WO2021089739A1 - Establishing pdu session without user plane resources - Google Patents

Abstract

Disclosed herein is a method of operating a communication device, comprising: generating (402) a packet data session establishment request for establishing a packet data session and an indication that user plane resources are not expected, required or requested for the packet data session and/or an indication that the communication device supports packet data session initiation without user plane resources; and transmitting (404) the packet data session establishment request and the indication towards a core network node in a communication network.

Description

ESTABLISHING PDU SESSION WITHOUT USER PLANE RESOURCES

[0001] The present disclosure relates generally to communications, and more particularly, to wireless communications and related wireless devices and network nodes. BACKGROUND Figure 1

[0002] A simplified wireless communication system is illustrated in Figure 1. The system includes a UE 100 that communicates with one or more access nodes 210, 220 using radio connections 107, 108. The access nodes 210, 220 are connected to a core network node 106. The access nodes 210-220 are part of a radio access network 105.

[0003] For wireless communication systems pursuant to 3GPP Evolved Packet System, EPS (also referred to as Long Term Evolution, LTE, or 4G) standard specifications, such as specified in 3GPP TS 36.300 and related specifications, the access nodes 210, 220 correspond typically to an Evolved NodeB (eNB) and the core network node 106 corresponds typically to either a Mobility Management Entity (MME) and/or a Serving Gateway (SGW). The eNB is part of the radio access network 105, which in this case is the E-UTRAN (Evolved Universal Terrestrial Radio Access Network), while the MME and SGW are both part of the EPC (Evolved Packet Core network).

[0004] For wireless communication systems pursuant to 3GPP 5G System, 5GS (also referred to as New Radio, NR, or 5G) standard specifications, such as specified in 3GPP TS 38.300 and related specifications, the access nodes 103-104 correspond typically to a 5G NodeB (gNB) and the network node 106 corresponds typically to either an Access and Mobility Management Function (AMF) and/or a User Plane Function (UPF). The gNB is part of the radio access network 100, which in this case is the NG-RAN (Next Generation Radio Access Network), while the AMF and UPF are both part of the 5G Core Network (5GC). [0005] The 5G System consists of the access network and the core network. The Access Network (AN) is the network that allows the UE to gain connectivity to the Core Network (CN), e.g. the base station which could be a gNB or an ng-eNB in 5G. The CN contains all the Network Functions (NF) ensuring a wide range of different functionalities such as session management, connection management, charging, authentication, etc. Figure 2

[0006] Figure 2, which is reproduced from TS 23.501 v16.2.0 gives a high overview of the 5G architecture for the non-roaming scenario.

[0007] The communication links between the UE and the network (AN and CN) are partitioned into two strata. The UE communicates with the CN over the Non-Access Stratum (NAS), and with the AN over the Access Stratum (AS). All the NAS communication takes place between the UE and the Access and connectivity Management Function (AMF) in the CN over the NAS protocol (N1 interface in Figure 2). Communications within the network can be classified as user plane or control plane communications.

The user plane carries user data traffic for a device (e.g. UE), e.g. such as voice or video or application data and similar. The control plane carries signaling traffic that is used to establish and maintain the user plane connection.

[0008] In the current 5GS specification 3GPP TS 23.502 v16.2.0, a user plane will be established between the UE and UPF via ngRAN when the UE requests the establishment of a new packet data session, such as a protocol data unit, PDU, session. [0009] Flowever, in 5GS, a PDU session could be without a user plane even though the UE is in CM-

CONNECTED state, e.g. when the UE transitions from CM-IDLE to CM-CONNECTED via the service request procedure but only requests user plane resources for a subset of its established PDU sessions. This is different from the evolved packet system (EPS) where all packet data network (PDN) connections always have user plane resources established when the UE is in EMM-CONNECTED state. [0010] It was agreed in SA2 CR 1868 in S2-1910498 the AMF shall enforce the requirement that over

NB-loT access, the UE shall at any time have more than two PDU sessions with active user planes. If the UE attempts to establish a new PDU session when there are already two PDU sessions with user planes, the AMF shall prevent such attempt. The NAS PDU session establishment request is piggybacked in a NAS mobility management (MM) message, namely, the uplink (UL) NAS transport message. For this scenario, rejecting the attempt with the current specifications, the AMF shall send back a downlink (DL) NAS transport message piggybacking the PDU session establishment request along with a cause code. The MM layer in the UE will provide this information to the session management (SM) layer in the UE.

SUMMARY

[0011] Assume that the UE requests connectivity to a new data network (DN) over NB-loT access but is rejected due the maximum two PDU sessions with user plane restriction. A short time later when the UE e.g. transitions to CM-IDLE and the restriction is removed (as all user planes will be released), the UE can get connectivity to the new DN by performing the service request procedure and at success, perform the PDU session establishment procedure. However, this is not signaling efficient. Instead, if the UE in the first place could establish the PDU session without the user plane established, a service request requesting the user plane for this PDU session will be enough to finally get connectivity to the DN.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The accompanying drawings, which are included to provide a further understanding of the disclosure and are incorporated in a constitute a part of this application, illustrate certain non-limiting embodiments of inventive concepts. In the drawings:

Figure 1 illustrates a wireless communication system.

Figure 2 illustrates a non-roaming reference architecture of a wireless communication system.

Figure 3 illustrates a PDU session establishment procedure.

Figure 4 is a flowchart that illustrates operations of a communication device according to some embodiments.

Figure 5 is a flowchart that illustrates operations of a core network node according to some embodiments.

Figure 6 is a block diagram illustrating an example of a communication device according to some embodiments.

Figure 7 is a block diagram illustrating an example of a core network (CN) node according to some embodiments.

DETAILED DESCRIPTION

[0013] Inventive concepts will now be described more fully hereinafter with reference to the accompanying drawings, in which examples of embodiments of inventive concepts are shown. Inventive concepts may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of present inventive concepts to those skilled in the art. It should also be noted that these embodiments are not mutually exclusive. Components from one embodiment may be tacitly assumed to be present/used in another embodiment. [0014] The following description presents various embodiments of the disclosed subject matter. These embodiments are presented as teaching examples and are not to be construed as limiting the scope of the disclosed subject matter. For example, certain details of the described embodiments may be modified, omitted, or expanded upon without departing from the scope of the described subject matter.

[0015] As noted above, a UE will be blocked from establishing a new PDU session when it already has two PDU sessions with user planes. In an example scenario, a UE that requests connectivity to a new data network (DN) over NB-loT access could be rejected due the restriction of having a maximum of two PDU sessions with user planes. A short time later when the UE e.g. transitions to CM-IDLE and the restriction is removed (as all user planes will be released), the UE can get connectivity to the new DN by performing a service request procedure and at success, perform the PDU session establishment procedure. However, this is not signaling efficient. Instead, if the UE could establish the PDU session without the user plane established, a service request requesting the user plane for this PDU session would be enough to establish connectivity to the DN.

[0016] Some embodiments described herein enable PDU session establishment without the establishment of user plane resources between a UE and the UPF via a gNB regardless of 3GPP access (NR, WB-loT, NB-loT). In various embodiments, the UE, AMF and/or SMF may decide whether user plane resources should be requested or established for a PDU session. Some embodiments may reduce signaling between core network functions such as AMF and SMF, and/or provide more flexibility for UEs to establish PDU sessions.

