WO2022238911A1

WO2022238911A1 - Controlled ue steering due to slicing

Info

Publication number: WO2022238911A1
Application number: PCT/IB2022/054353
Authority: WO
Inventors: Peter Hedman
Original assignee: Telefonaktiebolaget Lm Ericsson (Publ)
Priority date: 2021-05-10
Filing date: 2022-05-10
Publication date: 2022-11-17

Abstract

Providing controlled User Equipment (UE) steering due to slicing is disclosed herein. In one embodiment, a method performed by an Access and Mobility Management Function (AMF) to avoid redirecting a UE more than once for a same request from the UE comprises storing a requested Network Slice Selection Assistance Information (NSSAI) and an indication that a target NSSAI was provided to a NG-RAN as part of a UE context. The method further comprises providing the target NSSAI to the NG-RAN. The method also comprises subsequently receiving a requested NSSAI from the UE, wherein the requested NSSAI comprises one or more specific NSSAIs (S-NSSAIs) not available in the current tracking area (TA), and the UE context includes an indication that the target NSSAI was provided to the NG-RAN. The method additionally comprises determining whether to handle the UE request without providing a new target NSSAI to the NG-RAN.

Description

CONTROLLED UE STEERING DUE TO SLICING Related Applications [0001] This application claims the benefit of provisional patent application serial number 63/186,533, filed May 10, 2021, the disclosure of which is hereby incorporated herein by reference in its entirety. Technical Field [0002] The present disclosure relates to User Equipment (UE) redirection in a cellular communications system. Background [0003] TR 23.700-40 [1] solution #17 (see chapter 6.17 "Solution #17: Support of radio spectrum attribute by CN assisted RAN control") and solution #46 (see chapter 6.46 "Solution #46: Support RAN-Based UE redirection with enhanced RRC-level information") includes the possibility to redirect a user equipment (UE) to another cell of another tracking area (TA) such that the UE can access network slices that the UE requested which were not available in the UE's current cell and TA. [0004] The TR conclusion states as follows in Table 1: Table 1

Summary [0005] Methods and apparatus are disclosed herein for providing controlled User Equipment (UE) steering due to slicing. Embodiments of a method performed by an Access and Mobility Management Function (AMF) to avoid redirecting a UE more than once for a same request from the UE are disclosed herein. The method comprises storing a requested Network Slice Selection Assistance Information (NSSAI) and an indication that a target NSSAI was provided to a NG-RAN as part of a UE context. The method further comprises providing the target NSSAI to the NG-RAN. The method also comprises subsequently receiving a requested NSSAI from the UE, wherein the requested NSSAI comprises one or more specific NSSAIs (S-NSSAIs) not available in the current tracking area (TA), and the UE context includes an indication that the target NSSAI was provided to the NG-RAN. The method additionally comprises handling the UE request without providing a new target NSSAI to the NG-RAN. [0006] In some embodiments disclosed herein, the requested NSSAI is the same as the requested NSSAI stored in the UE context, and handling the UE request without providing a new target NSSAI to the NG-RAN comprises determining, based on the requested NSSAI being the same as the requested NSSAI stored in the UE context, that no need exists to provide the new target NSSAI. According to some embodiments disclosed herein, determining whether to handle the UE request without providing a new target NSSAI to the NG-RAN comprises one of handling the UE request by providing the new target NSSAI responsive to the one or more specific S-NSSAIs not available in the current TA having a higher priority than one or more S-NSSAI available in the current TA, or handling the UE request by not providing the new target NSSAI responsive to the one or more specific S-NSSAIs not available in the current TA not having a higher priority than one or more S-NSSAI available in the current TA. [0007] Some embodiments disclosed herein provide that the UE context comprises a UE context that is received from a previous AMF and that comprises the requested NSSAI and the indication that the target NSSAI was provided to the NG-RAN. According to some embodiments disclosed herein, the method further comprises, responsive to the AMF providing an allowed NSSAI without providing any target NSSAI to the NG- RAN, clearing the indication that the target NSSAI was provided to the NG-RAN in the UE context, and clearing the requested NSSAI in the UE context. [0008] Embodiments of an AMF for avoiding redirecting a UE more than once for a same request from the UE are also disclosed herein. The AMF is adapted to store a requested NSSAI and an indication that a target NSSAI was provided to a NG-RAN as part of a UE context. The AMF is further adapted to provide the target NSSAI to the NG-RAN. The AMF is also adapted to subsequently receive a requested NSSAI from the UE, wherein the requested NSSAI comprises one or more S-NSSAIs not available in the current TA, and the UE context includes an indication that the target NSSAI was provided to the NG-RAN. The AMF is additionally adapted to determine whether to handle the UE request without providing a new target NSSAI to the NG-RAN (e.g., handling the UE request by providing the new target NSSAI when the one or more specific S-NSSAIs not available in the current TA have higher priority than one or more S-NSSAI available in the current TA, or handling the UE request by not providing the new target NSSAI when the one or more specific S-NSSAIs not available in the current TA do not have higher priority than one or more S-NSSAI available in the current TA). In some embodiments disclosed herein, the AMF is further adapted to perform any of the operations attributed to the AMF above. [0009] Embodiments of a network node for implementing an AMF for avoiding redirecting a UE more than once for a same request from the UE are also disclosed herein. The network node comprises one or more transmitters, one or more receivers, and processing circuitry associated with the one or more transmitters and the one or more receivers. The processing circuitry is configured to cause the network node to store a requested NSSAI and an indication that a target NSSAI was provided to a NG- RAN as part of a UE context. The processing circuitry is further configured to cause the network node to provide the target NSSAI to the NG-RAN. The processing circuitry is also configured to cause the network node to subsequently receive a requested NSSAI from the UE, wherein the requested NSSAI comprises one or more S-NSSAIs not available in the current TA, and the UE context includes an indication that the target NSSAI was provided to the NG-RAN. The processing circuitry is additionally configured to cause the network node to determine whether to handle the UE request without providing a new target NSSAI to the NG-RAN (e.g., handling the UE request by providing the new target NSSAI when the one or more specific S-NSSAIs not available in the current TA have higher priority than one or more S-NSSAI available in the current TA, or handling the UE request by not providing the new target NSSAI when the one or more specific S-NSSAIs not available in the current TA do not have higher priority than one or more S-NSSAI available in the current TA). Some embodiments disclosed herein may further provide that the processing circuitry is further configured to cause the network node to perform any of the operations attributed to the AMF above. Brief Description of the Drawings [0010] The accompanying drawing figures incorporated in and forming a part of this specification illustrate several aspects of the disclosure, and together with the description serve to explain the principles of the disclosure. [0011] Figure 1 illustrates one example of a cellular communications system according to some embodiments disclosed herein; [0012] Figures 2 and 3 illustrate example embodiments in which the cellular communication system of Figure 3 is a Fifth Generation (5G) System (5GS); [0013] Figure 4 illustrates exemplary communications flows among and operations performed by some embodiments to provide controlled User Equipment (UE) steering; [0014] Figure 5 illustrates exemplary operations of an Access and Mobility Management Function (AMF) for providing controlled UE steering, according to some embodiments disclosed herein; [0015] Figure 6 illustrates a radio access node according to some embodiments disclosed herein; [0016] Figure 7 illustrates a virtualized embodiment of the radio access node of Figure 6 according to some embodiments disclosed herein; [0017] Figure 8 illustrates the radio access node of Figure 6 according to some other embodiments disclosed herein; [0018] Figure 9 illustrates a UE according to some embodiments disclosed herein; and [0019] Figure 10 illustrates the UE of Figure 9 according to some other embodiments disclosed herein. Detailed Description [0020] The embodiments set forth below represent information to enable those skilled in the art to practice the embodiments and illustrate the best mode of practicing the embodiments. Upon reading the following description in light of the accompanying drawing figures, those skilled in the art will understand the concepts of the disclosure and will recognize applications of these concepts not particularly addressed herein. It should be understood that these concepts and applications fall within the scope of the disclosure. [0021] There currently exist certain challenge(s). In particular, in some scenarios, the UE may have been redirected to a cell which does not support the intended network slices (or only a subset of what UE requested), and the Fifth Generation (5G) Core Network (5GC) may make another attempt to request the Radio Access Network (RAN) to redirect the UE. If the 5GC is not aware that the UE has been redirected once, the 5GC may repeat the request towards the RAN to redirect the UE multiple times, potentially leading to UE toggling between cells of TAs supporting a subset of the network slices that the UE is requesting, thus wasting resources as well as delaying the UE’s access to services. [0022] Aspects of the present disclosure and their embodiments may provide solutions to the aforementioned or other challenges. Embodiments are disclosed herein as proposed text for TS 23.501 [2], see CR in [4], in Table 2 below, with novel aspects marked with underline: Table 2

