WO2023141874A1

WO2023141874A1 - Methods, devices, and systems for performing network slice replacement

Info

Publication number: WO2023141874A1
Application number: PCT/CN2022/074290
Authority: WO
Inventors: Menghan WANG; Shuang Liang; Jinguo Zhu
Original assignee: Zte Corporation
Priority date: 2022-01-27
Filing date: 2022-01-27
Publication date: 2023-08-03
Also published as: CN117981393A

Abstract

The present disclosure describes methods, system, and devices for performing network slice replacement during protocol data unit (PDU) session modification procedure or service request procedure. One method includes selecting, by a radio-access network (RAN), a single-network slice selection assistant information (S-NSSAI) to replace a serving S-NSSAI for a PDU session; and sending, by the RAN, a message including network slice replacement information for the PDU session to an access and mobility management function (AMF). Another method includes receiving, by an AMF, a message for network slice replacement for a PDU session from a RAN; and determining, by the AMF, whether to accept the PDU session that requires slice replacement with a corresponding S-NSSAI based on the message.

Description

METHODS, DEVICES, AND SYSTEMS FOR PERFORMING NETWORK SLICE REPLACEMENT

TECHNICAL FIELD

The present disclosure is directed generally to wireless communications. Particularly, the present disclosure relates to methods, devices, and systems for performing network slice replacement during protocol data unit (PDU) session modification procedure or service request procedure.

BACKGROUND

Wireless communication technologies are moving the world toward an increasingly connected and networked society. High-speed and low-latency wireless communications rely on efficient network resource management and allocation among one or more user equipment and one or more wireless access network nodes (including but not limited to base stations) . A new generation network is expected to provide high speed, low latency and ultra-reliable communication capabilities and fulfill the requirements from different industries and users.

With the rapid evolution of cellular mobile communication systems, for example in the present wireless telecommunication protocol, support of network slice service continuity may have various problems/issues, being challenged under some circumstances, for example but not limited to, due to operation, administration, and maintenance (OAM) reason or slice congestion in a radio access network (RAN) .

The present disclosure describes various embodiments for performing network slice replacement in various circumstances, for example, during session modification procedure and/or service request procedure, addressing at least one of the problems/issues discussed above. The various embodiments in the present disclosure may increase efficiency and performance of service continuity for the UE, thus improving user experience and/or a technology field in the wireless communication.

SUMMARY

This document relates to methods, systems, and devices for wireless communication, and more specifically, for performing network slice replacement during protocol data unit (PDU) session modification procedure or service request procedure.

In one embodiment, the present disclosure describes a method for wireless communication. The method includes selecting, by a radio-access network (RAN) , a single-network slice selection assistant information (S-NSSAI) to replace a serving S-NSSAI for a protocol data unit (PDU) session; and sending, by the RAN, a message including network slice replacement information for the PDU session to an access and mobility management function (AMF) .

In another embodiment, the present disclosure describes a method for wireless communication. The method includes receiving, by an access and mobility management function (AMF) , a message for network slice replacement for a protocol data unit (PDU) session from a radio-access network (RAN) ; and determining, by the AMF, whether to accept the PDU session that requires slice replacement with a corresponding single-network slice selection assistant information (S-NSSAI) based on the message.

In another embodiment, the present disclosure describes a method for wireless communication. The method includes receiving, by a session management function (SMF) , a first single-network slice selection assistant information (S-NSSAI) corresponding to a protocol data unit (PDU) session that requires slice replacement from an access and mobility management function (AMF) ; determining, by the SMF, whether to accept the PDU session with the first S-NSSAI; in response to determining to accept the PDU session: triggering, by the SMF, replacement of a second S-NSSAI with the first S-NSSAI for the PDU session, and storing, by the SMF, the S-NSSAI and the second S-NSSAI associated with a same PDU session identity; in response to determining not to accept the PDU session: triggering, by the SMF, a PDU session release procedure; and sending, by the SMF, a N4 message to a user plan function (UPF) , the N4 message comprising at least one of the following: the first S-NSSAI, a network instance, or an updated rule.

In another embodiment, the present disclosure describes a method for wireless communication. The method includes receiving, by a session management function (SMF) , a network slice replacement fallback indication from an access and mobility management function (AMF) , the fallback indication indicating to replace a first single-network slice selection assistant information (S-NSSAI) with a second S-NSSAI for the associated PDU session, the second S-NSSAI corresponding to a PDU session when the PDU session is first established; determining, by the SMF, whether to accept the network slice replacement for the PDU session with the second S-NSSAI; in response to determining to accept the network slice replacement with the second S-NSSAI: removing, by the SMF, the first S-NSSAI associated with the PDU session that is stored by the SMF, and sending, by the SMF, a N4 message to a user plan function (UPF) , the N4 message comprising at least one of the following: the second S-NSSAI, access network (AN) tunnel information, a network instance, or an updated rule.

In another embodiment, the present disclosure describes a method for wireless communication. The method includes receiving, by a user plan function (UPF) , a request message from a session management function (SMF) , the request message comprising at least one of the following: a single-network slice selection assistant information (S-NSSAI) corresponding to a protocol data unit (PDU) session that requires slice replacement, a network instance, or an updated rule; and sending, by the UPF, a response message to the SMF, the response message comprising a core network (CN) tunnel information.

In some other embodiments, an apparatus for wireless communication may include a memory storing instructions and a processing circuitry in communication with the memory. When the processing circuitry executes the instructions, the processing circuitry is configured to carry out the above methods.

In some other embodiments, a device for wireless communication may include a memory storing instructions and a processing circuitry in communication with the memory. When the processing circuitry executes the instructions, the processing circuitry is configured to carry out the above methods.

In some other embodiments, a computer-readable medium comprising instructions which, when executed by a computer, cause the computer to carry out the above methods.

The above and other aspects and their implementations are described in greater detail in the drawings, the descriptions, and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A shows an example of a wireless communication system include more than one wireless access network node and one or more user equipment.

FIG. 1B shows an exemplary communication network including various terminal devices, a carrier network, data network, and service applications.

FIG. 1C shows exemplary network functions or network nodes in a communication network.

FIG. 2 shows an example of a network node.

FIG. 3 shows an example of a user equipment.

FIG. 4A shows a flow diagram of a method for wireless communication.

FIG. 4B shows a flow diagram of a method for wireless communication.

FIG. 4C shows a flow diagram of a method for wireless communication.

FIG. 4D shows a flow diagram of a method for wireless communication.

FIG. 4E shows a flow diagram of a method for wireless communication.

FIG. 5 shows a schematic diagram of an exemplary embodiment for wireless communication.

FIG. 6 shows a schematic diagram of an exemplary embodiment for wireless communication.

FIG. 7 shows a schematic diagram of an exemplary embodiment for wireless communication.

FIG. 8 shows a schematic diagram of an exemplary embodiment for wireless communication.

FIG. 9 shows a schematic diagram of an exemplary embodiment for wireless communication.

DETAILED DESCRIPTION

The present disclosure will now be described in detail hereinafter with reference to the accompanied drawings, which form a part of the present disclosure, and which show, by way of illustration, specific examples of embodiments. Please note that the present disclosure may, however, be embodied in a variety of different forms and, therefore, the covered or claimed subject matter is intended to be construed as not being limited to any of the embodiments to be set forth below.

Throughout the specification and claims, terms may have nuanced meanings suggested or implied in context beyond an explicitly stated meaning. Likewise, the phrase “in one embodiment” or “in some embodiments” as used herein does not necessarily refer to the same embodiment and the phrase “in another embodiment” or “in other embodiments” as used herein does not necessarily refer to a different embodiment. The phrase “in one implementation” or “in some implementations” as used herein does not necessarily refer to the same implementation and the phrase “in another implementation” or “in other implementations” as used herein does not necessarily refer to a different implementation. It is intended, for example, that claimed subject matter includes combinations of exemplary embodiments or implementations in whole or in part.

