Techniques for changing network slices of protocol data unit sessions

Abstract

Various aspects of the present disclosure relate to changing a network slice of a protocol data unit (PDU) session. A device receives, from a user equipment (UE), first signaling as a registration request to register with a first network slice, and the device transmits second signaling indicating acceptance of the registration and allowing the UE to register with an alternate network slice. The UE transmits the first signaling to request registration with the first network slice and receives the second signaling indicating registration with the first network slice and allowing registration with the alternative network slice. The UE transmits a third signaling to establish a first PDU session on the first network slice.

Description

Technical Field

[0001] The present disclosure relates to wireless communications, and more particularly, to changing (e.g., switching, updating, modifying) network slices. Background Art

[0002] A wireless communication system may include one or more network communication devices, such as a base station, which may be further referred to as an eNodeB (eNB), a next generation NodeB (gNB), or other suitable terms. Each network communication device (such as a base station) may support wireless communication of one or more user communication devices (which may be further referred to as user equipment (UE) or other suitable terms). A wireless communication system may support wireless communication with one or more user communication devices by utilizing resources of the wireless communication system (such as time resources (such as symbols, time slots, subframes, frames, or the like) or frequency resources (such as subcarriers, carriers). In addition, a wireless communication system may support wireless communication across various radio access technologies, including third generation (3G) radio access technologies, fourth generation (4G) radio access technologies, fifth generation (5G) radio access technologies, and other suitable radio access technologies above 5G (such as sixth generation (6G)).

[0003] Network slicing enables network operators to divide the network into granular "slices" to provide customized network connections or features for customer devices and / or external service providers. A network slice is a logical network with a set of network functions and corresponding resources (e.g., computing, storage, networking) to provide specific network capabilities and network characteristics. A network slice may include core network control plane and user plane network functions and an access network (e.g., a 5G radio access network or a fixed access network). A UE may be configured with network slicing related information, which is Network Slice Selection Assistance Information (NSSAI), which may include a single or multiple S-NSSAIs (single NSSAI). Summary of the invention

[0004] The present disclosure relates to methods, devices, and systems that support techniques for changing the network slice of a protocol data unit (PDU) session. By utilizing the described techniques, a network entity determines an alternative network slice (e.g., a second network slice S-NSSAI-2) of a first network slice (e.g., S-NSSAI-1) in a network and correspondingly configures a UE to use the alternative network slice S-NSSAI (e.g., S-NSSAI-2) for PDU session establishment. In an implementation scheme, the network entity that determines the alternative network slice is one or more of an access and mobility management function (AMF), a network slice selection function (NSSF), and / or a policy control function (PCF).

[0005] Aspects of the present disclosure relate to an AMF that indicates to a UE during a registration procedure whether the network supports an alternative slice (S-NSSAI) feature and / or whether the UE is allowed to request an alternative S-NSSAI. The AMF may also indicate to a session management function (SMF) that a PDU session will be established on an alternative S-NSSAI. The SMF sends a PDU Session Release (or Modify) message (including a new 5GSM cause value) to the UE to indicate to the UE that re-establishment on an alternative S-NSSAI is desired. If (a) there is no routing descriptor (RSD) with an S-NSSAI different from S-NSSAI-1 or (b) an S-NSSAI from another RSD is in a rejected NSSAI, the UE sends a registration request for an unknown network slice that is desired to be an alternative to the subscribed S-NSSAI (e.g., an alternative to S-NSSAI-1, where the alternative network slice is assumed to be S-NSSAI-2).

[0006] By performing aspects of the described techniques for changing the network slice of a PDU session, the UE determines or finds an alternative S-NSSAI based on one or more UE routing policy (URSP) rules. If no alternative S-NSSAI is available in the URSP rules, then after the UE requests an alternative S-NSSAI from the AMF, a new S-NSSAI is determined in the AMF. In addition, the AMF is able to notify the UE about the need to establish a PDU session on an alternative (or compatible) S-NSSAI without engaging the session management (SM) (sub) layer. If it is determined that an alternative network slice S-NSSAI can be used to establish a PDU session for the UE, then the alternative network slice S-NSSAI is compatible.

[0007] In some implementations of the methods and apparatus described herein, the UE transmits first signaling to request registration with a first network slice and receives second signaling indicating registration with the first network slice and allowing registration with an alternative network slice. The UE transmits third signaling to establish a first PDU session on the first network slice.

[0008] Some embodiments of the methods and devices described herein may further include the UE identifying that the alternative network slice does not exist in the configured network slice selection assistance information (NSSAI). The UE transmits a fourth signaling indicating that the UE supports the ability to register with the alternative network slice. The UE receives a fourth signaling indicating that the first PDU session is reestablished on the alternative network slice based at least in part on the unavailability of the first network slice and transmits a fifth signaling to request registration with the alternative network slice based on the inability to identify the alternative network slice. The UE receives a sixth signaling indicating that the registration is accepted and that the configured NSSAI includes an identification of the alternative network slice, the alternative network slice is mapped to the first network slice, and initiates establishment of a second PDU session on the alternative network slice, the second PDU session using the same routing descriptor as the first PDU session based on the alternative network slice mapped to the first network slice. The UE transmits the fifth signaling to request registration with the alternative network slice based on determining that there is no identified alternative network slice for reestablishing the first PDU session.

[0009] In some implementations of the methods and apparatus described herein, the AMF (or a network device implementing the AMF) receives first signaling from a UE as a registration request to register with a first network slice, and transmits second signaling indicating acceptance of the registration and allowing the UE to register with an alternative network slice.

[0010] Some embodiments of the methods and apparatus described herein may further include the AMF identifying that the alternative network slice does not exist in the configured NSSAI. The AMF receives a third signaling from the UE indicating that the UE supports the ability to register with the alternative network slice. The AMF transmits a third signaling to a network function serving a first PDU session established on the first network slice, the third signaling including an indication that the first PDU session can be established on the alternative network slice. The AMF receives a third signaling from the UE as an additional registration request to register with the alternative network slice based on the UE's inability to identify the alternative network slice in response to having signaled the UE to reestablish the first PDU session. The AMF transmits a fourth signaling to the UE indicating that the registration is accepted and that the configured NSSAI includes an identification of the alternative network slice, the alternative network slice being mapped to the first network slice, and receives a fifth signaling indicating that the UE has established a second PDU session using the same routing descriptor as the first PDU session based on the alternative network slice mapped to the first network slice. If the UE is not roaming, the alternative network slice is mapped to the first network slice based on the NSSAI. If the UE is roaming, the alternative network slice is mapped to the first network slice based on a Home Public Land Mobile Network (HPLMN) NSSAI. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 An example of a wireless communication system that supports techniques for changing network slicing of a PDU session according to aspects of the present disclosure is described.

[0012] Figure 2 An exemplary 5GS architecture of a UE associated with two network slices according to aspects of the present disclosure is illustrated, which supports techniques for changing the network slice of a PDU session.

[0013] Figure 3 An example of a signaling flow chart for a UE to (re)establish a current PDU session from a first network slice to an alternative second network slice according to aspects of the present disclosure is illustrated, which supports techniques for changing the network slice of a PDU session.

[0014] Figure 4 An example of a signaling flow diagram for a UE establishing a new PDU session on a first unavailable network slice when the AMF determines to use an alternative second network slice is illustrated, which supports techniques for changing the network slice of a PDU session according to aspects of the present disclosure.

[0015] Figure 5 and 6An example of a block diagram of an apparatus that supports techniques for changing network slices for a PDU session according to aspects of the present disclosure is illustrated.

[0016] Figures 7 to 10 A flowchart illustrating a method of supporting techniques for changing network slices for a PDU session according to aspects of the present disclosure. DETAILED DESCRIPTION

[0017] Network operators can divide the network into network slices to provide customized network connectivity or features for customer devices and / or external service providers. A network slice is a logical network with a set of network functions and corresponding resources (e.g., computing, storage, networking) to provide specific network capabilities and network characteristics. A network slice may include core network control plane and user plane network functions and access networks. A UE may be configured with network slice related information (NSSAI), which may include a single or multiple S-NSSAIs (single NSSAI).

[0018] The network slice used by the UE may be changed to another network slice (e.g., slice remapping), for example, during UE mobility due to lack of support for the first network slice in the target cell or due to resource limitations of the first network slice in the target radio access network (RAN) node. However, a disadvantage of conventional techniques is that slice remapping is performed transparently to the UE non-access stratum (NAS) layer or even transparently to the UE access stratum (AS) layer. Slice remapping is performed in the RAN side without changing the UE NAS layer or the 5G core network (5GCN or 5GC). However, the change of network slice will change the UE because the UE needs to be reconfigured with respect to the alternative network slice exchanged with the first network slice. Another conventional technique suggests that the SMF transmits the alternative network slice to the UE in NAS session management (SM) signaling. However, this does not take into account how the UE will handle the alternative network slice for a different PDU session on the previous network slice.

[0019] In aspects of the described techniques for changing the network slice of a PDU session, a network entity (e.g., AMF) determines an alternative network slice (S-NSSAI-2) for a first network slice (e.g., S-NSSAI-1) and correspondingly configures the UE to use the alternative S-NSSAI (e.g., S-NSSAI-2) for PDU session establishment. Aspects of the present disclosure relate to the AMF indicating to the UE during a registration procedure whether the network supports alternative network slice features and / or whether the UE is allowed to request an alternative network slice. The AMF may also indicate to the SMF that the PDU session is established on the alternative network slice. The SMF sends a PDU session release (or modification) message (including a new 5GSM cause value) to the UE to indicate to the UE that re-establishment on the alternative network slice is desired. If there is no RSD with a network slice different from the first network slice in use or (b) a network slice from another RSD is in the rejected NSSAI, then the UE sends a registration request for an unknown network slice, which is desired to be a replacement for the subscribed network slice (e.g., a replacement for the first network slice, where the replacement network slice is assumed to be the second network slice).

[0020] By performing aspects of the described techniques for changing the network slice of a PDU session, the UE determines or discovers an alternative S-NSSAI according to one or more URSP rules. If no alternative S-NSSAI is available in the URSP rules, then after the UE requests an alternative S-NSSAI from the AMF, a new S-NSSAI is determined in the AMF. In addition, the AMF is able to notify the UE about the need to establish a PDU session on an alternative S-NSSAI without engaging the session management (SM) (sub) layer.

[0021] Aspects of the present disclosure are described in the context of a wireless communication system. Aspects of the present disclosure are further illustrated and described with reference to apparatus diagrams and flow charts.

[0022] Figure 1An example of a wireless communication system 100 that supports techniques for changing network slices for PDU sessions according to aspects of the present disclosure is illustrated. The wireless communication system 100 may include one or more network entities 102, one or more UEs 104, a core network 106, and a packet data network 108. The wireless communication system 100 may support various radio access technologies. In some implementations, the wireless communication system 100 may be a 4G network, such as an LTE network or an LTE Advanced (LTE-A) network. In some other implementations, the wireless communication system 100 may be a 5G network, such as an NR network. In other implementations, the wireless communication system 100 may be a combination of a 4G network and a 5G network or other suitable radio access technologies, including Institute of Electrical and Electronics Engineers (IEEE) 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20. The wireless communication system 100 may support radio access technologies above 5G. In addition, the wireless communication system 100 may support technologies such as time division multiple access (TDMA), frequency division multiple access (FDMA), or code division multiple access (CDMA).