[0023] Aspects of the present disclosure and their embodiments may provide solutions to the aforementioned or other challenges. There are, proposed herein, various embodiments which address one or more of the issues disclosed herein. Embodiments of a method performed by an Access and Mobility Management Function (AMF) to avoid redirecting a user equipment (UE) more than once for a same request from the UE. The method comprises storing a requested Network Slice Selection Assistance Information (NSSAI) and an indication that a target NSSAI was provided to a Next Generation Radio Access Network (NG-RAN) as part of a UE context. The method further comprises providing the target NSSAI to the NG-RAN. The method also comprises subsequently receiving a requested NSSAI from the UE, wherein the requested NSSAI comprises one or more specific NSSAIs (S-NSSAIs) not available in the current tracking area (TA); the UE context includes an indication that the target NSSAI was provided to the NG-RAN; and the requested NSSAI is the same as the requested NSSAI stored in the UE context. The method additionally comprises handling the UE request without providing a new target NSSAI to the NG-RAN. In some embodiments, the method further comprises, responsive to the AMF providing an allowed NSSAI without providing any target NSSAI to the NG-RAN, clearing the indication that the target NSSAI was provided to the NG-RAN in the UE context, and clearing the requested NSSAI in the UE context. [0024] Embodiments of an AMF for avoiding redirecting a UE more than once for a same request from the UE are also disclosed herein. The AMF is adapted to store a requested NSSAI and an indication that a target NSSAI was provided to an NG-RAN as part of a UE context. The AMF is further adapted to provide the target NSSAI to the NG-RAN. The AMF is also adapted to subsequently receive a requested NSSAI from the UE, wherein the requested NSSAI comprises one or more S-NSSAIs not available in the current TA; the UE context includes an indication that the target NSSAI was provided to the NG-RAN; and the requested NSSAI is the same as the requested NSSAI stored in the UE context. The AMF is additionally adapted to determine whether to handle the UE request without providing a new target NSSAI to the NG-RAN, e.g., the AMF either handles the UE request by providing the new target NSSAI when the one or more specific S-NSSAIs not available in the current TA have higher priority than one or more S-NSSAI available in the current TA or handles the UE request by not providing the new target NSSAI when the one or more specific S-NSSAIs not available in the current TA do not have higher priority than one or more S-NSSAI available in the current TA. In some embodiments, the AMF is further adapted to perform any operations attributed to the AMF in the above-disclosed methods. [0025] Embodiments of a network node for implementing an AMF for avoiding redirecting a UE more than once for a same request from the UE are also disclosed herein. The network node comprises one or more transmitters, one or more receivers, and processing circuitry associated with the one or more transmitters and the one or more receivers. The processing circuitry is configured to cause the network node to store a requested NSSAI and an indication that a target NSSAI was provided to an NG- RAN as part of a UE context. The processing circuitry is further configured to cause the network node to provide the target NSSAI to the NG-RAN. The processing circuitry is also configured to cause the network node to subsequently receive a requested NSSAI from the UE, wherein the requested NSSAI comprises one or more specific S-NSSAIs not available in the current TA; the UE context includes an indication that the target NSSAI was provided to the NG-RAN; and the requested NSSAI is the same as the requested NSSAI stored in the UE context. The processing circuitry is additionally configured to cause the network node to handle the UE request without providing a new target NSSAI to the NG-RAN. In some embodiments, the processing circuitry is further configured to cause the network node to perform any operations attributed to the AMF in the above- disclosed methods. [0026] Certain embodiments may provide one or more of the following technical advantage(s). In particular, the embodiments disclosed herein enable the 5GC to avoid asking the NG-RAN to redirect the UE more than once for the same UE request. [0027] Before discussing controlled UE steering due to slicing in greater detail, the following terms are first defined: [0028] Radio Node: As used herein, a “radio node” is either a radio access node or a wireless communication device. [0029] Radio Access Node: As used herein, a “radio access node” or “radio network node” or “radio access network node” is any node in a Radio Access Network (RAN) of a cellular communications network that operates to wirelessly transmit and/or receive signals. Some examples of a radio access node include, but are not limited to, a base station (e.g., a New Radio (NR) base station (gNB) in a Third Generation Partnership Project (3GPP) Fifth Generation (5G) NR network or an enhanced or evolved Node B (eNB) in a 3GPP Long Term Evolution (LTE) network), a high-power or macro base station, a low-power base station (e.g., a micro base station, a pico base station, a home eNB, or the like), a relay node, a network node that implements part of the functionality of a base station (e.g., a network node that implements a gNB Central Unit (gNB-CU) or a network node that implements a gNB Distributed Unit (gNB-DU)) or a network node that implements part of the functionality of some other type of radio access node. [0030] Core Network Node: As used herein, a “core network node” is any type of node in a core network or any node that implements a core network function. Some examples of a core network node include, e.g., a Mobility Management Entity (MME), a Packet Data Network Gateway (P-GW), a Service Capability Exposure Function (SCEF), a Home Subscriber Server (HSS), or the like. Some other examples of a core network node include a node implementing an Access and Mobility Management Function (AMF), a User Plane Function (UPF), a Session Management Function (SMF), an Authentication Server Function (AUSF), a Network Slice Selection