Network slice replacement initiated by access and mobility management functions

Abstract

Aspects of the present disclosure relate to network slice replacement initiated by an access and mobility management function (AMF). An apparatus determines that a first network slice is no longer available and may be replaced with a second network slice, and sends a configuration update to a user equipment (UE) registered with the first network slice. The configuration update includes a mapping of the second network slice to the first network slice. In one embodiment, a UE receives a configuration update to change from a first network slice to a second network slice, the first network slice being used for one or more protocol data unit (PDU) sessions, and the UE sends a new PDU session establishment request on the second network slice based on a determination by the UE to establish a new PDU session.

Description

[0001] Related Applications

[0002] This application claims priority to U.S. patent application serial number 63 / 395,436, filed on August 5, 2022, entitled “Exchanging a Network Slice Initiated by an Access and Mobility Management Function,” the disclosure of which is incorporated herein by reference in its entirety. Technical Field

[0003] The present disclosure relates to wireless communications, and more particularly to replacing (e.g., switching, updating, modifying) network slices. Background Art

[0004] 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 for one or more user communication devices, which may be further referred to as a 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 (e.g., symbols, time slots, subframes, frames, etc.) or frequency resources (e.g., subcarriers, carriers). Additionally, a wireless communication system may support wireless communication across various radio access technologies, including third generation (3G) radio access technology, fourth generation (4G) radio access technology, fifth generation (5G) radio access technology, and other suitable radio access technologies other than 5G (e.g., sixth generation (6G)).

[0005] Network slicing enables network operators to divide the network into fine-grained "slices" to provide customized network connectivity or features for customer devices and / or external service providers. A network slice is a logical network that has a set of network functions and corresponding resources (e.g., computing, storage, networking) to provide certain network capabilities and network characteristics. A network slice may include core network control plane and user plane network functions, as well as an access network (e.g., a 5G radio access network or a fixed access network). The 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

[0006] The present disclosure relates to methods, devices, and systems for supporting network slice replacement initiated by an access and mobility management function (AMF). By utilizing the described techniques, a first network slice can be replaced with a second network slice, such as when the AMF determines that the first network slice (S-NSSAI-1) is no longer available and can be replaced with a second network slice (S-NSSAI-2). The AMF sends a configuration update to a UE registered with the first network slice, and the configuration update includes a mapping of the second network slice to the first network slice. The UE receives a configuration update to change from a first network slice to a second network slice, the first network slice is currently used for one or more PDU sessions, and the configuration update includes a mapping of the second network slice to the first network slice. Based on the UE's determination to establish a new PDU session, the UE sends a new PDU session establishment request on the second network slice.

[0007] By performing the various aspects of the described AMF-initiated network slice replacement, upon determining that the first network slice becomes unavailable and the new second network slice is not part of the S-NSSAI and / or configured NSSAI to which the UE is subscribed (i.e., is not part of the URSP rules, and therefore, the second network slice cannot be used by the UE for PDU session establishment), the AMF triggers the UE network slice reconfiguration. The AMF provides a new configured NSSAI, including the second network slice, and corresponding mapping information of the second network slice (S-NSSAI-2) to the first network slice (S-NSSAI-1) (in the non-roaming case) or the Home Public Land Mobile Network (HPLMN) S-NSSAI (in the roaming case) to allow the UE to continue to use one or more URSP rules. The configured and / or allowed NSSAI mapping information of S-NSSAI-2 to S-NSSAI-1 (or to HPLMN S-NSSAI) is used to configure the UE to start using the PDU session on the second network slice instead of the first network slice. A further benefit is that the AMF first configures the UE to use the alternative second network slice via a NAS MM procedure, and thereafter the AMF triggers a Session Management (SM) procedure to the Session Management Function (SMF) to release the old PDU session. This allows the UE to immediately trigger a new PDU session establishment without the need to perform a NAS MM procedure.

[0008] In some implementations of the methods and apparatus described herein, the AMF determines that a first network slice is no longer available and can be replaced with a second network slice. The AMF sends a first signaling indicating a configuration update to a UE registered with the first network slice, and the configuration update includes a mapping of the second network slice to the first network slice.

[0009] Some implementations of the methods and devices described herein may also include that the second network slice is not a network slice subscribed by the UE and is not identified in the configured NSSAI. The configuration update to the UE includes an updated configured NSSAI, or an allowed configured NSSAI, which includes a mapping of the second network slice to the first network slice. The AMF sends a second signaling to the network session management function, the second signaling explicitly indicating the release of one or more protocol data unit (PDU) sessions associated with the first network slice. The AMF receives a second signaling from the UE on the second network slice as a PDU session establishment request. The PDU session establishment request includes a mapping of the second network slice to the first network slice, and the device does not send the mapping to the network session management function. The AMF sends a second signaling to the network data management function based at least in part on determining that the first network slice is no longer available, the second signaling indicates a request to replace the first network slice with the second network slice, and receives a third signaling from the network data management function, the third signaling identifying the second network slice that will replace the first network slice. The second signaling of the network data management function initiates the network data management function to perform a network slice subscription update procedure.

[0010] In some implementations of the methods and apparatus described herein, a UE receives first signaling indicating a configuration update to change from a first network slice to a second network slice, the first network slice being used for one or more PDU sessions, and the configuration update including a mapping of the second network slice to the first network slice. The UE sends second signaling as a new PDU session establishment request on the second network slice based at least in part on a determination by the apparatus to establish a new PDU session.

[0011] Some implementations of the methods and apparatus described herein may also include the UE identifying that the second network slice does not exist in the configured NSSAI. The UE releases one or more PDU sessions based on the received configuration update to change from the first network slice to the second network slice. The UE implicitly releases the one or more PDU sessions without subsequent signaling. After establishing the new PDU session, the UE releases the one or more PDU sessions. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 An example of a wireless communication system supporting network slice replacement initiated by AMF according to various aspects of the present disclosure is illustrated.

[0013] Figure 2 An example 5GS architecture for a UE associated with two network slices supporting network slice replacement initiated by an AMF in accordance with various aspects of the present disclosure is illustrated.

[0014] Figure 3A and Figure 3BAn example of a signaling flow diagram 300 for an AMF to determine to reconfigure a UE with an alternative second network slice, the UE supporting network slice replacement initiated by the AMF, is illustrated in accordance with various aspects of the present disclosure.

[0015] Figure 4 and Figure 5 An example of a block diagram of a device supporting network slice replacement initiated by AMF according to various aspects of the present disclosure is illustrated.

[0016] Figures 6 to 9 A flowchart of a method for supporting network slice replacement initiated by AMF according to various aspects of the present disclosure is illustrated. DETAILED DESCRIPTION

[0017] The network operator 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 that has a set of network functions and corresponding resources (e.g., computing, storage, networking) to provide certain 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 configuration information NSSAI, which may include a single or multiple S-NSSAIs (single NSSAI).

[0018] A network slice being used by a UE may be changed to another network slice (e.g., slice remapping), such as during UE mobility due to lack of support for a first network slice in a target cell, or due to resource limitations of the first network slice in a 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 on 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 an alternative network slice, which is replaced with the first network slice. Another conventional technique suggests that the SMF communicate the alternative network slice to the UE in NAS 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 the various aspects of the disclosure described, there are multiple scenarios about how an alternative network slice or a second network slice (S-NSSAI-2) is related to the (multiple) S-NSSAI list to which the UE subscribes, which is stored in the UE subscription data and UE context in the AMF. In the first scenario, the second network slice is part of the subscribed S-NSSAI and is already part of the allowed NSSAI. In the second scenario, the second network slice is part of the subscribed S-NSSAI, but not part of the allowed NSSAI, and the second network slice can be added to the allowed NSSAI because the second network slice is supported in the current tracking area (TA). In the third scenario, the second network slice is part of the subscribed S-NSSAI, but the second network slice cannot be added to the allowed NSSAI because the second network slice is not supported in the UE current TA or is rejected for another reason (e.g., due to NSSAI failure). A new alternative network slice (S-NSSAI) is then needed, which may not be part of the subscribed S-NSSAI. In the fourth scenario, the second network slice is not part of the subscribed S-NSSAI and the configured NSSAI (in non-roaming case), or is not part of the configured NSSAI (in roaming case). The UE cannot request and use the second network slice (S-NSSAI-2) unless the second network slice is not part of the UE's configured NSSAI.