[0023] One or more network entities 102 may be dispersed throughout a geographic region to form a wireless communication system 100. One or more of the network entities 102 described herein may be or include or may be referred to as a network node, a base station, a network element, a RAN, a base transceiver station, an access point, a NodeB, an eNodeB (eNB), a next generation NodeB (gNB), or other suitable terms. The network entity 102 and the UE 104 may communicate via a communication link 110 (which may be a wireless or wired connection). For example, the network entity 102 and the UE 104 may perform wireless communication (e.g., receive signaling, transmit signaling) via a Uu interface.

[0024] The network entity 102 may provide a geographic coverage area 112, wherein the network entity 102 may support services (such as voice, video, packet data, message transceiving, broadcast, etc.) for one or more UEs 104 within the geographic coverage area 112. For example, the network entity 102 and UE 104 may support wireless communications of signals related to services (such as voice, video, packet data, message transceiving, broadcast, etc.) according to one or more radio access technologies. In some implementations, the network entity 102 may be movable, such as a satellite associated with a non-terrestrial network. In some implementations, different geographic coverage areas 112 associated with the same or different radio access technologies may overlap, but different geographic coverage areas 112 may be associated with different network entities 102. Information and signals described herein may be represented using any of a variety of different techniques and technologies. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referenced in the entire description may be represented by voltage, current, electromagnetic waves, magnetic fields or magnetic particles, light fields or optical particles, or any combination thereof.

[0025] One or more UEs 104 may be dispersed throughout the geographic area of ​​the wireless communication system 100. UE 104 may include or may be referred to as a mobile device, a wireless device, a remote device, a remote unit, a handheld device, or a subscriber device or some other suitable terminology. In some implementations, UE 104 may be referred to as a unit, a station, a terminal, or a client and other examples. Additionally or alternatively, UE 104 may be referred to as an Internet of Things (IoT) device, an Internet of Everything (IoE) device, or a Machine Type Communication (MTC) device and other examples. In some implementations, UE 104 may be fixed in the wireless communication system 100. In some other implementations, UE 104 may be mobile in the wireless communication system 100.

[0026] One or more UEs 104 may be devices in different forms or with different capabilities. Figure 1 1. Some examples of UE 104 are illustrated in FIG. UE 104 may be capable of communicating with various types of devices, such as network entity 102, other UEs 104, or network equipment (e.g., core network 106, packet data network 108, relay device, integrated access and backhaul (IAB) node, or another network equipment), such as Figure 1 Additionally or alternatively, UE 104 can support communications with other network entities 102 or UE 104 that can act as relays in wireless communication system 100.

[0027] The UE 104 may also be capable of supporting wireless communication directly with other UEs 104 via a communication link 114. For example, the UE 104 may support wireless communication directly with another UE 104 via a device-to-device (D2D) communication link. In some embodiments (e.g., vehicle-to-vehicle (V2V) deployments, vehicle-to-everything (V2X) deployments, or cellular V2X deployments), the communication link 114 may be referred to as a sidelink. For example, the UE 104 may support wireless communication directly with another UE 104 via a PC5 interface.

[0028] The network entity 102 may support communication with the core network 106 or another network entity 102 or both. For example, the network entity 102 may interface with the core network 106 via one or more backhaul links 116 (e.g., via S1, N2, or another network interface). The network entities 102 may communicate with each other via the backhaul links 116 (e.g., via X2, Xn, or another network interface). In some implementations, the network entities 102 may communicate with each other directly (e.g., between the network entities 102). In some other implementations, the network entities 102 may communicate with each other or indirectly (e.g., via the core network 106). In some implementations, one or more network entities 102 may include subcomponents, such as access network entities, which may be instances of access node controllers (ANCs). The ANC may communicate with one or more UEs 104 via one or more other access network transmission entities (which may be referred to as radio heads, smart radio heads, or transmit-receive points (TRPs)).

[0029] In some implementations, the network entity 102 may be configured as a disaggregated architecture, which may be configured to utilize a protocol stack that is physically or logically distributed between two or more network entities 102, such as an integrated access backhaul (IAB) network, an open RAN (O-RAN) (e.g., a network configuration sponsored by the O-RAN Alliance), or a virtualized RAN (vRAN) (e.g., a cloud RAN (C-RAN). For example, the network entity 102 may include one or more of a central unit (CU), a distributed unit (DU), a radio unit (RU), a RAN intelligent controller (RIC) (e.g., a near real-time RIC (near-RT RIC), a non-real-time RIC (non-RT RIC)), a service management and orchestration (SMO) system, or any combination thereof.

[0030] A RU may also be referred to as a radio head, a smart radio head, a remote radio head (RRH), a remote radio unit (RRU), or a transmit receive point (TRP). One or more components of the network entity 102 in the decomposed RAN architecture may be co-located, or one or more components of the network entity 102 may be located in distributed locations (e.g., separate physical locations). In some implementations, one or more network entities 102 of the decomposed RAN architecture may be implemented as virtual units (e.g., virtual CU (VCU), virtual DU (VDU), virtual RU (VRU)).

[0031] The functional division between CU, DU and RU can be flexible and can support different functions, depending on which functions (e.g., network layer functions, protocol layer functions, baseband functions, radio frequency functions, and any combination thereof) are performed at the CU, DU or RU. For example, a functional division of the protocol stack can be adopted between the CU and the DU, so that the CU can support one or more layers of the protocol stack and the DU can support one or more different layers of the protocol stack. In some implementations, the CU can host upper protocol layer (e.g., layer 3 (L3), layer 2 (L2)) functions and signaling (e.g., radio resource control (RRC), service data adaptation protocol (SDAP), packet data convergence protocol (PDCP)). The CU can be connected to one or more DUs or RUs and one or more DUs or RUs can host lower protocol layers, such as layer 1 (L1) (e.g., physical (PHY) layer) or L2 (e.g., radio link control (RLC) layer, medium access control (MAC) layer) functions and signaling and can each be at least partially controlled by the CU.

[0032] Additionally or alternatively, a functional division of the protocol stack may be employed between the DU and the RU, such that the DU may support one or more layers of the protocol stack and the RU may support one or more different layers of the protocol stack. The DU may support one or more different cells (e.g., via one or more RUs). In some implementations, the functional division between the CU and the DU or between the DU and the RU may be within the protocol layer (e.g., some functions of the protocol layer may be performed by one of the CU, DU, or RU, while other functions of the protocol layer are performed by different ones of the CU, DU, or RU).

[0033] The functions of the CU may be further divided into CU control plane (CU-CP) and CU user plane (CU-UP) functions. The CU may be connected to one or more DUs via midhaul communication links (e.g., F1, F1-c, F1-u), and the DU may be connected to one or more RUs via fronthaul communication links (e.g., open fronthaul (FH) interfaces). In some implementations, the midhaul communication links or fronthaul communication links may be implemented according to interfaces (e.g., channels) between layers of a protocol stack supported by the respective network entities 102 communicating via such communication links.

[0034] The core network 106 may support user authentication, access authentication, tracking, connection, and other access, routing, or mobility functions. The core network 106 may be an evolved packet core (EPC) or a 5G core (5GC), which may include control plane entities that manage access and mobility (e.g., a mobile management entity (MME), an access and mobility management function (AMF)) and user plane entities that route packets or interconnect to external networks (e.g., a serving gateway (S-GW), a packet data network (PDN) gateway (P-GW), or a user plane function (UPF)). In some implementations, the control plane entity may manage NAS functions of one or more UEs 104 served by one or more network entities 102 associated with the core network 106, such as mobility, authentication, and bearer management (e.g., data bearer, signal bearer, etc.).

[0035] The core network 106 may communicate with the packet data network 108 via one or more backhaul links 116 (e.g., via S1, N2, or another network interface). The packet data network 108 may include an application server 118. In some implementations, one or more UEs 104 may communicate with the application server 118. The UE 104 may establish a session (e.g., a protocol data unit (PDU) session or the like) with the core network 106 via the network entity 102. The core network 106 may route traffic (e.g., control information, data, and the like) between the UE 104 and the application server 118 using the established session (e.g., the established PDU session). A PDU session may be an example of a logical connection between a UE 104 and the core network 106 (e.g., one or more network functions of the core network 106).

[0036] In the wireless communication system 100, the network entity 102 and the UE 104 may use the resources of the wireless communication system 100 (e.g., time resources (e.g., symbols, time slots, subframes, frames, or the like) or frequency resources (e.g., subcarriers, carriers)) to perform various operations (e.g., wireless communication). In some implementations, the network entity 102 and the UE 104 may support different resource structures. For example, the network entity 102 and the UE 104 may support different frame structures. In some implementations, in, for example, 4G, the network entity 102 and the UE 104 may support a single frame structure. In some other implementations, in, for example, 5G and other suitable radio access technologies, the network entity 102 and the UE 104 may support various frame structures (i.e., multi-frame structures). The network entity 102 and the UE 104 may support various frame structures based on one or more parameter sets (numerology).

[0037] One or more parameter sets may be supported in the wireless communication system 100, and the parameter sets may include subcarrier spacing and cyclic prefixes. A first parameter set (e.g., μ=0) may be associated with a first subcarrier spacing (e.g., 15 kHz) and a normal cyclic prefix. A first parameter set (e.g., μ=0) associated with a first subcarrier spacing (e.g., 15 kHz) may utilize one slot per subframe. A second parameter set (e.g., μ=1) may be associated with a second subcarrier spacing (e.g., 30 kHz) and a normal cyclic prefix. A third parameter set (e.g., μ=2) may be associated with a third subcarrier spacing (e.g., 60 kHz) and a normal cyclic prefix or an extended cyclic prefix. A fourth parameter set (e.g., μ=3) may be associated with a fourth subcarrier spacing (e.g., 120 kHz) and a normal cyclic prefix. A fifth parameter set (e.g., μ=4) may be associated with a fifth subcarrier spacing (e.g., 240 kHz) and a normal cyclic prefix.

[0038] The time intervals of resources (e.g., communication resources) may be organized according to frames (also referred to as radio frames). Each frame may have a duration, such as a 10 millisecond (ms) duration. In some embodiments, each frame may include a plurality of subframes. For example, each frame may include 10 subframes, and each subframe may have a duration, such as a 1 ms duration. In some embodiments, each frame may have the same duration. In some embodiments, each subframe of a frame may have the same duration.

[0039] Additionally or alternatively, the time intervals of resources (e.g., communication resources) may be organized according to time slots. For example, a subframe may include a certain number (e.g., number) of time slots. Each time slot may include a certain number (e.g., number) of symbols (e.g., orthogonal frequency division multiplexing (OFDM) symbols). In some embodiments, the number (e.g., number) of time slots of a subframe may depend on a parameter set. For a normal cyclic prefix, a time slot may include 14 symbols. For an extended cyclic prefix (e.g., applicable to a 60kHz subcarrier spacing), a time slot may include 12 symbols. The relationship between the number of symbols per time slot, the number of time slots per subframe, and the number of time slots per frame of a normal cyclic prefix and an extended cyclic prefix may depend on a parameter set. It should be understood that references to a first parameter set (e.g., μ=0) associated with a first subcarrier spacing (e.g., 15kHz) may be used interchangeably between subframes and time slots.

