WO2022152616A2

WO2022152616A2 - Methods and apparatuses for changing network slice

Info

Publication number: WO2022152616A2
Application number: PCT/EP2022/050222
Authority: WO
Inventors: Peter Hedman; Ralf Keller; Angelo Centonza
Original assignee: Telefonaktiebolaget Lm Ericsson (Publ)
Priority date: 2021-01-15
Filing date: 2022-01-07
Publication date: 2022-07-21
Also published as: WO2022152616A3

Abstract

Methods and apparatuses for network slice are disclosed. According to an embodiment, A User Equipment, UE uses a first Protocol Data Unit, PDU, session on a first network slice in a source registration area; moves to a second registration area in which the first network slice is not an allowed network slice; determines that the first network slice can be remapped to a second network slice, the second network slice being an allowed network slice in the second registration area; and sends a PDU session establishment request to a first network node to initiate establishment of a second PDU session on the second network slice, wherein the PDU session establishment request comprises information that indicates that the second PDU session is being established to remap the first PDU session on the first network slice to the second PDU session on the second network slice.

Description

METHODS AND APPARATUSES FOR CHANGING NETWORK SLICE

Technical Field

[0001] Embodiments of the disclosure generally relate to communication, and, more particularly, to methods and apparatuses for change network slice.

Background

[0002] Figure 1 illustrates an example of the concept of network slicing with respect to the Third Generation Partnership Project (3GPP) Fifth Generation System (5GS). As shown in Figure 1, the 5GS supports multiple services. In this example, there are four services labelled as Service 1, Service 2, Service 3, and Service 4. Example services include, but are not limited to, enhanced Mobile Broadband (eMBB), Ultra Reliable Low Latency Communication (URLLC), massive Machine Type Communication (mMTC) or massive Internet of Things (loT), emergency services, and/or the like. As shown in Figure 1, each of the services is mapped to a 5GS network slice that is customized to meet the needs of that service. Note that more than one service may be mapped to the same 5GS network slice. As also illustrated in Figure 1, the 5GS network slices are implemented on the same physical infrastructure. In the 5GS and particularly in the Fifth Generation Core (5GC), network slices are identified by Single Network Slice Selection Assistance Information (S- NSSAI).

[0003] In some scenarios, a network slice may be non-homogenously or geographically limited during rollout or permanent, e.g., a network slice in a factory may be geographically limited to the geographic area of the factory. This results in situations in which a User Equipment (UE) may have access to one set of network slices when in a first geographic area (e.g., a first Registration Area) and have access to another, different set of network slices when in a second geographic area (e.g., a second Registration Area). [0004] Figure 2 illustrates an example of such a scenario. In the illustrated example, a UE can use two network slices (S-NSSAI x and S-NSSAI y) when in Registration Area 1, but the UE can only use one of the network slices (S-NSSAI y) when in Registration Area 2. [0005] Within a Registration Area (one or more Tracking Areas), the network slices are homogenous, i.e., each cell supports the same set of network slices (i.e., each cell supports the same set of S-NSSAIs). When the UE moves from a first Registration Area to a second (new) Registration Area, the UE performs registration and receives a new set of Allowed S- NSSAIs in the new Registration Area. For example, as illustrated in Figure 2, the S-NSSAI x and S-NSSAI y are both in the set, or list, of Allowed S-NSSAIs of Registration Area 1, whereas only S-NSSAI y is in the set, or list, of Allowed S-NSSAIs of Registration Area 2.

[0006] There currently exist certain challenge(s). When the UE moves from one Registration Area to another Registration Area (e.g., from Registration Area 1 to Registration Area 2 in the example of Figure 2), the Protocol Data Unit (PDU) session(s) established with a first network slice, e.g., S-NSSAI x (only in Registration Area 1) have to be released. Hence, the UE either cannot access the services that it has used before moving to the new Registration Area or has to establish a new PDU session(s) using a second network slice (e.g., S-NSSAI y in the example of Figure 2) that is available in the new Registration Area. However, when establishing the new PDU session(s) using the second network slice in the new Registration Area, the network may select a different Session Management Function (SMF) for the same Data Network Name (DNN) because it is now using the second network slice.

[0007] Certain aspects of the present disclosure and their embodiments may provide solutions to the aforementioned or other challenges. Embodiments disclosed herein relate to what is referred to herein as "remapping a network slice" or "remapping S-NSSAI".

[0008] In some embodiments, the network (e.g., a network node) select the same SMF and possibly also the same User Plane Function (UPF) for a PDU session with a new (second) network slice (e.g., S-NSSAI y) as previously used for an original (first) network slice (e.g., S-NSSAI x).

[0009] There are, proposed herein, various embodiments which address one or more of the issues disclosed herein. In one embodiment, a method performed by a UE comprises using a first Protocol Data Unit (PDU) session on a first network slice in a source registration area; moving to a second registration area in which the first network slice is not an allowed network slice; determining that the first network slice can be remapped to a second network slice, the second network slice being an allowed network slice in the second registration area; and sending a PDU session establishment request to a first network node to initiate establishment of a second PDU session on the second network slice, wherein the PDU session establishment request comprises information that indicates that the second PDU session is being established to remap the first PDU session on the first network slice to the second PDU session on the second network slice.

[0010] In one embodiment, the method further comprises receiving an Internet Protocol (IP) address from a second network node in association with establishment of the second PDU session on the second network slice; and assigning the IP address to the second PDU session.

[0011] In one embodiment, the method further comprises routing PDUs at the UE that would have been routed via the first PDU session on the first network slice via the second PDU session on the second network slice.

[0012] In one embodiment, the method wherein the first network node is an Access and Mobility Management Function (AMF), and the second network node is a Session Management Function (SMF).

[0013] In one embodiment, the method further comprises informing, to the first network node, support of remapping the first network slice to the second network slice; and receiving, from the first network node, support of remapping the first network slice to the second network slice.

[0014] In one embodiment, a method performed by an AMF, comprises receiving a PDU session establishment request from a UE, to establish a second PDU session on a second network slice, wherein the PDU session establishment request comprises information that indicates that the PDU session is being established to remap a first PDU session of the UE on a first network slice to the PDU session on the second network slice; selecting a SMF for the PDU session on the second network slice based on the information comprised in the PDU session establishment request; and forwarding the PDU session establishment request to the selected SMF.

[0015] In one embodiment, the method wherein selecting the SMF is such that the selected SMF is the same SMF that is used for the first PDU session on the first network slice.

[0016] In one embodiment, the method wherein selecting the SMF is such that the selected SMF is a new SMF that is not used for the existing PDU session on the first network slice.

[0017] In one embodiment, the method wherein the SMF indicates, to Charging Function (CHF) (via N40 interface), to Network Exposure Function (NEF), to Network Data Analytics Function (NWDAF), and to other Network Functions (NFs) that the PDU session is established for the purpose of remapping the first network slice to the second network slice.

[0018] In one embodiment, the method further comprises receiving, from the UE, support of remapping the first network slice to the second network slice; and informing, to the UE, support of remapping the first network slice to the second network slice.

[0019] In one embodiment, the method wherein sending, to a Radio Access Network (RAN), information on the PDU session established with the second network slice.

[0020] In one embodiment, the method wherein the SMF performs a selection of a User Plane Function (UPF).

[0021] In one embodiment, the method wherein the SMF accepts the second PDU session established with the second network slice and releases the first PDU session. [0022] In one embodiment, a method performed by a UE comprises receiving, from an AMF, information that indicates that the AMF does not support remapping of network slices, wherein: remapping of network slices is a capability to remap a first PDU session established on a first network slice (e.g., in a first registration area) to a second PDU session established on a second network slice (e.g., in a second registration area); deciding, based on local configuration or UE Route Selection Policy (URSP) whether to establish a new PDU session to remap an existing PDU session established on a first network slice to the new PDU session established on a second network slice. [0023] In one embodiment, the method further comprises sending, to the AMF, information that indicates that the UE supports the remapping of network slices.

[0024] In one embodiment, a method performed by a UE comprises indicating, to an AMF, that the UE supports remapping of network slices, wherein remapping of network slices is a capability to remap a first PDU session established on a first network slice (e.g., in a first registration area) to a second PDU session established on a second network slice (e.g., in a second registration area).

[0025] In one embodiment, the method wherein a network policy is set per network slice (of Serving Public Land Mobile Network (PLMN) or of Home Public Land Mobile Network (HPLMN)) whether changing a network slice of PDU sessions for that network slice is enabled, the network policy is set locally in the AMF.

[0026] In one embodiment, the method wherein a network policy is set per network slice (of Serving Public Land Mobile Network (PLMN) or of Home Public Land Mobile Network (HPLMN)) whether changing a network slice of PDU sessions for that network slice is enabled, the network policy is enabled by a Policy Control Function (PCF).