[0020] By performing the various aspects of the described AMF-initiated network slice replacement, upon determining that the first network slice becomes unavailable and the new second network slice is not part of the S-NSSAI and / or configured NSSAI to which the UE is subscribed (i.e., is not part of the URSP rules, and therefore, the second network slice cannot be used by the UE for PDU session establishment), the AMF triggers the UE network slice reconfiguration. The AMF provides the new configured NSSAI, including the second network slice, and the corresponding mapping information of the second network slice (S-NSSAI-2) to the first network slice (S-NSSAI-1) (in the non-roaming case) or the HPLMN S-NSSAI (in the roaming case), to allow the UE to continue to use one or more URSP rules. The configured and / or allowed NSSAI mapping information of S-NSSAI-2 to S-NSSAI-1 (or to HPLMN S-NSSAI) is used to configure the UE to start using the PDU session on the second network slice instead of the first network slice. A further benefit is that the AMF first configures the UE to use the alternative second network slice via the NAS MM procedure, and thereafter, the AMF triggers the SM procedure to the SMF to release the old PDU session. This allows the UE to immediately trigger a new PDU session establishment without the need to perform the NAS MM procedure.

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

[0022] Figure 1 An example of a wireless communication system 100 supporting network slice replacement initiated by an AMF according to various 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 the 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 other than 5G. Additionally, 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 radio access network (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 connection or a wired connection. For example, the network entity 102 and the UE 104 may perform wireless communication (e.g., receive signaling, send signaling) via a Uu interface.

[0024] The network entity 102 may provide a geographic coverage area 112 for which the network entity 102 may support services (e.g., voice, video, packet data, messaging, broadcast, etc.) for one or more UEs 104 within the geographic coverage area 112. For example, the network entity 102 and the UE 104 may support wireless communications of signals associated with services (e.g., voice, video, packet data, messaging, broadcast, etc.) according to one or more radio access technologies. In some implementations, the network entity 102 may be mobile, for example, 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. The information and signals described herein may be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referenced throughout the description may be represented by voltage, current, electromagnetic waves, magnetic fields or magnetic particles, optical 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 term. In some implementations, UE 104 may be referred to as a unit, a station, a terminal, or a client, etc. 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, etc. In some implementations, UE 104 may be stationary 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 of different forms or with different capabilities. Figure 1 Some examples of UE 104 are illustrated in FIG. UE 104 may be able to communicate with various types of devices, such as network entity 102, other UEs 104, or network devices (e.g., core network 106, packet data network 108, relay device, integrated access and backhaul (IAB) node, or another network device), such as Figure 1 Additionally or alternatively, the UE 104 can support communications with other network entities 102 or UEs 104 that can act as relays in the wireless communication system 100 .

[0027] The UE 104 may also be capable of supporting wireless communications directly with other UEs 104 via a communication link 114. For example, the UE 104 may support wireless communications directly with another UE 104 via a device-to-device (D2D) communication link. In some implementations, such as vehicle-to-vehicle (V2V) deployments, vehicle-to-everything (V2X) deployments, or cellular V2X deployments, the communication link 114 may be referred to as a side link. For example, the UE 104 may support wireless communications 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 directly with each other (e.g., between the network entities 102). In some other implementations, the network entities 102 may communicate indirectly with each other (e.g., via the core network 106). In some implementations, one or more network entities 102 may include subcomponents, such as an access network entity, which may be an example of an access node controller (ANC). 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 transmission reception points (TRPs).

[0029] In some implementations, the network entity 102 may be configured with a disaggregated architecture that 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 transmission reception point (TRP). One or more components of the network entity 102 in the disaggregated 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 disaggregated RAN architecture may be implemented as virtual units (e.g., virtual CU (VCU), virtual DU (VDU), virtual RU (VRU)).

[0031] The functional split between the CU, DU, and RU can be flexible, and different functionalities can be supported 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 split 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)) functionality 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) functionality and signaling, and the one or more DUs or RUs can each be at least partially controlled by the CU.

[0032] Additionally or alternatively, a functional split 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 split between the CU and the DU, or between the DU and the RU may be within the protocol layer (e.g., some functions for the protocol layer may be performed by one of the CU, DU, or RU, while other functions of the protocol layer are performed by another of the CU, DU, or RU).

[0033] The CU may be further functionally split into CU control plane (CU-CP) functionality and CU user plane (CU-UP) functionality. The CU may be connected to one or more DUs via a midhaul communication link (e.g., F1, F1c, F1u), and the DU may be connected to one or more RUs via a fronthaul communication link (e.g., an open fronthaul (FH) interface). In some implementations, a midhaul communication link or a fronthaul communication link may be implemented based on an interface (e.g., a channel) between layers of a protocol stack supported by a corresponding network entity 102 communicating via such a communication link.

[0034] The core network 106 may support user authentication, access authorization, tracking, connectivity, 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., mobility management entity (MME), access and mobility management function (AMF)) and user plane entities that route packets or interconnects to external networks (e.g., serving gateway (S-GW), packet data network (PDN) gateway (P-GW), or user plane function (UPF)). In some implementations, the control plane entities may manage NAS functions, such as mobility, authentication, and bearer management (e.g., data bearers, signal bearers, etc.) for one or more UEs 104 served by one or more network entities 102 associated with the core network 106.

[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, etc.) with the core network 106 via the network entity 102. The core network 106 may use the established session (e.g., the established PDU session) to route traffic (e.g., control information, data, etc.) between the UE 104 and the application server 118. The PDU session may be an example of a logical connection between the 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, such as time resources (e.g., symbols, time slots, subframes, frames, etc.) 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, such as in 4G, the network entity 102 and the UE 104 may support a single frame structure. In some other implementations, such as in 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 digital schemes.

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

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

[0039] Additionally or alternatively, the time intervals of resources (e.g., communication resources) can be organized according to time slots. For example, a subframe may include a certain number (e.g., amount) of time slots. Each time slot may include a certain number (e.g., amount) of symbols (e.g., orthogonal frequency division multiplexing (OFDM) symbols). In some implementations, the number of time slots (e.g., amount) for a subframe may depend on a digital scheme. 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. For a normal cyclic prefix and an extended cyclic prefix, 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 may depend on a digital scheme. It should be understood that references to a first digital scheme (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 split into various categories, frequency bands, frequency channels, etc. based on frequency or wavelength. By way of example, the wireless communication system 100 may support one or more operating frequency bands, such as the frequency range names 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 frequency 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 services (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 digital schemes (e.g., at least three digital schemes). For example, FR1 may be associated with a first digital scheme (e.g., μ=0) including a subcarrier spacing of 15 kHz; a second digital scheme (e.g., μ=1) including a subcarrier spacing of 30 kHz; and a third digital scheme (e.g., μ=2) including a subcarrier spacing of 60 kHz. FR2 may be associated with one or more digital schemes (e.g., at least 2 digital schemes). For example, FR2 may be associated with a third digital scheme (e.g., μ=2) including a subcarrier spacing of 60 kHz; and a fourth digital scheme (e.g., μ=3) including a subcarrier spacing of 120 kHz.

[0042] Depending on the implementation, one or more of the network entity 102 (to include the access network), the UE 104, the AMF 120, and / or the SMF may be operable to implement various aspects of a network slice replacement initiated by the AMF, as described herein. For example, the AMF 120 determines that a first network slice is no longer available and can be replaced with a second network slice, and the AMF sends a network slice configuration update 122 to the UE 104 registered with the first network slice. In the implementation, the network slice configuration update 122 includes a mapping of the second network slice to the first network slice. The UE 104 receives the network slice configuration update 122 from the AMF 120 (via the network entity 102), the configuration update 122 indicating a change from the first network slice to the second network slice, the first network slice being used for one or more PDU sessions. Then, based on the UE's determination to establish a new PDU session, the UE sends a new PDU session establishment request 124 on the second network slice, which is received by the AMF 120.