In general, terminology may be understood at least in part from usage in context. For example, terms, such as “and” , “or” , or “and/or, ” as used herein may include a variety of meanings that may depend at least in part upon the context in which such terms are used. Typically, “or” if used to associate a list, such as A, B or C, is intended to mean A, B, and C, here used in the inclusive sense, as well as A, B or C, here used in the exclusive sense. In addition, the term “one or more” or “at least one” as used herein, depending at least in part upon context, may be used to describe any feature, structure, or characteristic in a singular sense or may be used to describe combinations of features, structures or characteristics in a plural sense. Similarly, terms, such as “a” , “an” , or “the” , again, may be understood to convey a singular usage or to convey a plural usage, depending at least in part upon context. In addition, the term “based on” or “determined by” may be understood as not necessarily intended to convey an exclusive set of factors and may, instead, allow for existence of additional factors not necessarily expressly described, again, depending at least in part on context.

The present disclosure describes various methods and devices for performing network slice replacement during protocol data unit (PDU) session modification procedure or service request procedure.

With the rapid evolution of cellular mobile communication systems, for example in the present wireless telecommunication protocol, support of network slice service continuity may have various problems/issues, being challenged under some circumstances, for example but not limited to, due to operation, administration, and maintenance (OAM) reason or slice congestion in a radio access network (RAN) . One of the problems/issues may include solutions with core network and/or user equipment (UE) impacted from end-to-end system point of view are unclear. Under some circumstances, a new generation RAN (NG-RAN) may decide to release some or all PDU sessions established on a specific a single-network slice selection assistant information (S-NSSAI) , e.g. due to OAM reasons or network slice congestion; and with such PDU sessions being released, the network slice service continuity may not be guaranteed for the impacted UEs.

The present disclosure describes various embodiments for network slice replacement during protocol data unit (PDU) session modification procedure or service request procedure, so as to support network slice service continuity during UE mobility in some scenarios wherein the network slice is unavailable or the network slice resource is insufficient in the NG-RAN node. The various embodiments may at least address the above issue/problem, supporting service continuity for the UEs.

In various embodiments in the present disclosure, a radio access network (RAN) may refer to a new generation radio access network (NG-RAN) ; and/or in various embodiments, “RAN” and “NG-RAN” may be used interchangeably. In the present disclosure, a network slice may refer to a logical network that provides specific network capabilities and network characteristics; and/or a network slice instance may refer to a set of network function instances and the required resources (e.g. compute, storage and networking resources) which form a deployed network slice.

FIG. 1A shows a wireless communication system 100 including a portion or all of the following: a core network (CN, 102) , one or more access network node (or radio access network (RAN) , 118 and 119) , and/or one or more user equipment (UE) (110, 111, and 112) .

The core network (102) may communicate with the one or more access network node (118 and/or 119) . The UE may connect to one network node 118, for example, a radio access network (RAN) node (118 or 119) and/or a core network (CN) node (102) . The wireless network node (118 and 119) may include a network base station, which may be a nodeB (NB, e.g., a gNB) in a mobile telecommunications context. Each of the UE (110, 111, and/or 112) may wirelessly communicate with the wireless network node (118 and/or 119) via one or more radio channels 115. For example, the first UE 110 may wirelessly communicate with the first network node 118 via a channel including a plurality of radio channels during a certain period of time; during another period of time, the first UE 110 may wirelessly communicate with the second network node 119 via a channel including a plurality of radio channels.

An exemplary communication network in various embodiments, shown as 120 in FIG. 1B, may include a portion or all of the following:

terminal devices

121 and 122, a carrier network 123, various service applications 129, and other data networks 128. The carrier network 123, for example, may include access networks (or radio access network (RAN) 124) and a core network 126. The carrier network 123 may be configured to transmit voice, data, and other information (collectively referred to as data traffic) among

terminal devices

121 and 122, between the terminal devices and the service applications 129, and/or between the terminal devices and the other data networks 128. Communication sessions and corresponding data paths may be established and configured for such data transmission. The access networks 124 may be configured to provide terminal devices network access to the core network 126. The access network may, for example, support wireless access via radio resources, or wireline access. The core network may include various network nodes or network functions configured to control the communication sessions and perform network access management and data traffic routing. The service applications may be hosted by various application servers that are accessible by the terminal devices through the core network of the carrier network. A service application 129 may be deployed as a data network outside of the core network. Likewise, the other data networks 128 may be accessible by the terminal devices through the core network 126 and may appear as either data destination or data source of a particular communication session instantiated in the carrier network 123.

The core network 126 of FIG. 1B may include various network nodes or functions geographically distributed and interconnected to provide network coverage of a service region of the carrier network 123. These network nodes or functions may be implemented as dedicated hardware network elements. Alternatively, these network nodes or functions may be virtualized and implemented as virtual machines or as software entities. A network node may each be configured with one or more types of network functions. These network nodes or network functions may collectively provide the provisioning and routing functionalities of the core network 126. The term “network nodes” and “network functions” are used interchangeably in this disclosure.

FIG. 1C further shows an exemplary architecture of a 5G system (5GS) , which also shows an exemplary division of network functions (NFs) in a core network of a communication network 150. While only single instances of network nodes or network functions are illustrated in FIG. 1C, those having ordinary skill in the art readily understand that each of these network nodes may be instantiated as multiple instances of network nodes that are distributed throughout the core network.

As shown in FIG. 1C, the 5GS may include at least one UE (152) , at least one RAN (154) , at least one core network (155) , and/or at least one data network (DN, 170) . The core network may include, but is not limited to, a portion or all of the following: at least one access and mobility management function (AMF) , at least one session management function (SMF) , and/or at least one user plane function (UPF) . Exemplary signaling and data exchange between the various types of network nodes/functions through various communication interfaces are indicated by the various connection lines in FIG. 1C. Such signaling and data exchange may be carried by signaling or data messages following predetermined formats or protocols.

Referring to the at least one RAN (154) , during UE mobility, inter-NG-RAN handover procedure may be initiated to hand over the UE from a source NG-RAN (Source NG-RAN) to a target NG-RAN (Target NG-RAN) .

Referring to the AMF (156) , this network function (NF) may include functionalities such as UE Mobility Management, Reachability Management, Connection Management and Registration Management. The AMF terminates the RAN control plane (CP) interface N2 and non-access stratum (NAS) interface N1, NAS ciphering and integrity protection. It also transparently transmits N2 SM information between the RAN and the SMF.

Referring to the SMF (158) , this NF includes the following functionalities: session establishment, modification and release, UE IP address allocation &management, selection and control of user plane (UP) function, etc.

Referring to the UPF (160) , this NF serves as an anchor point for intra-/inter-radio access technology (RAT) mobility and as the external PDU session point of interconnect to the data network (DN) . The UPF also routes and forwards the data packet according to the indication from the SMF. It also buffers the downlink (DL) data when the UE is in idle mode. The UPF may receives uplink user plane traffic from the RAN and transmits downlink user plane traffic to the RAN via an N3 interface.

FIG. 2 shows an example of electronic device 200 to implement a network base station. The example electronic device 200 may include radio transmitting/receiving (Tx/Rx) circuitry 208 to transmit/receive communication with UEs and/or other base stations. The electronic device 200 may also include network interface circuitry 209 to communicate the base station with other base stations and/or a core network, e.g., optical or wireline interconnects, Ethernet, and/or other data transmission mediums/protocols. The electronic device 200 may optionally include an input/output (I/O) interface 206 to communicate with an operator or the like.