[0017] When the AMF decides, for example, based on NB-loT access restrictions or an operator- specific policy, to not request the establishment of user plane resources for a PDU session, the AMF may explicitly indicate to the SMF over the N11 interface in a SmContextCreateData message or SmContextUpdateData message that the SMF shall not initiate the establishment of the user plane for the new PDU session. In that case, the SMF may perform normal PDU session establishment activities except for setting up an N3 tunnel end-point and may not include the N2 SM Information IE in the SMContextCreatedData or SmContextUpdatedData message over N11.

[0018] In some embodiments, a UE may indicate to the AMF that the UE does not want to have a user plane resources established for a requested PDU session. The UE may indicate this in an UL NAS transport message piggybacking a NAS PDU session establishment request message.

[0019] A UE may indicate its support for this feature to the network with, for example, a new flag in the “5GMM capability” IE of the Registration Request message. [0020] In some embodiments, an SMF could decide on its own, without the indication from the UE, that user plane resources should not be established for a PDU session. This decision may be made, for example, based on an operator-specific policy or other information. Following such a decision, the SMF would not include the N2 SM Information IE in the SMContextCreatedData message or SMContextUpdatedData message over N11.

Figure 3

[0021] A procedure for UE-requested PDU session establishment that is reproduced from 3GPP TS 23.502 is shown in Figure 3. As shown therein, a PDU session establishment procedure may begin when a UE transmits a PDU session establishment request (1) toward an AMF in a 5G core network. The UE transmits the PDU session establishment request (1) to a RAN node, such as a gNodeB. In some embodiments, the PDU session establishment request may include an indication that user plane resources are not expected, required or requested for the PDU session that is being established.

[0022] In response to the PDU establishment request, the AMF may follow conventional procedures for PDU session establishment, except that the AMF may explicitly indicate to the SMF over the N11 interface in a SmContextCreateData message or SMContextUpdateData message (e.g., a

Nsmf_PDUSession_CreateSMContext Request or Nsfm_PDUSession_UpdateSMContext Request) that the SMF should not initiate the establishment of the user plane for the new PDU session.

[0023] For example, in response to a “NAS only flag” in the PDU session establishment request that indicates that user plane resources are not expected/requested/required or based on a local policy or other information (e.g. maximum allowed active user plane for a UE is reached), the AMF may decide to not setup user plane for the PDU session. In that case, the AMF may include a “NAS only flag” in the Nsmf_PDUSession_CreateSMContext Request or Nsfm_PDUSession_UpdateSMContext Request (3) to the SMF.

[0024] In response, the SMF may not include the N2 SM Information IE in the SMContextCreatedData message (5) or SMContextUpdatedData message over N11. For example, If the SMF has received a “NAS only flag” from the AMF indicating that user plane resources are not expected/required/requested for the PDU session, or the SMF decides to not set up a user plane for the PDU session due, for example, to a local policy (e.g. UE is in a restricted area for data service), the N2 SM information shall not be provided by the SMF. If SMF does not provide N2 SM information to the AMF and only an N1 SM container is provided, the AMF shall send DL NAS including the N1 SM container. [0025] An example proposed modification to 3GPP TS 23.502 is attached as Appendix A with changes highlighted.

Figure 4

[0026] Operations of a communication device according to some embodiments are illustrated in Figure 4. Referring to Figure 4, a method of operating a communication device includes generating (402) a packet data session establishment request for establishing a packet data session and an indication that user plane resources are not expected, required or requested for the packet data session and/or an indication that the communication device supports packet data session initiation without user plane resources, and transmitting (404) the packet data session establishment request and the indication towards a core network node in a communication network. An example of a packet data session establishment request may include, for example, a PDU session establishment request.

[0027] The core network node may include an access and mobility function, AMF, in a 5G core network. [0028] Transmitting the packet data session establishment request towards the core network node may include transmitting the packet data session establishment request to a radio access node in a radio access network.

[0029] The indication may be transmitted in a non-access stratum, NAS, transport message. The packet data session establishment request may include a PDU session establishment request that is carried in the NAS transport message. The indication may include a flag in the NAS transport message. [0030] The flag may indicate that no user plane setup is expected, required or requested for this packet data session establishment and/or that the communication device supports packet data session without user plane resources. The flag may include a NAS only flag.

[0031] The method may further include receiving, in response to the packet data session establishment request, an indication that the packet data session has been established without user plane resources. [0032] The user plane may carry user data traffic between the communication device and the communication network.

Figure 5

[0033] Operations of a core network function according to some embodiments are illustrated in Figure 5. Referring to Figure 5, a method of operating a core network function in a core network according to some embodiments includes receiving (502) a packet data session establishment request from a communication device, and establishing (504) the packet data session without user plane resources.

[0034] The core network node may include an access and mobility function, AMF, in a 5G core network. The method may further include, in response to the packet data session establishment request, transmitting a session context creation message or session context update message to a session management function, SMF, of the core network, wherein the session context creation message indicates that the SMF may be not to establish a user plane for the packet data session.

[0035] The session context creation message may include a SmContextCreateData message or a SmContextUpdateData message. The SMContextCreateData message or SmContextUpdateData message may omit an SMInformation information element.

[0036] The core network node may receive an indication that user plane resources are not requested, expected or required for the packet data session. The indication may be carried in a non-access stratum, NAS, transport message. The NAS protocol data unit, PDU, session establishment message may be carried in the NAS transport message. [0037] The indication may include a flag in the NAS transport message transmitted by the communication device. The flag may indicate that no user plane setup is expected, requested or required for this packet data session establishment. The flag may include a NAS only flag.

[0038] The method may further include, following establishment of the packet data session, transmitting an indication that the packet data session has been established without user plane resources. [0039] The method may further include determining, in response to the packet data session establishment request, that user plane resources are not to be established for the packet data session. Determining that user plane resources are not to be established for the packet data session may be performed based on a configuration setting.

[0040] Various embodiments provide a communication device 100 that includes a processor circuit, a transceiver coupled to the processor circuit, and a memory coupled to the processor circuit. The memory includes machine-readable computer program instructions that, when executed by the processor circuit, cause the processor circuit to perform some of the operations depicted in Figure 4.

Figure 6

[0041] Figure 6 depicts an example of a communication device 100 of a wireless communication network configured to provide wireless communication according to embodiments of inventive concepts. As shown, the communication device 100 may include a transceiver circuit 112 (also referred to as a transceiver) including a transmitter and a receiver configured to provide uplink and downlink radio communications with wireless devices. The communication device 100 may also include a processor circuit 116 (also referred to as a processor) coupled to the transceiver circuit 112, and a memory circuit 118 (also referred to as memory) coupled to the processor circuit 116. The memory circuit 118 may include computer readable program code that when executed by the processor circuit 116 causes the processor circuit to perform operations according to embodiments disclosed herein. According to other embodiments, processor circuit 116 may be defined to include memory so that a separate memory circuit is not required.

[0042] As discussed herein, operations of the communication device 100 may be performed by processor 116 and/or transceiver 112. For example, the processor 116 may control transceiver 112 to transmit uplink communications through transceiver 112 over a radio interface to one or more network nodes and/or to receive downlink communications through transceiver 112 from one or more network nodes over a radio interface. Moreover, modules may be stored in memory 118, and these modules may provide instructions so that when instructions of a module are executed by processor 116, processor 116 performs respective operations (e.g., operations discussed above with respect to example embodiments).