[0027] In one embodiment, the method wherein a network policy is set per network slice (of Serving Public Land Mobile Network (PLMN) or of Home Public Land Mobile Network (HPLMN)) whether changing a network slice of PDU sessions for that network slice is enabled, the network policy is by a Network Slice Selection Function (NSSF) providing a list of network slices for Serving PLMN that each network slice of HPLMN can be changed to.

[0028] In one embodiment, the method wherein a network policy is set per network slice (of Serving Public Land Mobile Network (PLMN) or of Home Public Land Mobile Network (HPLMN)) whether changing a network slice of PDU sessions for that network slice is enabled, the network policy is set by Network Operation, Administration and Maintenance (0AM) at different 5GC node.

[0029] In one embodiment, the method wherein a network policy is set per network slice (of Serving Public Land Mobile Network (PLMN) or of Home Public Land Mobile Network (HPLMN)) whether changing a network slice of PDU sessions for that network slice is enabled, the network policy is set at a Radio Access Node (RAN).

[0030] In one embodiment, a method performed by an AMF comprises receiving a PDU session establishment request to establish a PDU session on a first network slice; selecting a SMF in association with establishment of the PDU session on the first network slice; and forwarding the PDU session establishment request to the selected SMF.

[0031] In one embodiment, the method further comprises obtaining a NF profile of the SMF that comprises information that indicates support of changing a network slice (unless enabled for whole PLMN) and support of the network slices that the PDU session can be changed between, i.e. the network slices of HPLMN that are part of the Subscribed network slices (for a SMF of HPLMN), the network slices of Serving PLMN that as per Service Level Agreement (SLA) can be used for the network slice of the HPLMN; and selecting the SMF based on the NF profile.

[0032] In one embodiment, the method wherein the AMF receives, from the UE, indication that the UE supports remapping of network slices for the PDU session, and the remapping of network slices is a capability to remap a first PDU session established on a first network slice (e.g., in a first registration area) to a second PDU session established on a second network slice (e.g., in a second registration area).

[0033] In one embodiment, the method wherein the AMF enables changing of a network slice of serving PLMN or a network slice of HPLMN.

[0034] In one embodiment, the method wherein the AMF provides, to a Service Communication Proxy (SCP), information that indicates that remapping of network slices is enabled for the PDU session.

[0035] In one embodiment, the method wherein the AMF provides, to a Service Communication Proxy (SCP), information on a list of network slices of serving PLMN or HPLMN.

[0036] In one embodiment, the method wherein the SCP uses the provided information and selects a SMF.

[0037] In one embodiment, the method wherein the AMF provides, to the SMF, a network slice for which a PDU session can be changed to.

[0038] In one embodiment, the method wherein the SMF selects a Charging Function (CHF) that supports network slices for which a PDU session can be changed between.

[0039] In one embodiment, the method wherein the SMF indicates, to the AMF, which network slices for which a PDU session can be changed between. [0040] In one embodiment, a method of performed by a 5GC comprises providing, to a RAN, a list of network slices (of serving PLMN that a PDU session can be remapped to (when activating a User Plane (UP) of the PDU session).

[0041] In one embodiment, the method further comprises sending, to the RAN, a signal including a list of network slices that the PDU session can be remapped to, and an implicit indication or an explicit indication that the remapping may be applied by the RAN at any point in time when the RAN may decide remapping is beneficial.

[0042] In one embodiment, the method wherein the RAN decides to remap a PDU session to a different network slice among the network slices provided by the 5GC if dedicated resources for a given network slice have been exhausted.

[0043] In one embodiment, the method wherein the 5GC sends, to the RAN, a signal only remapping network slices for which all core network (CN) functions serving the PDU session remain the same throughout the remapping process.

[0044] In one embodiment, the method wherein the 5GC explicitly indicates, to the RAN, a list of the indicated network slice that can be autonomously chosen by the RAN for slice remapping may comprise 5GC signaling to the RAN a flag, together with the remapping network slice list, stating that "Remapping at RAN is allowed."

[0045] In one embodiment, the method wherein the 5GC implicitly indicates, to the RAN, by signaling a list of remapping network slice that comprises a network slice that the RAN can independently choose for remapping.

[0046] In one embodiment, the method wherein the RAN indicates, to the 5GC, remapping of network slices for a PDU session to another network slice via new Information Elements (IES) in either a new procedure over a RAN-CN interface (a NG interface for the NG-RAN) or via an existing procedure.

[0047] In one embodiment, the method wherein the RAN indicates, to the 5GC, during mobility by means of a NG path switch procedure.

[0048] In one embodiment, a method performed by a RAN comprising using a list of network slices as an input to decide whether to perform a NG handover (HO) or a XN HO. [0049] In one embodiment, the method wherein the RAN triggers the NG HO, and the 5GC performs remapping of network slice. [0050] In one embodiment, the method wherein the RAN triggers the XN HO, the 5GC removes a network slice not supported at a target RAN from an allowed network slice as an outcome of a mobility registration update procedure, and a UE decides whether to establish a PDU session based on URSP or local policies.

[0051] In one embodiment, a method performed by a 5GC comprises sending, to a RAN, a list of network slices that a PDU session can be remapped to, wherein an explicit indication, to the RAN, that the list of indicated network slices that can be autonomously chosen by the RAN for slice remapping may comprises 5GC signaling to RAN a flag, together with the remapping network slice list, stating that "Remapping at RAN is allowed." The RAN may decide to remap the PDU session to a different network slice among those network slices provided by the 5GC. If the RAN performs remapping of the network slice for a Protocol Data Unit, PDU, session to another network slice, the RAN may indicate such remapping to the 5GC via new IES in either a new procedure over the RAN-CN interface (a NG interface for the RAN) or via an existing procedure such as the NG PDU session modify procedure triggered by the RAN towards the 5GC, and the RAN lets the 5GC perform a slice remapping by triggering an NG HO.

[0052] In one embodiment, a method performed by an AMF comprises determining that one or more network slices (of Serving PLMN) is not supported by a tracking area (TA); and determining that new network slices (of Serving PLMN) to be used for a PDU session (which is supported by entities of PDU session).

[0053] In one embodiment, the method wherein the AMF indicates the change of network slices to a SMF; the SMF indicates the change to a UPF; and the SMF indicates the change to a NF comprising one or more of a CHF and a PCF.

[0054] In one embodiment, the method wherein a UE selects a new cell and sends a registration request to the AMF.

[0055] In one embodiment, the method wherein the AMF uses a new network slice in allowed network slices and send the new network slice to the UE.

[0056] In one embodiment, the method wherein the UE locally changes network slice (of Serving PLMN) of PDU sessions based on changed allowed network slice because the UE has received before list of network slice that can be remapped. [0057] In one embodiment, the method wherein the UE receives, from the SMF, an explicit signaling of change of network slice for a PDU session.

[0058] In one embodiment, the method wherein, for controlling a counting of number of registered UEs for a network slice as well as PDU sessions for a network slice, the NF performs actions for decreasing a count an old network slice and increasing the count for new network slice.

[0059] In one embodiment, the method wherein the NF changes to another network slice that can replace an existing network slice.

[0060] In one embodiment, the method wherein the NF determines that one or more network slices (of serving PLMN) of requested network slice is of lower priority in a new TA and that network slice change is enabled, the NF performs a network slice change as per steps above but changes to highest prioritized network slice of TA for the UE.

Certain embodiments may provide one or more of the following technical advantage(s).

The advantages of the proposed solution enable to change the network slice (S-NSSAI) for a PDU session when moving into an area not supporting the previously used network slice (S-NSSAI).

Brief Description of the Drawings

[0061] These and other objects, features and advantages of the disclosure will become apparent from the following detailed description of illustrative embodiments thereof, which are to be read in connection with the accompanying drawings.

[0062] Fig. 1 is a diagram illustrating an example of the concept of network slicing with respect to the 3GPP 5GS;

[0063] Fig. 2 is a diagram illustrating an example of a scenario of network slicing;

[0064] Fig. 3 is a diagram illustrating one example of a cellular communications system;

[0065] Fig. 4 is a diagram illustrating a wireless communication system represented as a

5G network architecture;

[0066] Fig. 5 is a diagram illustrating a 5G network architecture using service-based interfaces;

[0067] Fig. 6A is a diagram illustrating an example in which the core network comprises two network slices;

[0068] Fig. 6B is a diagram illustrating another example that the core network comprises two network slices;

[0069] Fig. 7A is a diagram illustrating one embodiment of the present disclosure;

[0070] Fig. 7B is a diagram illustrating another embodiment of the present disclosure;

[0071] Fig. 8 is a diagram illustrating yet another embodiment of the present disclosure;

[0072] Fig. 9 is a diagram illustrating a procedure for Registration in accordance with one embodiment of the present disclosure;

[0073] Figures 10A, 10B, and 10C are diagrams illustrating a procedure for PDU Session Establishment in accordance with one embodiment of the present disclosure;

[0074] Figures 11 is a diagram illustrating a procedure of Connected mode mobility; [0075] Fig. 12A and 12B are diagrams illustrating a procedure of Idle mode mobility;

[0076] Fig. 13 is a schematic block diagram showing an apparatus suitable for use in practicing some embodiments of the disclosure;

[0077] Fig. 14 is a schematic block diagram showing an apparatus suitable for use in practicing some other embodiments of the disclosure;

[0078] Figure 15 is a schematic block diagram that illustrates a virtualized embodiment of the network node 1300 according to some embodiments of the present disclosure;

[0079] Figure 16 is a schematic block diagram of a wireless communication device 1600 according to some embodiments of the present disclosure.