The electronic device 200 may also include system circuitry 204. System circuitry 204 may include processor (s) 221 and/or memory 222. Memory 222 may include an operating system 224, instructions 226, and parameters 228. Instructions 226 may be configured for the one or more of the processors 124 to perform the functions of the network node. The parameters 228 may include parameters to support execution of the instructions 226. For example, parameters may include network protocol settings, bandwidth parameters, radio frequency mapping assignments, and/or other parameters.

FIG. 3 shows an example of an electronic device to implement a terminal device 300 (for example, user equipment (UE) ) . The UE 300 may be a mobile device, for example, a smart phone or a mobile communication module disposed in a vehicle. The UE 300 may include communication interfaces 302, a system circuitry 304, an input/output interfaces (I/O) 306, a display circuitry 308, and a storage 309. The display circuitry may include a user interface 310. The system circuitry 304 may include any combination of hardware, software, firmware, or other logic/circuitry. The system circuitry 304 may be implemented, for example, with one or more systems on a chip (SoC) , application specific integrated circuits (ASIC) , discrete analog and digital circuits, and other circuitry. The system circuitry 304 may be a part of the implementation of any desired functionality in the UE 300. In that regard, the system circuitry 304 may include logic that facilitates, as examples, decoding and playing music and video, e.g., MP3, MP4, MPEG, AVI, FLAC, AC3, or WAV decoding and playback; running applications; accepting user inputs; saving and retrieving application data; establishing, maintaining, and terminating cellular phone calls or data connections for, as one example, internet connectivity; establishing, maintaining, and terminating wireless network connections, Bluetooth connections, or other connections; and displaying relevant information on the user interface 310. The user interface 310 and the inputs/output (I/O) interfaces 306 may include a graphical user interface, touch sensitive display, haptic feedback or other haptic output, voice or facial recognition inputs, buttons, switches, speakers and other user interface elements. Additional examples of the I/O interfaces 306 may include microphones, video and still image cameras, temperature sensors, vibration sensors, rotation and orientation sensors, headset and microphone input /output jacks, Universal Serial Bus (USB) connectors, memory card slots, radiation sensors (e.g., IR sensors) , and other types of inputs.

Referring to FIG. 3, the communication interfaces 302 may include a Radio Frequency (RF) transmit (Tx) and receive (Rx) circuitry 316 which handles transmission and reception of signals through one or more antennas 314. The communication interface 302 may include one or more transceivers. The transceivers may be wireless transceivers that include modulation /demodulation circuitry, digital to analog converters (DACs) , shaping tables, analog to digital converters (ADCs) , filters, waveform shapers, filters, pre-amplifiers, power amplifiers and/or other logic for transmitting and receiving through one or more antennas, or (for some devices) through a physical (e.g., wireline) medium. The transmitted and received signals may adhere to any of a diverse array of formats, protocols, modulations (e.g., QPSK, 16-QAM, 64-QAM, or 256-QAM) , frequency channels, bit rates, and encodings. As one specific example, the communication interfaces 302 may include transceivers that support transmission and reception under the 2G, 3G, BT, WiFi, Universal Mobile Telecommunications System (UMTS) , High Speed Packet Access (HSPA) +, 4G /Long Term Evolution (LTE) , 5G, 6G, any further tele-communication generation, and/or any future generation wireless communication standards. The techniques described below, however, are applicable to other wireless communications technologies whether arising from the 3rd Generation Partnership Project (3GPP) , GSM Association, 3GPP2, IEEE, or other partnerships or standards bodies.

Referring to FIG. 3, the system circuitry 304 may include one or more processors 321 and memories 322. The memory 322 stores, for example, an operating system 324, instructions 326, and parameters 328. The processor 321 is configured to execute the instructions 326 to carry out desired functionality for the UE 300. The parameters 328 may provide and specify configuration and operating options for the instructions 326. The memory 322 may also store any BT, WiFi, 3G, 4G, 5G, 6G, any further tele-communication generation, or other data that the UE 300 will send, or has received, through the communication interfaces 302. In various implementations, a system power for the UE 300 may be supplied by a power storage device, such as a battery or a transformer.

The present disclosure describes various embodiments, which may be implemented, partly or totally, on the network base station and/or the user equipment described above in FIGS. 2-3.

Referring to FIG. 4A, the present disclosure describes various embodiments of a method 400 for wireless communication. The method 400 may include a portion or all of the following steps: step 402, selecting, by a radio-access network (RAN) , a single-network slice selection assistant information (S-NSSAI) to replace a serving S-NSSAI for a protocol data unit (PDU) session; and step 404, sending, by the RAN, a message including network slice replacement information for the PDU session to an access and mobility management function (AMF) . In some implementations, the S-NSSAI may refer to an old S-NSSAI, and the serving S-NSSAI may refer to a backup S-NSSAI. In some other implementations, the S-NSSAI may refer to a backup S-NSSAI, and the serving S-NSSAI may refer to an old S-NSSAI. In some other implementations, the message may be a N2 path switch request message.

In some other implementations, the RAN selects, from network slice selection assistant information (NSSAI) , the S-NSSAI to replace the serving S-NSSAI associated with the PDU session, and the message comprises the S-NSSAI. Various implementations may be under a non-roaming and/or roaming with local break-out (LBO) scenario. The S-NSSAI may be a backup S-NSSAI, and/or the serving S-NSSAI may be an old S-NSSAI.

In some other implementations, the NSSAI comprises a list of S-NSSAIs that is allowed to use for a user equipment (UE) .

In some other implementations, the method 400 may optionally further include receiving, by the RAN, an updated CN tunnel information or an updated QoS profile for the PDU session from the AMF.

In some other implementations, in response to determining a network slice replacement fallback for the PDU session, the message comprises a fallback indication indicating to the AMF to replace the serving S-NSSAI with the S-NSSAI, the S-NSSAI corresponding to the PDU session when the PDU session is first established. Various implementation may be performed under a fall back scenario. The S-NSSAI may be an old S-NSSAI; and/or the serving S-NSSAI may be a backup S-NSSAI.

In some other implementations, in response to the RAN receiving the S-NSSAI and the serving S-NSSAI for the PDU session and not accepting an activation of user plane (UP) connection for the PDU session on the serving S-NSSAI: the RAN accepts the activation of user plane (UP) connection for the PDU session on the S-NSSAI, the S-NSSAI corresponding to the PDU session when the PDU session is first established; and the message comprises one of the following: a fallback indication indicating to the AMF the activation of UP connection for the PDU session on the S-NSSAI and corresponding access network (AN) tunnel information, or the S-NSSAI and corresponding access network (AN) tunnel information. Various implementations may be performed under a scenario of a UE initiated service request procedure to activate user plane (UP) connection for the PDU session. The S-NSSAI may be an old S-NSSAI; and/or a serving S-NSSAI may be a backup S-NSSAI.

Referring to FIG. 4B, the present disclosure describes various embodiments of a method 420 for wireless communication. The method 420 may include a portion or all of the following steps: step 422, receiving, by an access and mobility management function (AMF) , a message for network slice replacement for a protocol data unit (PDU) session from a radio-access network (RAN) ; and step 424, determining, by the AMF, whether to accept the PDU session that requires slice replacement with a corresponding single-network slice selection assistant information (S-NSSAI) based on the message.

In some implementations, the message comprises a first S-NSSAI; the AMF determines whether to accept the PDU session that requires slice replacement with the first S-NSSAI; and in response to determining to accept the PDU session with the first S-NSSAI, the AMF sends the first S-NSSAI corresponding to the PDU session to a corresponding session management function (SMF) .