[0040] In the wireless communication system 100, the electromagnetic (EM) spectrum may be divided into various categories, bands, channels, etc. based on frequency or wavelength. For example, the wireless communication system 100 may support one or more operating bands, such as the frequency range designations FR1 (410 MHz to 7.125 GHz), FR2 (24.25 GHz to 52.6 GHz), FR3 (7.125 GHz to 24.25 GHz), FR4 (52.6 GHz to 114.25 GHz), FR4a or FR4-1 (52.6 GHz to 71 GHz), and FR5 (114.25 GHz to 300 GHz). In some implementations, the network entity 102 and the UE 104 may perform wireless communications on one or more of the operating bands. In some implementations, FR1 may be used by the network entity 102 and the UE 104 as well as other equipment or devices for cellular communication traffic (e.g., control information, data). In some implementations, FR2 may be used by the network entity 102 and the UE 104 and other equipment or devices for short-range high data rate capabilities.

[0041] FR1 may be associated with one or more parameter sets (e.g., at least three parameter sets). For example, FR1 may be associated with a first parameter set (e.g., μ=0) including 15kHz subcarrier spacing, a second parameter set (e.g., μ=1) including 30kHz subcarrier spacing, and a third parameter set (e.g., μ=2) including 60kHz subcarrier spacing. FR2 may be associated with one or more parameter sets (e.g., at least 2 parameter sets). For example, FR2 may be associated with a third parameter set (e.g., μ=2) including 60kHz subcarrier spacing, and a fourth parameter set (e.g., μ=3) including 120kHz subcarrier spacing.

[0042] According to an implementation, one or more of the network entity 102 (including the access network), the UE 104, the AMF 120, and / or the SMF may be operable to implement various aspects of the techniques described herein for changing the network slice of a PDU session. For example, the UE 104 transmits a registration request 122 to register with a first network slice, and the AMF 120 (or a network device implementing the AMF) receives the registration request 122 from the UE 104 (via the network entity 102) to register with the first network slice. The AMF 120 transmits a registration acceptance response 124 to the UE 104, indicating that the registration is accepted and that the UE is allowed to register with the alternative network slice. The UE 104 receives the registration acceptance response 124 and the indication that registration with the alternative network slice is allowed. The UE 104 then transmits to establish a PDU session 126 on the first network slice, which is received by the AMF 120.

[0043] In general, the UE requests registration with a network slice by transmitting a NAS Registration Request message including a requested NSSAI (which contains a list of one or more S-NSSAIs that the UE wants to register with) to the 5GC (e.g., AMF). In a Registration Accept message or a UE Configuration Update Command message, the AMF transmits one or more elements related to the UE's network slice configuration to the UE, such as Allowed NSSAI, Configured NSSAI, Rejected NSSAI, or Pending NSSAI. NSSAI is a list of one or more S-NSSAIs.

[0044] Figure 2 An exemplary 5GS architecture 200 of a UE associated with two network slices is illustrated, which supports techniques for changing network slices for a PDU session in accordance with aspects of the present disclosure. The UE is associated with two network slices deployed on a first network slice instance (e.g., "NSI-1" depicted in solid lines) and a second network slice instance ("NSI-2" depicted in dashed lines), respectively. According to this exemplary architecture 200, a (radio) access network ((R)AN) is part of and shared by both network slices. The core network of the network slice (or NSI) has a common control plane network function (CCNF) and dedicated CN network functions, such as SMF1, user plane function (UPF) 1, and other network functions (NFs) belonging to NSI-1 and SMF2, UPF2, and other NFs belonging to NSI-2. It should be noted that the exemplary 5GS architecture 200 does not show or include all network functions (e.g., AMF, NSSF, SMF, UPF, etc.) or all reference points.

[0045] Due to lack of support for network slicing or resource limitations of network slices in the target RAN node, support for network slice service continuity during UE mobility is considered. These scenarios may occur due to the network slice not being required to be available in all Tracking Areas (TAs) of the network. In aspects of the present disclosure, non-mobile scenarios (or events) and mobile scenarios (or events) in the network are considered, which result in changes in network slices. For non-mobile scenarios, a) the network slice (or network slice instance) is overloaded or undergoes planned maintenance in the CN (e.g., network slice termination) and / or b) the network performance of the network slice cannot meet the service level agreement (SLA) agreed with the network slice customer, and therefore the UE should use an alternative network slice to meet the SLA. Mobile scenarios are considered, particularly in the case where a network slice (or network slice instance) moves between registration areas (RAs) that are overloaded in the target CN.

[0046] Aspects of the present disclosure consider whether the current network slice (or network slice instance) can serve the PDU session or whether the current network slice instance can meet the performance requirements of the application. If it is possible that the alternative S-NSSAI is not part of the S-NSSAI to which the UE subscribes (stored in the UE context in the AMF), then the alternative S-NSSAI is also not part of the NSSAI and URSP rules configured by the UE. The UE cannot request registration with the alternative S-NSSAI. Aspects of the present disclosure consider allowing the UE to register with an alternative S-NSSAI that is not part of the NSSAI configured by the UE. In addition, aspects of the present disclosure consider how to ensure that the alternative S-NSSAI (e.g., S-NSSAI-2) is compatible with the UE network slice configuration and routing policy (e.g., NSSP / URSP, configured NSSAI and / or allowed NSSAI).

[0047] When the network slice used by the UE is changed to another network slice, for example during UE mobility due to lack of support for the first network slice in the target cell or resource limitations of the first network slice in the target RAN node, this network slice change is called slice remapping. However, a disadvantage of conventional techniques is that slice remapping is performed transparently to the UE NAS layer or even transparently to the UE AS layer. In other words, slice remapping is performed in the RAN side without changing the UE NAS layer or the 5G core network (5GCN or 5GC). However, in the above scenario, the change of network slice will change the UE and 5GC because the UE needs to be reconfigured with respect to the alternative network slice exchanged with the first network slice. Another conventional technique suggests that the SMF transmits the alternative S-NSSAI to the UE in NAS SM signaling. However, this does not take into account how the UE will handle the alternative S-NSSAI for different PDU sessions on the previous S-NSSAI (e.g., S-NSSAI-1).

[0048] In aspects of the technique for changing the network slice of a PDU session, the network operator allows the data traffic of an application to be routed on more than a single network slice, and these more than one network slices are part of the S-NSSAI to which the UE subscribes. It is assumed that the network should have configured the URSP rules in the UE and that the application data traffic uses one or more RSDs each containing a different S-NSSAI. If a new PDU session is to be set up or if a current PDU session is to be reestablished, the UE is prompted to use an RSD different from the currently used RSD.

[0049] An example of UE subscription data and configuration for two network slices is:

[0050] UE subscription data :

[0051] -S-NSSAI-1 (default) (eMBB)

[0052] -S-NSSAI-2(eMBB)

[0053] URSP Rules :

[0054] -Business descriptor of App1:

[0055] =RSD#1: S-NSSAI-1, DNN-1;

[0056] =RSD#2: S-NSSAI-2, DNN-1;

[0057] The UE subscribes to S-NSSAI-1 and S-NSSAI-2, and when the UE registers with the network, the UE subscription data is stored in the unified data management (UDM) and the serving AMF. The network (e.g., PCF) configures a set of URSP rules for the UE, such as shown in the example of URSP rules for data services of application App1. This example URSP rule includes two RSDs: RSD#1 includes the combination of [S-NSSAI-1, data network name (DNN) 1] and RSD#2 includes the combination of [S-NSSAI-2, DNN1].

[0058] When the UE wants to establish a PDU session using this URSP rule, the UE first checks whether S-NSSAI-1 is part of an allowed NSSAI. If so, the UE uses RSD#1 to establish a PDU session. If S-NSSAI-1 is not part of an allowed NSSAI, the UE checks whether S-NSSAI-2 is part of an allowed NSSAI. If so, the UE uses RSD#2 to establish a PDU session. If both S-NSSAI-1 and S-NSSAI-2 are not part of an allowed NSSAI and are in a rejected NSSAI, the UE cannot establish a PDU session using this URSP rule. In aspects of the present disclosure, the UE is allowed (i.e., configured by the network) to register with an S-NSSAI (which is a replacement for S-NSSAI-1) and the replacement S-NSSAI is not part of the NSSAI configured by the UE.

[0059] There are several possible scenarios regarding the relevance of the second network slice (S-NSSAI-2) and the list of S-NSSAIs subscribed to by the UE in the UE context stored in the UE subscription data and the AMF. Scenario a) S-NSSAI-2 is part of the subscribed S-NSSAI and is already part of the allowed NSSAI. Scenario b) S-NSSAI-2 is part of the subscribed S-NSSAI but not part of the allowed NSSAI, and S-NSSAI-2 can be added to the allowed NSSAI because S-NSSAI-2 is supported in the current TA. Scenario c) S-NSSAI-2 is part of the subscribed S-NSSAI but not part of the allowed NSSAI, and S-NSSAI-2 cannot be added to the allowed NSSAI because S-NSSAI-2 is not supported in the UE's current TA. Scenario d) S-NSSAI-2 is not part of the subscribed S-NSSAI and therefore is not part of the UE configured NSSAI, and the UE cannot request and use S-NSSAI-2 unless S-NSSAI-2 is not part of the UE configured NSSAI.

[0060] Aspects of the present disclosure describe how a network slice S-NSSAI-2 may replace a network slice S-NSSAI-1 in the above scenarios (specifically, the last two scenarios c) and d)). In scenarios a) and b), it is assumed that the alternative S-NSSAI-2 to replace the S-NSSAI-1 is part of the S-NSSAI to which the UE subscribes. Therefore, if S-NSSAI-2 is allowed for application data services, the alternative S-NSSAI-2 will be configured in the UE URSP rules (specifically, in the URSP rules for establishing the current PDU session on S-NSSAI-1). Therefore, there is no need for the SMF to indicate any alternative S-NSSAI-2 to the UE in the NAS SM signaling for PDU session release. It is sufficient to indicate to the UE that the current PDU session needs to be reestablished on a different S-NSSAI and that the UE will choose to use another RSD with an S-NSSAI having a different S-NSSAI-1.

[0061] Aspects of the present disclosure relate to an AMF that indicates to a UE during a registration procedure whether the network supports an alternative slice (S-NSSAI) feature and / or whether the UE is allowed to request an alternative S-NSSAI. The AMF may also indicate to the SMF that a PDU session should be established on an alternative S-NSSAI. The SMF sends a PDU Session Release (or Modify) message containing a new 5GSM cause value to the UE to indicate to the UE that re-establishment on an alternative S-NSSAI is desired. If (a) there is no RSD with an S-NSSAI different from S-NSSAI-1 or (b) the S-NSSAI from other RSDs is in the rejected NSSAI, the UE sends a registration request for an unknown network slice that is desired to be an alternative to the subscribed S-NSSAI (e.g., an alternative to S-NSSAI-1, where the alternative network slice is assumed to be S-NSSAI-2).