[0043] In general, the UE requests registration for a network slice by communicating a NAS registration request message to the 5GC (e.g., AMF), the NAS registration request message including the requested NSSAI, which contains a list of one or more S-NSSAIs with which the UE wants to register. The AMF communicates one or more elements related to the UE's network slice configuration to the UE in a registration accept message or a UE configuration update command message, such as allowed NSSAI, configured NSSAI, rejected NSSAI, or pending NSSAI. NSSAI is a list of one or more S-NSSAIs.

[0044] Figure 2An example 5GS architecture 200 for a UE associated with two network slices, the UE supporting network slice replacement initiated by an AMF, in accordance with various aspects of the present disclosure is illustrated. The UE is associated with two network slices, which are 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 the example architecture 200, a (radio) access network ((R)AN) is part of the two network slices and is shared. 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 network functions (NFs) belonging to NSI-2. Note that the example 5GS architecture 200 does not show or include all network functions (e.g., AMF, network slice selection function (NSSF), SMF, UPF, etc.) or all reference points.

[0045] Support for network slice service continuity during UE mobility due to lack of support for network slices or due to resource limitations of the network slices in the target RAN node is considered. These scenarios may arise due to the fact that the network slice does not need to be available in all tracking areas (TAs) of the network. In various aspects of the present disclosure, non-mobility scenarios (or events) and mobility scenarios (or events) in the network are considered, which result in changes in network slices. For non-mobility 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. Mobility scenarios are considered, particularly in the case of inter-registration area (RA) mobility where the network slice (or network slice instance) in the target CN is overloaded.

[0046] Various 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 a possible alternative S-NSSAI is not part of the S-NSSAI to which the UE subscribes (stored in the UE context in the AMF), the alternative S-NSSAI is also not part of the NSSAI and URSP rules configured by the UE. The UE cannot request registration for an alternative S-NSSAI. Various 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. Further, various aspects of the present disclosure consider how to ensure that an 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, the network slice change is called slice remapping, such as 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 RAN node. 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 on 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 an alternative network slice, which is replaced with the first network slice. Another conventional technique suggests that the SMF communicates 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 various aspects of the disclosure described, there are multiple scenarios on how an alternative network slice or second network slice (S-NSSAI-2) is related to the (multiple) S-NSSAI lists to which the UE subscribes, which are stored in the UE subscription data and UE context in the AMF. The various scenarios may include: a) S-NSSAI-2 is part of the subscribed S-NSSAI and is already part of the allowed NSSAI; 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 tracking area (TA); c) S-NSSAI-2 is part of the subscribed S-NSSAI, but S-NSSAI-2 cannot be added to the allowed NSSAI because S-NSSAI-2 is not supported in the UE current TA or is rejected for another reason (e.g., due to NSSAA failure). A new alternative S-NSSAI is then required, which may not be part of the subscribed S-NSSAI; and d) S-NSSAI-2 is not part of the subscribed S-NSSAI and the configured NSSAI (in non-roaming case), or is not part of the configured NSSAI (in roaming case). The UE cannot request and use S-NSSAI-2 unless S-NSSAI-2 is not part of the UE's configured NSSAI.

[0049] Various aspects of the present disclosure describe how the network slice S-NSSAI-2 can replace the network slice S-NSSAI-1 in the above scenarios, in particular in scenario d) covering scenario c). In scenarios a) and b), it is assumed that the alternative S-NSSAI-2 that will replace the S-NSSAI-1 is part of the S-NSSAI to which the UE subscribes. Therefore, if S-NSSAI-2 is allowed to be used for application data services, the alternative S-NSSAI-2 will be configured in the UE URSP rules, in particular in the URSP rules for establishing the current (multiple) PDU sessions on S-NSSAI-1. Therefore, the SMF does not need to indicate any alternative S-NSSAI-2 to the UE in the NAS SM signaling for PDU session release.

[0050] Various aspects of the present disclosure direct the AMF to determine an alternative S-NSSAI-2 that is supported in the current tracking area and that will replace the S-NSSAI-1, and the AMF determines that the S-NSSAI-2 is not part of the S-NSSAI to which the UE is subscribed and / or the configured NSSAI for the current PLMN. If the AMF is located in the HPLMN and the AMF determines that the S-NSSAI-2 should replace the S-NSSAI-1 for a relatively long period of time (or always), the AMF indicates to the UDM that the list of subscribed S-NSSAIs should change. The UDM triggers known procedures for network slice subscription changes in order to update the UE and the rest of the 5GS. If the AMF determines that the S-NSSAI-2 should replace the S-NSSAI-1, such as on a temporary basis or for a relatively short period of time, the AMF determines to apply the S-NSSAI mapping feature for the UE network slice configuration (i.e., the S-NSSAI-2 is mapped to the S-NSSAI-1 and is sent to the UE in the configured NSSAI and / or the allowed NSSAI).

[0051] After S-NSSAI-2 is part of the allowed NSSAI and the mapping information includes mapping S-NSSAI-2 to S-NSSAI-1, the UE uses S-NSSAI-2 for each current PDU session (multiple) of the PDU sessions established on S-NSSAI-1 to automatically initiate a new (multiple) PDU session establishment procedure. The AMF receives a PDU session establishment request message including S-NSSAI-2 and the mapping information of S-NSSAI-2 to S-NSSAI-1, and the AMF determines to remove the mapping message of S-NSSAI-2 to S-NSSAI-1 before forwarding the message to the SMF selected for S-NSSAI-2. When S-NSSAI-1 can be used by the UE again, the AMF creates a configured NSSAI to delete the mapping information of S-NSSAI-2 to S-NSSAI-1, and the AMF triggers a UE configuration update (UCU) procedure to send the updated configured NSSAI to the UE.

[0052] As described herein, the term "alternative" S-NSSAI feature (or "compatible" S-NSSAI feature) means functionality supported by the network and the UE in which a first S-NSSAI for a PDU session may be replaced with another (second) S-NSSAI, wherein the second S-NSSAI may or may not be included in the NSSAI configured for the UE. In implementation, the second S-NSSAI is not part of the NSSAI configured for the UE, and therefore, the network determines and configures the UE with a second S-NSSAI that (a) replaces the first S-NSSAI (e.g., in a roaming case) or (b) maps to the first S-NSSAI (e.g., in a non-roaming case). Additionally, the second S-NSSAI replaces the first S-NSSAI-1 in the network (e.g., the first S-NSSAI-1 is waiting to be replaced or replaced with the second S-NSSAI-2). Assume that the UE has established a PDU session and due to an event, the current PDU session must be transferred from the first network slice (S-NSSAI-1) to the second network slice (S-NSSAI-2).

[0053] Figure 3A and Figure 3B An example of a signaling flow diagram 300 for supporting a network slice replacement initiated by an AMF according to various aspects of the present disclosure is illustrated. The example signaling flow diagram 300 illustrates that the AMF determines to reconfigure the UE with an alternative second S-NSSAI (e.g., S-NSSAI-2) by using network slice mapping information. SMF1 302 is part of a network slice identified by S-NSSAI-1, and SMF2 304 is part of a network slice identified by S-NSSAI-2.

[0054] In the example signaling flow diagram 300, the UE requests registration with the network (at step 0a), in particular, with the first network slice (e.g., S-NSSAI-1). The UE initiates (at step 0b) establishment of a PDU session on S-NSSAI-1, and SMF1 302 is selected by the AMF 120 as the serving SMF for the PDU session. The AMF determines (at step 1) that (a) S-NSSAI-1 becomes unavailable and / or (b) an alternative S-NSSAI (e.g., S-NSSAI-2) can be used to replace S-NSSAI-1. The reason why S-NSSAI-1 becomes unavailable may be due to a non-mobility event (e.g., operations, administration, and maintenance (OAM) or NSSF / NF reconfiguration, or S-NSSAI-1 will be down for network maintenance); or a UE mobility event (e.g., T-AMF does not support S-NSSAI-1).