Function (NSSF), a Network Exposure Function (NEF), a Network Function (NF) Repository Function (NRF), a Policy Control Function (PCF), a Unified Data Management (UDM), or the like. [0031] Communication Device: As used herein, a “communication device” is any type of device that has access to an access network. Some examples of a communication device include, but are not limited to: mobile phone, smart phone, sensor device, meter, vehicle, household appliance, medical appliance, media player, camera, or any type of consumer electronic, for instance, but not limited to, a television, radio, lighting arrangement, tablet computer, laptop, or Personal Computer (PC). The communication device may be a portable, hand-held, computer-comprised, or vehicle- mounted mobile device, enabled to communicate voice and/or data via wireless or wireline connection. [0032] Wireless Communication Device: One type of communication device is a wireless communication device, which may be any type of wireless device that has access to (i.e., is served by) a wireless network (e.g., a cellular network). Some examples of a wireless communication device include, but are not limited to: a User Equipment device (UE) in a 3GPP network, a Machine Type Communication (MTC) device, and an Internet of Things (IoT) device. Such wireless communication devices may be, or may be integrated into, a mobile phone, smart phone, sensor device, meter, vehicle, household appliance, medical appliance, media player, camera, or any type of consumer electronic, for instance, but not limited to, a television, radio, lighting arrangement, tablet computer, laptop, or PC. The wireless communication device may be a portable, hand-held, computer-comprised, or vehicle-mounted mobile device, enabled to communicate voice and/or data via wireless connection. [0033] Network Node: As used herein, a “network node” is any node that is either part of the RAN or the core network of a cellular communications network/system. [0034] Transmission/Reception Point (TRP): In some embodiments, a TRP may be either a network node, a radio head, a spatial relation, or a Transmission Configuration Indicator (TCI) state. A TRP may be represented by a spatial relation or a TCI state in some embodiments. In some embodiments, a TRP may be using multiple TCI states. In some embodiments, a TRP may a part of the gNB transmitting and receiving radio signals to/from UE according to physical layer properties and parameters inherent to that element. In some embodiments, in Multiple TRP (multi-TRP) operation, a serving cell can schedule UE from two TRPs, providing better Physical Downlink Shared Channel (PDSCH) coverage, reliability and/or data rates. There are two different operation modes for multi-TRP: single Downlink Control Information (DCI) and multi- DCI. For both modes, control of uplink and downlink operation is done by both physical layer and Medium Access Control (MAC). In single-DCI mode, UE is scheduled by the same DCI for both TRPs and in multi-DCI mode, UE is scheduled by independent DCIs from each TRP. [0035] In some embodiments, a set Transmission Points (TPs) is a set of geographically co-located transmit antennas (e.g., an antenna array (with one or more antenna elements)) for one cell, part of one cell or one Positioning Reference Signal (PRS) -only TP. TPs can include base station (eNB) antennas, Remote Radio Heads (RRHs), a remote antenna of a base station, an antenna of a PRS-only TP, etc. One cell can be formed by one or multiple TPs. For a homogeneous deployment, each TP may correspond to one cell. [0036] In some embodiments, a set of TRPs is a set of geographically co-located antennas (e.g., an antenna array (with one or more antenna elements)) supporting TP and/or Reception Point (RP) functionality. [0037] Note that the description given herein focuses on a 3GPP cellular communications system and, as such, 3GPP terminology or terminology similar to 3GPP terminology is oftentimes used. However, the concepts disclosed herein are not limited to a 3GPP system. [0038] Note that, in the description herein, reference may be made to the term “cell”; however, particularly with respect to 5G NR concepts, beams may be used instead of cells and, as such, it is important to note that the concepts described herein are equally applicable to both cells and beams. [0039] Figure 1 illustrates one example of a cellular communications system 100 in which embodiments of the present disclosure may be implemented. In the embodiments described herein, the cellular communications system 100 is a 5G system (5GS) including a Next Generation RAN (NG-RAN) and a 5G Core (5GC) or an Evolved Packet System (EPS) including an Evolved Universal Terrestrial RAN (E-UTRAN) and an Evolved Packet Core (EPC). In this example, the RAN includes base stations 102-1 and 102-2, which in the 5GS include NR base stations (gNBs) and optionally next generation eNBs (ng-eNBs) (e.g., LTE RAN nodes connected to the 5GC) and in the EPS include eNBs, controlling corresponding (macro) cells 104-1 and 104-2. The base stations 102- 1 and 102-2 are generally referred to herein collectively as base stations 102 and individually as base station 102. Likewise, the (macro) cells 104-1 and 104-2 are generally referred to herein collectively as (macro) cells 104 and individually as (macro) cell 104. The RAN may also include a number of low power nodes 106-1 through 106-4 controlling corresponding small cells 108-1 through 108-4. The low power nodes 106-1 through 106-4 can be small base stations (such as pico or femto base stations) or RRHs, or the like. Notably, while not illustrated, one or more of the small cells 108-1 through 108-4 may alternatively be provided by the base stations 102. The low power nodes 106-1 through 106-4 are generally referred to herein collectively as low power nodes 106 and individually as low power node 106. Likewise, the small cells 108-1 through 108-4 are generally referred to herein collectively as small cells 108 and individually as small cell 108. The cellular communications system 100 also includes a core network 110, which in the 5G System (5GS) is referred to as the 5GC. The base stations 102 (and optionally the low power nodes 106) are connected to the core network 110. [0040] The base stations 102 and the low power nodes 106 provide