[0062] As used herein, the term "replacement" S-NSSAI feature (or "compatible" S-NSSAI feature) means functionality supported by the network and the UE, where a first S-NSSAI of a PDU session may be exchanged with another (second) S-NSSAI, where the second S-NSSAI may or may not be included in the UE's configured NSSAI. In an implementation, the second S-NSSAI is not part of the UE's configured NSSAI, and the network determines and configures the UE accordingly. Additionally, in the network, the second S-NSSAI replaces the first S-NSSAI (e.g., the first S-NSSAI-1 is to be replaced by or exchanged with the second S-NSSAI).

[0063] Aspects of the present disclosure include re-establishment of a current PDU session where an alternative S-NSSAI is applicable. The implementation assumes that the UE has established a PDU session and due to, for example, the above-mentioned events, the current PDU session (or PDU sessions) must be transferred from a first network slice (S-NSSAI-1) to a second network slice (S-NSSAI-2).

[0064] Figure 3 An example of a signaling flow diagram 300 is illustrated that supports techniques for changing network slices for a PDU session according to aspects of the present disclosure. The example signaling flow diagram 300 illustrates how to trigger a UE to (re)establish a current PDU session (from a first S-NSSAI) to replace a second S-NSSAI. The UE (re)establishes a current PDU session (using a first S-NSSAI-1) and replaces a second S-NSSAI (S-NSSAI-2) for the new PDU session.

[0065] UE 104 requests to register with the network (at step 0), specifically, to register with the first network slice (e.g., S-NSSAI-1). In the NAS Registration Request message, the UE may indicate its capabilities (e.g., core network capabilities, 5GMM capabilities) to AMF 120. In addition to the new 5GMM capabilities, the UE also includes a feature of whether the UE supports requesting an alternative S-NSSAI. This UE capability may be used in the AMF to determine whether to provide the UE with a configuration that allows the UE to request an alternative S-NSSAI.

[0066] The AMF sends a registration accept message to the UE (at step 1), and the message may include a new indication (e.g., configuration) indicating that the UE is allowed to request an alternative S-NSSAI. This new indication from the AMF has at least one of the following meanings: (a) the network supports the "alternative" S-NSSAI feature and / or (b) the UE is allowed to use the feature of requesting an "alternative" S-NSSAI. The AMF determines whether to send this new indication to the UE based on the UE 5GMM capabilities received in step 0, the UE subscription data (e.g., whether the UE is a subscriber to a specific organization or enterprise), the type of S-NSSAI to which the UE subscribes, and / or the AMF capabilities and AMF local configuration. If the AMF does not support the feature of replacing S-NSSAI or the AMF does not allow the UE to use the feature (e.g., a low priority UE), the AMF does not send the indication to the UE. If the UE does not receive an indication that the UE is allowed to request an alternative S-NSSAI, the UE should not initiate step 6.

[0067] The UE initiates (at step 2) establishment of a PDU session on S-NSSAI-1 towards SMF1 302. For example, the UE establishes the PDU session using RSD#1 (e.g., from the example of UE subscription data and configuration for two network slices included above). The AMF determines (at step 3) at least one of the following: (a) S-NSSAI-1 becomes unavailable and (b) a replacement S-NSSAI is available to replace S-NSSAI-1. S-NSSAI-1 may become unavailable due to any of non-mobility events (e.g., operations, administration, and maintenance (OAM) or NSSF / NF reconfiguration or S-NSSAI-1 will be down due to network maintenance); or UE mobility events (e.g., T-AMF does not support S-NSSAI-1). In conventional solutions, the AMF triggers the release of the PDU session associated with the no longer available S-NSSAI. In the described technique, the AMF implements new features and determines that the no longer available S-NSSAI may be replaced by another (e.g., replacement) S-NSSAI.

[0068] The AMF sends a request message to SMF1 (at step 4a) to indicate that the PDU Session should not be released or modified. The AMF calls the Nsmf_PDUSession_ReleaseSMContext service operation to request the release of the PDU Session. The AMF calls the Nsmf_PDUSession_UpdateSMContext service operation to request the modification of the PDU Session. If the AMF determines that S-NSSAI-1 is no longer available but there is an alternative S-NSSAI that can be used to replace S-NSSAI-1, then the AMF includes a new indication to the SMF that supports the alternative S-NSSAI.

[0069] The SMF determines to release the PDU session (at step 4b). The PDU session may have any session and service continuity (SSC) mode (e.g. SSC mode 1, SSC mode 2 or SSC mode 3). Although for a PDU session in SSC mode 1, the network preserves the connection services provided to the UE (i.e. no IP address / prefix change), following a network event in which a change of network slice is unavoidable, the SMF may then trigger the release of the PDU session with a re-establishment cause value as described below. For a PDU session in SSC mode 2 or mode 3, the SMF initiates a PDU session release with a re-establishment cause value as described below. In addition, the SMF releases the IP address and / or prefix allocated to the PDU session and releases the corresponding user plane resources in the UPF using N4 signaling (not shown in the figure).

[0070] When the SMF wants to release a PDU session due to congestion or the S-NSSAI is no longer available, in the current system, the SMF includes a 5GSM cause value #69 "Insufficient resources for a particular slice" in the PDU Session Release Command message. For a PDU session of SSC mode 2, when the SMF wants the UE to re-establish the PDU session, the SMF includes a 5GSM cause value #39 "Request reactivation". In aspects of the present disclosure, a new 5GSM cause value is specified to indicate to the UE that re-establishment on an "alternative S-NSSAI" is desired. The SMF generates an N1 SM container to be sent to the UE, including a PDU Session Release Command or a PDU Session Modification Request message including a PDU Session Identifier (ID) and a 5GSM cause value. The 5GSM cause value indicates a trigger to establish a new PDU session with the same characteristics but with a different S-NSSAI. The SMF invokes the Namf_Communication_N1N2MessageTransfer service operation (N1 SM container, N2 information), and the SMF may not include a "skip indicator". By not including the "skip indicator", the SMF indicates to the AMF that the AMF needs to transmit the S1 SM container to the UE even if the UE is in the idle state. If the UP connection for the PDU session is active, the SMF shall also include an N2 resource release request (PDU session ID) in the Namf_Communication_N1N2MessageTransfer to release the (R)AN resources associated with the PDU session.

[0071] The AMF forwards the N1 SM container to the UE via a NAS transport message (at step 4c) and forwards the N2 information to the access network (AN) when available. The N1 SM container containing the request to release the PDU session contains the new 5GSM cause value "Re-establishment requested with different S-NSSAI" described in step 4b. The UE confirms receipt of the N1 SM container to the SMF.

[0072] After receiving the request in step 4, the UE releases the current or old PDU session, and the UE attempts to establish a new PDU session for the same user service (e.g., identified by the same URSP rule) using a different (i.e., alternative) S-NSSAI. As described above, the UE may check the URSP rules and identify whether there are one or more RSDs included in the URSP rules. If the UE identifies another RSD (e.g., RSD#2) that includes another S-NSSAI (e.g., S-NSSAI-2), the UE initiates establishment of a PDU session using RSD#2. If S-NSSAI-2 is not part of an allowed NSSAI and is not in a rejected NSSAI, the UE triggers a registration procedure to register with S-NSSAI-2. After S-NSSAI-2 becomes part of an allowed NSSAI, the UE starts establishing a PDU session with S-NSSAI-2.

[0073] However, the UE is unable to determine the alternative S-NSSAI (at step 5) due to conditions such as the following: (1) there is no RSD with an S-NSSAI different from S-NSSAI-1; or (2) one or more S-NSSAIs from other RSDs of the same URSP rule are in the rejected NSSAI. In this case, if the UE is configured to use the features described in step 1, then the UE determines to initiate a procedure to request registration with an alternative S-NSSAI of S-NSSAI-1 (at step 6). If the UE does not have a URSP rule (i.e., no stored or associated S-NSSAI for an established PDU session (e.g., the UE established the PDU session using local configuration)), then the UE re-establishes the PDU session on the alternative S-NSSAI using the local configuration if the alternative S-NSSAI is available in the local configuration. If there is no alternative S-NSSAI associated with the user traffic of the current or old PDU session, then the UE triggers step 6.

[0074] The UE sends a Registration Request message to the AMF (at step 6), which includes a requested NSSAI parameter (also referred to as an information element (IE)). The UE includes in the requested NSSAI (or a new type of requested S-NSSAI indication) a new parameter that the UE requests to register with an S-NSSAI that is an alternative to S-NSSAI-1. In other words, the UE requests to register with a new and unknown S-NSSAI that should be determined in the network (e.g., determined by the AMF and / or NSSF), where the new S-NSSAI should be able to serve data services as an alternative to S-NSSAI-1. This new S-NSSAI is not part of the UE's configured NSSAI, and the UE may include the additional S-NSSAI that is part of the configured NSSAI in the requested NSSAI.

[0075] After receiving the Registration Request message (including a request for a replacement S-NSSAI (as described in step 6, in the requested NSSAI)), the AMF (optionally together with the NSSF and / or OAM system) determines (at step 7) the S-NSSAI (e.g. S-NSSAI-3) supported in the UE's current TA. It is determined that S-NSSAI-3 should beneficially be supported in multiple Tas to form a larger new registration area. If S-NSSAI-3 is not part of the S-NSSAI to which the UE subscribes (i.e., not part of the UE configured NSSAI), the AMF determines to trigger network slicing configuration in the UE by sending the new configured NSSAI to the UE.

[0076] The AMF (and / or NSSF) may determine to apply a mapping of S-NSSAI-3 to [S-NSSAI-1 (in case of non-roaming) or HPLMN S-NSSAI (in case of roaming)]. The AMF (and / or NSSF) generates a new configured NSSAI and a new allowed NSSAI. If the UE is not roaming, the new configured NSSAI includes S-NSSAI-3 and a mapping of configured S-NSSAI-3 to S-NSSAI-1 (which is also the HPLMN S-NSSAI). If the UE roams into a visited public land mobile network (VPLMN) and S-NSSAI-1 is configured as a VPLMN S-NSSAI value mapped to an HPLMN S-NSSAI value (e.g., S-NSSAI-H), then the newly configured NSSAI will swap S-NSSAI-1 with S-NSSAI-3 in the configured S-NSSAI (and allowed S-NSSAI) and update the mapping information from "S-NSSAI-1 maps to S-NSSAI-H" to "S-NSSAI-3 maps to S-NSSAI-H".

[0077] In one or more embodiments, the first network slice may be S-NSSAI-1 (which is the S-NSSAI value used in the visited PLMN) or the HPLMN value of S-NSSAI. In the example of a non-roaming case: (1) Old configured NSSAI: S-NSSAI-1; Mapping of configured NSSAI: None. (2) New configured NSSAI: S-NSSAI-2; Mapping of configured NSSAI: S-NSSAI-2 to S-NSSAI-1. In the example of a roaming case (where S-NSSAI-1 is used for the serving VPLMN and the HPLMN S-NSSAI value is used in the HPLMN), the AMF replaces the S-NSSAI-1 with the S-NSSAI-2 value. An example of a roaming case for a configured NSSAI (which also applies similarly to an allowed NSSAI) is as follows: (1) Old configured NSSAI: S-NSSAI-1; mapping of configured NSSAI: S-NSSAI-1 to HPLMN S-NSSAI value. (2) New configured NSSAI: S-NSSAI-2; mapping of configured NSSAI: S-NSSAI-2 to HPLMN S-NSSAI value.