[0055] The AMF processes the determined alternative S-NSSAI (e.g., S-NSSAI-2) for the UE's network slice configuration (i.e., configured NSSAI, allowed NSSAI, rejected NSSAI). Note that the UE context in the AMF may contain multiple lists of rejected NSSAIs (e.g., rejected NSSAI for the current PLMN or Standalone Non-Public Network (SNPN), rejected NSSAI for the current registration area, rejected NSSAI for failed or revoked NSSAA, or rejected NSSAI for the maximum number of UEs reached). If the AMF determines that S-NSSAI-2 is part of the S-NSSAI subscribed to by the UE or part of the configured NSSAI, but S-NSSAI-2 is part of the rejected NSSAI for failed or revoked NSSAI or the rejected NSSAI for the maximum number of UEs reached (or other types of rejected NSSAI), the AMF determines another alternative S-NSSAI (e.g., S-NSSAI-3). This allows the UE to start using S-NSSAI-3 immediately. Additionally, the AMF may determine whether the alternative S-NSSAI (e.g., S-NSSAI-2 or S-NSSAI-3) is used as an alternative only for a limited time or permanently (i.e., for a relatively long time), which will lead to a decision on whether to apply step 2a or step 3a.

[0056] If the AMF is in the HPLMN and the AMF determines (at step 2a) that (i) S-NSSAI-2 should replace S-NSSAI-1 for a relatively long period of time (or always) or (ii) S-NSSAI-2 will be included in addition to the list of subscribed S-NSSAIs, the AMF determines to indicate to the UDM 306 that the list of subscribed S-NSSAIs should be updated (e.g., indicating that S-NSSAI-2 should replace S-NSSAI-1, or should include S-NSSAI-2 in addition) (further description is provided below with reference to step 3a). The UDM (at step 2b) internally updates (and / or further indicates to the unified data repository (UDR)) that the list of subscribed S-NSSAIs of the UE should be updated to include S-NSSAI-2 instead of S-NSSAI-1. The UDM triggers a procedure for network slice subscription update to update the UE configuration and configuration in other network functions (NFs) in the 5GS (e.g., serving AMF, etc.). By updating the list of subscribed S-NSSAIs, the Policy Control Function (PCF) that creates the UE policy should create new UE Routing Policy (URSP) rules, and the new policy rules should include the NSSP regarding how application data traffic can be mapped to S-NSSAI-2.

[0057] If the AMF (optionally together with the NSSF and / or OAM system) determines (at step 3a) at least one of the following conditions: i) S-NSSAI-2 (or S-NSSAI-3) is not part of the S-NSSAI to which the UE is subscribed or part of the configured NSSAI; ii) S-NSSAI-2 should be applied temporarily (i.e., for a limited time or within a limited area); and / or iii) one or more PDU sessions currently established on S-NSSAI-1 are not active (e.g., user plane resources (such as N3 tunnels) are not activated); then the AMF determines to configure the UE as follows: (1) in non-roaming case, add S-NSSAI-2 to the configured NSSAI (and in the allowed NSSAI), and additionally, add a network slice mapping to configure the UE to map S-NSSAI-2 to S-NSSAI-1, where S-NSSAI-1 acts as the HPLMN S-NSSAI value; (2) in roaming case, S-NSSAI-2 replaces S-NSSAI-1 in the configured NSSAI (and allowed NSSAI), and the mapping information includes the mapping of S-NSSAI-2 to HPLMN S-NSSAI (i.e., replacing the mapping of S-NSSAI-1 to HPLMN S-NSSAI).

[0058] The above condition i) is the result of processing the determined alternative S-NSSAI (e.g., S-NSSAI-2 or S-NSSAI 3) for the list of S-NSSAIs subscribed by the UE and the configured NSSAI. If the determined alternative S-NSSAI (e.g., S-NSSAI-2 or S-NSSAI 3) is not part of the S-NSSAI subscribed by the UE, the 5GS includes the alternative S-NSSAI in the S-NSSAI subscribed by the UE (step 2a), or the AMF performs the UE network slice reconfiguration procedure to update the configured NSSAI in the UE. In the latter case, no URSP rule update is required (e.g., contrary to steps 2a / 2b).

[0059] The above condition ii) is a decision point as to whether the AMF performs step 2a or step 3a. If the alternative S-NSSAI (e.g., S-NSSAI-2) is applied under limited conditions (such as a limited time or a limited area), the AMF determines to perform the UE network slice reconfiguration procedure. If S-NSSAI-2 is to be applied permanently (or semi-permanently) with respect to time or location area, the AMF determines to perform step 2a. The above condition iii) expresses the time point as to when the AMF triggers the UE network slice reconfiguration procedure. Before initiating the UE network slice reconfiguration procedure, the AMF may wait until the (multiple) PDU sessions established on S-NSSAI-1 are inactive (e.g., UP resources are not established). This will allow the UE to establish a new PDU session and terminate the current PDU session, and no user data traffic will be sent over the (multiple) PDU sessions.

[0060] If the NSSF is responsible for determining the configured NSSAI, allowed NSSAI, and / or rejected NSSAI, the AMF sends a request message to the NSSF, and the request includes an indication that an alternative S-NSSAI for S-NSSAI-1 is required. This new indication is sent in addition to the usual parameters (or information elements) as part of the Nnssf_NSSelection_Get request service operation from the AMF to the NSSF (e.g., parameters such as the subscribed S-NSSAI, the current tracking area identifier (ID), etc.). Based on the received request indicating that an alternative S-NSSAI for S-NSSAI-1 is required, the NSSF determines S-NSSAI-2 as an alternative network slice for replacing S-NSSAI-1. The NSSF also creates new configured NSSAI and / or allowed NSSAI (e.g., including S-NSSAI-2) and associated mapping information from S-NSSAI-2 to S-NSSAI-1, and sends it to the AMF.

[0061] The AMF triggers the UCU procedure (at step 3b), where the AMF includes the new configured NSSAI, which contains S-NSSAI-2 and additional mapping information of S-NSSAI-2 to S-NSSAI-1. The AMF may also send a new allowed NSSAI with the corresponding mapping of the allowed NSSAI information (including the mapping of S-NSSAI-2-to S-NSSAI-1). This is valid for non-roaming cases, and an example for the configured NSSAI (which also applies by analogy to the allowed NSSAI) is as follows: Old configured NSSAI: S-NSSAI-1; Mapping of configured NSSAI: None. New configured NSSAI: S-NSSAI-2; Mapping of configured NSSAI: S-NSSAI-2 to S-NSSAI-1.

[0062] For roaming cases, where S-NSSAI-1 is used in the serving Visited Public Land Mobile Network (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. Examples of configured NSSAIs (also similar to the allowed NSSAI application) for roaming cases are as follows: Old configured NSSAI: S-NSSAI-1; Mapping of configured NSSAI: S-NSSAI-1 to HPLMN S-NSSAI. New configured NSSAI: S-NSSAI-2; Mapping of configured NSSAI: S-NSSAI-2 to HPLMN S-NSSAI. Note that the AMF (and / or NSSF) may determine to provide only the updated allowed NSSAI to the UE (i.e., without updating the configured NSSAI). This is beneficial in cases where the alternative S-NSSAI should only be applied to ongoing network registrations (e.g., only in the current registration area). If the configured NSSAI is not updated, the UE will request to use the old S-NSSAI (e.g., S-NSSAI-1) again when performing a new registration procedure.

[0063] If the UE receives a new configured NSSAI without an allowed NSSAI in step 3b, the UE triggers a registration procedure (at step 4a) to register with one or more network slices including S-NSSAI-2. The UE sends a registration request message including a requested NSSAI parameter (also called an information element (IE)) to the AMF, where the requested NSSAI includes at least S-NSSAI-2. The UE may also send the mapped or requested NSSAI to the HPLMN NSSAI value IE. After S-NSSAI-2 becomes part of the allowed NSSAI, the UE may start establishing a PDU session with S-NSSAI-2. The AMF receives the registration request message including the requested NSSAI, and (at step 4b) the AMF (optionally together with the NSSF and / or OAM system) determines the S-NSSAI (e.g., including S-NSSAI-2) that is supported in the UE's current TA and can be included in the allowed NSSAI. The AMF (and / or NSSF) determines to apply the mapping of S-NSSAI-2 to S-NSSAI-1. The AMF (and / or NSSF) creates a new allowed NSSAI and sends the allowed NSSAI to the UE in the Registration Accept message.

