RU2789855C2 - Session control system and methods - Google Patents

Abstract

FIELD: communication.

SUBSTANCE: method for control of a communication network session contains: reception by a session management function (hereinafter – SMF) of a trigger for release of a session of a packet data unit (hereinafter – PDU); sending by SMF to a user plane function (hereinafter – UPF) of a request for release of a session, which includes at least one of an identifier of use equipment (hereinafter – UE), an identifier of PDU session to be released, and ID of N4 session for UPF request for rejection of all remaining packets of PDU session and release of UE context in UPF, or all tunnel resources and contexts associated with N4 session in UPF; and reception by SMF of a response for release of a session from UPF.

EFFECT: improvement of control of a communication network session.

16 cl, 90 dwg, 3 tbl

Description

Cross-reference to related applications

This application relates to U.S. Provisional Application No. 62/444,251 entitled "Session Management System and Methods" filed January 9, 2017 to U.S. Provisional Application No. 62/448,239 entitled "Session Management System and Methods" , filed January 19, 2017, U.S. Provisional Application No. 62/455,412 entitled "Session Management System and Methods" filed February 6, 2017, U.S. Provisional Application No. 62/460,533 entitled "Session Management System and Methods U.S. Provisional Application No. 62/472,720 entitled "Session Management System and Methods" filed March 17, 2017; U.S. Provisional Application No. 62/492,045 entitled "Session Management System and Methods filed April 28, 2017, U.S. Provisional Application No. 62/503,117 entitled "Session Management System and Methods" filed May 8, 2017, and Provisional Patent Application U.S. Pat. No. 62/521,922 entitled "Session Management System and Methods" filed June 19, 2017, the contents of which are incorporated herein by reference, including all applications submitted. This patent application also takes precedence over US Patent Application No. 15/862,194, filed January 4, 2018, entitled "Session Management System and Methods", which is also incorporated herein in its entirety by reference.

The field of technology to which the invention belongs

The present invention relates to the field of network communications and, in particular, to a system and methods for managing a Packet Data Unit (PDU) session.

State of the art

When a user equipment (UE) initiates a new data session in a fifth generation (5G) network, the UE is connected (ie, attached or registered) to the network. The network session management function will oversee the execution of connection management tasks. In addition, when the UE is already connected to the network, the session management function can monitor changes in the network connection of the UE. The current session management procedures include overhead signaling and connection establishment time.

The information in this section "prior art" is provided as background information, which, in the opinion of the applicant, may be relevant to the present invention. It is implied that there is no need for any statement or interpretation that the prior information constitutes prior art as opposed to the present invention.

The essence of the invention

The object of the embodiments of the present invention is to provide a system and methods for managing a communication network session.

In accordance with embodiments of the present invention, a method for releasing a Packet Data Unit (PDU) session is provided. The method comprises determining a session PDU release trigger, sending a session release request message N4 to a user plane function (UPF), receiving a session release response message N4 from the UPF, sending a session PDU release command request N11 to an access and mobility management function (AMF), receiving N11 acknowledging the release of the session PDU from the AMF and sending N11 a message to the AMF.

According to embodiments of the present invention, a handover method is also provided, comprising receiving N2 a path switch request from a target radio access network (T-RAN), sending N11 a message to a session management function (SMF), receiving N11 an acknowledgment message from the SMF, and sending N2 a request acknowledgment path switching in T-RAN.

Brief description of the drawings

Additional features and advantages of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, in which:

1 illustrates in a block diagram a computing system that may be used to implement the devices and methods disclosed herein;

2A illustrates in a component diagram an example of a communications network architecture;

2B illustrates in a component diagram an example of a non-roaming next generation (NG) architecture (such as 5G mobile wireless networks) in a point-to-point reference point view;

2C is a block diagram illustrating a service-based representation of a 5G core network system architecture;

3 illustrates, in a message processing flow diagram, an example of methods for attaching and reattaching a UE to a data network;

4 illustrates in a component diagram an example of a "Session-IDLE" state model;

5 illustrates in a component diagram an example of a "Session-ACTIVE" state model;

6A illustrates in a state diagram an example of a session control state model in a UE;

6B illustrates in a state diagram an example of a session management state model in the SMF;

6C illustrates in a component diagram an example session control state model for a plurality of session PDUs;

7 illustrates in a message processing diagram an example of a session establishment procedure according to an embodiment of the present invention;

8 illustrates, in a message processing flow diagram, an example SMF-AMF of a procedure for subscribing to mobility information of a UE, according to an embodiment of a session establishment procedure;

9 illustrates, in a message processing flow diagram, an example SMF-UDM of a UE context update procedure according to an embodiment of a session establishment procedure;

10 illustrates, in a message processing flow diagram, an AMF-UDM example of a UE context update procedure according to an embodiment of a session establishment procedure;

Fig. 11 illustrates, in a message processing flow diagram, an SMF-PCF example of a session update procedure according to an embodiment of a session establishment procedure;

12 illustrates in a flowchart an example of a session establishment method according to a session establishment procedure;

13 illustrates in a message processing flowchart an example of a session change procedure according to an embodiment of the present invention;

14 illustrates in flowchart an example of a session change method according to a session change procedure;

Fig. 15 illustrates in a message processing flowchart an example of a session release procedure according to an embodiment of the present invention;

16 illustrates in flowchart an example of a session release method according to a session release procedure;

17 illustrates in flowchart another example of a session release method according to a session release procedure;

18 illustrates in a message processing flowchart an example of a session PDU connection state transition procedure according to an embodiment of the present invention;

19 illustrates in a flowchart an example of a method for performing a state transition according to a session PDU connection state transition procedure;

20 illustrates, in a message processing flowchart, an example of an RRC suspend procedure according to an embodiment of the present invention;

21 illustrates in a flowchart an example of a session state transition method according to an RRC suspend procedure;

22 illustrates in a flowchart another example of a session state transition method according to an RRC suspend procedure;

23 illustrates, in a message processing flowchart, an example of an RRC resume procedure according to an embodiment of the present invention;

24 illustrates in a flowchart an example of a session state transition method according to an RRC resume procedure;

25 illustrates in flowchart an example of a session state transition method according to an RRC resume procedure;

26 illustrates, in a message processing flowchart, an example of a session-IDLE individual PDU state transition procedure, in accordance with an embodiment of the present invention;

27 illustrates in a flowchart an example of a session state transition method according to a session-IDLE individual PDU state transition procedure;

28 illustrates in a flowchart another example of a session state transition method according to a session-IDLE individual PDU state transition procedure;

29 illustrates, in a message processing flowchart, another example of a "Session-ACTIVE" PDU state transition procedure, in accordance with an embodiment of the present invention;

30 illustrates in a message processing flowchart an example of a Session-ACTIVE PDU session state transition procedure, in accordance with an embodiment of the present invention;

31 illustrates in a flowchart an example of a method for performing a Session-ACTIVE state transition according to a Session-ACTIVE PDU state transition procedure;

32 illustrates in a message processing flowchart an example of a Session-ACTIVE PDU session state transition procedure according to an embodiment of the present invention;

33 illustrates, in a flowchart, an example of a session transition method according to a Session-ACTIVE PDU state transition procedure;

34 illustrates, in a component diagram, an example of a UE Status CN Update service procedure;

35 illustrates, in a component diagram, an example procedure of the session PDU change service;

36 illustrates, in a component diagram, an example of a Get UE Policies service procedure;

37 illustrates, in a component diagram, an example of a refresh UE context service procedure;

38 illustrates, in a component diagram, an example of a refresh UE context service procedure; And

39 illustrates in a message processing flowchart an example method of an embodiment of the present invention.

40 illustrates in a message processing flowchart an example method of an embodiment of the present invention.

41 illustrates in a message processing flowchart an example of a release procedure N2 and a session PDU according to an embodiment of the present invention.

42 illustrates, in a flowchart, an example of a method for releasing an N2 connection and deactivating session PDUs in accordance with a session PDU release and deactivation procedure N2.

43 illustrates in a flowchart another example of a session PDU deactivation method according to a session PDU deactivation procedure.

44 illustrates, in a message processing flowchart, another example of a session PDU deactivation procedure in accordance with an embodiment of the present invention.

FIG. 45 illustrates in a flowchart an example of a session PDU deactivation method according to the session PDU deactivation procedure of FIG.

FIG. 46 illustrates in a flowchart another example of a session PDU deactivation method according to the session PDU deactivation procedure of FIG. 44.

47 illustrates, in a message processing flowchart, another example of a Session-ACTIVE state transition procedure according to an embodiment of the present invention.

48 illustrates in flowchart an example of a session transition method according to the Session-ACTIVE state transition procedure of FIG. 47.

FIG. 49 illustrates in a flowchart another example of a session transition method according to the Session-ACTIVE state transition procedure of FIG. 47.

50 illustrates in a message processing flowchart an example of a service request procedure according to an embodiment of the present invention.

51 illustrates in a message processing flowchart an example of a service request procedure (5100) according to an embodiment of the present invention.

52A illustrates in a state diagram an example of a session management state model in a UE according to an embodiment of the present invention.

52B illustrates in a state diagram an example of a session management state model in an AMF and/or SMF in accordance with an embodiment of the present invention.

53 illustrates in a message processing flowchart an example of an inter-NG RAN handover procedure based on Xn without moving the UPF according to an embodiment of the present invention.

FIG. 54 illustrates in flowchart an example of a method for handover of a UE from a source RAN to a target RAN according to the inter-NG RAN handover procedure based on Xn of FIG. 53.

FIG. 55 illustrates in a flowchart another example of a method for handover of a UE from a source RAN to a target RAN according to the inter-NG RAN handover procedure based on Xn of FIG. 53.

56 illustrates in a message processing flowchart an example of an inter-NG RAN handover procedure based on Xn with user plane function movement, in accordance with an embodiment of the present invention.

57 illustrates in a message processing flowchart an example of an N3 reconnection procedure initiated by UL data according to an embodiment of the present invention.

58 illustrates in a message processing flowchart an example of an N3 reconnection procedure initiated by DL data according to an embodiment of the present invention.

59 illustrates in a message processing flowchart an example procedure N2 for releasing and deactivating a session PDU in accordance with embodiments of the present invention.

60 illustrates, in a message processing flowchart, another example of a procedure N2 for releasing and deactivating a session PDU, in accordance with embodiments of the present invention.

61 illustrates in a message processing flowchart an example of a session PDU release procedure initiated by a UE, PCF, or SMF, in accordance with embodiments of the present invention.

62 illustrates, in a message processing flowchart, another example of a session PDU release procedure initiated by a UE or an SMF, in accordance with embodiments of the present invention.

63 illustrates in a message processing flowchart an example of an inter-NG(R)AN handover procedure based on Xn without user plane function relocation and with session deactivation, in accordance with embodiments of the present invention.

64 illustrates in a message processing flowchart an example of a service request procedure initiated by a UE according to embodiments of the present invention.

65 illustrates in a message processing flowchart an example of a late path switching procedure initiated by DL data without UPF movement, in accordance with embodiments of the present invention.

66 illustrates in a message processing flowchart an example of a late path switching procedure triggered by UL data with UPF reselection, in accordance with embodiments of the present invention.

67 illustrates in a message processing flowchart an example of a late path switching procedure triggered by DL data with UPF reselection, in accordance with embodiments of the present invention.

68 illustrates in a message processing flowchart an example of a UPF reselection procedure in accordance with embodiments of the present invention.

69 illustrates in a message processing flowchart an example of a UE context release procedure in an AN according to embodiments of the present invention.

70 illustrates in a message processing flowchart an example procedure for a requested UE or CN to release a session PDU for non-roaming and local output roaming in accordance with embodiments of the present invention.

71 illustrates in a message processing flowchart an example procedure for a requested UE or CN to release a session PDU for home routed roaming in accordance with embodiments of the present invention.

72 illustrates in a message processing flowchart an example of a handover procedure between NG(R)ANs based on Xn without moving a user plane function in accordance with embodiments of the present invention.

73 illustrates in a message processing flowchart an example of an inter-NG(R)AN handover procedure based on Xn with user plane function movement according to embodiments of the present invention.

74 illustrates in a message processing flowchart an example of a service request procedure initiated by a UE according to embodiments of the present invention.

75 illustrates in a message processing flowchart an example of a service request procedure initiated by a UE in a "CM-CONNECTED" state according to embodiments of the present invention.

76 illustrates in a message processing flowchart an example of a network initiated service request procedure according to embodiments of the present invention.

77 illustrates in a message processing flowchart an example of a service request procedure initiated by a UE in a "CM-CONNECTED" state according to embodiments of the present invention.

78 illustrates in a message processing flowchart an example of an AMG node-to-node handover procedure between NG-RAN nodes without an Xn interface in accordance with embodiments of the present invention.

79 illustrates in a message processing flowchart an example of release procedure N2, which is also known as UE context release in AN procedure, in accordance with embodiments of the present invention.

80 is a message processing flowchart illustrating an example of a UE-requested or network-requested session PDU release for non-roaming and local output roaming in accordance with embodiments of the present invention.

81 is a message processing flowchart illustrating an exemplary procedure for releasing a UE context in an AN, in accordance with embodiments of the present invention.

82A and 82B are a message processing flowchart illustrating an example of a service request procedure initiated by a UE, in accordance with embodiments of the present invention.

83A and 83B are a message processing flowchart illustrating an example of a service request procedure initiated by a UE in a "CM-CONNECTED" state, in accordance with embodiments of the present invention.

It should be noted that throughout the accompanying drawings, the same features are identified by the same reference numerals.

Detailed description

Embodiments of the present invention provide session management procedures for a communication network.

As used herein, a "network" or "communications network" may serve various devices, including, but not limited to, wireless communication devices. Such a network may include a radio access part and a backhaul part. The network may further comprise various virtualized components. The main example of such a network is the 5G network, which is reconfigurable and capable of segmenting the network.

Network segmentation refers to the ability of a network, such as a 5G communication network available to wireless devices, to provide multiple logical network segments on demand, with each network segment operating as essentially a separate network for different market scenarios that require different requirements. The capabilities and operating parameters of each network segment can be adapted to the requirements of the service. The configuration of network segments can be based on software-defined networking, network function virtualization, and network orchestration.

One application of network segmentation is in the core network. Through the use of network segmentation, different service providers can have different core networks that operate on the same physical set of network and computing resources. This can also be used to build a virtual network dedicated to certain types of network traffic. It should be understood that this discussion is not intended to exclude the application of network segmentation to the radio access edge of a radio access network (RAN), which may use certain functionality to support multiple network segments or partition resources for different network segments. To provide performance guarantees, network segments can be isolated from each other so that one segment does not adversely affect other segments. Isolation is not limited to different types of services, but also allows an operator to deploy multiple instances of the same network section.

Network segmentation allows the formation of separate network segments, respectively directed to different network services. This allows you to isolate different types of traffic from each other by assigning a segment to each type of traffic. Each segment may have characteristics adapted to the needs of the traffic flow it carries. Such needs may include different packet processing requirements, different service requirements, and different Quality of Service (QoS) requirements. Different network segments, corresponding to different pooled resource allocations, may offer different services to different customers or groups of customers. Different services may be supported by different network segments (network segment can be thought of as a type of custom virtual network), where different network segments (i.e. different custom virtual networks) are essentially separated from each other from the client point, although they may share physical network resources. The pooled resources may be commercial off-the-shelf hardware components configured to be configured using virtualization approaches such as NFV to support various network functionality to support network segment operations.

The session management functionality of the network is responsible for establishing an Internet Protocol (IP) or non-IP traffic connection for a user equipment (UE) and managing the user plane for that connection. Network functions in the next generation (NG) control plane may have service-based interfaces for services that can be used by authorized network functions.

In FIG. 1 is a block diagram illustrating a computing system 100 that may be used to implement the devices and methods disclosed herein. Specific devices may use all of the components shown, or only a subset of the components, and levels of integration may vary from device to device. In addition, a device may contain multiple instances of a component, such as multiple processing units, processors, memories, transmitters, receivers, and so on. The computing system 100 includes a processing unit 102 . The processing unit 102 includes a central processing unit (CPU) 104, a memory 106, and may further include a mass storage device 108, a video adapter 110, and an I/O interface 112 connected to the bus 114.

Bus 114 may be one or more of any type of several bus architectures, including a memory bus or memory controller, a peripherals bus, or a video bus. CPU 104 may include any type of electronic data processor. Memory 106 may comprise any type of permanent system memory such as static random access memory (SRAM), dynamic random access memory (DRAM), synchronous DRAM memory (SDRAM), read only memory (ROM), or a combination thereof. The memory 106 may include ROM for use during booting and DRAM for storing programs and data for use during program execution.

Storage device 108 may include any type of temporary storage device configured to store data, programs, and other information and provide access to data, programs, and other information via bus 114. Storage device 108 may include, for example, one or more solid state drives, hard drives, discs, magnetic discs or optical discs.

The video adapter 110 and the input/output interface 112 provide interfaces for connecting external input and output devices to the processing unit 102 . As shown, examples of input and output devices include display 116 connected to video adapter 110 and mouse/keyboard/printer 118 connected to I/O interface 112, other devices may be connected to processor 102 and may use more or less number of interface cards. For example, a serial interface such as Universal Serial Bus (USB) (not shown) may be used to provide an interface to an external device.

The processing unit 102 may also include one or more network interfaces 120, which may include wired links, such as an Ethernet cable, and/or wireless links for accessing nodes or various networks. Network interfaces 120 allow processor 102 to communicate with remote units via networks. For example, network interfaces 120 may provide wireless communication through one or more transmitters/transmit antennas and one or more receivers/receiver antennas. The processing unit 102 may be connected to a local area network 122 or a wide area network for data processing and communication with remote devices such as other processing units, the Internet, or remote storage media.

2A illustrates in a component diagram an example of a communication network architecture 200. The communication network architecture 200 includes a user device (UE) 202, an access network (AN) 204, a core network (CN) 206, and a data communication network (DN) 208 . One example of an AN 204 is a radio access network (RAN). The term (R)AN is used in this description to mean that either AN and/or RAN can be used. UE 202 communicates with DN 208 via (R)AN 204 and CN 206. Packet Data Units (PDUs) messages between UE 202 and DN 208 are transmitted via (R)AN 204 and CN 206. DN 208 may be a public network operator, a private a data network such as a Data Processing Local Area Network (LADN), an intra-operator data network, or any other type of data network.

In the uplink (UL) direction of the user plane (UP), PDUs are transmitted from the UE 202 to the (R)AN 204 via the link. (R)AN 204 forwards UP PDUs to CN 206, which then forwards UP PDUs to DN 208. In the downlink (DL) direction, DL PDUs are transmitted from DN 208 to CN 206, which then forwards DL PDUs to (R)AN 204 , which then forwards the DL PDUs to the UE 202. The CP functionality on the CN 206 configures the UP functionality on the CN 206 to provide the traffic processing functionality for the session. One or more UP functions per session can be enabled and configured by the CP functionality for a given UP scenario.

The connections between the components of the communication network architecture 200 may be suitable for any communication channel. For next generation (NG) architectures, the connection between the (R)AN 204 and the CP CN 206 may be via the NG2 interface. The connection between the (R)AN 204 and UP CN 206 may be via the NG3 interface. The connection between UP CN 206 and DN 208 can be made via the NG6 interface.

In FIG. 2B illustrates in a component diagram an example of a non-roaming 210 NG architecture (such as 5G mobile wireless networks) in a point-to-point reference point view. Non-roaming NG architecture 210 contains UE 202, (R)AN 204, CN 206, application function (AF) 250 that is outside CN 206, and DN 208. CN 206 contains UP function (UPF) module 212 and CP function. The CP functions include an authentication server function (AUSF) 214, a unified data management (UDM) function 216, an access and mobility management function (AMF) 218, a session management function (SMF) 220, and a policy control function (PCF) 222 . AMF 218 manages signaling termination of NG1 and NG2 interfaces, forwarding of signaling messages from UE 202 and (R)AN 204 to SMF 220, and management of mobility and security procedures for UE 202. SMF manages UP connection establishment between UE 202 and DN 208. PCF 222 provides policies to various network functions for UE session processing such as QoS, mobility management, session management, and billing policies. The UDM 216 provides network and user information storage management and security measures to protect data. AUSF 214 provides security functions such as authentication of users and user requests, and provision of security keys to encrypt data transmitted over the interfaces. AF 224 may be any application server outside the 3GPP network that provides control information between external applications and CN 206. For example, an IMS server may be AF 224. UPF 212 provides user plane functions such as mapping IP packets to QoS flows, packet forwarding , measuring traffic and preparing and sending reports. (R) AN 204 provides an air interface connection for UE 202 and forwards packets between UE 202 and CN UPF 212.

The components of the CN 206 in the non-roaming NG architecture 210 may be implemented as software modules on one or more servers. Fig. 2B illustrates one example of possible interfaces between some of the components. Table 1 shows the communication interfaces used by some of the components in FIG. 2b.

• Table 1. Interfaces used by some components of the non-roaming NG architecture

• Component • Interface • Component •UE 202 • NG1 •AMF 218 • (R)AN 204 • NG2 •AMF 218 • (R)AN 204 • NG3 •UPF 212 •UPF 212 • NG4 • SMF 220 • PCF 222 • NG5 • AF 224 •UPF 212 • NG6 • DN 208 • SMF 220 • NG7 • PCF 220 •AMF 218 • NG8 • UDM 216 • UDM 216 • NG10 • SMF 220 •AMF 218 • NG11 • SMF 220 • AUSF 214 • NG12 •AMF 218 • AUSF 214 • NG13 • UDM 216 •AMF 218 • NG14 •AMF 218 •AMF 218 • NG15 • PCF 222

In FIG. 2C illustrate a service-based architecture 226 for 5G core network or next generation (5GCN/NGCN/NCN). This illustration depicts logical connections between nodes and functions, and the connections shown in it should not be interpreted as direct physical connections. The UE 202 forms a radio access network connection with an ((R)AN) access network (radio) node 228 (which may be, for example, gNodeB (gNB)) that is connected to a CN of a user plane (UP) function (UPF) 212, such as gateway UP, through the network interface providing a specific interface, such as the N3 interface. The UPF 212 provides a logical connection to the data network (DN) 208 via a network interface such as the N6 interface. The radio access network connection between UE 202 and (R)AN node 226 may be referred to as a radio bearer (DRB).

DN 208 may be a data network used to provide an operator service, or may be outside the scope of a 3rd Generation Partnership Project (3GPP) standardization such as the Internet, a network used to provide a third party service. and in some embodiments, DN 208 may represent an edge computing network or resource, such as a mobile edge computing (MEC) network.

The UE 202 also connects to the access control and mobility function (AMF) 218 via a logical connection N1 (although the physical connection path is not direct). AMF 218 provides authentication and authorization of access requests, as well as a mobility management function. AMF 218 may perform other roles and functions as defined by 3GPP Technical Specification (TS) (TS) 23.501. From a service point of view, AMF 218 may communicate with other core network control plane functions via a service-based interface referred to as Namf.

The session management function (SMF) 220 is a network function that is responsible for distributing and managing the IP addresses that are assigned to the ED, as well as selecting the UPF 212 (or a specific UPF 212 instance) for traffic associated with a particular UE 202 session. It is understood that network 226 will typically have a plurality of SMFs 220, each of which may be associated with a respective group of UEs 202, (R)AN nodes 2282, or UPFs 212. SMF 220 may communicate with other core network functions, from a service value point of view, through a service-based interface designated as Nsmf. The SMF 220 can also connect to the UPF 212 via a logical interface such as the N4 network interface.

Authentication Server Function (AUSF) 214 provides authentication services to other network functions via a service-based Nausf interface.

A network exposure function (NEF) 230 may be deployed on a network to allow servers, functions, and other entities, such as those outside a trusted domain, to access services and capabilities on the network. In one such example, NEF 230 may act as a proxy between an application server outside the network shown and network functions such as policy control function (PCF) 222, SMF 220, UDM 216, and AMF 218, so the external application server may provide information that can be useful when setting parameters associated with a data session. The NEF 230 can communicate with other network functions through the Nnef service-based network interface. NEF 230 may also have an interface for non-3GPP functions.

Network Storage Function (NRF) 232 provides network service discovery functionality. NRF 232 may be specific to the public land mobile network (PLMN) or the network operator with which it is associated. Service discovery functionality may allow network functions and UEs connected to the network to determine where and how to access existing network functions, and may present a service-based Nnrf interface.

The PCF 222 communicates with other network functions via a service-based Npcf interface and may be used to provide policies and rules for other network functions, including those in the control plane. Enforcing and enforcing policies and rules is not necessarily the responsibility of the PCF 222, and is instead generally the responsibility of the functions to which the PCF 222 communicates the policy. In one such example, PCF 222 may pass a policy associated with session management to SMF 220. This may be used to provide a unified policy framework with which to control network behavior.

The unified data management (UDM) function 216 may represent a service-based Nudm interface for communication with other network functions and may provide storage facilities for other network functions. A unified data store can provide a consolidated view of network information that can be used to ensure that the most relevant information is available for various network functions from a single resource. This can make it easier to implement other network functions because they don't have to determine where a certain type of data is stored on the network. UDM 216 may use an interface, such as Nudr, to connect to a user data store (UDR) 234 . PCF 222 may be associated with UDM 216 as it may be associated with requesting and providing subscription policy information in UDR 234, but it should be understood that typically PCF 222 and UDM 216 are independent functions.

PCF 222 may have a direct interface to UDR 234 or may use a Nudr interface to connect to UDR 234. UDM 216 may receive requests to retrieve content stored in UDR 234 or requests to store content in UDR 234. UDM 216 is typically responsible for the functionality, such as credential processing, location management, and subscription management. The UDR 234 may also support any or all of: validated credential processing, user identification processing, access authorization, enrollment/mobility management, subscription management, and short message service (SMS) management. The UDR 234 is typically responsible for storing the data provided by the UDM 216. The stored data is typically associated with policy profile information (which may be provided by the PCF 222) that controls access rights to the stored data. In some embodiments, UDR 234 may store policy data as well as user subscription data, which may include any or all subscription identifiers, security credentials, access and mobility associated subscription data, and session-related data.

An application function (AF) 224 represents the functionality of a non-data plane (also called non-user plane) application deployed in a network operator domain and in a 3GPP compliant network. The AF 224 interacts with other core network functions via a service-based Naf interface and can access network capability information as well as provide application information for use in decision making such as traffic routing. AF 224 may also interact with functions such as PCF 222 to provide specific application input for policy and policy decisions. It should be understood that in many situations the AF 224 does not provide network services to other NFs and is instead often viewed as a consumer or user of services provided by other NFs. An application outside the 3GPP network can perform many of the same functions as AF 224 through the use of NEF 230.

UE 202 establishes communication with network functions that are in the user plane 236 (UP) and the control plane 238 (CP). UPF 212 is part of CN UP 236 (DN 208 is outside 5GCN). (R) AN node 228 may be considered part of the user plane, but because it is not strictly part of the CN, it is not considered part of the CN UP 236 or UPF 212. AMF 218, SMF 220, AUSF 214, NEF 230, NRF 232, PCF 222, and UDM 216 are functions that reside in CN CP 238 and are often referred to as control plane functions. AF 224 may communicate with other functions in CN CP 238 (either directly or indirectly through NEF 230), but is not normally considered part of CN CP 238.

Those skilled in the art will appreciate that there may be multiple UPs connected in series between the (R)AN node 228 and DN 208, and multiple data sessions for different DNs may be accommodated by using multiple UPFs in parallel.

3 illustrates in a message processing flowchart an example of methods (300) for joining (305) and rejoining (375) a UE 202 to a data network 208. The join method (305) comprises the UE 204 sending an initial join request to the AN 204 (310) including the UE capability and possibly the requested service and Network Segment Selection Assistance Information (NSSAI). The AN 204 forwards the join request to the AMF 218. The AMF 218 determines which segment(s) the UE 204 has selected by accessing the subscriber store, and then authenticates the UE 204 (320) to check if the UE 204 is allowed to access the network. AMF 218 then checks the UE's mobility policy (330) to see if the UE can access the network at that location. The AMF 218 selects the appropriate network segment SMF 220 based on the information received from the UE 204 in the join request and the profile information in the subscriber's store. The AMF 218 further interacts with the AUSF 214 to perform a segment authentication/authorization procedure by verifying the identity of the UE with the subscriber's store. The procedure determines if the UE 204 is authorized to access the given segment. Possibly, UP connection setup (360) may be performed for a default segment or a segment of a specific UE type. AMF 218 may then send a join response to UE 202 via AN 204. The join response includes session control, network segment selection assistance information (SM-NSSAI), UE temporary identifier (UE temporary identifier), and MM parameters. When UE 204 receives the SM-NSSAI, UE Temporary ID, and Mobility Management (MM) parameters, UE 204 may use this information to help select a network segment (eg, when the UE disconnects from the network and then rejoins the network again).

The reattach method (375) comprises a UE 202 sending a join request (380) to the AN 204. The join request includes an SM-NSSAI, a temporary UE identifier, and MM parameters. The AN 204 sends the join request to the AMF 218. An authorization step (350) for a particular segment may be performed, and possibly the UP connection establishment step (360) described above. AMF 218 may then send a join response (390) to UE 202 via AN 204. The join response includes a (possibly updated) SM-NSSAI, temporary UE ID, and MM parameters. Once UE 202 is attached (or reattached) to data network 208, the UE may initiate a Packet Data Unit (PDU) session with data network 208.

The session control states describe the UP connectivity for a session PDU between UE 202 and SMF 220. For an established session PDU, there can be at least two session control states for a session PDU: an active state (eg, "Session-ACTIVE") and an idle state. (for example, "Session-IDLE"). In this description, "Session-ACTIVE" may be used to indicate an active state and "Session-IDLE" is used to indicate an idle state. Since the session PDU state refers to the data transfer activities (UL and DL) of the user, the session state may alternatively be referred to as the session connection state.

The session control state may be designed for each session PDU, respectively. The session control state may be maintained at UE 202 and SMF 220. The AN 204 and the UP functions may not be aware of the session control state. However, the AN 204 and the UP functions may maintain the context of an established session PDU.

When the UE 202 is roaming (in the home routed roaming model), the session PDU may be served by two SMFs 220 in chain: one for the Visited Public Land Mobile Network (VPLMN) and one for the Home Public Land Mobile Network (HPLMN). The session control state may be updated in the SMF 220 in the VPLMN, while the SMF 220 in the HPLMN may consider the session PDU to be "Session-ACTIVE".

When a UE session PDU has no UL or DL activity for a certain period, the state of that session may be changed to "Session-IDLE". The UE may resume the session PDU(s) after a certain period of time by sending an Access Layer (AS) message to the AN 204 to activate the Data Radio Bearer (DRB). Alternatively, the UE may resume the session PDU(s) after a certain period of time has elapsed by sending a non-access layer (NAS) message to the SMF to notify the session activation request. For example, a user is browsing a website. The user may not have any data transfer when viewing downloaded pages or downloaded videos. The UE may download new data for the same session again after reading or viewing the downloaded content. In this example, if a period of time elapses while the user is browsing the downloaded content, the session PDU may be changed to "Session-IDLE". When the user starts downloading more data, the session PDU is then changed to "Session-ACTIVE".

In the combined join request and session PDU procedure, the UE may send a request for a new session in a join request message. However, if the UE has no transmission of UL or DL packets after a certain period of time, the session state may be changed from "Session-ACTIVE" to "Session-IDLE". Thus, by allowing a session to have an active state and an idle state, the UE can establish and maintain a new session for "future use" (or near future use) even if the UE has not transmitted UL or DL packets for a period of time after the new session is established. Without the "Session-IDLE" state, the session may be released prematurely.

The session state attribute may allow the CN 206 to efficiently handle session PDUs of various applications. UE 202 may initiate a session connection state transition at CN 206 by sending an AS message to AN 204 to change the DRB state (between active or suspended state); The AN 204 may then inform SMF 220 of the UE's request to activate or deactivate the session PDU at CN 206. Alternatively, UE 202 may initiate a session connection state transition at CN 206 by sending a NAS message to CN 206; the CN then activates the session control procedures at the CN and informs the AN 204 of the radio resource assignment for the session PDU. The session connection state attribute may also enable fast reconnection at the CN 206 when the session is resumed, may reduce signaling at the CP when the session is resumed or Radio Resource Control (RRC), may use network function resource utilization when session PDUs are idle for a long period, and may avoid RRC signaling regarding session state changes at CN 206. In one embodiment, UE 202 is unaware of session state at CN 206. In another embodiment, UE 202 is aware of session connection state.

FIG. 4 illustrates in a state model diagram an example of a "Session-IDLE" state model 400 . The "Session-IDLE" state model 400 shows how the "Session-IDLE" state can be represented in CP (as session state) and UP (as session context) for UE 202, AN 204, SF 220, and UPF 212. When a PDU session is in the "Session-IDLE" state, there may be no UP connection dedicated to the session PDU existing between the UE 202 and the UPF 212 terminating NG3. UE 202 may maintain a session context without RAN activated resources corresponding to the session PDU. In this example, the AN does not maintain any radio resource context corresponding to the session PDU. If the session PDU is served by only one UPF 212 (ie, if only UPF A is present for UPF 212 in FIG. 4), then the session context can be maintained in UPF A without information related to AN 204 NG3. If the session PDU is served by two UPFs 212 in chain (that is, if only UPF A and UPF B are used for UPF 212 in FIG. 4), then the session context can be maintained in both UPF A and UPF B. NG3 terminating the UPF , may not support information associated with AN 204. Both UPF A and UPF B may support information associated with an NG9 tunnel. If the session PDU is a multicast session PDU (i.e., UPF A, UPF B, and UPF C are used, as shown in FIG. 4), then the session context at the UPF branch point (i.e., UPF A) is not supported by AN 204 related information. . In this multicast session PDU, stub point UPF A may support NG9 tunnel-specific information towards both UPF B and UPF C. UPF B and UPF C may support NG9 tunnel-specific information towards UPF A branches.

UE 202 and SMF 220 may be in the "Session-IDLE" state when a data connection (i.e., NG3) dedicated to a session PDU is not established between UE 202 and UPF 212. NAS message (eg, service request) , including a given session PDU identifier (ID), may initiate a transition from "Session-IDLE" to "Session-ACTIVE". When the session PDU is in the "Session-IDLE" state, the session context at UE 202 and SMF 220 may be out of sync (i.e., UE 202 and the network may have different sets of QoS flows enabled (e.g., for guaranteed bit rate (GBR) QoS flows )). During the transition from the "Session-IDLE" state to the "Session-ACTIVE" state, the UE 202 may include a QoS flow state that indicates each QoS flow state (i.e., enabled or disabled) of the session PDU in the NAS message (e.g., service request), with the set of activated QoS flows synchronized between UE 202 and SMF 220.

In FIG. 5 illustrates in a component diagram an example of a "Session-ACTIVE" state model 500. The Session-ACTIVE state model 500 shows how the Session-ACTIVE state can be represented in CP (as session state) and UP (as session context) for UE 202, AN 204, SF 220, and UPF 212. A session PDU can be in the "Session-ACTIVE" state when a data connection (ie, NG3) dedicated to a given session PDU is established between the UE 202 and the UPF 214. In the "Session-ACTIVE" state, the UL/DL data belonging to the session PDU may be directly sent between UE 202 and the network. UE 202 may maintain a session context with RAN activated resources corresponding to the session PDU. The AN 204 may maintain the session context and reserve a RAN resource (for the GBR QoS flow, if present) corresponding to the session PDU. Only one UPF is served in a session PDU (ie, only UPF A), a session context may be maintained in UPF A with information associated with AN 204 NG3. If the session PDU is served by two UPFs in the chain (ie, only UPF A and UPF B), the session context may be maintained in both UPF A and UPF B. The final NF3 UPF may support AN 204 associated NG3 information. Both UPF A and UPF B can support information associated with an NG9 tunnel. If the session PDU is a multicast session PDU (ie, UPF A, UPF B, and UPF C), the session context at the UPF stub point (ie, UPF A) may maintain information associated with AN 204. The stub point UPF A may support NG9 tunnel related information to UPF A and UPF B. UPF A and UPF B can support NG9 tunnel related information to UPF A.

The AN 204 may be configured with a session sleep timer via SMF 220 when a session PDU is established or activated. If no UL/DL data is detected in the session PDU at the AN 204 during the idle session timer, then the AN 204 may initiate a session connection state transition procedure. The session connection state at both UE 202 and SMF 220 may enter "Session-IDLE" for a given session PDU.

The AN 202 and SMF 220 may also initiate a session PDU deactivation procedure for certain reasons. For example, O&M intervention, undefined failure, etc. When the session PDU is in the "Session-ACTIVE" state, during handover procedures, the AN 204 may send the session PDU identifier to the AMF 218 in a "required handover" message. According to the session PDU ID, the AMF 218 may notify the corresponding SMF 220 that the handover procedure has been performed.

The following session control (SM) parameters are used in the present invention: "session state", "activate-session-when-RRC-resume", "session-activity-timeout", "SM-action-for-idle" and " support-UE-context-for-all".

The session state parameter may be used in the context of the UE session PDU at AN 204, SMF 220, UPF 212, UDM 216, and PCF 222. The session state parameter may have two values: "Session-ACTIVE" and "Session-IDLE".

The "activate-session-when-RRC-resused" parameter may be used to indicate whether the session PDU is in the "Session-ACTIVE" state when the RRC is resumed. This parameter can have two values: "Yes" and "No". The parameter may be configured by PCF 222. PCF 222 may send this parameter to SMF 220. SMF 220 may then send this parameter to AN 204 and/or UE 202 during the session establishment procedure.

The session-activity-timeout parameter may be a timer parameter in the AN 204 configured by the PCF 222 for individual session PDUs. The parameter may be used to monitor activities in the UL and DL session PDUs. If the UE 202 has no UL or DL packets longer than the session-activity-timeout parameter, then the AN 204 may inform the SMF 220. The SMF 220 may then either release that session PDU or change the session state from the "Session ACTIVE" to "Session-IDLE", depending on the session management (SM) policy configured by PCF 222.

The SM-action-to-inaction parameter is an SM policy parameter configured by the PCF 222. The PCF 222 may send this parameter to the SMF 220 during the session establishment procedure. The SM-action-to-idle parameter can have two values: "keep-session-idle" and "release-session-idle". If the value is set to "keep-session-idle", then SMF 220 may change the state of the session PDU from "Session-ACTIVE" to "Session-IDLE". If the value is set to "release-idle-session", then the SMF 220 may release the idle session PDU.

The "keep-UE-context-for-idle-sessions" parameter may be in the UE context of SMF 220 and UPF 222, as configured by PCF 222. This parameter may be used to indicate whether the UE 202 context may be supported in SMF 220 and UPF 222, when all session PDUs of the same UE 202 that are served by SMF 220 and UPF 222 are in the "Session-IDLE" state. The "keep-UE-context-for-idle-sessions" parameter can have two values: "keep" and "may-be-released". If the "keep-UE-context-for-idle-sessions" parameter is set to "keep", then SMF 220 and UPF 222 can save the UE context regardless of session state. If "keep-UE-context-for-idle-sessions" is set to "may-be-released", then at least one of the following may apply:

• UPF 212 and SMF 220 may store the full UE context if their UE context

has at least one active session. However, some information in the context of the UE may be released, such as NG3 connection information including the NG3 tunnel endpoint identifier and the AN 204 IP address.

• UPF 212 and SMF 220 may or may not store the UE context if all

the sessions it serves are in an idle state.

• when UPF 212 releases the context of UE 202 having all idle sessions,

UPF 212 may send its full UE context to SMF 220. Additionally, UPF 220 can send UE context charging information to PCF 222.

In FIG. 6A illustrates in a state diagram an example session control state model 600A in UE 202. Session control state model 600A shows a "Session-IDLE" state 610 and a "Session-ACTIVE" state 620. An active session (i.e., a session that is in the "Session-ACTIVE" state 620) may be transitioned to the "Session-IDLE" state 610 upon a request from the UE 202 or a request from the AN 204. Such requests may include a reconfiguration RRC connection to deactivate RAN resources for the session PDU and release the RRC connection. An idle session (that is, a session that is in the "Session-IDLE" state 610) may be transitioned to the "Session-ACTIVE" state 620 following a UE 202 request (Mobile Initiated Data (MO)) or a UPF 212 request (mobile completed (MT) data). Such requests may include reconfiguring the RRC connection to activate RAN resources for the session PDU.

In FIG. 6B illustrate in a state diagram an example session control state model 600B in SMF 220. Session control state transition model 600B shows a "Session-IDLE" state 610 and a "Session-ACTIVE" state 620. An active session (i.e., a session that is in the "Session-ACTIVE" state 610) may be transitioned to the "Session-IDLE" state 620 upon a request from the UE 202 or a request from the AN 204. Such requests may include a request session deactivation for session PDUs. An idle session (ie, a session that is in the "Session-IDLE" state 620) may be transitioned to the "Session-ACTIVE" state 610 after a UE 202 request (MO data) or a UPF 212 request (MT data). Such requests may include reconfiguring the RRC connection to activate RAN resources for the session PDU.

In FIG. 6C illustrate in a component diagram an example session control state model 600C for a plurality of session PDUs. UE 202 may have multiple session PDUs established using multiple SMFs 220 and UPFs 212. The NextGen system maintains an independent session connection state for each session PDU (e.g., session A is in the "Session-IDLE" state, while session B and session C is in "Session-ACTIVE" session A and session B are served by SMF A, while session C is served by SMF B). When multiple session PDUs are activated for UE 202, the AN 204 may be configured with separate idle session timers by SMF(s) 220 for each session PDU during the session activation procedure. When UE 202 is in the CN-IDLE state, the session connection state of each session PDU may be "Session-IDLE". When UE 202 requests to enter the CN-CONNECTED state from the CN-IDLE state (eg, service request), UE 202 may also indicate the session PDU(s) to be activated. The session connection state for the requested session PDU(s) may be changed to "Session-ACTIVE" at UE 202 and SMF 220 while other session PDUs (if any) may remain at "Session-IDLE". Regardless of whether UE 202 has an activated session PDU, the NextGen system may support activation of additional session PDUs.

When the session is in the "Session-IDLE" state 610, the RRC may be in any state (eg, RRC-CONNECTED, RRC-IDLE, RRC-INACTIVE). If all session PDUs are in the "Session-IDLE" state, then the RRC may be in any state, the mobility state is MM-registered, and the CN state is either CN-IDLE or CN-CONNECTED. DRB may be suspended. Thus, there is no AS signaling for idle sessions. UE 202, AN 204, UPF 212, SMF 220, UDM 216, and PCF (222) may store an appropriate UE context including tunnel information for fast connection resumption. However, the NG3 tunnel information may not be updated in case of UE mobility or UPF 212 movement. Tunnel maintenance procedures may not be performed. In addition, the NG3 idle session tunnel can be removed from the routing tables of AN 204 and UPF 212. The tunnel information will be updated when the session changes its state from "Session-IDLE" to "Session-ACTIVE". In the context of UE AN 204, UPF 212, SMF 220, UDM 216, and PCF 222, the session state parameter may be labeled "Session-IDLE". NAS signaling is not required for idle sessions. In UPF 212 for idle sessions, TFTs may not be available in the UPF 212 packet classification function. Resources used for session data rate monitoring and billing (AMBR/MBR/GBR) may be released.

When the session is in the "Session-ACTIVE" state 620 and the RRC is in the RRC-CONNECTED state, DRB/AS/NAS signaling is set. The mobility state is MM-registered and the CN state is CN-CONNECTED. Network functions serving PDU sessions, including UE 202, AN 204, UPF 212, AMF 218, SMF 220, UDM 216, and PCF 222, have corresponding UE context information. In UE contexts AN 204, UPF 212, SMF 220, UDM 216, and PCF 222, the session state parameter is labeled "Session-ACTIVE". In UPF 212, a traffic flow pattern (TFT) is available in the packet classification function of UPF 212. TFT is used to classify packets into Quality of Service (QoS) flows. Therefore, the more TFTs used, the higher the search complexity in UPF 212. Thus, only TFTs of active sessions are searched for incoming packets in UPF 212. In AN 204 and UPF 212, resources are used for monitoring session data rate PDUs (cumulative maximum data rate (AMBR)/Maximum Transfer Rate (MBR)/Guaranteed Transfer Rate (GBR)) session and billing.

SMF 220 may change the session PDU state from "Session-ACTIVE" to "Session-IDLE" based on requests from UE 202 and AN 204 or based on its own decision. UE 202 and UPF 212 may inform SMF 220 of the presence of UE data so that SMF 220 may change the session state from "Session-IDLE" to "Session-ACTIVE". You can change the state of individual sessions or a group of sessions. The SMF 220 informs the UPF 212 that the UPF 212 should either retain or optionally delete the UE context, depending on the SM policy for that session PDU configured by the PCF 222.

When RRC UE 202 is in RRC-CONNECTED state and AN 204 changes RRC to RRC-IDLE or RRC-INACTIVE CONNECTED mode, the state of all UE 202 session PDUs may be set to the "Session-IDLE" state.

When the RRC connection is resumed, the CN state changes from CN-IDLE to CN-CONNECTED. For MO transmission, UE 202 may send an AS request to AN 204 to re-establish an RRC connection. This request may include DRB identifiers (identifiers) to be renewed. Alternatively, UE 202 may send a NAS request to SMF 220 to indicate which session should be resumed. It is possible to resume SM for some specific session PDUs. For MT handover, UPF 212 may send a UE Context Update Request to SMF 220. SMF 220 interacts with AMF 218 to page UE 202 to activate an RRC connection.

To support individual (de) session activation, UE 202 and AN 204 may initiate a DRBs suspend or resume procedure. If the DRB is suspended, the session state at CN 206 may be changed to "Session-IDLE". If the DRB is resumed, then the session state at CN 206 may be changed to "Session-ACTIVE".

The following describes the session management procedures for session establishment, session release, session change, RRC state transition, and session state transition.

In FIG. 7 illustrates in a message processing flowchart an example of a session establishment procedure (700) in accordance with an embodiment of the present invention. The steps in the session establishment procedure (700) may be performed by multiple non-roaming architecture 210 components to establish a session between UE 202 and DN 208. PCF 222 may have an SM policy that includes network segment related information, specific preferred logical ULs, and DLs. paths between AN 204 and UPF 212.

The method (700) comprises the UE sending a new NAS session request message (705) that includes the SM-NSSAI, the UE temporary ID and the UE generated session ID, service type, and Domain Name Network (DNN) to the AMF 218 via AN204. It should be noted that when a session PDU is generated along with a UE initial attach or reattach procedure for some specific network segments, the UE may provide a UE generated session ID along with the initial attach or reattach request. The AMF 218 uses the SM-NSSAI to select the SMF 220 and forward the session request message to the selected SMF 220 (710) along with the IP address of the serving AN. The AMF 218 may store the identity of the selected SMF 220. When the SMF 220 receives a request from the AMF 218, the SMF 220 may store the identity of the AMF 218 that is serving the UE 202. The SMF 220 may access the user's subscription information in the UDM 216 to authorize (715) the service (ie, SMF-UDM service authorization messaging). If the service is not authorized, then SMF 220 may send an appropriate session formation response message (760) sent to UE 202 via AMF 218. The session establishment response may include a session failure code.

If the service is authorized (715), then UP connections can be made (360) for a default segment or a segment of a specific UE type. Establishing UP connections (360) may include an SMF 220 receiving policies from the PCF 222 (720) to the UE, including SM, QoS, and charging policies (i.e., extracting SMF-PCF (SM, QoS, charging) UE policies, message exchange). SMF 220 may also allocate IP address(es) to UE 202 if the session PDU is an IP based session. The SM policy may include at least the following information: preferred UPF(s) 212 to support mobile edge computing (MEC) applications; parameter "timeout-session-activity", "support-UE-context-for-idle-sessions", "SM-action-for-idle-sessions"

Possibly, the SMF 220 may subscribe to the AMF 218 for UE mobility information (725) if session management optimization based on the mobility pattern is to be performed and if the SMF has not yet subscribed to the AMF 218 for the information. It should be noted that the SMF-AMF UE mobility information subscription messaging (725) may be an independent procedure that may take place at any time before, after, or during session establishment. In this example, the UE mobility information subscription SMF-AMF is shown in the session establishment procedure.