[0080] Figure 17 is a schematic block diagram of the wireless communication device 1600 according to some other embodiments of the present disclosure.

Detailed Description

[0081] Generally, all terms used herein are to be interpreted according to their ordinary meaning in the relevant technical field, unless a different meaning is clearly given and/or is implied from the context in which it is used. All references to a/an/the element, apparatus, component, means, step, etc. are to be interpreted openly as referring to at least one instance of the element, apparatus, component, means, step, etc., unless explicitly stated otherwise. The steps of any methods disclosed herein do not have to be performed in the exact order disclosed, unless a step is explicitly described as following or preceding another step and/or where it is implicit that a step must follow or precede another step. Any feature of any of the embodiments disclosed herein may be applied to any other embodiment, wherever appropriate. Likewise, any advantage of any of the embodiments may apply to any other embodiments, and vice versa. Other objectives, features, and advantages of the enclosed embodiments will be apparent from the following description. [0082] Some of the embodiments contemplated herein will now be described more fully with reference to the accompanying drawings. Other embodiments, however, are contained within the scope of the subject matter disclosed herein, the disclosed subject matter should not be construed as limited to only the embodiments set forth herein; rather, these embodiments are provided by way of example to convey the scope of the subject matter to those skilled in the art.

[0083] Radio Node: As used herein, a "radio node" is either a radio access node or a wireless communication device.

[0084] 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.

[0085] 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.

[0086] 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 a wireless or wireline connection. [0087] 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 (loT) 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 a wireless connection.

[0088] 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.

[0089] 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. [0090] 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.

[0091] 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.

[0092] Figure 3 illustrates one example of a cellular communications system 300 in which embodiments of the present disclosure may be implemented. In the embodiments described herein, the cellular communications system 300 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 302-1 and 302-2, 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 304-1 and 304-2. The base stations 302-1 and 302-2 are generally referred to herein collectively as base stations 302 and individually as base station 302. Likewise, the (macro) cells 304-1 and 304-2 are generally referred to herein collectively as (macro) cells 304 and individually as (macro) cell 304. The RAN may also include a number of low power nodes 306-1 through 306-4 controlling corresponding small cells 308-1 through 308-4. The low power nodes 306-1 through 306-4 can be small base stations (such as pico or femto base stations) or Remote Radio Heads (RRHs), or the like. Notably, while not illustrated, one or more of the small cells 308-1 through 308-4 may alternatively be provided by the base stations 302. The low power nodes 306-1 through 306-4 are generally referred to herein collectively as low power nodes 306 and individually as low power node 306. Likewise, the small cells 308-1 through 308-4 are generally referred to herein collectively as small cells 308 and individually as small cell 308. The cellular communications system 300 also includes a core network 310, which in the 5G System (5GS) is referred to as the 5GC. The base stations 302 (and optionally the low power nodes 306) are connected to the core network 310.

[0093] The base stations 302 and the low power nodes 306 provide service to wireless communication devices 312-1 through 312-5 in the corresponding cells 304 and 308. The wireless communication devices 312-1 through 312-5 are generally referred to herein collectively as wireless communication devices 312 and individually as wireless communication device 312. In the following description, the wireless communication devices 312 are oftentimes UEs, but the present disclosure is not limited thereto.

[0094] Figure 4 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 4 can be viewed as one particular implementation of the system 300 of Figure 3.

[0095] Seen from the access side the 5G network architecture shown in Figure 4 comprises a plurality of UEs 312 connected to either a RAN 302 or an Access Network (AN) as well as an AMF 400. Typically, the R(AN) 302 comprises base stations, e.g. such as eNBs or gNBs or similar. Seen from the core network side, the 5GC NFs shown in Figure 4 include a NSSF 402, an AUSF 404, a UDM 406, the AMF 400, a SMF 408, a PCF 410, and an Application Function (AF) 412.

[0096] 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 312 and the AMF 400. The reference points for connecting between the AN 302 and the AMF 400 and between the AN 302 and UPF 414 are defined as N2 and N3, respectively. There is a reference point, Nil, between the AMF 400 and SMF 408, which implies that the SMF 408 is at least partly controlled by the AMF 400. N4 is used by the SMF 408 and UPF 414 so that the UPF 414 can be set using the control signal generated by the SMF 408, and the UPF 414 can report its state to the SMF 408. N9 is the reference point for the connection between different UPFs 414, and N14 is the reference point connecting between different AMFs 400, respectively. N15 and N7 are defined since the PCF 410 applies policy to the AMF 400 and SMF 408, respectively. N12 is required for the AMF 400 to perform authentication of the UE 312. N8 and N10 are defined because the subscription data of the UE 312 is required for the AMF 400 and SMF 408.

[0097] The 5GC network aims at separating UP and CP. The UP carries user traffic while the CP carries signaling in the network. In Figure 4, the UPF 414 is in the UP and all other NFs, i.e., the AMF 400, SMF 408, PCF 410, AF 412, NSSF 402, AUSF 404, and UDM 406, 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.

[0098] The core 5G network architecture is composed of modularized functions. For example, the AMF 400 and SMF 408 are independent functions in the CP. Separated AMF 400 and SMF 408 allow independent evolution and scaling. Other CP functions like the PCF 410 and AUSF 404 can be separated as shown in Figure 4. Modularized function design enables the 5GC network to support various services flexibly.

[0099] 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.

[0100] Figure 5 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 4. However, the NFs described above with reference to Figure 4 correspond to the NFs shown in Figure 5. 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 5 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 400 and Nsmf for the service based interface of the SMF 408, etc. The NEF 500 and the NRF 502 in Figure 5 are not shown in Figure 4 discussed above. However, it should be clarified that all NFs depicted in Figure 4 can interact with the NEF 500 and the NRF 502 of Figure 5 as necessary, though not explicitly indicated in Figure 4.

[0101] Some properties of the NFs shown in Figures 4 and 5 may be described in the following manner. The AMF 400 provides UE-based authentication, authorization, mobility management, etc. A UE 312 even using multiple access technologies is basically connected to a single AMF 400 because the AMF 400 is independent of the access technologies. The SMF 408 is responsible for session management and allocates Internet Protocol (IP) addresses to UEs. It also selects and controls the UPF 414 for data transfer. If a UE 312 has multiple sessions, different SMFs 408 may be allocated to each session to manage them individually and possibly provide different functionalities per session. The AF 412 provides information on the packet flow to the PCF 410 responsible for policy control in order to support QoS. Based on the information, the PCF 410 determines policies about mobility and session management to make the AMF 400 and SMF 408 operate properly. The AUSF 404 supports authentication function for UEs or similar and thus stores data for authentication of UEs or similar while the UDM 406 stores subscription data of the UE 312. The Data Network (DN), not part of the 5GC network, provides Internet access or operator services and similar.

[0102] 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.

[0103] Figure 6A illustrates an example in which the core network 310 comprises two network slices (Network Slice 1 and Network Slice 2) that include comment elements like AMF 400-X, SMF 408-X, CHF 602, NEF 604, NWDAF 606. SCP 600-X is connected to AMF 400-X and is included in the Network Slice 1. As illustrated in Figure 6A, UE(s) 312 and (R)AN 302 are connected to AMF 400-X. SMF 408-X is connected to AMF 400-X and UPF 414. As an example, Network Slice 1 may correspond to S-NSSAI x in the example of Figure 2, and Network Slice 2 may correspond to S-NSSAI y in the example of Figure 2. Notably, in this example, the same SMF 408-X (and the same AMF 400-X, but not necessarily) is part of both Network Slice 1 and Network Slice 2. Thus, this is an example of an SMF that can support both of the network slices. As such, in some embodiments, this same SMF 408-X may be selected when remapping from Network Slice 1 to Network Slice 2 or vice versa.

[0104] Figure 6B illustrates another example that the core network 310 comprises two network slices (Network Slice 1 and Network Slice 2) that include comment elements like CHF 602, NEF 604, NWDAF 606, while each of Network Slice respectively includes AMF, SMF, and SCP. In other words, Network Slice 1 includes AMF 400-X, SMF 408-X, and SCP 600-X; Network Slice 2 includes AMF 400-Y, SMF 408-Y, and SCP 600-Y. As illustrated in Figure 6B, UE(s) 312 and (R)AN 302 are connected to both of AMF 400-X and AMF 400-Y. (R)AN 302 is also connected to both of UPF 414-X and UPF414-Y.