[0064] continue Figure 3BAccording to the signaling flow chart 300 in FIG. 3 , if there are one or more established PDU sessions on S-NSSAI-1, the AMF (at step 5a) determines to send a request to SMF1 to trigger the release of (multiple) PDU sessions. Note that although S-NSSAI-1 is still part of the mapped allowed NSSAI IE, the AMF triggers the PDU session release procedure. The AMF may include a new indication, i.e., explicit release signaling that needs to be communicated to the UE to indicate to the UE that the currently established PDU session may no longer be used. The AMF sends a request message to SMF1 (at step 5b) to indicate that the PDU session should be released. The AMF calls the Nsmf_PDUSession_ReleaseSMContext service operation to request the release 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, the AMF includes a new indication as explicit release signaling communicated to the UE.

[0065] The SMF determines to release the PDU session (at step 5c). The PDU session can be any session and service continuity (SSC) mode (e.g., SSC mode 1, SSC mode 2, or SSC mode 3). In the case of SSC mode 3, the SMF determines to send a PDU session modification request to the UE to re-establish the PDU session on an alternative S-NSSAI. The SMF releases the IP address and / or (multiple) prefixes assigned to the PDU session, and releases the corresponding user plane resources in the UPF using N4 signaling (not shown in the signaling flow chart). In the case of a PDU session in SSC mode 2, when the SMF wants the UE to re-establish the PDU session, the SMF includes a 5GSM cause #39 "reactivation request". The SMF creates an N1 SM container to be sent to the UE, which includes a PDU session release command or a PDU session modification request message, which includes a PDU session ID and a 5GSM cause value.

[0066] The SMF invokes the Namf_Communication_N1N2MessageTransfer service operation (N1 SM container, N2 information). If the UP connection for the PDU session is active, the SMF shall also include the N2 Resource Release Request (PDU Session ID) in the Namf_Communication_N1N2MessageTransfer to release the (R)AN resources associated with the PDU session. The UE confirms the receipt of the N1 SM container to the SMF. The SMF sends (at step 5d) a Nsmf_PDUSession_ReleaseSMContext response message to the AMF to indicate the successful release signaling to the UE.

[0067] Upon receiving a new allowed NSSAI including S-NSSAI-2 (i.e., without S-NSSAI-1) and mapping information of S-NSSAI-2 to S-NSSAI-1 (e.g., in step 3b or 4b), the UE performs (at step 6) at least one of the following a) and / or b). At a), the UE (automatically) triggers establishment of new (multiple) PDU sessions for user data traffic currently routed to S-NSSAI-1 (e.g., according to URSP rules with a routing descriptor (RSD) including S-NSSAI-1), but using S-NSSAI-2 from the allowed NSSAI. If there are established (multiple) PDU sessions on S-NSSAI-1, the UE immediately or automatically triggers the establishment of new (multiple) PDU sessions for each of the currently established (multiple) PDU sessions, where the same URSP rules and the same RSD can be used, but the new (multiple) PDU session is requested on S-NSSAI-2 and means replacing the old (multiple) PDU session on S-NSSAI-1. The stored (multiple) URSP rules (including the RSD containing S-NSSAI-1) are used to establish the PDU session on S-NSSAI-2, as indicated by the mapping of allowed NSSAI information (i.e., the mapping of S-NSSAI-2 to S-NSSAI-1). At b), the UE performs an implicit release of the old established (multiple) PDU session on S-NSSAI-1. After establishing a new PDU session over S-NSSAI-2, the UE releases the old established (multiple) PDU sessions, which will allow minimizing service disruption when changing network slices, as the UE can continue to send data over the old PDU sessions during the establishment of the new PDU sessions.

[0068] The UE triggers a new (multiple) PDU session establishment to S-NSSAI-2 (at step 7a), where the UE includes a mapping of S-NSSAI-2 and allowed NSSAI information (i.e., mapping information of S-NSSAI-2 to S-NSSAI-1) in a NAS message to the AMF. Note that this solution is applicable to both non-roaming and roaming scenarios (i.e., the mapping of allowed NSSAI information is also included in the PDU session establishment request in non-roaming scenarios). Since the PDU session is established on the new S-NSSAI (S-NSSAI-2), for PDU sessions of SSC mode 1 and SSC mode 2, the UE uses the request type "initial request" or the request type "already exists". If the UE uses the request type "already exists", the UE includes the old PDU session ID. If the UE does not provide the old PDU session ID and uses the request type "already exists", the AMF internally determines that the new PDU session on S-NSSAI-2 is associated with the PDU session on S-NSSAI-1. For PDU sessions in SSC mode 3, the UE uses request type "initial request" or "existing", which should not affect the AMF operation because the AMF shall select SMF in S-NSSAI-2.

[0069] The AMF selects a serving SMF for the new PDU session by using S-NSSAI-2 (at step 7b). The AMF selects SMF2 and forwards the UE request to SMF2 using the Nsmf_PDUSession_CreateSMContext request service operation. SMF2 continues the establishment of the PDU session as follows by using S-NSSAI-2: If SMF2 is in the UE HPLMN (i.e., non-roaming case), SMF2 uses the mapped S-NSSAI-1 value in the service operation of UDM to retrieve the UE SM subscription data. SMF2 does not use the mapped S-NSSAI-1 value as input to select another SMF in S-NSSAI-1. SMF2 acts as the anchor SMF for the PDU session. Further, if SMF2 is in the VPLMN for the UE (i.e., roaming case), SMF2 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 a home-routed PDU session. In this case, the PDU session establishment procedure for roaming scenarios will be applied, and SMF2 controls the intermediate UPF, and the SMF in the HPLMN serves the anchor UPF (i.e., an N9 tunnel is established between the intermediate UPF and the anchor UPF).

[0070] If the PDU session is used for Local Breakout (LBO), SMF2 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 calling the service operation with Subscriber Data Management (SDM), Nudm_SDM_Get request (including parameters such as Subscription Permanent Identifier (SUPI), Session Management Subscription Data, Selected Data Network Name (DNN), S-NSSAI (i.e., S-NSSAI-1) of the mapped S-NSSAI value, etc. The S-NSSAI of the mapped S-NSSAI value is also used for non-roaming scenarios. SMF2 confirms the establishment of the PDU session to the UE by sending a PDU Session Establishment Response (including the User Plane Configuration for the PDU Session Configuration).

[0071] After a period of time, the AMF may determine (at step 8) that S-NSSAI-1 can be used again. The AMF sends a UCU command to the UE (at step 9), including a new configured NSSAI and / or a new allowed NSSAI similar to step 3b. However, S-NSSAI-2 will be removed and S-NSSAI-1 will be included. In addition, the mapping of configured NSSAIs (e.g., including the mapping of S-NSSAI-2 to S-NSSAI-1) and the mapping of allowed NSSAIs (e.g., including the mapping of S-NSSAI-2 to S-NSSAI-1) are removed because they are no longer applicable. The UE initiates a new PDU session establishment to S-NSSAI-1 (at step 10). The UE sends a NAS message to the AMF, including the new PDU session ID (and optionally, an association with the old PDU session ID), S-NSSAI-1, DNN1, and N1 SM container (PDU session establishment request). In case of SSC mode 3, the UE also includes the old PDU session ID.

[0072] Note that the various aspects of the present disclosure described are also applicable to the scenario where the UE is registered with S-NSSAI-1 and there is no PDU session established on S-NSSAI-1. In this case, the network (e.g., AMF) triggers the UE network slice reconfiguration procedure by sending a new configured NSSAI and / or allowed NSSAI (with corresponding slice mapping information). When a new PDU session is to be established and associated with S-NSSAI-1 in a matching URSP rule, the UE uses the configured NSSAI and / or allowed NSSAI with an RSD associated with S-NSSAI-1 (or associated with the HPLMN S-NSSAI in the roaming case).