The SMF 220 may then send a resource AN setup request message (730) to the serving AN 204 via the AMF 218. The request may include a temporary UE ID, a session ID, a QoS profile, and a selected IP address of the UPF 212. The request may also include a "session-timeout-activity-timeout" and "activate-session-when-RRC-resumed" parameter .

Possibly, if the session ID provided by UE 202 is contained in the join request, the AN 204 may perform admission control on the requested session PDU in accordance with the QoS profile. If the session PDU is approved, the AN 204 may set up (ie, set up) the DRB (735) according to the QoS profile. It should be noted that for some services, although the UE may not request a new session during the join procedure, the CN 206 may still establish an UP path even if no DRB is established between the UE 202 and AN204.

The AN 204 may then send an AN resource setup response message (740) to the SMF 220 via the AMF 218. The AN 204 may store all UE-specific information in a UE-specific context profile including the session state parameter. Next, the SMF 220 may select the UPF 212 based on the preferred UPF policy, if available, and the current traffic load of the UPF 212. The SMF 220 may send a UPF session request message (745) to the selected UPF 212, which may include at least , UE temporary ID, session ID, UE 202 IP address(es), QoS and charging policies, DNN, and the "keep-UE-context-for-idle-sessions-to-hold-context" parameter. UPF 212 may store all UE-related information in a UE-specific context, which may include UE temporary ID, session ID, AN 204, UE 202 IP address(es), QoS and charging policies, and additional information. It should be noted that the session identifier may be omitted for some types of UEs, such as Internet of Things (IoT) devices, which access only one segment and only one session PDU per network segment.

The UPF 212 may then send a UPF session setup response message (750) to the SMF 220. The SMF 220 may store all UE related information in the UE Context Profile SM including the session state parameter. SMF 220 may then send a session formation response message (755) to AMF 218, which may include a temporary UE ID and a session ID. AMF 218 may initiate mobility management procedures. The SMF 220 may then send the NAS a session establishment response message (760) to the UE 202 via the AMF 218. If the session request is received, the session establishment response may include the session ID, assigned IP address(es), possible QoS profile, and service continuity mode and session (SSC). The SM may store UE context information including SM policy, QoS and charging policies, assigned IP address(es), AMF ID, AN ID, UPF ID, NG3 tunnel information, and other parameters. The two steps 755 and 760 may be combined. For example, SMF 220 may send a single message containing two parts, one for AMF 218 and one for UE 202. After receiving the combined session formation response message, AMF 218 may extract information for itself and forward the UE part to UE 202. As noted above, if the session request is rejected, the session formation response may include an error code. This error code could be "unauthorized service request", "network resource outage", "not enough credit to pay" or another error code. It should be noted that if UE 202 requests a new session in an initial attach and reattach request, step (760) may be skipped. In this case, in the initial attach and reattach procedures, AMF 218 may send an attach response message that includes session control information. The SM information may include a session ID and a QoS profile.

Possibly, SMF 220 may send UE session management information (i.e., via SMF-UE context update procedure (765)) to UDM 216. Also, AMF 218 may send information associated with UE mobility management (i.e., via procedure ( 770) update the AMF-UDM UE context to UDM 216. It is possible that SMF 220 and PCF 222 may perform an SMF-PCF session update procedure (775) where the actual session PDUs may be sent from SMF 220 to PCF 222. It should be noted that The AN 204 and UPF 212 may establish a tunnel if that tunnel does not already exist.

In FIG. 8 illustrate in a message processing flowchart an example of a procedure (725) for subscribing to SMF-AMF UE mobility information in accordance with an embodiment of a session establishment procedure (700). SMF 220 may send AMF 218 (or AMF 218 may receive from SMF 220) an SMF-AMF UE mobility information request message (826). Message (826) may include one or more identifiers to identify the UE 202 (such as UE temporary ID, International Mobile Subscriber Identity (IMSI), GUTI), mobility time window, and subscription type. The mobility time window indicates the time interval of the requested UE mobility information. The subscription type indicates whether the subscription is a one-time search for information or can use periodic information updates. The SMF 220 may then receive from the AMF 218 (or the AMF 218 may send to the SMF 220) an SMF-AMF UE mobility information update message (828). The message may include identifiers for a set of ANs 204 that can potentially serve the UE in the specified mobility time window. AMF 218 may update (828) the mobility information upon receipt of the request (826) and, if the request (826) indicates a periodic update, when the requested mobility information changes. AMF 218 may determine the service of the AN 204 set according to the mobility pattern of the UE 202. Other steps may be added to the procedure (725).

FIG. 9 illustrates in a message processing flowchart an example of an SMF-UDM UE context update procedure (765) according to an embodiment of a session establishment procedure (700). SMF 220 may send to UDM 216 (or UDM 216 may receive from SMF 220) an SMF-UDM UE Context Update Request message (966). Message (966) may include identifiers to identify the UE 202 (such as a temporary identifier, IMSI, GUTI) and a UE context or new UE context parameter values that have changed. SMF 220 may then receive from UDM 216 (or UDM 216 may send SMF 220) an SFM-UDM Context Update Response message (968) to confirm that the UE context has been updated at UDM 216. Other steps may be added to procedure (765).

In FIG. 10 illustrate in a message processing flowchart an example of an AMF-UDM UE context update procedure (770) according to an embodiment of a session establishment procedure (700). The AMF 218 may send to the UDM 216 (or the UDM 216 may receive from the AMF 218) an AMF-UDM UE Context Update Request message (1072) to update the mobility management parameters for the UE 202. The message (1072) may include identifiers to identify the UE 202 (such as UE temporary ID, IMSI, GUTI) and UE context or new UE context parameter values that have changed. AMF 218 may then receive from UDM 216 (or UDM 216 may send AMF 218) an AMF-UDM UE Context Update Response message (1074) to confirm that the mobility management parameters in the UE context have been updated in UDM 216. Other steps may be added. to procedure (770).

In FIG. 11 illustrate in a message processing flowchart an example of an SMF-PCF session update procedure (775) according to an embodiment of a session establishment procedure (700). The SMF 220 may send to the PCF 222 (or the PCF 222 may receive from the SMF 220) an SMF-PCF UE Session Update Request message (1176) to update the session parameters for the UE 202. The message (1176) may include identifiers to identify the UE 202 (such as temporary UE ID, IMSI, GUTI) and UE context (session control, QoS parameters, billing information) or new UE context parameter values that have changed. The SMF 220 may then receive from the PCF 222 (or the PCF 222 may send to the SMF 220) an SMF-PCF Session Update Response message (1178) to confirm that the session control parameters of the UE 202 have been updated in the PCF 136. Other steps may be added to the procedure. (775).

In FIG. 12 illustrate in flowchart an example of a session establishment method (1200) according to a session establishment procedure (700). Method (1200) is performed by SMF 220. SMF 220 may be implemented as a session management functional module on a server at CN 206. SMF 220 may be configured to receive a session request message (1210). The session request message may be from the AMF 218 that received the session request message from the UE 202. Once the SMF 220 receives the session request message, the SMF 220 may determine if the UE 202 is authorized to request a service (1220). To perform this service authorization, the SMF 220 may access the user's subscription information in the UDM 216. If the service is not authorized (1220), then the SMF 220 may send an appropriate session formation response message (760) to the UE 202 via the AMF 218. As described above, the session formation response may include a session deny code. If the service is authorized (1220) and if session management optimization is to be performed based on the mobility template and if the SMF 220 is not yet subscribed to the AMF for information (1230), then the SMF 220 may subscribe to the AMF 218 for the information (725) mobility UE as described above. It should be noted that, as described above, steps (1230) and (725) may be performed at any time before, during, or after method (2040).

SMF 220 may receive UE policies from PCF 222 (720) as described above. The SMF 220 may then send a resource setup request message (730) to the serving AN 204 via the AMF 218 as described above. SMF 220 may then receive a resource setup response message from AN 204 via AMF 218 (740) as described above. The SMF 220 may then send an UP Setup Request message to the selected UPF 212 (745) as described above. The SMF 220 may then receive a session setup response message (750) from the UPF 212 as described above. SMF 220 may then send a session formation response message (755) to AMF 218 as described above. SMF 220 may then send a session formation response message (760) to UE 202 via AMF 218 as described above.

Other methods may be added to the method (2040), including an SMF 220 storing all UE-related information in a UE SM Context Profile, including a session state parameter. SMF 220 may also optionally send UE session control information to UDM 216 (765).

In FIG. 13 illustrate in a message processing flowchart an example session change procedure (2060) in accordance with an embodiment of the present invention. The session PDU change procedure may be initiated by PCF 222, UE 202 and SMF 220. The first possible trigger for session change occurs when PCF 222 sends PCF-SMF session change request (1310a) to SMF 220. The request may include a temporary UE ID, session ID, and new SM/QoS/charging policy settings. The second possible trigger for session change occurs when UE 202 sends SMF 220 via AMF 218 a UE-SMF session change request (1310b) for an active session. The request may include the SM-NSSAI, the UE's temporary identifier, the session identifier, a list of parameters to be changed and their new values, and the UE's time zone. A third possible trigger for session change occurs when SMF 220 generates an SMF session change request (1310c) based on current UE policies and other factors (eg, load changes at UPF 212 and AN 204).

If the first and second candidate triggers were intended to generate a session change request, then SMF 220 may examine session change requests (1320). If the request comes from PCF 222 for UE policy updates (1310a), then the new policy update may be stored in the local memory of SMF 220. SMF 220 may generate a session change request for AN 204 and UPF 212 based on the new policy settings. If the request (1310b) comes from UE 202 (eg, for new QoS parameters (higher MBR or higher GBR)) SMF 220 may check the request with current UE policies. If the UE request (1310b) is allowed, then SMF 220 may generate a session change request for AN 204 and UPF 212 based on the UE request. If the UE request (1310b) is not allowed, then SMF 220 may send a reason code to the UE (1390b) and other steps of the procedure (1300) may be ignored.

UE 202 may request a session change, which may be outside the policies stored in SMF 220. For example, UE 202 may request an additional GBR stream for a current session PDU that does not have GBR streams. If UE 202 requests an additional GBR stream, then SMF 220 and PCF 222 may perform a UE policy extraction procedure. The SMF 220 may send to the PCF 222 an SMF-PCF UF Policy Request message (1330) that may include the desired policy for the additional PDU requested by the UE. The PCF 222 may return an SMF-PCF UF policy response message (1335) to the SMF 220, which may include the UE policy.

The SMF 220 may then send an SMF-AN session change request message (1340) to the AN 204 via the AMF 218. The request may include new SM parameters and/or new QoS parameters. Perhaps the AN 204 may then perform access control (1350) if a new GBR stream is requested or the current GBR stream is changed. If the QoS parameter changes are accepted, then the AN 204 may further perform a session change procedure with the UE 202. The AN 204 may send an AN-UE session change request message (1360) to the UE 202. The request may include new QoS, SM, or policy settings. After applying the new QoS, SM, or policy settings, UE 202 may send an AN-UE session change response message (1365) to the AN 204.

The AN 204 may then send the SMF-AN session change response message (1370) to the SMF 220 via the AMF 218, which may include either an acknowledgment or a reason code. If the SMF-AN session change response message includes a reason code, then steps (1380) and (1385) may be ignored. Otherwise, SMF 220 and UPF 212 may perform the SMF-UPF session change procedure. The SMF 220 may send an SMF-UPF session change request message (1380) to the UPF 212, which may include a temporary UE ID, session ID, and new session PDU parameters. UPF 212 may receive the new session parameters and check if the new parameters can be supported. If the new parameters can be supported, UPF 212 may reconfigure its resources to support the session PDU. The UPF 212 may then send an SMF-UPF session change response message (1385) to the SMF 220, which may include either an acknowledgment or a reason code. The SMF 220 may then send a response to the original request. If the session modification request is from PCF 222, then SMF 220 may send a PCF-SMF session change response message (1390a) to PCF 222, which may include an acknowledgment or a reason code. If a session change request is received from UE 202 (1310b) or SMF 220 (1310c), SMF 220 may send a PCF-SMF session change response message (1390a) to PCF 222 that contains the new session parameters. If the session change request is from UE 202 (1310b), then SMF 220 may send a UE-SMF session change response message (1390b) to UE 202, which may include an acknowledgment or a reason code. Possibly, the SMF 220 may perform a context update procedure (765) of the UE UDM 216.

In FIG. 14 illustrate in flowchart an example of a method (1400) for changing a session in accordance with a procedure (1300) for changing a session. Method (1400) is performed by SMF 220. SMF 220 can be configured to determine (1410) that a session change procedure should be performed. This determination (1410) may be related to SMF 220 receiving a PCF-SMF session change request message from PCF 222. Alternatively, this determination (1410) may be related to SMF 220 receiving a UE-SMF session change request message from UE 202. Alternatively, this determination (1410) may be due to SMF 220 generating an SFM session change request message based on current UE policies and other factors (eg, load changes at UPF 212 and AN 204). If the determination (1410) was made due to requests from PCF 222 or UE 202 (1420), then SFM 220 is configured to check received session change requests (1320) as described above. The SMF 220 may then send a session change request message to the SMF-AN to the AN 204 (1340) via the AMF 218 as described above. The SMF 220 may then receive an SMF-AN session change response message from the AN 204 (1370) via the AMF 218 as described above. The SMF 220 may then send an SMF-UPF session change request message (1380) to the UPF 212 as described above. The SMF 220 may then receive an SMF-UPF session change response message (1385) from the UPF 212 as described above. If the session modification was caused by a request from the SMF 220 (1430), then the SMF 220 may send a PCF-SMF session change response message (1390a) to the PCF 222 as described above. If the session change was caused by a request from the UE 202 (1440), then the SMF 220 may send a PCF-SMF session change response message (1390a) to the PCF 222, and then the SMF 220 may send the UE session change response message (1390b) to the UE 202 -SMF as described above.

Other steps may be added to the method (2080), including sending a PCF-SMF session change response message to PCF 222 if the PCF 222 sent the original session change request to SMF 220. Alternatively, SMF 220 may send a session change response message UE-SMF to UE 202 if UE 202 sent the original session change request to SMF 220. Additionally, SMF 23 may further send a UF SMF-PCF Policy Request message (1330) to UPF 212 and receive a UF SMF-PCF Policy Response Message (1335). PCF from UPF 212 as described above.

In FIG. 15 illustrate in a message processing flowchart an example session release procedure (1500) in accordance with an embodiment of the present invention. The session PDU release procedure (1500) may be initiated by UE 202, AN 204, UPF 212, and SMF 220. The first possible trigger for session PDU release occurs when UE 202 sends UE session SMF 220 a release request message (1510a). The message may include an SM-NSSAI, a temporary UE identifier, and a session identifier. The second possible trigger for releasing a session PDU occurs when the AN 204 sends an AN session release request message (1510b) to the SMF 220. The AN 204 may report one of: an overload condition for some session PDUs, no traffic for an extended period, and/or other conditions. A third possible trigger for releasing a session PDU occurs when UPF 212 sends a UPF session release request message (1510c) to SMF 220. UPF 212 may report at least one of congestion conditions for some session PDUs, charging policy violation (ie, time-based, data-volume-based, etc.), and/or other conditions. A fourth possible session PDU release trigger occurs when the SMF 220 decides to release the session PDU using its own logic (1510d) or by receiving information from the UE 202, AN 204, and/or UPF 212. After the SMF 220 decides to release the session, there are two options for the session release procedure for UE 202 and AN 204.

In a first variation of the session release procedure, the SMF 220 may send an SMF-UE session release request message (1520a) to the UE 202 via the AMF 218, which may include a temporary UE identifier, a session identifier, and a reason code. The reason code value may indicate the source of the session release request, such as: "session release by UE" (corresponding to step 1510a); "session release by AN" (corresponding to step 1510b); "session release by UPF" (corresponds to step 1510c); and "session release by SMF" (corresponding to step 1510d). UE 202 may then release its DRB resources and session PDU context. UE 202 may send SMF 220 via AMF 218 a session release response message (1530a) to the SMF-UE to confirm the release of AN 204 resources for the released session PDU. The SMF 220 may then send an SMF-AN session release request message (1540) to the AN 204 via the AMF 218, which may include a temporary UE ID and a session ID. The AN 204 may then remove the UE PDU context and release the DRB resources. The AN 204 may send an SMF-AN session release response message (1550) to the SMF 220 via the AMF 218 to acknowledge the release of the AN 204 resources for the released session PDU.

In a second variation of the session release procedure, the SMF 220 may send an SMF-AN session release request message (1540) to the AN 204 via the AMF 218, which may include a temporary UE ID, a session ID, and a reason code. The reason code value may indicate the source of the session release request, such as: "session release by UE" (corresponding to step 1510a); "session release by AN" (corresponding to step 1510b); "session release by UPF" (corresponds to step 1510c); and "session release by SMF" (corresponding to step 1510d). The AN 204 may then send an AN-UE session release request message (1520b) to the UE 202. The message indicates the DRB to be released (which is used to service the session PDU) and the reason code. UE 202 may then release its DRB resources and session PDU context. UE 202 may send an AN-UE session release response message (1530b) to AN 204 . The AN 204 may then remove the UE PDU context and release the DRB resources. The AN 204 may send an SMF-AN session release response message (1550) to the SMF 220 to acknowledge the release of the AN resources for the released session PDU.

The SMF 220 and UPF(s) 212 may then perform the SMF-UPF session release procedure. The SMF 220 may send an SMF-UPF session release request message (1560a) to the UPF 212. The message may include a temporary UE ID and a session ID. UPF 212 may then remove the UE PDU session context and release the resources that serve the PDU session. The UPF 212 may send a response message (1560b) to the SMF 212 releasing the SMF-UPF session. It should be noted that UPF 212 may send charging information to PCF 222 via SMF 220. Optionally, SMF 220 and UDM 216 may perform an SMF-UDM UE Context Update procedure (1570) in which UDM 216 may delete UE session PDU information. The SMF 220 and PCF 222 may then perform a SMF-PCF UE context update procedure (1580). The SMF may forward the charging information to the PCF 222. The PCF 222 may remove the released session PDU information.

In FIG. 16 illustrate in flowchart an example of a method (1600) for releasing a session in accordance with a procedure (1500) for releasing a session. Method (1600) is performed by SMF 220. SMF 220 can be configured to determine whether to release a session (1610) as described above with reference to FIG. 15. Once the determination (1610) is made, SMF 220 may send an SMF-UE release request message (1520a) to UE 202 via AMF 218 as described above. SMF 220 may then receive an SMF-UE release response message (1530a) from UE 202 via AMF 218 as described above. The SMF 220 may then send an SMF-AN session release request message (1540) to the AN 204 via the AMF 218 as described above. The SMF 220 may then receive an SMF-AN session release response message (1550) from the AN via the AMF 218 as described above. The SMF 220 may then send an SMF-UPF Session Release Request message (1560a) to the UPF 212 as described above. The SMF 220 may then receive an SMF-UPF Session Release Response Message (1560b) from the UPF 212 as described above. The SMF may then perform a SMF-PCF UE Context Update procedure (1570) with PCF 222 as described above. Other methods may be added to the method (1600) including SMF 220 and UDM 216 performing an optional SMF-UDM UE Context Update procedure (765) as described above.

In FIG. 17 illustrates in flowchart another example of a method (1700) for releasing a session in accordance with a procedure (1500) for releasing a session. Method (1700) is performed by SMF 220. SMF 220 may be configured to determine whether to release the session (1610). Determination (1610) may be based on the receipt of a session release request message from UE 202. Alternatively, determination (1610) may also be based on receipt of a session release request message from AN 204. Alternatively, determination (1610) may also be is based on receiving a session release request message from UPF 212. Alternatively, the determination (1610) may also be based on the SMF 220 logic. 204 through AMF 218 as described above. The SMF 220 may then receive the SMF-AN response session release message (1550) from the AN via the AMF 218 as described above. It should be noted that before the SMF receives the session release response message (1550) from the AN to the SMF-AN, the AN sent a session release request to the UE AN-UE and received a session release response message from the UE as described above. The SMF 220 may then send an SMF-UPF Session Release Request message (1560a) to the UPF 212 as described above. The SMF 220 may then receive an SMF-UPF session release response message (1560b) from the UPF 212 as described above. The SMF may then perform a SMF-PCF UE Context Update procedure (1570) with PCF 222 as described above. Other methods may be added to the method (1700) including SMF 220 and UDM 216 performing an optional SMF-UDM UE Context Update procedure (765) as described above.

In FIG. 18 illustrate in a message processing flowchart an example session PDU connection state transition procedure (1800) in accordance with an embodiment of the present invention. UE 202 may have its own logic to determine if the connection state of a session can be changed. Node 204 may monitor session PDU UL/DL activity to query SMF 220 to change session connection state to "Session-IDLE". The procedure (1800) may be initiated by the UE 202 or the AN 204. The first possible trigger for the session PDU connection state transition procedure is initiated when the UE 202 sends a connection session state transition request (1810a) to the SMF 220 (either "Session-ACTIVE" or "Session -IDLE"). Message (1810a) may include a temporary UE identifier, SM-NSSAI(s), session identifier(s), and new session connection state. A special session identifier value (eg, a wildcard) may be used to represent that all session PDUs served by the same SM specified in the SM-NSSAI are in the dormant state. Another possible trigger for the session PDU connection state transition procedure is initiated when the AN 204 monitors session PDU activity of all session PDUs and the AN 204 detects the absence of session UL and DL packets after the idle session timer set by SMF 220 during the session establishment procedure (700). The AN 204 sends a "Session-IDLE" state transition request (1810b) to the SMF 220 that requests the state of one session PDU or multiple session PDUs to be set to the "Session-IDLE" state. The message may include a temporary UE identifier, SM-NSSAI(s), session identifier(s), and an AN identifier. A special session identifier value (eg, a wildcard) may be used to represent that all session PDUs served by the same SM specified in the SM-NSSAI are in the dormant state.

The parameter for the session connection state of the SM UE context is set to a new state as requested (1820). The SMF 220 may then notify the AN 204 of the session connection state transition (1830a). The notification may include a UE ID, a session ID, and other information. If the session connection state changes to "Session-IDLE", then the SMF 220 may request that the AN 202 release the session PDU information including the NG3 tunnel information. The AN 204 may also release the radio resources that serve the session PDU. If the session connection state changes to "Session-ACTIVE", then SMF 220 may send a session context PDU including NG3 tunnel information and a QoS profile to the AN. The AN 204 may then prepare radio resources to serve the session PDU according to the QoS profile. If the QoS flows require admission control, the AN 204 may perform admission control. The AN 204 may then send a session state transition response message (1830b) to the SMF 220. The response message can be an acknowledgment or an error (reason) code. If the response message is a reason code, then the remaining steps in the procedure are not performed.

If the response message (1830b) is not a reason code, then SMF 220 may request UPF 212 to perform an Update UE Context service (1840). The SMF 220 may request the UPF 212 to release the NG3 tunnel information from the UE context in the UPF 212 if the session connection state changes to "Session-IDLE". In this request, the AN 204 tunnel endpoint ID can be set to NULL. If the session connection state changes to "Session-ACTIVE", then the SMF may request the UPF 212 to add the IP address of the AN 204 for the NG3 tunnel information. The SMF 220 may then request the AMF 218 to perform an Update UE Context service (1850). The session connection state in the context of UE AMF 218 may be set to the new session connection state. The notification may include a UE ID, a session ID, and a requested new session connection state. AMF 218 may store the connection state of the session in its UE context.

SMF 220 may then notify UE 202 of the new session connection state (1860a). The notification may include a session ID, a new session connection state, and a reason code if the SMF 220 received the reason code from the AN 204. The UE 202 may then send a "Session-IDLE" state transition response message (1860b) to the SMF 220. The SMF 220 may then requests the PCF 222 to perform the "update UE context" service (1870). The new session connection state may be sent to PCF 222. The service request from SMF 220 may include a UE ID, a session ID, and a new session connection state. The request (1870) may be a UE SMF-PCF context update procedure (1580) as described above.

In FIG. 19 illustrate in flowchart an example of a method (1900) for performing a state transition in accordance with a PDU session connection state transition procedure (1800). Method (1900) may be performed by SMF 220. SMF 220 may be configured to receive a session state transition request (1910). The request may be from the UE 202 or from the AN 204. The SMF 220 may then update the connection state parameter of the SM UE context session to the requested connection state (1820). The SMF 220 may then send a session state transition request message to the AN 204 (1830a). The SMF 220 may then receive a session state transition response message from the AN 204 (1830b). The SMF 220 may then send an Update UE Context service request to the UPF 212 (1840). The SMF 220 may then send a UE Context Update service request to the AMF 218 (1850). SMF 220 may then send a session state transition notification to UE 202 (1860a). SMF 220 may then receive a session state transition response from UE 202 (1860b). The SMF 220 may then send an Update UE Context service request to the PCF 222 (1870). Other steps may be added to the PDU session connection state transition procedure (1800).

In FIG. 20 illustrate in a message processing flowchart an example of an RRC suspend procedure (2000) in accordance with an embodiment of the present invention. The result of this procedure (2000) may be a session PDU transition from an active state to a "Session-IDLE" PDU state. UE 202 may have its own logic to determine if the RRC state can be paused to save power, but without interrupting the current session(s). In this scenario, the state of the current session(s) may be set to "Session-IDLE" at AN 204, UPF 212, SMF 220, PCF 222, and possibly at UDM 216. UE 202 may have multiple session PDUs, where each session may be served by a single UPF 212 or multiple UPFs 212. A UE may have access to multiple network segments, where each segment may have a separate SMF 220 to serve the UE 202. The RRC suspend procedure (2100) may be initiated by the UE 202 or the AN 204. The first possible trigger for The "Session-IDLE" state transition is triggered when the UE 202 sends an RRC Hold Request message (2010a) to the AN 204. UE-AN The second possible trigger for the "Session-IDLE" state transition is initiated when the AN 204 detects no activity in the UL and DL (2010b). After the UE-activity-timeout timer expires, the AN 204 may suspend the RRC connection.

The AN 204 and the AMF 218 may then perform the AN-AMF CN UE State Update procedure (2020) The AN 204 may send the AN-AMF UE CN-IDLE State Transition Request message (2020a) to the AMF 218, which may include the temporary UE ID, a new CN-IDLE state of the UE 202 and reason code "UE requests RRC pause" (corresponding to step 2010a) or "all sessions idle" or "no data activity" (corresponding to step 2010b). AMF 218 may then change the state of UE 202 to CN-IDLE and stop AMF 218 procedures by UE 202. The AN may then send a UE CN-IDLE U-ANF state transition response message (2020b) to UE 202.

Then, AN 204 and UE 202 may perform a UE-AN RRC Suspend procedure (2030). The AN 204 may send the UE-AN RRC Suspend Response Message (2030a) to the UE 202, which may include a reason code and an RRC Resume ID. The value of the reason code may be the same as the reason code in step (2020a). The AN 204 may then deactivate all AS signaling procedures and designate all DRBs in a suspended state. Then, UE 202 may perform a UE RRC Suspend procedure (2030b).

The AMF 218 and SMFs 220 may then perform an AMF-SMF UE CN-IDLE status update procedure (2040). AMF 218 may send an AMF-SMF UE CN-IDLE state transition request message (2040a) to SMF(s) 220, which may contain a temporary UE ID, a new UE 202 CN-IDLE state, and a possible reason code as in step (2020a). The SMF 220 may then send a CNE IDLE UF AMF-SMF state transition response message (2040b) to the AMF 218. By acknowledging the UE CN-IDLE State Transition Request message received from AMF 218, SMF 220 may implicitly assume that AN 204 has placed all UE 202 PDUs in the "Session-IDLE" state.

The SMF 220 may then perform an all session SMF deactivation procedure (2050) to place the session PDUs in the "Session-IDLE" state in the UPF(s) 220. The SMF 220 may send to the UPF(s) 212 that are serving the UE session(s) PDUs. , an SMF-UPF request message (2050a) to deactivate all sessions, which may indicate that the session PDU state should be changed to the "Session-IDLE" state. Message (2050a) includes a temporary UE ID and session ID(s) (or a wildcard parameter). The wildcard parameter (which may be a special value for a session identifier) may indicate that the state of the PDUs of sessions served by UPF 212 should be set to "Session-IDLE". The UPF 212 may then set the "Session-State" field of the UE's session PDU context to "Session-IDLE". UPF 212 may follow the SM policy in the maintain-UE-context-for-sessions-action parameter. If, in this UPF 212, UE 202 has no other active session PDU (served by other RATs), and if the value of the "support-UE-context-for-sessions-action" parameter is set to "support", then UPF 212 (and SMF 220 ) can save the UE context regardless of the session state. If, in this UPF 212, UE 202 has no other active session PDU (served by other RATs), and if the value of the "maintain-UE-context-for-sessions-action" parameter is set to "may-be-released", then the UPF 212 may save the full UE context, depending on the storage resource.

The UPF 212 may then send a response message (2050b) to the SMF 220 SMF-UPF to deactivate all sessions. If the UE context is released, then UPF 212 may send to SMF 220 the complete UE context including the SM UE context and the billing UE context. It should be noted that the UPF 212 may also send a billing UE context to the PCF 222 . If UPF 212 releases the UE context, then SMF 220 may receive the complete UE context from UPF 212 and may store the complete UE context in local memory. It should be noted that the UPF UE context and the SMF context may have some common fields such as UE temporary identifier, IP address(es), and TFT. To conserve memory resources, SMF 220 may only store additional UPF UE context parameters that are not present in the SMF UE context. Perhaps the SMF 220 may notify the AN 204 that all session PDUs are in the "Session-IDLE" state by sending the SMF-AN an all session idle notification message (2050c). It is also possible that SMF 220 and UDM 216 may perform the SMF-UDM UE Context Update procedure (765) as described above. The SMF 220 and PCF 222 may then perform an SMF-PCF UE Context Update procedure (1580), which may include the UE's CN state and session state, which change their session state. It should be noted that PCF 222 may also access UDM 216 to obtain a UE context if the policy is to store the UE context in UDM 216.

In FIG. 21 illustrate in flowchart an example of a session state transition method (2100) in accordance with the RRC suspend procedure (2000). Method (2100) is performed by SMF 220. SMF 220 may be configured to receive AMF-SMF UE CN-IDLE State Transition Request message (2040a) from AMF 218 as described above. The SMF 220 may then send an AMF-SMF CN-IDLE UE status change response message (2040b) to the AMF 218 as described above. The SMF 220 may then send to the UPF 212 SMF-UPF a request message (2050a) to deactivate all sessions as described above. The SMF 220 then receives a response message (2050b) from the SMF-UPF UPF 212 to deactivate all sessions as described above. The SMF 220 then performs the SMF-PCF UE Context Update procedure (1580) with the PCF 222 as described above. Other methods may be added to the method (2100) including the SMF optionally sending the SMF-AN an all session idle notification message to the AN 204 and performing the SMF-UDM UE context update procedure (765) as described above.

In FIG. 22 illustrate in flowchart an example of a session state transition method (2200) in accordance with the RRC suspend procedure (2000). Method (2200) is performed by AN 204. AN 204 may be configured to determine to release a session (2210). The determination (2210) may be based on the receipt of the UE-AN RRC Hold Request message from the UE 202. Alternatively, the determination (2210) may also be based that the AN 204 detects no activity in the UL and DL. Once the determination (2210) is made, the AN 204 may send an AN-AMF UE CN-IDLE UE State Change Request message (1620a) to the AMF 218 as described above. AMF 218 may then send a AN-AMF UE CN-IDLE state transition response message (1620b) to AN 204 as described above. The AN 202 may then send a RRC Suspend Response Message (1630a) to the UE-AN as described above. Other steps may be added to the method (1800) including the AN 204 receiving the SMF-AN entire session idle notification message (1650c) from the SMF 220 as described above.

In FIG. 23 illustrates in a message processing flowchart an example of an RRC resume procedure (2300) in accordance with an embodiment of the present invention. The procedure (2300) may be initiated when the RRC UE is in the RRC-suspended state and the UE 202 has data to send to the UL. The procedure (2300) is initiated when the UE 202 sends a UE-AN RRC Resume Request message (2310) to the AN 204. The message may include at least an RRC Resume ID. Perhaps the RRC Resume Request includes the DRB IDs or the session ID to be resumed. If the AN ID indicates the previous (former) AN 204' when the RRC was paused (note that the former AN ID is provided in the RRC resume ID), then the new serving AN 204 and the former AN 204' execute the UE context of the handover procedure (2320), so that the new serving AN 204 is able to obtain the UE context from the previous AN 204'. After sending the UE context to the new serving AN 204, the previous AN 204' may release the UE context.

The AN 204 and AMF 218 then perform a CN-CONNECTED UE AN-AMF UE state transition procedure (2330_). The AN 204 may check the UE context to find a serving AMF 218. UE AN-AMF UE The message may include a temporary UE identifier and a new CN-CONNECTED state The AMF 218 may then send a AN-AMF UE CN-CONNECTED state transition response message (2330b) to the AN 204. If the AMF 218 may support UE 202, the UE CN state transition response message may include an acknowledgment Otherwise, the message may contain a reason code.

It should be noted that if the RRC resume request in step 2310 does not include a DRB identifier or a session identifier, then the next Session-ACTIVE state transition procedure (2400) in AN-SMF is not performed. In addition, if the CN-CONNECTED state transition response includes a reason code, the UE 202 performs a reattach procedure, and procedure (2400) and step (2380) are not performed. At step (2370), the RRC resume response may include a reason code generated by AMF 218 at step (2330b). In addition, if there are errors in step (2320) or (2330), procedure (2400) and step (2380) are not performed, UE 202 does not resume the suspended RRC connection. At step (2370), the AN 204 may send a reason code to the UE 202 so that the UE can initiate a new (re) join procedure (300).

The AN 204 may send an AN-SMF "Session-ACTIVE" state transition request message (2340) via the AMF 218 to the SMF 220, which may include the session ID(s), its new "Session-ACTIVE" state, SM-NSSAI, which must be recognized by the AMF 218 to select the SMF, and the temporary ID of the UE. The message may contain a reason code "RRC resumed by UE". If the "active-session-when-RRC-resumed" parameter is set to "Yes" for some session PDUs, the AN 204 may contain the session ID(s) of those session PDUs in the "Session-ACTIVE" state transition request. In the case where UE 202 is being served by a new AN 204, the AN-SMF Session-ACTIVE state transition request may also include a Path AN Switch Request message, which may include the IP address of the new serving AN 204.

The SMF 220 and UPF 212 may then execute the SMF-UPF Session-ACTIVE state transition procedure (2350). The SMF 220 may send a Session-ACTIVE SMF-UPF state transition request message (2350a) to the UPF 212. The message may include a temporary UE ID, session IDs, and a new "Session-ACTIVE" state. If UPF 212 has released the UE context, then SMF 220 may also send the previously stored UE context to UPF 212 in an SMF-UPF Session-ACTIVE state transition request message. In the case where UE 202 is being served by a new serving AN 204, the SMF-UPF Session-ACTIVE state transition request may also include a path AN switch request, which may include the IP address of the new serving AN 204. UPF 212 prepares its resources according to the UE context. If the resources in the UPF 212 are ready, the UPF 212 may send an acknowledgment "Session-ACTIVE" SMF-UPF state transition response message (2350b) to the SMF 220. If the UPF 212 has sufficient resources to support the resumed session(s), then the session state in the context of the UPF 212 UE may be changed to "Session-ACTIVE". If the UPF 212 does not have sufficient resources to support the resumed session(s), then the "Session-ACTIVE" state transition response message may include a reason code.

The SMF 220 may send an AN-SMF "Session-ACTIVE" state transition response message (2070) to the AN 204, which may include the state of the requested session identifiers. In its context, the UE AN 204 may change the session state from "Session-IDLE" to "Session-ACTIVE". For sessions that are not activated due to errors in steps (2030) and (2050), the AN-SMF "Session-ACTIVE" state transition response message may include a reason code. Optionally, SMF 220 and UDM 216 may perform a SMF-UDM UE Context Update procedure (765) as described above.

SMF 220 and PCF 222 may perform a procedure (1580) update the context of the UE SMF-PCF. The AN 204 may then send a UE-AN RRC Resume Response Message (2370) to the UE 202. The message may include either an acknowledgment or reason codes for requesting RRC renewal. The reason codes may indicate AN error 204 (at step (2320)), AMF (at step (2330), or RRC resume errors. If the UE-AN RRC resume request included a DRB ID (or session ID) at step (2310) , then the UE-AN RRC Resume Response message may also include either an acknowledgment or a reason code for each requested DRB identifier.

UE 202 has UL data to send in the DRB that was requested in step (2310). The UE may send a UL grant request message (2380) to the AN 204 . AN 204 provides resources for DRB in UL. Thereafter, the UE may send data on the DRB.

In FIG. 24 illustrate in flowchart an example of a session state transition method (2400) in accordance with an RRC resume procedure (2300). Method (2400) is performed by SMF 220. The method comprises SMF 220 configured to receive from AN 204 via AMF 218 AN-SMF Session-ACTIVE state transition request messages (2340) as described above. The SMF 220 may then send the SMF-UPF "Session-ACTIVE" state transition request message (2350a) to the UPF 212 as described above. The SMF 220 then receives an SMF-UPF "Session-ACTIVE" state transition response message (2350b) from the UPF 212 as described above. The SFM 220 may then send an AN-SMF "Session-ACTIVE" state transition response message (2360) to the AN 204 via the AMF 218 as described above. The SMF 220 then performs the SMF-PCF UE Context Update procedure (1580) with the PCF 222 as described above. Other methods may be added to the method (2400), including the SMF further performing the SM-UDM UE Context Extraction procedure, performing the SMF-UE Context Update procedure (765), and receiving from the UE (via the AN 204) a UL Grant Request message. as described above.

In FIG. 25 illustrate in flowchart an example of a session state transition method (2500) in accordance with an RRC resume procedure (2300). The method (2500) is performed by the AN 204. The method comprises an AN 204 receiving a UE-AN RRC Resume Request (2310) from a UE 202 as described above. Then, if the AN ID designates the previous AN 204' (2510), then the serving AN 204 and the previous AN 204' perform the UE context handover procedure (2320) as described above. The AN 204 may send a CNE-CONNECTED UE AN-AMF state transition request message (2330a) to the AMF 218 as described above. The AN 204 may then receive a AN-AMF CN-CONNECTED UE Transition Response Message (2330b) from the AMF 218. The AN 204 may then send an AN-SMF "Session-ACTIVE" State Transition Request Message (2340) to the SMF 220 via the AMF 218 as described above. The AN 204 may then receive an AN-SMF "Session-ACTIVE" state transition response message (2350) from the SMF 220 via the AMF 218 as described above. The AN 204 may then send a UE-AN RRC Resume Response message to the UE as described above. Other methods may be added to method (2500) including forwarding UL PDU transmissions received from UE 202 to UPF 212.

FIG. 26 illustrates in a message processing flowchart an example of a session-ACTIVE single PDU state transition procedure (2600) initiated by UE 202 or AN 204, in accordance with an embodiment of the present invention. UE 202 may have its own logic to determine if the RRC state can be paused to save power, but without interrupting the current session(s). In this scenario, the state of the current session(s) may be set to "Session-ACTIVE" at AN 204, UPF 212, SMF 220, PCF 222, and possibly at UDM 216. UE 202 may have multiple session PDUs, where each session may be served by a single UPF 212 or multiple UPFs 212. UE 202 may have access to multiple network segments, where each segment may have a separate SMF 220 to serve UE 202. A one-to-one mapping between the session PDU ID and the DRB ID is used.

The individual Session-IDLE PDU state transition procedure (2600) may be initiated by the UE 202 and the AN 204. The first possible trigger for the individual Session-IDLE PDU state transition procedure (2600) is initiated when the UE 202 sends a message to the AN 204 (2610a) DRB-suspend request. A second possible trigger for a separate Session-IDLE PDU session state transition procedure (2600) is triggered when the AN 204, which monitors session PDU activity of all session PDUs, does not detect session UL and DL (2610b) packets after the session-monitoring timer. -timeout". Note that each session PDU may have a session-monitoring-timeout parameter configured by PCF 222. SMF 220 may receive a session-monitoring-timeout parameter from PCF 222 and send it to AN 204 during the procedure. (700) establishing a session.

The AN 204 may send an AN-SMF "Session-IDLE" state transition request message (2620) to the SMF 220, which may request that one or more session PDUs be set to the "Session-IDLE" state. Message (2620) may include a temporary UE identifier, SM-NSSAI(s), and session identifier(s). A special session identifier value (eg, wildcard) may indicate that PDU sessions served by the same SM specified in the SM-NSSAI should be set to idle.

The SMF 220 and UPF(s) 212 may then execute the SMF-UPF Session-IDLE state transition procedure (2630). The SMF 220 may send to the UPF(s) 212 that are serving the Session(s) PDU(s) a "Session-IDLE" State Transition Request Message(s) (2630a) indicating the "Session-IDLE" state of the Session(s) PDU(s). Message (2630a) may include a temporary UE ID and session ID(s). A special session identifier value (eg, a wildcard) may indicate that the state of PDU sessions served by UPF 212 should be set to "Session-IDLE". Then, if there are UL or DL packets in the UPF 212 buffer, the UPF 212 may send an SMF-UPF "Session-IDLE" state transition response message (2630b) to the SMF 220, which may include a reason code. The session state remains "Session-ACTIVE". If there are no DL packets in the UPF 212 buffer, the UPF 212 may set the "Session-State" field of the session context of the UE PDU to "Session-IDLE". The UPF 212 may send an acknowledgment "Session-IDLE" state transition response message (2630b) to the SMF 220 of the SMF-UPF. If there are no more active sessions in the same UPF 212, the UE context may be released and the UPF 212 may send the complete UE context, including the SM context and the PCF context, to the SMF 220.

The SMF 220 may then send an AN-SMF "Session-IDLE" state transition response message (2640) to the AN 204 (response to step (2620)). The message (2640) may include either an acknowledgment or a reason code in step (2630b). If UPF 212 releases the UE context, SMF 220 may receive the full UE context and charging information from UPF 212. SMF 220 may store the full UE context in local memory and forward the charging information to PCF 222 as in step (2670) below. It should be noted that the UPF UE context and the SMF context may have some common fields such as UE temporary ID, IP address(es), and TFT. To conserve memory resources, the SMF 220 may store only UPF UE context parameters that the SMF UE context does not have.

Then, AN 204 and UE 202 may optionally perform an AN-UE DRB Suspend procedure (2650). UE 202 may perform a UE DRB suspend procedure. After this step (2650), there may be no AS signaling for the suspended DRB, and there may be no NAS signaling for the PDU session associated with the suspended DRB. It is also possible that SMF 220 and UDM 216 may perform the SMF-UDM UE Context Update procedure (765) as described above. However, this step (765) may be mandatory if the SMF 220 releases the UE context. The SMF must then send the entire UE UP context and UE SM context to UDM 216. The SMF 220 and PCF 222 may then perform an SMF-PCF UE Context Update procedure (1580), which may include the UE CN state, the state of the sessions that change their session state, and billing information. It is noted that it is possible that the PCF 222 may also access the UDM 216 to obtain the UE context if the policy is to store the UE context in the UDM 216. In addition, it should be noted that the UPF 212 may directly send the charging context to the PCF 222.

In FIG. 27 illustrate in flowchart an example of a session state transition method (2700) in accordance with a single PDU Session-IDLE state transition procedure (2600). The method (2700) is performed by the SMF 220. The method comprises an SMF 220 configured to receive AN-SMF "Session-IDLE" state transition request messages (2620) from the AN 204 via the AMF 218 as described above. The SMF 220 may then send the SMF-UPF "Session-IDLE" state transition request message (2630a) to the UPF 212 as described above. The SMF 220 then receives the SMF-UPF "Session-IDLE" State Transition Response Message (2630b) from the UPF 212 as described above. The SMF 220 may then send an AN-SMF "Session-IDLE" state transition response message (2640) to the AN 204 via the AMF 218 as described above. The SMF 220 then performs the SMF-PCF UE Context Update procedure (1580) with the PCF 222 as described above. Other methods may be added to the method (2700), including the SMF possibly performing the SMF-UDF UE Context Update procedure (765) as described above.

In FIG. 28 illustrate in flowchart an example of a session state transition method (2800) in accordance with a single PDU's Session-IDLE state transition procedure (2600). The method (2800) is performed by the AN 204. The method comprises an AN 204 determining that a session state transition (2810) should be performed. The determination (2810) may be performed by the AN 204 receiving the UE-AN DRB Suspend Request (2610a) as described above. The determination (2810) may also be performed by the AN 204 which monitors session PDU activity of all session PDUs and detects the absence of session UL and DL packets (2610b) after the session-monitoring-timeout timer as described above. The AN 204 may then send the AN-SMF "Session-IDLE" state transition request message (2620) to the SMF 220 via the AMF 218 as described above. The AN 204 may then receive from the SMF 220, via the AMF 218, an AN-SMF "Session-IDLE" State Transition Response Message (2640), as described above. Other methods may be added to the method (2800) including the AN performing the AN-UE DRB Suspend procedure (2650) as described above.

In FIG. 29 illustrates, in a message processing flow diagram, an example PDU "Seassion-ACTIVE" state transition procedure (2900) in accordance with an embodiment of the present invention. The procedure (2900) is initiated by a UL grant request when the UE 202 is in the RRC-CONNECTED state and has UL data to be sent on the suspended DRB. UE 202 may send a UL-AN UL grant request message (2910) to the AN 204. The message may include the DRB identifier(s). If the DRB is in the dormant state, then a UL grant request may imply a request to resume that DRB. If the sessions with the session ID(s) associated with the DRB ID(s) are in the "Session-IDLE" state, then procedure (2400) as described above can be further executed. The AN 204 may then send a UE-AN UL-UE grant response message (2920) to the UE 202, which may include the DRB ID(s) or session ID(s) and an acknowledgment or reason code for each DRB. In case a reason code is contained for DRB, UE 202 may request a new session when CN 206 cannot resume an idle session. After receiving an acknowledgment from the AN 204 in a UL-AN UL grant response message (2920), UE 202 may send a UL packet to the AN 204 (2930) for renewed DRB(s). The AN 204 may then forward the UL packets (2930) to the UPF 212.

In FIG. 30 illustrates, in a message processing flow diagram, an example PDU "Seassion-ACTIVE" state transition procedure (3000) in accordance with an embodiment of the present invention. In this case, the current connection state of the session is in the "Session-IDLE" state. UPF 212 may not have NG3 tunnel information in the UE context. The procedure (3000) may be initiated by UPF 212 receiving a DL packet from a Packet Data Network (PDN) 208 . The packet may be buffered at UPF 212. UPF 212 may then send a Get UE Context Update Request message to SMF 220a to obtain the NG3 tunnel endpoint ID. The SMF 220 then checks the status of the CN 206 in its UE context. If UE 202 is in the CN-CONNECTED state, then steps (3030a), (3030b), (3030c) may not be performed.

If the UE 202 is in the CN-IDLE state, the SMF 220 may send an "Update UE CN State" request (3030a) to the AMF 218 so that the AMF 218 can provide the UE paging function. Message (3030a) may include a temporary UE identifier. AMF 218 may then perform a UE paging procedure (3030b). This may include a UE context handover procedure if UE 202 is served by a new AN 204. If AMF 218 successfully pages UE 202, then the UE enters the CN-CONNECTED state. The AMF 218 may send a UE CN Status Update (3030c) service to the SMF 220 that indicates that the UE 202 is in the CN-CONNECTED state.

The SMF 220 may then update the CN-CONNECTED state of the UE 202. The SMF 220 may send a "Session-ACTIVE" state transition request message (3040) to the AN 204. The message may include a temporary UE ID, a session ID, a UE PDU session context, and a QoS profile. The AN 204 may then set up radio resources (3050) with the UE 202 for the session PDU. This step (3050) may include access control, if required. The AN 204 may then send a "Session-ACTIVE" state transition response message (3060) to the SMF 220, which may include an SM-NSSAI, a temporary UE identifier, a session identifier, and either an acknowledgment or a reason code for that session ID.