[0105] As used herein, "remapping a network slice" or "remapping S-NSSAI" is a feature by which a first network slice (e.g., S-NSSAI x in Figure 2) in a first registration area (e.g., Registration Area 1 in Figure 2) can be remapped to a second network slice (e.g., S-NSSAI y in Figure 2) available in a second registration area (e.g., Registration Area 2 in Figure 2) or in the same Registration Area (e.g., Registration Area 1 in Figure 2). In other words, a first session(s) (e.g., first PDU session(s)) established by a UE on a first network slice (e.g., a first S-NSSAI) when in a first Registration Area can be remapped to a second session(s) (e.g., second PDU session(s)) established by the UE on a second network slice (e.g., a second S-NSSAI) when in a second Registration Area. Further, in some embodiments, this remapping is done in such a way that the same SMF that was used for the first session(s) on the first network slice is selected (for the same DNN) for the second session(s) on the second network slice.

[0106] Solution 1: Figures 7A and 7B illustrate one example of a first solution proposed in the present disclosure. Optional features are represented by dashed boxes. As illustrated, the UE 312 indicates, during registration to an Access and Mobile Management Function (AMF) 410, that the UE 312 supports "remapping S-NSSAI" (step 700). The AMF 410 also indicates, to the UE 312, that the AMF 410 supports "remapping S-NSSAI" (step 702). In one embodiment, the indication is made on a per network slice (S-NSSAI) basis but is not limited thereto. In one particular embodiment, the indication for a network slice (S-NSSAI) can include or otherwise indicate a list of other network slices (other S-NSSAIs) that can be remapped into the network slice, or vice versa. Such indication may also be sent from the AMF 410 to the Radio Access Node (RAN) 302. Configuration of the list of network slices (S-NSSAIs) that can be remapped into a particular network slice may be provided by the Network Operation, Administration and Maintenance (0AM) system to the fifth generation core network (5GC) 310, e.g., to the AMF 410, and to the RAN 302. In this way, the AMF 410 and the RAN 302 may not need to signal this information between each other. [0107] First Case of Solution 1: Both the UE 312 and network support "Remapping S-NSSAI." In this case, the UE 312 is using a first PDU session for a first network slice (e.g., S-NSSAI x in Registration Area 1 of Figure 2), wherein the first PDU session is associated with the first network slice (e.g., S-NSSAI x) in the respective Registration Area (step 704). When the UE 312 moves to a new Registration Area (e.g., Registration Area 2 in Figure 2) and receives a set of Allowed S-NSSAIs (which may include one or more Allowed S-NSSAIs) that does not include the first network slice (e.g., S-NSSAI x in Registration Area 1 of Figure 2) (step 706), then the following actions are performed.

• The UE 312 determines a remapped (second) network slice (e.g., S-NSSAI y in Figure 2) that is to be used in the new Registration Area instead of the first network slice (e.g., S-NSSAI x in Figure 2) for a new (second) PDU session (step 708).

• The UE 312 establishes a new (second) PDU session, indicating, to the fifth generation core network (5GC) 310, the remapped second network slice (e.g., S- NSSAI y) on which the new PDU session is to be established. In addition, the UE 312 indicates, to the 5GC, the first network slice (e.g., S-NSSAI x) and a PDU session Identification (ID) of existing (first) PDU session established on the first network slice (step 710).

• The AMF 410 determines, for the new PDU session, whether the same SMF 408-X can be selected as for the existing PDU session, even though a different S-NSSAI (e.g., S-NSSAI y) is selected for the new PDU session (step 712). For example, the AMF 410 may determine whether the SMF associated to the PDU session ID of the existing PDU session and the first network slice (e.g., S-NSSAI x) also supports the second network slice (e.g., S-NSSAI y) selected for the new PDU session. This may be done by, for example, querying one or more other network nodes in the 5GC (e.g., the NRF, SMFs, etc.). o If the same Session Management Function (SMF 408-X) can be selected, then the request is forwarded from the AMF 410-X to the SMF 408-X (step 718) and the SMF 408-X decides which User Plane Function (UPF 414) to select (step 720). ■ The UE 312 may receive the same IP address or a new IP address (step 722).

■ The SMF 408-X accepts the new PDU session associated to the remapped (second) network slice (e.g., S-NSSAI y), and then releases the first (original) PDU session associated to the first network slice (e.g., S-NSSAI x) after a timeout (e.g., the time it may take for the UE 312 to release the first (old) PDU session) (step 724). o If a new SMF 408-Y is selected, the request from the AMF 410-Y is forwarded to the new SMF 408-Y (step 726) and the new SMF 408-Y decides which UPF 414 to select (728).

■ The UE 312 receives a new IP address (step 730).

■ The new SMF 408-Y accepts the new PDU session (although the new SMF 408-Y may reject the new PDU session as well). The UE 312 must release the first (old) PDU session (step 732). o The SMF 408-Y can indicate, to Charging Function (CHF) (via N40), to Network Exposure Function (NEF), to Network Data Analytics Function (NWDAF) and/or to other Network Functions (NFs), that the new PDU session is established for the purpose of remapping the network slice (S- NSSAI) (step 734).

• The UE 312 routes all PDUs, so far routed via the first PDU session associated with the first network slice (e.g., S-NSSAI x), via the new PDU session associated with the second network slice (e.g., S-NSSAI y) (step 736).

• When the new PDU session with a remapped network slice (e.g., S-NSSAI y) is established, the AMF 410 may signal the RAN 302 with this information (step 738). The RAN 302 is therefore informed that the new (second) PDU session is derived from a PDU session of a different network slice (e.g., S-NSSAI y), which is not supported at the RAN 302.

[0108] Second Case of Solution 1: Network does not support "Remapping S- NSSAI." Figure 8 illustrates a case where the network (e.g., AMF 410) does not support "Remapping S-NSSAI." Optional features are represented by dashed boxes. If the AMF 410 does not support "Remapping S-NSSAI", then the UE 312 decides, based on local configuration or UE Route Selection Policy (URSP), whether to establish a new PDU session using the second network slice (e.g., S-NSSAI y) for the traffic previously handled by the first network slice (e.g., S-NSSAI x).

[0109] Solution 2: To prepare for the possibility of doing a remapping of network slice used for a PDU session, the following impacts to the procedures are envisioned in this solution: Registration, PDU Session Establishment, Connected mode mobility, and Idle mode mobility.

[0110] Figure 9 illustrates a procedure for Registration in accordance with one embodiment of the present disclosure. Optional features are represented by dashed boxes. The steps of this procedure are as follows:

• UE 312 indicates its support for "Remapping S-NSSAI" (of PDU Sessions) during registration to the AMF 410 (step 900).

• Optionally, a network policy is set per network slice (S-NSSAI) (of Serving Public Land Mobile Network (PLMN) or of Home PLMN (HPLMN)) whether changing network slice (S-NSSAI) of PDU Sessions for that network slice (S-NSSAI) is enabled (step 904): o The policy can be set locally in Access and Mobility Management Function (AMF 410) (step 906), or o The policy can be enabled by Policy Control Function (PCF 410) (step 908), o The policy can be enabled by Network Slice Selection Function (NSSF 402) providing a list of network slices (S-NSSAIs) for Serving PLMN that each network slice (S-NSSAI) of HPLMN can be changed to (step 910), or o The policy can be set by Network Operation, Administration and Maintenance (0AM) at different fifth generation core network (5GC) nodes and optionally at the RAN 302 (step 912).

[0111] Figures 10A, 10B, and 10C illustrate a procedure for PDU Session Establishment in accordance with one embodiment of the present disclosure. Optional features are represented by dashed boxes. As illustrated, the AMF 400 receives a Protocol Data Unit (PDU) session establishment request to establish a PDU session on a first network slice (step 1000). The AMF 400 selects a SMF 408, in association with establishment of the PDU session on the first network slice (step 1002), and the AMF 400 forwards the PDU session establishment request to the selected SMF 408 (step 1004). [0112] When, as per current procedures, a network slice (S-NSSAI) is determined for a PDU session (i.e., based on a network slice (S-NSSAI) provided by UE 312 or determined by AMF 410), the AMF 410 performs SMF discovery and selection (as per Third Generation Partnership Project (3GPP) Technical Specification (TS) 23.501 v16.7.0 (2020-12), “System architecture for the 5G System (5GS),” clause 6.3.2):

/// Start of TS 23.501 III

6.3.2 SMF discovery and selection

The SMF selection functionality is supported by the AMF and SCP and is used to allocate an SMF that shall manage the PDU Session. The SMF selection procedures are described in clause 4.3.2.2.3 of TS 23.502 [3],

The SMF discovery and selection functionality follows the principles stated in clause 6.3.1.