[0078] The AMF sends a Registration Accept message to the UE (at step 8), the Registration Accept message including the configured NSSAI (e.g., including S-NSSAI-3 instead of S-NSSAI-1) and the mapping of the configured NSSAI (e.g., including a mapping of S-NSSAI-3 to S-NSSAI-1 or a mapping of S-NSSAI-3 to S.NSSAI-H). In addition, a new allowed NSSAI may be included, in which S-NSSAI-3 is added and S-NSSAI-1 is removed, and including a corresponding mapping of S-NSSAI-3 to S-NSSAI-1 or a mapping of S-NSSAI-3 to S-NSSAI-H. If the alternative S-NSSAI cannot be determined and provided to the UE, the AMF will reject the sending of S-NSSAI-1 in the NSSAI to the UE. The AMF uses an existing cause value for rejected S-NSSAI-1 (e.g., rejected due to unavailability in the registration area) or may introduce a new cause value to indicate that S-NSSAI-1 is temporarily rejected and no alternative S-NSSAI is available. If the UE receives the mapping information of S-NSSAI-3 to S-NSSAI-1 of step 8, the UE triggers a new PDU session establishment to S-NSSAI-3 (at step 9), and in addition, the UE includes the mapping information of S-NSSAI-3 to S-NSSAI-1.

[0079] The UE sends a NAS message to the AMF (at step 10), which includes the new PDU Session ID (and optionally the association with the old PDU Session ID), S-NSSAI-3, the mapping of S-NSSAI-3 to S-NSSAI-1, DNN1 and N1 SM container (PDU Session Establishment Request). For SSC Mode 3 of the UE, the message also includes the old PDU Session ID. The AMF selects a serving SMF (e.g. SMF3) for the new PDU Session, and the AMF forwards the N1-SM container to the serving SMF (e.g. SMF3). The AMF may forward the UE request to SMF3 using the Nsmf_PDUSession_CreateSMContext request service operation. When establishing a PDU Session on the new S-NSSAI (S-NSSAI-2), the UE may use the request type "Initial Request" for PDU Sessions of SSC Modes 1 and 2. For PDU sessions in SSC mode 3, the UE may use request type "initial request" or "existing", which should not impact the AMF operation as the AMF shall select the SMF in S-NSSAI-2.

[0080] SMF3 304 proceeds to establish the PDU session by using S-NSSAI-3 (at step 11). If the mapping information of S-NSSAI-3 to S-NSSAI-1 is provided to SMF3 and if SMF3 is in the UE HPLMN (i.e., non-roaming case), then SMF3 uses the mapped S-NSSAI-1 value in the service operation to the UDM to retrieve the UE SM subscription data. SMF3 does not use the mapped S-NSSAI-1 value as input to select another SMF in S-NSSAI-1. SMF3 acts as an anchor SMF for the PDU session. If SMF3 is in the UE's VPLMN (i.e., roaming case), then SMF3 may determine to use the mapped S-NSSAI value (i.e., S-NSSAI-1) to select and contact the SMF in the HPLMN to establish the home routed PDU session.

[0081] If the PDU session establishment procedure for roaming scenario is applicable, SMF3 will control the intermediate UPF and SMF1 will serve the anchor UPF (i.e., establish an N9 tunnel between the intermediate UPF and the anchor UPF). If the PDU session is to be used for local breakout (LBO), SMF3 uses the mapped S-NSSAI-1 value in the service operation to UDM to retrieve the UE SM subscription data, and SMF3 does not use the mapped S-NSSAI-1 value as input to select another SMF in S-NSSAI-1 in the HPLMN. SMF2 retrieves the UE session management subscription data from UDM by invoking a service operation with Subscriber Data Management (SDM), and the Nudm_SDM_Get request contains the following parameters: Subscription Permanent Identifier (SUPI), Session Management Subscription Data, Selected DNN, S-NSSAI (which is S-NSSAI-1) to which the S-NSSAI value is mapped, etc. The S-NSSAI to which the S-NSSAI value is mapped is also used in non-roaming scenarios.

[0082] In an alternative implementation, the AMF may determine (at step 3) to perform a UE Configuration Update (UCU) procedure, where the AMF (and / or together with the NSSF) generates a new configured NSSAI and allowed NSSAI containing S-NSSAI-3 and a mapping of S-NSSAI-3 to S-NSSAI-1 and sends it to the UE. This substitute may be applied when the AMF knows that the possible substitute S-NSSAI-3 is not part of the S-NSSAI to which the UE subscribes. By performing aspects of the described techniques for changing the network slice of a PDU session, the UE determines or discovers a substitute S-NSSAI according to one or more URSP rules. If no substitute S-NSSAI is available in the URSP rules, then after the UE requests a substitute S-NSSAI from the AMF, a new S-NSSAI is determined in the AMF.

[0083] Aspects of the present disclosure include establishing a new PDU session where an alternative S-NSSAI is applicable. Embodiment, consider a scenario where a UE requests to establish a new PDU session by using a first S-NSSAI (e.g., S-NSSAI-1). The network (e.g., AMF or NSSF) determines that (1) S-NSSAI-1 is currently unavailable (due to congestion, overload, or unmet SLA) and (2) substitutes a second S-NSSAI (S-NSSAI-2) that is part of the S-NSSAI to which the UE subscribes. Assume that S-NSSAI-2 is not part of the UE's allowed NSSAI.

[0084] Figure 4An example of a signaling flow diagram 400 is illustrated to support techniques for changing network slices for a PDU session according to aspects of the present disclosure. The example signaling flow diagram 400 illustrates a UE establishing a new PDU session (on a first unavailable S-NSSAI) where the AMF determines to use an alternative second S-NSSAI.

[0085] UE 104 requests to register with the network (at step 0), specifically, to register with the first network slice (e.g., S-NSSAI-1). In the NAS Registration Request message, the UE may indicate its capabilities (e.g., core network capabilities, 5GMM capabilities) to AMF 120. In addition to the new 5GMM capabilities, the UE also includes a feature of whether the UE supports requesting an alternative S-NSSAI. This UE capability may be used in the AMF to determine whether to provide the UE with a configuration that allows the UE to request an alternative S-NSSAI.

[0086] The AMF sends a registration accept message to the UE (at step 1), and the message may include a new indication (e.g., configuration) indicating that the UE is allowed to request an alternative S-NSSAI. This new indication from the AMF has at least one of the following meanings: (a) the network supports the "alternative" S-NSSAI feature and / or (b) the UE is allowed to use the feature of requesting an "alternative" S-NSSAI. The AMF determines whether to send this new indication to the UE based on the UE 5GMM capabilities received in step 0, the UE subscription data (e.g., whether the UE is a subscriber to a specific organization or enterprise), the type of S-NSSAI to which the UE subscribes, and / or the AMF capabilities and AMF local configuration. If the AMF does not support the feature of replacing S-NSSAI or the AMF does not allow the UE to use the feature (e.g., a low priority UE), the AMF does not send the indication to the UE. If the UE does not receive an indication that the UE is allowed to request an alternative S-NSSAI, the UE should not initiate step 6.

[0087] The UE initiates a new PDU Session establishment procedure (at step 2) (e.g., according to RSD#1 from the example of UE subscription data and configuration for two network slices included above). The UE sends a NAS message to the AMF, including the New PDU Session ID, S-NSSAI-1, DNN1 and N1 SM container (PDU Session Establishment Request).

[0088] The AMF determines (at step 3) that S-NSSAI-1 is not available, but an alternative S-NSSAI is available to replace S-NSSAI-1. The AMF determines one of the following options. The first option is similar to the above reference Figure 3Step 3 described, where the AMF calls the Nsmf_PDUSession_CreateSMContext service operation to request the creation of a new PDU session for the selected SMF serving S-NSSAI-1, where the AMF includes a new indication to the SMF that it supports the replacement S-NSSAI (as described above with reference to Figure 3 In addition, the above reference may be performed Figure 3 Steps 4b to 10 are described, and SMF1 will be involved in the procedure, but SMF1 is not used to replace the final PDU session establishment on S-NSSAI (e.g. S-NSSAI-3).

[0089] In the second option, the AMF determines not to proceed with the PDU session establishment and the AMF rejects the request to the UE with an indication that the requested S-NSSAI-1 is not available and an alternative S-NSSAI may be used. For this purpose, existing 5GMM reject causes (e.g., #69 "Insufficient resources for a particular slice", #69 "Insufficient resources for a particular slice and DNN", or "Payload not forwarded") may be used. In addition, a new 5GMM indication is introduced that the UE may request an N1 SM payload (i.e., PDU session establishment request) on an alternative S-NSSAI. Alternatively, a new 5GMM reject cause may be introduced to trigger the UE to request an N1 SM payload for PDU session establishment on an alternative S-NSSAI. The benefit of the new 5GMM reject cause is that the UE will be indicated to trigger registration to an (unknown) alternative S-NSSAI, even if the UE does not have an RSD entry with an S-NSSAI different from S-NSSAI-1. For step 3 option b), the AMF sends a NAS message to the UE (at step 4) to indicate that the PDU session establishment request is rejected by using one of the alternatives described in step 3 option b). In an embodiment, the AMF includes a new 5GMM rejection cause that triggers the UE to request a new PDU session establishment on an alternative unknown S-NSSAI.

[0090] After receiving the NAS message in step 4, the UE releases the current or old PDU session, and the UE attempts to establish a new PDU session for the same user service (e.g., identified by the same URSP rule) using a different (i.e., alternative) S-NSSAI. As described above, the UE may check the URSP rules and identify whether there are one or more RSDs included in the URSP rules. If the UE identifies another RSD (e.g., RSD#2) that includes another S-NSSAI (e.g., S-NSSAI-2), the UE initiates establishment of a PDU session using RSD#2. If S-NSSAI-2 is not part of the allowed NSSAI and is not in the rejected NSSAI, the UE triggers a registration procedure to register with S-NSSAI-2. After S-NSSAI-2 becomes part of the allowed NSSAI, the UE starts to establish a PDU session with S-NSSAI-2.

[0091] However, the UE may be unable to determine the alternative S-NSSAI (at step 5) due to conditions such as the following: (1) there is no RSD with an S-NSSAI different from S-NSSAI-1; or (2) one or more S-NSSAIs from other RSDs of the same URSP rule are in the rejected NSSAI. In this case, if the UE is configured to use the features described in step 1, the UE determines to initiate a procedure to request registration with an alternative S-NSSAI of S-NSSAI-1 (at step 6). If the UE does not have a URSP rule (i.e., no stored or associated S-NSSAI for an established PDU session (e.g., the UE established the PDU session using local configuration)), then if the alternative S-NSSAI is available in the local configuration, the UE re-establishes the PDU session on the alternative S-NSSAI using the local configuration. If there is no alternative S-NSSAI associated with the user traffic of the current or old PDU session, the UE triggers step 6.