In some other implementations, the first S-NSSAI is configured to replace a second S-NSSAI, the second S-NSSAI corresponding to the PDU session that require slice replacement when the PDU session is first established. The second S-NSSAI may be an old S-NSSAI.

In some other implementations, the step 424 may optionally include determining, by the AMF, whether the first S-NSSAI and the second S-NSSAI are supported by a same SMF; in response to determining that the first S-NSSAI and the second S-NSSAI are supported by the same SMF, determining, by the AMF, to accept the PDU session; and/or in response to determining that the first S-NSSAI and the second S-NSSAI are not supported by the same SMF, determining, by the AMF, not to accept the PDU session.

In some other implementations, the method 420 may optionally include in response to determining to accept the PDU session: sending, by the AMF, corresponding N2 SM information and the first S-NSSAI to the corresponding SMF, and/or storing, by the AMF, the first S-NSSAI and the second S-NSSAI corresponding to a same PDU session identity.

In some other implementations, the message comprises a network slice replacement fallback indication indicating to the AMF to replace a first S-NSSAI with a second S-NSSAI for the PDU session, the second S-NSSAI corresponding to the PDU session when the PDU session is first established; and/or the AMF sends the network slice replacement fallback indication for the PDU session to a corresponding SMF. The first S-NSSAI may be a backup S-NSSAI; and/or the second S-NSSAI may be an old S-NSSAI.

In some other implementations, the message comprises a second S-NSSAI, the second S-NSSAI corresponding to the PDU session when the PDU session is first established; and/or the AMF sends the message to a corresponding SMF, the message comprising the second S-NSSAI for the PDU session. The second S-NSSAI may be an old S-NSSAI.

Referring to FIG. 4C, the present disclosure describes various embodiments of a method 440 for wireless communication. The method 440 may include a portion or all of the following steps: step 442, receiving, by a session management function (SMF) , a first single-network slice selection assistant information (S-NSSAI) corresponding to a protocol data unit (PDU) session that requires slice replacement from an access and mobility management function (AMF) ; step 444, determining, by the SMF, whether to accept the PDU session with the first S-NSSAI; step 446, in response to determining to accept the PDU session: triggering, by the SMF, replacement of a second S-NSSAI with the first S-NSSAI for the PDU session, and/or storing, by the SMF, the S-NSSAI and the second S-NSSAI associated with a same PDU session identity; and/or step 448, in response to determining not to accept the PDU session: triggering, by the SMF, a PDU session release procedure; and/or sending, by the SMF, a N4 message to a user plan function (UPF) , the N4 message comprising at least one of the following: the first S-NSSAI, a network instance, or an updated rule.

Referring to FIG. 4D, the present disclosure describes various embodiments of a method 460 for wireless communication. The method 460 may include a portion or all of the following steps: step 462, receiving, by a session management function (SMF) , a network slice replacement fallback indication from an access and mobility management function (AMF) , the fallback indication indicating to replace a first single-network slice selection assistant information (S-NSSAI) with a second S-NSSAI for the associated PDU session, the second S-NSSAI corresponding to a PDU session when the PDU session is first established; step 464, determining, by the SMF, whether to accept the network slice replacement for the PDU session with the second S-NSSAI; step 466, in response to determining to accept the network slice replacement with the second S-NSSAI: removing, by the SMF, the first S-NSSAI associated with the PDU session that is stored by the SMF, and/or sending, by the SMF, a N4 message to a user plan function (UPF) , the N4 message comprising at least one of the following: the second S-NSSAI, access network (AN) tunnel information, a network instance, or an updated rule. The first S-NSSAI may be a backup S-NSSAI; and/or the second S-NSSAI may be an old S-NSSAI.

In some implementations, the SMF provides the first S-NSSAI and the second S-NSSAI to the RAN.

In some other implementations, the SMF sends an updated core network (CN) tunnel information and an updated quality of service (QoS) profile to the RAN.

Referring to FIG. 4E, the present disclosure describes various embodiments of a method 480 for wireless communication. The method 480 may include a portion or all of the following steps: step 482, receiving, by a user plan function (UPF) , a request message from a session management function (SMF) , the request message comprising at least one of the following: a single-network slice selection assistant information (S-NSSAI) corresponding to a protocol data unit (PDU) session that requires slice replacement, a network instance, or an updated rule; and/or step 484, sending, by the UPF, a response message to the SMF, the response message comprising a core network (CN) tunnel information. In some implementations, the S-NSSAI may refer to an old S-NSSAI. In some other implementations, the S-NSSAI may refer to a backup S-NSSAI.

In some other implementations, the method 480 may optionally further include determining, by the UPF, internal UPF resources based on the S-NSSAI or the network instance; and/or allocating, by the UPF, the CN tunnel information based on the request message from the SMF.

Below, the present disclosure describes various exemplary embodiments in more details, which should be regarded as examples only, and do not impose any limitation on various embodiments in the present disclosure. Any portion (e.g., one step or several steps) of a single embodiment or a plurality of embodiments may be combined or arranged in any amount or in any order, as desired. In some embodiments, one or more steps may be performed in parallel, as desired.

FIG. 5 shows a schematic diagram of an exemplary embodiment for a RAN requested PDU session modification procedure in non-roaming and/or roaming with local break-out (LBO) scenario, including a portion or all of the following: a NG-RAN 582, an AMF 590, an SMF 592, and/or an UPF 594.

Roaming is a feature of telecommunication system which allows one or more subscribers to use their mobile service outside of their home networks. Their home network may refer to their service provider’s coverage area. Roaming services may include, but not limited to, making or receiving calls, sending or receiving mobile data, performing supplementary services e.g., call forwarding, etc. In local break-out (LBO) roaming, data traffic may be routed directly from a visiting (or visitor) network (V-Network) to a data network while authentication and handling of subscription data may be handled by the home network. In some cases, only signaling data may be routed to the home network. In home-routed (HR) roaming, an IP Address may be obtained from the home network; and/or a UE may communicate with a visiting (or visitor) SMF (V-SMF) from the visiting network, a visiting (or visitor) UPF (V-UPF) from the visiting network, a home SMF (H-SMF) from the home network, and/or a home UPF (H-UPF) from the home network.

Referring to step 5-1, the NG-RAN (or RAN) may decide to initiate a PDU session modification procedure for one or more PDU sessions.

Referring to step 5-2, the NG-RAN may initiate the PDU session modification procedure by sending a N2 message, i.e. PDU SESSION RESOURCE MODIFY INDICATION message, to the AMF. The message includes a PDU session resource modify indication list, with an PDU session identifier (ID) and N2 SM information for each item in the list. The list may include one or more PDU sessions. The N2 SM information includes access network (AN) tunnel information.

Referring to step 5-3, the AMF may send a Nsmf_PDUSession_UpdateSMContext request message to the corresponding SMF associated with the PDU session. The message may include the N2 SM information.

Referring to step 5-4, when the SMF decides to accept the PDU session modification, the SMF may update the UPF with N4 rules related to new or modified quality of service (QoS) flow (s) . When the SMF cannot accept the PDU session modification, the SMF includes the PDU session associated with the failure cause in the PDU session resource failed to modify list and return to the NG-RAN.

Referring to step 5-5, the SMF updates the UPF with the N4 rules related to new or modified QoS flow (s) .

Referring to step 5-6, the UPF returns an N4 session modification/establishment response message to the SMF with updated information when available.

Referring to step 5-7, the SMF sends an Nsmf_PDUSession_UpdateSMContext response message including N2 SM information to the AMF. For accepted PDU session, the N2 SM information includes core network (CN) tunnel information, updated parameters for the accepted QoS flows. For a failed PDU session, the N2 SM information includes corresponding failure cause.