The SMF 220 may then send a "get UE context update" service response message (3070) to the UPF 212. If SMF 220 has received a reason code from AMF 218, then SMF 220 may send a reason code to UPF 212 to release the UE context and discard received packets. SMF 220 may also release the UE context. If SMF 220 receives a reason code from AN 204, then SMF 220 may send a reason code to UPF 212. UPF 212 may then discard received packets. If the SMF 220 receives the confirmation at steps (3030) and (3060), then the SMF 220 may send a "get UE context update" response message (3070) to the UPF 212, which may include the UE ID, session ID, and tunnel endpoint ID. NG3. The SMF 220 and PCF 222 then perform the SMF-PCF UE Context Update procedure (1580) as described above. The SMF 220 may request the PCF 222 to perform an "Update UE Context" service, where a new session connection state may be sent to the PCF 222. The service request from the SMF 220 may include a UE ID, a session ID, and a new session state.

In FIG. 31 illustrate in flowchart an example of a method (3100) for performing a Session-ACTIVE state transition in accordance with a Session-ACTIVE PDU state transition procedure (3000). Method (3100) may be performed by SMF 220. SMF 220 may be configured to receive a Get UE Context Update Service Request message (3020) from UPF 212. SMF 220 may send an Update UE CN Status Service Request message (3030a) for AMF 218. The SMF 220 may then receive a Update UE CN Status Service Response Message (3030c). The SMF 220 may then send a "Session-ACTIVE" state transition request message (3040) to the AN 204 via the AMF 218. The SMF 220 may then receive a "Session-ACTIVE" state transition response message (3060) from the AN 204 via the AMF 218. The SMF 220 may then send a "get UE context update" service response message (3070) to the UPF 212. The SMF 220 may then perform the SMF-PCF UE Context Update procedure (1580) as described above. Other steps may be added to the method (3100).

In FIG. 32 illustrate in a message processing flowchart an example of a Session-ACTIVE PDU state transition procedure (3200) in accordance with an embodiment of the present invention. The procedure (3200) is initiated by the UPF 212 request when the session PDU is in the "Session-IDLE" state and thus the UPF 212 may not have a TFT for the idle session DL packet. The UE PDU context may be stored in either SMF 220 or UPF 212. UPF 212 receives a DL packet from Packet Data Network (PDN) 208 (3210). The packet may be buffered at the UPF 212. The UPF 212 may send a UPF-SMF UF Context Request message (3220) to the SMF 220. If UPF 212 does not have a UE context, UPF 212 may identify and send a UPF-SMF UE context request to serving SMF 220, which may include packet header information. It should be noted that some application servers may establish a tunnel with UPF 212. This tunnel may be associated with sessions handled by a particular SMF 220. UPF 212 may rely on tunnel information to identify the service of SMF 220.

SMF 220 may check the status of the CN in the context of the UE. If UE 202 is in the CN-IDLE state (ie, UE 202 is in the RRC-IDLE state or RRC-suspended state), then SMF 220 may initiate a UE paging procedure (3230). The SMF 220 may send a paging request message (3230a) to the UE SMF-AMF to the AMF 218. The message may include a temporary UE identifier. AMF 218 may then perform a UE paging procedure (3230b). This step may include a UE context handover procedure if UE 202 is being served by a new AN 204. If AMF 218 successfully pages UE 202, then UE 202 enters the CN-CONNECTED state. AMF 218 may send an SMF-AMF UE Paging Response Message (3230c) to SMF 220, which may indicate that UE 202 is in a CN-CONNECTED state.

SMF 220 may update UE 202 to be in the CN-CONNECTED state. The SMF 220 may send a Session-ACTIVE state transition request message (3240) to the AN 204 of the SMF-AN. The message may include a temporary UE ID, a session ID, and a "Session-ACTIVE" state parameter. Possibly, if the DRB is currently paused, the AN 204 initiates an ANB-UE DRB resume procedure (3224). The AN 204 may send an AN-UE DRB Resume Request message (3224a) to the UE 202. The message may include DRB identifiers. Then, UE 202 resumes the suspended DRB. UE 202 may send an AN-UE DRB Resume Response message (3224b) to AN 204, which may include a DRB identifier and either an acknowledgment or a reason code. It should be noted that in step (3224a), the AN-UE DRB Renewal Request message may be implicitly carried in the DL Channel Grant message.

The AN 204 may send an SMF-AN "Session-ACTIVE" state transition response message (3260) to the SMF 220, which may include an SM-NSSAI, a temporary UE identifier, a session identifier, and either an acknowledgment or a reason code for that session identifier. If the SMF 220 receives a reason code from the AN 204, the SMF 220 may initiate an SM establishment procedure (700) initiated by the CN 206. ) of the UPF-SMF UE context, which may include an assertion of the "Session-ACTIVE" state. If UPF 212 does not have a UE context, the message may also include the full UE context. UPF 212 may set up UP resources to support PDU sessions. Optionally, SMF 220 and UDM 216 may perform a SMF-UDM UE Context Update procedure (765) as described above. SMF 220 and PCF 222 may perform a procedure (1580) update the context of the UE SMF-PCF. UPF 212 may then send the DL packet to UE 202 (3280).

In FIG. 33 illustrate in flowchart an example of a session transition method (3300) in accordance with the Session-ACTIVE PDU state transition procedure (3210). The method comprises an SMF 220 configured to receive UPF-SMF UE Context Request messages (3220) as described above. The SMF 220 may then send to the AN 204 via the AMF 218 a Session-ACTIVE" SMF-AN state transition request (3240) as described above. The SMF 220 may then receive from the AN 204 via the AMF 218 a Session-ACTIVE"SMF-AN State Transition Response Message (3260) as described above. The SMF 220 may then send a UPF-SMF UE Context Response Message (3270) to the UPF 212 as described above. The SFM 220 may then perform the SMF-PCF UE Context Update procedure (1580) as described above. Other methods may be added to method (3300) including SMF 220 performing SFM-UDM UF context search procedure with UDM 216, SMF 220 initiating UE paging procedure, and SMF 220 performing SMF-UDM UE context update procedure. with UDM 216 as described above.

In FIG. 34 illustrates in a component diagram an example procedure (3400) of the UE CN Status Update service. AMF 218 may provide a paging service to UE 202 when UE 202 is in the CN-IDLE state. AMF 218 may maintain a UE context. The requester 3405 may send an Update UE State Request message (3410) to the AMF 218. The message may include a UE ID. Requestor 3405 may be SMF 220 as in step (3030a) above. The supplicant 3405 may also be any network function that can communicate with the AMF 218. The AMF 218 may then send an "Update UE CN Status" response message (3420) to the supplicant 3405, which may include an acknowledgment of the UE and IP CN-CONNECTED status. -address AN 204. If paging fails, the response may contain a reason code.

In FIG. 35 illustrates in a component diagram an example procedure (3500) of the change session PDU service. This service (3500) provides a session PDU change service such as QoS parameters and billing parameters. SMF 220 may maintain a UE context. The requestor 3505 may send a session change request message (3510) to the SMF 220. The message may include a UE identifier, a PDU session identifier, and new session parameters. The supplicant 3505 may be any network function that can communicate with the SMF 220. The SMF 220 may then send a "session change" response message (3520) to the supplicant 3505 to acknowledge the service termination. The message (3520) may include an acknowledgment or a reason code.

In FIG. 36 illustrates in a component diagram an example procedure (3600) of the Get UE Policies service. PCF 222 may provide UE policies to requestor 3605. PCF 222 may have policies for services, DN 208, time zone, and UE 202. Requestor 3605 may send a Get UE Policies Request message (3610) to PCF 222. The message may include the PDU session type, DN, UE 202 time zone, and requested policy such as SM policy, access and mobility (AM) policy, QoS policy, and billing policy. The supplicant 3605 may be any network function that can communicate with the PCF 222. The PCF 222 may then send a "get UP policies" response message (3620) to the supplicant 3605, which may include the requested policy.

In FIG. 37 illustrates in a component diagram an example of a procedure (3700) of the Update UE Context service. PCF 222 may provide a UE context update service to a requestor 3605 for some scenarios, including dynamic policy. PCF 222 may have policies for services, DN 208, time zone, and UE 202. Requestor 3605 may send an Update UE Context Request message (3710) to PCF 222. The message may include a UE identifier, session identifiers, and a list of parameters, and their respective new values. Requester 3605 may be SMF 220 as in step (1580) above. The requester can also be any network function that can communicate with the PCF 222. The PCF 222 can then store the new parameter values in the context of the UE. The PCF 222 may send an "Update UE Context" response message (3720) to the requester 3605 to confirm that the service has been performed or report an error (via a reason code).

In FIG. 38 illustrates in a component diagram an example of a procedure (3800) of the Update UE Context service. When a session PDU is established, the UPF 212 may have a UE context. The requester 3805 may send to the UPF(s) 212 that are serving the session PDU an Update UE Context Request message (3810). The message may include a UE identifier, session identifier(s), and a list of parameters and their respective new values. The new value can be NULL. If the new tunnel endpoint ID is NULL, UPF 212 may contact SMF 220 if UPF 212 does not know how to forward the packet. Requester 3805 may be SMF 220 as in step (3070) above. Requestor 3805 can also be any network function that can communicate with UPF 212. UPF 212 can receive new session parameters and check if the new parameters can be supported. If the new parameters can be supported, then the UPF 212 may reconfigure or release its resources to serve the PDU session. The UPF 212 may send an SMF-UPF session change response message (3820) to the SMF 220, which may include an acknowledgment to confirm that the service has been performed or to report an error (via a reason code).

In FIG. 39 is a call processing flow diagram 3900 illustrating methods that can be performed in sequence of various nodes and functions of the UE's Session-IDLE state transition in CM_Connected mode. As shown in FIG. 39, there may be several different triggers to start the session connection state transition procedure. As shown in FIG. 39, UE 202 or AN 204 may request a Session-IDLE transition. Those skilled in the art will appreciate that other triggers may also be applicable. Either UE 202 or AN 204 may send a "Session-IDLE" transition request (at 3902a and 3902b) to SMF 220. In some examples, the request message may include a temporary UE ID, session ID(s), "Session-IDLE" status or AD ID, as appropriate. There may be a difference in the information contained in a message, depending on the host or function that initiates the message. A special session identifier value (eg, a wildcard) may be used to designate all PDU sessions that match the identification requirements contained in the request. It should also be understood that SMF 220 may initiate a "Session-IDLE" state transition, either in response to another external trigger or in response to an internal condition being satisfied. SMF 220 and UPF 212 communicate with each other to perform a session update. SMF 220 may send a session update request 3904a (e.g., an N4 session update request) to UPF 212. This request may serve as a request to UPF 212 to release AN-associated NG3 information from the UE PDU session context (as identified by UPF) . This session information may include the tunnel endpoint identifier of the AN 204 and the IP address of the AN. In response to this request, UPF212 may release the session and send a 3904b response to SMF 220 to acknowledge completion of the UE context update request. The SMF 220 may then send a session update request 3906 to the AN 204, which may further be routed via the AMF 218. In some embodiments, this may take the form of an N2 session update request sent to the AN 204 via the AMF 208. The session update request may include: information such as temporary UE ID, session IDs, and "Session-IDLE" state. In response to receiving the session refresh request, the AN 204 and UE 202 may perform an RRC connection reconfiguration procedure 3908 to release allocated resources for the session(s). The AN 204 may inform the UE 202 of the session state transition through a procedure. Those skilled in the art will appreciate that there may be additional details of the interaction between the UE 202 and the AN 204, but these implementation details may vary from solution to solution. Upon releasing the session context (or sessions), the AN 204 PDU may send a session update response 3910 (a session update response, such as an N2 session update response). This response may be sent to SMF 220 and may optionally be sent via AMF 208. The response may serve to confirm completion of the "Session-IDLE" state transition at UE 202 and may include a temporary UE ID and a session ID. At this point, SMF 220 may set the session connection state (at 3912) of the UE context to "Session-IDLE". Those skilled in the art will appreciate that other services may be invoked to send a session update request and response without deviating from the idea of the present method. It should also be understood that a policy control function may also be involved.

FIG. 40 is a call processing flowchart illustrating methods that can be performed in sequence of various nodes and functions for a "Session-ACTIVE" state transition initiated by a UE in CM_Connected mode. As shown in the FIG. 40 embodiment as shown in FIG. 40, the method may be initiated by UE 202 sending an active session transition request to SMF 220. As shown in FIG. 40, step 4002, UE 202 sends a "Session-ACTIVE" request to SMF 220 (possibly via AMF 218). The message may include a temporary UE identifier, session identifier(s), and a "Session-ACTIVE" state. It should be understood that a special session identifier value (eg, a wildcard) may be used to designate all PDU sessions that satisfy other conditions specified in the request. In response, the SMF 220 may send (at 4004) a session update request, such as an N2 session update request, to the AN 204, such as via the AMF. 218 The session update request message may include a temporary UE ID, a session ID, a "Session-IDLE" state, and NG3 connection information. The AN 204 and UE 202 may perform an RRC connection reconfiguration procedure (at 4006). In one embodiment, the RRC connection reconfiguration procedure may include the AN 204 assigning radio resources to serve the PDU session in accordance with the QoS profile. If the QoS profile requires admission control, the AN 204 may perform admission control (or may invoke an admission control procedure). If there are insufficient radio resources to meet the needs of the session PDU, or if the AN 204 is otherwise unable to maintain the session, the AN 204 may instruct or otherwise inform the UE 202 to release the session PDU. If there are sufficient radio resources, and the AN 204 may otherwise maintain the session, the AN 204 may send an RRC Connection Reconfiguration message to the UE 202 that indicates the radio resource allocation. According to the RRC connection configuration, the UE 202 may set the session connection state to "Session-ACTIVE". Those skilled in the art will appreciate that other steps may be taken as part of the reconfiguration of an RRC connection. The addition of these steps may vary from implementation to implementation and thus is not discussed here. After configuring (or reconfiguring, as the case may be) an RRC connection, communication node 204 may send a session update response message (at 4008) to SMF 220. Optionally, this message may be sent to AMF 218 for delivery to SMF 220. In some embodiments, implementation the message may be a session update response N2. The message may include a temporary UE ID and a session ID. The AN 204 may use this response message 4008 to notify the SMF 220 of either the successful completion of the "Session-ACTIVE" state transition or a reason code associated with an error to successfully complete the transition, such as insufficient radio resources to support the session PDU. If the SMF 220 is notified that the transition was successful, it may send a request to the UPF 212 to update the UE's session context. This may take the form of messages 4010a and 4010b in response. If SMF 220 is not notified of a success (including a scenario in which a failure is notified), steps 4010a and 4010b may be omitted. As shown at 4010a, SM 220 may send a request to UPF 212 to update session information. This may take the form of an N4 session update request sent to UPF 212 requesting an update of NG3 information associated with AN 204 that is associated with the session context of the UE PDU at UPF 212. The request message may include a UE temporary identifier, session ID, and information NG3 that includes the AN tunnel endpoint ID and the AN IP address. In response, UPF 212 may send an acknowledgment, as shown at 4010b. This acknowledgment may take the form of an N4 session update response. If the SMF 220 receives an indication from the AN 204 that the RRC connection reconfiguration was successful, the SMF 220 may set the session connection state (at 4012) in the UE context accordingly. If the session connection state transition is successful, then SMF 220 may set the session connection state to "Session-ACTIVE". If the session connection state transition is unsuccessful (eg, the AN cannot maintain a session PDU), then SMF 220 may initiate a session release procedure. As noted above with respect to FIG. 39, the PCF may participate during session state transition procedures. It should also be understood that different services may be involved in N2 messaging.

The signaling NAS connection release procedure may be initiated by the 5G node (R)AN 204 or the AMF 218. The AMF 218 may inform the SMF 220 that the UE 202 is entering the CM-IDLE state, so that the SMF 220 may inform the UPF(s) 212 to deactivate existing PDU sessions by releasing N3 tunnel information (including IP address and tunnel endpoint ID) of the UE context in UPF 212. UE 202 may consider the NAS signaling connection disconnected if the UE detects that the RRC connection has been released. After the signaling NAS connection is disconnected, UE 202 and AMF 218 may enter the CM-IDLE state.

When UE 202 has multiple established PDU sessions, activation of UP connections of existing PDU sessions may result in activation of the UE-CN user plane connection (ie, radio data link and N3 tunnel) for the PDU session. For the UE 202 in the CM-IDLE state, either the UE 202 or the network initiated service request procedure may support independent activation of the UP connection of an existing session PDU. For UE 202 in the CM-CONNECTED state, independent activation and deactivation of UP connections of existing PDU sessions may be supported.

There may be different types of PDU session establishment procedures. One type of session setup procedure may be a UE 202 initiated session setup PDU. Another type of session setup procedure may be a network initiated session setup PDU. In the case of a network initiated procedure, the network may send a device startup message to the application(s) on the UE side. The startup payload contained in the device startup request message may include information about which application on the UE side is to initiate the session establishment request PDU. Based on this information, the UE-side application(s) starts the PDU session establishment procedure.

There may be various options for deactivating a PDU session. One type of session deactivation procedure may be that all UE 202 PDU sessions may be deactivated when the UE CM state transitions from the CM-CONNECTED state to the CM-IDLE state. Another type of session deactivation procedure could be an (R)AN 204 initiating all PDU session deactivation. The (R)AN 204 may inform the AMF 218 of the RRC release reason, such as O&M intervention, unspecified failure, user inactivity, repeated RRC signaling integrity check failure, release due to UE 202 generated connection release signaling, and so on. Another type of session deactivation procedure could be an AMF 218 initiating the deactivation of all PDU sessions due to an authentication failure. Another type of session deactivation procedure may include a (R)AN 204 initiating a selective session PDU deactivation. The (R)AN 204 may inform the SMF 220 via the AMF 218 of the reason for the selective PDU session, such as O&M interference and user inactivity.

The procedure may be used to release the N2 connection and at the same time deactivate PDU sessions when the UE 202 enters the CM-IDLE state. Fig. 41 illustrates in a message processing flowchart an example of a PDU session deactivation procedure (4100) in accordance with an embodiment of the present invention. UE 202 and (R)AN 204 may perform RRC release (600A). If the RRC connection is released, then the (R)AN 204 may interact with the UE 202 to release the RRC signaling connection. UE 202 enters the CM-IDLE state and all PDU sessions may be deactivated. Thus, UE 202 knows that RRC release implies PDU session deactivation. The (R)AN 204 may then send (message N2) a release RRC notification (4102) to the AMF 218. The message (4102) may include a reason code such as O&M intervention, UE inactivity, and so on. that, in certain scenarios, step (600A) may be initiated before or in parallel with step (4102).

The (R)AN 204 may then generate (message N11) one or more N2 release notification messages (4104) and send them via the AMF 218 to the SMF(s) 220 that serve the PDU sessions to be deactivated. Message (4104) may include a UE ID to identify the UE (such as a temporary UE ID or SUPI), a list of PDU session IDs to be deactivated, and a reason code. Alternatively, the message (4104) includes a UE ID for identifying the UE (such as a temporary UE ID or SUPI), (R)AN information, a list of PDU session IDs to be deactivated, a PDU session ID, and a reason code. The (R)AN information indicates the IP address of the (R)AN that releases the RRC connection. The SMF 220 may then send (message N4) an N3 release request (4106) to the UPF(s) 212. The message (4106) may include a UE identifier (such as a temporary UE identifier or SUPI) to identify the UE, and ID(s ) session PDUs to be deactivated. UPF 212 may then discard any remaining deactivated session PDU packets, if any. UPF 212 may release N3 tunnel information (such as (R)AN IP address and tunnel endpoint identifier) in the context of the UE session PDU of the PDU sessions to be deactivated. The UPF 212 may send (message N4) N3 a release response message (4108) to the SMF 220 confirming the release of the tunnel information N3.

The SMF 220 may send (message N11) an N2 release notification acknowledgment message (4110) to the AMF 218 to acknowledge receipt of the AMF notification message (4104) 218. The message (4110) may be sent before, after, or in parallel with the message (4106). AMF 218 may then collect all responses from SMF(s) 220 that have been notified (at step (4104)). Once all acknowledgments from the SMFs 220 have been collected, the AMF 218 may send an (N2 message) N2 release request message (4112) to the (R)AN 204 with a reason code. If step (600A) has not previously been performed in the first step of procedure (4210), (R)AN 204 and UE 202 may perform RRC release procedure (600A). (R) The AN 204 may request the UE 202 to release the RRC connection. UE 202 enters the CM-IDLE state and all PDU sessions at UE 202 may be deactivated. Upon receiving the RRC connection release acknowledgment from the UE 202, the (R) AN 204 deletes the UE context.

The (R) AN may then send (message N2) an N2 release response message (4114) to AMF 218. This message (4114) should provide an acknowledgment for step (4112). Upon receipt of the N2 release response message (4114), AMF 218 may set the CM-IDLE state in the UE context and release the N2 UE connection. The AMF 218 may then send (message N11) an N2 release confirmation message (4116) to the SMF(s) 220 to confirm the release of the N2 connection. Alternatively, the message (4116) may be omitted.

In another embodiment, if the release RRC procedure (600A) was performed in the first step of the procedure (44100), messages 4112, 414 and the release RRC procedure (600A) between message steps 4112 and 41114 may be omitted.

FIG. 42 illustrates in flowchart an example of a method (4200) for releasing an N2 connection and deactivating a session PDU in accordance with a procedure (4100) for releasing an N2 and deactivating a session PDU. Method (4200) may be performed by AMF 218. Method (4200) includes AMF 218 configured to receive a release RRC notification message (4102). The AMF 218 then sends an N2 release notification message (4104) to the SMF 220. The AMF 218 then receives an N2 release notification confirmation message (4110) from the SMF 220. The AMF then sends an N2 release request message (4112) to the (R)AN 204. The AMF then 218 receives an N2 release confirmation message (4114) from (R)AN 204. Other steps may be added to the method (4200).

FIG. 43 illustrates in a flowchart another example of a method (4300) for disconnecting an N2 connection and deactivating a session PDU in accordance with an N2 release and deactivating session PDU procedure (4100). The method (4300) may be performed by the SMF 220. The method (4300) comprises an SMF 220 configured to receive an N2 release notification message (4104) from the AMF 218. The SMF 220 then sends an N3 release request message (4106) to the UPF 212. The SMF 220 then receives an N3 release response message (4108) from the UPF 212. The SMF 220 then sends an N2 release notification confirmation message (4110) (4110) to the AMF 218.

The procedure may be used to release the N2 connection when the UE 202 enters the CM-IDLE state, or to deactivate PDU sessions when the (R)AN 204 initiates selective session PDU deactivation. 44 illustrates, in a message processing flow diagram, an example of a PDU session deactivation procedure (4400) in accordance with an embodiment of the present invention. UE 202 and (R)AN 204 may perform an RRC release procedure (600A) or an RRC reconfiguration procedure (600B). If the RRC connection is disconnected, then the (R)AN 204 may interact with the UE to release the RRC signaling connection (procedure 600A). The UE enters the CM-IDLE state and all PDU sessions are deactivated. If some PDU sessions are deactivated, then the (R)AN 204 may interact with the UE 202 to release DRBs belonging to the deactivated PDU sessions (procedure 600B). UE 202 may be aware that releasing all DRBs belonging to a PDU session implies deactivation of the corresponding PDU sessions. The (R)AN may send (message N2) a PDU session deactivation request (4402) to the AMF 218. Message (4402) may include the PDU session identifier(s) and a reason code. The reason code may be an RRC message with a reason such as O&M interference, UE inactivity, and so on. The reason code may also be session inactive PDU. In case of RRC release, the PDU session deactivation request does not include the PDU session identifier. In case of PDU session inactivity, PDU session deactivation request (4402) may include a list of PDU session identifiers. It should be noted that, in certain scenarios, step (600A or 600B) may be initiated before or in parallel with step (4402).

The AMF 218 may then generate (message N11) one or more PDU session deactivation request(s) (4404) and send them to the SMF(s) 220 that serve the PDU sessions to be deactivated (4404). Message (4104) may include a UE ID to identify the UE (such as a temporary UE ID or SUPI), a list of PDU session IDs to be deactivated, and a reason code. The SMF 220 may then send (message N4) an N3 release request (4106) to the UPF(s) 212. The message (4106) may include a UE identifier (such as a temporary UE identifier or SUPI) to identify the UE 204 and a session ID PDU. UPF 212 may provide N3 tunnel information (ie, (R) AN IP address and tunnel ID) in the context of the UE PDU session for PDU sessions to be deactivated. The UPF 212 may send (message N4) an N3 release response message (4108) to the SMF 220 confirming the release of the N3 tunnel information.

The SMF 220 may then send (message N11) a session PDU deactivation response message (4406) to the AMF 218 to acknowledge the release of the N3 tunnel information to the UPF(s) 212. The AMF 218 may then collect all responses from the SMF 220 that were requested for deactivation PDU sessions (at step (4404)). Once all responses from the SMF 220 have been collected, the AMF 218 may send (message N2) a session PDU connection release request (4408) to the (R)AN 204. In the case of the (R)AN 204 or AMF 218, after initiating the deactivation of all session PDUs, the message ( 4408) may include an indication to release the UE context (ie, all information related to the UE 204, including N3 tunnel information and N2 connection). In case of selective PDU session deactivation, message (4408) may include a list of PDU session identifiers.

If step (600A or 600B) was not previously performed in the first step of procedure (4400), the (R)AN 204 and UE 202 may perform a release RRC procedure (600A) or an RRC reconfiguration procedure (600B). If the message at step (4408) included an indication to release the UE context, then the (R)AN 204 may request the UE 202 to release the RRC connection (600A). UE 202 enters the CM-IDLE state and all PDU sessions at UE 202 may be deactivated. Upon receiving the RRC connection release acknowledgment from the UE 202, the (R)AN 204 deletes the UE context. If the message in step (4408) included an indication to deactivate the PDU session list, the (R)AN 204 and the UE perform a DRB release procedure (600B). The UE knows that releasing all DRBs belonging to a session PDU implies deactivation of the corresponding session PDU. Upon receiving an acknowledgment to release DRBs from UE 202, (R)AN 204 removes the UE PDU session context from the deactivated session PDUs.

The (R)AN 204 may then send (message N2) a session PDU connection release response message (4410) to the AMF 218. The message (4410) provides an acknowledgment for step (4408). If the message in step (4408) indicates a UE context release, AMF 218 may set the CM-IDLE state on the UE context and release the N2 UE connection. The AMF 218 may then create (message N11) a session PDU deactivate confirmation message (4412) and send it to SMF(s) 220 to confirm the deactivation of PDU sessions at the (R)AN 204.

FIG. 45 illustrates in flowchart an example of a PDU session deactivation method (4500) according to a PDU session deactivation procedure (4400). Method (4500) may be performed by AMF 218. Method (4500) comprises AMF 218 configured to receive a session PDU deactivate request message (4402) from an (R)AN204. AMF 218 may then send a session PDU deactivate request message (4404) to SMF 220. AMF 218 may then receive a session PDU deactivate response message (4406) (4406) from SMF 220. AMF 218 may then send a session connection release message (4408) PDU at the (R)AN 204. The AMF 218 may then receive the session PDU connection release response message(s) from the (R)AN 204. The AMF 218 may then send a session PDU deactivation confirmation message (4412) to the SMF 220. To method (4500 ) other steps can be added.

FIG. 46 illustrates in a flowchart another example of a PDU session deactivation method (4600) according to a PDU session deactivation procedure (4400). Method (4600) may be performed by SMF 220. Method (4600) comprises SMF 220 configured to receive session PDU deactivate request message (4404) from AMF 218. SMF 220 then sends N3 release request message (4106) to UPF 212. The SMF 220 then receives the N3 Release Response Message (4108) from the UPF 212. The SMF 220 then sends a PDU Session Deactivate Response Message (4406) to the AMF 218. The SMF 220 then receives a PDU Session Deactivate Acknowledge Message (4412) from the AMF 218. To the method (4600) other methods may be added.

The service request procedure may be used by the 5G UE 204 in the CM-IDLE state to request the establishment of a secure connection with the AMF 218. The UE 202 in the CM IDLE state may initiate the service request procedure in the following order: send uplink signaling messages, user data, or a response to network paging request. Upon receipt of the service request message, the AMF 218 may perform authentication and the AMF 218 may perform a security procedure. After establishing a secure signaling connection with the AMF 218, the UE 202 or the network may send signaling messages, such as establishing a PDU session from the UE 202 to the network, or the SMF 220 through the AMF 218 may initiate the user plane to establish resources for the PDU sessions requested by the network and/or specified in the service request message. When UE 202 is in the CM-CONNECTED state, UE 202 may use a different SM procedure to request user plane resource establishment for idle PDU sessions.

FIG. 47 illustrates in a message processing flowchart another example of a Session-ACTIVE state transition procedure (4700) in accordance with an embodiment of the present invention. UE 202 may send an SM session activation request (4702) to SMF 220 in message N1. Message (4702) may include PDU session ID(s) to be activated. Message (4702) may not include a list of PDU sessions available at UE 202. A list of PDU sessions available at UE 202 may be included if UE 202 released some PDU sessions but did not inform SMF 220. (R) The AN 204 may forward the N1 SM session activation message to the AMF 218 via the N2 interface. The (R)AN 204 does not need to have the UE 202's location, RAT type, and 5G UE temporary ID in the UF 208. The AMF 218 may select the SMF 220 based on the session ID of the PDU and forward the SM session activation request (4704) to the serving SMF 220 via the N11 interface. The forwarded message (4704) may include a UE ID for identifying the UE, such as a temporary 5G UE ID or SUPI, and PDU session ID(s).

The SMF 220 may use the "Message Transfer" service provided by the AMF 218 to send an N11 message (4706) that contains one N2 SM information to be sent to the (R)AN 204 and one N1 SM Session Activation Confirm NAS message to send to the UE. through the N11 interface. The N11 message may include a UE ID to identify the UE (eg, a temporary 5G UE ID or SUPI) and PDU session ID(s). The N2 information message SM may include a PDU session ID(s) and a UE PDU session context (QoS profile and N3 tunnel termination information UPF 212 (UPF IP address and tunnel endpoint identifier)). The AMF 218 may then read the UE ID (such as a 5G temporary ID or SUPI) and the PDU session ID(s) to find the (R)AN 204. The AMF 218 transmits the content of the N11 message (4706) which contains the N2 SM information and the NAS acknowledgment message. the N1 SM session activation received from the SMF in N2 message 4708 to the (R)AN on the N2 interface. The (R)AN 204 and UE 202 may then perform a RRC connection reconfiguration procedure (600B) according to the QoS profile for all QoS flows of the activated session PDU provided in the N2 SM information. If the (R)AN 204 can support the PDU session, the RRC connection reconfiguration message sent from the AN 204 to the UE 202 can indicate the radio resource allocation for the PDU session; and (R)AN 204 forwards the N1 SM Session Activation Confirm message provided in message (4708) to the UE by the NAS. After setting up the radio resources in the user plane, the uplink data from the UE 202 can now be sent (4710) to the RAN 204. The 5G RAN 204 can send the uplink data (4710) to the UPF address 212 and the tunnel ID provided in step (4706) .

Then (R)AN 204 may send (message N2) N3 information (4712) (R)AN to SMF 220 via AMF 218. Message (4712) may include PDU session ID(s), RAT type, list of received QoS flows and a list of rejected QoS flows for the corresponding activated session PDU, and (R) AN N3 tunnel information ((R) AN IP address and tunnel ID). The AMF 218 then transmits (message N11) N3(R)AN information (4714) to the SMF 220 by reading the PDU session identifier(s) over the N11 interface. Message (4714) may include a UE identifier for identifying the UE (such as a 5G temporary identifier or SUPI), PDU session identifier(s), RAT type, a list of received QoS flows, and a list of rejected QoS flows for the corresponding activated session PDU, and N3( R) AN tunnel information ((R) AN IP address and tunnel ID). Possibly, if dynamic PCC is deployed, then SMF 220 may initiate an IP-CAN session change (4716) and provide new UE 202 location information to PCF 222.

In another embodiment, the (R)AN 204 may include the SMF identifier in the message (4712). The AMF 218 may read the SMF ID rather than the PDUS session ID(s) to forward the (N2-message) N3(R)AN information (4714) to the SMF 220.

If, at step (4712), the AN node 204 notifies the successful completion of the session activation, then the SMF 220 requests the UPF 212 to update the session context of the UE PDU. In this case, the SMF 220 may send an N4 message update request (4718) to the UPF 212 to update the N3 tunnel information of the (R)AN 204. The message (4718) may include an identifier to identify the UE (such as a 5G temporary identifier or SUPI), PDU session identifier(s) and (R) AN tunnel information (IP address (R) AN 204 and tunnel endpoint identifier N3). The UPF 212 may then send an N4 session update response (4720) to the SMF 220 to acknowledge completion of the session update request.

FIG. 48 illustrates in flowchart an example of a session transition method (4800) in accordance with the Session-ACTIVE state transition procedure (4700) of FIG. 47. The method (4800) may be performed by the AMF 218. The method (4800) comprises an AMF 218 configured to receive an SM session activation request message (4702) from the UE 202 via the AN 204. The AMF 218 then sends a session activation request message (4704) SM to SMF 220. The AMF 218 then receives an N11 message containing the N2 SM information and an N1 SM session activation confirmation (4706) from the SMF 220. The AMF 218 then sends an N2 message containing the N2 SM information and an activation confirmation (4708) to the AN 204. Then AMF 218 receives AN N3(R) information message (4712) from AN 204. AMF 218 then sends N3(R)AN information (4714) to SMF 220. Other methods may be added to method (4800).

FIG. 49 illustrates in flowchart an example of a session transition method (4900) in accordance with the Session-ACTIVE state transition procedure (4700) of FIG. 47. Method (4900) may be performed by SMF 220. Method (4900) comprises SMF 220 configured to receive an SM session activation request message (4704) from AMF 218. SMF 220 then sends N11 a message containing SM information N2 and N1 SM session activation confirmation message (4706) at AMF 218. The SMF 220 then receives the N3(R)AN information message (4714) from the AMF 218. The SMF 220 can then optionally perform an IP-CAN session change (4716) with the PCF 222. The SMF then 220 sends a session update request message (4718) to UPF 212. SMF 220 then receives a session update response message (4720) from UPF 212. Other steps may be added to the method (4900).

FIG. 50 illustrates in a message processing flowchart an example of a service request procedure (5000) according to an embodiment of the present invention. UE 202 may send to (R)AN 204 a request (5002) for NAS MM services. Message (5002) may include PDU session ID(s), security parameters, and PDU session state. The UE 202 may send the NAS a service request message to the AMF 218 encapsulated in an RRC message to the RAN 204.

If UE 202 is in the CM-IDLE state, then UE202 may send a NAS MM service request message (5002). UE 202 may include a 5G temporary ID in the RRC message (5002) between UE 202 and (R) AN 204. (R) AN 204 may route the NAS MM service request message to the correct AMF 218 according to the 5G temporary ID. If UE 204 is in the CM-IDLE state, then UE 202 may send a NAS MM service request message (5002). UE 202 may include the security parameters in the NAS message (5002). The status of the session PDU may be known. Alternatively, the session PDU status may only be contained if UE 202 has released some session PDUs but has not informed SMF 220.

If the UE 202 is in the CM-CONNECTED state, the UE 202 may send a NAS MM service request message (5002). The MM service request message (5002) may be encrypted and integrity protected. The message (5002) may include the session ID(s) of the PDUs to be activated. The status of the session PDU may be known. Alternatively, the session PDU status may only be contained if UE 202 has released some session PDUs but has not informed SMF 220.

When initiated by the UE 202 for user data, the UE 202 may include the PDU session ID(s) in the NAS service request message (5002) to indicate the PDU session that the UE 202 selects to activate. If UE 202 is initiated for signaling only, UE 202 may not send any PDU session ID. When initiating this procedure (5000) for a paging response, if the UE 202 needs to activate the PDU session(s), it includes the PDU session ID(s) in the NAS MM service request message (5002) to indicate the PDU session that the UE 202 needs to be activated. Otherwise, UE 202 does not need to include any PDU session identifier. The PDU session state may indicate PDU sessions available at UE 202.

The (R)AN 204 may then send a NAS MM service request message (5004) to the N2 AMF 218. The message (5004) may include a 5G temporary identifier, location information, RAT type, and RRC establishment reason. If the AMF 218 cannot process the service request (5004), it will reject it.

If the UE 202 is in the CM-IDLE state, then the 5G temporary identifier may be received in the RRC procedure. RAN 204 may select AMF 218 according to the temporary identifier. The location and RAT type information is related to the cell in which the UE 202 is located.

If the UE is in the CM-CONNECTED state, the (R)AN 204 forwards a NAS MM service request message to the AMF 218 without adding the 5G temporary ID, location information, RAT type, or RRC establishment reason.

Based on the state of the PDU session, AMF 218 may initiate a PDU session release procedure if the PDU session is not available at UE 202.

Then, if the service request (5004) was not sent with integrity protection, or an integrity protection failure is indicated, AMF 218 may initiate a NAS authentication/security procedure (5006) with UE 202 and AUSF 214. If UE 202 is initiated to establish a signaling connection, after security exchange, UE 202 may send uplink signals and the rest of this procedure is not performed. If the UE is in the CM-CONNECTED state, step (5006) is skipped.

AMF 218 may then conditionally send SMF 220 N11 a message (5008) that includes a UE identifier (SUPI) and PDU session ID(s). If the NAS MM service request message (5004) includes the PDU session ID(s) or this procedure is triggered by the SMF 220, the AMF 218 may send an N11 message (5008) to the SMF(s) 220 associated with the PDU session ID(s). The SMF 220 may then conditionally send to the N11 AMF 218 a message (5010) that includes the N2 SM information (QoS profile, N3 CN tunnel information) and the NAS SM session activation confirmation (with PDU session IDs) to the AMF 218. After receiving N11 messages (5008), each SMF 220 may send an N11 message (5010) to AMF 218 to set up user plane(s) for PDU sessions. The N2 SM information may include information that the AMF 218 may provide to the RAN 204. The NAS SM session activation confirmation message may include information that the AMF 218 may provide to the UE 202. The SMF 220 may use the message passing service provided by by AMF 218 to send N2 SM information and activate the SM NAS session.

The AMF 218 may then conditionally send to the (R)AN 204 N2 a request (5012) that includes the N2 SM information and the NAS SM session activation confirmation received from the SMF 220, the security context, the AMF signaling connection identifier, the handover restriction list, and the MM NAS service confirmation. If the service request (5000) was initiated by the UE 202 in the CM-IDLE state, the AMF 218 may include a security context, an AMF signaling connection identifier, and a handover constraint list in the N2 request (5012). RAN 204 may store a security context, an AMF signaling connection identifier, QoS information for QoS flows of activated session PDUs, and N3 tunnel identifiers in the context of the UE RAN. If the service request (5000) was initiated when the UE 202 is in the CM-CONNECTED state, the AMF 218 may send the N2 SM information (QoS profile, N3 CN tunnel information) and the NAS SM SM session activation confirmation to the (R)AN 204, without adding a security context, an AMF signaling connection identifier, and a list of handover restrictions or MM NAS service confirmation. If there are multiple session PDUs that include multiple SMFs 220, AMF 218 may wait for responses from all SMFs 220 in step (5010) until it sends an N2 request (5012) to RAN 204. Receiving a NAS MM service may include a PDU session status in AMF 218. If this procedure (5000) is triggered for signaling only, a NAS MM service acknowledgment may be sent to UE 202 after step (5006).

Then, (R)AN 204 and UE 202 may perform RRC connection reconfiguration (600B) depending on the QoS information for all QoS flows of activated PDU sessions. If the service request procedure (5000) was initiated by the UE 202 in the CM-IDLE state, user plane security may be established at this step (600A). The RAN 204 may forward the NAS MM service acknowledgment and the NAS SM session activation acknowledgment to the UE 202. If the service request procedure (5000) was initiated by the UE in the CM-IDLE state, the UE 202 may delete the session context PDUs that are not available on the 5G CN.

After the user plane radio resources are established, the uplink data from the UE may be forwarded (5014) to the RAN 204. The 5G RAN 204 may send the uplink data (5014) to the UPF address 212 and the provided tunnel ID in step (5008) . The (R)AN 204 may then conditionally send to AMF 218 an N2 request ACK (5016) that includes N2 SM information (RAN tunnel information, a list of received QoS flows for each of the activated PDU sessions, and a list of rejected QoS flows for each of the activated PDU sessions).

The AMF 218 may then conditionally send to the N11 SMF 220 a message (5018) that includes the N2 SM information (RAN tunnel information), the RAT type, the list of received QoS flows, and the list of rejected QoS flows for each received PDU session in the SMF 220. If the time zone of the UE 202 has changed from the last reported time zone of the UE, the AMF 218 may contain the UE time zone IE in this message (5018). For denied QoS flows, SMF 220 may send a NAS SM release QoS flow request to UE 202. Message (5018) may include a PDU session ID(s) and a list of rejected QoS flows for each PDU session. UE 202 may then acknowledge the release of the rejected QoS flows. Possibly, if a dynamic PCC is deployed, the SMF 220 may initiate a change (4716) to the IP-CAN session and provide the new location information to the PCF 222.

SMF 220 may then conditionally send to UPF 212 an N4 session update request (4718) that includes RAN tunnel information and a list of received QoS flows. If the user plane needs to be set up or changed, SMF 220 may initiate an N4 session change procedure and provide RAN tunnel information. The UPF 212 may then conditionally send an N4 session update response (4720) to the SMF 220. The SMF 220 may then conditionally send an ACK message to the AMF 218 N11.

When the network needs to signal (e.g., N1 signaling at UE 202, SMS with mobile termination, PDU session radio resource establishment for delivering user data data with terminal mobile station) with UE 202 in 5G CM-IDLE state or 5G CM-CONNECTED state the network may initiate a network-initiated service request procedure. If the UE 202 is in the 5G CM-IDLE state, the network initiated service request procedure may send a paging request to the (R)AN 204/UE 202. The paging request starts the service request procedure in the UE 202. The UE 202 is in 5G CM-IDLE. CONNECTED, no paging request will be sent to (R)AN 204/UE 202.

FIG. 51 illustrates in a message processing flowchart an example of a service request procedure (5100) according to an embodiment of the present invention. When UPF 212 receives downlink data in a PDU session and no tunnel information of AN 204 for the PDU session is stored in UPF 212, UPF 212 may buffer the downlink data. The UPF 212 may then send a data notification (5104) to the SMF 220 that includes the PDU's session ID and priority. Upon arrival of the first downlink data packet, UPF 212 may send a data notification message (5104) to SMF 220. If UPF 212 receives additional downlink data packets for a QoS flow in the same PDU session with the same or lower priority than the first data notification (5104) has been sent, the UPF 212 may buffer these downlink data packets and does not send a new data notification. If the paging policy demarcation feature is supported by UPF 212 and if enabled by SMF 220 for this N4 session, UPF 212 may also use DSCP to the TOS (IPv4)/TC (IPv6) value from the IP header of the downlink data packet. The SMF 220 may send a data notification acknowledgment (5106) to the UPF 212 (ACK).

The SMF 220 may then send an N11 message (5108) to the AMF 218 including the persistent UE ID, PDU session ID, and priority. SMF 220 identifies AMF 218 and sends N11 a message (5108) including a persistent UE ID, PDU session ID, priority, and paging policy indication. The priority and session ID of the PDU may be set according to step (5104). If the SMF 220, while waiting for user plane establishment, receives an additional data notification message (5104) with a higher priority than the first N11 message (5108) sent, the SMF 220 may send a new N11 message (5108), indicating the higher priority AMF 218 and the session ID of the PDU. If the SMF 220, while waiting for the user plane to be established, receives a different N11 message from the AMF 218 than the one sent by the N11 message (5108), the SMF 220 may resend the N11 message (5108) only to the new AMF 218 from which it received the N11 message . If the registration procedure with AMF change 218 is performed when the previous AMF 218 receives the N11 message (5108), the previous AMF 218 may reject the N11 message indicating that the N11 message has been temporarily rejected. With support for paging policy differentiation, the SMF 220 may indicate in the N11 message (5108) that the paging policy indication refers to the downlink data that triggered the data notification message. It should be noted that the AMF 218 may receive request message(s) from other network functions, resulting in signaling towards the UE 202/RAN 204, such as a network initiated disconnect and SMF 220 initiating a PDU session change. If UE 202 is in the 5G CM-CONNECTED state and AMF 218 delivers only N1 messages to UE 202, the flow continues at step (5116) as shown below.

AMF 218 may respond to SMF 220. If UE 202 is in the 5G CM-IDLE state and AMF 218 believes that UE 202 is unpaging, AMF 218 may send a response (5110) to SMF 220, with a reason code and information. SMF 220 may deliver this additional information to UPF 212. If UE 202 is in 5G CM-CONNECTED state, AMF 218 may send a response (5110) to SMF 220 indicating that UE 202 is in 5G CM-CONNECTED mode, and then SMF 220 may perform steps (5010) - (5020) in the UE-initiated service request procedure (5000) to establish the radio resources and tunnel N3 of the session PDU. The rest of this procedure is omitted.

If the UE 202 is registered with the AMF 218 and is in the 5G CM-IDLE, but is deemed reachable for paging, the AMF 218 may send a paging message (5112) including the NAS ID for the paging, the registration area, the DRX paging length, and an indication paging priority to each (R)AN 204 belonging to the registration area(s) in which the UE 202 is registered. With support for paging policy differentiation, the AMF 218 may include an indication of the paging policy in the paging request message (5112). Paging strategies may be configured in AMF 218 for various combinations of DNNs, paging policy indication, PDU session identifiers from SMF 220 when available (see clause 4.9), and other PDU session context information identified by the PDU session identifier received in N11 message. The paging strategies may include a paging retransmission scheme (eg, how often the paging is repeated or at what time interval); determining whether to send a paging message (R) AN 204 during certain AMF 218 high load conditions; whether to apply sub-area based paging (eg, first paging in the last known cell ID or TA and retransmission in all registered TAs). AMF 218 and (R)AN 204 may support additional paging optimization to reduce signaling and network resource load used to successfully page UE 202 in one or more of the following ways: AMF 218 implements specific paging strategies (e.g., paging message call N2 is sent to the nodes (R) AN 204, which served the UE 202 last); AMF 218 based on the recommended RAN cells and nodes provided by the (R)AN 204 when migrating to CN-IDLE. The AMF 218 may take into account the portion of the (R)AN 204 related to this portion of this information to determine the (R)AN 204 to be searched, and may provide the recommended cell information in the N2 paging message to each of the (R)AN 204 ; and by the (R)AN 204 considering the paging attempt count information provided by the AMF 218 when paging. If the UE radio capability for paging information is available in AMF 218, AMF 218 adds the UE radio capability for paging information in the paging message N2 to the (R) ANs 204. If the recommended cells and (R) ANs 204 information for paging available in AMF 218, AMF 218 may take this information into account to determine which (R)AN 204 to paging and, when paging (R)AN 204 is established, AMF 218 may transparently send recommended cell information to (R)AN 204. AMF 218 may add information about the number of paging attempts to the paging message (5112) (messages) N2. The information about the number of paging attempts may be the same for all (R) ANs 204 selected by AMF 218 for paging.

Then, the (R)AN node 204 may conditionally paging (5114) the UE 202. If the (R)AN nodes 204 receive paging messages (5112) from the AMF 218, the UE 202 call (5224) via the (R)AN node 204 When the UE 202 is in the 5G CM-IDLE state, after receiving a paging request, the UE 202 may initiate a UE initiated service request procedure (5000). In step (5008), the AMF 218 may send the N11 message to both the SMF(s) 220 associated with the PDU session identified by the PDU session ID(s) in the NAS MM Service Request message and the SMF(s) 220 from which the N11 is received. message in step (5006). AMF 218 controls the timer paging procedure. If AMF 218 does not receive a response from UE 202 to the paging request message (5224), then it may retry the paging in accordance with any applicable paging strategy described in step (5108). If AMF 218 does not receive a response from UE 202 after this repaging procedure, AMF 218 may use an N11 message to notify SMF 220 of paging failure if paging was initiated by N11 message, if AMF 218 does not know the current MM procedure that prevents response of the UE 202 (that is, the AMF 218 receives a context request message indicating that the UE 202 is performing a TAU procedure with the other AMF 218. When a downlink data notification rejection message is received, the SMF 220 informs the UPF 212 and the UPF 212 deletes the buffered packet (packets).The UPF 212 then transmits the buffered downlink data (5116) to the UE 202 via the (R)AN node 204 that performed the service request procedure.The network may send downlink signaling (5116) if the procedure is initiated due to request from other network entities described in step (5108).