[0092] The UE sends a Registration Request message to the AMF (at step 6), which includes a requested NSSAI parameter (also referred to as an IE). The UE includes in the requested NSSAI (or a new type of requested S-NSSAI indication) a new parameter that the UE requests to register with an S-NSSAI that is an alternative to S-NSSAI-1. In other words, the UE requests to register with a new and unknown S-NSSAI that should be determined in the network (e.g., determined by the AMF and / or NSSF), where the new S-NSSAI should be able to serve data traffic as an alternative to S-NSSAI-1. This new S-NSSAI is not part of the UE configured NSSAI, and the UE may include the additional S-NSSAI in the requested NSSAI that is part of the configured NSSAI.

[0093] After receiving the Registration Request message (including a request to replace the S-NSSAI (as described in step 6, in the requested NSSAI)), the AMF (optionally together with the NSSF and / or OAM system) determines (at step 7) the S-NSSAI (e.g. S-NSSAI-3) supported in the UE's current TA. It is determined that S-NSSAI-3 should beneficially be supported in multiple TAs to form a larger new registration area. If the S-NSSAI-3 is not part of the S-NSSAI to which the UE is subscribed (i.e., not part of the UE configured NSSAI), the AMF determines to trigger network slicing configuration in the UE by sending the new configured NSSAI to the UE.

[0094] The AMF (and / or NSSF) may determine to apply a mapping of S-NSSAI-3 to [S-NSSAI-1 (in case of non-roaming) or HPLMN S-NSSAI (in case of roaming)]. The AMF (and / or NSSF) generates a new configured NSSAI and a new allowed NSSAI. If the UE is not roaming, the new configured NSSAI includes S-NSSAI-3 and a mapping of configured S-NSSAI-3 to S-NSSAI-1 (which is also the HPLMN S-NSSAI). If the UE roams to a VPLMN and S-NSSAI-1 is configured as a VPLMN S-NSSAI value mapped to an HPLMN S-NSSAI value (e.g., S-NSSAI-H), then the newly configured NSSAI will swap S-NSSAI-1 with S-NSSAI-3 in the configured S-NSSAI (and allowed S-NSSAI) and update the mapping information from "S-NSSAI-1 maps to S-NSSAI-H" to "S-NSSAI-3 maps to S-NSSAI-H".

[0095] In one or more embodiments, the first network slice may be S-NSSAI-1 (which is the S-NSSAI value used in the visited PLMN) or the HPLMN value of S-NSSAI. In the example of a non-roaming case: (1) Old configured NSSAI: S-NSSAI-1; Mapping of configured NSSAI: None. (2) New configured NSSAI: S-NSSAI-2; Mapping of configured NSSAI: S-NSSAI-2 to S-NSSAI-1. In the example of a roaming case (where S-NSSAI-1 is used for the serving VPLMN and the HPLMN S-NSSAI value is used in the HPLMN), the AMF replaces the S-NSSAI-1 with the S-NSSAI-2 value. An example of a roaming case for a configured NSSAI (which also applies similarly to an allowed NSSAI) is as follows: (1) Old configured NSSAI: S-NSSAI-1; mapping of configured NSSAI: S-NSSAI-1 to HPLMN S-NSSAI value. (2) New configured NSSAI: S-NSSAI-2; mapping of configured NSSAI: S-NSSAI-2 to HPLMN S-NSSAI value.

[0096] The AMF sends a Registration Accept message to the UE (at step 8), the Registration Accept message including the configured NSSAI (e.g., including S-NSSAI-3 instead of S-NSSAI-1) and the mapping of the configured NSSAI (e.g., including a mapping of S-NSSAI-3 to S-NSSAI-1 or a mapping of S-NSSAI-3 to S.NSSAI-H). In addition, a new allowed NSSAI may be included, in which S-NSSAI-3 is added and S-NSSAI-1 is removed, and including a corresponding mapping of S-NSSAI-3 to S-NSSAI-1 or a mapping of S-NSSAI-3 to S-NSSAI-H. If the alternative S-NSSAI cannot be determined and provided to the UE, the AMF will reject the sending of S-NSSAI-1 in the NSSAI to the UE. The AMF uses an existing cause value for rejected S-NSSAI-1 (e.g., rejected due to unavailability in the registration area) or may introduce a new cause value to indicate that S-NSSAI-1 is temporarily rejected and no alternative S-NSSAI is available. If the UE receives the mapping information of S-NSSAI-3 to S-NSSAI-1 of step 8, the UE triggers a new PDU session establishment to S-NSSAI-3 (at step 9), and in addition, the UE includes the mapping information of S-NSSAI-3 to S-NSSAI-1.

[0097] The UE sends a NAS message to the AMF (at step 10), the message includes the new PDU Session ID (and optionally the association with the old PDU Session ID), S-NSSAI-3, the mapping of S-NSSAI-3 to S-NSSAI-1, DNN1 and N1SM container (PDU Session Establishment Request). For SSC Mode 3 of the UE, the message also includes the old PDU Session ID. The AMF selects a serving SMF (e.g., SMF3 402) for the new PDU Session, and the AMF forwards the N1-SM container to the serving SMF (e.g., SMF3). The AMF may forward the UE request to SMF3 using the Nsmf_PDUSession_CreateSMContext request service operation. When establishing a PDU Session on the new S-NSSAI (S-NSSAI-2), the UE may use the request type "initial request" for PDU Sessions of SSC Modes 1 and 2. For PDU sessions in SSC mode 3, the UE may use request type "initial request" or "existing", which should not impact the AMF operation as the AMF shall select the SMF in S-NSSAI-2.

[0098] By performing aspects of the described techniques for changing the network slice of a PDU session, the AMF is able to inform the UE that a PDU session needs to be established on an alternative S-NSSAI without engaging the session management (SM) (sub) layer. The UE is able to send a request for a new 5GMM capability (e.g., the capability to support alternative S-NSSAI features) of the S-NSSAI that will replace the current S-NSSAI. In addition, the UE receives configuration information indicating whether to use the features of the alternative S-NSSAI. The UE receives a new 5GSM indication to re-establish a PDU session on an S-NSSAI that is an alternative to the currently used S-NSSAI (e.g., S-NSSAI-1). The UE determines a request to register with the S-NSSAI that replaces S-NSSAI-1, and sends a request to the AMF to register with the S-NSSAI of the alternative network slice that is S-NSSAI-1.

[0099] In addition, in aspects of the described technology for changing the network slice of a PDU session, the AMF is capable of receiving a new UE 5GMM capability (e.g., a capability to support an alternative S-NSSAI feature) requesting an S-NSSAI that will replace the current S-NSSAI. In addition, the AMF sends configuration information to the UE to indicate whether to use the feature of the alternative S-NSSAI. The AMF determines that S-NSSAI-1 is no longer available, but an alternative S-NSSAI can be used. The AMF sends an indication to the SMF serving the PDU session established on S-NSSAI-1 to request the release of the PDU session, and the alternative S-NSSAI can be used. The AMF determines to request registration with the S-NSSAI of the alternative network slice that is S-NSSAI-1. The AMF also receives a registration request for an S-NSSAI that is an alternative to the currently used S-NSSAI-1 from the UE and determines an alternative S-NSSAI-3. The AMF sends the new configured NSSAI and the allowed NSSAI to the UE, including mapping information of S-NSSAI-3 to S-NSSAI-1.

[0100] Figure 5 An example of a block diagram 500 illustrating a device 502 that supports techniques for changing network slices for a PDU session according to aspects of the present disclosure. The device 502 may be an example of an AMF (or a network device implementing an AMF) described herein. The device 502 may support wireless communications with one or more network entities 102, UEs 104, or any combination thereof. The device 502 may include components for bidirectional communication, including components for transmitting and receiving communications, such as a processor 504, a memory 506, a transceiver 508, and an I / O controller 510. These components may be in electronic communication or otherwise coupled (e.g., operatively, communicatively, functionally, electronically, electrically) via one or more interfaces (e.g., a bus).

[0101] The processor 504, memory 506, transceiver 508, or various combinations thereof, or various components thereof may be examples of means for performing various aspects of the present disclosure described herein. For example, the processor 504, memory 506, transceiver 508, or various combinations thereof, or components thereof may support a method for performing one or more of the operations described herein.

[0102] In some implementations, the processor 504, memory 506, transceiver 508, or various combinations or components thereof may be implemented as hardware (e.g., communication management circuitry). The hardware may include a processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof configured to or otherwise support means for performing the functions described in the present disclosure. In some implementations, the processor 504 and the memory 506 coupled to the processor 504 may be configured to perform one or more of the functions described herein (e.g., execution of instructions stored in the memory 506 by the processor 504).

[0103] For example, the processor 504 may support wireless communication at the device 502 according to the examples disclosed herein. The processor 504 may be configured to or otherwise support a component for: receiving a first signaling as a registration request from a user equipment (UE) to register with a first network slice; and transmitting a second signaling indicating that the registration is accepted and that the UE is allowed to register with an alternative network slice.

[0104] In addition, the processor 504 may be configured to or otherwise support any or a combination of alternative network slices not identified in the configured NSSAI. The method further includes receiving a third signaling from the UE indicating that the UE supports the ability to register with the alternative network slice. The method further includes transmitting the third signaling to a network function serving a first PDU session established on the first network slice, the third signaling including an indication that the first PDU session can be established on the alternative network slice. The method further includes receiving a third signaling from the UE as an additional registration request to register with the alternative network slice in response to signaling the UE to reestablish the first protocol data unit (PDU) session based at least in part on the UE's inability to identify the alternative network slice. The method further includes: transmitting a fourth signaling to the UE indicating that the registration is accepted and the configured NSSAI includes an identification of the alternative network slice, the alternative network slice being mapped to the first network slice; and receiving a fifth signaling indicating that the UE has established a second PDU session using the same routing descriptor as the first PDU session based at least in part on the alternative network slice mapped to the first network slice. If the UE is not roaming, the alternative network slice is mapped to the first network slice based on the NSSAI. If the UE is roaming, the alternative network slice is mapped to the first network slice based on the HPLMN NSSAI.

[0105] Additionally or alternatively, according to the examples disclosed herein, device 502 may include: a processor; and a memory coupled to the processor, the processor being configured to receive first signaling from a UE as a registration request to register with a first network slice; and to transmit second signaling indicating acceptance of the registration and allowing the UE to register with an alternative network slice.

[0106] In addition, the wireless communication at the device 502 may include the processor being configured to identify that any or a combination of alternative network slices are not present in the configured NSSAI. The processor is configured to receive a third signaling from the UE indicating that the UE supports the ability to register with the alternative network slice. The processor is configured to transmit the third signaling to the network function serving the first PDU session established on the first network slice, the third signaling including an indication that the first PDU session can be established on the alternative network slice. The processor is configured to receive a third signaling from the UE as an additional registration request to register with the alternative network slice in response to having signaled the UE to reestablish the first PDU session based at least in part on the UE's inability to identify the alternative network slice. The processor is configured to: transmit a fourth signaling to the UE indicating that the registration is accepted and that the configured NSSAI includes an identification of the alternative network slice, the alternative network slice being mapped to the first network slice; and receive a fifth signaling indicating that the UE has established a second PDU session using the same routing descriptor as the first PDU session based at least in part on the alternative network slice mapped to the first network slice.