[0043] Accordingly, a communication device 100 according to some embodiments includes a processor circuit 116, a transceiver 112 coupled to the processor circuit, and a memory 118 coupled to the processor circuit, the memory including machine readable program instructions that, when executed by the processor circuit, cause the UE to perform operations described above.

[0044] Accordingly, referring to Figures 4 and 6, a communication device (100) according to some embodiments includes a processor circuit (116), a transceiver (112) coupled to the processor circuit, and a memory (118) coupled to the processor circuit. The memory includes computer readable program instructions that, when executed by the processor, cause the communication device to perform operations of generating (402) a packet data session establishment request for establishing a packet data session and an indication that user plane resources are not requested for the packet data session, and transmitting (404) the packet data session establishment request and the indication towards a core network node.

[0045] A communication device (100) according to some embodiments is configured to generate (402) a packet data session establishment request for establishing a packet data session and an indication that user plane resources are not requested for the packet data session, and transmit (404) the packet data session establishment and the indication request towards a core network node. Figure 7

[0046] Figure 7 is a block diagram of a network node according to some embodiments. Various embodiments provide a core network node that includes a processor circuit 206 and a memory 208 coupled to the processor circuit. The memory 208 includes machine-readable computer program instructions that, when executed by the processor circuit, cause the processor circuit to perform some of the operations depicted in Figure 5.

[0047] Figure 7 depicts an example of a core network node 200 of a wireless communication network configured to provide cellular communication according to embodiments of inventive concepts. The network node 200 may include a network interface circuit 204 (also referred to as a network interface) configured to provide communications with other nodes (e.g., with other base stations and/or core network nodes) of the wireless communication network. The memory circuit 208 may include computer readable program code that when executed by the processor circuit 206 causes the processor circuit to perform operations according to embodiments disclosed herein. According to other embodiments, processor circuit 206 may be defined to include memory so that a separate memory circuit is not required.

[0048] As discussed herein, operations of the network node 200 may be performed by processor 206 and/or network interface 204. For example, processor 206 may control network interface 204 to transmit communications through network interface 204 to one or more other network nodes and/or to receive communications through network interface from one or more other network nodes. Moreover, modules may be stored in memory 208, and these modules may provide instructions so that when instructions of a module are executed by processor 206, processor 206 performs respective operations. In addition, a structure similar to that of Figure 7 may be used to implement other network nodes. Moreover, network nodes discussed herein may be implemented as virtual network nodes.

[0049] Accordingly, a core network node (200) according to some embodiments includes a processor circuit (206), a network interface (204), and a memory (208) coupled to the processor circuit. The memory may include computer readable program instructions that, when executed by the processor, cause the communication device to perform operations of receiving (502) a packet data session establishment request from a communication device, and establishing (504) the packet data session without user plane resources. [0050] A core network node (200) according to some embodiments may be configured to receive (502) a packet data session establishment request from a communication device, and establish (504) the packet data session without user plane resources.

EXAMPLE EMBODIMENTS

[0051] Some example embodiments discussed above are summarized below. Reference numbers/letters are provided in parenthesis by way of example/illustration without limiting example embodiments to particular elements indicated by reference numbers/letters.

Embodiment 1. A method of operating a communication device, comprising: generating (402) a packet data session establishment request for establishing a packet data session and an indication that user plane resources are not expected, required or requested for the packet data session and/or an indication that the communication device supports packet data session initiation without user plane resources; and transmitting (404) the packet data session establishment request and the indication towards a core network node in a communication network.

Embodiment 2. The method of Embodiment 1, wherein the core network node comprises an access and mobility function, AMF, in a 5G core network.

Embodiment 3. The method of Embodiment 1 or 2, wherein transmitting the packet data session establishment request towards the core network node comprises transmitting the packet data session establishment request to a radio access node in a radio access network.

Embodiment 4. The method of any previous Embodiment, wherein the indication is transmitted in a non-access stratum, NAS, transport message.

Embodiment 5. The method of Embodiment 4, wherein the packet data session establishment request comprises a protocol data unit, PDU, session establishment message that is carried in the NAS transport message. Embodiment 6. The method of Embodiment 4 or 5, wherein the indication comprises a flag in the NAS transport message.

Embodiment 7. The method of Embodiment 6, wherein the flag indicates that no user plane setup is expected, required or requested for this packet data session establishment and/or that the communication device supports packet data session without user plane resources.

Embodiment 8. The method of Embodiment 7, wherein the flag comprises a NAS only flag.

Embodiment 9. The method of any previous Embodiment, further comprising: receiving, in response to the packet data session establishment request, an indication that the packet data session has been established without user plane resources.

Embodiment 10.The method of any previous Embodiment, wherein the user plane carries user data traffic between the communication device and the communication network.

Embodiment 11.A communication device (100), comprising: a processor circuit (116); a transceiver (112) coupled to the processor circuit; and a memory (118) coupled to the processor circuit, wherein the memory comprises computer readable program instructions that, when executed by the processor, cause the communication device to perform operations of: generating (402) a packet data session establishment request for establishing a packet data session and an indication that user plane resources are not requested for the packet data session; and transmitting (404) the packet data session establishment request and the indication towards a core network node.

Embodiment 12.The communication device of Embodiment 10, further configured to perform operations according to any of Embodiments 1 to 10. Embodiment 13. A communication device (100) configured to: generate (402) a packet data session establishment request for establishing a packet data session and an indication that user plane resources are not requested for the packet data session; and transmit (404) the packet data session establishment request and the indication towards a core network node.

Embodiment 14. A method of operating a core network function in a core network, comprising: receiving (502) a packet data session establishment request from a communication device for establishing a packet data session; and establishing (504) the packet data session without user plane resources.

Embodiment 15.The method of Embodiment 14, wherein the core network node comprises an access and mobility function, AMF, in a 5G core network.

Embodiment 16.The method of any of Embodiments 14 to 15, further comprising: in response to the packet data session establishment request, transmitting a session context creation message or a session context update message to a session management function, SMF, of the core network, wherein the session context creation message or session context update message indicates that the SMF is not to establish a user plane for the packet data session.

Embodiment 17.The method of Embodiment 16, wherein the session context creation message comprises a SmContextCreateData message or a SmContextUpdateData message.

Embodiment 18.The method of Embodiment 17, wherein the SMContextCreateData message or SmContextUpdateData message omits an SMInformation information element.

Embodiment 19.The method of any of Embodiments 14 to 18, wherein the packet data session establishment request includes an indication that user plane resources are not requested, expected or required for the packet data session. Embodiment 20.The method of Embodiment 19, wherein indication is carried in a non-access stratum, NAS, transport message.

Embodiment 21.The method of Embodiment 20, wherein packet data session establishment request is carried in the NAS transport message.

Embodiment 22.The method of Embodiment 20, wherein the indication comprises a flag in the NAS transport message.

Embodiment 23.The method of Embodiment 22, wherein the flag indicates that no user plane setup is expected, requested or required for this packet data session establishment.

Embodiment 24.The method of Embodiment 22, wherein the flag comprises a NAS only flag.

Embodiment 25.The method of any of Embodiments, 14 to 24, further comprising: following establishment of the packet data session, transmitting an indication that the packet data session has been established without user plane resources.

Embodiment 26.The method of any of Embodiments 14 to 18, further comprising: determining, in response to the packet data session establishment request, that user plane resources are not to be established for the packet data session.

Embodiment 27.The method of Embodiment 26, wherein determining that user plane resources are not to be established for the packet data session is performed based on a configuration setting.