FIG. 52A illustrates in a state diagram an example of a session management state model 5200A in UE 202 in accordance with an embodiment of the present invention. The session state may transition from the "Session-IDLE" state 610A to the "Session-ACTIVE" state 620A when a service request is received from the AMF 218. The session state of the UE 202 may transition from the "Session-ACTIVE" state 620A to the "Session-IDLE" state 610A ”, when RRC is released.

FIG. 52A further illustrates in a state diagram an example of a session control state model 5200A in UE 202 in accordance with embodiments of the present invention. Upon receipt of a new session PDU request, the PDU session state is generated as part of the UE PDU session context, and the PDU session state is set to the "Session-ACTIVE" state 620A. When the RRC is released, the session state of the PDU is set to the "Session-IDLE" state 610A. When the UE 202 sends a service request to transmit uplink data or to receive downlink data, and the UE 204 receives a service request receive message from the AMF 218, and the session state of the PDU is set to the "Session-ACTIVE" state 620A.

FIG. 52B illustrates in a state diagram an example of a session management state model 5200B in AMF 218 and/or SMF 220 in accordance with an embodiment of the present invention. The session state may transition from the "Session-IDLE" state 610B to the "Session-ACTIVE" state 620B after session activation is completed. The session state may transition from the "Session-ACTIVE" state 620B to the "Session-IDLE" state 610B when the N2 connection is released.

The session state may be used to indicate that the UE 202 has activated a PDU session to send and receive data. The two session states include the "Session-ACTIVE" state and the "Session-IDLE" state. UE 202 serving AMF 218 and serving SMF 220 maintain session state.

When the session PDU is in the "Session-IDLE" state, the UP data connection between the UE 202 and the UPF 212 terminating the N3 connection is not established. UE 202 may not send or receive data. (R)AN 204 may not have a PDU session context. The UPF 212 terminating N3 connection may have a UE PDU session context, but without the (R)AN 204 N3 connection information (ie, without the (R)AN 204 address and N3 tunnel endpoint identifier). SMF 220 may store UE PDU session context information related to SMF 220 but without (R)AN information 204. AMF 218 may store all UE PDU session context information related to AMF 218.

When the session PDU is in the "Session-ACTIVE" state, UE 202 can send and receive data. The air interface Uu between UE 202 and (R)AN 204 may be established. The N3 connection can be established when the PDU session is activated. UE 202 may have all PDU session context information including DRB information. AMF 218 may store all UE PDU session context information associated with AMF 218. SMF 220 may store all UE PDU session context information associated with SMF 220. (R)AN 204 may monitor PDU session data activity. The last data activity time information element in the session context of the PDU at the (R)AN 204 may be used to record the last time the UE 202 had data activity. During the handover procedure, this information element may be passed to the target (R)AN 204 t and not modified as part of the UE context. Each session context PDU may also have an inactive session timer. During the handover procedure, the N3 (R)AN 204 connection information on the N3 connection of the UPF 212 terminating the connection may be updated if the session PDU has data activity.

Another parameter, "status flag N3", in the session context of the UE PDU in the (R) AN 204 may be used to indicate whether the information of the (R) AN 204 in the UPF 212 is updated or not. Status flag N3 in (R)AN 204 may have two values: N3_AT_UPF_UPDATED and N3_NOT_AT_UPF_UPDATED. During the handover procedure, the target (R) AN 204t compares the duration that the UE 202 has no data activity (from the current time and the last data activity time parameter) and the idle session timer parameter. If the duration for which UE 202 has no data activity is longer, then the target (R) AN 204t may deduce that UE 202 has no data activity. Otherwise, target (R) AN 204t may infer that UE 202 has data activity. The N3 AN (R) Tunnel information on the N3 UPF terminating connection is only updated if the session PDU has data activity. When PDU session information is sent to the (R) AN 204 during the session establishment procedure and the session request procedure, the N3 state flag in the (R) AN 204 may be set to N3_AT_UPF_UPDATED. The N3 status flag in the (R)AN 204 may be changed from N3_AT_UPF_UPDATED to N3_AT_UPF_NOT_UPDATED during the target (R)AN 204t handover procedure if the session PDU has no data activity in the source (R)AN 204s. The N3 status flag in the (R)AN 204 may be changed from N3_AT_UPF_NOT_UPDATED to N3_AT_UPF_UPDATED if the session PDU is processing data.

During the handover process, the target (R)AN 204t may send the AMF 218 a list of session PDUs that are considered to have no data activity marked by the target (R)AN 204t in the path switch request. The target (R)AN 204t may include a different list of PDU sessions that have an N3 status flag like N3_AT_UPF_NOT_UPDATED already set by the source (R)AN 204s. For each PDU session, target RAN 204t may include (R)AN 204 PDU session information such as (R)AN type, (R)AN N3 address, and (R)AN N3 tunnel endpoint ID, and a list of received streams. QoS and another list of rejected QoS flows. AMF 218 may store (R)AN information. The AMF 218 may inform the appropriate serving SMF 220 of the session ID(s) of the PDUs that do not have data activity marked by the target (R) AN 204t in the path switch request. The SMF 220 may send a message to the serving UPF 212 to release the (R)AN N3 tunnel information.

AMF 218 and SMF 220 may have an N3 status flag as part of their UE's PDU session context. When a PDU session is established or activated, the N3 status flag in AMF 218 and SMF 220 may be set to N3_AT_UPF_UPDATED. The N3 status flag in AMF 218 and SMF 220 may be changed from N3_AT_UPF_UPDATED to N3_AT_UPF_NOT_UPDATED upon receipt of a message from the (R)AN 204 indicating that this session PDU has no data activity. Status flag N3 in AMF 218 and SMF 220 may be changed from N3_AT_UPF_NOT_UPDATED to N3_AT_UPF_UPDATED when UE 202 has data activity notified by UPF 212 or (R)AN 204.

Table 2 describes the session states "Sesssion-ACTIVE" and "Session-IDLE" for various network entities.

Table 2. Description of session state

• Network object • Session active • Session idle • UE (maintains session state) • Has the entire session context PDU including DRB information • Has the entire session context PDU without DRB information • (R)AN (does not maintain session state) • Has all session context PDU and DRB information • Does not have all session PDU context and DRB information • UPF (does not maintain session state) • Has the entire session context PDU • Has the entire session context PDU without (R)AN N3 connection information AMF (maintains session state) Has the entire session context PDU related to access and mobility control Has the entire session context PDU related to access and mobility control SMF (maintains session state) Has the entire session context PDU. However, depending on the N3 flag state, the SMF may not have (R)AN information such as (R)AN type and (R)AN N3 connection information if the N3 flag state is set to N3_AT_UPF_NOT_UPDATED. Has the entire context of the session PDU, without (R)AN information such as (R)AN type and (R)AN N3 connection information.

FIG. 52B further illustrates in a state diagram an example session management state model 5200B in AMF 218 and/or SMF 220 in accordance with embodiments of the present invention. When a new PDU session request is received, the PDU session state is set as part of the UE PDU session context in the AMF 218 and in the SMF 220, and the PDU session state is set to the "Session-ACTIVE" state 620A. When N2 is released, the session PDU state of all session PDUs in AMF 218 and SMF 220 transitions from "Session-ACTIVE" state 620A to "Session-IDLE" state 610A. Upon receipt of a service request by UE 202 including a session PDU activation request, the session PDU state of the requested session PDU transitions from the "Session-IDLE" state 610A to the "Session-ACTIVE" state 620A.

In 3GPP TS 23.502, clause 4.2.3.2 on UE-initiated service request in CM-IDLE state describes a UE-initiated service request in CM-IDLE state procedure. Step 5 of this procedure refers to the AMF 218 sending an N2 request message to the (R)AN 204. It should be noted that this message may include a monitor data activity flag in addition to the N2 SM information received from the SMF 220, security context, identifier AMF signaling connections, handover restriction list and MM NAS service confirmation. The (R)AN 204 stores the security context, the AMF signaling connection identifier, the QoS information for the QoS flows of activated PDU sessions, the N3 tunnel identifiers, and the monitor data activity flag in the UE RAN context.

Handover between NG(R)AN based on Xn can take place with and without relocation of UPF 212. Handover can be based on centralized deployment or local deployment. Separate call flows can be defined for roaming scenarios.

The AMF 218 analyzes the mobility pattern of the UE 202 and determines, based on the mobility pattern, whether to request (R)AN 204 to monitor individual session PDU data activity. If the AMF 218 requests the (R)AN 204 to monitor the data activity of individual session PDUs, then after the session PDU is established or activated, the (R)AN 204 records the last time the session PDU had data activity via a parameter, such as a parameter like "time of last data activity". During the handover procedure, the last data activity time parameter is passed to the target (R) AN 204t and is not changed as part of the UE PDU context. The target (R) AN 204t sends the session PDU data last activity time parameter to the list of session PDUs that require a path switch in the path switch request.

Alternatively, the AMF 218 may inform the SMF 220 of the mobility pattern of the UE 202 during the session establishment procedure. SMF 220 may then determine whether to monitor individual PDU session data activity. In this case, during the session establishment procedure, the SMF 220 requests the (R)AN 204 to monitor the activity of the session PDU data.

For each session PDU contained in the Path Switch Request, the SMF 220 decides whether or not to update the (R)AN tunnel information for the UPF 212 based on criteria. The criteria may include at least one of the following: UE 202 mobility pattern, PDU session type, length of time that UE 202 has no data activity, and whether there is another PDU session served by the same UPF 212. In the pattern mobility of UE 202 consider only the UE 202 requesting handover. The PDU session type may be stored as part of the PDU session attributes. The duration that the UE has no data activity is based on the last data activity time reported by (R)AN 204, in accordance with AMF instruction 218.

Each AMF 218 and SMF 220 have a parameter called "connection state N3" as part of their UE's session PDU context. The N3 connection state has two values: N3_CONNECTED and N3_DISCONNECTED. When a session PDU is established or activated, the N3 connection state in AMF 218 and SMF 220 is set to N3_CONNECTED. The session PDU connection state N3 at AMF 218 changes from N3_CONNECTED to N3_DISCONNECTED when AMF 218 receives a message from SMF 220 indicating that (R)AN information is not updated for this session PDU during the handover procedure. The connection state of the N3 session PDU in the SMF 220 changes from N3_CONNECTED to N3_DISCONNECTED when the SMF 220 decides not to update the UPF 212 with (R)AN information during the handover procedure. The N3 connection state in AMF 218 and SMF 220 changes from N3_DISCONNECTED to N3_CONNECTED when UE 202 has data activity notified by UPF 212 or (R)AN 204.

During the handover process, the target (R) AN 204t sends to the AMF 218 a list of session PDUs to be switched and to be released in a path switch request. The PDU sessions to be switched are PDU sessions that have N3 UPF tunnel information. For each session PDU to be switched, target RAN 204t includes a last data activity time parameter and target (R) AN information such as (R) AN type, (R) AN address, and (R) AN N3 tunnel endpoint identifier . AMF 218 stores type (R)AN. The AMF 218 informs the corresponding Serving SMF 220 of the session ID(s) of the PDU to be switched and released. For PDU sessions to be switched, SMF 220 determines whether or not to update (R)AN information for UPF 212. If SMF 220 decides to update (R)AN information for UPF 212, SMF 220 sends (R)AN N3 tunnel information to UPF 212 If the SMF 220 decides not to update the (R)AN information, the SMF 220 sends a request message to the UPF 212 to remove the (R)AN information of the N3 tunnel. SMF 220 informs AMF 218 of its determination whether or not to update (R)AN information in UPF 212. For PDU sessions where (R)AN information is updated in UPF 212, the N3 connection state in AMF 218 and SMF 220 are set to N3_CONNECTED. Otherwise, the N3 connection state in AMF 218 and SMF 220 is set to N3_DISCONNECTED. During the N2 release procedure, the AMF 218 sends an N2 release notification message to the SMF(s) 220 that are serving session PDUs that are in the "Session-ACTIVE" state and have the N3 connection state set to N3_CONNECTED.

FIG. 53 illustrates in a message processing flowchart an example of an Xn-based inter-NG RAN handover procedure (5300) without relocating the UPF 212 according to an embodiment of the present invention. This procedure (5300) may be used to handover the UE 202 from the source RAN 204 to the destination RAN 204t using Xn when the AMF 218 does not change and the SMF 220 decides to keep the existing UPF 212 (i.e., the UPF 212 that terminates the N3 interface in the base NG networks (NGC) Assumes an IP connection between the source UPF 212 and the target UPF 212.

The procedure (5300) includes preparing (5302) a handover and performing (5304) a handover. Performing (5304) handover includes forwarding data (5306) from the source RAN 204s to the target RAN 204t. The target RAN 204t can check if some PDU sessions having the N3 status flag, "N3_AT_UPF_UPDATED", but no data activity in the source RAN 204s, by reading the last data activity time parameter in the PDU session context. If the duration for which the PDU has no data activity is greater than the session inactivity timer parameter, the PDU session is considered to have no data activity. The target RAN 204t may send an N2 path switch request message (5308) to the AMF 218 to report that the UE 202 has moved to a new target cell and a list of PDU sessions to be switched or deleted, a list of PDU sessions that have no data activity marked by the target RAN 204t and a list of PDU sessions that have no data activity marked by the source RAN 204s. Depending on the type of the target cell, the target RAN 204t may include relevant information in this message (5308) for each PDU session, including the RAN type, the N3 RAN address, and the N3 tunnel endpoint identifier. If the target RAN 204t cannot support some of the QoS flows of the session PDU, the N2 Path Switch Request message (5308) may include a list of accepted QoS flows and a list of rejected QoS flows for that session PDU.

The AMF 218 may then send an N11 message (5310) to each SMF 220 associated with the PDU session lists received in the N2 path switch request (5308). For PDU sessions that require a path switch, upon receipt of the N11 message (5310), each of these SMFs 220 determines whether the existing UPF 212 can continue to serve the UE 202. If the existing UPF 212 cannot continue to serve the UE 202 and it is not a session anchor PDU steps (5608)-(5624) of FIG. 56 as described below are executed. Otherwise, the following of steps (5312) - (5318) of each of these SMFs 220 are performed if their existing UPFs 212 can continue to serve the UE 202. For PDU sessions that are in the list of PDU sessions not marked with data activity by the source RAN 204 and a list of PDU sessions having no data activity marked by target RAN 204t, AMF 218 may store RAN 204 information. For each PDU session in the list of PDU sessions having no data activity marked by target RAN 204t, AMF 218 may send an N11 message ( 5310) to SMF 220 to send the PDU session ID to notify that the PDU session has no data activity.

The SMF 220 may then initiate the release of session PDUs that are not requested by the target RAN 204t. For PDU sessions requested by target RAN 204t, SMF 220 may send an N4 session change request message (5312) (including RAN address, downlink user plane tunnel identifiers, received stream list, if any) to UPF 212. For Session PDUs where RAN 204 information needs to be released, SMF 220 may send an N4 session change request (5312) to UPF 212 for those PDU sessions. Message (5312) may indicate N3 RAN connection release information (ie, RAN address and tunnel ID for the downlink user plane). The UPF 212 then returns an N4 session change response message (5314) (including tunnel identifiers for uplink traffic) to the SMF 220 after the requested session PDUs are switched or changed. To aid the reordering function at target RAN 204t for PDU sessions requiring a path switch, UPF 212 may send one or more "end marker" (5316) packets on the previously used path immediately after the path switch. UPF 212 may start sending downlink packets (5318) to target RAN 204t. It is noted that step (5318) may occur at any time after receiving a session change response (5314) N4 in SMF 2200. In SMF 220, for PDU sessions with no data activity, the N3 flag state of these PDU sessions may be changed from N3_AT_UPF_UPDATED to N3_AT_UPF_NOT_UPDATED. SMF 220 may send an acknowledgment (5320) of N11 message (ACK) (including CN tunnel information) to AMF 212 for PDU sessions that have been successfully switched or changed.

Upon receiving a response to the N11 message (5320) from SMF 220, for PDU sessions not having data activity marked by target RAN 204t, AMF 218 may change the N3 status flag parameter of these PDU sessions from N3_AT_UPF_UPDATED to N3_AT_UPF_NOT_UPDATED. Once message response N11 (5320) is received from all SMFs 220, AMF 218 may aggregate the received CN tunnel information from these responses and send this aggregated information as part of the N2 SM information in the N2 path switch request ACK (5322) to target RAN 204t. If none of the requested PDU sessions were successfully switched, AMF 218 may send an N2 Path Switch Request Deny message to target RAN 204t. At the target RAN 204t, for PDU sessions not having data activity marked by the target RAN 204t, the state flag parameter N3 of these PDU sessions may be changed from N3_AT_UPF_UPDATED to N3_AT_UPF_NOT_UPDATED. By sending a resource release message (5324) to the source RAN 204, the target RAN 204t confirms the successful handover. The release of resources from the source RAN 204 is then initiated.

FIG. 53 further illustrates in a message processing flowchart an example of an Xn-based inter-NG(R)AN handover procedure (5300) without user plane function relocation and session deactivation according to embodiments of the present invention. Procedure (5300) provides an alternative solution that combines the handover procedure defined in clause 4.9.1.1 of TS 23.502 and session deactivation signaling messages.

This procedure (5300) is used when UE 202 is handed over from source RAN 204s to target RAN 204t using Xn when AMF 218 does not change and SMF 220 decides to keep the existing UPF 212. UPF 212 is the UPF terminated by the N3 interface in the NGC. An IP connection is assumed between the source UPF 212s and the target UPF 212t. When the PDU is set, SMF 220 sends to (R)AN 204 a timer parameter, eg, named "session inactivity timer". Source (R) AN 204s records the last time that the session PDU has data activity using the last data activity time parameter. The source (R) AN 204s sends the session inactivity timer parameter and the last data activity time parameter to the target (R)AN 204t as part of the session context of the UE PDU. If the session PDU has no data activity for a period longer than the session inactivity timer parameter, the target (R) AN 204t decides to initiate a session PDU deactivation procedure.

In the handover execution step, the target (R)AN 204t sends to the UE 202 an RRC signaling message that indicates whether sessions PDUs that are accepted, deactivated, or rejected are received. The target (R) AN 204t then informs the SMF 220 (via AMF 218) that the PDU sessions have been accepted, deactivated, or rejected. For PDU sessions that are received, the target (R)AN 204t includes (R)AN N3 tunnel information such as the (R)AN address and tunnel endpoint identifier. For PDU sessions that are received, SMF 220 requests UPF 212 to update (R)AN tunnel information. For PDU sessions that are deactivated, SMF 220 sends a message requesting UPF 212 to remove (R)AN tunnel information. For PDU sessions that are released, SMF 220 initiates a session PDU release procedure.

Target RAN 204t sends an N2 Path Switch Request message (5308) to AMF 218 that indicates that UE 202 has moved to a new target cell. The message (5308) includes a list of PDU sessions to be switched, deactivated, or deleted. Depending on the target cell type, the target RAN 204t includes other information in this message. The PDU sessions to be switched are PDU sessions having N3 tunnel information UPF. For each PDU session to be switched, the target (R) AN 204t includes a last data activity time parameter and (R) AN information (such as (R) AN address N3 and tunnel endpoint ID N3). If the target RAN 204t cannot support the QoS flow of the session PDU, the N2 path switch request message (5308) includes a list of accepted QoS flows and a list of rejected QoS flows for that session PDU.

The AMF sends an N11 message (5310) to each SMF 220 associated with the list of session PDUs received in the N2 Path Switch Request message (5308). For PDU sessions that require a path switch, upon receipt of the N11 message (5310), each of these SMFs 220 determines whether the existing UPF 212 can continue to serve the UE 202. If the existing UPF 212 cannot continue to serve the UE 202, and is not a PDU session anchor , perform steps 3-11 of clause 4.9.1.2 of TS 23.502. For each PDU session where a path switch is required, the SMF 220 determines whether to update the existing UPF 212 with the tunnel information (R) AN 204, in accordance with clause 5.6.X of TS 23.501.

SMF 220 initiates the release of session PDUs that are not requested by the target RAN 204t. For PDU sessions requested by target RAN 204t, SMF 220 sends N4 Session Change Request message (6408) to UPF 212. Message (5312) includes AN address (R), tunnel identifiers for downlink user plane, and list of received flows , If there are any. For PDU sessions to be deactivated, the (R)AN information does not need to be updated. The SMF 220 sends an N4 session change request message (5312) to the UPF 212 for these PDU sessions. Message (5312) indicates release (R) AN of N3 tunnel information such as (R) AN address and tunnel endpoint identifier for the downlink user plane. The UPF 212 returns an N4 session change response message (5314) to the SMF 220 after the requested session PDUs are switched or changed. Message (5314) includes tunnel identifiers for uplink traffic.

To assist the reordering function in target RAN 204t for PDU sessions requiring path switching, UPF 212 sends one or more "end marker" packets (5316) over the previously used path immediately after path switching. UPF 212 starts sending downlink packets to target RAN 204t. SMF 220 sends N11 an ACK message (5318) to AMF 218 for PDU sessions that have been successfully switched or deactivated. The message (5318) includes CN tunnel information and indicates whether the (R)AN N3 tunnel information has been updated (eg, if a path has been switched) or deleted (eg, if PDU sessions have been deactivated). In SMF 220, for session PDUs where (R)AN N3 tunnel information from UPF 212 is given, the session state is set to "Session-IDLE". It should be noted that step (5318) may occur at any time after the N4 session change response message (5314) is received in SMF 220.

In AMF 218, after N11 receives the ACK message, the session state of the deactivated session PDUs is set to "Session-IDLE". Once message response N11 (5318) is received from all SMFs 220, AMF 218 aggregates received CN tunnel information from these responses and sends this aggregated information as part of N2 SM information in N2 Path Switch Request ACK message (5320) to target 204t. The message (5320) includes an indication, for each PDU session, whether the UPF 212 is updated with (R)AN information. If none of the requested PDP sessions were successfully switched, AMF 218 sends an N2 switch request failure message to the target RAN 204t. At target RAN 204t, for PDU sessions where UPF 212 is not updated with (R)AN information, UPF N3 tunnel information is removed. By sending a resource release message (5322) to the source RAN 204, the target RAN 204t indicates a successful handover. The release of resources from the source RAN 204 is then initiated.

FIG. 53 further illustrates in the message processing flowchart an example of a handover procedure (5300) between NG(R)ANs based on Xn without relocating the UPF 212 according to an embodiment of the present invention. This procedure (5300) may be used to handover the UE 202 from the source (R) AN 204s to the destination RAN 204t using Xn when the AMF 218 does not change and the SMF 220 decides to keep the existing UPF 212 (e.g., UPF 212 that terminates the N3 interface in the NG core network (NGC)). Assume an IP connection between source UPF 212 and target UPF 212.

The procedure (5300) includes preparing (5302) a handover and performing (5304) a handover. Performing (5304) handover includes sending data (5306) from the source (R)AN 204s to the target (R)AN 204t. Target (R)AN 204t sends an N2 Path Switch Request message (5308) to AMF 218 that includes an indication that UE 202 has moved to a new target cell and a list of PDU sessions to be switched or removed. Depending on the type of the target cell, the target (R)AN 204t includes in the message (5308) other information for each PDU session to be switched, including the last data activity time parameter and (R)AN information such as the address N3 (R )AN and tunnel endpoint ID N3. If the target (R)AN 204t cannot support the QoS flows of the session PDU, the N2 Path Switch Request message (5308) may include a list of accepted QoS flows and a list of rejected QoS flows for that session PDU.

The AMF 218 then sends an N11 message (5310) to each SMF 220 associated with the PDU session lists received in the N2 Path Switch Request message (5308). For PDU sessions that require a path switch, upon receipt of the N11 message (5310), each of these SMFs 220 determines whether the existing UPF 212 can continue to serve the UE 202. If the existing UPF 212 cannot continue to serve the UE 202, and is not a PDU session anchor , perform steps (5608) - (5624) of FIG. 56 as described below. Otherwise, each of these SMFs 220 performs the following steps (5312) - (5318) if their existing UPFs 212 can continue to serve the UE 202. For each PDU session where a path switch is required, the SMF 220 determines whether to update or not existing UPF 212 (R)AN tunnel information.

The SMF 220 then initiates the release of PDU sessions that are not requested by the target RAN 204t. For PDU sessions requested by target RAN 204t, SMF 220 sends an N4 session change request message (5312) to UPF 212. The message (5312) includes the (R)AN address, tunnel identifiers for the downlink user plane, and a list of received streams, If there are any. For PDU sessions in which the (R) AN 204 information does not need to be updated, the SMF 220 sends an N4 Session Change Request message (5312) to the UPF 212 for those PDU sessions. Message (5312) indicates transmission of N3 RAN tunnel information such as AN (R) address and tunnel endpoint identifier for the downlink user plane. The UPF 212 then returns an N4 session change response message (5314) to the SMF 220 after switching or changing the requested sessions PDUs. Message (5314) includes tunnel identifiers for uplink traffic. To assist the reordering function at the target (R) AN 204t for PDU sessions requiring a path switch, UPF 212 sends one or more "end marker" packets (5316) over the previously used path immediately after the path switch. UPF 212 may start sending downlink packets (5318) to target RAN 204t. It should be noted that step (5318) may occur at any time after receiving the N4 session change response message (5314) to the SMF 2200. The SMF 220 sends an N11 message acknowledgment (ACK) message (5318) to the AMF 212 for PDUs that have been switched. or successfully changed. Message (5318) includes CN tunnel information. Message (5318) indicates whether the N3 AN (R) tunnel information has been updated (eg, path switch) or released (eg, path release). In SMF 220, for PDU sessions where N3(R)AN tunnel information is not updated in UPF 212, the N3 connection state parameter of these PDU sessions is changed from N3_CONNECTED to N3_DISCONNECTED.

At AMF 218, upon receipt of N11 ACK message (5318), the N3 connection state parameter for PDU sessions where SMF 220 does not update (R)AN information for UPF 212 changes from N3_CONNECTED to N3_DISCONNECTED. Once the N11 ACK message (5318) is received from all SMFs 220, the AMF 218 aggregates the received CN tunnel information from these responses and sends this aggregated information as part of the N2 SM information in the N2 Path Switch Request ACK (5320) to the target (R)AN 204t . The message (5320) includes an indication for each PDU session of whether the UPF 212 has been updated with (R)AN information. If none of the requested PDP sessions were successfully switched, the AMF 218 sends an N2 Path Switch Request Fail message to the target (R)AN 204t. At target (R)AN 204t, for PDU sessions where UPF 212 is not updated with (R)AN information, UPF N3 tunnel information is removed. By sending a resource release message (5322) to the source (R)AN 204s, the target (R)AN 204t confirms the success of the handover. Releasing resources from the original (R) AN 204 is then initiated.

FIG. 53 further illustrates, in a message processing flowchart, an example of an Xn-based inter-NG RAN handover procedure (5300) without moving a user plane function, in accordance with embodiments of the present invention. Target (R)AN 204 may send an N2 Path Switch Request message (5308) to AMF 218 to report that UE 202 has moved to a new target cell and provide a list of PDU sessions to be switched. Depending on the target cell type, the target (R)AN 204t may pad the message with appropriate information. For each to be switched to the target (R) AN 204t, the N2 path switch request message (5308) may include a list of received QoS flows.

The AMF 218 may then send the N2 SM information using the N11 message (5310) to each SMF 220 associated with the list of PDU sessions and the list of received QoS flows for each PDU session received at the N2 path switch. Request (5308) for PDU sessions to be switched to the target (R)AN 204t, after receiving the N11 message, each of the SMFs 220 determines whether the existing UPF 212 can continue to serve the UE 202. If the existing UPF 212 cannot continue to serve the UE 202 , and is not a PDU session binding, then steps 3-11 of clause 4.9.1.2 of the TS are performed. 23.502. Otherwise, the following steps are performed. For an activated PDU session(s) that is not included in the N2 Path Switch Request message, the AMF 218 may send a separate request(s) to the corresponding SMF 220.

For PDU sessions requested by target (R)AN 204t, SMF 220 may send N4 session change request message (5312) to UPF 212. Message (5312) may include (R)AN address, tunnel identifiers for downlink user plane and a list of received QoS flows. For a session PDU that the target (R)AN 204t cannot support, SMF 220 may determine whether to unlock or keep, but not switch, that session PDU. If the session PDU is released, SMF 220 may initiate a session PDU release procedure. If the session PDU is retained but not to be switched, the SMF 220 may send an N4 session change request (5312) to the UPF 212 to set the "Session-AMBR" of the session PDU to zero.

For a PDU session to be switched, UPF 212 may return an N4 session change response message (5314) to SMF 212 after switching the requested PDU sessions. Message (5314) may include tunnel identifiers for uplink traffic. To keep the PDU session from switching, the UPF 212 may return an N4 session change response message (5314) accordingly.

For a session PDU to be switched to assist the reordering function at the target (R)AN 204t, UPF 212 may send one or more "end marker" packets (5316) on the previously used path after the path switch. UPF 212 may start sending downlink packets to target (R) AN 204t.

The SMF 220 may then send an ACK N11 message (5318) to the AMF 218 for the session PDUs that were successfully switched. Message (5318) may include CN tunnel information. To switch the PDU session, the SMF 220 may send an N11 ACK message (5318) to the (R)AN 204 via the AMF 218. The message (5318) may include an N2 SM message that includes a PDU session ID and sets "Session- AMBR" to 0. It should be noted that step (5318) may occur at any time after the session change response N4 is received in SMF 220.

Once the response to the N11 message (5318) is received from all SMFs 220, the AMF 218 may aggregate the received CN tunnel information from these responses and send the aggregated information as part of the N2 SM information in the N2 Path Switch Request ACK (5320) to the target (R)AN 204t. If none of the requested PDP sessions were successfully switched, AMF 218 may send an N2 Path Switch Request Reject message (5320) to the target (R) AN. By sending a resource release message (5322) to the source (R)AN 204s, the target (R)AN 204t can confirm the success of the handover. The resource release may then be initiated at the source (R)AN 204.

In an inter-NG-RAN handover with no Xn interface, source (R)AN (S-RAN) 204 may initiate an N2-based handover at target (R)AN (T-RAN) 204t. This can be triggered, for example, due to new radio conditions or load balancing, lack of Xn connectivity to target (R)AN 204t, error indication from target (R)AN 204t after failed handover based on Xn or based on dynamic information received by S-RAN 204s.

FIG. 54 illustrates in flowchart an example of a method (5400) for handover of a UE 202 from a source RAN 204s to a target RAN 204t in accordance with the Xn-based inter-NG RAN handover procedure (5300) of FIG. Method (5400) may be performed by AMF 218. Method (5400) comprises AMF 218 configured to receive N2 Path Switch Request Message (5308) from target RAN 204t. AMF 218 then sends an N11 message (5310) to SMF 220. AMF 218 then receives an N11 ACK message (5318) from SMF 220. AMF 218 then sends an N2 Path Switch Request ACK message (5320) to target RAN 204t. Other steps may be added to the method (5400).

FIG. 55 illustrates in flowchart another example of a method (5500) for handover of a UE 202 from a source RAN 204s to a target RAN 204t in accordance with the Xn-based inter-NG RAN handover procedure (5300) of FIG. 53. Method (5500) may be performed by SMF 220. Method (5500) comprises SMF 220 configured to receive N1 messages (5310) from AMF 218. SMF 220 then sends N4 session change request message (5312) to UPF 212. Then SMF 220 receives N4 session change response (5314) from UPF 212. The SMF then sends N11 an ACK message (5318) to AMF 218. Other steps may be added to the method (5500).

FIG. 56 illustrates in a message processing flowchart an example of an Xn-based inter-NG RAN handover procedure (5600) with user plane function movement according to an embodiment of the present invention. Procedure (5600) may be used to handover UE 202 from source RAN 204s to destination RAN 204t using Xn when AMF 218 is unchanged and SMF 220 decides that source UPF 212s should be released. The source UPF 212s is the UPF 212 that terminates the N3 interface in the NGC. An IP connection is assumed between source UPF 212 and source RAN 204, and between target UPF 212t and target RAN 204t.

The procedure (5600) includes preparing (5302) a handover and performing (5304) a handover. Performing (5304) handover includes forwarding data (5306) from the source RAN 204s to the target RAN 204t. The target RAN 204t can check if some PDU sessions having the N3 status flag, "N3_AT_UPF_UPDATED", but no data activity in the source RAN 204s, by reading the last data activity time parameter in the PDU session context. If the duration for which the PDU has no data activity is greater than the session inactivity timer parameter, the PDU session is considered to have no data activity. Target RAN 204t may send downlink data (5602) to UE 202. UE 202 may send uplink data (5604). The target RAN 204t may send an N2 path switch request message (5308) to the AMF 218 to report that the UE 202 has moved to a new target cell and a list of PDU sessions to be switched or deleted, a list of PDU sessions that have no data activity marked by the target RAN 204t and a list of PDU sessions that have no data activity marked by the source RAN 204s. Depending on the type of the target cell, the target RAN 204t may include relevant information in the message (5308) for each PDU session, including the RAN type, the N3 RAN address, and the N3 tunnel endpoint identifier. If the target RAN 204t cannot support some of the QoS flows of the session PDU, the N2 Path Switch Request message (5308) may include a list of accepted QoS flows and a list of rejected QoS flows for that session PDU.

The AMF 218 may then send an N11 message (5310) to each SMF 220 associated with the PDU session lists received in the N2 path switch request (5308). For PDU sessions that require a path switch, upon receipt of the N11 message (5310), each of these SMFs 220 determines whether the existing UPF 212 can continue to serve the UE 202. If the existing UPF 212 cannot continue to serve the UE 202 and it is not a session anchor PDU, perform steps (5606) - (5624), as described below. Otherwise, steps (5312) - (5318) of FIG. 53, as described above, execute each of these SMFs 220 if existing UPFs 212 can continue to serve UE 202. For PDU sessions that are in the PDU session list with no data activity marked by the source RAN 204 and in the PDU session list, having no data activity marked by target RAN 204t, AMF 218 may store RAN 204 information. to forward the session ID of the PDU to notify that the session PDU has no data activity.

SMF 220 may initiate release of session PDUs that are not requested by target RAN 204t. SMF 220 may then select a new target UPF 212t (5606) based on the UPF selection criteria in accordance with clause 6.3.3 of TS 23.501. The SMF 220 may perform IP address assignment of the target UPF 212t and allocation of downlink and uplink tunnel IDs. An N4 session establishment request message (5608) (including target RAN 204t address identifiers, uplink and downlink tunnel identifiers) may be sent to target RAN 212t. Target UPF 212t may send a session establishment response message (5610) to SMF 220. SMF 220 may start a timer to be used in step (5622) below. SMF 220 may send an N4 session change request message (5612) to the anchor session PDU 212a. The anchor session PDU 212a may respond with an N4 session change response message (5614). At this point, anchor session PDU 212a may start sending downlink packets (5616) to target RAN 204t using the target RAN 204t's address and tunnel IDs via target UPF 212t.

The SMF 220 may send an N 11 ACK message (5618) (including the CN tunnel information) to the AMF 218. Upon receiving the N11 response message (5618) from the SMF 220, for PDU sessions not having data activity marked by the target RAN 204t, the AMF 218 MAY change the N3 status flag parameter of these PDU sessions from N3_AT_UPF_UPDATED to N3_AT_UPF_NOT_UPDATED. Once the response to the N11 message (5618) is received from all SMFs 220, the AMF 218 may aggregate the received CN tunnel information from these responses and send this aggregated information as part of the N2 SM information in the N2 Path Switch Request ACK (5320) to the target RAN 204t. If none of the requested PDP sessions were successfully switched, AMF 218 may send an N2 Path Switch Request Reject message to target RAN 204t. At the target RAN 204t, for PDU sessions not having data activity marked by the target RAN 204t, the state flag parameter N3 of these PDU sessions may be changed from N3_AT_UPF_UPDATED to N3_AT_UPF_NOT_UPDATED. By sending a resource release message (5322) to the source RAN 204s, the target RAN 204t confirms the success of the handover. Resource release from source RAN 204 is then initiated. UE 202 can now send uplink data (5620). After the timer expires after step (5610), SMF 220 may initiate a source UPF 212s release procedure by sending a session end request (5622) N4 (including the release reason). The originating UPF 212 may confirm the release of resources with a session termination response message (5624) N4.

FIG. 56 further illustrates in the message processing flowchart an example of a handover procedure (5600) between an Xn-based NG(R)AN and a user plane function move, in accordance with embodiments of the present invention. Procedure (5600) may be used to handover UE 202 from source (R)AN 204s to destination (R)AN 204t using Xn when AMF 218 does not change and SMF 220 determines that source UPF 212s should be moved. The source UPF 212s is the UPF 212 that terminates the N3 interface in the NGC. IP connectivity is assumed between source UPF 212 and source RAN 204, and between target UPF 212t and target RAN 204t.

The procedure (5600) includes preparing (5302) a handover and performing (5304) a handover. Performing (5304) a handover includes sending data (5306) from a source (R) AN 204s to a target (R) AN 204t. Target (R) AN 204t sends an N2 Path Switch Request message (5308) to AMF 218 that includes an indication that UE 202 has moved to a new target cell and a list of PDU sessions to be switched or deleted. Depending on the target cell type, the target (R) AN 204t adds to the message (5308) other information for each PDU session to be switched, including the last data activity time parameter and (R) AN information such as N3 address (R )AN and tunnel endpoint ID N3. If the target (R)AN 204t cannot support the QoS flows of the session PDU, the N2 Path Switch Request message (5308) may include a list of accepted QoS flows and a list of rejected QoS flows for that session PDU.

The AMF 218 then sends an N11 message (5310) to each SMF 220 associated with the PDU session lists received in the N2 Path Switch Request message (5308). For PDU sessions that require a path switch, upon receipt of the N11 message (5310), each of these SMFs 220 determines whether the existing UPF 212 can continue to serve the UE 202. If the existing UPF 212 cannot continue to serve the UE 202, and is not a PDU session anchor , then the following steps (7202608) - (5624) are performed. Otherwise, steps (5312) - (5318) of FIG. 53, as described above, I each of these SMFs 220 if their existing UPFs 212 can continue to serve the UE 202. For each PDU session where a path switch is required, the SMF 220 determines whether the existing UPF 212 should be updated with (R) AN information about the tunnel.

SMF 220 initiates the release of session PDUs that are not requested by the target RAN 204t. For PDU sessions to be switched, SMF 220 then selects a new target UPF 212t (5606) based on the UPF selection criteria in accordance with clause 6.3.3 of TS 23.501. SMF 220 may perform assignment of the IP address of the target UPF 212t and allocation of downlink and uplink tunnel identifiers. The SMF 220 sends an N4 session establishment request message (5608) to the target UPF 212t. Message (5608) includes the target address of the RAN 204t and the uplink and downlink tunnel identifiers. The target UPF 212t sends an N4 session response message (5610) to the SMF 220. The SMF 220 may start a timer to be used in step (5590) below. The SMF 220 sends an N4 session change request message (5550) to the anchor session PDU 212a. The anchor session PDU 212a responds with an N4 session change response message (5614). At this point, anchor session PDU 212a may begin sending downlink packets (5616) to target RAN 204t using the target RAN 204t's address and tunnel IDs via target UPF 212t.

SMF 220 sends N11 an ACK message (5618) to AMF 218. Message (5618) includes CN tunnel information. At AMF 218, after N11 receives the ACK message (5318), the connection state parameter N3 for PDU sessions where SMF 220 does not update (R)AN information for UPF 212 changes from N3_CONNECTED to N3_DISCONNECTED. Once the N11 ACK message (5318) is received from all SMFs 220, the AMF 218 aggregates the received CN tunnel information from these responses and sends this aggregated information as part of the N2 SM information in the N2 Path Switch Request ACK (5320) to the target (R)AN 204t . The message (5320) includes an indication for each PDU session of whether the UPF 212 has been updated with (R)AN information. If none of the requested PDP sessions were successfully switched, the AMF 218 sends an N2 Path Switch Request Fail message to the target (R) AN 204t. At the target (R) AN 204t, for PDU sessions where the UPF 212 is not updated with the (R) AN information, the UPF N3 tunnel information is removed. By sending a resource release message (5322) to the source (R)AN 204s, the target (R)AN 204t confirms the success of the handover. Resource release is then initiated from the original (R)AN 204.

After the timer expires after step (7302610), the SMF 220 initiates the source UPF 212s release procedure by sending an N4 session end request message (5622) to the source UPF 212s. The message (5622) includes the release reason. Source UPFs 212s acknowledge with session end response message (5624) N4, which indicates the release of resources.

FIG. 57 illustrates in a message processing flowchart an example of an N3 reconnection procedure (5700) triggered by UL data (ie, a new UL data packet) according to an embodiment of the present invention. This procedure (5700) may be used to trigger a path switching update for a PDU session that has N3 status flag as N3_AT_UPF_NOT_UPDATED at the (R)AN 204 when uplink data arrives at the (R)AN 204. The UE 202 may send a channel grant request UL data or UL data packet in (R)AN 204 (5702). If the PDU session state flag N3 is N3_AT_UPF_NOT_UPDATED, (R)AN204 may send an N2 path switch request (5704) to AMF 218. Message (5704) may include a PDU session identifier (such as SUPI) and (R)AN information including type (R)AN, N3 address (R)AN, and N3 tunnel endpoint identifier. Alternatively, the message (5704) may include only the session ID of the PDU.

AMF 218 may send N11 a request message (5706) to switch path to SMF 220 to forward N2 message (5704) received from (R)AN 204. Message (5706) may also include an identifier to identify UE 202 (e.g., temporary identifier 5G or SUPI) and (R)AN information (such as (R)AN type, N3 (R)AN address, and N3 tunnel endpoint ID). SMF 220 may send N4 a session change request message (5708) to UPF212. Message (5708) may include an identifier to identify the UE 202 (such as a 5G temporary identifier or SUPI), a PDU session identifier, (R)AN tunnel information (such as an N3 (R)AN address, and an N3 tunnel endpoint identifier). The UPF 212 may update the (R)AN 204 information for the requested session PDU. The UPF 212 may send a session change response message (5710) to the SMF 220. The message (5710) may include a UE identifier (such as SUPI) and a PDU session identifier. SMF 220 may change the PDU session status flag N3 to N3_AT_UPF_UPDATED. SMF 220 may send an N11 path switch response message (5712) to AMF 218. Message (5712) may include a UE identifier (such as SUPI) and a PDU session identifier. AMF 218 may change PDU session status flag N3 to N3_AT_UPF_UPDATED. AMF 218 may send N2 a path change response message (5714) to the (R)AN 204 to confirm that a path switch has been performed. Message (5714) may include a PDU session identifier. (R) AN 204 may then send packets (5716) of uplink data.

FIG. 57 further illustrates in a message processing flowchart an example of a late path switching procedure (5700) performed by UL data without relocating the UPF 212, in accordance with embodiments of the present invention. This procedure (5700) may be used to trigger a path switching update for a session PDU that does not have N3 UPF tunnel information when the (R)AN 204 receives a UL grant request or UL data for the session PDU. UPF 212 remains the same. SMF 220 stores information about the CN tunnel. UE 202 sends a grant request for a UL data bearer or a UL data packet to the (R)AN 204 for the session PDU (5702). If the N3 UPF tunnel information is not available, the (R)AN 204 sends the N2 session path switch request message (5704) to the AMF 218. The message (5704) includes the PDU session ID and the (R)AN tunnel information such as the N3 address (R ) AN and tunnel endpoint ID N3.

The AMF 218 sends N11 a session path switch message (5706) to the SMF 220. The message (5706) includes an identifier to identify the UE 202 (such as the SUPI session ID and the session PDU ID and (R)AN tunnel information such as the AN type ( R), address (R)AN N3, and downlink tunnel endpoint identifier.SMF 220 determines whether existing UPF 212 can continue to serve UE PDU sessions.If existing UPF 212 cannot continue to serve UE 202 and is not a session PDU anchor, perform steps (4) - (9) of clause 4.9.1.c of TS 23.502 If the existing UPF 212 can continue to serve the UE 202, the SMF 220 sends an N4 session change request message (5708) to the UPF212. The message (5708) includes an identifier UE (such as SUPI), PDU session ID, and N3 (R)AN tunnel information, eg, N3 (R) AN address and N3 tunnel endpoint ID UPF 212 updates the (R) AN 204 tunnel information for the requested session PDU.UPF 212 departure There is an N4 session change response message (5710) in SMF 220. The message (5710) includes the SUPI and the PDU session identifier. SMF 220 sends N11 a path switch response message (5712) to AMF 218. Message (5712) includes a UE identifier (such as SUPI), a PDU session identifier, and an SM N2 message that includes CN tunnel information for the (R)AN 204. SMF 220 changes the connection state of the N3 session PDU to N3_CONNECTED. The AMF 218 sends a Path Switch Response (5714) N2 message to the (R) AN 204, which indicates that the path switch has been completed. Message (5714) includes the PDU session identifier and the N2 SM message received from SMF 220. AMF 218 changes the connection state N3 of the session PDU to N3_CONNECTED. (R)AN 204 updates the CN tunnel information and sends uplink data packets (5716).

FIG. 58 illustrates in a message processing flowchart an example of an N3 reconnection procedure (5800) triggered by DL data (ie, a new DL data packet) according to an embodiment of the present invention. This procedure (5800) may be used to initiate a path switching update at UPF 212 for a session PDU that has state flag N3 as N3_AT_UPF_NOT_UPDATED at SMF 220 when downlink data arrives at UPF 212. UPF 212 may receive downlink data packets from DN 208 (5802). The UPF 212 may send a DL data notification N4 message (5804) to the SMF 220. The message (5804) may include an identifier to identify the UE 202 (such as 5G temporary or SUPI) and a PDU session identifier.

Based on status flag N3, currently set to N3_AT_UPF_NOT_UPDATED, SMF 220 may send N11 an (R)AN information request message (5806) to AMF 218. Message (5806) may include a UE identifier (such as SUPI) and a session identifier PDU. AMF 218 may change PDU session status flag N3 to N3_AT_UPF_UPDATED. AMF 218 may send N11 response message (5808) (R)AN information to SMF 220. Message (5808) includes a UE identifier (such as SUPI), a PDU session identifier, and (R)AN information (including type (R) )AN, address N3 (R)AN, and tunnel endpoint identifier N3 (R)AN). The SMF 220 may send an N4 change request message (5810) to the UPF 212. The message (5810) may include an identifier to identify the UE 202 (such as a 5G temporary identifier or SUPI), a PDU session identifier, (R)AN information (such as N3 (R)AN address and N3 tunnel endpoint ID). The UPF 212 may update the (R)AN 204 information for the requested session PDU. The UPF 212 may send a session change response message (5812) to the SMF 220. The message (5812) may include a UE identifier (such as SUPI) and a PDU session identifier. Upon receiving the message (5690), SMF 220 may change the PDU session status flag N3 to N3_AT_UPF_UPDATED. UPF 212 may send downlink data packets (5814) to UE 202 via (R)AN 204. It should be noted that step (5814) may be performed before step (5812).

In the alternative embodiment of FIG. 58, upon receiving message (5806), AMF 218 may send an N2 notification message to (R)AN 204 informing that UPF 212 is being updated with (R)AN information. The message may include a PDU session identifier. The (R)AN 204 may change the PDU session status flag N3 to N3_AT_UPF_UPDATED. The (R)AN 204 may send a notification acknowledgment N2 to the AMF 218 acknowledging receipt of the notification message from the AMF 218.