Referring to step 5-8, the AMF sends a N2 message, i.e. PDU SESSION RESOURCE MODIFY CONFIRM message, to the NG-RAN. The message includes a PDU session resource modify confirm list, with a PDU session ID and corresponding N2 SM information for each PDU session. The list may include zero, one or more PDU sessions. The corresponding N2 SM information includes CN tunnel information, and/or updated parameters for the accepted QoS flows. The message may also include a PDU session resource failed to modify list, with a PDU session ID and corresponding N2 SM information for each PDU session. The list may include zero, one or more PDU sessions. The corresponding N2 SM information includes the failure cause.

FIG. 6 shows a schematic diagram of an exemplary embodiment for performing network slice replacement during a RAN requested PDU session modification procedure in home-routed (HR) roaming scenario, including a portion or all of the following: a NG-RAN 682, an AMF 690, a V-SMF 692, a V-UPF 694, a H-SMF 696, and/or a H-UPF 698.

Referring to step 6-1, the NG-RAN (or RAN) may decide to initiate a PDU session modification procedure for one or more PDU sessions.

Referring to step 6-2, the NG-RAN initiates the PDU session modification procedure by sending a N2 message, i.e. PDU SESSION RESOURCE MODIFY INDICATION message, to the AMF. The message includes a PDU session resource modify indication list, with a PDU session ID and N2 SM information for each item in the list. The list may include one or more PDU sessions. The N2 SM information includes AN tunnel information.

Referring to step 6-3, the AMF sends a Nsmf_PDUSession_UpdateSMContext request message to the corresponding V-SMF associated with the PDU session. The message includes the N2 SM information.

Referring to step 6-4, the V-SMF sends a Nsmf_PDUSession_Update request message to the H-SMF. The message includes the N2 SM information.

Referring to step 6-5, when the H-SMF decides to accept the PDU session modification, the H-SMF may update the H-UPF with N4 rules related to new or modified QoS flow (s) . When the H-SMF cannot accept the PDU session modification, the H-SMF includes the PDU session associated with the failure cause in the PDU session resource failed to modify list and return to the NG-RAN.

Referring to step 6-6, the H-SMF may update the H-UPF with N4 rules related to new or modified QoS flow (s) .

Referring to step 6-7, the H-UPF responds to the H-SMF with updated information when available.

Referring to step 6-8, the H-SMF sends a Nsmf_PDUSession_Update response message to the V-SMF. For one or more accepted PDU session, the message includes updated CN tunnel information, updated parameters for the accepted QoS flows. For one or more failed PDU session, the message includes corresponding failure cause.

Referring to step 6-9, the V-SMF may update the V-UPF with N4 rules related to new or modified QoS flow (s) .

Referring to step 6-10, the V-UPF responds to the V-SMF with updated information when available.

Referring to step 6-11, the V-SMF sends an Nsmf_PDUSession_UpdateSMContext response message including N2 SM information to the AMF. For one or more accepted PDU session, the N2 SM information includes updated CN tunnel information, updated parameters for the accepted QoS flows. For one or more failed PDU session, the N2 SM information includes corresponding failure cause.

Referring to step 6-12, the AMF sends a N2 message, e.g. PDU SESSION RESOURCE MODIFY CONFIRM message, to the NG-RAN. The message includes a PDU session resource modify confirm list, with a PDU session ID and corresponding N2 SM information for each PDU session. The list may include zero, one or more PDU sessions. The corresponding N2 SM information includes CN tunnel information, updated parameters for the accepted QoS flows. The message may also include a PDU session resource failed to modify list, with a PDU session ID and corresponding N2 SM information for each PDU session. The list may include zero, one or more PDU sessions. The corresponding N2 SM information includes the failure cause.

FIG. 7 shows a schematic diagram of an exemplary embodiment for performing network slice replacement during a RAN requested PDU session modification procedure in non-roaming and/or roaming with local break-out (LBO) scenario, including a portion or all of the following: a NG-RAN 782, an AMF 790, an SMF 792, and/or an UPF 794. This exemplary embodiment may realize network slice replacement during a PDU session modification procedure when the network slice is congested or unavailable at the NG-RAN, in which way the network slice service continuity is guaranteed for an impacted UEs, and thus, solves the problem/issue of poor network slice service continuity for the impacted UEs due to the NG-RAN initiating a PDU session release procedure for such PDU session when the PDU session is associated with network slice which is congested or unavailable at the NG-RAN.

Referring to step 7-1, for some or all PDU sessions established on a serving S-NSSAI, the NG-RAN may decide to replace the serving S-NSSAI with a new selected backup S-NSSAI, e.g. due to OAM reasons or the serving S-NSSAI is congested. The backup S-NSSAI is selected e.g. from the allowed NSSAI of the UE.

Referring to step 7-2, the NG-RAN may initiate a PDU session modification procedure by sending a N2 message, e.g. PDU SESSION RESOURCE MODIFY INDICATION message, to the AMF. The message includes a PDU session resource modify indication list, with the PDU session ID, the selected backup S-NSSAI and N2 SM information for each item in the list. The list may include one or more PDU sessions. The N2 SM information includes AN tunnel information. The N2 SM information may include the selected backup S-NSSAI.

Referring to step 7-3, the AMF may determine whether the PDU session (s) that requires slice replacement can be forwarded to the corresponding SMF. When the PDU session can be forwarded, e.g. the serving S-NSSAI and the backup S-NSSAI of the PDU session can be supported by the same SMF, the AMF forwards the N2 SM information and the backup S-NSSAI of the PDU session to the corresponding SMF. The AMF stores both the old S-NSSAI and the backup S-NSSAI associated with the same PDU session identity.

When the PDU session cannot be forwarded, e.g. the serving S-NSSAI and the backup S-NSSAI cannot be supported by the same SMF, the AMF informs the SMF to release such PDU session and include such PDU session in the PDU session resource failed to modify list returned to the NG-RAN.

Referring to step 7-4, the AMF sends a Nsmf_PDUSession_UpdateSMContext request message to the SMF. The message includes the N2 SM information and the backup S-NSSAI.

Referring to step 7-5, when the SMF receives the backup S-NSSAI for the PDU session and SMF decides to accept the replacement, the SMF triggers replacement of old S-NSSAI with the backup S-NSSAI for the PDU session. The SMF stores both the old S-NSSAI and the backup S-NSSAI associated with the same PDU session identity. When the SMF cannot accept the replacement, the SMF triggers the PDU session Release procedure.

Referring to step 7-6, the SMF sends a N4 session modification request message to the UPF. The message may include the backup S-NSSAI, the network instance (e.g. selected based on the backup S-NSSAI) , the updated rules such as packet detection rule (PDR) and QoS enhancement rule (QER) (e.g. taking the backup S-NSSAI into consideration) . The UPF may use the parameters, e.g. the backup S-NSSAI and the network instance, to determine internal UPF resources. Depending on the network deployment, the CN tunnel information of UPF used for the old S-NSSAI and the backup S-NSSAI may be different. In this case, the SMF may ask the UPF to allocate new CN tunnel information.

When the UPF cannot support both the old S-NSSAI and the backup S-NSSAI, a new UPF supporting both S-NSSAIs should be selected. When the new UPF is selected, the SMF sends a N4 session establishment request message to the UPF with the similar parameters.

Referring to step 7-7, the UPF returns an N4 session modification/establishment response message to the SMF with updated CN tunnel information when available.