Embodiment 28. A core network node (200), comprising: a processor circuit (206); a network interface (204); and a memory (208) coupled to the processor circuit, wherein the memory comprises computer readable program instructions that, when executed by the processor, cause the communication device to perform operations of:

IB receiving (502) a packet data session establishment request from a communication device for establishing a packet data session; and establishing (504) the packet data session without user plane resources.

Embodiment 29.The core network node of Embodiment 27, further configured to perform operations according to any of Embodiments 14 to 27.

Embodiment 30. A core network node (200) configured to: receive (502) a packet data session establishment request from a communication device for establishing a packet data session; and establish (504) the packet data session without user plane resources.

[0052] Explanations for abbreviations from the above disclosure are provided below.

Abbreviation Explanation

3GPP 3rd Generation Partnership Project

5G 5th Generation

AAA Authentication, Authorization and Accounting

AF Application Function

AMF Access and Mobility Management Function

AN Access Network

ARPF Authentication credential Repository and Processing Function

AS Access Stratum

CN Core Network

DN Data Network eNB Evolved NodeB (a radio base station in LTE) gNB A radio base station in NR.

IETF Internet Engineering Task Force

LTE Long Term Evolution

ME Mobile Equipment

NAS Non-Access Stratum

NF Network Function

NRF NF Repository Function

NEF Network Exposure Function

NSSF Network Slice Selection Function

NPN Non-Public Network

NR New Radio

PCF Policy Control Function PLMN Public Land Mobile Network

RAN Radio Access Network

RFC Request for Comments

SBA Service Based Architecture

SMF Session Management Function

UPF User Plane Function

UE User Equipment

X2 Interface/reference point between two eNBs.

Xn Interface/reference point between two gNBs.

UL Uplink

DL Downlink

[0053] In the above-description of various embodiments of present inventive concepts, it is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of present inventive concepts. Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which present inventive concepts belong. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of this specification and the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

[0054] As used herein, a "communication device" may be any device intended for accessing services via an access network and configured to communicate over the access network. For instance, the communication device may be, but is not limited to: a user equipment (UE), mobile phone, smart phone, sensor device, meter, vehicle, household appliance, medical appliance, media player, camera, or any type of consumer electronic, for instance, but not limited to, television, radio, lighting arrangement, tablet computer, laptop, or PC. The communication device may be a portable, pocketstorable, hand-held, computer-comprised, or vehicle-mounted mobile device, enabled to communicate voice and/or data, via a wireless or wireline connection.

[0055] When an element is referred to as being "connected", "coupled", "responsive", or variants thereof to another element, it can be directly connected, coupled, or responsive to the other element or intervening elements may be present. In contrast, when an element is referred to as being "directly connected", "directly coupled", "directly responsive", or variants thereof to another element, there are no intervening elements present. Like numbers refer to like elements throughout. Furthermore, "coupled", "connected", "responsive", or variants thereof as used herein may include wirelessly coupled, connected, or responsive. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. Well-known functions or constructions may not be described in detail for brevity and/or clarity. The term "and/or" includes any and all combinations of one or more of the associated listed items.

[0056] It will be understood that although the terms first, second, third, etc. may be used herein to describe various elements/operations, these elements/operations should not be limited by these terms. These terms are only used to distinguish one element/operation from another element/operation. Thus, a first element/operation in some embodiments could be termed a second element/operation in other embodiments without departing from the teachings of present inventive concepts. The same reference numerals or the same reference designators denote the same or similar elements throughout the specification.

[0057] As used herein, the terms "comprise", "comprising", "comprises", "include", "including", "includes", "have", "has", "having", or variants thereof are open-ended, and include one or more stated features, integers, elements, steps, components, or functions but does not preclude the presence or addition of one or more other features, integers, elements, steps, components, functions, or groups thereof. Furthermore, as used herein, the common abbreviation "e.g.", which derives from the Latin phrase "exempli gratia," may be used to introduce or specify a general example or examples of a previously mentioned item, and is not intended to be limiting of such item. The common abbreviation "i.e.", which derives from the Latin phrase "id est," may be used to specify a particular item from a more general recitation. [0058] Example embodiments are described herein with reference to block diagrams and/or flowchart illustrations of computer-implemented methods, apparatus (systems and/or devices) and/or computer program products. It is understood that a block of the block diagrams and/or flowchart illustrations, and combinations of blocks in the block diagrams and/or flowchart illustrations, can be implemented by computer program instructions that are performed by one or more computer circuits. These computer program instructions may be provided to a processor circuit of a general purpose computer circuit, special purpose computer circuit, and/or other programmable data processing circuit to produce a machine, such that the instructions, which execute via the processor of the computer and/or other programmable data processing apparatus, transform and control transistors, values stored in memory locations, and other hardware components within such circuitry to implement the functions/acts specified in the block diagrams and/or flowchart block or blocks, and thereby create means (functionality) and/or structure for implementing the functions/acts specified in the block diagrams and/or flowchart block(s).

[0059] These computer program instructions may also be stored in a tangible computer- readable medium that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable medium produce an article of manufacture including instructions which implement the functions/acts specified in the block diagrams and/or flowchart block or blocks. Accordingly, embodiments of present inventive concepts may be embodied in hardware and/or in software (including firmware, resident software, micro-code, etc.) that runs on a processor such as a digital signal processor, which may collectively be referred to as "circuitry," "a module" or variants thereof.

[0060] It should also be noted that in some alternate implementations, the functions/acts noted in the blocks may occur out of the order noted in the flowcharts. For example, two blocks shown in succession may in fact be executed substantially concurrently or the blocks may sometimes be executed in the reverse order, depending upon the functionality/acts involved. Moreover, the functionality of a given block of the flowcharts and/or block diagrams may be separated into multiple blocks and/or the functionality of two or more blocks of the flowcharts and/or block diagrams may be at least partially integrated. Finally, other blocks may be added/inserted between the blocks that are illustrated, and/or blocks/operations may be omitted without departing from the scope of inventive concepts. Moreover, although some of the diagrams include arrows on communication paths to show a primary direction of communication, it is to be understood that communication may occur in the opposite direction to the depicted arrows.

[0061] Many variations and modifications can be made to the embodiments without substantially departing from the principles of the present inventive concepts. All such variations and modifications are intended to be included herein within the scope of present inventive concepts. Accordingly, the above disclosed subject matter is to be considered illustrative, and not restrictive, and the examples of embodiments are intended to cover all such modifications, enhancements, and other embodiments, which fall within the spirit and scope of present inventive concepts. Thus, to the maximum extent allowed by law, the scope of present inventive concepts are to be determined by the broadest permissible interpretation of the present disclosure including the examples of embodiments and their equivalents, and shall not be restricted or limited by the foregoing detailed description.