service to wireless communication devices 112-1 through 112-5 in the corresponding cells 104 and 108. The wireless communication devices 112-1 through 112-5 are generally referred to herein collectively as wireless communication devices 112 and individually as wireless communication device 112. In the following description, the wireless communication devices 112 are oftentimes UEs, but the present disclosure is not limited thereto. [0041] Figure 2 illustrates a wireless communication system represented as a 5G network architecture composed of core Network Functions (NFs), where interaction between any two NFs is represented by a point-to-point reference point/interface. Figure 2 can be viewed as one particular implementation of the system 100 of Figure 1. [0042] Seen from the access side the 5G network architecture shown in Figure 2 comprises a plurality of UEs 112 connected to either a RAN 102 or an Access Network (AN) as well as an AMF 200. Typically, the R(AN) 102 comprises base stations, e.g., such as eNBs or gNBs or similar. Seen from the core network side, the 5GC NFs shown in Figure 2 include a NSSF 202, an AUSF 204, a UDM 206, the AMF 200, a SMF 208, a PCF 210, and an Application Function (AF) 212. [0043] Reference point representations of the 5G network architecture are used to develop detailed call flows in the normative standardization. The N1 reference point is defined to carry signaling between the UE 112 and AMF 200. The reference points for connecting between the AN 102 and AMF 200 and between the AN 102 and UPF 214 are defined as N2 and N3, respectively. There is a reference point, N11, between the AMF 200 and SMF 208, which implies that the SMF 208 is at least partly controlled by the AMF 200. N4 is used by the SMF 208 and UPF 214 so that the UPF 214 can be set using the control signal generated by the SMF 208, and the UPF 214 can report its state to the SMF 208. N9 is the reference point for the connection between different UPFs 214, and N14 is the reference point connecting between different AMFs 200, respectively. N15 and N7 are defined since the PCF 210 applies policy to the AMF 200 and SMF 208, respectively. N12 is required for the AMF 200 to perform authentication of the UE 112. N8 and N10 are defined because the subscription data of the UE 112 is required for the AMF 200 and SMF 208. [0044] The 5GC network aims at separating UP and CP. The UP carries user traffic while the CP carries signaling in the network. In Figure 2, the UPF 214 is in the UP and all other NFs, i.e., the AMF 200, SMF 208, PCF 210, AF 212, NSSF 202, AUSF 204, and UDM 206, are in the CP. Separating the UP and CP guarantees each plane resource to be scaled independently. It also allows UPFs to be deployed separately from CP functions in a distributed fashion. In this architecture, UPFs may be deployed very close to UEs to shorten the Round Trip Time (RTT) between UEs and data network for some applications requiring low latency. [0045] The core 5G network architecture is composed of modularized functions. For example, the AMF 200 and SMF 208 are independent functions in the CP. Separated AMF 200 and SMF 208 allow independent evolution and scaling. Other CP functions like the PCF 210 and AUSF 204 can be separated as shown in Figure 2. Modularized function design enables the 5GC network to support various services flexibly. [0046] Each NF interacts with another NF directly. It is possible to use intermediate functions to route messages from one NF to another NF. In the CP, a set of interactions between two NFs is defined as service so that its reuse is possible. This service enables support for modularity. The UP supports interactions such as forwarding operations between different UPFs. [0047] Figure 3 illustrates a 5G network architecture using service-based interfaces between the NFs in the CP, instead of the point-to-point reference points/interfaces used in the 5G network architecture of Figure 2. However, the NFs described above with reference to Figure 2 correspond to the NFs shown in Figure 3. The service(s) etc. that a NF provides to other authorized NFs can be exposed to the authorized NFs through the service-based interface. In Figure 3 the service based interfaces are indicated by the letter “N” followed by the name of the NF, e.g., Namf for the service based interface of the AMF 200 and Nsmf for the service based interface of the SMF 208, etc. The NEF 300 and the NRF 302 in Figure 3 are not shown in Figure 2 discussed above. However, it should be clarified that all NFs depicted in Figure 2 can interact with the NEF 300 and the NRF 302 of Figure 3 as necessary, though not explicitly indicated in Figure 2. [0048] Some properties of the NFs shown in Figures 2 and 3 may be described in the following manner. The AMF 200 provides UE-based authentication, authorization, mobility management, etc. A UE 112 even using multiple access technologies is basically connected to a single AMF 200 because the AMF 200 is independent of the access technologies. The SMF 208 is responsible for session management and allocates Internet Protocol (IP) addresses to UEs. It also selects and controls the UPF 214 for data transfer. If a UE 112 has multiple sessions, different SMFs 208 may be allocated to each session to manage them individually and possibly provide different functionalities per session. The AF 212 provides information on the packet flow to the PCF 210 responsible for policy control in order to support QoS. Based on the information, the PCF 210 determines policies about mobility and session management to make the AMF 200 and SMF 208 operate properly. The AUSF 204 supports authentication function for UEs or similar and thus stores data for authentication of UEs or similar while the UDM 206 stores subscription data of the UE 112. The Data Network (DN), not part of the 5GC network, provides Internet access or operator services and similar. [0049] An NF may be implemented either as a network element on a dedicated hardware, as a software instance running on a dedicated hardware, or as a virtualized function instantiated on an appropriate platform, e.g., a cloud infrastructure. [0050] As disclosed herein, the following proposed additions to the UE context in the AMF are shown as underlined text in Table 3 as changes to TS 23.502 [3], see CR in [5]: Table 3