Referring to step 7-8, the SMF sends an Nsmf_PDUSession_UpdateSMContext response message including N2 SM information to the AMF. For one or more accepted PDU session, the N2 SM information includes CN tunnel information, updated parameters for the accepted QoS flows, optionally updated QoS profile (s) (e.g. taking the backup S-NSSAI into consideration) . For one or more failed PDU session, the N2 SM information includes corresponding failure cause. When the SMF decides to accept the slice replacement from the old S-NSSAI to the backup S-NSSAI for the PDU session, such PDU session is considered as accepted PDU session. Otherwise, such PDU session is considered as failed PDU session.

Referring to step 7-9, the AMF sends a N2 message, e.g. PDU SESSION RESOURCE MODIFY CONFIRM message, to the NG-RAN. The message includes a PDU session resource modify confirm list, with a PDU session ID and corresponding N2 SM information for each PDU session. The list may include zero, one or more PDU sessions. The corresponding N2 SM information includes CN tunnel information, updated parameters for the accepted QoS flows, optionally updated QoS profile (s) . The message may also include a PDU session resource failed to modify list, with a PDU session ID and corresponding N2 SM information for each PDU session. The list may include zero, one or more PDU sessions. The corresponding N2 SM information includes the failure cause.

In some other embodiments, the above method may be performed under the situation of requesting network slice fallback for the PDU session. For example, the NG-RAN requires to replace the backup S-NSSAI with the old serving S-NSSAI by sending a network slice fallback indication to the AMF and the AMF forwards such indication to the SMF. When accepted, the SMF performs slice replacement of backup S-NSSAI with the old S-NSSAI for the PDU session. After successful slice fallback, the SMF removes the stored backup S-NSSAI for the PDU session. The SMF sends indication to the AMF which indicates the AMF to remove the stored backup S-NSSAI. The AMF removes the stored backup S-NSSAI for the PDU session.

FIG. 8 shows a schematic diagram of an exemplary embodiment for performing network slice replacement during a RAN requested PDU session modification procedure in home-routed (HR) roaming scenario, including a portion or all of the following: a NG-RAN 882, an AMF 890, a V-SMF 892, a V-UPF 894, a H-SMF 896, and/or a H-UPF 898.

Referring to step 8-1, for some or all PDU sessions established on the serving S-NSSAI, the NG-RAN may decide to replace the serving S-NSSAI with a new selected backup S-NSSAI, e.g. due to OAM reasons or the serving S-NSSAI is congested. The backup S-NSSAI is selected e.g. from a list of allowed NSSAIs of the UE.

Referring to step 8-2, the NG-RAN may initiate a PDU session modification procedure by sending a N2 message, e.g. PDU SESSION RESOURCE MODIFY INDICATION message, to the AMF. The message includes a PDU session resource modify indication list, with the PDU session ID, the selected backup S-NSSAI and N2 SM information for each item in the list. The list may include one or more PDU sessions. The N2 SM information includes AN tunnel information. The N2 SM information may include the selected backup S-NSSAI.

Referring to step 8-3, the AMF retrieves the mapped home public land mobile network (HPLMN) S-NSSAI of the backup S-NSSAI from the NSSF or based on local configuration. The AMF determines whether the PDU session (s) that requires slice replacement can be forwarded to the corresponding V-SMF and H-SMF. When the PDU session can be forwarded, e.g. the serving S-NSSAI and the backup S-NSSAI can be supported by the same V-SMF and, the mapped HPLMN S-NSSAI of the serving S-NSSAI and the mapped HPLMN S-NSSAI of the backup S-NSSAI can be supported by the same H-SMF, the AMF forwards the N2 SM information, the backup S-NSSAI and the mapped HPLMN S-NSSAI of the backup S-NSSAI to the corresponding V-SMF. The AMF stores the old S-NSSAI, the backup S-NSSAI, the mapped HPLMN S-NSSAI of the old S-NSSAI and the mapped HPLMN S-NSSAI of the backup S-NSSAI associated with the same PDU session identity.

When the PDU session cannot be forwarded, e.g. the serving S-NSSAI and the backup S-NSSAI cannot be supported by the same V-SMF and/or the mapped HPLMN S-NSSAI of the serving S-NSSAI and the mapped HPLMN S-NSSAI of the backup S-NSSAI cannot be supported by the same H-SMF, the AMF informs the V-SMF to release such PDU session and include such PDU session in the PDU session resource failed to modify list returned to the NG-RAN.

Referring to step 8-4, the AMF sends a Nsmf_PDUSession_UpdateSMContext request message to the V-SMF. The message includes the N2 SM information, the backup S-NSSAI and the mapped HPLMN S-NSSAI of the backup S-NSSAI.

Referring to step 8-5, when the V-SMF receives the backup S-NSSAI for the PDU session and V-SMF decides to accept replacement of the old S-NSSAI with the backup S-NSSAI, the V-SMF informs the H-SMF to update the PDU session. Otherwise the V-SMF informs the H-SMF to release such PDU session and include such PDU session in the PDU session resource failed to modify list returned to the NG-RAN.

Referring to step 8-6, the V-SMF sends a Nsmf_PDUSession_Update request message to the H-SMF. The message includes the N2 SM information and the mapped HPLMN S-NSSAI of the backup S-NSSAI.

Referring to step 8-7, when the H-SMF receives the mapped HPLMN S-NSSAI of the backup S-NSSAI and H-SMF decides to accept the replacement, the H-SMF triggers replacement of the mapped HPLMN S-NSSAI of the old S-NSSAI with the mapped HPLMN S-NSSAI of the backup S-NSSAI for the PDU session. The H-SMF stores both the mapped HPLMN S-NSSAI of the old S-NSSAI and the mapped HPLMN S-NSSAI of the backup S-NSSAI associated with the same PDU session identity. When the H-SMF cannot accept the replacement, the H-SMF includes such PDU session in the PDU session resource failed to modify list returned to the NG-RAN and triggers the PDU session release procedure.

Referring to step 8-8, the H-SMF sends a N4 session modification request message to the H-UPF. The message may include the mapped HPLMN S-NSSAI of the backup S-NSSAI, the network instance (e.g. selected based on the mapped HPLMN S-NSSAI of the backup S-NSSAI) , the updated rules such as packet detection rule (PDR) and QoS enhancement rule (QER) (e.g. taking the mapped HPLMN S-NSSAI of the backup S-NSSAI into consideration) . The H-UPF may use the parameters, e.g. the mapped HPLMN S-NSSAI of the backup S-NSSAI and the network instance, to determine internal H-UPF resources. Depending on the network deployment, the CN tunnel information of the H-UPF used for the mapped HPLMN S-NSSAI of the old S-NSSAI and the mapped HPLMN S-NSSAI of the backup S-NSSAI may be different. In this case, the H-SMF may ask the H-UPF to allocate new CN tunnel information.

When the H-UPF cannot support both the mapped HPLMN S-NSSAI of the old S-NSSAI and the mapped HPLMN S-NSSAI of the backup S-NSSAI, a new H-UPF supporting both S-NSSAIs should be selected. When the new H-UPF is selected, the H-SMF sends N4 session establishment request message to the H-UPF with the similar parameters.

Referring to step 8-9, the H-UPF returns an N4 session modification/establishment response message to the H-SMF with updated CN tunnel information when available.

Referring to step 8-10, the H-SMF sends a Nsmf_PDUSession_Update response message to the V-SMF. For one or more accepted PDU session, the message includes updated CN tunnel information, updated parameters for the accepted QoS flows, optionally updated QoS profile (s) (e.g. taking the mapped HPLMN S-NSSAI of the backup S-NSSAI into consideration) . For one or more failed PDU session, the message includes corresponding failure cause.

When the SMF decides to accept the slice replacement from the mapped HPLMN S-NSSAI of the old S-NSSAI to the mapped HPLMN S-NSSAI of the backup S-NSSAI for the PDU session, such PDU session is considered as an accepted PDU session. Otherwise, such PDU session is considered as a failed PDU session.