[0062] Generally, all terms used herein are to be interpreted according to their ordinary meaning in the relevant technical field, unless a different meaning is clearly given and/or is implied from the context in which it is used. All references to a/an/the element, apparatus, component, means, step, etc. are to be interpreted openly as referring to at least one instance of the element, apparatus, component, means, step, etc., unless explicitly stated otherwise. The steps of any methods disclosed herein do not have to be performed in the exact order disclosed, unless a step is explicitly described as following or preceding another step and/or where it is implicit that a step must follow or precede another step. Any feature of any of the embodiments disclosed herein may be applied to any other embodiment, wherever appropriate. Likewise, any advantage of any of the embodiments may apply to any other embodiments, and vice versa. Other objectives, features and advantages of the enclosed embodiments will be apparent from the following description. Appendix A - Example Modification to 3GPP TS 23.502

4.3.2.2.1 Non-roaming and Roaming with Local Breakout

Clause 4.3.2.2.1 specifies PDU Session establishment in the non-roaming and roaming with local breakout cases. The procedure is used to:

- Establish a new PDU Session;

- Handover a PDN Connection in EPS to PDU Session in 5GS without N26 interface;

- Switching an existing PDU Session between non-3GPP access and 3 GPP access. The specific system behaviour in this case is further defined in clause 4.9.2; or - Request a PDU Session for Emergency services.

In case of roaming, the AMF determines if a PDU Session is to be established in LBO or Home Routing. In the case of LBO, the procedure is as in the case of non-roaming with the difference that the AMF, the SMF, the UPF and the PCF are located in the visited network. PDU Sessions for Emergency services are never established in Home Routed mode. In the case of LBO, the NEF is not used.

NOTE 1 : UE provides both the S-NSSAIs of the Home PLMN and Visited PLMN to the network as described in clause 5.15.5.3 of TS 23.501 [2]

Figure 4.3.2.2.1-1: UE-requested PDU Session Establishment for non-roaming and roaming with local breakout

The procedure assumes that the UE has already registered on the AMF thus unless the UE is Emergency Registered the AMF has already retrieved the user subscription data from the UDM.

1. From UE to AMF: NAS Message (S-NSSAI(s), UE Requested DNN, PDU Session ID, Request type, Old PDU Session ID, N1 SM container (PDU Session Establishment Request), NAS only flag).

In order to establish a new PDU Session, the UE generates a new PDU Session ID.

The UE initiates the UE Requested PDU Session Establishment procedure by the transmission of a NAS message containing a PDU Session Establishment Request within the N1 SM container. The PDU Session Establishment Request includes a PDU session ID, Requested PDU Session Type, a Requested SSC mode, 5GSM Capability, PCO, SM PDU DN Request Container, [Number Of Packet Filters], [Header Compression Configuration], UE Integrity Protection Maximum Data Rate, and [Always-on PDU Session Requested].

The Request Type indicates "Initial request" if the PDU Session Establishment is a request to establish a new PDU Session and indicates "Existing PDU Session" if the request refers to an existing PDU Session switching between 3GPP access and non-3GPP access or to a PDU Session handover from an existing PDN connection in EPC. If the request refers to an existing PDN connection in EPC, the S-NSSAI is set as described in TS 23.501 [2] clause 5.15.7.2

When Emergency service is required and an Emergency PDU Session is not already established, a UE shall initiate the UE Requested PDU Session Establishment procedure with a Request Type indicating "Emergency Request".

The Request Type indicates "Emergency Request" if the PDU Session Establishment is a request to establish a PDU Session for Emergency services. The Request Type indicates "Existing Emergency PDU Session" if the request refers to an existing PDU Session for Emergency services switching between 3 GPP access and non-3GPP access or to a PDU Session handover from an existing PDN connection for Emergency services in EPC.

The 5GSM Core Network Capability is provided by the UE and handled by SMF as defined in TS 23.501 [2] clause 5.4.4b.

The Number Of Packet Filters indicates the number of supported packet filters for signalled QoS rules for the PDU Session that is being established. The number of packet filters indicated by the UE is valid for the lifetime of the PDU Session. For presence condition, see TS 24.501 [25]

The UE Integrity Protection Maximum Data Rate indicates the maximum data rate up to which the UE can support UP integrity protection. The UE shall provide the UE Integrity Protection Data Rate capability independently of the Access Type over which the UE sends the PDU Session Establishment Request.

If the use of header compression for Control Plane CIoT 5GS optimisation was negotiated successfully between the UE and the network in the previous registration procedure, the UE shall include the Header Compression Configuration, unless "Unstructured" or "Ethernet" PDU Session Type is indicated.

The NAS message sent by the UE is encapsulated by the AN in a N2 message towards the AMF that should include User location information and Access Type Information.

The PDU Session Establishment Request message may contain SM PDU DN Request Container containing information for the PDU Session authorization by the external DN.

The UE includes the S-NSSAI from the Allowed NSSAI of the current access type. If the Mapping of Allowed NSSAI was provided to the UE, the UE shall provide both the S-NSSAI of the VPLMN from the Allowed NSSAI and the corresponding S-NSSAI of the HPLMN from the Mapping Of Allowed NSSAI. If the procedure is triggered for SSC mode 3 operation, the UE shall also include the Old PDU Session ID which indicates the PDU Session ID of the on-going PDU Session to be released, in NAS message. The Old PDU Session ID is included only in this case.

The AMF receives from the AN the NAS SM message (built in step 1) together with User Location Information (e.g. Cell Id in case of the NG-RAN).

The UE shall not trigger a PDU Session establishment for a PDU Session corresponding to a LADN when the UE is outside the area of availability of the LADN.

If the UE is establishing a PDU session for IMS, and the UE is configured to discover the P-CSCF address during connectivity establishment, the UE shall include an indicator that it requests a P-CSCF IP address(es) within the SM container.

The PS Data Off status is included in the PCO in the PDU Session Establishment Request message.

The UE capability to support Reliable Data Service is included in the PCO in the PDU Session Establishment Request message.

If the UE has indicated that it supports transfer of Port Management Information Containers as per UE 5 GSM Core Network Capability, then the UE shall include the MAC address of the DS-TT Ethernet port used for this PDU session. If the UE is aware of the UE-DS-TT Residence Time, then the UE shall additionally include the UE-DS-TT Residence Time.

If the UE requests to establish always-on PDU session, the UE includes an Always-on PDU Session Requested indication in the PDU Session Establishment Request message.

The UE may include a “NAS only flag” to indicate that no user plane setup is expected for this PDU session establishment. The AMF determines that the message corresponds to a request for a new PDU Session based on that Request Type indicates "initial request" and that the PDU Session ID is not used for any existing PDU Session(s) of the UE. If the NAS message does not contain an S-NSSAI, the AMF determines a default S- NSSAI of the HPLMN for the requested PDU Session either according to the UE subscription, if it contains only one default S -NS S AI, or based on operator policy and, in the case of LBO, an S -NS S AI of the Serving PLMN which matches the S-NSSAI of the HPLMN. When the NAS Message contains an S-NSSAI of the Serving PLMN but it does not contain a DNN, the AMF determines the DNN for the requested PDU Session by selecting the default DNN for this S-NSSAI if the default DNN is present in the UE's Subscription Information (or for the corresponding S-NSSAI of the HPLMN, in the case of LBO); otherwise the serving AMF selects a locally configured DNN for this S-NSSAI of the Serving PLMN. If the AMF cannot select an SMF (e.g. the UE requested DNN is not supported by the network, or the UE requested DNN is not in the Subscribed DNN List for the S-NSSAI (or its mapped value for the HPLMN in the case of LBO) and wildcard DNN is not included in the Subscribed DNN list), the AMF shall, based on operator policies received from PCF, either reject the NAS Message containing PDU Session Establishment Request from the UE with an appropriate cause or request PCF to replace the UE requested DNN by a selected DNN. If the DNN requested by the UE is present in the UE subscription information but indicated for replacement, the AMF shall request the PCF to perform a DNN replacement to a selected DNN. AMF requests DNN replacement as as specified in clause 4.16.2.1.1. If the DNN requested by the UE is present in the UE subscription information but not supported by the network and not indicated for replacement, the AMF shall reject the NAS Message containing PDU Session Establishment Request from the UE with an appropriate cause value.