[0051] Figure 4 provides a message flow diagram to illustrate exemplary communications flows among and operations performed according to some embodiments. In Figure 4, an NG-RAN 400, an AMF 402, and a UE 404 are represented by blocks and vertical lines, with communications between the elements represented by arrows and operations performed by the elements represented by blocks on the vertical lines. As seen in Figure 4, the AMF 402 stores a requested NSSAI, and an indication that a target NSSAI was provided to an NG-RAN as part of a UE context, as indicated by block 406. The AMF 402 provides the target NSSAI 408 to the NG-RAN 400, as indicated by arrow 410. The AMF 402 subsequently receives a requested NSSAI 412 from the UE 404, as indicated by arrow 414. Because the requested NSSAI 412 comprises one or more S-NSSAIs not available in the current TA, the UE context includes an indication that the target NSSAI 408 was provided to the NG-RAN 400, and the requested NSSAI 412 is the same as the requested NSSAI stored in the UE context, the AMF 402 then determines whether to handle the UE request without providing a new target NSSAI to the NG-RAN 400, as indicated by block 416. [0052] Figure 5 provides a flowchart 500 that illustrates exemplary operations according to some embodiments. In Figure 5, operations begin with an AMF, such as the AMF 402 of Figure 4, storing a requested NSSAI, and an indication that a target NSSAI was provided to an NG-RAN as part of a UE context (e.g., a UE context received from a previous AMF) (block 502). The AMF next provides the target NSSAI to the NG- RAN (block 504). The AMF subsequently receives a requested NSSAI from the UE, wherein the requested NSSAI comprises one or more S-NSSAIs not available in the current TA; the UE context includes an indication that the target NSSAI was provided to the NG-RAN; and the requested NSSAI is the same as the requested NSSAI stored in the UE context (block 506). The AMF then determines whether to handle the UE request without providing a new target NSSAI to the NG-RAN (e.g., by determining, based on the requested NSSAI being the same as the requested NSSAI stored in the UE context, that no need exists to provide the new target NSSAI) (block 508). In some embodiments, the operations of block 508 for determining whether to handle the UE request without providing a new target NSSAI to the NG-RAN may comprise handling the UE request by providing the new target NSSAI when the one or more specific S- NSSAIs not available in the current TA have higher priority than one or more S-NSSAI available in the current TA, or handling the UE request by not providing the new target NSSAI when the one or more specific S-NSSAIs not available in the current TA do not have higher priority than one or more S-NSSAI available in the current TA. [0053] In some embodiments, the AMF may additionally perform operations responsive to the AMF providing an allowed NSSAI without providing any target NSSAI to the NG-RAN (block 510). In such embodiments, the AMF may clear the indication that the target NSSAI was provided to the NG-RAN in the UE context (block 512). The AMF may also clear the requested NSSAI in the UE context (block 514). [0054] Figure 6 is a schematic block diagram of a radio access node 600 according to some embodiments of the present disclosure. Optional features are represented by dashed boxes. The radio access node 600 may be, for example, a base station 102 or 106 or a network node that implements all or part of the functionality of the base station 102 or gNB described herein. As illustrated, the radio access node 600 includes a control system 602 that includes one or more processors 604 (e.g., Central Processing Units (CPUs), Application Specific Integrated Circuits (ASICs), Field Programmable Gate Arrays (FPGAs), and/or the like), memory 606, and a network interface 608. The one or more processors 604 are also referred to herein as processing circuitry. In addition, the radio access node 600 may include one or more radio units 610 that each includes one or more transmitters 612 and one or more receivers 614 coupled to one or more antennas 616. The radio units 610 may be referred to or be part of radio interface circuitry. In some embodiments, the radio unit(s) 610 is external to the control system 602 and connected to the control system 602 via, e.g., a wired connection (e.g., an optical cable). However, in some other embodiments, the radio unit(s) 610 and potentially the antenna(s) 616 are integrated together with the control system 602. The one or more processors 604 operate to provide one or more functions of a radio access node 600 as described herein. In some embodiments, the function(s) are implemented in software that is stored, e.g., in the memory 606 and executed by the one or more processors 604. [0055] Figure 7 is a schematic block diagram that illustrates a virtualized embodiment of the radio access node 600 according to some embodiments of the present disclosure. This discussion is equally applicable to other types of network nodes. Further, other types of network nodes may have similar virtualized architectures. Again, optional features are represented by dashed boxes. [0056] As used herein, a “virtualized” radio access node is an implementation of the radio access node 600 in which at least a portion of the functionality of the radio access node 600 is implemented as a virtual component(s) (e.g., via virtual machine(s) executing on a physical processing node(s) in a network(s)). As illustrated, in this example, the radio access node 600 may include the control system 602 and/or the one or more radio units 610, as described above. The control system 602 may be connected to the radio unit(s) 610 via, for example, an optical cable or the like. The radio access node 600 includes one or more processing nodes 700 coupled to or included as part of a network(s) 702. If present, the control system 602 or the radio unit(s) are connected to the processing node(s) 700 via the network 702. Each processing node 700 includes one or more processors 704 (e.g., CPUs, ASICs, FPGAs, and/or the like), memory 706, and a network interface 708. [0057] In this example, functions 