Referring to step 8-11, for one or more accepted PDU session, the V-SMF stores both the old S-NSSAI and the backup S-NSSAI associated with the same PDU session identity. The V-SMF triggers replacement of the old S-NSSAI with the backup S-NSSAI for the PDU session.

Referring to step 8-12, the V-SMF sends a N4 session modification request message to the V-UPF. The message may include the backup S-NSSAI, the network instance (e.g. selected based on the backup S-NSSAI) , the updated rules such as packet detection rule (PDR) and QoS enhancement rule (QER) (e.g. taking the backup S-NSSAI into consideration) . The V-UPF may use the parameters, e.g. the backup S-NSSAI and the network instance, to determine internal V-UPF resources. Depending on the network deployment, the CN tunnel information of V-UPF used for the old S-NSSAI and the backup S-NSSAI may be different. In this case, the V-SMF may ask the V-UPF to allocate new CN tunnel information.

When the V-UPF cannot support both the old S-NSSAI and the backup S-NSSAI, a new V-UPF supporting both S-NSSAIs should be selected. When the new V-UPF is selected, the V-SMF sends a N4 session establishment request message to the V-UPF with the similar parameters.

Referring to step 8-13, the V-UPF returns an N4 session modification/establishment response message to the V-SMF with updated CN tunnel information when available.

Referring to step 8-14, the SMF sends an Nsmf_PDUSession_UpdateSMContext response message including N2 SM information to the AMF. For one or more accepted PDU session, the N2 SM information includes updated CN tunnel information, updated parameters for the accepted QoS flows, optionally updated QoS profile (s) (e.g. taking the backup S-NSSAI into consideration) . For one or more failed PDU session, the N2 SM information includes corresponding failure cause.

Referring to step 8-15, the AMF sends a N2 message, e.g. PDU SESSION RESOURCE MODIFY CONFIRM message, to the NG-RAN. The message includes a PDU session resource modify confirm list, with a PDU session ID and corresponding N2 SM information for each PDU session. The list may include zero, one or more PDU sessions. The corresponding N2 SM information includes CN tunnel information, updated parameters for the accepted QoS flows, optionally updated QoS profile (s) . The message may optionally also include a PDU session resource failed to modify list, with PDU session ID and corresponding N2 SM information for each PDU session. The list may include zero, one or more PDU sessions. The corresponding N2 SM information includes the failure cause.

In some other embodiments, the above method may be performed under the situation of requesting network slice fallback for the PDU session. For example, the NG-RAN requires to replace the backup S-NSSAI with the old serving S-NSSAI by sending a network slice fallback indication to the AMF and the AMF forwards such indication to the SMF. When accepted, the SMF performs slice replacement of backup S-NSSAI with the old S-NSSAI for the PDU session. After successful slice fallback, the SMF removes the stored backup S-NSSAI for the PDU session. The SMF sends an indication to the AMF which indicates the AMF to remove the stored backup S-NSSAI. The AMF removes the stored backup S-NSSAI for the PDU session.

FIG. 9 shows a schematic diagram of an exemplary embodiment for performing UE initiated service request procedure to activate user plane (UP) connection for a PDU session, including a portion or all of the following: a UE 980, a NG-RAN 982, an AMF 990, an SMF 992, and/or an UPF 994. In some implementations, when a UE has established a PDU session with an S-NSSAI (e.g., an old S-NSSAI) and this S-NSSAI has been replaced by a back-up S-NSSAI, when the UE enters the CM-IDLE state or the user plane resource of such PDU session is released, both the old S-NSSAI and the backup S-NSSAI are stored in the PDU session context in the SMF. The various embodiments (e.g., this exemplary embodiment) may provide a mechanism for user plane re-activation for the PDU session associated with the old S-NSSAI and the back-up S-NSSAI.

Referring to step 9-1, the UE in connection management-idle (CM-IDLE) state or CM-connected state triggers Service request procedure to activate the user plane (UP) connection for PDU session (s) by sending service request message to the RAN. The service request message includes a list of PDU sessions to be activated.

Referring to step 9-2, the RAN forwards the service request message to the AMF.

Referring to step 9-3, the AMF determines the PDU session (s) for which the UP connection (s) may be activated and sends a Nsmf_PDUSession_UpdateSMContext request message to SMF (s) associated with the PDU session (s) with an operation type set to "UP activate" to indicate establishment of user plane resources for the PDU session (s) .

Referring to step 9-4, the SMF knows that the PDU session is associated with an old S-NSSAI as well as a backup S-NSSAI based on the PDU session context. The SMF requests CN tunnel information and sends a N4 session establishment/modification request message to the UPF. The message may include the backup S-NSSAI, the target network instance (e.g. selected based on the backup S-NSSAI) , the rules such as packet detection rule (PDR) and QoS enhancement rule (QER) (e.g. taking the backup S-NSSAI into consideration) .

Referring to step 9-5, the UPF may use the parameters, e.g. the backup S-NSSAI and the network instance, to determine internal UPF resources. The UPF sends a N4 session establishment/modification response message to the SMF. The UPF provides CN tunnel information to the SMF.

Referring to step 9-6, the SMF sends a Nsmf_PDUSession_UpdateSMContext response message including N2 SM information to the AMF. For a PDU session that the SMF has determined to accept the activation of UP connection, the N2 SM information includes PDU session ID, QoS profile (s) , CN N3 tunnel information, the old S-NSSAI, and/or the backup S-NSSAI.

Referring to step 9-7, the AMF forwards the N2 SM information received from SMF to the RAN.

Referring to step 9-8, the RAN performs radio resource control (RRC) connection reconfiguration with the UE depending on the QoS information for all the QoS flows of the PDU session (s) whose UP connections are activated.

Referring to step 9-9, when the RAN accepts the activation of UP connection for the PDU session on the backup S-NSSAI, the service request procedure may continue as described in other implementations/embodiments or per an existing procedure.

Otherwise when the RAN doesn’t accept the activation of UP connection for the PDU session on the backup S-NSSAI, instead of the RAN accepting the activation of UP connection for the PDU session on the old S-NSSAI, the RAN provides a fallback indication that the UP connection for the PDU session is activated on the old S-NSSAI or instead provides the old S-NSSAI, and associated AN tunnel information to the AMF.

Referring to step 9-10, the AMF sends a Nsmf_PDUSession_UpdateSMContext request message to the SMF. The message includes the indication or the old S-NSSAI, and the AN tunnel information received from the RAN.

Referring to step 9-11, when the SMF accepts the activation of UP connection for the PDU session on the old S-NSSAI, the SMF removes the stored backup S-NSSAI and sends a N4 session modification request message to the UPF. The message may include the AN tunnel information, the target network instance (e.g. selected based on the old S-NSSAI) , the rules such as packet detection rule (PDR) and QoS enhancement rule (QER) (e.g. taking the old S-NSSAI into consideration) .

Referring to step 9-12, the UPF sends a N4 session modification response message to the SMF. The message includes updated CN tunnel information.

Referring to step 9-13, the SMF sends a Nsmf_PDUSession_UpdateSMContext response message to the AMF with an indication indicating the AMF to remove the stored backup S-NSSAI. The AMF removes the stored backup S-NSSAI.

Referring to step 9-14, the SMF sends the N2 SM information including the updated CN tunnel information and the QoS profile (s) (when needed) for the PDU session to the RAN via the AMF.

The present disclosure describes methods, apparatus, and computer-readable medium for wireless communication. The present disclosure addressed the issues with performing network slice replacement during protocol data unit (PDU) session modification procedure or service request procedure. The methods, devices, and computer-readable medium described in the present disclosure may facilitate the performance of wireless communication by performing network slice replacement during protocol data unit (PDU) session modification procedure or service request procedure, thus improving efficiency and overall performance. The methods, devices, and computer-readable medium described in the present disclosure may improves the overall efficiency of the wireless communication systems.