The AMF selects an SMF as described in clause 6.3.2 of TS 23.501 [2] and clause 4.3.2.2.3. If the Request Type indicates "Initial request" or the request is due to handover from EPS or from non-3GPP access serving by a different AMF, the AMF stores an association of the S-NSSAI(s), the DNN, the PDU Session ID, the SMF ID as well as the Access Type of the PDU Session. During registration procedures, the AMF determines the use of the Control Plane CIoT 5GS Optimisation or User Plane CIoT 5GS Optimisation based on UEs indications in the 5G Preferred Network Behaviour, the serving operator policies and the network support of CIoT 5GS optimisations. The AMF selects an SMF that supports Control Plane CIoT 5GS optimisation or User Plane CIoT 5GS Optimisation as described in clause 6.3.2 of TS 23.501 [2]

If the Request Type is "initial request" and if the Old PDU Session ID indicating the existing PDU Session is also contained in the message, the AMF selects an SMF as described in clause 4.3.5.2 and stores an association of the new PDU Session ID, the S-NSSAI(s), the selected SMF ID as well as Access Type of the PDU Session.

If the Request Type indicates "Existing PDU Session", the AMF selects the SMF based on SMF-ID received from UDM. The case where the Request Type indicates "Existing PDU Session", and either the AMF does not recognize the PDU Session ID or the subscription context that the AMF received from UDM during the Registration or Subscription Profile Update Notification procedure does not contain an SMF ID corresponding to the PDU Session ID constitutes an error case. The AMF updates the Access Type stored for the PDU Session.

If the Request Type indicates "Existing PDU Session" referring to an existing PDU Session moved between 3GPP access and non-3GPP access, then if the Serving PLMN S-NSSAI of the PDU Session is present in the Allowed NSSAI of the target access type, the PDU Session Establishment procedure can be performed in the following cases:

- the SMF ID corresponding to the PDU Session ID and the AMF belong to the same PLMN;

- the SMF ID corresponding to the PDU Session ID belongs to the HPLMN;

Otherwise the AMF shall reject the PDU Session Establishment Request with an appropriate reject cause.

NOTE 2: The SMF ID includes the PLMN ID that the SMF belongs to.

The AMF shall reject a request coming from an Emergency Registered UE and the Request Type indicates neither "Emergency Request" nor "Existing Emergency PDU Session". When the Request Type indicates "Emergency Request", the AMF is not expecting any S-NSSAI and DNN value provided by the UE and uses locally configured values instead. The AMF stores the Access Type of the PDU Session.

If the Request Type indicates "Emergency Request" or "Existing Emergency PDU Session", the AMF selects the SMF as described in TS 23.501 [2], clause 5.16.4.

3. From AMF to SMF: Either Nsmf PDUSession CreateSMContext Request (SUPI, selected DNN, UE requested DNN, S-NSSAI(s), PDU Session ID, AMF ID, Request Type, PCF ID, Priority Access, [Small Data Rate Control Status], N1 SM container (PDU Session Establishment Request), User location information, Access Type, PEI, GPSI, UE presence inLADN service area, Subscription For PDU Session Status Notification, DNN Selection Mode, Trace Requirements, Control Plane CIoT 5GS Optimisation indication, or Control Plane Only indicator, NAS only flag) or Nsmf PDUSession UpdateSMContext Request (SUPI, DNN, S-NSSAI(s), SM Context ID, AMF ID, Request Type, N1 SM container (PDU Session Establishment Request), User location information, Access Type, RAT type, PEI, NAS only flag).

If the AMF does not have an association with an SMF for the PDU Session ID provided by the UE (e.g. when Request Type indicates "initial request"), the AMF invokes the Nsmf PDUSession CreateSMContext Request, but if the AMF already has an association with an SMF for the PDU Session ID provided by the UE (e.g. when Request Type indicates "existing PDU Session"), the AMF invokes the Nsmf PDUSession UpdateSMContext Request.

The AMF sends the S-NSSAI of the Serving PLMN from the Allowed NSSAI to the SMF. For roaming scenario in local breakout (LBO), the AMF also sends the corresponding S-NSSAI of the HPLMN from the Mapping Of Allowed NSSAI to the SMF. The AMF ID is the UE's GUAMI which uniquely identifies the AMF serving the UE. The AMF forwards the PDU Session ID together with the N1 SM container containing the PDU Session Establishment Request received from the UE. The GPSI shall be included if available at AMF.

The AMF determines Access Type and RAT Type, see clause 4.2.2.2.I.

The AMF provides the PEI instead of the SUPI when the UE in limited service state has registered for Emergency services (i.e. Emergency Registered) without providing a SUPI. The PEI is defined in TS 23.501 [2] clause 5.9.3. In case the UE in limited service state has registered for Emergency services (i.e. Emergency Registered) with a SUPI but has not been authenticated the AMF indicates that the SUPI has not been authenticated. The SMF determines that the UE has not been authenticated when it does not receive a SUPI for the UE or when the AMF indicates that the SUPI has not been authenticated.

If the AMF determines that the selected DNN corresponds to an LADN then the AMF provides the "UE presence in LADN service area" that indicates if the UE is IN or OUT of the LADN service area.

If the Old PDU Session ID is included in step 1, and if the SMF is not to be reallocated, the AMF also includes Old PDU Session ID in the Nsmf PDUSession CreateSMContext Request.

DNN Selection Mode is determined by the AMF. It indicates whether an explicitly subscribed DNN has been provided by the UE in its PDU Session Establishment Request.

The SMF may use DNN Selection Mode when deciding whether to accept or reject the UE request.

When the Establishment cause received as part of AN parameters during the Registration procedure or Service Request procedure is associated with priority services (e.g. MPS, MCS), the AMF includes a Message Priority header to indicate priority information. The SMF uses the Message Priority header to determine if the UE request is subject to exemption from NAS level congestion control. Other NFs relay the priority information by including the Message Priority header in service-based interfaces, as specified in TS 29.500 [17]

In the local breakout case, if the SMF (in the VPLMN) is not able to process some part of the N1 SM information that Home Routed Roaming is required, and the SMF responds to the AMF that it is not the right SMF to handle the N1 SM message by invoking Nsmf PDUSession CreateSMContext Response service operation. The SMF includes a proper N11 cause code triggering the AMF to proceed with home routed case. The procedure starts again at step 2 of clause 4.3.2.2.2.

The AMF may include a PCF ID in the Nsmf PDUSession CreateSMContext Request. This PCF ID identifies the H-PCF in the non-roaming case and the V-PCF in the local breakout roaming case.

The AMF includes Trace Requirements if Trace Requirements have been received in subscription data.

If the AMF decides to use the Control Plane CIoT 5GS Optimisation or User Plane CIoT 5GS Optimisation as specified in step 2 or to only use Control Plane CIoT 5GS Optimisation for the PDU session as described in clause 5.31.4 of TS 23.501 [2], the AMF sends the Control Plane CIoT 5GS Optimisation indication or Control Plane Only indicator to the SMF.

The AMF includes the latest Small Data Rate Control Status if it has stored it for the PDU Session.