In another alternative embodiment of FIG. 58, upon receiving message (5812), SMF 220 may send message N2 to (R)AN 204 via AMF 218 to notify (R)AN 204 that UPF 212 has updated (R)AN information. The message may include a PDU session identifier. Upon receipt of this message, the (R)AN 204 may change the PDU session status flag N3 to N3_AT_UPF_UPDATED.

(R) AN-CN interactions include procedures that relate to N2 (eg, NG2) interactions, such as an N2 release procedure and potential procedures for an RRC connection idle state.

The N2 release procedure may be used to release the N2 signaling logical connection and all N3 connections to the UE 202. The procedure will transition the UE 202 from the CN-CONNECTED state to the CN-IDLE state in both UE 202 and AMF 218. That is, the UE context in UE 202 and AMF 218 will be changed accordingly. All UE related context information will be deleted at (R)AN 204.

When the N2 signaling connection is lost, for example due to loss of transport signaling or due to failure of the (R)AN, the N2 release procedure may be performed locally by (R)AN 204 and AMF 218. When the N2 release procedure is performed locally by (R)AN )AN 204 or AMF 218, each node performs its actions locally as described in the sequence of operations below, without using any of the signaling shown directly between (R)AN 204 and AMF 218. It should be noted that when the N2 signaling connection is lost due to failure of AMF 218, due to N2 stickiness and does not release N2. The initiation of the N2 release procedure can be performed by either (R)AN or AMF. The reason for the (R)AN-initiated procedure may be at least one of O&M intervention, unspecified failure, user inactivity, repeated RRC signaling integrity check failure, release due to UE generated connection release signaling, Inter-RAT redirection, and etc. The reason for the procedure initiated by the AMF may be at least one of: authentication failure, disconnection, etc.

The N2 release procedure may be used to release the N2 connection and at the same time to deactivate PDU sessions when the UE 202 enters the CM-IDLE state. Fig. 59 illustrates, in a message processing flow diagram, an example of an N2 release and PDU session procedure (5900) in accordance with embodiments of the present invention. Procedure (5900) may start with (R)AN 204 and UE 202 performing RRC release procedure (5902). The RRC release procedure (5902) may be similar to the RRC release procedure (600A) described above. The (R)AN 204 interacts with the UE 202 to release the signaling RRC connection. UE 202 enters the CM-IDLE state and deactivates all PDU sessions. The (R)AN 204 may send (message N2) an N2 release request (5904) to the AMF 218. The message (5904) may include a reason code such as O&M intervention, UE inactivity, and so on. Those skilled in the art will appreciate that, in certain scenarios, step (5902) may be initiated before or in parallel with step (5904). The AMF 218 may send (message N11) an N2 release notification message (5906) to the SMF(s) 220 that have subscribed to the N2 release notification. Message (5906) may include a UE identifier (such as SUPI), RAN information, and a reason code. It should be noted that the SMF 220 may subscribe to the UE AMF 218's mobility event notification service by default when a session PDU is established or activated. In this message, the AMF 218 will notify the SMF 220 of the N2 release event. AMF 218 may monitor or otherwise learn about the state of the session, that is, whether the session is activated or not. The AMF 218 informs the SMFs 220 that serve the activated PDU sessions of the state of the session.

The SMF 220 then sends (message N4) an N3 release request (5908) to the UPF(s) 212. The message (5908) may include the SUPI UE and PDU session ID(s) to be deactivated. UPF 212 then releases N3 the (R)AN tunnel information (eg, (R)AN IP address and tunnel ID) in the context of the UE PDU session for the PDU sessions to be deactivated. The UPF sends (message N4) an N3 release response (5910) to the SMF 220 acknowledging the (R)AN tunnel information release N 3 . UPF 212 may begin buffering the downlink packets of the deactivated session PDUs. The SMF 220 then sends (message N11) a PDU session event notification (5912) to the AMF 218 to inform the AMF 218 that the (R)AN tunnel information has been deleted in the UPF 212. This message (5912) shall acknowledge the notification message (5906) release of N2. SMF 220 may then change the session state of the PDU to "Session-IDLE".

AMF 218 then collects all responses from SMF(s) 220 that were notified at (5906). Once all acknowledgments from the SMF 220 have been collected, and if step (5902) is not performed, the AMF 218 then sends (message N2) an N2 release response (5914) to the (R)AN 204 with a reason code. AMF 218 may change the session state of all session PDUs of UE 202 to "Session-IDLE". If step (5902) has not been performed, RAN 204 and UE 202 perform an RRC release procedure (5916). The RRC release procedure (5916) may be similar to the RRC release procedure (600A) described above. The (R)AN 204 sends a message to the UE 202 to release the RRC connection. UE 202 enters the CM-IDLE state and all PDU sessions at UE 202 transition to the "Session-IDLE" state. Upon receipt of the RRC connection release acknowledgment from the UE 202, the (R)AN 204 deletes the UE context. The (R)AN 204 then sends (message N2) an N2 release acknowledgment (5918) to the AMF 218. Upon receiving an N2 release response message (5918), the AMF 218 sets the UE context to the CM-IDLE state and releases the N2 connection. It should be noted that the AMF 218 may remove the subscription to the AMF UE 218 mobility event notification service for the SMF service PDU(s) sessions.

In a modification of the embodiment described with reference to FIG. 59, the N2 release procedure may be used to release the N2 connection and at the same time deactivate PDU sessions when the UE 202 enters the CM-IDLE state. Fig. 60 illustrates in a message processing flowchart another example of an N2 release and session PDU procedure (6000) in accordance with embodiments of the present invention. Procedure (6000) may start with (R)AN 204 and UE 202 performing RRC release procedure (5902). The RRC release procedure (5902) may be similar to the RRC release procedure (600A) described above. (R) AN 204 interacts with UE 202 to release the signaling RRC connection. UE 202 enters the CM-IDLE state and deactivates all PDU sessions. The (R)AN 204 may send (message N2) an RRC release notification (5904) to the AMF 218. The message (6002) may include a reason code such as O&M intervention, UE inactivity, and so on. Those skilled in the art will appreciate that, in certain scenarios, step (5902) may be initiated before or in parallel with step (6002). The AMF 218 may send (message N11) an N2 release notification message (6004) to the SMF(s) 220 that have subscribed to the N2 release notification. Message (6204) may include a UE identifier (such as SUPI), RAN information, and a reason code. It should be noted that the SMF 220 may subscribe to the default N2 release notification service when a PDU session is established or activated. AMF 218 may monitor or otherwise learn about the state of the session, that is, whether the session is activated or not. The AMF 218 informs the SMFs 220 that serve the activated PDU sessions of the state of the session.

The SMF 220 then sends (message N4) an N3 release request (6006) to the UPF(s) 212. The message (6006) may include a UE identifier (such as SUPI) and a PDU session identifier(s) to deactivate. The UPF 212 then releases the N3 (R)AN tunnel information (eg, (R)AN IP address and tunnel endpoint ID) in the context of the UE PDU session for the PDU sessions to be deactivated. The UPF sends (message N4) an N3 release response (6008) to the SMF 220 acknowledging transmission of the N3 tunnel information. UPF 212 may begin buffering the downlink packets of the deactivated session PDUs. The SMF 220 then sends (message N11) a release notification confirmation message (6010) N2 to the AMF 218, which acknowledges the release notification message (6004). SMF 220 may then change the session state of the PDU to "Session-IDLE".

AMF 218 then collects all responses from SMF(s) 220 that were notified at (6004). Once all acknowledgments from SMFs 220 have been collected, and if step (5902) is not completed, AMF 218 then sends (message N2) an N2 release request message (6012) to (R)AN 204 with a reason code. AMF 218 changes the session state of all session PDUs of UE 202 to "Session-IDLE". If step (5902) has not been performed, (R) AN 204 and UE 202 perform RRC release procedure (5916). The RRC release procedure (5916) may be similar to the RRC release procedure (600A) described above. The (R)AN 204 sends a message to the UE 202 to release the RRC connection. UE 202 enters the CM-IDLE state and all PDU sessions at UE 202 transition to the "Session-IDLE" state. Upon receiving an RRC connection release acknowledgment from UE 202, RAN 204 deletes the UE context. The (R) AN 204 then sends (message N2) an N2 release response (6014) to the AMF 218. Upon receiving the N2 release response message (6014), the AMF 218 sets the UE context to the CM-IDLE state and releases the N2 connection.

UE 202 or a network requested session PDU release for non-roaming and roaming with a local break procedure may be used to release the session PDU when UE 202 is in the CM-CONNECTED state. Fig. 61 illustrates in a message processing flowchart an example procedure (6100) for releasing a session PDU initiated by UE 202, PCF 222, or SMF 220, in accordance with embodiments of the present invention. One trigger for the session PDU release procedure (6100) is initiated when the UE 202 sends a UE session release request message (N1 SM message) message (6102) to the SMF 220. Message (6102) may include a PDU session ID. (R) AN 204 forwards the message over a logical interface such as an N2 connection. AMF 218 checks the session ID of the PDU and forwards the message to SMF 220. The forwarded message from AMF 218 to SMF 220 includes a UE identifier (such as SUPI) and a session PDU release request of message N1. Another trigger for the session PDU release procedure (6100) is initiated when the PCF 222 sends an N7 PCF session release request message (6104) to the SMF 220. Another PDU session release procedure (6100) trigger is initiated when SMF 220 decides to release PDU sessions using its own logic or by receiving requests from at least one of the UE 202, AN 204 (eg, congestion report), DN 208 and UPF 212.

Once the trigger PDU session release procedure (6100), the SMF 220 interacts with the UPF 212 to release the PDU context in the UPF 212. The SMF 220 sends an N4 message session release request message (6108) to the UPF 212. The message (6108) may include, at least one of a UE ID (such as SUPI) and a PDU session ID. UPF 212 discards any remaining session PDUs to be released and releases the UE PDU context. The UPF 212 then sends a session release response message (6110) to the SMF 220. If a dynamic policy is implemented, the SMF 220 informs the PCF 222 that the PDU-CAN PDU session release procedure (6112) has been completed, so that the PCF 222 will not provide any additional session change messages. SMF 220 related to the released session PDU. SMF 220 knows if the session state is enabled. The SMF 220 sends an N11 message (6202) to the AMF 218 that includes the UE ID (eg, SUPI), the N1 SM PDU session release request to the UE 202, and the N2 SM PDU session release request to the (R)AN 204 if the session PDU was activated. The N1 SM PDU session release request message may include PDU session identifier(s) and reason code(s). The N2 SM PDU session release request message may include PDU session identifier(s). Messages N1 SM and N2 SM can be wrapped in a container. SMF 220 may use the AMF 218 messaging service as defined in clause 5.2.2.4 of TS 23.502 to send N1 SM and N2 SM messages to UE 202 and (R)AN 204.

AMF 218 then transmits (6116) the message received from SMF 220 to (R)AN 204 via a logical interface such as an N2 connection. If the (R)AN 204 receives only the N1 SM PDU session release request, the (R)AN 204 forwards (6118) this message to the UE 202. If the (R)AN 204 receives the N1 SM PDU session release request and the N2 session PDU release request, (R)AN 204 performs an RRC connection reconfiguration with UE 202. During this reconfiguration procedure, the (R)AN 204 sends a N1 SM session PDU release request to UE 202. (R)AN 204 and UE 202 release the radio resource(s) for the released session(s) of the PDU. UE 202 and AN 204 release the PDU session context. If the (R)AN 204 receives the N2 SM PDU session release request at step (6224), the (R)AN 204 sends a session release N2 SM PDU response (6120) via the AMF 218 to the SMF 220. The message (6120) may include an identifier ( identifiers) of the PDU session. The AMF 218 sends a message (6122) to N11 to forward the N2 SMU PDU session response to the SMF 220. The message (6122) includes the UE identifier (such as SUPI) and the N2 SM session PDU response received from the (R)AN 204. Thereafter As the UE 202 receives the N1 SM session PDU release request in step (6118), the UE 202 releases the resources serving the released PDU sessions and removes the PDU session context. The UE 202 sends an N1 SM PDU session release response (6124) to the SMF 220. The message includes the PDU session ID(s). (R) The AN 204 sends this message to the AMF 218 via a logical interface such as an N2 connection. The AMF 218 sends an N11 message to forward (6126) the N1 SM PDU session release response received in step (6124) to the SMF 220. The N11 message may include at least one of: a UE identifier (such as SUPI) and N1 SM PDU session release response received in step (6122). After receiving the messages in steps (6122) and (6126), the SMF 220 sends an N11 message PDU session event notification message (62046128) as defined in 5.2.8.1 of TS 23.502 to the AMF 218 with a session PDU release trigger. SMF 220 and AMF 218 delete their session context PDU of the released session PDU.

As noted above, procedure (6100) may be used to perform session PDU release initiated by UE 202. Alternatively, procedure (6100) may be used, with some modifications, as a session PDU release procedure requested by the network in the absence of roaming and with local break roaming for releasing a session PDU when the UE 202 is in the CM-IDLE state. For example, if UE 202 is in the CM-IDLE state, AMF 218 will send a paging message to UE 202 carrying a PDU session release notification and a session ID of the PDU to be released. The remaining steps are similar to the procedure (6100). For example, UE 202 sends a session release request for SMU PDU N1 to SMF 220.

In a modification of the embodiment described with reference to FIG. 61, UE 202 or a network-requested session PDU release with no roaming and with local interrupt procedure roaming may be used to release the session PDU when the UE 202 is in the CM-CONNECTED state or the CM state. -IDLE. The SMF 220 may be unaware of the UE's connection control state, but knows if the session PDU is up. If the UE 202 is in the CM-IDLE state, the AMF 220 may send the session state PDU to the AMF 218 to the UE 202 for synchronization when the service request procedure is performed. Fig. 62 illustrates in a message processing flowchart another example of a PDU session release procedure (6200) initiated by UE 202 or SMF 220, in accordance with embodiments of the present invention. One trigger for the session PDU release procedure (6200) is initiated when the UE 202 sends a UE session release request message (6102) (N1 SM message) to the SMF 220. Message (6102) may include a PDU session identifier. The (R)AN 204 forwards the message over a logical interface such as an N2 connection. AMF 218 checks the session ID of the PDU and forwards the message to SMF 220. The forwarded message from AMF 218 to SMF 220 includes a UE identifier (such as SUPI) and a session PDU release request of message N1. Another trigger for the session PDU release procedure (6200) is initiated when the PCF 222 sends a "PCF Session Release Request" message (6104) to the SMF 220 N7. Another trigger for the PDU session release procedure (6100) is initiated when SMF 220 decides to release PDU sessions using its own logic or by receiving requests from UE 202, AN 204 (eg, congestion report), DN 208, and UPF. 212.

Once the PDU session release procedure (6200) has been initiated, the SMF 220 interacts with the UPF 212 to release the PDU context to the UPF 212. The SMF 220 sends an N4 message session release request (6108) to the UPF 212. The message (6108) may include, at least one of: a UE identifier (such as SUPI) and a PDU session identifier. UPF 212 discards any remaining session PDUs to be released and releases the UE PDU context. The UPF 212 then sends a session end response (N4 message) (6110) to the SMF 220. If a dynamic policy is implemented, the SMF 220 informs the PCF 222 that the PDU-CAN PDU session release procedure (6112) has been completed. SMF 220 knows if the session state is enabled. The SMF 220 sends an N11 message session release notification (6202) to the AMF 218, which includes the UE ID (eg, SUPI), the N1 SM PDU session release request to the UE 202, and the N2 SM PDU session release request to the (R)AN 204 if the PDU session has been activated. The N1 SM PDU session release request message may include PDU session identifier(s) and reason code(s). The N2 SM PDU session release request message may include PDU session identifier(s). Messages N1 SM and N2 SM can be wrapped in a container. SMF 220 may use the AMF messaging service 218 to send N1 SM and N2 SM messages to UE 202 and (R)AN 204.

If the UE is in the CM-CONNECTED state, then the AMF 218 transmits (6116) the message received from the SMF 220 to the (R)AN 204 via a logical interface such as an N2 connection. If the (R)AN 204 receives only the N1 SM PDU session release request, the (R)AN 204 forwards (6118) this message to the UE 202. If the (R)AN 204 receives the N1 SM PDU session release request and the N2 session PDU release request, (R) The AN 204 performs an RRC connection reconfiguration with the UE 202. During this reconfiguration procedure, the (R)AN 204 sends a session release request N1 SM message PDU to the UE 202. R) The AN 204 and UE 202 release the radio resource(s) for the released session (sessions) PDU. UE 202 and (AN)AN 204 release the PDU session context. If the (R) AN 204 receives the N2 SM PDU session release request in step (6116), the (R) AN 204 sends an N2 SM PDU session release response (6120) to the SMF 220 via the AMF 218. The message (6120) may include an identifier ( identifiers) of the PDU session. The AMF 218 sends a message (6275) to N11 to forward the N2 SMU PDU session response to the SMF 220. The message (6275) includes the UE identifier (such as SUPI) and the N2 SM session PDU response received from the (R)AN 204. If the UE 202 receives the N1 SM session PDU release request in step (6118), then the UE 202 releases the resources serving the released PDU sessions and deletes the PDU session context. The UE 202 sends a session PDU release response (6122) to the SM SMF 220. The message includes the PDU session ID(s). The (R)AN 204 sends this message to the AMF 218 via a logical interface such as an N2 connection. The AMF 218 sends an N11 message to forward (6124) the N1 SM PDU session release response received in step (6122) to the SMF 220. The N11 message may include at least one of: a UE identifier (such as SUPI) and session release response SM PDU N1 received at step (6122). After receiving the messages in steps (6275) and (6124), SMF 220 sends a session release acknowledgment (6204) of message N11 to AMF 218. SMF 220 and AMF 218 remove their session context PDU from the released session PDU.

If UE 202 is in the CM-IDLE state, messages 6224, 6118, 6120, 6275, 6122, 6124, and 6204 are skipped. AMF 218 sends a session release acknowledgment (6206) of Message N11 PDU to SMF 220.

5G, UE 202 may use a service request procedure in the CM-IDLE state to request the establishment of a secure connection with AMF 218. A UE 202 in the CM-IDLE state may initiate a service request procedure to send an uplink signaling message, user data, or a response to a paging request. online. Upon receiving the service request message, the AMF 218 may perform an authentication and security procedure. After establishing a secure signaling connection with AMF 218, either UE 202 or the network may send signaling messages, such as PDU session establishment from UE 202 to core network 206, or SMF 220 through AMF 220 may initiate user plane resource establishment for PDU sessions requested by the network and /or specified in the service request message.

For any service request, AMF 218 may respond with a service response message to synchronize the PDU session state between UE 202 and core network 206. AMF 218 may also respond with a service reject message at UE 202 if the service request cannot be accepted by the network. To request a service due to user data, the network may take additional action if the user plane resource establishment was not successful. It should be noted that the service request procedure discussed in FIG. 63 below is not applicable to an access network such as a WiFi network (after the UE 202 has registered with the network) in which the UE 202 is always considered to be in the CM-CONNECTED state and in which the user plane resource is always considered to be set to active. PDU session.

FIG. 63 illustrates in a message invocation diagram an example of an Xn-based inter-NG(R)AN handover procedure (6300) without user plane function relocation and with session deactivation, in accordance with embodiments of the present invention. The procedure (6300) combines the handover procedure defined in clause 4.9.1.1 of TS 23.502 and the session deactivation signaling message. The procedure (6300) includes preparing (6302) a handover and performing (6304) a handover. Performing (6304) a handover includes sending data (6306) from a source (R) AN 204s to a target (R) AN 204t.

Target (R) AN 204t sends an N2 Path Switch Request message (6308) to AMF 218 that includes an indication that UE 202 has moved to a new target cell and a list of session PDUs to be switched or removed. Depending on the target cell type, the target (R) AN 204t pads this message with the appropriate information. The PDU sessions to be switched are PDU sessions having UPF N3 tunnel information. For each PDU session to be switched, the target (R) AN 204t includes a last data activity time parameter and (R) AN information such as the N3 address of the (R) AN and the N3 tunnel endpoint identifier. If the target (R) AN 204t cannot support some of the QoS flows of the session PDU, then the N2 path switch request message (6308) includes a list of accepted QoS flows and a list of rejected QoS flows for that session PDU.

The AMF 218 then sends an N11 message (6310) to each SMF 220 associated with the list of session PDUs received in the N2 Path Switch Request message (6308). For PDU sessions that require path switching, upon receipt of the N11 message (6310), each of the SMFs 220 determines whether the existing UPF 212 can continue to serve the UE 202. If the existing UPF 212 cannot continue to serve the UE 202 and it is not a PDU session anchor , perform steps 3-11 of clause 4.9.1.2 of TS 23.502. Otherwise, each of the SMFs 220 performs the following steps (6312) - (6322) if the existing UPF 212 can continue to serve the UE 202. For each PDU session that requires a path switch, the SMF 220 determines whether or not to deactivate the session.

The SMF 220 initiates the release of session PDUs that are not requested by the target (R)AN 204t. For PDU sessions requested by target (R) AN 204t, SMF 220 sends to UPF 212 an N4 session change request (6312) including the (R) AN address, tunnel identifiers for the downlink user plane, and a list of received streams, if present. . In order for the PDU sessions to be deactivated, the SMF 220 sends an N4 session change request message (6312) to the UPF 212 for these PDU sessions. Message (6312) indicates the release of (R)AN N3 tunnel information including the (R)AN address and tunnel endpoint identifier for the downlink user plane. The UPF 212 returns an N4 session change response message (6312) to the SMF 212 after the requested session PDUs are switched or changed. Message (6314) includes tunnel identifiers for uplink traffic. To assist the reordering function in the target (R) AN 204t for PDU sessions requiring a path switch, UPF 212 sends one or more "end marker" packets (6316) over the previously used path immediately after the path switch. UPF 212 starts sending downlink packets (6318) to target (R) AN 204t.

The SMF 220 sends to the AMF 218 an ACK message (6320) of the N11 message for the PDU sessions that were successfully switched. The message (6320) includes CN tunnel information and indicates whether the N3 AN (R) tunnel information is updated (eg, path switched) or deactivated (eg, path released). The ACK (6320) message N11 includes an SM message N2 including the PDU session ID(s) for the (R)AN 204 to deactivate PDU sessions. In SMF 220, for session PDUs that are deactivated, the session state parameter is changed to "Session-IDLE". It should be noted that step (6320) may occur at any time after receiving the N4 session change response message (6314) in SMF 220.

Upon receiving the ACK (6320) of the N11 message, the AMF 218 sets the session state of the PDU sessions accordingly. Once an ACK response (6320) to the N11 message is received from all SMFs 220, the AMF 218 aggregates the received CN tunnel information from these responses and sends this aggregated information as part of the N2 SM information and N1 message session deactivation request (including the session ID of the PDU to be deactivated) in the N2 Path Switch Request ACK (6322) message at the target RAN 204t. If none of the requested PDP sessions were successfully switched, the AMF 218 sends an N2 Path Switch Request Fail message as a message (6322) to the target (R) AN 204t. At the target (R) AN 204t, for PDU sessions to be deactivated, the UPF N3 tunnel information is removed. (R) The AN 204t forwards the session deactivation request message N1 message (6324) to the UE 202 in an RRC message. The UE 202 sets the session state of the session PDUs indicated in the N1 SM message to "Session-IDLE". UE 202 releases the radio context of the deactivated PDU sessions. UE 202 sends an N1 message session deactivate response message (6326) to AMF 218 via target (R) AN 204t. By sending a resource release message (6328) to the source RAN 204, the target (R)AN 204t confirms the success of the handover. Resource release is then initiated from the source RAN 204.

In FIG. 64 illustrates in a message processing flowchart an example of a service request procedure (6400) initiated by a UE, in accordance with embodiments of the present invention. The UE 202 may send to the (R)AN 204 an MM MM service request message (6402) that includes the PDU session ID(s), security parameters, and the PDU session state. The UE 202 sends a NAS message service request in an RRC message encapsulated AMF 218 to the RAN 204. If a service request is initiated for user data, the UE 202 adds the PDU session identifier(s) in the NAS service request message (6402) to indicate the session(s). ) PDU that UE 202 requests to use. If a service request is initiated for signaling only, UE 202 does not need to add any PDU session ID. When this procedure (6400) is initiated for a paging response, if the UE 202 needs to use some PDU session(s), the UE 202 adds these PDU session IDs to the MM MM service request message (6402). Otherwise, UE 202 does not need to add any PDU session identifier. The PDU session state indicates the PDU sessions available at the UE 202. The PDU session state is added if the UE 202 has released some PDU sessions but has not informed the AMF 218 when the UE 202 is in the CM-IDLE state.

(R) The AN 204 then sends a message (6404) to the N2 AMF 218, which includes the NAS MM service request, 5G temporary identifier, location information, RAT type, and RRC establishment reason. If the AMF 218 cannot process the service request, it will reject it. The temporary 5G identifier is accepted in the RRC procedure. RAN 204 selects AMF 218 according to this temporary identifier. The location information and RAT type are related to the cell in which UE 202 is located. Based on the PDU session state, AMF 218 may initiate a PDU session release procedure if the PDU session is not available at UE 202.

If the service request was not sent with integrity protection, or if the integrity protection is indicated as failed, AMF 218 may initiate a NAS authentication/security procedure (6406). If the UE 202 initiated the service request only to establish a signaling connection, then after exchanging security information, the UE 202 and the network may send the signaling.

If the NAS MM Service Request message includes a PDU session ID(s) or if this procedure (6400) is initiated by the SMF 220 but the PDU session IDs from the UE 202 correlate with other SMFs 220 than the one initiated by the procedure, the AMF 218 sends N11 message (6408) in SMF(s) 220 associated with PDU session ID(s). Upon receipt of the N11 message (6408), each SMF 220 sends an N11 message (6410) to the AMF 218 to set up a user plane for PDU sessions. The message (6410) includes N2 SM information such as a QoS profile and N3 CN tunnel information. The N2 SM information includes information that AMF 220 may provide to RAN 204.

The AMF 218 may send to the N2 (R)AN 204 a request message (6412) that includes the N2 SM information received from the SMF 220, the security context, the AMF signaling connection ID, the handover restriction list, and the NAS acknowledgment MM. The RAN 204 stores the security context, the AMF signaling connection identifier, the QoS information for the QoS flows of the activated session PDUs, and N3 tunnel identifiers in the context of the UE RAN. The MM NAS confirmation of the service includes the PDU session state in the AMF 218. The PDU session state is added if the core network has released some PDU sessions but has not informed the UE 202 when the UE 202 is in the CM-IDLE state. AMF 218 may include at least one N2 SM information element from SMF 220 if the procedure (6400) is initiated to set up a user plane session PDU. AMF 218 may send additional SM N2 information from SMF 220, if any, in a separate N2 message(s), such as an N2 tunnel establishment request. Alternatively, if multiple SMFs 220 are involved, AMF 218 may send one N2 request message to (R)AN 204 after all N11 messages from SMF 220 have been received. In such a scenario, the N2 request message includes the N2 SM information received in each of the N11 messages and information to allow the AMF 218 to associate responses with the corresponding SMF 220.

(R) The AN 204 may perform a RRC connection reconfiguration procedure (6414) with the UE 202 depending on the QoS information for all QoS flows of activated PDU and DRB sessions. At this point, the security of the user plane is established. (R) The AN 204 forwards the NAS MM service acknowledgment to the UE 202. The UE 202 locally deletes the session context of PDUs that are not available on the 5G CN 206.

After configuring the user plane radio resources, the uplink data from the UE 202 can now be forwarded (6416) to the (R)AN 204. The 5G RAN 204 sends the uplink data to the UPF address 212 and the tunnel ID provided in steps (6408) and ( 6410). (R)AN 204 may send to AMF 218 an N2 request ACK (6418) that includes N2 SM information such as (R)AN tunnel information, a list of accepted QoS flows for activated session PDUs, and a list of rejected QoS flows for activated sessions PDU). Message (6418) may include SM N2 information element(s), eg, RAN tunnel information. (R) The AN 204 may send the N2 SM information in separate N2 messages, such as an N2 tunnel setup response, if the AMF 224 sends separate N2 messages in step (6412). If multiple N2 SM information elements are added to the N2 request message (6412), then the N2 request ACK (6418) may include multiple N2 SM information elements and information to allow the AMF 218 to associate responses with the corresponding SMF 220. The AMF 218 may send the N11 SMF a message (6420) that includes N2 SM information, such as RAN tunnel information and RAT type, for each received PDU session, in SMF 220. If AMF 218 received N2 SM information (one or more elements) in step (6418 ), the AMF 218 forwards the SM N2 information to the corresponding SMF 220. If the UE's time zone has changed from the UE's last reported time zone, then the AMF 218 includes the UE's time zone IE in this message (6420). If a dynamic PCC is deployed, then the SMF 220 may further initiate an IP-CAN session change (6422) and provide the new location information to the PCF 222.

SMF 220 may send to UPF 212 an N4 session update request message (6424) that includes RAN tunnel information. If the user plane needs to be set up or changed, SMF 220 initiates the N4 session change procedure and provides information about the RAN tunnel. The UPF 212 may then send an N4 session update response message (6426) to the SMF 220. The SMF 220 may then send an ACK (6426) N11 message to the AMF.

The session state may be used to indicate that the UE 202 has activated a PDU session to send and receive data. The two types of session states include an active state (sometimes referred to as the "Session-ACTIVE" state) and an idle state (sometimes referred to as the "Session-IDLE" state). UE 202 serving AMF 218 and serving SMF 220 may maintain session state status locally.

When the session PDU is in the "Session-IDLE" state, the UP data connection between the UE 202 and the N3 tunnel termination UPF 212 is not established. The UE does not send or receive data in the "Session-IDLE" state. (R) AN 204 does not have a session context PDU in the "Session-IDLE" state. The terminating N3 UPF 212 connection has a UE PDU session context but no (R)AN N3 connection information (eg, no (R)AN 204 IP address and no N3 tunnel endpoint ID). SMF 220 may store UE PDU session context information related to SMF 220 but without AN (R) information 204. AMF 218 may store all UE PDU session context information related to AMF 218.

When the session PDU is in the "Session-ACTIVE" state, UE 202 may send and receive data. The Uu interface between UE 202 and (R)AN 204 is set to the "Session-ACTIVE" state. The N3 connection is established when the PDU session is activated. UE 202 has access to all PDU session context information including DRB information. AMF 218 stores all UE PDU session context information related to AMF 218. SMF 220 stores all UE PDU session context information related to SMF 220.

Table 3 provides a description of the "Session-ACTIVE" and "Session-IDLE" states for various network entities.

Table 3: Description of session state

network object Session-ACTIVE session IDLE UE 202
(maintains session state) Has all NAS context and AS session PDU information Has NAS context information and AS session PDU without DRB information (R)AN 204
(does not maintain session state) Has all the context information of the session PDU. However, depending on the UE's data activity, the (R)AN 204 may not have the UPF connection information N3. Has no session PDU context UPF 212
(does not maintain session state) Has all the context information of the session PDU. However, depending on the data activity, the UPF 212 may not have the (R)AN N3 connection information. Has session context PDU without (R)AN connection information N3 AMF 218
(supports session state and N3 connection status) Has all the session PDU context information related to access control and mobility. Has all the session PDU context information related to access control and mobility. SMF 220
(supports session state and N3 connection status) Has all the context information of the session PDU. However, depending on the N3 flag status, the SMF 220 may not have the (R)AN information if the N3 connection status is N3_DISCONNECTED. Has session context PDU without (R)AN information

In FIG. 64 further illustrate, in a message processing flowchart, an example of a UE-initiated service request procedure (6400) in a CM-IDLE state in accordance with embodiments of the present invention. UE 202 may send to the (R)AN 204 a NAS MM service request message (6402) that includes the PDU session ID(s), security parameters, and PDU session state. The UE 202 may send a NAS message service request (6402) to the AMF 218 encapsulated in an RRC message to the RAN 204. The RRC message may be used to transmit a 5G temporary identifier. If a service request is initiated for user data, UE 202 may add PDU session identifiers to the NAS service request message (6402) to indicate the PDU session(s) that UE 202 is requesting to use. If the service request is initiated for signaling only, UE 202 does not need to use any PDU session ID. When initiating a procedure (6400) for a paging response, if the UE 202 needs to use some PDU session(s), the UE 202 may add these PDU session IDs to the NAS MM service request message (6402). Otherwise, UE 202 does not need to use any PDU session identifier. The PDU session state indicates the PDU sessions available at UE 202.

(R) The AN 204 may then send a message (6404) to the N2 AMF 218 that includes the NAS MM service request, 5G temporary identifier, location information, RAT type, and RRC establishment reason. If the AMF 218 cannot process the service request, it will reject it. Temporary 5G ID received in RRC procedure. RAN 204 may select AMF 218 according to this temporary identifier. The location information and RAT type are related to the cell in which UE 202 is located. Based on the PDU session state, AMF 218 may initiate a PDU session release procedure if the PDU session is not available at UE 202.

If the service request was not sent with integrity protection, or if the integrity protection is indicated as failed, AMF 218 may initiate a NAS authentication/security procedure (6406). If the UE 202 initiated the service request only to establish a signaling connection, then after the security exchange, the UE 202 and the network may send the signaling.

If the NAS MM service request message includes PDU session ID(s), or if this procedure (6400) is initiated by SMF 220, PDU session IDs from UE 202 correlate with other SMFs 220 than the one that initiates the procedure, AMF 218 sends N11 message (6408) in SMF(s) 220 associated with PDU session ID(s). Upon receipt of the N11 message (6408), each SMF 220 sends an N11 message (6410) to the AMF 218 to set up a user plane for PDU sessions. The message (6410) includes N2 SM information such as a QoS profile and N3 CN tunnel information. The N2 SM information includes information that AMF 220 may provide to RAN 204.

The AMF 218 may send to the N2 (R)AN 204 a request message (6412) that includes the N2 SM information received from the SMF 220, the security context, the AMF signaling connection ID, the handover restriction list, and the service confirmation NAS MM. The RAN 204 may store the security context, the AMF signaling connection identifier, the QoS information for the QoS flows of the activated PDU sessions, and the N3 tunnel identifiers in the context of the UE RAN. The NAS MM service confirmation includes the session state of the PDU in the AMF 218. The AMF 218 may include at least one N2 SM information element from the SMF 220 if the procedure (6400) is initiated to set up a session PDU user plane. AMF 218 may send additional SM N2 information from SMF 220, if any, in a separate N2 message(s), such as an N2 tunnel setup request. Alternatively, if multiple SMFs 220 are involved, AMF 218 may send one N2 request message to (R)AN 204 after all N11 messages from SMF 220 have been received. In such a scenario, the N2 request message includes N2 SM information received in each of N11 messages, and information allowing the AMF 218 to associate responses with the corresponding SMF 220.

(R) The AN 204 may perform a connection RRC reconfiguration procedure (6414) with the UE 202 depending on the QoS information for all QoS flows of activated PDU and DRB sessions. This step establishes the security of the user plane. (R)AN 204 may forward the NAS MM acknowledgment of service to UE 202. UE 202 may locally delete session context of PDUs that are not available at 5G CN 206. If (R)AN 204 receives in at least one of UE 202's QoS streams may keep the session state of the PDU activated. Otherwise, UE 202 considers the service request as not received (R) by AN 204.

After setting up the user plane radio resources, the uplink data from the UE 202 can now be redirected (6416) to the (R)AN 204. The 5G RAN 204 sends the uplink data to the UPF address 212 and the tunnel ID provided in steps (6408) and ( 6410). If the (R) AN 204 receives at least one QoS flow, a message from the (R) AN 204 may send to the AMF 218 an N2 request ACK (6418) that includes an N2 reject ACK (including the session ID of the PDU, N2 SM information such as (R)AN tunnel information (list of accepted QoS flows for activated PDU sessions and list of rejected QoS flows for activated PDU sessions). Message (6418) may include SM N2 information element(s), such as RAN tunnel information. The (R)AN 204 may send N2 SM information in separate N2 messages, such as an N2 tunnel setup response, if the AMF 224 sends separate N2 messages in step (6412). If the N2 request message (6412) contains multiple N2 SM information elements, the N2 request ACK (6418) may include multiple N2 SM information elements and information to allow the AMF 218 to associate responses with the corresponding SMFs 220. If the (R)AN 204 does not receives the PDU session, the (R)AN 204 may send an N2 request ACK message (6418) that indicates to the AMF 218 that the N2 SM request was not received and a reason code. Message (6418) may include a PDU session identifier, N2 SM information (including PDU session rejection, and a reason code).

The AMF 218 may send an SMF N11 message (6420) that includes the PDU session ID, N2 SM information such as RAN tunnel information, and RAT type for each received PDU session to the SMF 220. If the AMF 218 has received the N2 SM information (one or more elements) in step (6418), then the AMF 218 forwards the N2 SM information to the corresponding SMF 220. If the UE time zone has changed from the last reported UE time zone, the AMF 218 pads the UE time zone IE in this message (6420 ). If a PDU session is received and if a dynamic PCC is deployed, the SMF 220 may further initiate an IP-CAN session change (6422) and provide new location information to the PCF 222. The SMF 220 may send a session update request message (6424) to the UPF 212 N4, containing information about the RAN tunnel. If the user plane needs to be set up or changed, SMF 220 initiates the N4 session change procedure and provides information about the RAN tunnel. The UPF 212 may then send an N4 session update response message (6426) to the SMF 220. SMF 220 may then send an AMF ACK (6426) N11 message. Message (6426) may include a PDU session ID and a PDU session state. The SMF 2225 may indicate the PDU session state (activated or deactivated) for the AMF 218.

A UE-initiated service request in the CM-CONNECTED state procedure may be used by the 5G UE 202 in the CM-CONNECTED state to request the establishment of user plane resources for PDU sessions. The network may take additional action if the user plane resource establishment was not successful. It should be noted that the procedure shown in FIG. 77 does not apply to the access network (when the UE 202 is registered with the network), in which the UE 202 is always considered to be in the CM-CONNECTED state, and in which the user plane resource is always considered to be set for the active session PDU.

FIG. 65 illustrates in a message processing flowchart an example of a late path switching procedure (6500) triggered by DL data without relocating the UPF 212, in accordance with embodiments of the present invention. This procedure (6500) may be used to trigger a path switch update when DL data arrives at UPF 212 and UPF 212 has no DL tunnel information. UPF 212 receives downlink data packets (6502) from DN 208. If N3 tunnel (R) AN information is not available, UPF 212 sends an N4 message NL message (6504) data notification message to SMF 220. Message 6504) includes a UE ID (such as SUPI) and the session ID of the PDU. The SMF 220 sends an acknowledgment message (6506) of the data DL notification to the UPF 212. Alternatively, the acknowledgment (6506) may be performed by the transport network message protocol.

If the connection state N3 is currently set to N3_DISCONNECTED, the SMF 220 sends N11 an information request message (6508) (R)AN to the AMF 218. The message (6508) includes a UE identifier (such as SUPI), a PDU session identifier, and an SM message. N2 including CN tunnel information (such as UPF address and UPF tunnel endpoint identifier N3) to (R)AN 204. AMF 218 sends N2 an (R)AN Path Switch Notify (6510) message that includes session identifier PDU and SM message N2. (R) AN 204 updates CN tunnel information. The (R)AN 204 sends an N2 message path switch notification acknowledgment message (6512) to the AMF 218. The message (6512) includes the PDU session ID and (R)AN tunnel information such as (R)AN address and endpoint ID tunnel. The AMF 218 sends N11 a RAN Information Response Message (6514) message to the UPF 212. The message (6514) includes a UE identifier (such as SUPI), a PDU session identifier, and tunnel information (R)AN, which includes a type (R) AN, N3 (R)AN address, and N3 tunnel endpoint ID. AMF 218 changes the session PDU connection state N3 to N3_CONNECTED.

SMF 220 sends N4 session change request message (6516) to UPF 212. Message (6516) includes UE identifier (such as SUPI), PDU session identifier and (R)AN N3 tunnel information such as (R)AN address N3 and downlink tunnel endpoint identifier. UPF 212 updates the (R)AN tunnel information for the requested session PDU. The UPF 212 sends N4 a session change response message (6518) to the SMF 220. The message (6518) includes a UE ID and a PDU session ID. The SMF 220 changes the session PDU connection state N3 to N3_CONNECTED. UPF 212 may send downlink data packets to UE 202 via (R)AN 204 before or after steps (6516) and (6518).

FIG. 66 illustrates in a message processing flowchart an example of a late path switch procedure (6600) triggered by UL data with UPF 212 reselection, in accordance with embodiments of the present invention. This procedure (6600) may be used to initiate a path switch update when the UE 202 requests to send UL data. UPF 212 may or may not be reselected. This procedure (6600) can be divided into two procedures: one for late path switching triggered by uplink data, as defined in FIG. 57, and one for moving the UPF 212, as defined in FIG.

The UE 202 sends a UL Data Bearer Grant Request message or a UL Data Packet (6602) to the (R)AN 204 for the session PDU. If UPF N3 tunnel information is not available at (R)AN 204, (R)AN 204 sends N2 a session path switch request message (6604) to AMF 218. The message (6604) includes a PDU session identifier and (R)AN tunnel information , such as the (R)AN address and tunnel endpoint ID of the (R)AN N3. The AMF then sends a session path switch request (6606) message to the SMF 220 including the UE identifier (such as SUPI), the PDU session identifier, and (R)AN tunnel information such as (R)AN type, N3 address (R) AN and Downlink Tunnel Endpoint ID.

The SMF 220 selects the target UPF 212t to serve the PDU session based on the criteria in clause 6.3.3 of TS 23.502 (6608). SMF 220 assigns N3 tunnel information such as N3 uplink tunnel endpoint ID. The SMF 220 sends N4 a session establishment request message (6610) to the target UPF 212t. Message (6610) includes a PDU session ID, QoS policy, charging policy, and (R)AN tunnel information. The (R)AN tunnel information may include an (R)AN address, a downlink tunnel endpoint ID, and N3 and N9 downlink tunnel information such as a binding UPF address and an N9 downlink tunnel endpoint ID. The target UPF 212t updates the (R)AN tunnel information and the anchor tunnel information UPF 212a. The target UPF 212t sends N4 a session establishment response message (6612) to the SMF 220. The message (6612) includes a UE identifier (such as SUPI) and a session PDU identifier.

The SMF 220 sends N4 a session change request message (6614) to the anchor UPF 212a (such as the session anchor UPF). Message (6614) includes a UE identifier (such as SUPI) and N9 UPF target tunnel information such as a UPF target address and an N9 uplink tunnel endpoint identifier. The binding UPF 212a updates the tunnel information of the target UPF. Anchor UPF 212a sends N4 session change response (6616) message to SMF 220. SMF 220 sends N11 session path switch response (6618) message to AMF 218. Message (6618) includes UE identifier (such as SUPI), PDU session identifier and an SM N2 message that includes N3 CN tunnel information for the (R)AN 204. SMF 220 changes the session PDU connection state N3 to N3_CONNECTED. SMF 220 starts the timer to be used in step (6624).

The AMF 218 sends a Session Path Switch Response (6620) message to the (R) AN 204 that indicates that the path switch is complete. The message (6620) includes the PDU session identifier and the N2 SM message received from SMF 220. AMF 218 changes the session PDU connection state N3 to N3_CONNECTED. (R)AN 204 updates the CN tunnel information and sends uplink data packets (6622). Once the timer set in step (6618) expires, the SMF 220 sends a session end request message (6624) to the source UPF 212s. Message (6624) includes a UE identifier (such as SUPI) and a PDU session identifier. The original UPF 212s remove the PDU context. Source UPFs 212s send N4 a session end response message (6626) to SMF 220.

FIG. 67 illustrates in a message processing flowchart an example of a late path switching procedure (6700) triggered by DL data with UPF 212 reselection, in accordance with embodiments of the present invention. This procedure (6700) may be used to switch the late path triggered by DL data entering the UPF 212. First, the CN performs the path switch procedure without reselecting the UPF 212. Thereafter, if the SMF 220 determines that the UPF 212 should be moved, the SMF 220 performs the UPF 212 reselection procedure.

Session anchor UPF 212a sends downlink data packets (6702) to source UPF 212s. Steps (6504) - (6520) of the late path switching procedure (6500) initiated by the DL data without reselecting the UPF 212 are then performed. The SMF 212 selects a new UPF 212 (6704). If a new UPF 212 is selected (6704), a UPF 212 reselection procedure (6800) is performed.

FIG. 68 illustrates in a message processing flowchart an example of a UPF 212 reselection procedure (6800) in accordance with embodiments of the present invention. This procedure (6800) may be used to establish a new UPF 212 that terminates the N3 connection. The SMF 220 selects the target UPF 212t to serve the PDU session based on the criteria in 6.3.3 of TS 23.502. SMF 220 assigns N3 tunnel information (such as N3 uplink tunnel endpoint ID) and N9 tunnel information (such as N9 anchor UPF address and N9 uplink tunnel endpoint ID). The SMF 220 sends N4 a session establishment request message (6802) to the target UPF 212t. Message (6802) includes the PDU session ID, QoS policy, charging policy, and (R)AN tunnel information such as (R)AN address, downlink tunnel endpoint ID, and N3 and N9 tunnel information. Target UPF 212t updates tunnel information (R)AN, N3 and N9. The target UPF 212t sends N4 a session establishment response message (6804) to the SMF 220. The message (6804) includes a UE identifier (such as SUPI) and a PDU session identifier.

The SMF 220 sends N4 a session change request message (6806) to the anchor UPF 212a (such as the session anchor UPF). Message (6806) includes a UE identifier (such as SUPI) and UPF N9 target tunnel information such as a UPF target address and an N9 downlink tunnel endpoint identifier. The anchor UPF 212a updates the tunnel information of the target UPF 212t. Anchor UPF 212a sends N4 a session change response message (6808) to SMF 220. Anchor UPF 212a may send downlink data (6810) to UE 202 via target UPF 212t. The SMF 220 sends an SM session change request message (6812) to the (R)AN 204 using the AMF messaging service 218. The message (6812) to the AMF 218 includes a UE identifier (such as SUPI) and an SM session change request message N2 to the (R)AN 204, which includes the PDU session ID and N3 tunnel information (such as the UPF address and the tunnel endpoint ID. The (R)AN 204 stores the N3 tunnel information and sends a session change response message (6814) to the SM to SMF 220 via AMF 218. Message 6814 includes a PDU session ID AMF 218 adds a UE ID (such as SUPI) and forwards N2 an SM session change response message to SMF 220. UE 202 and (R)AN 204 can send UL data (6816) to destination UPF 212t and anchor UPF 212a SMF 220 sends N4 session end request messages (6818) S4 to source UPF 212. Source UPF 212 sends N4 session end response message to SMF 220.

If a UE N2 context release request is made immediately after the SMF 220 deactivates the session PDU, the (R)AN 204 may release the N3 interface and radio interface information (including Uu) before the UPF 212 receives an instruction from the SMF 220 to start packet buffering downlink. Thus, it is possible that the UPF 212 may forward some downlink packets to the (R) AN 204 where the (R) AN 204 does not have UE context information. Therefore, the (R)AN 204 may drop these packets, which may result in the loss of important information when the packets are dropped and/or incorrect billing because the UPF 212 does not know that the packets have been dropped. To avoid this situation, AMF 218 may collect all responses from SMFs 220 confirming that the session deactivation has been completed before requesting the (R)AN 204 to release the UE context.

FIG. 69 illustrates in a message processing flowchart an example of a procedure (6900) for releasing a UE context in an AN in accordance with embodiments of the present invention. This procedure (6900) may be used to release the N2-AP (application protocol) signaling logical connection and associated user plane N3 connections. When the N2-AP signaling connection is lost due to failure of the (R)AN 204 or AMF 218, the UE context release in the AN procedure (6900) may be performed locally by the AMF 218 or (R)AN 204 as described in the procedure flow below without using or not relying on any signaling shown between (R)AN 204 and AMF 218. The release of the UE context in the AN procedure (700) may result in the deactivation of all UE 202 PDU sessions.

UE context release triggering in AN procedure (6900) can be (R)AN triggered due to, for example, O&M interference, unspecified failure, AN link failure (e.g., radio), user inactivity, due to release to UE-generated disconnect (6902a) alarm connections, etc. Procedure initiation (6900) may also be initiated by AMF (6902b) due to, for example, an unspecified failure, etc. In FIG. 69 shows both (R)AN initiated and AMF initiated UE context release steps in the AN procedure (6900).