[0107] The processor 504 may include an intelligent hardware device (e.g., a general purpose processor, a DSP, a CPU, a microcontroller, an ASIC, an FPGA, a programmable logic device, discrete gate or transistor logic components, discrete hardware components, or any combination thereof). In some implementations, the processor 504 may be configured to operate a memory array using a memory controller. In some other implementations, the memory controller may be integrated into the processor 504. The processor 504 may be configured to execute computer-readable instructions stored in a memory (e.g., memory 506) to cause the device 502 to perform various functions of the present disclosure.

[0108] The memory 506 may include random access memory (RAM) and read-only memory (ROM). The memory 506 may store computer-readable, computer-executable code including instructions that, when executed by the processor 504, cause the device 502 to perform various functions described herein. The code may be stored in a non-transitory computer-readable medium (e.g., system memory or another type of memory). In some embodiments, the code may not be directly executed by the processor 504 but may cause a computer (e.g., when compiled and executed) to perform the functions described herein. In some embodiments, the memory 506 may include a basic I / O system (BIOS) that may control basic hardware or software operations (e.g., interacting with peripheral components or devices), etc.

[0109] I / O controller 510 can manage input and output signals of device 502. I / O controller 510 can also manage peripheral devices that are not integrated into device 502. In some embodiments, I / O controller 510 can represent a physical connection or port to an external peripheral device. In some embodiments, I / O controller 510 can utilize an operating system, such as or another known operating system. In some embodiments, I / O controller 510 may be implemented as part of a processor (e.g., processor 504). In some embodiments, a user may interact with device 502 via I / O controller 510 or via hardware components controlled by I / O controller 510.

[0110] In some implementations, the device 502 may include a single antenna 512. However, in some other implementations, the device 502 may have more than one antenna 512 (i.e., multiple antennas) capable of simultaneously transmitting or receiving multiple wireless transmissions, including multiple antenna panels or antenna arrays. The transceiver 508 may communicate bidirectionally via one or more antennas 512, wired or wireless links as described herein. For example, the transceiver 508 may represent a wireless transceiver and may communicate bidirectionally with another wireless transceiver. The transceiver 508 may also include a modem for modulating packets to provide the modulated packets to one or more antennas 512 for transmission and demodulating packets received from the one or more antennas 512.

[0111] Figure 6 An example of a block diagram 600 illustrating a device 602 that supports techniques for changing network slices for a PDU session according to aspects of the present disclosure. The device 602 may be an example of a UE 104 described herein. The device 602 may support wireless communications with one or more network entities 102, UEs 104, or any combination thereof. The device 602 may include components for bidirectional communication, including components for transmitting and receiving communications, such as a processor 604, a memory 606, a transceiver 608, and an I / O controller 610. These components may be in electronic communication or otherwise coupled (e.g., operatively, communicatively, functionally, electronically, electrically) via one or more interfaces (e.g., a bus).

[0112] The processor 604, memory 606, transceiver 608, or various combinations thereof, or various components thereof may be examples of means for performing various aspects of the present disclosure described herein. For example, the processor 604, memory 606, transceiver 608, or various combinations thereof, or components thereof may support a method for performing one or more of the operations described herein.

[0113] In some implementations, the processor 604, memory 606, transceiver 608, or various combinations or components thereof may be implemented as hardware (e.g., communication management circuitry). The hardware may include a processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof configured to or otherwise support means for performing the functions described in the present disclosure. In some implementations, the processor 604 and the memory 606 coupled to the processor 604 may be configured to perform one or more of the functions described herein (e.g., execution of instructions stored in the memory 606 by the processor 604).

[0114] For example, processor 604 may support wireless communication at device 602 according to the examples disclosed herein, and the device may include a processor; and a memory coupled to the processor, the processor being configured to: transmit first signaling to request registration with a first network slice; receive second signaling indicating registration with the first network slice and allowing registration with an alternative network slice; and transmit third signaling to establish a first PDU session on the first network slice.

[0115] In addition, the wireless communication at device 602 may include the processor being configured to identify that any or a combination of alternative network slices are not present in the configured NSSAI. The processor is configured to transmit a fourth signaling indicating that the device supports the ability to register with the alternative network slice. The processor is configured to: receive a fourth signaling indicating that the first PDU session is reestablished on the alternative network slice based at least in part on the unavailability of the first network slice; and transmit a fifth signaling to request registration with the alternative network slice based at least in part on the inability to identify the alternative network slice. The processor is configured to: receive a sixth signaling indicating that the registration is accepted and the configured NSSAI includes an identification of the alternative network slice, the alternative network slice being mapped to the first network slice; and initiate establishment of a second PDU session on the alternative network slice, the second PDU session using the same routing descriptor as the first PDU session based at least in part on the alternative network slice mapped to the first network slice. The processor is configured to transmit a fifth signaling to request registration with the alternative network slice based at least in part on determining that there is no identified alternative network slice for reestablishing the PDU session.

[0116] The processor 604 may include an intelligent hardware device (e.g., a general purpose processor, a DSP, a CPU, a microcontroller, an ASIC, an FPGA, a programmable logic device, discrete gate or transistor logic components, discrete hardware components, or any combination thereof). In some implementations, the processor 604 may be configured to operate a memory array using a memory controller. In some other implementations, the memory controller may be integrated into the processor 604. The processor 604 may be configured to execute computer-readable instructions stored in a memory (e.g., memory 606) to cause the device 602 to perform various functions of the present disclosure.

[0117] The memory 606 may include random access memory (RAM) and read-only memory (ROM). The memory 606 may store computer-readable, computer-executable code including instructions that, when executed by the processor 604, cause the device 602 to perform various functions described herein. The code may be stored in a non-transitory computer-readable medium (e.g., system memory or another type of memory). In some embodiments, the code may not be directly executed by the processor 604 but may cause a computer (e.g., when compiled and executed) to perform the functions described herein. In some embodiments, the memory 606 may include a basic I / O system (BIOS) that may control basic hardware or software operations (e.g., interacting with peripheral components or devices), etc.

[0118] I / O controller 610 can manage input and output signals of device 602. I / O controller 610 can also manage peripheral devices that are not integrated into device 2402. In some embodiments, I / O controller 610 can represent a physical connection or port to an external peripheral device. In some embodiments, I / O controller 610 can utilize an operating system, such as or another known operating system. In some embodiments, I / O controller 610 may be implemented as part of a processor (e.g., processor 604). In some embodiments, a user may interact with device 602 via I / O controller 610 or via hardware components controlled by I / O controller 610.

[0119] In some implementations, the device 602 may include a single antenna 612. However, in some other implementations, the device 602 may have more than one antenna 612 (i.e., multiple antennas) capable of simultaneously transmitting or receiving multiple wireless transmissions, including multiple antenna panels or antenna arrays. The transceiver 608 may communicate bidirectionally via one or more antennas 612, wired or wireless links as described herein. For example, the transceiver 608 may represent a wireless transceiver and may communicate bidirectionally with another wireless transceiver. The transceiver 608 may also include a modem for modulating packets to provide the modulated packets to one or more antennas 612 for transmission and demodulating packets received from the one or more antennas 612.

[0120] Figure 7 Flowchart illustrating a method 700 for supporting techniques for changing network slices for a PDU session according to aspects of the present disclosure. The operations of the method 700 may be implemented by an apparatus or component thereof as described herein. For example, the operations of the method 700 may be implemented by reference to Figures 1 to 6 The described AMF (or network device implementing AMF) is executed. In some embodiments, the device may execute a set of instructions to control the functional elements of the device to perform the described functions. In addition or alternatively, the device may use dedicated hardware to perform aspects of the described functions.

[0121] In 702, the method may include receiving first signaling as a registration request from a UE to register with a first network slice. The operations of 702 may be performed according to the examples described herein. In some embodiments, aspects of the operations of 702 may be referred to as Figure 1 The described device performs.

[0122] At 704, the method may include transmitting a second signaling indicating that the registration is accepted and that the UE is allowed to register with the alternative network slice. The operations of 704 may be performed according to the examples described herein. In some implementations, aspects of the operations of 704 may be referred to as Figure 1 The described device performs.

[0123] Figure 8 Flowchart illustrating a method 800 of supporting techniques for changing network slices for a PDU session according to aspects of the present disclosure. The operations of the method 800 may be implemented by an apparatus or component thereof as described herein. For example, the operations of the method 800 may be implemented by reference to Figures 1 to 6 The described AMF (or network device implementing AMF) is executed. In some embodiments, the device may execute a set of instructions to control the functional elements of the device to perform the described functions. In addition or alternatively, the device may use dedicated hardware to perform aspects of the described functions.

[0124] At 802, the method may include receiving third signaling from the UE indicating that the UE supports the ability to register with an alternative network slice. The operations of 802 may be performed according to the examples described herein. In some embodiments, the method may be performed by reference to Figure 1 The described apparatus performs aspects of the operations of 802 .

[0125] At 804, the method may include transmitting a third signaling to a network function serving a first PDU session established on a first network slice, the third signaling including an indication that the first PDU session may be established on an alternative network slice. The operations of 804 may be performed according to the examples described herein. In some implementations, the Figure 1 The described apparatus performs aspects of the operations of 804 .

[0126] At 806, the method may include receiving signaling from the UE as an additional registration request to register with the alternative network slice based on the UE's inability to identify the alternative network slice in response to the UE being signaled to reestablish the first PDU session. The operations of 806 may be performed according to the examples described herein. In some implementations, the Figure 1 The described apparatus performs aspects of the operations of 806 .

[0127] At 808, the method may include transmitting to the UE signaling that the registration is accepted and that the configured NSSAI includes an identification of an alternative network slice, the alternative network slice being mapped to the first network slice. The operations of 808 may be performed according to the examples described herein. In some embodiments, the method may be performed by reference to Figure 1 The described apparatus performs aspects of the operations of 808 .

[0128] At 810, the method may include receiving signaling indicating that the UE has established a second PDU session using the same routing descriptor as a first PDU session based on an alternative network slice mapped to the first network slice. The operations of 810 may be performed according to the examples described herein. In some embodiments, the UE may be configured to perform the second PDU session using the same routing descriptor as the first PDU session based on the alternative network slice mapped to the first network slice. Figure 1 The described apparatus performs aspects of the operations of 810 .

[0129] Fig. 9 Flowchart illustrating a method 900 for supporting techniques for changing network slices for a PDU session according to aspects of the present disclosure. The operations of the method 900 may be implemented by an apparatus or component thereof as described herein. For example, the operations of the method 900 may be implemented by reference to Figures 1 to 6 The described UE 104 performs. In some embodiments, the device may execute a set of instructions to control the functional elements of the device to perform the described functions. In addition or alternatively, the device may use dedicated hardware to perform aspects of the described functions.

[0130] At 902, the method may include transmitting a first signaling to request registration with a first network slice. The operations of 902 may be performed according to the examples described herein. In some embodiments, the Figure 1 The described apparatus performs aspects of the operations of 902 .