The AMF may according to UE indicated “NAS only flag” in step 1 or based on local policy or other information (e.s. maximum allowed active user plane for a UE is reached), decided to not setup user plane for the PDU session, then the AMF shall include a “NAS only Has” to the SMF. SMF to AMF: Namf_Communication_NlN2MessageTransfer (PDU Session ID, N2 SM information (PDU Session ID, QFI(s), QoS Profile(s), CN Tunnel Info, S-NSSAI from the Allowed NSSAI, Session-AMBR, PDU Session Type, User Plane Security Enforcement information, UE Integrity Protection Maximum Data Rate, RSN), N1 SM container (PDU Session Establishment Accept ([QoS Rule(s) and QoS Flow level QoS parameters if needed for the QoS Flow(s) associated with the QoS rule(s)], selected SSC mode, S-NSSAI(s), UE Requested DNN, allocated IPv4 address, interface identifier, Session-AMBR, selected PDU Session Type, [Reflective QoS Timer] (if available), [P-CSCF address(es)], [Control Plane Only indicator], [Header Compression Configuration], [Always-on PDU Session Granted], [Small Data Rate Control parameters], [Small Data Rate Control Status]))). If multiple UPFs are used for the PDU Session, the CN Tunnel Info contain tunnel information related with the UPF that terminates N3.

The SMF may provide the SMF derived CN assisted RAN parameters tuning to the AMF by invoking Nsmf PDUSession SMContextStatusNotify (SMF derived CN assisted RAN parameters tuning) service.

The AMF stores the SMF derived CN assisted RAN parameters tuning in the associated PDU Session context for this UE.

The N2 SM information carries information that the AMF shall forward to the (R)AN which includes:

- The CN Tunnel Info corresponds to the Core Network address(es) of the N3 tunnel corresponding to the PDU Session. If two CN Tunnel Info are included for the PDU session for redundant transmission, the SMF also indicates the NG-RAN that one of the CN Tunnel Info used as the redundancy tunnel of the PDU session as described in clause 5.33.2.2 of TS 23.501 [2]

- One or multiple QoS profiles and the corresponding QFIs can be provided to the (R)AN. This is further described in TS 23.501 [2] clause 5.7. The SMF may indicate for each QoS Flow whether redundant transmission shall be performed by a corresponding redundant transmission indicator.

- The PDU Session ID may be used by AN signalling with the UE to indicate to the UE the association between (R)AN resources and a PDU Session for the UE.

- A PDU Session is associated to an S-NSSAI of the HPLMN and, if applicable, to a S-NSSAI of the VPLMN, and a DNN. The S-NSSAI provided to the (R)AN, is the S-NSSAI with the value for the Serving PLMN (i.e. the HPLMN S-NSSAI or, in LBO roaming case, the VPLMN S-NSSAI).

- User Plane Security Enforcement information is determined by the SMF as described in clause 5.10.3 of TS 23.501 [2]

- If the User Plane Security Enforcement information indicates that Integrity Protection is "Preferred" or "Required", the SMF also includes the UE Integrity Protection Maximum Data Rate as received in the PDU Session Establishment Request.

- The use of the RSN parameter by NG-RAN is described in TS 23.501 [2] clause 5.33.2.1.

If SMF has received the “NAS only flag” from AMF. or SMF decides to not setup user plane for the PDU session due to other local policy (e.2. UE is in a restricted area for data service), the N2 SM information shall not be provided by the SMF.

The N1 SM container contains the PDU Session Establishment Accept that the AMF shall provide to the UE. If the UE requested P-CSCF discovery then the message shall also include the P-CSCF IP address(es) as determined by the SMF and as described inTS 23.501 [2] clause 5.16.3.4. The PDU Session Establishment Accept includes S-NSSAI from the Allowed NSSAI. For LBO roaming scenario, the PDU Session Establishment Accept includes the S-NSSAI from the Allowed NSSAI for the VPLMN and also it includes the corresponding S-NSSAI of the HPLMN from the Mapping Of Allowed NSSAI that SMF received in step 3.

If the PDU Session being established was requested to be an always-on PDU Session, the SMF shall indicate whether the request is accepted by including an Always-on PDU Session Granted indication in the PDU Session Establishment Accept message. If the PDU Session being established was not requested to be an always-on PDU Session but the SMF determines that the PDU Session needs to be established as an always- on PDU Session, the SMF shall include an Always-on PDU Session Granted indication in the PDU Session Establishment Accept message indicating that the PDU session is an always-on PDU Session.

If Control Plane CIoT 5GS Optimisation is enabled for this PDU session, the N2 SM information is not included in this step. If Control Plane CIoT 5GS optimisation is enabled for this PDU session, and the UE has sent the Header Compression Configuration in the PDU Session Establishment Request, and the SMF supports the header compression parameters, the SMF shall include the Header Compression Configuration in the PDU Session Establishment Accept message. If the UE has included Header Compression Configuration in the PDU Session Establishment Request, the SMF may acknowledge Header Compression setup parameters. If the SMF has received the Control Plane Only Indicator in step 3, the SMF shall include the Control Plane Only Indicator in the PDU Session Establishment Accept message. The SMF shall indicate the use of Control Plane only on its CDR.

Multiple QoS Rules, QoS Flow level QoS parameters if needed for the QoS Flow(s) associated with those QoS mle(s) and QoS Profiles may be included in the PDU Session Establishment Accept within the N1 SM and in the N2 SM information.

The Namf_Communication_NlN2MessageTransfer contains the PDU Session ID allowing the AMF to know which access towards the UE to use.

If the PDU session establishment failed anywhere between step 5 and step 11, then the Namf Communication N lN2MessageTransfer request shall include the N 1 SM container with a PDU Session Establishment Reject message (see clause 8.3.3 of TS 24.501 [25]) and shall not include any N2 SM container. The (R)AN sends the NAS message containing the PDU Session Establishment Reject to the UE. In this case, steps 12-17 are skipped. AMF to (R)AN: N2 PDU Session Request (N2 SM information, NAS message (PDU Session ID, N1 SM container (PDU Session Establishment Accept)), [CN assisted RAN parameters tuning]).

The AMF sends the NAS message containing PDU Session ID and PDU Session Establishment Accept targeted to the UE and the N2 SM information received from the SMF within the N2 PDU Session Request to the (R)AN.

If the SMF derived CN assisted RAN parameters tuning are stored for the activated PDU Session(s), the AMF may derive updated CN assisted RAN parameters tuning and provide them the (R)AN.

If SMF does not provide N2 SM information in step 11 and only N1 SM container is provided, the AMF shall send N2 DL NAS transport including the N1 SM container. (R)AN to UE: The (R)AN may issue AN specific signalling exchange with the UE that is related with the information received from SMF. For example, in case of a NG-RAN, an RRC Connection Reconfiguration may take place with the UE establishing the necessary NG-RAN resources related to the QoS Rules for the PDU Session request received in step 12.

(R)AN also allocates (R)AN Tunnel Info for the PDU Session. In case of Dual Connectivity, the Master RAN node may assign some (zero or more) QFIs to be setup to a Master RAN node and others to the Secondary RAN node. The AN Tunnel Info includes a tunnel endpoint for each involved (R)AN node, and the QFIs assigned to each tunnel endpoint. A QFI can be assigned to either the Master RAN node or the Secondary RAN node and not to both.