If there are acknowledged AN conditions (eg, radio link failure) or for other (R AN 204 internal reasons), (R)AN 204 may initiate UE context release in AN procedure (6900). In this case, (R)AN 204 sends N2 a message request (6902b) to release the UE context in AMF 218. The message may include a reason (or reason code) that indicates (or represents) the reason for the release (e.g., AN connection failure, O&M intervention, unspecified failure, etc.). ) UE context release triggering in AN procedure (6900) can also be triggered by AMF internal event 218.

AMF 218 may send one message to each SMF 220 serving multiple activated PDU sessions to request deactivation of those PDU sessions. For each of the SMFs serving activated PDU sessions, AMF 218 may request SMF 220 to deactivate PDU sessions: AMF 218 may send N11 a request message (6904) to deactivate PDU session to SMF 220. Message (6904) may include a UE identifier ( such as SUPI), the (R) AN identifier (such as the (R)AN address), and the release reason (or reason code). AMF 218 may also store the deactivated session state of the PDU. It is noted that this step (6904) can also be performed via the AMF service: Namf_UE Mobility Event Notification (SMF). In this case, the AMF 218 may send (via an N11 message) a UE mobility event notification that indicates an N2 release event to the SMF(s) 220 that serve the active session(s) of the UE 202 PDU, as defined in clause 5.2.2.2 TS 23.502. The message may include a UE identifier (such as SUPI), an (R)AN information identifier (such as an (R)AN address), and a reason code. The (R)AN information identifier may be used to distinguish between multiple (R)ANs in the case where the UE is connected to multiple (R)ANs.

The SMF 220 may then send a session change request message (6906a) to the UPF 212 N4. This message (6906a) may include AN tunnel information to be deleted. Thus, the SMF initiates an N4 session change procedure (6906a) indicating that the AN tunnel information needs to be deleted. The buffer command may indicate whether the UPF 212 should buffer the incoming DL PDU. Noted that the request (6906a) includes a "buffer command", then the UPF 212 may start buffering the downlink PDUs received for the UE 202 and initiate the "network initiated service request" procedure described in clause 4.2.3.3 of TS 23.502 if a downlink PDU arrives for a session PDU. The UPF 212 may then send an N4 session response message (6906b) to the SMF 220 acknowledging the request to the SMF 220. The SMF 220 may store the deactivated state of the session PDU.

The SMF 220 may then send a PDU session deactivation response message (6908) to the AMF 218 N11. It should be noted that this step (6908) can also be implemented using the SMF service: Nsmf_PDU Session Event Report Notification (AMF). The SMF 220 may send (via an N11 message) a Session Event Report Notification PDU as defined in clause 5.2.8.1 of TS 23.502. The notification may include a UE identifier (such as SUPI), PDU session identifier(s), and an event trigger (such as deletion of (R)AN tunnel information). After the AMF 218 collects all PDU session deactivation responses in step (6908) from the SMF(s) 220 that were notified in step (6904), the AMF 218 may send a request message (6910) to the (R)AN 204 N2 releasing the UE context.

If the AN connection (eg, RRC connection) with UE 202 has not yet been released (step 6902a), (R)AN 204 requests UE 202 to release the AN connection (6912). Upon receiving the AN connection release acknowledgment from the UE 202, the (R)AN 204 may delete the UE context. The (R)AN 204 may acknowledge the release of N2 by returning the N2 UE context release complete message (6914) to the AMF 218. This releases the signaling connection between the AMF 218 and the (R)AN 204 for that UE 202. It should be noted that during this procedure, the AN may provide location information to the AMF 218.

The session PDU release procedure may be used to release all resources associated with the session PDU. Such resources may include the IP address/prefixes allocated to the IP-based PDU session, which may include releasing multiple prefixes in case of multihoming (as defined in TS 23.501). Such resources may also include any UPF 212 resource (including the N3/N9 termination) that was used by the PDU session. SMF 220 may notify any entity associated with the session PDU that the session PDU has been released. Such entities include PCF 222 and DN 208 (eg, when DN 208 authorization took place during PDU session establishment).

In some implementations, for deactivated session PDUs, SMF 220 may send an Asynchronous Session Release (ASR) flag and PDU session identifier to inform AMF 218 of the session release request and indicate whether the session PDU should be released or not. The procedure can be executed asynchronously. If the ASR flag is set to FALSE, the PDU session may be canceled immediately, regardless of the CM state of the UE 202. If the ASR flag is set to TRUE, the PDU session release may be performed when the UE 202 is in the CM-CONNECTED state. In the message from SMF 220 to AMF 218, the ASR flag and PDU session ID may be added according to the following:

• for an activated session PDU, if the UE 202 is in the CM-

CONNECTED, the session PDU may be released immediately. Therefore, the SMF 220 does not need to send an ASR indication to the AMF 218.

• for a deactivated session PDU, SMF 220 may send an ASR flag and

the PDU session identifier in the message in the AMF 218. If the ASR flag is set to FALSE, the AMF 218 may send N1 SM (session PDU release request) information to the UE 202 immediately. If the UE 202 is in the CM-IDLE state, the AMF 218 may send a request to the UE 202 to enter the CM-CONNECTED state. If UE 202 receives the paging message, AMF 218 may send SM N1 (session release request PDU) information to UE 202. If UE 202 is unable to paging, AMF 218 may send an "undelivered error message" to SMF 220 with a reason code (eg, UE not available). SMF 220 and AMF 218 may then release the session PDU. The session state in AMF 218 and UE 202 may be synchronized when UE 202 performs service request or registration procedures. If the ASR flag is set to TRUE, the PDU session at UE 202 may be released if UE 202 is in the CM-CONNECTED state. If UE 202 is in the CM-IDLE state, the PDU session state at UE 202 and CN 206 may be synchronized when UE 202 performs service request or registration procedures.

FIG. 70 illustrates in a message flow diagram an example procedure for a requested UE 202 or CN 206 to release a non-roaming and break-local roaming (7000) PDU session in accordance with embodiments of the present invention. 70 illustrates both the PDU session release procedure requested by the UE and the PDU session release procedure requested by the network. The procedure (7000) allows UE 202 to request the release of one session PDU. The procedure (7000) also allows SMF 220 or PCF 222 to initiate release of the session PDU. In the case of local interruption (LBO), the procedure (7000) is the same as in the case of no roaming, with the difference that SMF 220, UPF 212 and PCF 222 are located in the visited network.

The procedure (7000) may be initiated by the UE 202, the PCF 222, or the SMF 220. The UE 202 may initiate the procedure (7000) by sending an N1 SM PDU Session Release Request message (7002a) to the SMF 220. The message (7002a) may include a session identifier PDU and may be relayed by the (R)AN 204 to the AMF 218 corresponding to the session ID of the PDU via the N2 interface, and relayed by the AMF 218 via the N11 interface to the SMF 220. Depending on the access type, when the UE 202 is in the CM-IDLE state, the UE 202 may initiate a service request procedure before being able to release the session PDU. The PCF may initiate a procedure (7000) by initiating a PDU-CAN session change procedure (7002b) to request a PDU session release. The SMF 220 may initiate a procedure (7000) by releasing the session PDU (7002c), for example, based on a request from DN 208 (eg, deauthorize UE 202 to access DN 208) or based on a request from UDM (eg, change subscription) or from the real-time charging system (OCS). The release procedure (7002c) may also be initiated based on local policy. For example, the release procedure (7002c) may be associated with moving the UPF 212 for Mode 2/Mode 3 Session and Service Continuity (SSC). If the SMF 220 receives one of the triggers in steps (7002a) through (7002c), the SMF 220 may begin a session PDU release procedure (7000).

The SMF 220 may release the IP address/prefix(es) that have been allocated for the session PDU and may also release the corresponding user plane resources. SMF 220 may send N4 a session release request message (7004a) to UPF 212. The message (7004) may include an N4 session identifier. UPF 212 may discard any remaining session PDUs and release all tunnel resources and contexts associated with session N4. UPF 212 may acknowledge the N4 session release request by sending N4 a session release response message (7004b) to SMF 220. The message (7004b) may include an N4 session identifier. If there are multiple UPFs 212 associated with a session PDU, steps (7004a) and (7004b) may be performed for each UPF 212. If dynamic PCC is applied to this session, SMF 220 may initiate a PDU-CAN session release procedure (7006). If this is the last PDU session that SMF 220 processes for UE 202, SMF 220 may release the association with the UDM.

The SMF 220 may send an N11 request message (7008) to the AMF 218. The message (7008) may include an N2 SM resource release request and N1 SM information such as a PDU session release command. SMF 220 may generate SM N1 information including a PDU session release command message that includes the PDU session ID and a reason (or reason code). The cause may indicate a trigger to establish a new PDU session with the same characteristics (eg, when procedures associated with SSC mode 2 are called). It should be noted that SSC mode 2 is defined in clause 5.6.9 of TS 23.502.

Some implementations use the "ACM" asynchronous communication type indication, as described below. If the PDU session UP connection is active, SMF 220 may also generate an SM N2 request to release the (R)AN 204 resources associated with the session PDU. This N2 SM request may include an N2 resource release request that includes the session ID of the PDU. SMF 220 may send an N11 message (7008) to AMF 218. Message (7008) may include an N2 SM resource release request and an N1 SM container that includes a session PDU release command. If the session PDU is deactivated, the "ACM" indication indicates to the AMF 218 whether it can skip sending the N1 SM container to the UE 202 (eg, when the UE 202 is in CM-IDLE mode). If the UE 202 is in the CM-IDLE state and an "ACM" indication is included in the N11 message, steps (7010) - (7014) may be skipped. Otherwise, if the UE 202 is in the CM-IDLE state and "ACM" is not specified, the AMF 218 may initiate a network-initiated service request procedure to send the N1 SM information to the UE 202. If the UE 202 is in the CM-CONNECTED state, then the AMF 218 may send the message received from the SMF 218 in step (7008) to the (R)AN 204. This may be done by sending the SM N2 resource release request message (7010) to the (R)AN 204, where the message (7010) ) may include N1 SM information. It should be noted that the UE 202 and the 5G core network (eg, CN 206) will be synchronized with respect to the status (eg, released) of the session PDU at the next service request or registration procedure. When the (R)AN 204 has received the N2 SM request (7010) to release the AN resources associated with the session PDU, the (R)AN 204 provides a dedicated signaling exchange (7012) with the UE 202 to release the corresponding AN resources. In the case of a 3GPP RAN, an RRC connection may be reconfigured with the UE 202 releasing the resources (R) of the AN 204 related to the session PDU. During this procedure, the (R)AN 204 may send any NAS message (such as an N1 SM PDU session release command) received from the AMF 218 in step (7010). The UE 202 may acknowledge the session PDU release command by sending a session PDU release ACK message (7012) via the N1 SM signaling sent by the (R)AN 204. If the (R)AN 204 received the N2 SM request (7010) to release the AN resources, ( The R)ANs 204 may acknowledge the N2 SM resource release request by sending an N2 SM resource release ACK message (7014) to the AMF 218. The message (7014) may include N1 SM information that includes a session PDU release acknowledgment. Otherwise, the (R)AN 204 may forward the N1 SM information, which includes the session PDU release ACK, from the UE 202 to the AMF 218. If the UE 202 is in the CM-CONNECTED state, the AMF 218 may send the N11 response message (7018 ) to the SMF 220. The message (7018) may include N1 SM information that includes a session PDU release acknowledgment. Otherwise, if the UE 202 is in the CM-IDLE state, the AMF 218 may notify the SMF 220 of the undelivered N1 SM with a reason code indicating that N2 has been released, or the UE 202 is in the CM-IDLE state.

Other implementations use the Asynchronous Session Release (ASR) flag along with the session ID of the PDU, as described below. If the PDU session UP connection is active, SMF 220 may also generate an SM N2 request to release the (R)AN 204 resources associated with the PDU session. This N2 SM request may include a (R)AN resource release request that includes a PDU session ID. SMF 220 may send an N11 message (7008) to AMF 218. Message (7008) may include an N2 SM resource release request and an N1 SM container (which includes a session PDU release command). The N11 message (7008) may further include an ASR flag and a PDU session identifier. The ASR flag may provide the AMF 218 with an indication of the session release notification and whether it may send the N1 SM container to the UE 202 (eg, when the UE 202 is in CM-IDE mode). If the UE 202 is in the CM-IDLE state and the ASM flag is set to TRUE in message N11, the AMF confirms that steps (7010) - (7014) can be skipped. Otherwise, if UE 202 is in the CM-IDLE state and the ASR flag is set to FALSE, AMF 218 may initiate a network-initiated service request procedure to send N1 SM information to UE 202. If UE 202 receives paging, AMF 218 may send to the UE 202 SM N1 information (including a session PDU release request). The paging message may also carry SM N1 information (including a session PDU release request). If the UE is unable to paging, the AMF 218 may send an "Undelivered Error Message" to the SMF 220 with a reason indicating that the UE is not available at step (7018). If the UE 202 is in the CM-CONNECTED state, then the AMF 218 may send the message received from the SMF 218 in step (7008) to the (R)AN 204. This may be done by sending N2 a resource release request message (7010) to the SM in (R)AN 204, where the message (7010) may include N1 SM information. It should be noted that the UE 202 and the 5G core network (eg, CN 206) will be synchronized with respect to the status (eg, released) of the session PDU at the next service request or registration procedure. When the (R)AN 204 has received the N2 SM request (7010) to release the AN resources associated with the session PDU, the (R)AN 204 exchanges special signaling (7012) with the UE 202 to release the corresponding AN resources. In the case of a 3GPP RAN, an RRC connection may be reconfigured with the UE 202 releasing the (R)AN 204 resources related to the session PDU. During this procedure, the (R)AN 204 may send any NAS message (such as an N1 SM PDU session release command) received from the AMF 218 in step (7010). The UE 202 may acknowledge the session PDU release command by sending a session PDU release ACK message (7012) via the N1 SM signaling sent by the (R)AN 204. If the (R)AN 204 received the N2 SM request (7010) to release AN resources, (R) The ANs 204 may acknowledge the N2 SM resource release request by sending an N2 SM resource release ACK message (7014) to the AMF 218. The message (7014) may include N1 SM information that includes an acknowledgment of the session PDU release. Otherwise, the (R)AN 204 may forward the N1 SM information, which includes the session PDU release ACK, from the UE 202 to the AMF 218. If the UE 202 is in the CM-IDLE state and the ASR flag is set to TRUE in step ( 7008208) AMF 218 may acknowledge message SMF 220 (7008) and step (7018) is skipped. SMF 220 and AMF 218 may release the session PDU. The PDU session state at AMF 218 and UE 202 may be synchronized when service request or registration procedures are performed. If the UE 202 is in the CM-IDLE state and the ASR flag is set to FALSE in step (7008), the AMF 218 may not page the UE 202 and the AMF may send an Undelivered Error message that includes a session PDU release indication. , PDU session ID, and reason code (eg, UE not available). Step (7018) is skipped. SMF 220 and AMF 218 may release the session PDU. The session state in AMF 218 and UE 202 may be synchronized when UE 202 performs service request or registration procedures. Otherwise, AMF 218 may send a response message N11 to SMF 220, the message including N1 SM information (such as a session PDU release ACK).

In still other implementations using the session release hint, it is used as described below. If the session PDU is deactivated, SMF 220 may send a session release indication and PDU session identifier to AMF 218. SMF 220 may send an N11 message (7008) to AMF 218. Message (7008) includes N2 SM resource release request, SM container N1 ( including a PDU session release command), a PDU session release indication, and a PDU session identifier. The N2 SM resource release request message may include an N1 SM container. The session PDU release indication indicates the session PDU release notification AMF 218 . If the PDU session is deactivated, the SMF may indicate a PDU session release indication and PDU session ID in message 7008. AMF 218 may send an N1 SM container to UE 202 when UE 202 is in the CM-IDLE state. If UE 202 is in the CM-IDLE state, AMF 218 may acknowledge step (7008) at step (7018) and steps (7010) - (7014) and (7018) are skipped. AMF 218 may release all PDU session contexts. It should be noted that the UE 202 and the 5G core network, AMF 218, 206, will be synchronized with respect to the status (eg, released) of the session PDU at the next service request or registration procedure. If the UE 202 is in the CM-CONNECTED state, the PDU session release indication and the PDU session identifier are not contained in the message in step (7008), then the AMF 218 may transmit the message received from the SMF 220 in step (7008). If the (R) AN 204 receives the N2 SM Resource Release Request message (7010) to release the AN resources associated with the session PDU, a special signaling exchange (7012) may be provided with the UE 202 to release the corresponding AN resources. In the case of a 3GPP RAN, an RRC connection may be reconfigured with the UE 202 releasing the (R)AN 204 resources related to the session PDU. During this procedure (7000), the (R)AN 204 may send any NAS message (eg, N1 SM PDU session release command) received from the AMF 218 in step (7010). If the (R)AN 204 only receives the N1 SM container (including the session PDU release command), the (R)AN 204 may forward this message to the UE 202. The UE 202 acknowledges the session PDU release command by sending a session PDU release ACK message via N1 SM signaling sent via the (R)AN 204. If the (R)AN 204 has received the N2 SM request to release the AN resources, the (R)AN 204 may acknowledge the N2 SM resource release request by sending the N2 SM Resource Release ACK message (7014) (including N1 SM information including PDU session release ACK) to AMF 218. Otherwise, (R)AN 204 may forward SM N1 information (including PDU session release) from UE 202 to AMF 218. If UE 202 is in CM-CONNECTED state, AMF 218 may send N11 a message (7018) to forward messages received from (R)AN 204 in step (7014) to SMF 220. If UE 202 is in CM-IDLE state, AMF 218 may send message N11 to SMF 220 (including session messages, an acknowledgment, and an identifier for the PDU session, such as the PDU's session identifier). SMF 220 may release all PDU session contexts and step (7018) is skipped.

SMF 220 may notify AMF 218 that a session PDU is being released via an N11 message (7018). AMF 218 and SMF 220 may remove all contexts (including the PDU session ID) associated with the PDU session. An example for step (7018) could be an SMF 220 sending an AMF 218 via message N11 a session event message notification PDU as defined in 5.2.8.1 of TS 23.502. In this example, the event trigger is a session PDU release. It should be noted that in some embodiments, the order in which SMF 220 releases resources may be implementation dependent.

In another example of session PDU release procedure (7000), SMF 220 knows the UE's connection management (CM) state (eg, CM-IDLE or CM-CONNECTED). The SMF 220 serving the PDU session subscribes to the Mobility Event Notification Service of the UE AMF 218. When the UE changes the state of the CM, the AMF 218 may notify the SMF 220.

If the session PDU is activated, at step (7008), SMF 220 sends N11 a request message to AMF 218. The message includes an N2 SM resource release request and N1 SM information (including a session PDU release command). SMF 220 generates SM N1 information including a PDU session release command message (which includes the PDU session ID and reason). The cause may indicate a trigger to establish a new PDU session with the same characteristics (eg, when procedures associated with SSC mode 2 are called).

If the PDU session is deactivated (UP deactivated) and the UE 202 is in the CM-IDLE state, at step (7008), the SMF 220 sends N11 a request message to the AMF 218. The message includes a PDU session release indication and a PDU session identifier.

In step (7010), if the UE 202 is in the CM-CONNECTED state, the AMF 218 forwards the message received in step (7008) to the (R)AN 204 via the N2 interface. If the UE 202 is in the CM-IDLE state, steps (7010) - (7012) and (7018) are skipped. AMF 218 releases all PDU session contexts locally. The session state of the PDU in UE 202 and in the 5G core network (such as AMF 218) are synchronized in the next service request or registration procedure.

In step (7012), if the (R)AN 204 receives a request N2 SM to release the (R)AN resources associated with the session PDU, then generate an (R)AN special signaling exchange with the UE 202 to release the corresponding (R)AN resources. In the case of 3GPP (R) AN 204, RRC connection reconfiguration may take place when UE 202 releases (R) AN 204 resources related to the session PDU. During this procedure (R), the AN 204 sends any NAS message (eg, N1 SM PDU session release command) received from the AMF 218 in step (7010).

In step (7012), if the (R)AN 204 only receives the N1 SM information, the (R)AN 204 forwards this message to the UE 202. The UE 202 acknowledges the session PDU release command by sending a session PDU release acknowledge message via the N1 SM signaling sent via (R)AN 204.

In step (7014), if the (R) AN 204 has received the (R) AN resource release request N2 SM in step (7010), the (R) AN 204 acknowledges the N2 SM resource release request by sending an N2 SM resource release acknowledgment (including reporting SM N1 session PDU release acknowledgment information) to AMF 218. Otherwise, if (R)AN 204 received only SM N1 information in step (7010), (R)AN 204 may forward SM N1 information (session PDU release acknowledgment) from UE 202 to AMF 218.

In step (7018), if the UE 202 is in the CM-CONNECTED state, the AMF 218 sends a response message N11 to forward the message received from the (R)AN 204 in step (7014) that includes N1 SM information (including acknowledge session PDU release), in SMF 220.

In step (7018), if UE 202 is in the CM-IDLE state, AMF 218 sends an N11 message (including PDU session release confirmation and PDU session ID) to SMF 220 in response to SMF 220 message in step (7008). Step (7018) is skipped. SMF 220 releases all session PDU contexts of the released session PDU.

At step (7018), SMF 220 notifies AMF 218 that the PDU session has been released. AMF 218 and SMF 220 may remove all contexts (including the PDU session ID) associated with the PDU session.

FIG. 71 illustrates in a message processing flowchart an example procedure for a requested UE 202 or CN 206 to release a session PDU for roaming (7100) with home routing in accordance with embodiments of the present invention. This procedure (7100) is used in case of home routing roaming. Some of the steps in releasing a session PDU for a roaming with home routing procedure (7100) are similar to those for releasing a session PDU for a procedure (7000) without roaming and roaming with local interruption.

The session PDU release for home routed roaming procedure (7100) may be initiated by UE 202, PCF 222, or SMF at HPLMN (H-SMF) 220h. The UE 202 may initiate a procedure (7100) by sending an SM PDU Session Release Request message (7102) to the AMF 220. The message (7102) may include a PDU session identifier and may be relayed (7104) to the SMF in the VPLMN (V-SMF) 220v corresponding to the PDU session ID via N11 and AMF 218. Then, V-SMF 220v may send a session PDU release request message (7106), depending on the access type, when the UE 202 is in the CM-IDLE state, the UE 202 may initiate a request procedure service before it can release the session PDU. The PCF 222 may initiate a procedure (7100) by initiating a PDU-CAN session change procedure (7108) to request a PDU session release. H-SMF 220h may initiate a procedure (7100) by releasing a session PDU (7110) as described above in step (7002c) of FIG. If H-SMF 220 receives one of the triggers in steps (7106) - (7110), H-SMF 220 may start a session PDU release procedure (7100).

H-SMF 220 may release the IP address/prefix(es) that have been allocated for the session PDU and may also release the corresponding user plane resources. H-SMF 220 may send an N4 session release request message (7112a) to UPF 212. The message (7112a) may include an N4 session identifier. UPF 212 may discard any remaining session PDUs and release all tunnel resources and contexts associated with session N4. The UPF 212 may acknowledge the N4 session release request by sending an N4 session release response message (7112b) to the H-SMF 220. The message (7112b) may include an N4 session identifier. If there are multiple UPFs 212 associated with a PDU session, steps (7112a) and (7112b) may be performed for each UPF 212. If dynamic PCC is applied to this session, then the H-SMF 220 may initiate a PDU-CAN session termination procedure (7114). . If this is the last session PDU that H-SMF 220 processes for UE 202, H-SMF 220 may release the association with the UDM.

The H-SMF 220h may then send a session PDU release command message (7116) to the V-SMF 220v. This message (7116) may include a permanent subscriber identification, a PDU session identifier, and a NAS message. The V-SMF 220v may then release the appropriate user plane resources using steps (7118a) and (7118b). This may include the same procedure as steps (7112a) and (7112b), but controlled from the SMF in the VPLMN (V-SMF 220v). Steps (7120) - (7130) are the same as (7008) - (7018) as described above with reference to FIG. 70 with the SMF being H-SMF 220h. The V-SMF 220v may then send a session PDU release confirmation message (7132) to the H-SMF 220h. Message (7132) may include a permanent identification of the subscriber and a PDU session identifier. H-SMF 220h may remove all contexts associated with the session PDU.

FIG. 72 illustrates in a message flow diagram an example of an Xn-based inter-NG(R) AN handover procedure (7200) without moving a user plane function, in accordance with embodiments of the present invention. This procedure (7200) may be used to handover the UE 202 from the source (R) AN 204 to the destination (R) AN 204t using the Xn interface when the AMF 218 does not change and the SMF 220 decides to keep the existing UPF 212 (e.g., UPF 212, which terminates the N3 interface in the NG core network (NGC) Assuming an IP connection between the source UPF 212 and the target UPF 212.

The procedure (7200) includes preparing (7202) a handover and performing (7204) a handover. Performing (7204) handover includes forwarding data (7206) from source (R)AN 204s to target (R)AN 204t. Target (R)AN 204t may send a path switch request message (7208) N2 to AMF 218 that includes an indication that UE 202 has moved to a new target cell and a list of session PDUs to be switched. Depending on the target cell type, the target (R)AN 204t inserts the appropriate information into this message. For QoS flows to be switched to the target (R) AN 204t, the N2 Path Switch Request message (7208) may include a list of received QoS flows.

AMF 218 may send N2 SM information via N11 message (7210) to each SMF 220 associated with the list of PDU sessions and the list of received QoS flows of each PDU session received in the N2 Path Switch Request (72080). For PDU sessions to be switched to the target (R) AN 204t, upon receipt of the N11 message (7210), each of the SMFs 220 may determine whether the existing UPF 212 can continue to serve the UE 202. If the existing UPF 212 cannot continue to serve the UE 202 , and is not a PDU session binding, follow steps 3-11 of clause 4.9.1.2 of TS 23.502 (version 0.3.0 published March 2017). Otherwise, each of the SMFs 220 may perform the following steps (7212) - (7220) if their existing UPFs 212 can continue to serve the UE 202. For activated PDU sessions that are not in the N2 path, in the Switch Request (7280) message The AMF 218 may send a separate request(s) to the appropriate SMF 220 to notify that the target (R) AN 204t does not support this PDU session.

For PDU sessions requested (accepted) by target (R)AN 204t, SMF 220 may send an N4 session change request message (7212) to UPF 212. Message (7212) may include the (R)AN address and tunnel identifiers for the user plane downlink. For PDU sessions rejected by target (R)AN 204t, SMF 218 may either unblock or deactivate the PDU sessions. To release PDU sessions, SMF 218 may initiate a session PDU release procedure as defined in 4.3.4 of TS 23.502. In order for PDU sessions to be deactivated, SMF 218 may send an N4 session change request (7212) to UPF 212 for these PDU sessions. Message (7212) indicates release of (R)AN N3 tunnel information such as (R)AN address and tunnel endpoint identifier for downlink user plane, buffering command and reactivation timer, and reason code (e.g., handover rejected or missing data activity). It should be noted that the buffering command may be used to indicate whether UPF 212 should buffer incoming downlink packets. It is also noted that the reactivation timer may indicate the duration that a deactivated PDU session UP remains in the deactivated state after UPF 212 clears N3 AN (R) tunnel information. Before the reactivation timer expires, UPF 214 may buffer the downlink packets in accordance with the buffer command. After the reactivation timer expires, UPF 212 may buffer the downlink packets in accordance with the buffer command. If UPF 212 receives downlink packets before or after the reactivation timer expires, UPF 212 may send a downlink packet notification to SMF 220 to initiate a network initiated service request.

The UPF 212 may return an N4 change response message (7214) to the SMF 220 after the requested session PDUs are switched or changed/deactivated. Message (7214) may include tunnel identifiers for uplink traffic. To assist the reordering function at the target (R) AN 204t for PDU sessions requiring a path switch, UPF 212 may send one or more "end marker" packets (7216) on the previously used path immediately after the path switch. UPF 212 may start sending downlink packets to target (R)AN 204t (7218). SMF 220 may send N11 an ACK message (7220) to AMF 218 for PDU sessions that have been successfully switched or deactivated. Message (7220) may include CN tunnel information and may indicate whether the (R)AN N3 tunnel information is updated for a PDU session to be switched over the UP channel or a PDU session is deactivated (UP deactivation, UP path released), for deactivated sessions The SMF PDU 220 may store the deactivation state of the deactivated session PDU. The N11 ACK message (7220) may include an SM N2 message to the (R)AN 204 to deactivate PDU sessions and a SM message container N1. The N2 SM message may include PDU session identifier(s). The message container SM N1 may include a session deactivation request that includes PDU session identifiers. It should be noted that if AMF 218 sends a session deactivate request to UE 202, then SMF only needs to inform AMF 218 of its session deactivation decision, and SMF 220 does not need to send an N1 SM message container to UE 202. It is also noted that step (7220) may occur at any time after the N4 session change response message (7214) is received in SMF 220.

It should be noted that for PDU sessions that the target (R)AN 204t rejects, the target (R)AN 204t may delete all PDU session contexts before sending a path switch request 7208 to the AMF 218. In this case. The N11 ACK message 7220 from SMF 220 to AMF 218 may include an N1 SM message to be forwarded only to UE 202.

Once the N11 ACK message (7220) is received from all SMFs 220, the AMF 218 may aggregate the received CN tunnel information from these responses and send this aggregated information as part of the N2 SM information in the N2 Path Switch Request ACK (7222) to the target (R) AN 204t. The message (7222) may include an indication for each PDU session as to whether the N3 connection is switched and a request to deactivate the N2 SM session and the N1 message container. If none of the requested PDP sessions were successfully switched, AMF 218 may send an N2 Path Switch Request Failure message to the target (R) AN 204t.

It should be noted that the AMF may collect an N11 ACK message (7220) from the SMF 220 that processes the path switch request and may send to the target (R) AN 204t in a separate message. This will reduce the handover time for received PDU sessions. AMF 218 may collect an N11 ACK message (7220) from SMF 220 for deactivated session PDUs and forward N2 SM session deactivation requests and N1 SM session deactivation requests in a separate message to target (R) AN 204t. AMF 218 may combine all N2 SM session deactivate requests in one message and send to target (R)AN 204t. AMF 218 may combine all N1 SM session deactivate requests in a single message and send to UE 202. The combined N2 session deactivate request may include a combined N1 SM session deactivate request.

At AMF 218, upon receipt of the N11 ACK message (7222), AMF 218 may maintain a deactivation state of deactivated PDU sessions, if any. It should be noted that if AMF 2204 sends a session deactivate request to UE 202, then AMF 218 may send an N1 MM message container (including a session deactivate request having a session ID PDU) to UE 202. If the target (R)AN 204t receives the request deactivating the N2 SM session in step (7222), the target (R)AN 204t may delete the PDU session context of the PDU sessions to be deactivated. The (R)AN 204 then forwards the SM N1 container (including the session deactivation request having the session ID PDU) to the UE 202 via an RRC message (7224). It should be noted that if AMF 218 sends a session deactivate request to UE 202 in step (7222), then (R)AN 204 may forward an N1 MM container (including a session deactivate request having a session identifier PDU) to UE 202 via an RRC message (7224). UE 202 may release the radio context of deactivated PDU sessions. The UE sends an RRC message (7226) that includes the N1 SM session deactivate response(s) to the SMF 220 for each of the N1 SM session deactivate request via the target (R)AN 204t (7228) and the AMF 218 (7230). It should be noted that if AMF 218 sends a session deactivate request to UE 202 in step (7224), then the UE sends one N1 MM session deactivate response (7228) to AMF 218 via target (R)AN 204t. By sending a resource release message (7332) to the source (R) AN 204s, the target (R) AN 204 confirms the success of the handover. Resource release is then initiated from the source (R)AN 204.

It should be noted that the target (R) AN 204t may send in message (7232) an SM N2 session deactivate response message to SMF 220 to acknowledge the release of PDU session contexts for deactivated PDU sessions. The SM N2 session deactivate response may include an SM N1 session deactivate response (7226) from UE 202.

It should be noted that the target (R)AN 204t may send message 7232 to source (R)AN 204s at any time after receiving message 7222 from AMF 218, such as before sending message 7224 to UE 202.

It should be noted that the SMF may decide to either release or deactivate the session PDU. In another embodiment, the SMF always deactivates PDU sessions that the target (R)AN rejects. In preparing (7202) for handover and performing (7204) handover, the target (R)AN may inform UE 202 of PDU sessions that are deactivated. SMF 220 should not send SM N1 session deactivate request to UE 202, but SM N2 session deactivate requests to target (R)AN 204t. Therefore, messages 7224 to 7230 are not needed.

It should be noted that in FIG. 72, PDU deactivation is triggered by PDU session rejection due to target (R)AN 204t not having enough resources. One of skill in the art can combine PDU session deactivation during handover due to session PDU inactivity in FIG. 63 and session PDU deactivation due to lack of resources at the target (R) AN in FIG. 72.

FIG. 73 illustrates in a message processing flowchart an example of an Xn-based inter-NG(R)AN handover procedure (7300) with user plane function movement according to embodiments of the present invention. Procedure (7300) may be used to handover UE 202 from source (R) AN 204s to destination (R) AN 204t using Xn when AMF 218 does not change and SMF 220 determines that source UPF 212s should be moved. The source UPF 212 is the UPF that terminates the N3 interface in the 5GC. IP connectivity is assumed between source UPF 212 and source (R) AN 204, and between target UPF 212t and target (R) AN 204t.

The procedure (7300) includes preparing (7302) a handover and performing (7304) a handover. Performing (7304) a handover includes sending data (7306) from a source (R) AN 204s to a target (R) AN 204t. Target (R) AN 204t may send downlink data (7308) to UE 202. UE 202 may send uplink data (7310). Target (R) AN 204t may send an N2 Path Switch Request message (7312) to AMF 218 that includes an indication that UE 202 has moved to a new target cell and a list of session PDUs to be switched. Depending on the target cell type, the target (R) AN 204t adds appropriate information to this message. For QoS flows to be switched to the target (R) AN 204t, the N2 path switch request message (7312) may include a list of received QoS flows.

AMF 218 may send N2 SM information via N11 message (7314) to each SMF 220 associated with the list of PDU sessions and the list of received QoS flows of each PDU session received in the N2 path switch request (7312). For PDU sessions to be switched to the target (R) AN 204t, upon receipt of the N11 message (7314), each of the SMFs 220 may determine whether the existing UPF 212 can continue to serve the UE 202. If the existing UPF 212 cannot continue to serve the UE 202 and is not a PDU session binding, steps 3-11 of clause 4.9.1.2 of TS 23.502 are performed. Otherwise, each of the SMFs 220 may perform the following steps (7316) - (7328) if their existing UPFs 212 can continue to serve the UE 202. AMF path switching 218 may send a separate request(s) to the corresponding SMF(s) 220 to notify that the target (R) AN 204t does not support this PDU session.

For PDU sessions to be switched, SMF 220 may then select a new target UPF 212t based on UPF selection criteria in accordance with clause 6.3.3 of TS 23.501. The assignment of the IP address to the target UPF and the allocation of downlink and uplink tunnel identifiers may be performed by SMF 220 (7316). An N4 session establishment request message (7318) (including the target RAN address and the uplink and downlink tunnel identifiers) may be sent to the target UPF 212t. Target UPF 212t may then send N4 a session establishment response message (7320) to SMF 220. SMF 220 may start a timer to be used in step (7336). The SMF 220 may then send an N4 session change message (7322) to the anchor session PDU 212a. Anchor session PDU 212a may respond with an N4 session change response message (7324). At this point, anchor session PDU 212a may begin sending downlink packets (7326) to target (R)AN 204t using the address and tunnel IDs of target (R)AN 204t via target UPF 212t.

SMF 220 may then send an N11 ACK message (7328) (including information about the CN tunnel) to AMF 218. Steps (7332) and (7334) may be similar to steps 7 and 10 defined in clause 4.9.1.1 of TS 23.502. After the timer expires after step (7320), the SMF 220 may initiate a release procedure for the source UPF 212s by sending an N4 session end request message (7336) to the source UPF 212. The message (7336) may include a release reason (or reason code). The originating UPF 212 may be acknowledged with an N4 session end response message (7338) in SMF 220 to acknowledge the release of resources.

The service request procedure may be used by the 5G UE 202 in the CM IDLE state to request the establishment of a secure connection with the AMF 218. The UE 202 in the CM IDLE state may initiate the service request procedure to send uplink signaling messages, user data, or a paging request response. online. Upon receiving the service request message, the AMF 218 may perform authentication and the AMF 218 may perform a security procedure. After establishing a secure signaling connection with the AMF 218, the UE 202 or the network may send signaling messages, such as establishing a PDU session from the UE 202 to the network, or the SMF 220 through the AMF 218 may begin establishing user plane resources for the PDU sessions requested by the network and/or specified in the service request message.

For any service request, the AMF 218 may respond with a service response message to synchronize the PDU session state between the UE 202 and the network. AMF 218 may also respond with a service failure message at UE 202 if the service request cannot be accepted by the network. To request a service due to user data, the network may take further action if the user plane resource establishment was not successful. If the current N3 termination UPF 212 cannot be connected to (R)AN 204, the SMF 220 may reselect a new termination UPF 213 with N3. It should be noted that the procedure in clause 4.2.3.2 is not applicable for an access network (once the UE 202 is registered with the network), in which the UE 202 is always considered to be in the CM-CONNECTED state, and in which the user plane resource is always considered to be established for an active session. PDU.

In FIG. 74 illustrate in a message processing flowchart an example of a service request procedure (7400) initiated by a UE, in accordance with embodiments of the present invention. UE 202 initiates a service request procedure to activate a PDU session. The 5G core network can reselect the new N3 UPF termination connection. The source UPF 204 and the target UPF 204t are not the UPF 212 that provides the N6 connection to the data network (DN). UE 202 may send a NAS MM service request message (7402) to the (R)AN 204. Message (7402) may include PDU session ID(s), security parameters, and PDU session state. UE 202 may send a MM service request message (7402) to the NAS encapsulated in the RRC message to the (R)AN 204. If the service request is initiated for user data, the UE 202 may include the PDU session identifier in the NAS service request message. to indicate the PDU session(s) that the UE 202 should use. If the service request is initiated for signaling only, the UE 202 does not include any PDU session ID. When this procedure is initiated for a paging response, if the UE 202 needs to use some PDU session(s), the UE 202 may include the PDU session ID(s) in the NAS MM service request message to indicate the PDU session(s) that the UE 202 should use. Otherwise, UE 202 will not include any PDU session ID. The PDU session state indicates the PDU sessions available at UE 202.

The (R)AN 204 may then send a message (7404) to the AMF218 N2 that includes the NAS MM service request, 5G temporary identifier, location information, RAT type, and RRC establishment reason. If the AMF 218 cannot process the service request, it may reject it. A temporary 5G identifier can be obtained in the RRC procedure. The (R)AN 204 may select the AMF 218 according to the temporary identifier. The location information and RAT type are relative to the cell in which the UE 202 is located. Based on the PDU session state, the AMF 218 may initiate a PDU session release procedure if the PDU session is not available at the UE 202. Then, if the service request was not sent with integrity protection or integrity protection is indicated as failed, the AMF 218 may initiate the NAS authentication/security procedure (7406) as defined in clause 4.6 of TS 23.502. If the UE 202 initiated a service request to establish only a signaling connection, after exchanging security information, the UE 202 and the network may send signaling, and steps (7408) and (7420) - (7430) are skipped.

AMF 218 may then send a message (7408) to SMF 220 N11, which may include PDU session ID(s), location information, and RAT type. If the NAS MM service request message includes the PDU session ID(s) or if this procedure is initiated by the SMF 220, the PDU session IDs from the UE 202 correlate with other SMFs 220 than those initiating the procedure, the AMF 218 may send an N11 message in SMF(s) 220 associated with PDU session ID(s). If the current source UPFs 212 cannot serve the requested PDU session, the SMF 220 may select the target UPF 212t (7410) based on the criteria in clause 6.3.3 of TS 23.501. Otherwise, if the source UPFs 212 can serve the requested PDU session, steps (7412) - (7418), (7438) - (7440) and (7444) - (7446) are skipped.

Once the target UPF 212t is determined, the SMF 220 may assign N3 tunnel information (such as N3 tunnel endpoint identifier) and N9 tunnel information (such as N9 anchor UPF address and N9 tunnel endpoint identifier). SMF 220 may then send N4 a session establishment request PDU message (7412) to target UPF 212t. Message (7412) may include a UE context and a session PDU including a PDU session ID, a QoS policy, a charging policy, and N3 and N9 tunnel information. The target UPF 212t can then provision resources to support the PDU session. The target UPF 212t may send a session establishment response message (7414) to the SMF 220. The message (7414) may include a UE identifier (such as SUPI) and a PDU session identifier. Alternatively, the message (7414) may include a transaction ID that is both a UE ID and a PDU session ID.

The SMF 220 may then send N4 a session change request message (7416) to the anchor UPF 212a (ie, the UPF of the session anchor that connects N6 to the DN). Message (7416) may include a UE identifier such as SUPI and N9 target UPF 212t 212t tunnel information such as a target UPF address and an N9 downlink tunnel endpoint identifier. The anchor UPF 212a may then update the tunnel information of the target UPF. The anchor UPF 212a may send a session change response message (7418) to the SMF 220. The SMF 220 may send an N11 message (7420) to the AMF 218. The message (7420) may include N2 SM information such as PDU session ID, QoS profile, CN N3 tunnel information and S-NSSAI.

After receiving the N11 message (7408), each SMF 220 may send an N11 message (7420) to the AMF 218 to establish a user plane for PDU sessions. The N2 SM information may include information that the AMF 218 may provide to the (R)AN 204. If the target UPF212t (7410) is selected, the SMF 220 may start a timer to be used in steps (7444) and (7446). The AMF 218 may send an N2 request message (7422) to the (R)AN 204. The message (7422) may include the N2 SM information received from the SMF 220, a security context, an AMF signaling connection identifier, a handover constraint list, and a MM NAS service confirmation. . The (R)AN 204 may store the security context, AMF signaling connection identifier, QoS information for the QoS flows of activated PDU sessions, and N3 tunnel identifiers in the context of the UE RAN. The NAS MM service confirmation may include the session state of the PDU in the AMF 218. The AMF 218 may include at least one N2 SM information from the SMF 220 if the procedure is triggered to set up a session PDU user plane. AMF 218 may send additional SM N2 information from SMF 220 in separate N2 messages (eg, N2 tunnel setup request), if any. Alternatively, if multiple SMFs 220 are involved, AMF 218 may send a single N2 request message to (R)AN 204 after receiving N11 messages from SMF 220. In such cases, the N2 request message may include N2 SM information received in each of N11 messages, and information allowing the AMF 218 to associate responses with the corresponding SMF 220.

The (R)AN 204 may reconfigure (7424) the RRC connection with the UE 202 depending on the QoS information for the QoS flows of the activated PDUs and radio bearers. At this point (7424), user plane security can be established. The (R)AN 204 may forward the NAS MM service acknowledgment to the UE 202. The UE 202 may locally delete the session context of PDUs that are not available on the 5G CN. Once the radio resources in the user plane have been established, the uplink data from UE 202 can now be directed to (R)AN 204 (7426). The 5G (AN)AN 204 may send uplink data to the UPF address 212 and the tunnel ID provided in step (7422). The (R)AN 204 may send an N2 request ACK message (7428) to the AMF 218. The message (7428) may include N2 SM information that includes (R)AN tunnel information, a list of received QoS flows for activated session PDUs, and a list of rejected QoS flows for activated session PDUs. The N2 SM information may include tunnel information of the (R)AN 204. The (R)AN 204 may respond to the N2 SM information with a separate N2 message (e.g., an N2 tunnel setup response) if the AMF 218 sends a separate N2 message at step (7422) . If the N2 SM information is included in the N2 request message at 7422, the N2 request ACK (7428) may include information about the N2 SM set and information allowing the AMF 218 to associate responses with the corresponding SMF 220.

AMF 218 may then send an N11 message (7430) for each received session PDU to SMF 220. Message (7430) may include N2 SM information (which includes (R)AN tunnel information and a list of received QoS flows) and RAT type . If the AMF 218 has received the N2 SM information (one or more) in step (7420), then the AMF 218 may forward the N2 SM information to the corresponding SMF 220. If the UE's time zone has changed from the UE's last reported time zone, then the AMF 218 may add UE time zone IE in this message (7430). If a dynamic PCC is deployed, SMF 220 may optionally initiate a PDU-CAN session change (7432) and provide new location information to PCF 222.

If the source UPF 212s are selected in step (7410) and if the user plane is to be set or changed, the SMF 220 may initiate an N4 session change request procedure by sending an N4 change request message (7434) to the source UPF 212s. Message (7434) may include AN (R) tunnel information. Source UPF 212s may send an N4 session change response message (7436) to the SMF 220. If the target UPF 212t is selected in step (7410) and if the user plane is to be set or changed, the SMF 220 may initiate the N4 session change procedure by sending a request change session PDU message N4 to target UPF 212t (7438). The message may include (R)AN tunnel information. Target UPF 212t may send N4 session change response message (7440) to SMF 220.

The SMF may send an N11 ACK message (7442) to AMF 218. The message (7442) may include a PDU session identifier. The SMF 220 may indicate to the AMF 218 a successful session activation message (7442). AMF 218 may keep the PDU session active state. When the timer set in step (7420) expires, the SMF 220 may send an N4 session end request message (7444) to the source UPF 212. The message (7440) may include a UE 202 identifier (eg, SUPI) and a PDU session identifier. The original UPF 212 may remove the PDU session context. The source UPF 212 may then send N4 a session termination response message (7446) to the SMF 220.

In FIG. 74, UPF termination N3 is not UPF 212 providing N6 connection to data network (DN) 208. In case UPF termination NF is also UPF 212 which provides N6 connection to DN 208, 5G core network (SMF) 220) can insert a UPF to terminate the N3 connection and connect the new UPF to the UPF providing the N6 connection.

The service request procedure may be used by the 5G UE 202 in the CM-CONNECTED state to request the establishment of user plane resources for PDU sessions. It should be noted that the network may take further action if the user plane resource establishment was not successful. It is also noted that the procedure shown in FIG. 75 is used for an access network (when the UE 202 is registered with the network), in which the UE 202 is always considered to be in the CM-CONNECTED state, and in which the user plane resource is always considered to be set to the active PDU session.

FIG. 75 illustrates in a message processing flowchart an example of a service request procedure initiated by a UE in a CM-CONNECTED state (7500) in accordance with embodiments of the present invention. UE 202 may send an MM service request message (7402) to the (R)AN 204 to the NAS. The message (7402) may include PDU session ID(s). The UE 202 may send the NAS MM service request message to the RRC encapsulated AMF 218 to the (R)AN 204. The NAS MM service request message may be encrypted and integrity protected. The PDU session ID(s) in the NAS Service Request message may indicate the PDU session that UE 202 selects to activate.

The (R)AN 204 may then send an N2 message (7404) to the AMF 218. The message (7404) may include a NAS MM service request. If the service request (7404) cannot be processed by AMF 218, AMF 218 may reject it. The (R)AN 204 may forward the NAS MM Service Request message to the AMF 218 based on the existing N2 connection. AMF 218 may send an N11 message (7408) to SMF 220. The message may include PDU session identifier(s), location information (for a UE, may be in (R)AN address format), and RAT type. If the current source UPFs 212 are unable to service the requested PDU session, the SMF 212 may select the target UPF 212t (7410) based on the criteria in 6.3.3 of TS 23.501. Otherwise, if the source UPFs 212 can serve the requested PDU session, steps (7412) - (7418) and (7438), (7440), (7444) and (7446) are skipped.