If the AMF does discovery, the AMF shall utilize the NRF to discover SMF instance(s) unless SMF information is available by other means, e.g. locally configured on AMF. The AMF provides UE location information to the NRF when trying to discover SMF instance(s). The NRF provides NF profile(s) of SMF instance(s) to the AMF. In addition, the NRF also provides the SMF service area of SMF instance(s) to the AMF. The SMF selection functionality in the AMF selects an SMF instance and an SMF service instance based on the available SMF instances obtained from NRF or on the configured SMF information in the AMF.

NOTE 1 : Protocol aspects of the access to NRF are specified in TS 29.510 [58],

The SMF selection functionality is applicable to both 3GPP access and non-3GPP access.

The SMF selection for Emergency services is described in clause 5.16.4.5.

The following factors may be considered during the SMF selection: a) Selected Data Network Name (DNN). In the case of the home routed roaming, the DNN is not applied for the V-SMF selection. b) S-NSSAI of the HPLMN (for non-roaming and home-routed roaming scenarios), and S- NSSAI of the VPLMN (for roaming with local breakout and home-routed roaming scenarios). c) NSI-ID.

NOTE 2: The use of NSI -ID in the network is optional and depends on the deployment choices of the operator. If used, the NSI ID is associated with S-NSSAI. d) Access technology being used by the UE. e) Support for Control Plane CIoT 5GS Optimisation. f) Subscription information from UDM, e.g. - per DNN: whether LBO roaming is allowed.

- per S-NSSAI: the subscribed DNN(s).

- per (S-NSSAI, subscribed DNN): whether LBO roaming is allowed.

- per (S-NSSAI, subscribed DNN): whether EPC interworking is supported.

- per (S-NSSAI, subscribed DNN): whether selecting the same SMF for all PDU sessions to the same S-NSSAI and DNN is required. g) Void. h) Local operator policies.

NOTE 3 : These policies can take into account whether the SMF to be selected is an LSMF or a V-SMF or a SMF. i) Load conditions of the candidate SMFs. j) Analytics (i.e. statistics or predictions) for candidate SMFs' load as received from NWDAF (see TS 23.288 [86]), if NWDAF is deployed. k) UE location (i.e. TA). l) Service Area of the candidate SMFs. m) Capability of the SMF to support a MA PDU Session. n) If interworking with EPS is required. o) Preference of V-SMF support. This is applicable only for V-SMF selection in the case of home routed roaming.

To support the allocation of a static IPv4 address and/or a static IPv6 prefix as specified in clause 5.8.2.2.1, a dedicated SMF may be deployed for the indicated combination of DNN and S- NSSAI and registered to the NRF, or provided by the UDM as part of the subscription data.

In the case of delegated discovery, the AMF, shall send all the available factors a)-d), k) and n) to the SCP.

In addition, the AMF may indicate to the SCP which NRF to use (in the case of NRF dedicated to the target slice).

If there is an existing PDU Session and the UE requests to establish another PDU Session to the same DNN and S-NSSAI of the HPLMN, and the UE subscription data indicates the support for interworking with EPS for this DNN and S-NSSAI of the HPLMN or UE subscription data indicates the same SMF shall be selected for all PDU sessions to the same S-NSSAI, DNN, the same SMF in non roaming and LBO case or the same H-SMF in home routed roaming case, shall be selected. In addition, if the UE Context in the AMF provides a SMF ID for an existing PDU session to the same DNN, S-NSSAI, the AMF uses the stored SMF ID for the additional PDU Session. In any such a case where the AMF can determine which SMF should be selected, if delegated discovery is used, the AMF shall indicate a desired NF Instance ID so that the SCP is able to route the message to the relevant SMF. Otherwise, if UE subscription data does not indicate the support for interworking with EPS for this DNN and S -NS SAI, a different SMF in non roaming and LBO case or a different H- SMF in home routed roaming case, may be selected. For example, to support a SMF load balancing or to support a graceful SMF shutdown (e.g., a SMF starts to no more take new PDU Sessions).

In the home-routed roaming case, the SMF selection functionality selects an SMF in VPLMN based on the S-NSSAI of the VPLMN, as well as an SMF in HPLMN based on the S-NSSAI of the HPLMN. This is specified in clause 4.3.2.2.3.3 of TS 23.502 [3],

When the UE requests to establish a PDU Session to a DNN and an S-NSSAI of the HPLMN, if the UE MM Core Network Capability indicates the UE supports EPC NAS and optionally, if the UE subscription indicates the support for interworking with EPS for this DNN and S-NSSAI of the HPLMN, the selection functionality (in AMF or SCP) selects a combined SMF+PGW-C. Otherwise, a standalone SMF may be selected.

If the UDM provides a subscription context that allows for handling the PDU Session in the VPLMN (i.e. using LBO) for this DNN and S-NSSAI of the HPLMN and, optionally, the AMF is configured to know that the VPLMN has a suitable roaming agreement with the HPLMN of the UE, the following applies:

- If the AMF does discovery, the SMF selection functionality in AMF selects an SMF from the VPLMN.

- If delegated discovery is used, the SCP selects an SMF from the VPLMN.

If an SMF in the VPLMN cannot be derived for the DNN and S-NSSAI of the VPLMN, or if the subscription does not allow for handling the PDU Session in the VPLMN using LBO, then the following applies:

- If the AMF does discovery, both an SMF in VPLMN and an SMF in HPLMN are selected, and the DNN and S-NSSAI of the HPLMN is used to derive an SMF identifier from the HPLMN.

- If delegated discovery is used:

- The AMF performs discovery and selection of H-SMF from NRF. The AMF may indicate the maximum number of H-SMF instances to be returned from NRF, i.e. SMF selection at NRF.

- The AMF sends Nsmf PDUSession CreateSMContext Request to SCP, which includes the endpoint (e.g. URI) of the selected H-SMF, and the discovery and selection parameters as defined in this clause, i.e. parameter for V-SMF selection. The SCP performs discovery and selection of the V-SMF and forwards the request to the selected V-SMF.

- The V-SMF sends the Nsmf PDUSession Create Request towards the H-SMF via the SCP; the V-SMF uses the received endpoint (e.g. URI) of the selected H-SMF to construct the target destination to be addressed. The SCP forwards the request to the H-SMF.

- Upon reception of a response from V-SMF, based on the received V-SMF ID the AMF obtains the Service Area of the V-SMF from NRF. The AMF uses the Service Area of the V-SMF to determine the need for V-SMF relocation upon subsequent UE mobility.

If the initially selected SMF in VPLMN (for roaming with LBO) detects it does not understand information in the UE request, it may reject the N11 message (related with a PDU Session Establishment Request message) with a proper N11 cause triggering the AMF to select both a new SMF in the VPLMN and a SMF in the HPLMN (for home routed roaming).

The AMF selects SMF(s) considering support for CIoT 5GS optimisations (e.g. Control Plane CIoT 5GS Optimisation).

Additional details of AMF selection of an I-SMF are described in clause 5.34.

In the case of home routed scenario, the AMF selects a new V-SMF if it determines that the current V-SMF cannot serve the UE location. The selection/relocation is same as an I-SMF selection/relocation as described in clause 5.34.

/// End of TS 23.501 III

[0113] The present disclosure proposes the following changes to 3GPP TS 23.501 , clause 6.3.2: a. If the UE 312 indicated its support for “remapping S-NSSAI” of PDU Sessions (step 1006), and if changing network slice (S-NSSAI) is enabled for the network slice (S- NSSAI) (this can be for the network slice (S-NSSAI) of Serving PLMN or for the network slice (S-NSSAI) of HPLMN) (step 1008), i. The AMF 410 selects an SMF 408 that is indicated in a NF Profile (step 1010)) that the SMF 408:

1 . supports changing network slice (S-NSSAI) (unless enabled for whole PLMN)

2. supports the network slices (S-NSSAIs) that the PDU Session can be changed between, i.e. , the network slices (S-NSSAIs) of HPLMN that are part of the Subscribed network slices (S-NSSAIs) (for SMF 408 of HPLMN), the network slices (S-NSSAIs) of Serving PLMN that as per Service Level Agreement (SLA) can be used for the network slice (S-NSSAI) of the HPLMN. b. If delegated discovery is used, the AMF 410 additionally provides the following information to the Service Communication Proxy (SCP) 600 for SMF selection: i. “remapping S-NSSAI” is enabled (step 1012), ii. Optionally, list of network slices (S-NSSAIs) of Serving PLMN (step 1014), iii. Optionally, list of network slices (S-NSSAIs) of HPLMN (step 1014).