710 of the radio access node 600 described herein are implemented at the one or more processing nodes 700 or distributed across the one or more processing nodes 700 and the control system 602 and/or the radio unit(s) 610 in any desired manner. In some particular embodiments, some or all of the functions 710 of the radio access node 600 described herein are implemented as virtual components executed by one or more virtual machines implemented in a virtual environment(s) hosted by the processing node(s) 700. As will be appreciated by one of ordinary skill in the art, additional signaling or communication between the processing node(s) 700 and the control system 602 is used in order to carry out at least some of the desired functions 710. Notably, in some embodiments, the control system 602 may not be included, in which case the radio unit(s) 610 communicate directly with the processing node(s) 700 via an appropriate network interface(s). [0058] In some embodiments, a computer program including instructions which, when executed by at least one processor, causes the at least one processor to carry out the functionality of radio access node 600 or a node (e.g., a processing node 700) implementing one or more of the functions 710 of the radio access node 600 in a virtual environment according to any of the embodiments described herein is provided. In some embodiments, a carrier comprising the aforementioned computer program product is provided. The carrier is one of an electronic signal, an optical signal, a radio signal, or a computer readable storage medium (e.g., a non-transitory computer readable medium such as memory). [0059] Figure 8 is a schematic block diagram of the radio access node 600 according to some other embodiments of the present disclosure. The radio access node 600 includes one or more modules 800, each of which is implemented in software. The module(s) 800 provide the functionality of the radio access node 600 described herein. This discussion is equally applicable to the processing node 700 of Figure 7 where the modules 800 may be implemented at one of the processing nodes 700 or distributed across multiple processing nodes 700 and/or distributed across the processing node(s) 700 and the control system 602. [0060] Figure 9 is a schematic block diagram of a wireless communication device 900 according to some embodiments of the present disclosure. As illustrated, the wireless communication device 900 includes one or more processors 902 (e.g., CPUs, ASICs, FPGAs, and/or the like), memory 904, and one or more transceivers 906 each including one or more transmitters 908 and one or more receivers 910 coupled to one or more antennas 912. The transceiver(s) 906 includes radio-front end circuitry connected to the antenna(s) 912 that is configured to condition signals communicated between the antenna(s) 912 and the processor(s) 902, as will be appreciated by on of ordinary skill in the art. The processors 902 are also referred to herein as processing circuitry. The transceivers 906 are also referred to herein as radio circuitry. In some embodiments, the functionality of the wireless communication device 900 described above may be fully or partially implemented in software that is, e.g., stored in the memory 904 and executed by the processor(s) 902. Note that the wireless communication device 900 may include additional components not illustrated in Figure 9 such as, e.g., one or more user interface components (e.g., an input/output interface including a display, buttons, a touch screen, a microphone, a speaker(s), and/or the like and/or any other components for allowing input of information into the wireless communication device 900 and/or allowing output of information from the wireless communication device 900), a power supply (e.g., a battery and associated power circuitry), etc. [0061] In some embodiments, a computer program including instructions which, when executed by at least one processor, causes the at least one processor to carry out the functionality of the wireless communication device 900 according to any of the embodiments described herein is provided. In some embodiments, a carrier comprising the aforementioned computer program product is provided. The carrier is one of an electronic signal, an optical signal, a radio signal, or a computer readable storage medium (e.g., a non-transitory computer readable medium such as memory). [0062] Figure 10 is a schematic block diagram of the wireless communication device 900 according to some other embodiments of the present disclosure. The wireless communication device 900 includes one or more modules 1000, each of which is implemented in software. The module(s) 1000 provide the functionality of the wireless communication device 900 described herein. [0063] Any appropriate steps, methods, features, functions, or benefits disclosed herein may be performed through one or more functional units or modules of one or more virtual apparatuses. Each virtual apparatus may comprise a number of these functional units. These functional units may be implemented via processing circuitry, which may include one or more microprocessor or microcontrollers, as well as other digital hardware, which may include Digital Signal Processor (DSPs), special-purpose digital logic, and the like. The processing circuitry may be configured to execute program code stored in memory, which may include one or several types of memory such as Read Only Memory (ROM), Random Access Memory (RAM), cache memory, flash memory devices, optical storage devices, etc. Program code stored in memory includes program instructions for executing one or more telecommunications and/or data communications protocols as well as instructions for carrying out one or more of the techniques described herein. In some implementations, the processing circuitry may be used to cause the respective functional unit to perform corresponding functions according one or more embodiments of the present disclosure. [0064] While processes in the figures may show a particular order of operations performed by certain embodiments of the present disclosure, it should be understood that such order is exemplary (e.g., alternative embodiments