Once the target UPF 212t is determined, the SMF 220 may assign N3 tunnel information (such as N3 tunnel endpoint ID) and N9 tunnel information (such as N9 anchor UPF address and N9 tunnel endpoint ID). SMF 220 may then send N4 a session establishment request PDU message (7412) to target UPF 212t. Message (7412) may include a UE session context and a PDU, including a PDU session ID, QoS policy, charging policy, and N3 and N9 tunnel information. The target UPF 212t can then provision resources to support the PDU session. The target UPF 212t may send a session establishment response message (7414) to the SMF 220. The message (7414) may include a UE identifier (eg, SUPI) and a session PDU identifier.

The SMF 220 may then send N4 a session modification request message (7416) to the anchor UPF 212a (ie, the session anchor UPF). Message (7416) may include SUPI information and N9 target UPF 212t tunnel information, such as target UPF address and N9 downlink tunnel endpoint identifier. The target UPF 212a may then update the tunnel information of the target UPF. The target UPF 212a may send a session change response message (7418) to the SMF 220. The SMF 220 may send an N11 message (7420) to the AMF 218. The message (7420) may include N2 SM information such as PDU session ID, QoS profile, CN N3 tunnel information and S-NSSAI.

Upon receipt of the N11 message (7408), each SMF 220 may send an N11 message (7420) to the AMF 218 to establish a user plane for PDU sessions. The N2 SM information may include information that the AMF 218 may provide to the (R)AN 204. If the target UPF212t (7410) is selected, the SMF 220 may start a timer to be used in steps (7444) and (7446). The AMF 218 may send an N2 request message (7422) to the (R)AN 204. The message (7422) may include N2 SM information received from SMF 220 including PDU session ID, QoS profile, N3 CN tunnel information, S -NSSAI and NAS confirmation of MM service. If there are multiple PDU sessions that include multiple SMFs 220, AMF 218 need not wait for responses from all SMFs 220 in step (7420).

The RAN reconfigures (7424) the RRC connection with the UE 202 depending on the QoS information for the QoS flows of the PDU sessions and the activated data radio bearers. The (R)AN 204 may forward the MM service acknowledgment to the NAS to the UE 202. Once the user plane radio resources for the selected session PDU have been established, the uplink data from the UE 202 may now be forwarded (7426) to the (R)AN 204. 5G (R) The AN 204 may send uplink data to the UPF address and tunnel ID provided in step (7422). The (R)AN 204 may then send an N2 request ACK message (7428) to the AMF 218. The message (7428) may include N2 SM information such as (R)AN tunnel information, a list of received QoS flows for activated PDU sessions, and a list of rejected QoS flows for activated PDU sessions. Message (7428) may include SM information N2, for example, (R)AN tunnel information. The (R)AN may send the N2 SM information with separate N2 messages (eg, N2 tunnel setup response) in step (7422). AMF 218 may then send an N11 message (7430) for each received PDU session to SMF 220. Message (7430) may include N2 SM information (including (R)AN tunnel information, a list of received QoS flows, and a list of rejected QoS flows ). If a dynamic PCC is deployed, SMF 220 may optionally initiate a PDU-CAN session change (7432) and provide new location information to PCF 222.

SMF 220 may send N4 session change request message (7434) to source UPF 212. Message (7434) may include (R)AN tunnel information and a list of received QoS flows. If the source UPFs 212s are selected in step (7412), and if the user plane is to be set or changed, the SMF 220 may initiate the N4 session change procedure by sending N4 a session change request message (7434), providing the (R)AN with tunnel information (e.g., (R)AN address and (R)AN N3 tunnel endpoint ID). Source UPFs 212 may send N4 a session change response message (7436) to SMF 220. If the target UPF 212t is selected in step (7410) and if the user plane is to be set or changed, SMF 220 may initiate session change procedure N4 by sending a request (7438) Change the session to the target UPF 212t that provides the (R)AN with tunnel information (eg, (R)AN address and (R)AN N3 tunnel endpoint ID). The target UPF 212t may send an N4 session change response message (7440) to the SMF 220. The SMF 220 may send an N11 ACK message (7442) to the AMF 218. The message (7442) includes a PDU session identifier. SMF 220 may indicate successful session activation for AMF 218. AMF 218 may then store the PDU's session activated state. If the target UPF 212t is selected in step (7410), after the timer set in step (7422) expires, the SMF 220 may send N4 a session end request message (7444) to the source UPF 212s. Message (7444) may include a UE 202 identifier (eg, SUPI) and a PDU session identifier. Source UPF 212 may remove the PDU session context and send N4 a session end response message (7646) to SMF 220.

A network-initiated service request procedure may be used when the network needs to signal (eg, N1 signaling to UE 202, SMS with mobile termination, setting up user plane session PDU resource to deliver user termination data on mobile) to UE 202. If UE 202 is in the CM-IDLE state or the CM-CONNECTED state, the network may initiate a network-initiated service request procedure. If UE 202 is in the CM-IDLE state and asynchronous type communication is not activated, the network may send a paging request to the (R)AN/UE. The paging request may initiate a service request procedure at the UE 202. If an asynchronous type of communication is enabled, the network may store the received message and forward the message to the (R)AN 204 and/or UE 202 (i.e., synchronize the context with the (R)AN 204 and/or UE 202) when UE 202 enters the CM-CONNECTED state.

FIG. 76 illustrates in a message processing flowchart an example of a service request procedure (7600) initiated by a network in accordance with embodiments of the present invention. When UPF 212 receives downlink session PDU data (7602) and there is no (R)AN 204 tunnel information stored in UPF 212 for session PDU, UPF 212 may buffer downlink data. Upon arrival of the first downlink data packet (7602), the UPF 212 may send a data notification message (7604) to the SMF 220. The message (7604) may include a PDU session identifier and a priority. If UPF 212 receives additional downlink data packets (7604) for a QoS flow in the same PDU session with the same or lower priority than used in any previous data notification for that PDU session, UPF 212 may buffer those downlink data packets. communication without sending new notification data. It should be noted that if UPF 212 receives additional downlink data packets for a QoS flow in the same PDU session with a higher priority than that used in any previous data notification for that PDU session, UPF 212 may send a data notification message (7604) in SMF 220 indicating higher priority. If the paging policy demarcation feature (as defined in TS 23.501 5.2.X) is supported by UPF 212, and if enabled by SMF 220 for this N4 session, UPF 212 may also add DSCP to the TOS (IPv4)/TC (IPv6) value from IP header of the downlink data packet. If the SMF 220, while waiting for the user plane to be established in the UPF 212, receives an N11 message notifying the new AMF 218 serving UE 202 from the new AMF 218, the SMF 220 may resend the data notification message (7604) to the new AMF 218. The SMF 220 may send ACK (7606) data notification in UPF 212.

Upon receipt of the data notification message (7604), the SMF 220 may determine the AMF 218 and send an N11 message (7608) to the AMF 218 including the priority and session PDU IDs received in the data notification message (7604). Message (7608) may include a persistent UE ID, PDU session ID, N2 SM information (including PDU session ID, QoS profile, N3 CN tunnel information, and S-NSSAI), priority, and paging policy. If the SMF 220, while waiting for a user plane connection to be activated, receives any additional data notification message (7604) for the same PDU session, but with a higher priority than that specified in any previous data notification for that PDU session, the SMF 220 may send a new N11 a message (7608) indicating the higher priority and session ID of the PDU in the AMF 218. If the SMF 220, while waiting for user plane activation, receives a message response N11 (7606) from an AMF 218 other than the one to which the SMF 220 sent the N11 message, The SMF 220 may send an N11 message to this AMF 218. Supporting paging policy differentiation, the SMF 220 may indicate in the N11 message (7608) a paging policy indication associated with the downlink data (7602) that initiated the data notification message (7604). It should be noted that AMF 218 may receive request message(s) from other network functions, which may result in signaling towards the UE/RAN, such as a network initiated disconnect and SMF 220 initiating a PDU session change. If UE 202 is in the CM-CONNECTED state and AMF 218 only delivers N1 message to UE 202, the flow continues to step (7618) below. If the UE 202 is in the CM-IDLE state and the AMF 218 determines that the UE 202 is not paging available, the AMF 218 may send an N1 message (7610) to the SMF or other network functions from which the AMF 218 received the request message in step (7608 ) indicating that the UE 202 is unavailable, or the AMF 218 performs an asynchronous type communication and stores an N11 message (7610). If an asynchronous type communication is called and AMF 218 stores an N11 message, AMF 218 may initiate communication with UE 202 and (R)AN 204 when UE 202 is reachable, such as when UE 202 enters the CM-CONNECTED state. If the AMF change registration procedure 218 is performed when the preceding AMF 218 receives the N11 message (7608), the preceding AMF 218 may reject the N11 message indicating that the N11 message has been temporarily rejected. The SMF 220 may notify the UPF 212 of a user plane setup failure (7612). Upon learning that the N11 message requested from SMF 220 has been temporarily rejected and receiving the downlink data notification from UPF 212, SMF 220 may request UPF 212 to apply extended buffering.

AMF 218 may send a page message (7740) to the node (R) AN. If the UE 202 is in the CM-CONNECTED state, the AMF 218 performs the steps in the UE-initiated service request procedure (7618) to activate the user plane connection for this PDU session (ie, establish radio resources and N3 tunnel). The rest of this procedure can be omitted. If the UE 202 is in the RM-REGISTRETED state, in the CM-IDLE state, and reachable, the AMF 218 may send a page message (7740) to the (R)AN node(s) belonging to the registration area(s) in which the UE 202 is registered. The paging may include a NAS ID for the paging, a list of registration areas, a DRX length of the paging, and an indication of the paging priority. In support of paging policy differentiation, the AMF 218 may add a paging policy indication to the paging request message.

Paging policies may be configured in AMF 218 for various combinations of DNNs, paging policy indications, PDU session IDs from SMF 220 when available, and other PDU session context information identified by the PDU session ID received in the N11 message. The paging strategies may include: a paging retransmission scheme (eg, how often the paging is repeated or at what time interval); determining whether to send a paging message (7740) to (R)AN nodes during certain AMF 218 high load conditions; whether to apply paging on a sub-area basis (eg, first paging in last known cell ID or TA and retransmission in all registered TAs). AMF 218 and (R)AN204 may support additional paging optimization to reduce the load on signaling and network resources used to successfully page UE 202 by one or more of the following means:

• with AMF 218 implementing specific paging strategies (eg, N2 paging message (7740) is sent to (R)AN nodes that last served UE 202);

• AMF 218 based on the recommended RAN cells and nodes provided by the (R)AN 204 upon transition to the CM-IDLE state. AMF 218 takes into account the (R)AN nodes related in part to this information to determine the (R)AN nodes for paging and provides recommended cell information in an N2 paging message to each of these (R)AN nodes;

• by (R)AN 204, considering the number of paging attempts provided by AMF 218 when paging.

If the UE's ability to broadcast the paging information is available in the AMF 218, the AMF 218 may add the ability to broadcast the UE's paging information in the N2 paging message (7740) to the (R)AN nodes 204. If the recommended cell and (R)AN node information is available for paging in the AMF 218, the AMF 218 may take this information into account to determine the (R)AN nodes to page, and when paging the (R)AN node, the AMF 218 may transparently pass recommended cell information to the (R)AN node. AMF 218 may add information about the number of paging attempts to the N2 paging message. The information about the number of paging attempts may be the same for all (R) AN nodes selected by the AMF 218 for paging. If the (R)AN nodes receive paging messages from the AMF 218, then the UE 202 may page with the (R)AN node (7614).

AMF 218 may send N11 an ACK message (7616) to SMF 220. AMF 218 may control the paging procedure with a timer. If AMF 218 does not receive a response from UE 202 to the paging request message (7614), AMF 218 may apply additional paging according to any applicable paging strategy. If the AMF 218 does not receive a response from the UE 202, the AMF 218 considers the UE 202 unreachable and the SM message N2 cannot be forwarded to the (R)AN 204. ", for example, the UE's unavailability for SMF 220 or other network functions to indicate a "message routing service" failure if AMF 218 is unaware of the current MM procedure that prevents UE 202 from responding, i.e., AMF 218 receives an N14 context request message indicating that the UE 202 is performing the registration procedure with the other AMF 218. Upon receipt of "message reject N11", the SMF 220 may inform the UPF 212.

When the UE is in the CM-IDLE state, after receiving a paging request (7614), the UE may initiate a service request procedure (7618) initiated by the UE. The AMF 218 may send an N11 message to the SMF(s) 220 associated with the session PDU identified by the PDU session ID(s) in the NAS MM Service Request message, if present, but not to the SMFs 220 from which the N11 message is received in step ( 7608). The UPF 212 transmits any buffered downlink data to the UE 202 via the (R)AN node that performed the service request procedure (7618). The network may send downlink signaling (7620) if the procedure is triggered due to a request from other network entities described in step (7608).

A UE-initiated service request in the CM-IDLE state procedure may be used by the 5G UE 202 in the CM-IDLE state to request the establishment of a secure connection with the AMF 218. The UE 202 in the CM-IDLE state may initiate a service request procedure to send uplink signaling messages, user data or a response to a network paging request. Upon receipt of the service request message, the AMF 218 may perform an authentication and security procedure. After establishing a secure signaling connection with the AMF 218, the UE 202 or the network may send signaling messages, such as establishing a PDU session from the UE 202 to the network, or the SMF 220 through the AMF 218 may begin establishing a user plane resource for the PDU sessions requested by the network and/or specified in the service request message. For any service request, the AMF 218 may respond with a service response message to synchronize the PDU session state between the UE 202 and the network. AMF 218 may also respond with a service failure message at UE 202 if the service request cannot be accepted by the network. To request a service due to user data, they may take additional actions if the user plane resource establishment was not successful. It should be noted that the procedure shown in FIG. 64 is not applicable to an access network (when the UE 202 is registered with the network), in which the UE 202 is always considered to be in the CM-CONNECTED state, and in which the user plane resource is always considered to be established for the active session PDU.

FIG. 77 illustrates in a message processing flowchart an example of a service request procedure (7700) initiated by a UE in a CM-CONNECTED state, in accordance with embodiments of the present invention. UE 202 may send an MM service request message (6402) to the (R)AN 204 to the NAS. The message (6402) may include PDU session ID(s). UE 202 may send a message NAS service request to an AMF 218 encapsulated in an RRC message to the (R)AN. The NAS MM service request message may be encrypted and integrity protected. The PDU session ID(s) in the NAS Service Request message of the message indicates the PDU session that the UE 202 selects to activate.

The (R)AN 204 may send an N2 message (6404) to the AMF 218. The message (6404) may include the NAS MM service request. If the service request (6404) cannot be processed by the AMF 218, the AMF 218 may reject it. The (R)AN 204 may forward the NAS an MM service request message to the AMF 218 based on the existing N2 connection. AMF 218 may then send N11 a message (6408) to SMF(s) 220 associated with the PDU session ID(s). Upon receiving the N11 message (6408), each SMF 220 may send an N11 message (6410) to the AMF 218 to set up the user plane(s) for the PDU sessions. Message (6410) may include SM N2 information, which includes PDU session ID, QoS profile, N3 CN tunnel information, and S-NSSAI. The N2 SM information may include information that the AMF 218 may provide to the (R)AN 204.

AMF 218 may then send N2 request message (6412) to (R)AN 204. Message (6412) may include N2 SM information (including QoS profile and N3 CN tunnel information received from SMF, NAS MM confirmation of service) . If there are multiple PDU sessions that include multiple SMFs 220, AMF 218 need not wait for responses from all SMFs 220 at step (6410). The (R)AN 204 may then perform RRC connection reconfiguration (6414) with the UE 202 depending on the QoS information for the QoS flows of the activated PDU sessions and radio bearers. The (R)AN 204 may forward the NAS MM an acknowledgment of the service to the UE 202. If the (R)AN 204 receives at least one of the QoS flows, the UE 202 may keep the PDU session state activated. Otherwise, UE 202 may treat the service request as not received by (R)AN 204; The session state of the PDU at the UE remains deactivated.

After setting the radio resources in the user plane for the selected session PDU, the uplink data from the UE 202 can now be forwarded (6416) to the (R)AN 204. The 5G (R)AN 204 can send the uplink data to the UPF address 212 and the tunnel ID provided in step (6410). If the (R)AN 204 receives at least one QoS flow, the (R)AN 204 may send an N2 request ACK message (6418) to the AMF 218. The message (6418) may include a PDU session ID, N2 SM information ( including tunnel (R)AN information, a list of accepted QoS flows for activated PDU sessions, and a list of rejected QoS flows for activated PDU sessions). The (R)AN 204 may respond with N2 SM information with separate N2 messages (eg, an N2 tunnel setup response). If the (R)AN 204 does not receive the session PDU, the (R)AN 204 may send N2 a request ACK message (6418) to AMF 218 indicating that the N2 request was not received and a reason code. Message (6418) may include SM N2 information (including PDU session ID, PDU session rejection, and reason code). AMF 218 may send an N11 message (6420) for each received session PDU to SMF 220. Message (6420) may include a PDU session ID and N2 SM information received from (R)AN 204 at step (6418).

If a session PDU is received and if a dynamic PCC is deployed, the SMF 220 may initiate an IP-CAN session change procedure (6422) and provide new location information to the PCF 222. If the session PDU is received and if the user plane needs to be set or changed, the SMF initiates an N4 session change procedure by sending an N4 session update request message (6424) that provides RAN tunnel information and a list of received QoS flows. The UPF 212 may then send an N4 session update response message (6426) to the SMF 220. The SMF may then send an N11 ACK message (6428) to AMF 218. The message may include a PDU session ID and a PDU session state. SMF 220 may indicate the PDU session state (activated or deactivated) for AMF 218.

An inter-NG RAN handover procedure based on Xn without moving the user plane function can be used to transfer the UE 202 from the source (R)AN 204s to the target (R)AN 204t using Xn when the AMF 218 does not change and the SMF 220 determines to keep the existing UPF 212. The UPF 212 referred to is the UPF 212 which terminates the N3 interface in the 5GC. An IP connection is assumed between the source UPF 212s and the target UPF 212t. If the target (R)AN 204 does not have sufficient resources to service some of the PDU sessions, the target (R)AN 204 may notify the SMF 220. The SMF 220 may then decide to release or retain the PDU session. To release a session PDU, SMF 220 may initiate a session PDU release procedure. To save the PDU session, SMF 220 may do one of the following: 1. Deactivate the N3 tunnel between target (R)AN 204t and UPF 212; 2. Set "Session-AMBR" (aggregate maximum bit rate) to zero; or 3. Deactivate the user plane including the DRB air interface and the N3 tunnel.

FIG. 78 illustrates in a message processing flowchart an example of an Intra AMF procedure (7800), between an NG-RAN node without an Xn interface, in accordance with embodiments of the present invention. Downlink UP data may be transmitted (7802) between UPF 212 and UE 202 via S-RAN 204. An event may occur that causes S-RAN 204 to initiate a move across N2 (7804). The S-RAN 204 may send a Handover Required message (7806) to the AMF 218. The message (7806) may include a target identifier, a source-target transparent container, and PDU session identifiers. The transparent source-target container may include (R)AN information generated by S-RAN 204 to be used by T-RAN 204t and transparent to 5GCN. All PDU sessions handled by the S-RAN 204 (i.e., all existing PDU sessions with active UP connections) may be added to a Handover Required message (7806) indicating which of these PDU sessions the S-RAN 204 is requesting for handover.

AMF 218 may send a PDU handover request message (7808) to SMF 220. The message may include a PDU session ID and target ID, and may be sent for each specified PDU session by S-RAN 204s as handover candidate N2. The PDU session ID indicates the PDU session candidate for N2 handover.

The SMF 220 may send a PDU handover response message (7810) to the AMF 218. The message (7810) may include a PDU session ID and N2 SM information. SMF 220 may select a UPF 212 that supports N3 connection to target (R)AN node 204t. The SMF 220 may check if an N2 handover can be received for the specified PDU session and may include the result in the N2 SM information transparently sent to the AMF 220 in the T-RAN 204t. If the N2 handover for the PDU session is received, the N2 SM information may also include the PDU session ID, the N3 UP address and the UPF 212 tunnel ID, and the QoS parameters.

The AMF 218 monitors the PDU handover response message (7812) from the involved SMFs 220. The smallest value of maximum delay indications for PDU sessions that are handover candidates gives the maximum time that the AMF 218 can wait for the PDU handover response message (7810) before continuing the procedure. N2 handover. When the maximum timeout has elapsed or when all PDU handover response messages have been received, the AMF 218 continues the handover procedure N2 (handover request message at step (7820)).

AMF 218 may send a PDU handoff cancel message (7814) to SMF 220. The message (7814) may include a PDU session identifier. A PDU handover response message (7810) arriving too late is indicated by the SMF 220, allowing the SMF 220 to release the possibly allocated N3 UP address and tunnel ID for the selected UPF 212. It should be noted that the PDU change request message (7816) sent by the AMF 218 to the SMF 220 , and a PDU change response message (7818) sent by SFM 220 to AMF 218 starts at step (7812) and is executed in parallel with this and later steps.

AMF 218 may send a handover request message (7820) to T-RAN 204t. The message (7820) may include a transparent source-target container, information MM N2 and information list SM N2). AMF 218 may determine and/or select T-RAN 204t based on the target ID. AMF 218 may allocate a GUTI valid for UE 202 in AMF 218 and target TAI. The transparent source-target container may be forwarded as received from S-RAN 204. The N2 MM information may include, for example, security information and a handover restriction list. The SM N2 information list may include SM N2 information from SMF 220 in PDU handover response messages received before the end of step (7814).

The T-RAN 204t may send a handover request confirmation message (7822) to the AMF 218. The message (7822) may include a transparent source-target container, a list of SM N2 responses, and a list of invalid session PDUs. The transparent source-target container may include a UE 202 container with an access layer part and a NAS part. The UE 202 container may be transparently sent via AMF 218 and S-RAN 204 to UE 202. The information provided in S-RAN 204 may also include a list of PDU session identifiers indicating the PDU sessions that failed to establish and the reason for the failure ( for example, SMF decision 220, SMF 220 response too late, or T-RAN decision 204t). The N2 SM response list includes, for each N2 SM information received and N2 session PDU received SMF 220, a PDU session ID and an N2 SM response indicating the PDU session ID and if the T-RAN 204t received a handover request N2 for the session PDU. For each received T-RAN 204t session PDU for N2 handover, the N2 SM response may include the N3 UP address and T-RAN 204t tunnel ID, as well as a list of received QoS flows. For PDU sessions that T-RAN 204t rejects, T-RAN 204t may set Session-AMBR to zero. Alternatively, T-RAN 204t may delete the N3 tunnel information of the UPF 212.

The AMF may send a PDU change request message (7824) to the SMF 220. The message (7824) may include a PDU session identifier and an SM N2 response. For each T-RAN 204t received SM N2 response (contained in the SM N2 response list), AMF 218 may send the received SM N2 response to the SMF 220 indicated in the corresponding PDU session ID.

The SMF 220 may send a PDU change response message (7826) to the AMF 218. The message (7826) may include a PDU session identifier, and a message (7826) may be sent for each PDU change request message (7824) received. The SMF 220 may prepare for the N2 handover by specifying the N3 UP address and the T-RAN tunnel ID 204t to the UPF 212 if the N2 handover is received by the T-RAN 204t. If the N2 handover is not received by T-RAN 204t, SMF 212 may set the Session-AMBR of the rejected session PDUs to zero. The SMF 220 may acknowledge the Change Request message by sending a PDU Change Response message to the AMF 218.

The AMF may send a handover command message (7828) to the S-RAN 204. The message (7828) may include a source-target transparent container, a list of invalid session PDUs. The source-target transparent container may be redirected as received from the AMF 218. S-RANs 204 may use the list of PDU sessions that failed to set up and the specified failure reason to determine whether to proceed with the procedure. N2 handover.

S-RAN 204 may send a handover command message (7830) to UE 202. The message may include a UE 202 container. UE 202 container may be sent transparently from T-RAN 204t via AMF 218 to S-RAN 204 and provided to UE 202 via S-RAN 204.

After UE 202 has successfully synchronized (7832) with the target cell, it may send a handover confirmation message (7834) to T-RAN 204t. With this message, UE 202 considers the handover successful. For rejected PDU sessions, UE 202 does not send an uplink request for the reactivation timer. This timer may be set by a setting in a policy of the UE 202 or by a message from the SMF 220.

The T-RAN 204t may then send a handover notification message (7838) to the AMF 218. According to this message, the handover is considered successful in T-RAN 204t. AMF 218 may then send a handover complete message (7840) to SMF 220. The message may include a PDU session identifier. A handover complete message (7840) may be sent per session PDU to the corresponding SMF 220 to indicate the success of handover N2.

The SMF 220 may send a handover complete ACK message (7842) to the AMF 218. The message (7842) may include a PDU session ID. SMF 220 may indicate to the selected UPF 212 that the downlink user plane for the specified PDU session may switch to T-RAN 204t. For PDU sessions that are not supported by T-RAN 204t, SMF 220 may notify the selected UPF 212 to set the Session-AMBR to zero, the reactivation timer, and the buffer command. Until the reactivation timer expires, if the UPF does not send a downlink packet notification to the SMF 220 if the UPF 212 receives the downlink packet; these packets may be buffered or dropped based on the buffer command. If the buffering command is set to TRUE, downlink packets are buffered. If the buffer command is set to FALSE, downlink packets are dropped. Thus, the SMF 220 may acknowledge receipt of the handover complete message. AMF 218 may send a UE context release command message (7846) to S-RAN 204s. The S-RANs 204 may then send a UE context release complete message (7848) to the AMF 218. The source (R)AN may release its resources related to UE 202 and respond with a UE context release complete message (7846).

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as generally understood by those skilled in the art to which this invention pertains.

Through the descriptions of the foregoing embodiments, the present invention may be implemented using hardware alone, or using software and the necessary universal hardware platform. Based on this understanding, the technical solution of the present invention can be implemented in the form of a software product. The Software Product may be stored on a non-volatile or persistent storage medium, which may be a read-only compact disk (CD-ROM), a USB flash drive, or a removable hard drive. The software product includes a set of instructions that enable a computing device (personal computer, server, or network device) to perform the methods provided in the embodiments of the present invention. For example, such an execution may correspond to the modeling of logical operations, as described here. The software product may additionally or alternatively include a set of instructions that enable the computing device to perform operations to configure or program the digital logic device in accordance with embodiments of the present invention.

AMF 218 is responsible for UE 202 access and mobility management, while SMF 220 is responsible for PDU session management. The AMF may not need to store the state of PDU sessions (activated and deactivated). In some of the procedures presented earlier in FIG. 59 and FIG. 60 for the N2 release procedure (or UE context release in the (R)AN procedure) and the handover procedures of FIG. 72 and FIG. 74, the AMF may store the session state of the PDU. In the following embodiments, the AMF may not store PDU session state, which helps separate the AMF and SMF functions.

An alternative solution for the N2 release procedure in FIG. 59, which is also referred to as the "UE context release to AN" procedure, is illustrated in FIG. 79, where the AMF may not store PDU session state. The UE context release in the AN procedure may be used to release the N2 connection and at the same time deactivate the PDU sessions when the UE 202 enters the CM-IDLE state. Fig. 79 illustrates, in a message processing flowchart, an example of an N2 release and session PDU procedure (5900) in accordance with embodiments of the present invention. The procedure (7900) may begin with the (R)AN 204 and UE 202 performing signaling path release on the (R)AN (7902). The RRC release procedure (7902) may be similar to the RRC release procedure (600A) described above. The (R)AN 204 interacts with the UE 202 to release the signaling RRC connection. UE 202 enters the CM-IDLE state and deactivates all PDU sessions. The (R)AN 204 may send (message N2) N2 UE context release (7904) to AMF 218. The message (5904) may include a reason code such as O&M intervention, UE inactivity, and so on. those skilled in the art will recognize that, in certain scenarios, step (7902) may be initiated before or in parallel with step (7904). The AMF 218 may send (message N11) a mobility event notification message (7906) to the UE SMF(s) 220 that have subscribed to the AMF UE's mobility event notification service for the "UE enters CM-IDLE state" event. Other names for the "UE enters CM-IDLE state" event may be "N2 release" or "UE CM state transition to CM-IDLE", etc. Message (7906) may include a UE identifier (such as SUPI), (R)AN information in case the UE has multiple (R)AN multiple connections, a reason code, a UE mobility event, a list of PDU session identifiers. It should be noted that the SMF 220 may subscribe to the UE's AMF 218 mobility event notification service when a session PDU is established or activated, or through a separate subscription procedure. For example, in TS 23.502, version 0.3.0 published in March 2014, SMF 220 may subscribe to the UE's AMF 218 mobility event notification service in step 4b in FIG. 4.2.3.2-1 of clause 4.2.3.2 "Service request initiated by UE in CM-IDLE state" or in step 3b of FIG. 4.2.3.3-1 of clause 4.2.3.3 "Service request initiated by UE in CM-CONNECTED state" , or at step 16 in figure 4.3.2.2.1-1 of clause 4.3.2.2.1 "no roaming and roaming with local interruption".

The SMF 220 then sends (message N4) a release request (7908) N3 to the UPF(s) 212. Other names for the release request (7908) message may be a session change request or a session deactivation PDU request. The message (7908) may include an identifier for identifying the UE, such as SUPI, or an identifier for identifying the session ID of the PDU to be deactivated, a buffering command, and a reactivation timer. The buffer command indicates whether the UPF will buffer the downlink PDU received for the UE, then initiates a downlink data notification to the SMF to initiate the "network initiated service request" procedure described in 4.2.3.3 of TS 23502, version 0.3.0, published March 2017. The reactivation timer indicates the minimum time that a PDU session is deactivated before the UPF can send a downlink data notification to the SMF if a downlink PDU packet arrives. UPF 212 then releases the N3 (R)AN tunnel information (eg, (R)AN IP address and tunnel ID) in the context of the UE PDU session for the PDU sessions to be deactivated. The UPF sends (message N4) an N3 release response (7910) to the SMF 220 acknowledging the release of the N3 (R) AN tunnel information. Other names for the message (7910) may be a session change response or a session deactivation response. The UPF 212 may begin buffering the downlink packets of the deactivated session PDUs. SMF 220 may not need to send a message (7912) to acknowledge receipt of the message (7906). Instead of a message (7912), the transport layer protocol may use an acknowledgment message when receiving a message (7906). SMF 220 may then change the session state of the PDU to "Session-IDLE".

The AMF 218 then sends (message N2) an N2 release response (7914) to the (R)AN 204 with a reason code via the N2 interface. Other message names (7914) may be N2 UE context release request. The AMF 218 may not need to store the session state of all UE 202 PDU sessions in "Session-IDLE" (or session deactivation state). Note that the message (7914) can be sent before, in parallel, or after the message (7906). If step (7902) has not been performed, RAN 204 and UE 202 perform an RRC release procedure (7916). The RRC release procedure (7916) may be similar to the RRC release procedure (600A) described above. Other names for the message (7916) may be "signaling path release on (R)AN" or "RRC reconfiguration". The (R)AN 204 sends a message to the UE 202 to release the RRC connection. UE 202 enters the CM-IDLE state and all PDU sessions at UE 202 transition to the "Session-IDLE" state (or in other words, the session deactivation state). Upon receiving the RRC connection release acknowledgment from the UE 202, the (R)AN 204 deletes the UE context. The (R)AN 204 then sends (message N2) an acknowledgment (7918) of the N2 release to the AMF 218. Another message name (7918) may be "N2 UE context release complete". After receiving the N2 release response message (7918), the AMF 218 sets the CM state of the UE to the CM-IDLE state and releases the N2 connection. It should be noted that the AMF 218 may retain or remove the subscription to the AMF 218 UE mobility event notification service for SMF PDU(s) sessions, for some UE mobility events such as "serving cell change".

It should be noted that the SMF 220 may subscribe to the UE's AMF 218 Mobility Event Notification Service for a Serving Cell Change event when a PDU session is established or activated, or through a separate subscription procedure. For example, in TS 23.502, version 0.3.0 published in March 2014, SMF 220 may subscribe to a mobility event notification service of UE AMF 218 in step 4b in FIG. 4.2.3.2-1 of clause 4.2.3.2 "service request initiated by UE in CM-IDLE state" or in step 3b of clause 4.2.3.3-1 of clause 4.2.3.3 "service request initiated by UE in CM-CONNECTED state" , or at step 16 in figure 4.3.2.2.1-1 of clause 4.3.2.2.1 "no roaming and roaming with local interruption". Therefore, during handover procedures, such as in FIG. 72, FIG. 73, and FIG. 78, AMF 218 may send path switching requests to SMF 220 that have subscribed to the AMF 218 UE Mobility Event Notification Service for the Serving Cell Change event. . The SMF 220 may subscribe to the UE AMF 218 mobility event notification service if the SMF serves activated or deactivated PDU sessions. For deactivated PDU sessions, during handover procedures, the SMF may move the UPF 212 or release the deactivated PDU session if there is no suitable UPF to service the PDU session.

Using the method that the AMF may not save the session state of the PDU and the SMF subscribes to an even UE mobility notification, another embodiment of Xn-based inter-NG(R)AN handover illustrated in FIG. 72 can be obtained.

In handover preparation (7202) and handover execution (7204), if the target (R)AN 204t rejects some PDU sessions, the target (R)AN 204t should not establish any Data Radio Bearer (DRB) for the rejected PDU session with the UE 202. UE MUST NOT release PDU sessions to which a DRB is assigned. The UE must wait for a decision from the SMF on whether to release or deactivate the rejected PDU sessions. These requirements may also apply to Xn-based inter-NG(R)AN handover with UPF movement described in FIG.

In message (7208), target (R)AN 204t sends an N2 path switch request to AMF 218. Message (7208) includes a list of accepted PDU sessions and a list of rejected PDU sessions.

AMF 218 may send N2 SM information via N11 message (7210) to each SMF 220 associated with the list of PDU sessions and the list of received QoS flows of each PDU session received in the N2 path switch request (7208). For PDU sessions to be switched to the target (R)AN 204t, upon receipt of the N11 message (7210), each of the SMFs 220 may determine whether the existing UPF 212 can continue to serve the UE 202. If the existing UPF 212 cannot continue to serve the UE 202 , and is not a PDU session binding, steps 3-11 of clause 4.9.1.2 of TS 23.502 (version 0.3.0 published March 2017) are followed. Otherwise, each of the SMFs 220 may perform the following steps (7212) - (7220) if their existing UPFs 212 can continue to serve the UE 202.

For the rejected session(s) PDU, AMF 218 may send a separate request(s) to the appropriate SMF file(s) 220 to notify that the target (R)AN 204t does not support that session PDU. AMF 218 may send separate request(s) to SMFs 220 that have subscribed to an even UE mobility notification triggered by the serving cell change. The message includes the address of the target (R)AN.

For PDU sessions requested (accepted) by target (R)AN 204t, SMF 220 may send an N4 session change request message (7212) to UPF 212. Message (7212) may include the (R)AN address and tunnel identifiers for the user plane downlink. For PDU sessions rejected by target (R)AN 204t, SMF 218 may either unblock or deactivate the PDU sessions. To release PDU sessions, SMF 218 may initiate a session PDU release procedure as defined in 4.3.4 of TS 23.502. In order for PDU sessions to be deactivated, SMF 218 may send an N4 session change request (7212) to UPF 212 for these PDU sessions. Message (7212) may indicate release of (R)AN N3 tunnel information such as (R)AN address and tunnel endpoint identifier for downlink user plane, buffering command and reactivation timer, and reason code (e.g., handover rejected or no data activity). It should be noted that the buffering command may be used to indicate whether UPF 212 should buffer incoming downlink packets. It is also noted that the reactivation timer may indicate the duration that a deactivated PDU session UP remains in a deactivated state after UPF 212 clears N3 (R)AN tunnel information. Before the reactivation timer expires, UPF 214 may buffer the downlink packets in accordance with the buffer command. After the reactivation timer expires, UPF 212 may buffer the downlink packets in accordance with the buffer command. If UPF 212 receives downlink packets before or after the reactivation timer expires, UPF 212 may send a downlink packet notification to SMF 220 to initiate a network initiated service request.

For deactivated PDU sessions, the SMF may decide to select a new UPF. If a new UPF is selected, the SMF sends the session context PDU to the new UPF and requests the previously used UPF to release the session context PDU. Alternatively, the SMF may install a new N3-terminated UPF and connect the new N3-terminated UPF to the previously used UPF.

The UPF 212 may return a session change response message (7214) to the SMF 220 after the requested session PDUs are switched or changed/deactivated. Message (7214) may include tunnel identifiers for uplink traffic. To assist the reordering function at the target (R)AN 204t for PDU sessions requiring a path switch, UPF 212 may send one or more "end marker" packets (7216) over the previously used path immediately after the path switch. The UPF 212 may start sending downlink packets to the target (R)AN 204t (7218). SMF 220 may send N11 an ACK message (7220) to AMF 218 for PDU sessions that have been successfully switched or deactivated. For switched PDU sessions, message (7220) may include an N2 SM message that includes N3 CN tunnel information. For deactivated session PDUs, message 7220 may comprise an N1 SM message container containing a session deactivation request and PDU session identifiers. The SMF may store the deactivation state of the deactivated session PDU(s).

Once an N11 ACK message (7220) is received from all SMFs 220, AMF 218 may aggregate the received N2 SM messages and N1 SM messages into an N2 path switch request ACK (7222) at the target (R)AN 204t. If none of the requested PDP sessions were successfully switched, the AMF 218 may send an N2 Path Switch Request Fail message to the target (R)AN 204t.

It should be noted that the AMF may collect an N11 ACK message (7220) from the SMF 220 that processes the path switch request for the received session PDUs and may send a separate message to the target (R)AN 204t. This will reduce the handover time for received PDU sessions. AMF 218 may N11 ACK message (7220) from SMF 220 for rejected session PDUs and carry N1 SM message containers as a single message to target (R)AN 204t.

If the target (R)AN 204t receives the N1 SM message container in step (7222), the target (R)AN 204t forwards the N1 SM message container (including the session deactivation request having the session ID PDU) to the UE 202 via an RRC message ( 7224). The UE maintains the deactivated state of the session PDU(s). UE 202 may release the radio context of deactivated PDU sessions. The UE sends an RRC message (7226) that includes the N1 SM session deactivation response(s) and PDU session identifier(s) of the deactivated session PDUs to the SMF 220 via the target (R)AN 204t and AMF 218. By sending a release message (7232) resources to the source (R)AN 204s, the target (R)AN 204t acknowledges the success of the handover. Resource release is then initiated from the source (R)AN 204.

In the above description, target RAN 204t sends an N1 session deactivate request message received from SMF 220 to UE 202 in a message (7224). Alternatively, the target (R) AN 204t may forward the N1 session deactivation request to the source (R) AN 204s. The source (R) AN 204 may then forward the N1 session deactivation request to the UE via another RRC message similar to the (7224) message. The UE acknowledges the PDU session deactivation by sending an N1 session deactivation response to the SMF. This message is delivered to either the source (R) AN 204s or the target (R) AN 204t by the same RRC message (7226). The source (R) AN 204s or target (R) AN 204t sends a N1 session deactivation response to the AMF 218 with the same message (7228); AMF 218 then sends a session deactivation response N1 to SMF 220 with the same message (7230).

Using the method that AMF may not save PDU session state and SMFs subscribe to even UE mobility notification, another embodiment of Intra AMF, handover between NG-RAN nodes without Xn interface can be obtained as follows. 78 illustrates in a message processing flowchart an example of an Intra AMF procedure (7800), between NG-RAN nodes without an Xn interface, in accordance with embodiments of the present invention. Downlink UP data may be transmitted (7802) between UPF 212 and UE 202 via S-RAN 204. An event may occur that causes S-RAN 204 to initiate a move across N2 (7804). The S-RAN 204 may send a handover request message (7806) to the AMF 218. The message (7806) may include a target identifier, a source-to-target transparent container, and PDU session identifiers. The source-to-target transparent container may include (R)AN information generated by S-RAN 204 to be used by T-RAN 204t and transparent to 5GCN. All PDU sessions handled by the S-RAN 204 (ie, all existing PDU sessions with active UP connections) may be contained in a handover required message (7806) indicating which of these PDU sessions the S-RAN 204s is requesting for handover.

AMF 218 may send a PDU handover request message (7808) to SMF 220. The message may include a PDU session ID and a target ID, and may be sent for each specified PDU session by S-RAN 204s as handover candidate N2. The PDU session ID indicates the PDU session candidate for N2 handover. The AMF 218 may send a separate message to the SMF 220 that has subscribed to the UE's mobility event notification. The message includes the target (R)AN. SMF 220 may decide to select a new UPF to serve deactivated PDU sessions. If a new UPF is selected, SMF 220 sends a session establishment request with session contexts PDUs to the newly selected UPF. The SMF then requests the previously used UPF to release the PDU session contexts. Alternatively, the SMF may establish an N9 connection between the new UPF and the previously used UPF. The AMF 218 may send a separate UE mobility event notification message (7808) to the SMF 220 that the SMF subscribes to the "UE Mobility Event Notification" AMF service in 5.2.2.2 of TS 23.502, version 0.3.0 published March 2017, for the event "serving cell change". The notification may include a new serving cell PDU session identifier(s), which is a target identifier.

The SMF 220 may send a PDU handover response message (7810) (7810) to the AMF 218. The message (7810) may include a PDU session ID and N2 SM information. The SMF 220 may select a UPF 212 that supports N3 connection to the target (R) AN 204t. The SMF 220 may check whether an N2 handover for the specified PDU session can be received and may include the result in the N2 SM information transparently sent to the AMF 220 in the T-RAN 204t. If the N2 handover for the PDU session is received, the N2 SM information may also include the PDU session ID, the N3 UP address and the UPF 212 tunnel ID, and the QoS parameters.

The AMF 218 monitors PDU handover response messages (7812) from the involved SMFs 220. The smallest value of maximum delay indications for PDU sessions that are handover candidates gives the maximum time that AMF 218 can wait for a PDU handover response message (7810) before continuing the N2 handover procedure. . After the maximum timeout has elapsed or when all PDU handover response messages have been received, the AMF 218 continues the N2 handover procedure (handover request message at step (7820).

AMF 218 may send a PDU handoff cancel message (7814) to SMF 220. The message (7814) may include a PDU session identifier. The PDU handover response message (7810) arriving too late is indicated by the SMF 220, allowing the SMF 220 to release the possibly allocated N3 UP address and tunnel ID for the selected UPF 212. Note that the PDU change request message (7816) sent by the AMF 218 to the SMF 220 , and the PDU change response message (7818) sent by SFM 220 to AMF 218 starts at step (7812) and is executed in parallel with this and later steps.

AMF 218 may send a handover request message (7820) to T-RAN 204t. The message (7820) may include a source-to-target transparent container, N2 MM information, and N2 SM information list. AMF 218 may determine and/or select T-RAN 204t based on the target ID. AMF 218 may allocate a GUTI valid for UE 202 in AMF 218 and target TAI. The source-to-target transparent container may be forwarded as received from S-RAN 204. The N2 MM information may include, for example, security information and a handover restriction list. The SM N2 information list may include SM N2 information from SMF 220 in PDU handover response messages (7814) received before the end of step (7814).

The T-RAN 204t may send a handover request confirmation message (7822) to the AMF 218. The message (7822) may include a source-to-target transparent container, a list of SM N2 responses, and a list of unestablished session PDUs. The source-to-target transparent container may include a UE 202 container with an access layer part and a NAS part. The container of UE 202 may be sent transparently via AMF 218 and S-RAN 204 to UE 202. The information provided to S-RAN 204 may also include a list of PDU session identifiers indicating PDU sessions that failed to establish and the reason for the failure. (e.g. SMF decision 220, SMF 220 response too late, or T-RAN decision 204t). The N2 SM response list includes, for each N2 SM information received and N2 handover PDU session received SMF 220, a PDU session ID and an N2 SM response indicating the PDU session ID and if the T-RAN 204t received an N2 handover request for the PDU session. For each N2 handover PDU session received by the T-RAN 204t, the N2 SM response may include an N3 UP address and a T-RAN 204t tunnel ID, as well as a list of received QoS flows. For PDU sessions that T-RAN 204t rejects, T-RAN 204t may delete PDU session contexts.

The AMF may send a PDU change request message (7824) to the SMF 220. The message (7824) may include a PDU session identifier and an SM N2 response. For each T-RAN 204t received SM N2 response (included in the SM N2 response list), AMF 218 may send a received SM N2 response to the SMF 220 indicated in the corresponding PDU session ID.

The SMF 220 may send a PDU change response message (7826) to the AMF 218. The message (7826) may include a PDU session identifier, and a message (7826) may be sent for each PDU change request message (7824) received. The SMF 220 may prepare for the N2 handover by specifying the N3 UP address and the T-RAN tunnel ID 204t to the UPF 212 if the N2 handover is received by the T-RAN 204t. If the N2 handover is not received by the T-RAN 204t, the SMF 212 may decide whether to unlock or deactivate the session PDU. To release a session PDU, the SMF initiates the session PDU release procedure described in 4.3.4 in TS 23.502 version 0.3.0 published March 2017. To deactivate sessions, the SMF PDU sends a session change request N4. in UPF for these PDU sessions. The message indicates release of (R)AN N3 tunnel information ((R)AN address and tunnel endpoint identifier for downlink user plane), buffering command, reactivation timer). The buffering command shall indicate whether the UPF should buffer incoming downlink packets.

The reactivation timer indicates the duration that a deactivated PDU session UP remains in the deactivated state after the UPF deletes the N3 (R)AN tunnel information. Before the reactivation timer expires, the UPF shall buffer the downlink packets in accordance with the buffering command. After the response timer expires, the UPF shall buffer the downlink packets in accordance with the buffer command. If UPF receives a downlink packet before or after the reactivation timer expires, UPF sends a downlink packet notification to the SMF to initiate a network initiated service request.

The SMF 220 acknowledges the change request message (7824) by sending a PDU change response message (7826) to the AMF 218. For PDU sessions that are deactivated, the message (7826) may include an N1 SM (session deactivate) message container Request (ID(s) ) session PDU, reactivation timer The SMF stores the deactivation state of the session(s) of the deactivated PDU.

The AMF may send a handover command message (7828) to the S-RAN 204. The message (7828) may include a source-target transparent container, a list of PDU sessions that failed to establish, and an N1 SM message container received in the message ( 7826). The source-target transparent container may be redirected as received from AMF 218. S-RANs 204 may use the list of PDU sessions that failed to set up and the indicated failure reason to determine whether to proceed with the procedure. handover N2.

S-RAN 204 may send a handover command message (7830) to UE 202. The message may include a UE 202 container and an N1 SM message container. The container of UE 202 may be sent transparently from T-RAN 204t via AMF 218 to S-RAN 204 and provided to UE 202 via S-RAN 204.

After UE 202 has successfully synchronized (7832) with the target cell, it may send a handover confirmation message (7834) to T-RAN 204t. According to this message, UE 202 considers the handover successful. The message may include an N1 SM acknowledgment (PDU session identifier(s)) for successfully switched and deactivated PDU sessions. For deactivated PDU sessions, UE 202 maintains the PDU session(s) deactivated state. UE 202 does not send an uplink request for the reactivation timer. This timer may be set by a setting in the policy of the UE 202 or by a message from the SMF 220.

The T-RAN 204t may then send a handover notification message (7838) to the AMF 218. The message (7838) may contain the N1 SM acknowledgment received by the UE in the message (7834). According to this message, the handover is considered successful in T-RAN 204t. AMF 218 may then send a handover complete message (7840) to SMF 220. The message may include a PDU session identifier and an N1 SM message from UE 202. A handover complete message (7840) may be sent to each PDU session for the corresponding SMF 220, indicating successful handover N2.

The SMF 220 may send a handover complete ACK message (7842) to the AMF 218. The message (7842) may include a PDU session identifier. SMF 220 may indicate to the selected UPF 212 that the downlink user plane for the specified PDU session may switch to T-RAN 204t. For PDU sessions that are not supported by T-RAN 204t and are deactivated, SMF 220 may notify the selected UPF 212 to remove (R)AN N3 tunnel information, reactivation timer, and buffering command. Thus, the SMF 220 may acknowledge receipt of the handover complete message. AMF 218 may send a UE context release command message (7846) to S-RAN 204s. The S-RAN 204 may then send a UE context release complete message (7848) to the AMF 218. The source (R) AN 204 may release its resources associated with the UE 202 and respond with a UE context release complete message (7846).