[0073] By performing the various aspects of the described AMF-initiated network slice replacement, upon determining that S-NSSAI-1 becomes unavailable and the new alternative S-NSSAI-2 is not part of the S-NSSAI subscribed to by the UE and / or the configured NSSAI (i.e., not part of the URSP rules, and therefore, S-NSSAI-2 cannot be used by the UE for PDU session establishment), the AMF triggers the UE network slice reconfiguration (steps 3a and 3b). The AMF sends the new configured NSSAI, including the alternative S-NSSAI-2 and the corresponding mapping information of S-NSSAI-2 to S-NSSAI-1 (in non-roaming case) or HPLMN S-NSSAI (in roaming case), so as to allow the UE to continue to use one or more URSP rules containing S-NSSAI-1 or HPLMN S-NSSAI. The configured and / or allowed NSSAI mapping information of S-NSSAI-2 to S-NSSAI-1 or HPLMN S-NSSAI is used to configure the UE to start using the PDU session on S-NSSAI-2 instead of S-NSSAI-1. A further benefit is that the AMF first configures the UE to use the alternative S-NSSAI-2 via the NAS MM procedure, and thereafter, the AMF triggers the SM procedure to the SMF to release the old PDU session. This allows the UE to immediately trigger a new PDU session establishment without the need to perform the NAS MM procedure.

[0074] Further, in the various aspects of the network slice replacement initiated by the AMF described, when the AMF determines that S-NSSAI-2 must replace S-NSSAI-1 and S-NSSAI-2 is not part of the S-NSSAI subscribed to by the UE, the AMF determines to configure the UE with network slice mapping information for mapping S-NSSAI-2 to S-NSSAI-1. If the AMF is located in the HPLMN and the AMF determines that S-NSSAI-2 should replace S-NSSAI-1 for a relatively long period of time (or always), the AMF indicates to the Unified Data Management (UDM) that the list of subscribed S-NSSAIs should be changed. Upon receiving a PDU session establishment request message including S-NSSAI-2 and mapping information of S-NSSAI-2 to S-NSSAI-1, the AMF determines to remove the mapping message of S-NSSAI-2 to S-NSSAI-1 before forwarding the message to the SMF selected for S-NSSAI-2. The AMF sends a request for an alternative S-NSSAI for S-NSSAI-1 to the NSSF and receives a corresponding reply.

[0075] Further, in the various aspects of the described network slice replacement initiated by the AMF, the UE receives a new allowed NSSAI with mapping information for S-NSSAI-2 mapping to S-NSSAI-1, and the UE determines to automatically trigger the establishment of a new (multiple) PDU session on S-NSSAI-2 for each of the (multiple) PDU sessions currently established on S-NSSAI-1. The UE also receives a new allowed NSSAI with mapping information for S-NSSAI-2 mapping to S-NSSAI-1, and the UE triggers an implicit release of the old established (multiple) PDU session on S-NSSAI-1. After establishing the new PDU session on S-NSSAI-2, the UE releases the old established (multiple) PDU session.

[0076] Further, in the various aspects of the described network slice replacement initiated by AMF, the NSSF receives a request from the AMF requiring an alternative S-NSSAI for S-NSSAI-1. The NSSF determines the alternative S-NSSAI (e.g., S-NSSAI-2) to be used to replace S-NSSAI-1. The NSSF creates the configured NSSAI, the allowed NSSAI, and the corresponding mapping information, which includes the mapped S-NSSAI-2 to S-NSSAI-1. The NSSF sends a reply to the AMF, including the alternative S-NSSAI (e.g., S-NSSAI-2) to be used to replace S-NSSAI-1.

[0077] Figure 4 An example of a block diagram 400 of a device 402 supporting network slice replacement initiated by an AMF according to various aspects of the present disclosure is illustrated. The device 402 may be an example of an AMF (or a network device implementing an AMF) described herein. The device 402 may support wireless communications with one or more network entities 102, UEs 104, or any combination thereof. The device 402 may include components for bidirectional communication, including components for sending communications and receiving communications, such as a processor 404, a memory 406, a transceiver 408, and an I / O controller 410. 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).

[0078] The processor 404, the memory 406, the transceiver 408, 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 404, the memory 406, the transceiver 408, or various combinations thereof or components thereof may support methods for performing one or more operations described herein.

[0079] In some implementations, the processor 404, memory 406, transceiver 408, or various combinations or components thereof may be implemented in hardware (e.g., in a communications management circuit system). 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 that is configured to or otherwise supports components for performing the functions described in the present disclosure. In some implementations, the processor 404 and the memory 406 coupled to the processor 404 may be configured to perform one or more functions described herein (e.g., by executing instructions stored in the memory 406 by the processor 404).

[0080] For example, according to the examples disclosed herein, the processor 404 may support wireless communication at the device 402. The processor 404 may be configured to or otherwise support components for: determining that a first network slice is no longer available and can be replaced with a second network slice; and sending a first signaling indicating a configuration update to a UE registered with the first network slice, the configuration update including a mapping of the second network slice to the first network slice.

[0081] Additionally, the processor 404 may be configured to or otherwise support any one or combination of the following items: the second network slice is not a network slice to which the UE subscribes, and the second network slice is not identified in the configured NSSAI. The configuration update to the UE includes an updated configured NSSAI, which includes a mapping of the second network slice to the first network slice. The configuration update to the UE includes an allowed NSSAI, which includes a mapping of the second network slice to the first network slice. The method also includes sending a second signaling to a network session management function, the second signaling explicitly indicating the release of one or more PDU sessions associated with the first network slice. The method also includes receiving a second signaling from the UE on the second network slice as a PDU session establishment request. The PDU session establishment request includes a mapping of the second network slice to the first network slice, and the device does not send the mapping to the network session management function. The method also includes sending second signaling to the network data management function based at least in part on determining that the first network slice is no longer available, the second signaling indicating a request to replace the first network slice with a second network slice; and receiving third signaling from the network data management function, the third signaling identifying the second network slice that will replace the first network slice. The second signaling to the network data management function initiates the network data management function to perform a network slice subscription update procedure.

[0082] Additionally or alternatively, according to the examples disclosed herein, device 402 may include an apparatus for wireless communication, including a processor; and a memory coupled to the processor, the processor being configured to determine that a first network slice is no longer available and can be replaced with a second network slice; and to send a first signaling indicating a configuration update for a UE registered with the first network slice, the configuration update including a mapping of the second network slice to the first network slice.

[0083] Additionally, the wireless communication at device 402 may include any one or a combination of the following items: the second network slice is not a network slice to which the UE subscribes, and the second network slice is not identified in the configured NSSAI. The configuration update to the UE includes an updated configured NSSAI, and the updated configured NSSAI includes a mapping of the second network slice to the first network slice. The configuration update to the UE includes an allowed NSSAI, and the allowed NSSAI includes a mapping of the second network slice to the first network slice. The processor is configured to send a second signaling to the network session management function, and the second signaling explicitly indicates the release of one or more PDU sessions associated with the first network slice. The processor is configured to receive a second signaling from the UE on the second network slice as a PDU session establishment request. The PDU session establishment request includes a mapping of the second network slice to the first network slice, and the device does not send the mapping to the network session management function. The processor is configured to, based at least in part on determining that the first network slice is no longer available, send second signaling to the network data management function indicating a request to replace the first network slice with a second network slice; and receive third signaling from the network data management function, the third signaling identifying the second network slice that will replace the first network slice. The second signaling of the network data management function initiates the network data management function to perform a network slice subscription update procedure.

[0084] The processor 404 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, a discrete gate or transistor logic component, a discrete hardware component, or any combination thereof). In some implementations, the processor 404 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 404. The processor 404 may be configured to execute computer-readable instructions stored in a memory (e.g., memory 406) to cause the device 402 to perform various functions of the present disclosure.

[0085] The memory 406 may include random access memory (RAM) and read-only memory (ROM). The memory 406 may store computer-readable, computer-executable code, which includes instructions that, when executed by the processor 404, cause the device 402 to perform various functions described herein. The code may be stored in a non-transient computer-readable medium (such as a system memory or another type of memory). In some implementations, the code may not be directly executed by the processor 404, but may cause a computer (e.g., when compiled and executed) to perform the functions described herein. In some implementations, the memory 406 may include a basic I / O system (BIOS) or the like that may control basic hardware or software operations (such as interaction with peripheral components or devices).

[0086] I / O controller 410 can manage input signals and output signals for device 402. I / O controller 410 can also manage peripheral devices that are not integrated into device 402. In some implementations, I / O controller 410 can represent a physical connection or port to an external peripheral device. In some implementations, I / O controller 410 can utilize an operating system, such as

[0087] Or another known operating system. In some implementations, I / O controller 410 can be implemented as part of a processor, such as processor 404. In some implementations, a user can interact with device 402 via I / O controller 410, or via hardware components controlled by I / O controller 410.