The SCP 600 uses the additional information to select a SMF 408 that as far as possible supports network slices (S-NSSAIs) that can be used when changing network slices (S-NSSAIs) (step 1016). [0114] To enable the SMF 408 to select a UPF 414 that supports the appropriate network slices (S-NSSAIs), the AMF 410 may provide, to the SMF 408, the network slices (S-NSSAIs) for which the PDU Session can be changed (step 1022).

[0115] The SMF 408 also selects a Charging Function, CHF, that supports the network slices (S-NSSAIs) for which the PDU Session can be changed between (step 1024).

[0116] The SMF 408 may indicate to the AMF 410 (to UPF 414 and CHF as well), e.g., based on the network slices (S-NSSAIs) supported by the SMF 408, which network slices (S-NSSAIs) the PDU Session can be changed between (step 1026).

[0117] When activating the User Plane (UP) of the PDU Session, the 5GC 310 (e.g., SMF 408 or AMF 410) provides, to the Next Generation Radio Access Network, a list of network slices (S-NSSAIs) (of Serving PLMN) that the PDU Session can be remapped to (step 1032).

[0118] In one embodiment of the PDU session establishment procedure of Figures 10A-10C, the 5GC 310 may signal to the RAN 302 the list of network slice (S-NSSAI) the PDU Session can be remapped to, as well as an implicit or explicit indication that the remapping may be applied by the RAN 302 at any point in time when the RAN 302 may decide the remapping is beneficial (step 1032). For example, if dedicated resources for a given network slice (S-NSSAI) have been exhausted, the RAN 302 may decide to remap the PDU Session to a different network slice (S-NSSAI) among those provided by the fifth generation core network (5GC) 310 (step 1036).

[0119] The 5CG may signal to the RAN 302 only remapping network slices (S-NSSAIs) for which all Core Network (CN) functions serving the PDU Session remain the same throughout the remapping process (step 1038). An explicit indication to the RAN 302 that the list of indicated network slices (S-NSSAIs) that can be autonomously chosen by the RAN 302 for slice remapping may comprise 5GC signalling to the RAN 302 a flag, together with the remapping network slice (S-NSSAI) list, stating that "Remapping at RAN is allowed" (step 1040). An implicit way of signalling such information to the RAN 302 may be signalled by the fifth generation core network (5GC) 310 by means of purely signalling the list of remapping network slice (S-NSSAI) to the RAN 302 (implicitly indicating that the list comprises network slices (S-NSSAIs) the RAN 302 can independently choose for remapping) (step 1042). [0120] If the RAN 302 performs remapping of the network slice (S-NSSAI) for a PDU Session to another network slice (S-NSSAI), the RAN 302 may indicate such remapping to the fifth generation core network (5GC) 310 via new Information Elements (IES) in either a new procedure over the RAN-CN interface (the NG interface for the NG-RAN) or via an existing procedure such as the NG: PDU SESSION MODIFY procedure triggered by the RAN 302 towards the fifth generation core network (5GC) 310 (step 1044). Alternatively, the remapping may be indicated during mobility by means of the NG PATH SWITCH procedure (step 1046).

[0121] Figure 11 illustrates a procedure of Connected mode mobility. Optional features are represented by dashed boxes. The NG-RAN uses the list of network slices (S-NSSAIs) as an input to decide whether to perform NG Handover (HO) or Xn HO. If at least one PDU Session cannot be supported by target NG-RAN due to the network slice (S-NSSAI) of a PDU Session used by the UE 312 at the source RAN not being available at the target RAN, but that the target NG-RAN supports a network slice (S-NSSAI) of the list of network slices (S-NSSAIs) that can be used for remapping of the source network slice (S-NSSAI) (step 1100), then the NG-RAN lets the fifth generation core network (5GC) 310 perform a slice remapping by triggering an NG HO (step 1102A).

[0122] During such NG HO, the CN may perform network slice (S-NSSAI) remapping as per the methods described above (step 1104). If Xn HO is triggered by the RAN 302 (step 1102B), then PDU Session UP for the network slice (S-NSSAI) that is not supported in the target RAN is removed by the source NG-RAN (step 1106) and AMF 410 also removes network slice (S-NSSAI) not supported at target RAN from the Allowed NSSAI as an outcome of the Mobility Registration Update procedure (step 1108), and the UE 312 then decides whether to establish a new PDU Session based on URSP or local policies (step 1110).

[0123] Figures 12A and 12B illustrate a procedure of Idle mode mobility. Optional features are represented by dashed boxes. The UE 312 selects a new cell and initiates a Mobility Registration Update procedure by sending a registration request to the AMF 410 (step 1200). The AMF 410 determines that one or more network slices (S-NSSAIs) (of Serving PLMN) is not supported by the Tracking Area (TA) (step 1204), and the AMF 410 does the following: a. For each PDU Session, the AMF 410 determines a new network slice (S-NSSAI) (of Serving PLMN) to be used for the PDU Session (which is supported by the entities of the PDU Session) (step 1206) and indicates the change to the SMF 408 (V-SMF) (step 1208), the SMF indicates the change to the UPF 414 (step 1210), the SMF 408 also indicates the change to the CHF and to the PCF 410 (step 1212). b. The AMF 410 uses the new network slice (S-NSSAI) in the Allowed NSSAI and sends the new network slice (S-NSSAI) to the UE 312 (step 1214) i. The UE 312 may locally change the network slice (S-NSSAI) (of Serving PLMN) of the PDU Sessions based on the changed Allowed NSSAI because the UE 312 has received before the list of network slice (S-NSSAI) that can be remapped (step 1216A)

1 . Alternatively, the change can be indicated by explicit SM signaling by each SMF 408 (but requires much more signaling) (step 1216B) [0124] The NFs controlling the counting of number of registered UEs for a network slice as well as PDU Sessions for a network slice may need to perform the actions for decreasing the count for the original network slice (S-NSSAI) and increase the network slice (S-NSSAI) for the new network slice (S-NSSAI) (step 1222). The logic may be done before updating the SMF 408 as to check that there is enough quota for the network slice (S-NSSAI) before changing the PDU Sessions, and if quota is reached for one S-NSAI the NF may change to another one of the network slice (S-NSSAI) that can replace the existing network slice (S-NSSAI) (step 1224).

[0125] Optionally, (e.g. to cover the case when the UE 312 moves back to Registration Area 1 and to enable that the UE 312 again can use the original network slice (e.g., S- NSSAI x)), the AMF 410 determines that one or more network slices (S-NSSAIs) (of Serving PLMN) of the Requested NSSAI is of lower priority in the new TA, and that S- NSSAI change is enabled, the AMF 410 then may perform a network slice (S-NSSAI) change as per steps above but changes to the highest prioritized network slice (S-NSSAI) of the TA for the UE 312 (step 1226).

[0126] Figure 13 is a schematic block diagram of a network node 1300 according to some embodiments of the present disclosure. Optional features are represented by dashed boxes. The network node 1300 may be, for example, a base station 302 or 306 or a network node that implements all or part of the functionality of the base station 302 or gNB, a network node that implements a NF (e.g., AMF 400, SMF 408, SCP 600, or any other NF of the 5GC). As illustrated, the network node 1300 includes a control system 1302 that includes one or more processors 1304 (e.g., Central Processing Units (CPUs), Application Specific Integrated Circuits (ASICs), Field Programmable Gate Arrays (FPGAs), and/or the like), memory 1306, and a network interface 1308. The one or more processors 1304 are also referred to herein as processing circuitry. In addition, if the network node 1300 is a radio access node (e.g., a base station 302), the network node 1300 may include one or more radio units 1310 that each includes one or more transmitters 1312 and one or more receivers 1314 coupled to one or more antennas 1316. The radio units 1310 may be referred to or be part of radio interface circuitry. In some embodiments, the radio unit(s) 1310 is external to the control system 1302 and connected to the control system 1302 via, e.g., a wired connection (e.g., an optical cable). However, in some other embodiments, the radio unit(s) 1310 and potentially the antenna(s) 1316 are integrated together with the control system 1302. The one or more processors 1304 operate to provide one or more functions of the network node 1300 as described herein (e.g., one or more functions of the RAN or a RAN node such as the base station 302, a NF of the core network 310 (e.g., the AMF 400, SMF 408, SCP 600, or any other NF), as described herein). In some embodiments, the function(s) are implemented in software that is stored, e.g., in the memory 1306 and executed by the one or more processors 1304.

[0127] Figure 15 is a schematic block diagram that illustrates a virtualized embodiment of the network node 1300 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.

[0128] As used herein, a "virtualized" network node is an implementation of the network node 1300 in which at least a portion of the functionality of the network node 1300 is implemented as a virtual component(s) (e.g., via a virtual machine(s) executing on a physical processing node(s) in a network(s)). As illustrated, in this example, the network node 1300 includes one or more processing nodes 1500 coupled to or included as part of a network(s) 1502. Each processing node 1500 includes one or more processors 1504 (e.g., CPUs, ASICs, FPGAs, and/or the like), memory 1506, and a network interface 1508. If the network node 1300 is a radio access node, the network node 1300 may also include the control system 1302 and/or the one or more radio units 1310, as described above. The control system 1302 may be connected to the radio unit(s) 1310 via, for example, an optical cable or the like. If present, the control system 1302 or the radio unit(s) are connected to the processing node(s) 1500 via the network 1502.