may perform the operations in a different order, combine certain operations, overlap certain operations, etc.). [0065] Some example embodiments of the present disclosure are as follows: [0066] Embodiment 1: A method performed by an Access and Mobility Management Function, AMF, (Figure 4, 402) to avoid redirecting a user equipment, UE, (Figure 4, 404) more than once for a same request from the UE, the method comprising: • storing (Figure 5, 502) a requested Network Slice Selection Assistance Information, NSSAI, and an indication that a target NSSAI (Figure 4, 408) was provided to a Next Generation Radio Access Network, NG-RAN, (Figure 4, 400) as part of a UE context; • providing (Figure 5, 504) the target NSSAI to the NG-RAN; • subsequently receiving (Figure 5, 506) a requested NSSAI (Figure 4, 412) from the UE, wherein: • the requested NSSAI comprises one or more specific NSSAIs, S-NSSAIs, not available in the current tracking area, TA; • the UE context includes an indication that the target NSSAI was provided to the NG-RAN; and • the requested NSSAI is the same as the requested NSSAI stored in the UE context; and • handling (Figure 5, 508) the UE request without providing a new target NSSAI to the NG-RAN. [0067] Embodiment 2: The method of embodiment 1, wherein, responsive to the AMF providing an allowed NSSAI without providing any target NSSAI to the NG-RAN: • clearing (Figure 5, 512) the indication that the target NSSAI was provided to the NG- RAN in the UE context; and • clearing (Figure 5, 514) the requested NSSAI in the UE context. [0068] Embodiment 3: An Access and Mobility Management Function, AMF, (Figure 4, 402) for avoiding redirecting a user equipment, UE, (Figure 4, 404), more than once for a same request from the UE, the AMF adapted to: • store (Figure 5, 502) a requested Network Slice Selection Assistance Information, NSSAI, and an indication that a target NSSAI (Figure 4, 408) was provided to a Next Generation Radio Access Network, NG-RAN, (Figure 4, 400) as part of a UE context; • provide (Figure 5, 504) the target NSSAI to the NG-RAN; • subsequently receive (Figure 5, 506) a requested NSSAI (Figure 4, 412) from the UE, wherein: • the requested NSSAI comprises one or more specific NSSAIs, S-NSSAIs, not available in the current tracking area, TA; • the UE context includes an indication that the target NSSAI was provided to the NG-RAN; and • the requested NSSAI is the same as the requested NSSAI stored in the UE context; and • handle (Figure 5, 508) the UE request without providing a new target NSSAI to the NG-RAN. [0069] Embodiment 4: The AMF of embodiment 3, wherein the AMF is further adapted to perform the method of embodiment 2. [0070] Embodiment 5: A network node (Figure 6, 600) for implementing an Access and Mobility Management Function, AMF, (Figure 4, 402) for avoiding redirecting a user equipment, UE, (Figure 4, 404), more than once for a same request from the UE, the network node comprising: • one or more transmitters (Figure 6, 612); • one or more receivers (Figure 6, 614); and • processing circuitry (Figure 6, 604) associated with the one or more transmitters and the one or more receivers, the processing circuitry configured to cause the network node to: • store (Figure 5, 502) a requested Network Slice Selection Assistance Information, NSSAI, and an indication that a target NSSAI (Figure 4, 408) was provided to a Next Generation Radio Access Network, NG-RAN, (Figure 4, 400) as part of a UE context; • provide (Figure 5, 504) the target NSSAI to the NG-RAN; • subsequently receive (Figure 5, 506) a requested NSSAI (Figure 4, 412) from the UE, wherein: • the requested NSSAI comprises one or more specific NSSAIs, S-NSSAIs, not available in the current tracking area, TA; • the UE context includes an indication that the target NSSAI was provided to the NG-RAN; and • the requested NSSAI is the same as the requested NSSAI stored in the UE context; and • handle (Figure 5, 508) the UE request without providing a new target NSSAI to the NG-RAN. [0071] Embodiment 6: The network node of embodiment 5, wherein the processing circuitry is further configured to cause the network node to perform the method of embodiment 2. [0072] At least some of the following abbreviations may be used in this disclosure. If there is an inconsistency between abbreviations, preference should be given to how it is used above. If listed multiple times below, the first listing should be preferred over any subsequent listing(s). • 3GPP Third Generation Partnership Project • 5G Fifth Generation • 5GC Fifth Generation Core • 5GS Fifth Generation System • AF Application Function • AMF Access and Mobility Function • AN Access Network • AP Access Point • ASIC Application Specific Integrated Circuit • AUSF Authentication Server Function • CPU Central Processing Unit • DN Data Network • DSP Digital Signal Processor • eNB Enhanced or Evolved Node B • EPS Evolved Packet System • E-UTRA Evolved Universal Terrestrial Radio Access • FPGA Field Programmable Gate Array • gNB New Radio Base Station • gNB-DU New Radio Base Station Distributed Unit • HSS Home Subscriber Server • IoT Internet of Things • IP Internet Protocol • LTE Long Term Evolution • MME Mobility Management Entity • MTC Machine Type Communication • NEF Network Exposure Function • NF Network Function • NG-RAN Next Generation Radio Access Network • NR New Radio • NRF Network Function Repository Function • NSSAI Network Slice Selection Assistance Information • NSSF Network Slice Selection Function • OTT Over-the-Top • PC Personal Computer • PCF Policy Control Function • P-GW Packet Data Network Gateway • QoS Quality of Service • RAM Random Access Memory • RAN Radio Access Network • ROM Read Only Memory • RRH Remote Radio Head • RTT Round Trip Time • SCEF Service Capability Exposure Function • SMF Session Management Function • S-NSSAI Specific Network Slice Selection Assistance Information • UDM Unified Data Management • UE User Equipment • UPF User Plane Function [0073] Those skilled in the art will recognize improvements and modifications to the embodiments of the present disclosure. All such improvements and modifications are considered within the scope of the concepts disclosed herein.