[0088] In some implementations, the device 402 may include a single antenna 412. However, in some other implementations, the device 402 may have more than one antenna 412 (i.e., multiple antennas), including multiple antenna panels or antenna arrays, which may be able to concurrently send or receive multiple wireless transmissions. The transceiver 408 may communicate bidirectionally via one or more antennas 412, wired links, or wireless links described herein. For example, the transceiver 408 may represent a wireless transceiver and may communicate bidirectionally with another wireless transceiver. The transceiver 408 may also include a modem to modulate packets, thereby providing the modulated packets to one or more antennas 412 for transmission, and demodulating the packets received from the one or more antennas 412.

[0089] Figure 5An example of a block diagram 500 of a device 502 supporting network slice replacement initiated by an AMF in accordance with various aspects of the present disclosure is illustrated. The device 502 may be an example of a UE 104 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 sending communications 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).

[0090] The processor 504, the memory 506, the 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, the memory 506, the transceiver 508, or various combinations thereof or components thereof may support methods for performing one or more operations described herein.

[0091] In some implementations, the processor 504, memory 506, transceiver 508, or various combinations or components thereof may be implemented in hardware (e.g., in a communications management circuit system). 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 that is configured to or otherwise supports components 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 functions described herein (e.g., by executing instructions stored in the memory 506 by the processor 504).

[0092] For example, according to the examples disclosed herein, the processor 504 may support wireless communication at the device 502. The processor 504 may be configured to or otherwise support components for: receiving a first signaling indicating a configuration update to change from a first network slice to a second network slice, the first network slice being used for one or more PDU sessions, the configuration update including a mapping of the second network slice to the first network slice; and sending a second signaling as a new PDU session establishment request on the second network slice based at least in part on a determination to establish a new PDU session.

[0093] Additionally, the processor 504 may be configured to or otherwise support any one or combination of the following: the second network slice is not identified in the configured NSSAI. The method also includes releasing one or more PDU sessions based on the received configuration update to change from the first network slice to the second network slice. The one or more PDU sessions are implicitly released without subsequent signaling. After establishing the new PDU session, the one or more PDU sessions are released.

[0094] Additionally or alternatively, according to the examples disclosed herein, the device 502 may include an apparatus for wireless communication, comprising: a processor; and a memory coupled to the processor, the processor being configured to receive a first signaling indicating a configuration update to change from a first network slice to a second network slice, the first network slice being used for one or more PDU sessions, the configuration update including a mapping of the second network slice to the first network slice; and sending a second signaling as a new PDU session establishment request on the second network slice based at least in part on the apparatus's determination to establish a new PDU session.

[0095] Additionally, the wireless communication at the device 502 may include any one or combination of the following: the processor is configured to identify that the second network slice does not exist in the configured NSSAI. The processor is configured to release one or more PDU sessions based on the received configuration update to change from the first network slice to the second network slice. The processor is configured to implicitly release the one or more PDU sessions without subsequent signaling. The processor is configured to release the one or more PDU sessions after establishing a new PDU session.

[0096] 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, a discrete gate or transistor logic component, a discrete hardware component, 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.

[0097] The memory 506 may include random access memory (RAM) and read-only memory (ROM). The memory 506 may store computer-readable, computer-executable code, which includes 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-transient computer-readable medium (such as system memory or another type of memory). In some implementations, 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 implementations, the memory 506 may include a basic I / O system (BIOS) that can control basic hardware or software operations (such as interaction with peripheral components or devices), etc.

[0098] I / O controller 510 can manage input signals and output signals for device 502. I / O controller 510 can also manage peripheral devices that are not integrated into device 502. In some implementations, I / O controller 510 can represent a physical connection or port to an external peripheral device. In some implementations, I / O controller 510 can utilize an operating system, such as

[0099] Or another known operating system. In some implementations, I / O controller 510 can be implemented as part of a processor, such as processor 504. In some implementations, a user can interact with device 502 via I / O controller 510, or via hardware components controlled by I / O controller 510.

[0100] 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), including multiple antenna panels or antenna arrays, which may be able to concurrently send or receive multiple wireless transmissions. The transceiver 508 may communicate bidirectionally via one or more antennas 512, wired links, or wireless links 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 to modulate packets, thereby providing the modulated packets to one or more antennas 512 for transmission, and demodulating the packets received from the one or more antennas 512.

[0101] Figure 6 A flowchart of a method 600 for supporting network slice replacement initiated by an AMF according to various aspects of the present disclosure is illustrated. The operations of the method 600 may be implemented by the apparatus described herein or components thereof. For example, the operations of the method 600 may be implemented by reference to Figures 1 to 5The AMF described herein (or a network device implementing the AMF) may be used to perform the described functions. In some implementations, the device may execute an instruction set to control the functional elements of the device to perform the described functions. Additionally or alternatively, the device may use dedicated hardware to perform various aspects of the described functions.

[0102] At 602, the method may include determining that the first network slice is no longer available and can be replaced with a second network slice. The operations of 602 may be performed according to the examples described herein. In some implementations, various aspects of the operations of 602 may be described with reference to Figure 1 The described device is used to perform

[0103] At 604, the method may include sending first signaling indicating a configuration update to a UE registered with the first network slice, the configuration update including a mapping of the second network slice to the first network slice. The operations of 604 may be performed according to the examples described herein. In some implementations, various aspects of the operations of 604 may be described with reference to Figure 1 The device described is used to perform the

[0104] Figure 7 A flowchart of a method 700 for supporting network slice replacement initiated by an AMF according to various aspects of the present disclosure is illustrated. The operations of the method 700 may be implemented by the apparatus described herein or components thereof. For example, the operations of the method 700 may be implemented by reference to Figures 1 to 5 The AMF described herein (or a network device implementing the AMF) may be used to perform the described functions. In some implementations, the device may execute an instruction set to control the functional elements of the device to perform the described functions. Additionally or alternatively, the device may use dedicated hardware to perform various aspects of the described functions.

[0105] At 702, the method may include sending signaling to a network session management function that explicitly indicates the release of one or more PDU sessions associated with the first network slice. The operations of 702 may be performed according to the examples described herein. In some implementations, various aspects of the operations of 702 may be described with reference to Figure 1 The described device is used to perform

[0106] At 704, the method may include receiving signaling from the UE as a PDU session establishment request on the second network slice. The operations of 704 may be performed according to the examples described herein. In some implementations, various aspects of the operations of 704 may be described with reference to Figure 1 The described device is used to perform

[0107] At 706, the method may include sending signaling to a network data management function based on determining that the first network slice is no longer available, the signaling indicating a request to replace the first network slice with a second network slice. The operations of 706 may be performed according to the examples described herein. In some implementations, various aspects of the operations of 706 may be implemented by reference to Figure 1 The described device is used to perform

[0108] At 708, the method may include receiving signaling from a network data management function, the signaling identifying a second network slice that will replace the first network slice. The operations of 708 may be performed according to the examples described herein. In some implementations, various aspects of the operations of 708 may be performed by reference to Figure 1 The described device is used to perform

[0109] Figure 8 A flowchart of a method 800 for supporting network slice replacement initiated by an AMF according to various aspects of the present disclosure is illustrated. The operations of the method 800 may be implemented by the apparatus described herein or components thereof. For example, the operations of the method 800 may be implemented by reference to Figures 1 to 5 The described UE 104 is performed. In some implementations, the device may execute an instruction set to control the functional elements of the device to perform the described functions. Additionally or alternatively, the device may use dedicated hardware to perform various aspects of the described functions.

[0110] At 802, the method may include receiving first signaling indicating a configuration update to change from a first network slice to a second network slice, the first network slice being used for one or more PDU sessions, the configuration update including a mapping of the second network slice to the first network slice. The operations of 802 may be performed according to the examples described herein. In some implementations, various aspects of the operations of 802 may be implemented by reference to Figure 1 The described device is used to perform

[0111] At 804, the method may include sending second signaling as a new PDU session establishment request on the second network slice based at least in part on the determination to establish a new PDU session. The operations of 804 may be performed according to the examples described herein. In some implementations, various aspects of the operations of 804 may be described with reference to Figure 1 The described device is used to perform

[0112] Fig. 9 A flowchart of a method 900 for supporting network slice replacement initiated by an AMF according to various aspects of the present disclosure is illustrated. The operations of the method 900 may be implemented by the apparatus described herein or components thereof. For example, the operations of the method 900 may be implemented by reference to Figures 1 to 5The described UE 104 is performed. In some implementations, the device may execute an instruction set to control the functional elements of the device to perform the described functions. Additionally or alternatively, the device may use dedicated hardware to perform various aspects of the described functions.