[0131] At 904, the method may include receiving second signaling indicating registration with the first network slice and allowing registration with the alternative network slice. The operations of 904 may be performed according to the examples described herein. In some embodiments, the method may be performed by reference to Figure 1 The described apparatus performs aspects of the operations of 904 .

[0132] At 906, the method may include transmitting a third signaling to establish a first PDU session on the first network slice. The operation of 906 may be performed according to the examples described herein. In some embodiments, the method may be performed by reference to Figure 1 The described apparatus performs aspects of the operations of 906 .

[0133] Fig.10 Flowchart illustrating a method 1000 for supporting techniques for changing network slices for a PDU session according to aspects of the present disclosure. The operations of the method 1000 may be implemented by an apparatus or component thereof as described herein. For example, the operations of the method 1000 may be implemented by reference to Figures 1 to 6 The described UE 104 performs. In some embodiments, the device may execute a set of instructions to control the functional elements of the device to perform the described functions. In addition or alternatively, the device may use dedicated hardware to perform aspects of the described functions.

[0134] At 1002, the method may include transmitting fourth signaling indicating that the device supports the ability to register with an alternative network slice. The operations of 1002 may be performed according to the examples described herein. In some embodiments, the method may be performed by reference to Figure 1 The described apparatus performs aspects of the operations of 1002 .

[0135] At 1004, the method may include receiving signaling indicating reestablishing the first PDU session on an alternative network slice based on the unavailability of the first network slice. The operations of 1004 may be performed according to the examples described herein. In some embodiments, the first PDU session may be reestablished on an alternative network slice based on the unavailability of the first network slice. Figure 1 The described apparatus performs aspects of the operations of 1004 .

[0136] At 1006, the method may include transmitting signaling to request registration with an alternative network slice based on failure to identify the alternative network slice. The operations of 1006 may be performed according to the examples described herein. In some implementations, the method may include transmitting signaling to request registration with an alternative network slice based on failure to identify the alternative network slice. Figure 1 The described apparatus performs aspects of the operations of 1006 .

[0137] At 1008, the method may include receiving signaling indicating that the registration is accepted and that the configured NSSAI includes an identification of an alternative network slice, the alternative network slice being mapped to the first network slice. The operations of 1008 may be performed according to the examples described herein. In some embodiments, the Figure 1 The described apparatus performs aspects of the operations of 1008 .

[0138] At 1010, the method may include establishing a second PDU session on the alternative network slice, the second PDU session using the same routing descriptor as the first PDU session based on the alternative network slice mapped to the first network slice. The operations of 1010 may be performed according to the examples described herein. In some embodiments, the reference Figure 1 The described apparatus performs aspects of the operations of 1010 .

[0139] It should be noted that the methods described herein describe possible implementations, and that the operations and steps may be rearranged or otherwise modified and other implementations are possible. Furthermore, aspects from two or more of the methods may be combined.

[0140] The various illustrative blocks and components described in connection with the present disclosure may be implemented or performed with a general purpose processor, a DSP, an ASIC, a CPU, an FPGA or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general purpose processor may be a microprocessor, but alternatively, the processor may be any processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices (e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration).

[0141] The functions described herein may be implemented as hardware, software executed by a processor, firmware, or any combination thereof. If implemented as software executed by a processor, the functions may be stored on a computer-readable medium or transmitted by a computer-readable medium as one or more instructions or codes. Other examples and implementations are within the scope of the present disclosure and the appended claims. For example, due to the nature of software, the functions described herein may be implemented using software executed by a processor, hardware, firmware, hard wiring, or a combination of any of these. Features implementing the functions may also be physically located at various locations, including being distributed so that portions of the functions are implemented at different physical locations.

[0142] Computer-readable media include both non-transitory computer storage media and communication media, including any media that facilitates transfer of a computer program between locations. Non-transitory storage media may be any available media that can be accessed by a general-purpose or special-purpose computer. By way of example, and not limitation, non-transitory computer-readable media may include RAM, ROM, electrically erasable programmable ROM (EEPROM), flash memory, compact disk (CD) ROM or other optical disk storage, magnetic disk storage or other magnetic storage, or any other non-transitory media that can be used to carry or store desired program code in the form of instructions or data structures and that can be accessed by a general-purpose or special-purpose computer or a general-purpose or special-purpose processor.

[0143] Any connection may be properly referred to as a computer-readable medium. For example, if the software is transmitted from a website, server or other remote source using a coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio and microwaves, then the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio and microwaves are included in the definition of computer-readable media. Disks and optical discs, as used herein, include CDs, laser discs, optical discs, digital versatile discs (DVDs), floppy disks, and Blu-ray discs, where disks typically reproduce data magnetically, while optical discs reproduce data optically with lasers. Combinations of the above are also included within the scope of computer-readable media.

[0144] As used herein, the claims include that the "or" used in a list of items (e.g., a list of items modified by phrases such as "at least one" or "one or more" or "one or both") indicates an inclusive list, so that, for example, a list of at least one of A, B, or C means A or B or C or AB or AC or BC or ABC (i.e., A and B and C). Similarly, a list of one or more of A, B, or C means A or B or C or AB or AC or BC or ABC (i.e., A and B and C). In addition, as used herein, the phrase "based on" should not be interpreted as a closed set of reference conditions. For example, an exemplary step described as "based on condition A" can be based on both condition A and condition B without departing from the scope of the present disclosure. In other words, as used herein, the phrase "based on" should be interpreted in the same manner as the phrase "at least partially based on". In addition, as used herein, the claims include that a "group" may include one or more elements.

[0145] When referring to a network entity, the terms "transmit," "receive," or "communicate" may refer to any part of a network entity of a RAN (e.g., base station, CU, DU, RU) communicating with another device (e.g., directly or via one or more other network entities).

[0146] The description set forth herein describes exemplary configurations in conjunction with the accompanying drawings and does not represent all examples that may be implemented or within the scope of the claims. The term "example" as used herein means "serving as an example, instance, or illustration" rather than "preferably" or "more advantageous than other examples". The detailed description includes specific details to provide an understanding of the described techniques. However, these techniques may be practiced without these specific details. In some examples, known structures and devices are shown in block diagram form to avoid making the concepts of the described examples unclear.

[0147] The description herein is provided to enable one of ordinary skill in the art to make or use the present disclosure. Various modifications of the present disclosure should be apparent to one of ordinary skill in the art, and the general principles defined herein may be applied to other variations without departing from the scope of the present disclosure. Therefore, the present disclosure is not limited to the examples and designs described herein, but is given the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A device for wireless communication, comprising: processor; and a memory coupled to the processor, the processor being configured to: Transmitting first signaling to request registration with a first network slice; receiving second signaling indicating registration with the first network slice and allowing registration with an alternative network slice; and Transmit third signaling to establish a first protocol data unit (PDU) session on the first network slice.

2. The apparatus of claim 1, wherein the processor is configured to identify that the alternative network slice does not exist in configured network slice selection assistance information (NSSAI).

3. An apparatus according to claim 1 or 2, wherein the processor is configured to transmit fourth signaling indicating that the apparatus supports the ability to register with the alternative network slice.

4. The apparatus of claim 1 , 2 or 3, wherein the processor is configured to: receiving fourth signaling indicating re-establishment of the first PDU session on the alternative network slice based at least in part on unavailability of the first network slice; and Fifth signaling is transmitted to request registration with the alternative network slice based at least in part on the inability to identify the alternative network slice.

5. The apparatus of claim 4, wherein the processor is configured to: receiving sixth signaling indicating acceptance of the registration and configuring network slice selection assistance information NSSAI to include an identifier of the alternative network slice, the alternative network slice being mapped to the first network slice; and Indicate establishment of a second PDU session on the alternative network slice, the second PDU session using the same routing descriptor as the first PDU session based at least in part on the alternative network slice mapped to the first network slice.

6. An apparatus according to claim 4 or 5, wherein the processor is configured to transmit the fifth signaling to request the registration to the alternative network slice based at least in part on determining that there is no identified alternative network slice for reestablishing the first PDU session.

7. A device for wireless communication, comprising: processor; and a memory coupled to the processor, the processor being configured to: receiving first signaling as a registration request from a user equipment UE to register with a first network slice; and Second signaling is transmitted indicating acceptance of the registration and allowing the UE to register with the alternative network slice.

8. The apparatus of claim 7, wherein the processor is configured to identify that the alternative network slice is not present in configured network slice selection assistance information (NSSAI).

9. An apparatus according to claim 7 or 8, wherein the processor is configured to receive third signaling from the UE indicating that the UE supports the ability to register with the alternative network slice.

10. An apparatus according to claim 7, 8 or 9, wherein the processor is configured to transmit a third signaling to a network function that serves a first protocol data unit (PDU) session established on the first network slice, the third signaling including an indication that the first PDU session can be established on an alternative network slice.

11. An apparatus according to any one of claims 7 or 10, wherein the processor is configured to receive a third signaling from the UE as an additional registration request to register with the alternative network slice in response to having signaled the UE to reestablish a first protocol data unit (PDU) session based at least in part on the UE's inability to identify the alternative network slice.

12. The apparatus of claim 11, wherein the processor is configured to: transmitting, to the UE, fourth signaling indicating that the registration is accepted and that the configured network slice selection assistance information NSSAI includes an identifier of the alternative network slice, the alternative network slice being mapped to the first network slice; and Receiving fifth signaling indicating that the UE has established a second PDU session using the same routing descriptor as the first PDU session based at least in part on the alternative network slice mapped to the first network slice.

13. A method comprising: receiving first signaling as a registration request from a user equipment UE to register with a first network slice; and Second signaling is transmitted indicating acceptance of the registration and allowing the UE to register with the alternative network slice.

14. The method of claim 13, wherein the alternative network slice is not identified in configured network slice selection assistance information (NSSAI).

15. The method according to claim 13 or 14, further comprising: Third signaling is received from the UE indicating that the UE supports the ability to register with the alternative network slice.

16. The method of claim 13, 14 or 15, further comprising: A third signaling is transmitted to a network function servicing a first protocol data unit (PDU) session established on the first network slice, the third signaling including an indication that the first PDU session may be established on an alternative network slice.

17. The method according to any one of claims 13 to 16, further comprising: In response to having signaled the UE to reestablish a first protocol data unit (PDU) session, third signaling is received from the UE as an additional registration request to register with the alternative network slice based at least in part on the UE being unable to identify the alternative network slice.

18. The method according to claim 17, further comprising: transmitting, to the UE, fourth signaling indicating that the registration is accepted and that the configured network slice selection assistance information NSSAI includes an identifier of the alternative network slice, the alternative network slice being mapped to the first network slice; and Receiving fifth signaling indicating that the UE has established a second PDU session using the same routing descriptor as the first PDU session based at least in part on the alternative network slice mapped to the first network slice.

19. The method of claim 18, wherein if the UE is not roaming, mapping the alternative network slice to the first network slice based on the NSSAI.

20. The method of claim 18, wherein if the UE is roaming, the alternative network slice is mapped to the first network slice based on a home public land mobile network (HPLMN) NSSAI.

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