Session PDU release requested by UE or network for non-roaming and break-local roaming

In FIG. 80 illustrate an exemplary embodiment including both a session PDU release procedure requested by a UE and a session PDU release procedure requested by a network. This procedure allows the UE to request the release of one session PDU. The procedure also allows the SMF or PCF to initiate release of the session PDU. In the case of LBO, the procedure is the same as in the case of no roaming, with the difference that SMF, UPF and PCF are in the visited network.

The procedure of FIG. 80 initiate one of the following options:

• Step 8002a: The UE initiates the session PDU release procedure requested by the UE by transmitting a session PDU release request message (Session PDU ID) N1 SM. The N1 message is forwarded to the (R)AN in the 5G core network with information about the user's location. This message is relayed to the SMF corresponding to the session ID of the PDU via N2 and AMF. Depending on the type of access, when the UE is in the CM-IDLE state, the UE may initiate a service request procedure before releasing the session PDU.

• Step 8002b: The PCF may initiate a session PDU-CAN change procedure to request a release of the session PDU.

• Step 8002c: The SMF may initiate release of the session PDU, eg, based on a request from the DN (deauthorization of the UE to access the DN) or based on a request from the UDM (subscription change) or from the OCS. The release procedure may also be triggered based on local policy (eg, the release procedure may be associated with a UPF move for a Mode 2/Mode 3 SSC).

When the SMF receives any of the triggers in step 8002a-8002c, the SMF starts a session PDU release procedure.

Step 8004: The SMF releases the IP address/prefix(es) that were allocated to the session PDU and releases the corresponding user plane resources:

• Step 8004a: The SMF sends an N4 session release request message (N4 session ID) to the UPF. The UPF may discard any remaining session PDUs and release all tunnel resources and contexts associated with the N4 session.

• Step 8004b: The UPF acknowledges the N4 session release request by sending an N4 session release response message (N4 session ID) to the SMF.

If multiple UPFs associated with a session PDU are used, a session release request procedure (steps 8004a and 8004b) may be performed for each UPF.

Step 8006: The SMF sends a request message N11 to the AMF (resource release request SM N2, SM information N1 (session PDU release command)).

The SMF generates SM N1 information including a session PDU release command message (PDU session ID, reason). The cause may indicate a trigger to establish a new session PDU with the same characteristics (eg, when procedures associated with SSC mode 2 are called).

SSC mode 2 is defined in clause 5.6.9. TS 23.501

If the session PDU UP connection is active, the SMF shall also generate an SM N2 request to release (R)AN resources associated with the session PDU (N2 resource release request (session PDU ID)).

If the session PDU is deactivated, the SMF may send a session release indication and session ID of the PDU to the AMF.

The SMF sends an AMF message to the AMF (Resource Release Request SM N2, SM Container N1 (Session PDU Release Command), Session PDU Release Indication, Session PDU Identifier) to the AMF. The session PDU release indication informs the AMF of the session PDU release notification. The AMF may skip sending the N1 SM container to the UE when the UE is in the CM-IDLE state.

Step 8008: If the UE is in the CM-IDLE state, the AMF may acknowledge step 8006 at step 8014; and steps 8008 through 8012 and 8016 may be omitted.

The UE and 5GC will be synchronized regarding the status of the (released) session PDU at the next service request or registration procedure.

If the UE is in the CM-CONNECTED state, then the AMF sends the message received from the SMF in step 8006 (N2 SM resource release request, N1 SM information) to the (R)AN.

Step 8010: If the (R)AN receives an N2 SM request to release the AN resources associated with the session PDU, then generate a special signaling exchange with the UE to release the corresponding AN resources.

In the case of the 3GPP RAN, an RRC connection may be reconfigured with the UE releasing the RAN resources associated with the session PDU.

During this procedure, the (R)AN sends any NAS message (N1 SM session PDU release command) received from the AMF in step 8008. If the (R)AN only receives the N1 SM container (session PDU release command), the (R)AN sends these messages to the UE.

The UE confirms the session PDU release command by sending a session PDU acknowledgment message via the N1 SM signaling sent via the (R)AN.

Step 8012: [Conditional] If the (R)AN has received the N2 SM AN resource release request, the (R)AN confirms the N2 SM resource release request by sending the N2 SM resource release acknowledgment (N1 SM) information message (session PDU release acknowledgment), information user location) in AMF. Otherwise, the (R)AN simply forwards the SM N1 (session PDU release acknowledgment) information from the UE to the AMF.

Step 8014: If the UE is in the CM-CONNECTED state, the AMF sends a response message (N2 SM Resource Release Confirmation) to N11 to forward the message received from the (R)AN in step 6 to the SMF. If the UE is in the CM-IDLE state, the AMF sends an N11 response message (session release acknowledgment, session PDU ID) to the SMF. The AMF may remove all contexts (including the session ID of the PDU) associated with the session PDU.

Step 8016: If the session PDU is up, the SMF notifies the AMF that the session PDU has been released. The AMF and SMF may delete all contexts (including the PDU session ID) associated with the session PDU. In some embodiments, may take the form of Nsmf_PDU Session Event Report Notification (AMF): The SMF sends a session PDU event report notification (N11 message), as defined in clause 5.2.8.1, to the AMF; the event trigger is the release of the session PDU.

Step 8018: If dynamic PCC is applied to this session, the SMF initiates a session PDU-CAN termination procedure. The SMF notifies any entity that has subscribed to the user location information associated with the session PDU change. If it is the last session PDU being processed for the UE, then the SMF releases the association with the UDM. The order in which the SMF releases resources is implementation dependent. If the session PDU is deactivated, then step 8018 may be performed in parallel, before or after step 8006.

Alternative Embodiments A

In alternative embodiments, steps 8006 through 8018 may be performed as follows:

Step 8006: The SMF sends an N11 message to the AMF (N2 SM session PDU release request, N1 SM session PDU release request, N11 session PDU release notification). The N1 SM session PDU release request includes a session PDU identifier, a reason. The cause may indicate a trigger to establish a new session PDU with the same characteristics (eg, when procedures associated with SSC mode 2 are called).

SSC mode 2 is defined in TS 23.501 [2], clause 5.6.9.

The N2 Session PDU Release Request SM is for releasing (R)AN resources associated with the session PDU (N2 Resource Release Request (PDU Session ID)). The session PDU release notification N11 includes the PDU session identifier for the AMF to remove the context of the session PDU.

If Session PDU UP is enabled, the SMF sends an N1 SM PDU Session Release Request and an N2 SM PDU Session Release Request via the AMF.

If the PDU session UP is deactivated and if the SMF does not subscribe to the Namf_EventExpose AMF service for CM UE state changes, the SMF sends an SM message N1 to the UE via the AMF.

If the session PDU UP is deactivated and the SMF knows that the UE is in the CM-IDLE state, the SMF sends an N11 session PDU release request. Otherwise, if the SMF knows that the UE is in the CM-CONNECTED state, the SMF sends an SM session PDU release request to N1.

In some embodiments, this may take the form of Namf_Message Transfer (SMF): The SMF requests the Namf_Message Transfer AMF service defined in 5.2.2.4 to send N1 SM and N2 SM messages to the UE and (R)AN.

Step 8008: if the UE is in the CM-IDLE state, and a session PDU release notification N11 is received, the AMF acknowledges step 8006 at step 8014; and steps 8008 to 8012 and 8016 are skipped. If the UE is in the CM-IDLE state and an SM message N1 is received, the AMF sends a delivery rejection in step 8014; steps 8008 to 8012 and 8016 are skipped.

The UE and 5GC will be synchronized regarding the status of the (released) session PDU at the next service request or registration procedure.

If the UE is in the CM-CONNECTED state, then the AMF sends the message received from the SMF in step 3 (N2 SM session PDU release request, N1 SM session PDU release request) to the (R)AN.

8010: If the (R)AN receives an N2 session PDU release request, the SM generates a special signaling exchange with the UE to release the corresponding AN resources to release the AN resources associated with the session PDU. In the case of the 3GPP RAN, an RRC connection may be reconfigured with the UE releasing the RAN resources associated with the session PDU. During this procedure, the (R)AN sends any NAS message (Release Request PDU Session SM N1) received from the AMF in step 8008.

If the (R)AN only receives the N1 SM container (session PDU release request), the (R)AN forwards these messages to the UE. The UE acknowledges the session PDU release request by sending a session PDU release ACK message via N1 SM signaling sent via the (R)AN.

8012: [Conditional] If the (R)AN received the N2 SM AN resource release request, the (R)AN confirms the N2 SM session PDU release request by sending the N2 SM session PDU release acknowledgment (N1 SM info (session PDU release acknowledgment), information about user location) in AMF. Otherwise, the (R)AN simply forwards the SM N1 (session PDU release acknowledgment) information from the UE to the AMF.

8014: If the UE is in the CM-CONNECTED state, the AMF sends an N11 response message (N2 SM session PDU release acknowledgment) to forward the message received from the (R)AN in step 6 to the SMF. If the UE is in the CM-IDLE state and the AMF has received the session PDU release notification N11 in step 3, the AMF sends a response message N11 (session PDU release acknowledgment, session PDU identifier) to the SMF. If the UE is in the CM-IDLE state and the AMF has received the SM message N1 in step 3, the AMF sends a delivery failure message to the SMF indicating the CM-IDLE state of the UE. The AMF and SMF may remove all contexts (including the session PDU ID) associated with the session PDU.

8016: If the session PDU is up, the SMF sends an N11 session PDU release notification to the AMF. The AMF and SMF may remove all contexts (including the PDU session ID) associated with the PDU session. In some embodiments, the implementation takes the form Nsmf_PDU Session Event Report Notification (AMF): The SMF sends a session PDU event report notification (N11 message) as defined in clause 5.2.8.1 to the AMF; the event trigger is the release of the session PDU.

8018: If dynamic PCC is applied to this session, the SMF initiates a session PDU-CAN termination procedure. The SMF notifies any entity that has subscribed to the user location information associated with the session PDU change. If this is the last session PDU processed for the UE, the SMF releases the association with the UDM. The order in which the SMF releases resources is implementation dependent. If the session PDU is deactivated, step 8018 may be performed in parallel, before or after step 8006.

Alternative options In the implementation

In further alternative embodiments, steps 8006 through 8018 may be performed as follows:

Step 8006: The SMF sends N2 SM session PDU release request, N1 SM session PDU release request, N11 session PDU release notification to the AMF. The N1 SM session PDU release request includes the PDU session ID, reason. The cause may indicate a trigger to establish a new PDU session with the same characteristics (eg, when procedures associated with SSC mode 2 are called). SSC mode 2 is defined in clause 5.6.9 of TS 23.501 [2].

The N2 Session PDU Release Request SM is for releasing (R)AN resources associated with the session PDU (N2 Session PDU Release Request (Session PDU ID)). The N11 session PDU release notification includes the PDU session identifier for the AMF to remove the PDU session context. If the session PDU UP is enabled, the SMF sends an N1 session PDU release request to SM and an SM session PDU release request to N2. If the UE is unavailable, the SMF sends a session PDU release notification N11. If the session PDU UP is deactivated, the SMF sends a session PDU release request to the N1 SM.

In some embodiments, this may take the form of Namf_Message Transfer (SMF): The SMF requests the Namf_Message Transfer AMF service defined in 5.2.2.4 to send N1 SM and N2 SM messages to the UE and (R)AN.

Step 8008: if the UE is in the CM-IDLE state and the SM N1 message is received, the AMF discards the SM N1 message and acknowledges step 8006 in step 8014; and steps 8008 to 8012 are skipped. The UE and 5GC will be synchronized regarding the status of the (released) session PDU at the next service request or registration procedure.

If the UE is in the CM-CONNECTED state, then the AMF sends the message received from the SMF in step 3 (N2 SM session PDU release request, N1 SM session PDU release request) to the (R)AN.

Step 8010: When the (R)AN has received the N2 SM session PDU release request to release the AN resources associated with the session PDU, it issues a special signaling exchange with the UE to release the corresponding AN resources. In the case of the 3GPP RAN, an RRC connection may be reconfigured with the UE releasing the RAN resources associated with the session PDU. During this procedure, the (R)AN sends any NAS message (N1 SM session PDU release request) received from the AMF in step 8008.

If the (R)AN only receives the N1 SM container (session PDU release request), the (R)AN forwards this message to the UE. The UE acknowledges the session PDU release request by sending a session PDU release Ack message via the N1 SM signaling sent on the (R)AN.

Step 8012: [Conditional] If the (R)AN has received the N2 SM AN resource release request, the (R)AN acknowledges the N2 SM session PDU release request by sending an N2 SM session PDU release acknowledgment (N1 SM information (session PDU release acknowledgment), information user location) in AMF. Otherwise, the (R)AN simply forwards the SM N1 (session PDU release acknowledgment) information from the UE to the AMF.

Step 8014: If the UE is in the CM-CONNECTED state, the AMF sends an N11 response message (N2 SM session PDU release acknowledgment) to forward the message received from the (R)AN in step 6 to the SMF.

If the AMF has received the session PDU release notification N11 in step 8006, the AMF sends a response message N11 (session PDU release confirmation, session PDU ID) to the SMF, and step 8016 is skipped. The AMF and SMF may remove all contexts (including the PDU session ID) associated with the session PDU.

If an SBA message is used, then the N11 response message (session PDU release acknowledgment, session PDU identifier) may not be required.

If the UE is in the CM-IDLE state and the AMF has received the SM message N1 in step 8006, the AMF sends a delivery failure message to the SMF with a reason code indicating the CM-IDLE state of the UE. This is especially applicable to cases where the process starts at any of steps 8002b or 8002c.

Step 8016: The SMF sends an N11 session PDU release notification to the AMF. The AMF and SMF may remove all contexts (including the PDU session ID) associated with the session PDU. In some embodiments, this may take the form of Nsmf_PDU Session Event Report Notification (AMF): The SMF sends a session PDU event report notification (N11 message) as defined in clause 5.2.8.1 to the AMF; the event trigger is the release of the session PDU.

Step 8018: If dynamic PCC is applied to this session, the SMF initiates a session PDU-CAN termination procedure. The SMF notifies any entity that has subscribed to the user location information associated with the session PDU change. If this is the last session PDU processed for the UE, the SMF releases the association with the UDM. The order in which the SMF releases resources is implementation dependent. If the session PDU is deactivated and the SMF knows the state of the CM, step 8018 may be performed in parallel, before or after step 8006.

Alternative C implementation

In further alternative embodiments, steps 8006 through 8018 may be performed as follows:

Step 8006: The SMF sends an AMF (resource release request SM N2, information SM N1). The N1 SM information includes a session PDU release command message (PDU session ID, reason). The cause may indicate a trigger to establish a new PDU session with the same characteristics (eg, when procedures associated with SSC mode 2 are called). SSC mode 2 is defined in TS 23.501, clause 5.6.9. The N2 SM session PDU release request (session PDU identifier) is for releasing (R)AN resources associated with the session PDU.

If the session PDU UP is enabled, the SMF sends an N1 SM session PDU release command and an N2 SM resource release request via a Namf_Communication_N1MessageTransfer and a Namf_Communication_N2MessageTrigger service operation, respectively.

If the session PDU UP is deactivated, the SMF requests the UE to release the session PDU by calling Namf_Communication_N1MessageTransfer (SM message N1 (session PDU release command), skip indication). If the UE is in the CM-IDLE state and the AMF receives the SM N1 message with a skip indication, the AMF discards the SM N1 message and notifies the SMF "message not sent with reason code"; steps 8008 to 8014 are skipped. "Gap indication" is possible and is described in clause 5.2.2.2.7 of TS 23.502.

If the UE is not available, the SMF notifies the AMF that the session PDU has been released by calling Nsmf_EventExposure_Notify(session PDU release indication, session PDU identifier). The AMF and SMF shall remove all contexts (including the PDU session ID) associated with the session PDU, as well as any event subscriptions from the SMF to the AMF. Steps 8008 to 8016 are skipped.

If the procedure is initiated to move the Session PDU Binding Session PDU in SSC Mode 2, it is assumed that the SMF does not include a "skip indication".

The UE and 5GC will be synchronized with respect to the (released) PDU session status at the next service request or registration procedure.

Step 8008: If the UE is in the CM-IDLE state and no skip indication is received, the AMF initiates a network initiated service request procedure to send N1 SM information to the UE.

If the UE is in the CM-CONNECTED state, then the AMF sends the message received from the SMF in step 3 (Release SM N2 resource request, SM information N1) to the (R)AN.

Step 8010: When the (R)AN has received the N2 SM request to release the AN resources associated with the session PDU, it issues a special signaling exchange with the UE to release the corresponding AN resources.

In the case of the 3GPP RAN, the RRC connection may be reconfigured in case the UE releases the RAN resources associated with the session PDU.

During this procedure, the (R)AN sends any NAS message (N1 SM session PDU release command) received from the AMF in step 8008.

The UE acknowledges the session PDU release command by sending a session PDU release acknowledge message via the N1 SM signaling sent via the (R)AN.

Step 8012 [Conditional] If the (R)AN has received the N2 SM AN resource release request, the (R)AN confirms the N2 SM resource release request by sending the N2 SM resource release acknowledgment (N1 SM information message (session PDU release acknowledgment), information about user location) in AMF.

Otherwise, the (R)AN simply forwards the SM N1 (session PDU release acknowledgment) information from the UE to the AMF.

Step 8014: The AMF invokes the SMF Namf_Communication_N1MessageNotify (N1 Release SM Ack) as defined in clause 5.2.2.2.4 of TS 23.502. The AMF invokes the SMF Namf_Communication_N2InfoNotify (SM N2 resource release confirmation) as defined in 5.2.2.2.11 of TS 23.502.

Step 8016: The SMF notifies the AMF that the PDU session has been released by calling the Nsmf_EventExposure_Notify service operation as defined in clause 5.2.8.3.2 of TS 23.502. The AMF and SMF shall remove all contexts (including the PDU session ID) associated with the session PDU, as well as any event subscriptions from the SMF to the AMF.

Step 8018: If dynamic PCC is applied to this session, then the SMF initiates a session PDU-CAN termination procedure. The SMF notifies any entity that has subscribed to the user location information associated with the PDU session change. If this is the last session PDU it processes for the UE, the SMF releases the association with the UDM. The order in which the SMF releases resources is implementation dependent. If the PDU session is deactivated and the SMF knows the state of the CM, step 9 may be performed in parallel, before or after step 3.

In Alternative Embodiment C, the operation of the Namf_Communication_N1MessageTransfer service is described as follows.

Service operation name: Namf_Communication_N1MessageTransfer.

Description: CN NF request to send downlink message N1 to UE via AMF.

Known NF consumers: SMF, SMSF, PCF, NEF

Required input: CN NF ID, message container(s)

Inputs possible: an indication of the subscription whether the time reference is sent to the AMF for subsequent notification of the response message. The "Ignore Indication" indicates that the AMF should skip sending the N1 SM container to the UE if the UE is in the CM-IDLE state.

Required output: Result indication includes "passed" and "not passed with cause".

Output possible: None.

See 4.3.2.2.1 step 10, 4.3.2.2.2 step 14 and 4.13.3.6 step 5a for details of this service operation. If the AMF does not have an N1 context for the UE, and if the UE is in the CM-IDLE state, the AMF initiates a network initiated service request procedure as specified in clause 4.2.3.4. The AMF replies to the NF consumer with a Namf_Communication_N1MessageTransfer response, providing a result indication of whether the AMF was able to successfully transmit the N1 message to the UE.

In some embodiments, an explicit subscription (Namf_Communication_N1MessageSubscribe) for an N1 response message type may combine a Namf_Communication_N1MessageTransfer service operation call.

Providing the option not to save
session PDU states in AMF and updates to related procedures

Some TS 23.502 procedures, such as UE context release in AN and handover procedures, assume that the AMF keeps the state of the session PDU (activated or deactivated). However, this assumption violates the separation principle between AMF and SMF. Alternative solutions that do not require knowledge of the state of the session PDU in the AMF are described below.

Clause 5.2.2.3 of TS 23.502 specifies that the AMF also provides the "event detection" service. Accordingly, an SMF may subscribe to this service if the SMF serves at least one PDU session of a particular RAT. The SMF may subscribe to this service even if all of the PDU sessions it serves are deactivated. With regard to UE context release in the AN procedure, the SMF may subscribe to "event detection" caused by the CM's state change from the CONNECTED state to the IDLE state when the UE requests session establishment or session activation. The AMF then simply needs to notify the SMF of the CM state transition in the CM-IDLE, to the signed SMF. The SMF decides on the appropriate action.

The SMF may subscribe to the AMF's "Namf_EventExposure" service in the session establishment and service request procedures.

The SMF may subscribe to the AMF's "Namf_Communication_N2InfoSubscribe" service as defined in clause 5.2.2.2.9 of TS 23.502 to receive N2 UE context release request notification from the (R)AN to the AMF. The SMF performs the Namf_Communication_N2InfoSubscribe service operation in the session establishment and service request procedures.

In the service request procedures in TS 23.502, the AMF may reject the service activation request. It is also possible that the (R)AN may not have the resources to service the PDU session, in which case the (R)AN may also reject the PDU session establishment request. To implement this functionality, the procedures defined in TS 23.502 can be revised as follows:

Clause 4.3.2.2.1 without roaming and roaming with local interruption

Step 16: SMF in AMF: SM (reason) response.

After this step, the AMF forwards appropriate events to the SMF, such as on handover when (R)AN the tunnel information changes or the AMF moves.

The SMF may subscribe to the Namf_EventExposure AMF (UE ID, event filter) service as defined in clause 5.2.2.3. The event filter is "CM state change to CM-IDLE".

The SMF may subscribe to N2 messages of type SM and N2 UE Context Release Request using the Namf_Communication_N2InfoSubscribe AMF service operation as defined in clause 5.2.2.2.9.

Clause 4.3.2.2.2. Roaming with home routing

Step 20. This step is the same as step 16 in 4.3.2.2.1 with the following differences:

• SMF is V-SMF

Clause 4.2.6. UE context release in AN

This procedure is used to release the N2-AP signaling logical connection and associated user plane N3 connections.

When N2-AP signaling connection is lost due to (R)AN or AMF failure, UE context release in AN procedure is performed locally by AMF or (R)AN as described in the flow below without using or relying on any of the signaling shown between (R)AN and AMF. The release of the UE context in the AN results in the deactivation of all UE PDU sessions.

Initiation of UE context release in an AN procedure may be due to:

• (R)AN-triggered by cause, eg, O&M intervention, unspecified failure, AN link failure (eg, radio), user inactivity, release due to connection reset generated by UE, etc.; or

• AMF-triggered for a reason, such as an unspecified failure, etc.

Both (R)AN-triggered and AMF-triggered UE context release in AN procedures are shown in FIG. 81. Referring to the drawing:

Step 8102: In the presence of some acknowledged AN conditions (eg, radio failure) or other internal reason, the (R)AN, (R)AN may decide to initiate UE context release at the AN. In this case, the (R)AN sends an N2 UE context release reason request message to the AMF. Reason indicates the reason for the reset (e.g. connection failure, O&M intervention, unspecified failure, etc.). The decision to initiate release of the UE context in the AN procedure may also be triggered by an internal AMF event.

Step 8104: [Conditional] For each of the session PDUs serving SMFs that are subscribed to Namf_EventExposure_Subscribe, the AMF performs Namf_EventExposure_Notify as described in clause 5.2.2.3.4. In some embodiments, the (R)AN information may be used in cases where the UE has multiple connections. Alternatively, the mobility event container may contain a list of PDU session IDs.

Alternative implementation of step 8104:

Step 8104a: [Conditional] For each of the SMFs serving session PDUs that are subscribed to Namf_Communication_N2InfoSubscribe for the N2 information type N2 UE context release request, the AMF performs a Namf_Comunication_N2InfoNotify service operation as described in clause 5.2.2.2.11 to notify the PDU session ID, release reason (UE N2 context release request).

The AMF may send (R)AN information to the SMF in case the UE has multiple connections. Alternatively, the AMF may send a list of PDU session IDs.

Step 8104b: [Conditional] The SMF sends a response to the AMF on the message received in step 8104a.

Step 8106a: [Conditional] SMF in UPF: session change request N4 (AN tunnel information to be deleted, buffering on/off). The SMF initiates session change procedure N4 indicating that the AN tunnel information needs to be deleted. Buffering Enable/Disable indicates whether the UPF can buffer an incoming DL PDU or not. See clause 4.4 for more details.

Step 8106b: [Conditional] UPF in SMF: N4 session change response acknowledging the SMF request. See clause 4.4 for more details.

Step 8108a: The SMF sends an N2 context release command to the AMF via a Namf_Communication_N2MessageTrigger service operation as defined in clause 5.2.2.2.8 of TS 23.502.

Step 8108b: The AMF sends a response message to step 8108a.

Step 8108c. The SMF may perform Namf_Communication_N2InfoUnsubscribe for a specific N2 information type, such as a U2 NE context release request, as defined in 5.2.2.2.10 of TS 23.502.

Step 8108d: [Conditional] The SMF may execute the Namf_EventExposureUnSubscribe procedure for some types of UE mobility events as defined in clause 5.2.2.3.3 of TS 23.502.

Step 8110: After the AMF collects all the N2 context release commands in step 4 from the SMF(s) that were notified in step 2, the AMF sends a UE Context Release Request (R) to the N2 AN. If the AN is a RAN, this step is detailed in the RAN specifications. In case the AN is an N3IWF, this step is described in clause 4.12.

This step may be performed before, in parallel with, or after step 8104, as desired.

Step 8112: If the AN connection (eg, RRC connection) with the UE has not yet been released (step 8102), the (R)AN requests the UE to release the AN connection. Upon receiving the AN connection release confirmation from the UE, the (R)AN deletes the UE context.

Step 8114: The (R)AN acknowledges the release of N2 by returning a UE N2 context release complete message to the AMF. This releases the signaling connection between the AMF and the (R)AN for that UE.

During the procedure of FIG. 81, the AN may provide location information to the AMF.

Clause 4.2.3.2 Service request initiated by UE in CM-IDLE state

In FIG. 82A and 82B illustrate an example procedure for a UE-initiated service request in a CM-IDLE state. This exemplary procedure also includes the aspects necessary to support network segmentation.

The service request procedure may be used by the 5G UE in the CM IDLE state to request the establishment of a secure connection with the AMF. The UE in the CM IDLE state initiates a service request procedure to send uplink signaling messages, user data, or a network paging response. Upon receiving the service request message, the AMF may perform authentication and the AMF may perform a security procedure. After establishing a secure signaling connection with the AMF, the UE or the network may send signaling messages, e.g., establishing a session PDU from the UE to the network, or the SMF through the AMF may start establishing a user plane resource for the session PDUs requested by the network and/or indicated in the service request message.

For any service request, the AMF may respond with a service response message to synchronize the state of the session PDU between the UE and the network. The AMF may also respond to the UE with a service failure message if the service request cannot be accepted by the network. To request a service due to user data, the network may take additional action if the user plane resource establishment was not successful.

The procedure described in this clause 4.2.3.2 applies to scenarios with or without an intermediate UPF and with or without an intermediate UPF reselection.

The procedure defined in clause 4.2.3.2 of TS 23.502 is not applicable to an access network (after the UE has registered with the network), in which the UE is always considered to be in the CM-CONNECTED state, and in which the user plane resource is always considered to be established for an active PDU session.

Referring to FIG. 82A and 82B:

Step 8202: UE at (R)AN: MM request NAS service (session PDU ID(s), security parameters, session PDU state). The UE sends a service request message to the NAS in an AMF encapsulated in an RRC message in the RAN. The RRC message(s) that can be used to carry the 5G temporary ID and NAS message is described in the RAN specifications. If a service request is initiated for user data, the UE includes the session PDU ID(s) in the NAS service request message to indicate the session(s) of the PDU to be used by the UE. If the service request is initiated for signaling only, the UE does not include the session ID of the PDU. When this procedure is initiated for a paging response, if the UE needs to use some PDU session(s), the UE adds the PDU session identifier(s) in the NAS MM service request message to indicate the PDU session(s) that the UE needs. Otherwise, the UE will not include any PDU session identifier. The PDU session state indicates the PDU sessions available at the UE. In some embodiments, the NAS service request may also include an indication of user data, signaling, or a paging response.

Step 8204: (R)AN in AMF: N2 message (MM NAS service request, 5G temporary ID, location information, RAT type, RRC establishment reason). The details of this step are described in the RAN specifications. If the AMF cannot process the service request, it will reject it. Temporary 5G ID received in RRC procedure. The RAN selects the AMF according to the temporary identifier. The location information and RAT type are related to the cell in which the UE is located. Based on the state of the session PDU, the AMF may initiate a session PDU release procedure if the session PDU is not available at the UE.

Step 8206: If the service request was not sent with integrity protection or the integrity protection is indicated as failed, the AMF may initiate the NAS authentication/security procedure as defined in clause 4.6. If the UE initiated a service request only to establish a signaling connection, after the security exchange, the UE and the network can send signals, and steps 8208 and 8214 to 8224 are skipped.

Step 8208: [Conditional] AMF in SMF: Message N11 (PDU session ID(s), reason(s), UE location information). Message N11 is sent in one or more of the following scenarios:

• If the NAS MM service request message includes PDU session IDs, or the procedure is initiated by an SMF, but the UE PDU session IDs correlate with other SMFs than the one that initiates the procedure, the AMF sends N11 SMF message(s) associated with the ID. (IDs) of the session PDU with the cause set to indicate "setting user plane resources" for the session PDU.

• If the UE was in MICO mode and the AMF notified the SMF that the UE is unreachable and that the SMF does not need to send DL data notifications to the AMF, the AMF informs the SMF that the UE is reachable.

The AMF may also notify any other NF that has subscribed to the reachability of the UE that the UE is reachable.

Step 8210: Based on the new location information, the SMF checks the UPF selection criteria in accordance with clause 6.3.3 of TS 23.501 [2] and decides to do one of the following:

• continue to use current UPFs;

• select a new intermediate UPF if the UE has moved out of the service area of the UPF that is connecting to the RAN while maintaining UPFs acting as a session PDU anchor; or

• initiate session PDU re-establishment in order to move the UPF acting as the session PDU anchor.

Step 8212a: [Conditional] SMF for new UPF: session establishment request N4. If the SMF selects the new UPF as the intermediate UPF for the session PDU, a new N4 session request message is sent to the new UPF providing the packet discovery, application, and reporting rules to be established in the intermediate UPF. The session PDU binding information for this session PDU is also provided to the intermediate UPF.

Step 8212b: new UPF (intermediate) for SMF: session establishment response N4. The new intermediate UPF sends an N4 session establishment response message to the SMF. In the case where the UPF extracts the CN tunnel information, provide the DL CN tunnel information and the UL tunnel information (ie, N3 CN tunnel information) to the SMF. The SMF starts a timer that will be used in step 17a to release the resource in the previously used intermediate UPF, if any.

Step 8214a: [Conditional] UPF SMF (PSA): N4 session change request. If the SMF selects a new UPF to act as the intermediate UPF for the session PDU, the SMF sends an N4 Session Change Request message to the Session PDU Anchor UPF (PSA), providing the DL tunnel information from the new intermediate UPF.

Step 8214b: UPF (PSA) to SMF: session change response N4. UPF (PSA) sends an N4 session change response message to the SMF.

Step 8216: [Conditional] SMF in AMF: N11 message (SM information N1 (PDU session ID, PDU session re-establishment indication), N2 SM information (PDU session ID, QoS profile, N3 CN tunnel information, S-NSSAI)) in AMF. Upon receiving an N11 message at 4 with a reason including "setting user plane resources", the SMF determines whether UPF reallocation is performed based on the UE location information, UPF service area, and operator policies:

• For the session PDU that the SMF determines to serve the current session PDU binding UPF in step 8210, the SMF generates only the N2 SM information and sends an N11 message to the AMF to establish the user plane. The N2 SM information contains information that the AMF can provide to the RAN.

• For session PDUs that the SMF determines that UPF remapping is required for session PDU binding UPF in step 8210, the SMF may send an N11 message containing only the N1 SM information to the UE via the AMF. The N1 SM information includes the corresponding PDU session identifier and the PDU session re-establishment indication, which is the same as step 2 described in clause 4.3.5.1.1 of TS 23.501 [2].

After receiving an N11 message in step 8208 indicating that the UE is reachable if the SMF has pending DL data, the SMF sends an N11 message to the AMF to set the user plane for the PDU sessions, otherwise, the SMF resumes sending DL data notifications to the AMF in case DL data.

Step 8218: AMF in (R)AN: request N2 (SM N2 information received from SMF, security context, AMF signaling connection ID, handover constraint list, MM NAS service confirmation). The RAN stores the security context, the AMF signaling connection identifier, the QoS information for the QoS flows of the activated PDU sessions, and N3 RAN tunnel identifiers in the context of the UE. This step is detailed in the RAN specifications. The list of handover restrictions is described in clause 5.3.4.1 of TS 23.501 [2] "Mobility restrictions". The NAS confirmation MM includes the session status of the PDU in the AMF. If the N1 SM information is received from step 8, the service confirmation message also includes the N1 SM information. The AMF may include at least one N2 SM information from the SMF if the procedure is initiated to set up a user plane session PDU. The AMF may send additional N2 SM information from the SMF in separate N2 messages (eg N2 tunnel establishment request), if any. Alternatively, if multiple SMFs are involved, the AMF may send one N2 request message to the (R)AN after receiving all N11 messages from the SMF. In such a case, the N2 request message includes the N2 SM information received in each of the N11 messages and information allowing the AMF to associate responses with the corresponding SMF.

Step 8220: (R)AN at UE: The RAN performs an RRC connection reconfiguration with the UE depending on the QoS information for all QoS flows of activated PDU sessions and radio bearers. This step establishes user plane security, which is detailed in the RAN specifications. The RAN forwards a service confirmation to the NAS MM to the UE. The UE locally deletes the session context of PDUs that are not available in the 5G CN. If the N1 message is present in the service acknowledgment and indicates that any session PDU should be re-established, the UE initiates re-establishment of the PDU session after completing the service request procedure. That is, for SSC mode 2, perform step 3 and step 4 as defined in clause 4.3.5.1.1. For SSC Mode 3, perform steps 3 and 4 as defined in clause 4.3.5.2.

Step 8222: After establishing a radio resource user plane, uplink data from the UE can now be forwarded to the RAN. The 5G RAN sends the uplink data to the UPF address and tunnel ID provided in step 4.

Step 8224: [Conditional] (R)AN in AMF: N2 request confirmation (N2 SM information (RAN Tunnel Information, List of Received QoS Flows for Activated PDU Sessions, List of Rejected QoS Flows for Activated Sessions PDUs) This step is detailed in the RAN specifications The message may include N2 SM information, such as RAN tunnel information.The RAN may respond with the N2 SM information with a separate N2 message (eg, N2 tunnel setup response) if the AMF sends a separate N2 message in step 8210. If in the N2 request message for step 8210 contains the multiple N2 SM information, the N2 request confirmation includes the SM information and the N2 set information to allow the AMF to associate responses with the corresponding SMF.

Step 8226: [Conditional] AMF in SMF: message N11 (SM information (RAN tunnel information) N2, RAT type) for each received session PDU for SMF. If the AMF has received the SM N2 information (one or more) in step 8, the AMF may forward the SM N2 information to the corresponding SMF. If the UE time zone has changed from the last reported UE time zone, the AMF may pad the UE time zone IE into this message.

Step 8228: [Optional] SMF in PCF: If a dynamic PCC is deployed, the SMF may initiate a session IP-CAN change and provide new location information to the PCF. Step 8230a: [Conditional] SMF for New Intermediate UPF: N4 Session Change Request (RAN Tunnel Information). If the SMF has selected a new UPF to perform the intermediate UPF function for the PDU session in step 5, the SMF initiates the N4 session change procedure and provides the RAN tunnel information.

Step 8230b: [Conditional] UPF in SMF: N4 session update response.

Step 8232a: [Conditional] The SMF may perform the Namf_Communication_N2InfoSubscribe service operation as defined in clause 5.2.2.2.9 for the N2 information type N2 UE context release request.

Step 8232b: [Conditional] The SMF may execute the Namf_EventExpose_Subscribe procedure as defined in clause 5.2.2.3.2 for specific UE mobility events. If desired, this step may be performed in conjunction with step 8216.

Step 8234a: [Conditional] SMF for previous intermediate UPF: N4 session change request or N4 session release request. If the SMF decides to continue using the previous intermediate UPF in step 5, the SMF sends a session change request to N4, providing the (R)AN with tunnel information. If the SMF has decided to select a new UPF to act as the intermediate UPF, the SMF initiates resource release after the timer expires in step 8212b by sending session release request N4 (release reason) to the previous intermediate UPF. If there is no intermediate UPF, the SMF sends an N4 session change request to the UPF PSA, providing the (R)AN with the tunnel information.

Step 8234b: previous intermediate UPF in SMF: N4 session change response or N4 session release response. The preceding UPF acknowledges with an N4 session change response or an N4 session release response to confirm the change or release of resources. If there is no intermediate UPF, the UPF PSA sends an N4 session change SMF response to acknowledge the resource change.

Clause 4.2.3.3 UE-initiated service request in CM-CONNECTED state

In FIG. 83A and 83B illustrate an example of a service request procedure initiated by a UE in a CM-IDLE state. This exemplary procedure also includes the aspects necessary to support network segmentation.

The network may take additional action if the user plane resource establishment was not successful.

The procedure in this clause 4.2.3.3 applies to scenarios with or without an intermediate UPF, and with or without an intermediate UPF reselection.

The procedure in this clause 4.2.3.3 of TS 23.502 is not applicable to the access network (when the UE is registered with the network) in which the UE is always considered to be in the CM-CONNECTED state and in which the user plane resource is always considered to be established for an active session PDU.

Referring to FIG. 83A and 83B:

Step 8302: UE at (R) AN: MM request NAS service (ID(s) of PDU session). The UE sends a NAS message service request in an AMF encapsulated in an RRC message to the RAN. The NAS MM message service request may be encrypted and integrity protected. The PDU session ID(s) in the NAS message service request message indicates the PDU session that the UE selects to activate.

Step 8304: (R)AN in AMF: N2 message (NAS MM service request). The details of this step are described in the RAN specifications. If the service request cannot be processed by the AMF, the AMF rejects it. The (R)AN sends an MM service request message to the AMF based on the existing N2 connection to the NAS.

Step 8306: [Conditional] AMF in SMF: message N11 (PDU session ID(s)). The AMF sends an N11 SMF message according to the PDU session IDs.

Step 8308: Based on the new location information, the SMF checks the UPF selection criteria in accordance with clause 6.3.3 of TS 23.501 [2]. If the UE has moved out of the UPF service area that connects the UE to the RAN, the SMF may select a new intermediate UPF.

Step 8310a: [Conditional] SMF for New Intermediate UPF: N4 Session Establishment Request, if the SMF selects a new intermediate UPF for the session PDU, an N4 Session Request message is sent to the new intermediate UPF providing packet discovery, provisioning and reporting rules to be installed on T-UPF. The session PDU binding information for this session PDU is also provided in the T-UPF.

Step 8310b: new UPF in SMF: session establishment response N4. The new UPF sends an N4 session establishment response message to the SMF. If the UPF allocates CN tunnel information, the UPF provides DL CN tunnel information and UL tunnel information (ie, N3 CN tunnel information) to the SMF. The SMF starts a timer that will be used in step 8417a to release the resource in the previous UPF, if any.

Step 8312a: [Conditional] SMF in UPF (PSA): session change request N4. If the SMF selects a new UPF to act as the intermediate UPF for the session PDU, the SMF sends an N4 change request message to the session PDU anchor UPF (PSA), providing the DL tunnel information for the new intermediate UPF.

Step 8312b: UPF (PSA) in SMF: session change response N4. UPF (PSA) sends an N4 session change response message to the SMF.

Step 8314: [Conditional] SMF in AMF: N11 message (SM information N2 (PDU session ID, QoS profile, N3 CN tunnel information, S-NSSAI)) to AMF SMF generates SM information N2 and sends N11 message to AMF to set user plane for PDU sessions. The N2 SM information contains information that the AMF can provide to the RAN.

Step 8316: [Conditional] AMF in (R) AN: N2 request (N2 information SM (QoS profile, CN N3 tunnel information) received from SMF, MM NAS service confirmation). If there are multiple PDU sessions that include multiple SMFs, the AMF need not wait for responses from all SMFs in step 8306b.

Step 8318: (R)AN at UE: The RAN performs an RRC connection reconfiguration with the UE depending on the QoS information for all QoS flows of activated PDU sessions and radio data bearers. The RAN forwards a service confirmation to the NAS MM to the UE.

Step 8320: After establishing the user plane radio resources for the selected session PDU, the uplink data from the UE can now be forwarded to the RAN. The 5G RAN sends the uplink data to the UPF address and tunnel ID provided in step 8314.

Step 8322: [Conditional] (R)AN in AMF: N2 Request Acknowledge (N2 SM information (RAN Tunnel Information, List of Received QoS Flows for Activated Session PDUs, List of Rejected QoS Flows for Activated Sessions PDUs) This step is detailed in the RAN specifications The message may include N2 SM information, eg, RAN tunnel information.The RAN may respond with the N2 SM information with a separate N2 message (eg, N2 tunnel setup response).

Step 8324: [Conditional] AMF in SMF: message N11 (SM information N2 (RAN tunnel information, QoS received flow list, QoS rejected flow list)) for each received PDU session in the SMF.

Step 8326: [Optional] SMF in PCF: If a dynamic PCC is deployed, the SMF may initiate a session IP-CAN change and provide new location information to the PCF.

Step 8328a: [Conditional] UPF SMF: N4 session update request (RAN tunnel information and list of received QoS flows). If the SMF selects a new UPF as the intermediate UPF for the PDU session in step 4, the SMF initiates the N4 session change procedure and provides the RAN tunnel information.

Step 8328b: [Conditional] UPF in SMF: N4 session update response.

Step 8330a: [Conditional] The SMF performs the Namf_Communication_N2InfoSubscribe service operation as defined in clause 5.2.2.2.9 for the N2 information type N2 UE context release request.

Step 8330b: [Conditional] The SMF may execute the Namf_EventExpose_Subscribe procedure as defined in clause 5.2.2.3.2 for specific UE mobility events. This step may be performed in conjunction with step 8314.

Step 8332a: [Conditional] SMF for previous UPF (interim): N4 session change request or N4 session release request. If the SMF decides to continue using the previous intermediate UPF in step 4, the SMF sends a session change request to N4, providing the (R)AN with tunnel information. If the SMF has decided to select a new UPF to act as the intermediate UPF in step 8308, the SMF initiates resource release after the timer expires in step 8312b by sending session release request N4 (release reason) to the previous intermediate UPF. If there is no intermediate UPF, the SMF sends an N4 session change request to the UPF PSA, providing the (R)AN with the tunnel information.

Step 8332b: previous UPF (intermediate) in SMF: N4 session change response or N4 session release response. The preceding UPF (intermediate) acknowledges with session release response message N4 to confirm the change or release of resources. If there is no intermediate UPF, the UPF PSA sends an N4 session change response to the SMF to acknowledge the resource change.

Based on the foregoing, it should be understood that aspects of the present invention provide any one or more of:

• A method for releasing a Packet Data Unit (PDU) session, the method comprising:

determining a session PDU release trigger;

sending a session release request message N4 to a user plane function (UPF);

receiving a N4 session release response message from the UPF;

sending a request N11 with a session PDU release command to an access and mobility function (AMF);

receiving an N11 response confirming the release of the session PDU from the AMF; And

sending message N11 to AMF.

• A handover method, the method comprising:

receiving an N2 path switch request from a target radio access network (T-RAN);

sending the message N11 to the session management function (SMF);

receiving an acknowledgment of message N11 from the SMF; And

sending an acknowledgment of the N2 path switch request to the T-RAN.

Although the present invention has been described with reference to its specific features and embodiments, it is obvious that various modifications and combinations can be made to it without departing from the invention. The description and drawings, respectively, are to be regarded simply as illustrating the invention as defined in the appended claims and are intended to cover any and all modifications, variations, combinations or equivalents that are within the scope of the present invention.

Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as generally understood by those skilled in the art to which this invention pertains.

Through the descriptions of the foregoing embodiments, the present invention may be implemented using hardware alone, or using software and the necessary universal hardware platform. Based on this understanding, the technical solution of the present invention can be implemented in the form of a software product. The Software Product may be stored on a non-volatile or persistent storage medium, which may be a read-only compact disk (CD-ROM), a USB flash drive, or a removable hard drive. The software product includes a set of instructions that enable a computing device (personal computer, server, or network device) to perform the methods provided in the embodiments of the present invention. For example, such an execution may correspond to the modeling of logical operations, as described here. The software product may additionally or alternatively include a set of instructions that enable the computing device to perform operations to configure or program the digital logic device in accordance with embodiments of the present invention.

Claims (28)

1. A method for managing a communication network session, comprising: receiving a session management function, SMF, a trigger for releasing a session packet data unit, PDU; sending by SMF to the user plane function, UPF, a session release request that includes at least one of the user device identifier, UE, the identifier of the session PDU to be released, and the session ID N4 to request the UPF to discard all remaining session PDU packets and release a UE context in UPF, or all tunnel resources and contexts associated with an N4 session in UPF; And receiving by the SMF from the UPF a session release response. 2. The method of claim 1, wherein the session release response is for confirming the session release request. 3. The method of claim 1 or 2, wherein the trigger to release the session PDU is received when the UE is in a CM connection control state, including one of: a CM-CONNECTED state or a CM-IDLE state. 4. The method according to any one of claims 1-3, wherein when the session PDU is associated with a plurality of UPFs, sending by the SMF to the UPF a session release request comprises: sending by the SMF a session release request to each of the plurality of UPFs, and receiving by the SMF from the UPF a session release response comprises: receiving by the SMF from each of the plurality of UPFs a session release response. 5. The method according to any one of claims 1-4, wherein the PDU session release is initiated by the SMF, the method further comprising: if the UE associated with the session PDU is not available, notification by the SMF of the access and mobility control function AMF that the session PDU has been released. 6. The method of claim 5, wherein the SMF notifies the AMF that the session PDU is being released by invoking an operation including a session PDU identifier and a session PDU indication. 7. The method according to claim 5 or 6, in which the method further comprises: deleting by the SMF the context associated with the session PDU in which communication associated with resource release between the AMF and the UE is skipped. 8. A method according to any one of claims 1 to 4, wherein the method further comprises: sending by the SMF to the access and mobility control function, an AMF request including an N1 SM message in which the N1 SM message includes a session PDU release command, and a skip indication instructing the AMF to skip sending the N1 SM message to the UE if the UE is in the state CMIDLE; And receiving by the SMF from the AMF a response indicating that the N1 SM message is not being transmitted to the UE. 9. The method of claim 8, wherein the response includes a result indication indicating that the N1 SM message was not transmitted to the UE with a cause. 10. A communication network session manager comprising a processor and a memory, the processor being configured to perform the method of any one of claims 1-9. 11. A method for managing a communication network session, comprising: receiving by the user plane function, UPF, from the session management function, SMF, a session release request including at least one of a user device identifier, UE, a session identifier of a packet data unit, a PDU to be released, and a session ID N4; UPF discarding any remaining session PDUs and releasing the UE context in the UPF, or all tunnel resources and contexts associated with the N4 session in the UPF; And sending a session release response via UPF to the SMF. 12. The method of claim 11, wherein the session release response is for confirming the session release request. 13. A network session manager comprising a processor and a memory, the processor being configured to perform the method of any one of claims 11-12. 14. A communication network session management system, comprising a communication network session management device according to claim 10 and a communication network session management device according to claim 13. 15. A non-volatile computer-readable medium storing instructions which, when executed by one or more processors, causes the one or more processors to perform the method of any one of claims 1-9. 16. A non-volatile computer-readable medium storing instructions which, when executed by one or more processors, causes the one or more processors to perform the method of any one of claims 11-12.

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