Reference throughout this specification to features, advantages, or similar language does not imply that all of the features and advantages that may be realized with the present solution should be or are included in any single implementation thereof. Rather, language referring to the features and advantages is understood to mean that a specific feature, advantage, or characteristic described in connection with an embodiment is included in at least one embodiment of the present solution. Thus, discussions of the features and advantages, and similar language, throughout the specification may, but do not necessarily, refer to the same embodiment.

Furthermore, the described features, advantages and characteristics of the present solution may be combined in any suitable manner in one or more embodiments. One of ordinary skill in the relevant art will recognize, in light of the description herein, that the present solution can be practiced without one or more of the specific features or advantages of a particular embodiment. In other instances, additional features and advantages may be recognized in certain embodiments that may not be present in all embodiments of the present solution.

Claims

A method for wireless communication, comprising:

selecting, by a radio-access network (RAN) , a single-network slice selection assistant information (S-NSSAI) to replace a serving S-NSSAI for a protocol data unit (PDU) session; and

sending, by the RAN, a message including network slice replacement information for the PDU session to an access and mobility management function (AMF) .
The method according to claim 1, wherein:

the RAN selects, from network slice selection assistant information (NSSAI) , the S-NSSAI to replace the serving S-NSSAI associated with the PDU session, and

the message comprises the S-NSSAI.
The method according to claim 2, wherein:

the NSSAI comprises a list of S-NSSAIs that is allowed to use for a user equipment (UE) .
The method according to claim 2, further comprising:

receiving, by the RAN, an updated CN tunnel information or an updated QoS profile for the PDU session from the AMF.
The method according to claim 1, wherein:

in response to determining a network slice replacement fallback for the PDU session, the message comprises a fallback indication indicating to the AMF to replace the serving S-NSSAI with the S-NSSAI, the S-NSSAI corresponding to the PDU session when the PDU session is first established.
The method according to claim 1, wherein:

in response to the RAN receiving the S-NSSAI and the serving S-NSSAI for the PDU session and not accepting an activation of user plane (UP) connection for the PDU session on the serving S-NSSAI:

the RAN accepts the activation of user plane (UP) connection for the PDU session on the S-NSSAI, the S-NSSAI corresponding to the PDU session when the PDU session is first established; and

the message comprises one of the following:

a fallback indication indicating to the AMF the activation of UP connection for the PDU session on the S-NSSAI and corresponding access network (AN) tunnel information, or

the S-NSSAI and corresponding access network (AN) tunnel information.
A method for wireless communication, comprising:

receiving, by an access and mobility management function (AMF) , a message for network slice replacement for a protocol data unit (PDU) session from a radio-access network (RAN) ; and

determining, by the AMF, whether to accept the PDU session that requires slice replacement with a corresponding single-network slice selection assistant information (S-NSSAI) based on the message.
The method according to claim 7, wherein:

the message comprises a first S-NSSAI;

the AMF determines whether to accept the PDU session that requires slice replacement with the first S-NSSAI; and

in response to determining to accept the PDU session with the first S-NSSAI, the AMF sends the first S-NSSAI corresponding to the PDU session to a corresponding session management function (SMF) .
The method according to claim 8, wherein:

the first S-NSSAI is configured to replace a second S-NSSAI, the second S-NSSAI corresponding to the PDU session that require slice replacement when the PDU session is first established.
The method according to claim 9, wherein the determining whether to accept the PDU session that requires slice replacement with the first S-NSSAI comprises:

determining, by the AMF, whether the first S-NSSAI and the second S-NSSAI are supported by a same SMF;

in response to determining that the first S-NSSAI and the second S-NSSAI are supported by the same SMF, determining, by the AMF, to accept the PDU session; and

in response to determining that the first S-NSSAI and the second S-NSSAI are not supported by the same SMF, determining, by the AMF, not to accept the PDU session.
The method according to claim 10, further comprising:

in response to determining to accept the PDU session:

sending, by the AMF, corresponding N2 SM information and the first S-NSSAI to the corresponding SMF, and

storing, by the AMF, the first S-NSSAI and the second S-NSSAI corresponding to a same PDU session identity.
The method according to claim 7, wherein:

the message comprises a network slice replacement fallback indication indicating to the AMF to replace a first S-NSSAI with a second S-NSSAI for the PDU session, the second S-NSSAI corresponding to the PDU session when the PDU session is first established; and

the AMF sends the network slice replacement fallback indication for the PDU session to a corresponding SMF.
The method according to claim 7, wherein:

the message comprises a second S-NSSAI, the second S-NSSAI corresponding to the PDU session when the PDU session is first established; and

the AMF sends the message to a corresponding SMF, the message comprising the second S-NSSAI for the PDU session.
A method for wireless communication, comprising:

receiving, by a session management function (SMF) , a first single-network slice selection assistant information (S-NSSAI) corresponding to a protocol data unit (PDU) session that requires slice replacement from an access and mobility management function (AMF) ;

determining, by the SMF, whether to accept the PDU session with the first S-NSSAI;

in response to determining to accept the PDU session:

triggering, by the SMF, replacement of a second S-NSSAI with the first S-NSSAI for the PDU session, and

storing, by the SMF, the S-NSSAI and the second S-NSSAI associated with a same PDU session identity;

in response to determining not to accept the PDU session:

triggering, by the SMF, a PDU session release procedure; and

sending, by the SMF, a N4 message to a user plan function (UPF) , the N4 message comprising at least one of the following: the first S-NSSAI, a network instance, or an updated rule.
A method for wireless communication, comprising:

receiving, by a session management function (SMF) , a network slice replacement fallback indication from an access and mobility management function (AMF) , the fallback indication indicating to replace a first single-network slice selection assistant information (S-NSSAI) with a second S-NSSAI for the associated PDU session, the second S-NSSAI corresponding to a PDU session when the PDU session is first established;

determining, by the SMF, whether to accept the network slice replacement for the PDU session with the second S-NSSAI;

in response to determining to accept the network slice replacement with the second S-NSSAI:

removing, by the SMF, the first S-NSSAI associated with the PDU session that is stored by the SMF, and

sending, by the SMF, a N4 message to a user plan function (UPF) , the N4 message comprising at least one of the following: the second S-NSSAI, access network (AN) tunnel information, a network instance, or an updated rule.
The method according to any of claims 14 and 15, wherein:

the SMF provides the first S-NSSAI and the second S-NSSAI to the RAN.
The method according to any of claims 14, 15, and 16, wherein:

the SMF sends an updated core network (CN) tunnel information and an updated quality of service (QoS) profile to the RAN.
A method for wireless communication, comprising:

receiving, by a user plan function (UPF) , a request message from a session management function (SMF) , the request message comprising at least one of the following: a single-network slice selection assistant information (S-NSSAI) corresponding to a protocol data unit (PDU) session that requires slice replacement, a network instance, or an updated rule; and

sending, by the UPF, a response message to the SMF, the response message comprising a core network (CN) tunnel information.
The method according to claim 18, further comprising:

determining, by the UPF, internal UPF resources based on the S-NSSAI or the network instance; and

allocating, by the UPF, the CN tunnel information based on the request message from the SMF.
A wireless communications apparatus comprising a processor and a memory, wherein the processor is configured to read code from the memory and implement a method recited in any of claims 1 to 19.
A computer program product comprising a computer-readable program medium code stored thereupon, the computer-readable program medium code, when executed by a processor, causing the processor to implement a method recited in any of claims 1 to 19.