Claims

Claims 1. A method performed by an Access and Mobility Management Function, AMF, (402) to avoid redirecting a user equipment, UE, (404) more than once for a same request from the UE, the method comprising: storing (502) a requested Network Slice Selection Assistance Information, NSSAI, and an indication that a target NSSAI was provided to a Next Generation Radio Access Network, NG-RAN, as part of a UE context; providing (504) the target NSSAI to the NG-RAN; subsequently receiving (506) a requested NSSAI from the UE, wherein: the requested NSSAI comprises one or more specific NSSAIs, S-NSSAIs, not available in the current tracking area, TA; and the UE context includes an indication that the target NSSAI was provided to the NG-RAN; and determining whether to handle (508) the UE request without providing a new target NSSAI to the NG-RAN.

2. The method of claim 1, wherein: the requested NSSAI is the same as the requested NSSAI stored in the UE context; and determining whether to handle the UE request without providing a new target NSSAI to the NG-RAN comprises determining, based on the requested NSSAI being the same as the requested NSSAI stored in the UE context, that no need exists to provide the new target NSSAI.

3. The method of claim 1, wherein determining whether to handle the UE request without providing a new target NSSAI to the NG-RAN comprises one of: handling the UE request by providing the new target NSSAI responsive to the one or more specific S-NSSAIs not available in the current TA having a higher priority than one or more S-NSSAI available in the current TA, or handling the UE request by not providing the new target NSSAI responsive to the one or more specific S-NSSAIs not available in the current TA not having a higher priority than one or more S-NSSAI available in the current TA.

4. The method of claim 1, wherein the UE context comprises a UE context that is received from a previous AMF and that comprises the requested NSSAI and the indication that the target NSSAI was provided to the NG-RAN.

5. The method of claim 1, wherein, responsive to the AMF providing an allowed NSSAI without providing any target NSSAI to the NG-RAN: clearing (512) the indication that the target NSSAI was provided to the NG-RAN in the UE context; and clearing (514) the requested NSSAI in the UE context.

6. An Access and Mobility Management Function, AMF, (402) for avoiding redirecting a user equipment, UE, (404) more than once for a same request from the UE, the AMF adapted to: store (502) a requested Network Slice Selection Assistance Information, NSSAI, and an indication that a target NSSAI was provided to a Next Generation Radio Access Network, NG-RAN, as part of a UE context; provide (504) the target NSSAI to the NG-RAN; subsequently receive (506) a requested NSSAI from the UE, wherein: the requested NSSAI comprises one or more specific NSSAIs, S-NSSAIs, not available in the current tracking area, TA; and the UE context includes an indication that the target NSSAI was provided to the NG-RAN; and determine whether to handle (508) the UE request without providing a new target NSSAI to the NG-RAN.

7. The AMF of claim 6, wherein the AMF is further adapted to perform the method of any one of claims 2-5.

8. A network node (600) for implementing an Access and Mobility Management Function, AMF, (402) for avoiding redirecting a user equipment, UE, (404) more than once for a same request from the UE, the network node comprising: one or more transmitters (612); one or more receivers (614); and processing circuitry (604) associated with the one or more transmitters and the one or more receivers, the processing circuitry configured to cause the network node to: store (502) a requested Network Slice Selection Assistance Information, NSSAI, and an indication that a target NSSAI was provided to a Next Generation Radio Access Network, NG-RAN, as part of a UE context; provide (504) the target NSSAI to the NG-RAN; subsequently receive (506) a requested NSSAI from the UE, wherein: the requested NSSAI comprises one or more specific NSSAIs, S-NSSAIs, not available in the current tracking area, TA; and the UE context includes an indication that the target NSSAI was provided to the NG-RAN; and determine whether to handle (508) the UE request without providing a new target NSSAI to the NG-RAN.

9. The network node of claim 8, wherein the processing circuitry is further configured to cause the network node to perform the method of one of claims 2-5.