[0113] At 902, the method may include releasing one or more PDU sessions based on a received configuration update to change from a first network slice to a second network slice. The operations of 902 may be performed according to the examples described herein. In some implementations, various aspects of the operations of 902 may be described with reference to Figure 1 The described device is used to perform

[0114] 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. Further, aspects from two or more methods may be combined.

[0115] The various illustrative blocks and components described in conjunction with the disclosure herein may be implemented or performed using 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 in an alternative, the processor may be any processor, controller, microcontroller, or state machine. The 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).

[0116] The functions described herein may be implemented in hardware, software executed by a processor, firmware, or any combination thereof. If implemented in software executed by a processor, the functions may be stored on a computer-readable medium or sent via 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 any combination of these. Features that implement the functions may also be physically located at various locations, including being distributed so that parts of the functions are implemented at different physical locations.

[0117] Computer-readable media include both non-transient computer storage media and communication media, including any medium that promotes the transmission of computer programs from one place to another. Non-transient storage media can be any available medium that can be accessed by a general-purpose computer or a special-purpose computer. By way of example and not limitation, non-transient computer-readable media can include RAM, ROM, electrically erasable programmable ROM (EEPROM), flash memory, compact disk (CD) ROM or other optical disk storage, disk storage or other magnetic storage devices, or can be used to carry or store desired program code components in the form of instructions or data structures and can be accessed by a general-purpose computer or a special-purpose computer or a general-purpose processor or any other non-transient medium of a special-purpose processor.

[0118] Any connection can be appropriately referred to as a computer-readable medium. For example, if the software is sent from a website, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technology (such as infrared, radio, and microwave), the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technology (such as infrared, radio, and microwave) is included in the definition of computer-readable medium. Disks and optical discs as used herein include CDs, laser discs, optical optical discs, digital versatile discs (DVDs), floppy disks, and Blu-ray discs, wherein disks usually reproduce data magnetically, and optical discs reproduce data optically using lasers. The above combination is also included in the scope of computer-readable media.

[0119] As used herein, including in the claims, "or" used in a list of items (e.g., a list of items beginning with a phrase such as "at least one of..." or "one or more of...") 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). Moreover, as used herein, the phrase "based on" should not be interpreted as a reference to a closed set of conditions. For example, an example step described as "based on condition A" may 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 "based at least in part on". Further, as used herein, including in the claims, a "set" may include one or more elements.

[0120] When referring to a network entity, the terms "send," "receive," or "communicate" may refer to any part of a network entity of a RAN (e.g., base station, CU, DU, RU) that communicates with another device (e.g., directly or via one or more other network entities).

[0121] The description set forth herein in conjunction with the accompanying drawings describes example configurations 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" and is not "preferred" or "better than other examples". For the purpose of providing an understanding of the described techniques, the specific embodiments include specific details. However, these techniques may be practiced without these specific details. In some instances, known structures and devices are shown in block diagram form to avoid confusing the concepts of the described examples.

[0122] The description herein is provided to enable one of ordinary skill in the art to make or use the present disclosure. Various modifications to the present disclosure will 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 broadest scope consistent with the principles and novel features disclosed herein.

Claims

1. A network device for wireless communication, comprising: at least one memory; as well as at least one processor coupled to the at least one memory and configured to cause the network device to: determining that the first network slice is no longer available and can be replaced with a second network slice; as well as Sending first signaling, the first signaling indicating a configuration update for a user equipment (UE) registered with the first network slice, the configuration update including a mapping of the second network slice to the first network slice.

2. The network device according to claim 1, wherein the second network slice is not a network slice subscribed by the UE and is not identified in the configured Network Slice Selection Assistance Information (NSSAI).

3. The network device according to claim 1, wherein the configuration update for the UE comprises at least one of the following: updated configured network slice selection assistance information (NSSAI), the updated configured NSSAI comprising the mapping of the second network slice to the first network slice; or The allowed NSSAI includes the mapping of the second network slice to the first network slice.

4. The network device according to claim 1, wherein the at least one processor is configured to cause the network device to send a second signaling to a network session management function, wherein the second signaling explicitly indicates the release of one or more protocol data unit (PDU) sessions associated with the first network slice.

5. The network device according to claim 1, wherein the at least one processor is configured to cause the network device to receive second signaling from the UE on the second network slice as the protocol data unit (PDU) session establishment request.

6. The network device of claim 1 , wherein the at least one processor is configured to cause the network device to: Based at least in part on determining that the first network slice is no longer available, sending second signaling to a network data management function, the second signaling indicating a request to replace the first network slice with the second network slice; and A third signaling is received from the network data management function, wherein the third signaling identifies the second network slice to replace the first network slice.

7. The network device according to claim 6, wherein the second signaling to the network data management function initiates the network data management function to perform a network slice subscription update procedure.

8. A user equipment (UE) for wireless communication, comprising: at least one memory; as well as at least one processor, coupled to the at least one memory and configured to cause the UE to: receiving first signaling indicating a configuration update to change from a first network slice to a second network slice, the first network slice being used for one or more protocol data unit (PDU) sessions, the configuration update comprising a mapping of the second network slice to the first network slice; as well as At least partly based on the UE's determination to establish a new PDU session, second signaling is sent on the second network slice as a new PDU session establishment request.

9. The UE according to claim 8, wherein the at least one processor is configured to cause the second network slice to not exist in the network slice selection assistance information (NSSAI) configured by the UE identification.

10. The UE of claim 8, wherein the at least one processor is configured to cause the UE to release the one or more PDU sessions based on the received configuration update to change from the first network slice to the second network slice.

11. The UE according to claim 10, wherein the at least one processor is configured to cause the UE to perform at least one of the following: implicitly release the one or more PDU sessions without subsequent signaling, or release the one or more PDU sessions after the new PDU session is established.

12. A processor for wireless communication, comprising: at least one controller coupled to the at least one memory and configured to cause the processor to: receiving first signaling indicating a configuration update to change from a first network slice to a second network slice, the first network slice being used for one or more protocol data unit (PDU) sessions, the configuration update comprising a mapping of the second network slice to the first network slice; as well as Based at least in part on a determination to establish a new PDU session, second signaling is sent on the second network slice as a new PDU session establishment request.

13. A method comprising: determining that the first network slice is no longer available and can be replaced with a second network slice; as well as Sending first signaling, the first signaling indicating a configuration update for a user equipment (UE) registered with the first network slice, the configuration update including a mapping of the second network slice to the first network slice.

14. The method of claim 13, wherein the second network slice is not a network slice to which the UE subscribes and is not identified in configured Network Slice Selection Assistance Information (NSSAI).

15. The method according to claim 13, wherein the configuration update of the UE comprises at least one of the following: updated configured network slice selection assistance information (NSSAI), the updated configured NSSAI comprising the mapping of the second network slice to the first network slice; or The allowed NSSAI includes the mapping of the second network slice to the first network slice.

16. The method according to claim 13 also includes sending a second signaling to a network session management function, wherein the second signaling explicitly indicates the release of one or more protocol data unit (PDU) sessions associated with the first network slice.

17. The method of claim 13, further comprising receiving second signaling from the UE on the second network slice as a protocol data unit (PDU) session establishment request.

18. The method of claim 17, wherein the PDU session establishment request includes the mapping of the second network slice to the first network slice, and the mapping is not sent to a network session management function.

19. The method according to claim 13, further comprising: Based at least in part on determining that the first network slice is no longer available, sending second signaling to a network data management function, the second signaling indicating a request to replace the first network slice with the second network slice; as well as A third signaling is received from the network data management function, wherein the third signaling identifies the second network slice to replace the first network slice.

20. The method of claim 19, wherein the second signaling to the network data management function initiates the network data management function to perform a network slice subscription update procedure.

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