[0129] In this example, functions 1510 of the network node 1300 described herein (e.g., one or more functions of the RAN or a RAN node such as the base station 302, a NF of the core network 310 (e.g., the AMF 400, SMF 408, SCP 600, or any other NF), as described herein) are implemented at the one or more processing nodes 1500 or distributed across the one or more processing nodes 1500 and the control system 1302 and/or the radio unit(s) 1310 in any desired manner. In some particular embodiments, some or all of the functions 1510 of the network node 1300 described herein are implemented as virtual components executed by one or more virtual machines implemented in a virtual environ ment(s) hosted by the processing node(s) 1500. As will be appreciated by one of ordinary skill in the art, additional signaling or communication between the processing node(s) 1500 and the control system 1302 is used in order to carry out at least some of the desired functions 1510. Notably, in some embodiments, the control system 1302 may not be included, in which case the radio unit(s) 1310 communicate directly with the processing node(s) 1500 via an appropriate network interface(s).

[0130] 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 network node 1300 or a node (e.g., a processing node 1500) implementing one or more of the functions 1510 of the network node 1300 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). [0131] Figure 14 is a schematic block diagram of the network node 1300 according to some other embodiments of the present disclosure. The network node 1300 includes one or more modules 1400, each of which is implemented in software. The module(s) 1400 provide the functionality of the network node 1300 described herein. This discussion is equally applicable to the processing node 1500 of Figure 15 where the modules 1400 may be implemented at one of the processing nodes 1500 or distributed across multiple processing nodes 1500 and/or distributed across the processing node(s) 1500 and the control system 1302.

[0132] Figure 16 is a schematic block diagram of a wireless communication device 1600 according to some embodiments of the present disclosure. As illustrated, the wireless communication device 1600 includes one or more processors 1602 (e.g., CPUs, ASICs, FPGAs, and/or the like), memory 1604, and one or more transceivers 1606 each including one or more transmitters 1608 and one or more receivers 1610 coupled to one or more antennas 1612. The transceiver(s) 1606 includes radio-front end circuitry connected to the antenna(s) 1612 that is configured to condition signals communicated between the antenna(s) 1612 and the processor(s) 1602, as will be appreciated by on of ordinary skill in the art. The processors 1602 are also referred to herein as processing circuitry. The transceivers 1606 are also referred to herein as radio circuitry. In some embodiments, the functionality of the wireless communication device 1600 described above may be fully or partially implemented in software that is, e.g., stored in the memory 1604 and executed by the processor(s) 1602. Note that the wireless communication device 1600 may include additional components not illustrated in Figure 16 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 1600 and/or allowing output of information from the wireless communication device 1600), a power supply (e.g., a battery and associated power circuitry), etc.

[0133] 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 1600 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).

[0134] Figure 17 is a schematic block diagram of the wireless communication device 1600 according to some other embodiments of the present disclosure. The wireless communication device 1600 includes one or more modules 1700, each of which is implemented in software. The module(s) 1700 provide the functionality of the wireless communication device 1600 described herein. 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), specialpurpose 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.

[0135] 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.).

[0136] 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 Management Function

AN Access Network

ASIC Application Specific Integrated Circuit

AUSF Authentication Server Function

CHF Charging Function

CN Core Network

CPU Central Processing Unit

DN Data Network

DNN Data Network Name

DSP Digital Signal Processor eNB Enhanced or Evolved Node B

EPC Evolved Packet Core

E-UTRA Evolved Universal Terrestrial Radio Access

FPGA Field Programmable Gate Array

HO Handover

HPLMN Home Public Land Mobile Network gNB New Radio Base Station gNB-CU New Radio Base Station Central Unit gNB-DU New Radio Base Station Distributed Unit

HSS Home Subscriber Server

IE Information Element loT Internet of Things

IP Internet Protocol LTE Long Term Evolution

MME Mobility Management Entity

MRU Mobility Registration Update

MTC Machine Type Communication

NEF Network Exposure Function

NF Network Function

NR New Radio

NRF Network Function Repository Function

NSSAI Network Slice Selection Assistance Information

NSSF Network Slice Selection Function

NWDAF Network Data Analytics Function

OAM Network Operation, Administration and Maintenance

OTT Over-the-Top

PC Personal Computer

PCF Policy Control Function

PDU Protocol Data Unit

P-GW Packet Data Network Gateway

QoS Quality of Service

RA Registration Area

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

SCP Service Communication Proxy

SLA Service Level Agreement

SMF Session Management Function

S-NSSAI Single Network Slice Selection Assistance Information

TA Tracking Area TCI Transmission Configuration Indicator

TRP Transmission/Reception Point

UDM Unified Data Management

UDR Unified Data Management Function UE User Equipment

UPF User Plane Function

URSP User Equipment Route Selection Policy

Claims

36 Claims What is claimed is:

1. A method performed by a User Equipment, UE (312), comprising:

• using (704) a first Protocol Data Unit, PDU, session on a first network slice in a source registration area;

• moving (706) to a second registration area in which the first network slice is not an allowed network slice;

• determining (708) that the first network slice can be remapped to a second network slice, the second network slice being an allowed network slice in the second registration area; and

• sending (710) a PDU session establishment request to a first network node to initiate establishment of a second PDU session on the second network slice, wherein o the PDU session establishment request comprises information that indicates that the second PDU session is being established to remap the first PDU session on the first network slice to the second PDU session on the second network slice.

2. The method of claim 1, further comprising:

• receiving (722; 730) an Internet Protocol, IP, address from a second network node in association with establishment of the second PDU session on the second network slice; and

• assigning (724A; 732A) the IP address to the second PDU session.

3. The method of claim 2, further comprising:

• routing (736) PDUs at the UE (312) that would have been routed via the first PDU session on the first network slice via the second PDU session on the second network slice. 37

4. The method of any of claims 1 to 3, wherein the first network node is an Access and Mobility Management Function, AMF, (400), and the second network node is a Session Management Function, SMF, (408).

5. The method of any of claims 1 to 4, further comprising:

• informing (700), to the first network node, support of remapping the first network slice to the second network slice; and

• receiving (702), from the first network node, support of remapping the first network slice to the second network slice.

6. A method performed by an Access and Mobility Management Function, AMF (400), comprising:

• receiving (710) a Protocol Data Unit, PDU, session establishment request from a User Equipment, UE (312), to establish a second PDU session on a second network slice, wherein the PDU session establishment request comprises information that indicates that the PDU session is being established to remap a first PDU session of the UE (312) on a first network slice to the PDU session on the second network slice;

• selecting (712) a Session Management Function, SMF (408), for the PDU session on the second network slice based on the information comprised in the PDU session establishment request; and

• forwarding (718; 726) the PDU session establishment request to the selected SMF (408).

7. The method of claim 6, wherein selecting (712) the SMF (408) is such that the selected SMF (408) is the same SMF (408-X) that is used for the first PDU session on the first network slice.

8. The method of claim 6, wherein selecting (712) the SMF (408) is such that the selected SMF (408) is a new SMF (408-Y) that is not used for the existing PDU session on the first network slice.

9. The method of claim 8, wherein the SMF (408-Y) indicates (734), to Charging Function, CHF (via N40 interface), to Network Exposure Function, NEF, to Network Data Analytics Function, NWDAF, and to other Network Functions, NFs, that the PDU session is established for the purpose of remapping the first network slice to the second network slice.

10. The method of any of claims 6 to 9, further comprising:

• receiving (700), from the UE (312), support of remapping the first network slice to the second network slice; and

• informing (702), to the UE (312), support of remapping the first network slice to the second network slice.

11. The method of any of claims 6 to 10, wherein sending (738), to a Radio Access Network, RAN, (302), information on the PDU session established with the second network slice.

12. The method of any of claims 6 to 11, wherein the SMF (408-X; 408-Y) performs (720; 728) a selection of a User Plane Function, UPF (414-X; 415-Y).

13. The method of any of claims 6 to 12, wherein the SMF (408-X; 408-Y) accepts (724B; 732B) the second PDU session established with the second network slice and releases (724B; 732B) the first PDU session.

14. A method performed by a User Equipment, UE, (312), comprising: • receiving (804), from an Access and Mobility Management Function, AMF, (400), information that indicates that the AMF (400) does not support remapping of network slices, wherein: o remapping of network slices is a capability to remap a first Protocol Data Unit, PDU, session established on a first network slice (e.g., in a first registration area) to a second PDU session established on a second network slice (e.g., in a second registration area);

• deciding (806), based on local configuration or UE Route Selection Policy, URSP, whether to establish a new PDU session to remap an existing PDU session established on a first network slice to the new PDU session established on a second network slice.