If the (R)AN receives two CN Tunnel Info for a PDU session in step 12 for redundant transmission, (R)AN also allocates two AN Tunnel Info correspondingly, and indicate to SMF one of the AN Tunnel Info is used as the redundancy tunnel of the PDU session as described in clause 5.33.2.2 of TS 23.501 [2]

(R)AN forwards the NAS message (PDU Session ID, N1 SM container (PDU Session Establishment Accept)) provided in step 12 to the UE. (R)AN shall only provide the NAS message to the UE if the AN specific signalling exchange with the UE includes the (R)AN resource additions associated to the received N2 command.

(R)AN forwards the NAS message to UE directly if N2 DL NAS transport is received in step 12.

If MICO mode is active and the NAS message Request Type in step 1 indicated "Emergency Request", then the UE and the AMF shall locally deactivate MICO mode.

If the N2 SM information is not included in the step 11, then the following steps 14 to 16b and step 17 are omitted.

14. (R)AN to AMF: N2 PDU Session Response (PDU Session ID, Cause, N2 SM information (PDU Session ID, AN Tunnel Info, List of accepted/rejected QFI(s), User Plane Enforcement Policy Notification)).

The AN Tunnel Info corresponds to the Access Network address of the N3 tunnel corresponding to the PDU Session.

If the (R)AN rejects QFI(s) the SMF is responsible of updating the QoS rules and QoS Flow level QoS parameters if needed for the QoS Flow associated with the QoS mle(s) in the UE accordingly.

The NG-RAN rejects the establishment of UP resources for the PDU Session when it cannot fulfil User Plane Security Enforcement information with a value of Required. The NG-RAN notifies the SMF when it cannot fulfil a User Plane Security Enforcement with a value of Preferred.

If the NG-RAN can not establish redundant user plane for the PDU Session as indicated by the RSN parameter, the NG-RAN takes the decision on how to proceed with the the PDU Session as described in TS 23.501 [2]

15. AMF to SMF: Nsmf PDUSession UpdateSMContext Request (SM Context ID, N2 SM information,

Request Type).

The AMF forwards the N2 SM information received from (R)AN to the SMF.

If the list of rejected QFI(s) is included in N2 SM information, the SMF shall release the rejected QFI(s) associated QoS profiles.

If the N2 SM information indicates failure of user plane resource setup, the SMF shall reject the PDU session establishment by including a N1 SM container with a PDU Session Establishment Reject message (see clause 8.3.3 of TS 24.501 [25]) in the Nsmf PDUSession UpdateSMContext Response in step 17. Step 16 is skipped in this case and instead the SMF releases the N4 Session with UPF.

If the User Plane Enforcement Policy Notification in the N2 SM information indicates that no user plane resources could be established, and the User Plane Enforcement Policy indicated "required" as described in clause 5.10.3 of TS 23.501 [2], the SMF shall reject the PDU session establishment by including a N1 SM container with a PDU Session Establishment Reject message (see clause 8.3.3 of TS 24.501 [25]) in the Nsmf PDUSession UpdateSMContext Response in step 17. Step 16 is skipped in this case.

Claims

1. A method of operating a communication device, comprising: generating (402) a packet data session establishment request for establishing a packet data session and an indication that user plane resources are not expected, required or requested for the packet data session and/or an indication that the communication device supports packet data session initiation without user plane resources; and transmitting (404) the packet data session establishment request and the indication towards a core network node in a communication network.

2. The method of claim 1 , wherein the core network node comprises an access and mobility function,

AMF, in a 5G core network.

3. The method of claim 1 or 2, wherein transmitting the packet data session establishment request towards the core network node comprises transmitting the packet data session establishment request to a radio access node in a radio access network.

4. The method of any previous claim, wherein the indication is transmitted in a non-access stratum, NAS, transport message.

5. The method of claim 4, wherein the packet data session establishment request comprises a protocol data unit, PDU, session establishment message that is carried in the NAS transport message.

6. The method of claim 4 or 5, wherein the indication comprises a flag in the NAS transport message.

7. The method of claim 6, wherein the flag indicates that no user plane setup is expected, required or requested for this packet data session establishment and/or that the communication device supports packet data session without user plane resources.

8 The method of claim 7, wherein the flag comprises a NAS only flag.

9. The method of any previous claim, further comprising: receiving, in response to the packet data session establishment request, an indication that the packet data session has been established without user plane resources.

10. The method of any previous claim, wherein the user plane carries user data traffic between the communication device and the communication network.

11. A communication device (100), comprising: a processor circuit (116); a transceiver (112) coupled to the processor circuit; and a memory (118) coupled to the processor circuit, wherein the memory comprises computer readable program instructions that, when executed by the processor, cause the communication device to perform operations of: generating (402) a packet data session establishment request for establishing a packet data session and an indication that user plane resources are not requested for the packet data session; and transmitting (404) the packet data session establishment request and the indication towards a core network node.

12. The communication device of claim 10, further configured to perform operations according to any of claim 1 to 10.

13. A communication device (100) configured to: generate (402) a packet data session establishment request for establishing a packet data session and an indication that user plane resources are not requested for the packet data session; and transmit (404) the packet data session establishment request and the indication towards a core network node.

14. A method of operating a core network function in a core network, comprising: receiving (502) a packet data session establishment request from a communication device for establishing a packet data session; and establishing (504) the packet data session without user plane resources.

15. The method of claim 14, wherein the core network node comprises an access and mobility function, AMF, in a 5G core network.

16. The method of any of claim 14 to 15, further comprising: in response to the packet data session establishment request, transmitting a session context creation message or a session context update message to a session management function, SMF, of the core network, wherein the session context creation message or session context update message indicates that the SMF is not to establish a user plane for the packet data session.

17. The method of claim 16, wherein the session context creation message comprises a SmContextCreateData message or a SmContextUpdateData message.

18. The method of claim 17, wherein the SMContextCreateData message or SmContextUpdateData message omits an SMInformation information element.

19. The method of any of claim 14 to 18, wherein the packet data session establishment request includes an indication that user plane resources are not requested, expected or required for the packet data session.

20. The method of claim 19, wherein indication is carried in a non-access stratum, NAS, transport message.

21. The method of claim 20, wherein packet data session establishment request is carried in the NAS transport message.

22. The method of claim 20, wherein the indication comprises a flag in the NAS transport message.

23. The method of claim 22, wherein the flag indicates that no user plane setup is expected, requested or required for this packet data session establishment.

BO

24. The method of claim 22, wherein the flag comprises a NAS only flag.

25. The method of any of claim 14 to 24, further comprising: following establishment of the packet data session, transmitting an indication that the packet data session has been established without user plane resources.

26. The method of any of claim 14 to 18, further comprising: determining, in response to the packet data session establishment request, that user plane resources are not to be established for the packet data session.

27. The method of claim 26, wherein determining that user plane resources are not to be established for the packet data session is performed based on a configuration setting.

28. A core network node (200), comprising: a processor circuit (206); a network interface (204); and a memory (208) coupled to the processor circuit, wherein the memory comprises computer readable program instructions that, when executed by the processor, cause the communication device to perform operations of: receiving (502) a packet data session establishment request from a communication device for establishing a packet data session; and establishing (504) the packet data session without user plane resources.

29. The core network node of claim 28, further configured to perform operations according to any of claim 14 to 27.

30. A core network node (200) configured to: receive (502) a packet data session establishment request from a communication device for establishing a packet data session; and establish (504) the packet data session without user plane resources.