15. The method of embodiment 14, further comprising:

• sending (800), to the AMF (400), information that indicates that the UE (312) supports the remapping of network slices.

16. A method performed by a User Equipment, UE (312), comprising:

• indicating (900), to an Access and Mobility Management Function, AMF (400), that the UE (312) supports remapping of network slices, wherein o remapping of network slices is a capability to remap a first Protocol Data Unit, PDU, session established on a first network slice (e.g., in a first registration area) to a second PDU session established on a second network slice (e.g., in a second registration area).

17. The method of claim 16, wherein a network policy is set (904) per network slice (of Serving Public Land Mobile Network, PLMN, or of Home Public Land Mobile Network, HPLMN) whether changing a network slice of PDU sessions for that network slice is enabled, the network policy is set (906) locally in the AMF (400).

18. The method of claim 16 or 17, wherein a network policy is set (904) per network slice (of Serving Public Land Mobile Network, PLMN, or of Home Public Land Mobile Network, HPLMN) whether changing a network slice of PDU sessions for that network slice is enabled, the network policy is enabled (908) by a Policy Control Function, PCF, (410).

19. The method of claim 16 or 17, wherein a network policy is set (904) per network slice (of Serving Public Land Mobile Network, PLMN, or of Home Public Land Mobile Network, HPLMN) whether changing a network slice of PDU sessions for that network slice is enabled, the network policy is enabled (910) by a Network Slice Selection Function, NSSF, (402) providing a list of network slices for Serving PLMN that each network slice of HPLMN can be changed to.

20. The method of claim 16 or 17, wherein a network policy is set (904) per network slice (of Serving Public Land Mobile Network, PLMN, or of Home Public Land Mobile Network, HPLMN) whether changing a network slice of PDU sessions for that network slice is enabled, the network policy is set (912A) by a Network Operation, Administration and Maintenance, OAM, at different fifth generation core network, 5GC, node.

21. The method of claim 16 or 17, wherein a network policy is set (904) per network slice (of Serving Public Land Mobile Network, PLMN, or of Home Public Land Mobile Network, HPLMN) whether changing a network slice of PDU sessions for that network slice is enabled, the network policy is set (912B) at a Radio Access Node, RAN, (302).

22. A method performed by an Access and Mobility Management Function, AMF (400), comprising:

• receiving (1000) a Protocol Data Unit, PDU, session establishment request to establish a PDU session on a first network slice;

• selecting (1002) a Session Management Function, SMF (408), in association with establishment of the PDU session on the first network slice; and

• forwarding (1004) the PDU session establishment request of the selected SMF (408). 41

23. The method of claim 22, further comprising:

• obtaining (1010) a Network Function, NF, profile of the SMF (408) that comprises information that indicates support of changing a network slice (unless enabled for whole PLMN) and support of the network slices that the PDU session can be changed between, i.e. the network slices of HPLMN that are part of the Subscribed network slices (for a SMF (408) of HPLMN), the network slices of Serving PLMN that as per Service Level Agreement, SLA, can be used for the network slice of the HPLMN; and

• selecting (1010) the SMF (408) based on the NF profile.

24. The method of claims 22 or 23, wherein the AMF (400) receives (1006), from the UE (312), indication that the UE supports remapping of network slices for the PDU session, and the remapping of network slices is a capability to remap a first Protocol Data Unit, PDU, session established on a first network slice (e.g., in a first registration area) to a second PDU session established on a second network slice (e.g., in a second registration area).

25. The method of any of claims 22 to 24, wherein the AMF (400) enables (1008) changing of a network slice of serving Public Land Mobile Network, PLMN, or a network slice of HPLMN.

26. The method of any of claims 22 to 25, wherein the AMF (400) provides (1014), to a Service Communication Proxy, SCP, (600), information that indicates that remapping of network slices is enabled for the PDU session.

27. The method of any of claims 22 to 26, wherein the AMF (400) provides (1014), to a Service Communication Proxy, SCP (600), information on a list of network slices of serving Public Land Mobile Network, PLMN, or HPLMN. 42

28. The method of claim 27, wherein the SCP uses (1016) the provided information and selects (1016) a Session Management Function, SMF, (408).

29. The method of any of claims 22 to 28, wherein the AMF (400) provides (1022), to the SMF (408), a network slice for which a PDU session can be changed to.

30. The method of any of claims 22 to 29, wherein the SMF (408) selects (1024) a Charging Function, CHF, that supports network slices for which a PDU session can be changed between.

31. The method of any of claims 22 to 30, wherein the SMF (408) indicates (1026), to the AMF (400), which network slices for which a PDU session can be changed between.

32. A method of performed by a fifth generation core network, 5GC, (310), comprising:

• providing (1032), to a Radio Access Node, RAN, (302), a list of network slices (of serving Public Land Mobile Network, PLMN, that a Protocol Data Unit, PDU, session can be remapped to (when activating a User Plane, UP, of the PDU session).

33. The method of claim 32, further comprising:

• sending (1034), to the RAN (302), a signal including a list of network slices that the PDU session can be remapped to, and an implicit indication or an explicit indication that the remapping may be applied by the RAN (302) at any point in time when the RAN (302) may decide remapping is beneficial.

34. The method of claim 32 or 33, wherein the RAN (302) decides (1036) to remap a Protocol Data Unit, PDU, session to a different network slice among the network slices provided by the 5GC (310) if dedicated resources for a given network slice have been exhausted. 43

35. The method of any of claim 32 to 34, wherein the 5GC (310) sends (1038), to the RAN (302), a signal only remapping network slices for which all core network, CN, functions serving the PDU session remain the same throughout the remapping process.

36. The method of claim 35, wherein the 5GC (310) explicitly indicates (1040), to the RAN (302), a list of the indicated network slice that can be autonomously chosen by the RAN (302) for slice remapping may comprise 5GC signaling to the RAN (302) a flag, together with the remapping network slice list, stating that "Remapping at RAN is allowed."

37. The method of claim 35, wherein the 5GC (310) implicitly indicates (1042), to the RAN (302), by signaling a list of remapping network slice that comprises a network slice that the RAN (302) can independently choose for remapping.

38. The method of any of claim 32 to 37, wherein the RAN (302) indicates (1044), to the 5GC (310), remapping of network slices for a PDU session to another network slice via new Information Elements, IES, in either a new procedure over a RAN-CN interface (a NG interface for the NG-RAN) or via an existing procedure.

39. The method of any of claim 32 to 38, wherein the RAN (302) indicates (1046), to the 5GC (310), during mobility by means of a NG path switch procedure.

40. A method performed by a Radio Access Node, RAN, (302), comprising:

• using (1100) a list of network slices as an input to decide whether to perform a NG handover, HO, or a XN HO.

41. The method of claim 40, wherein the RAN (302) triggers (1102A) the NG HO, and a fifth generation core network, 5GC, (310) performs (1104) remapping of network slice.

42. The method of claim 40, wherein

• the RAN (302) triggers (1102B) the XN HO,

44

• the 5GC (310) removes (1108) a network slice not supported at a target RAN from an allowed network slice as an outcome of a mobility registration update procedure, and

• a User Equipment, UE (312), decides (1110) whether to establish a PDU session based on User Equipment Route Selection Policy, URSP, or local policies. A method performed by a fifth generation core network, 5GC, 310, comprising:

• sending (1034), to a Radio Access Node, RAN, (302), a list of network slices that a Protocol Data Unit, PDU, session can be remapped to, wherein o an explicit indication (1040), to the RAN (302), that the list of indicated network slices that can be autonomously chosen by the RAN (302) for slice remapping may comprises 5GC signaling to RAN a flag, together with the remapping network slice list, stating that "Remapping at RAN is allowed," o the RAN (302) may decide (1036) to remap the PDU session to a different network slice among those network slices provided by the 5GC (310), o If the RAN (302) performs remapping of the network slice for a Protocol Data Unit, PDU, session to another network slice, the RAN (302) may indicate (1044) such remapping to the 5GC (310) via new Information Elements, IES, in either a new procedure over the RAN-CN interface (a NG interface for the RAN (302)) or via an existing procedure such as the NG PDU session modify procedure triggered by the RAN (302) towards the 5GC (310), and o the RAN (302) lets the 5GC (310) perform a slice remapping by triggering an NG Handover, HO. A method performed by a fifth generation core network, 5GC, 310, comprising:

• sending (1034), to a Radio Access Node, RAN, (302), a list of network slices that a Protocol Data Unit, PDU, session can be remapped to, wherein o an explicit indication (1040), to the RAN (302), that the list of indicated network slices that can be autonomously chosen by the RAN (302) for slice remapping may comprises 5GC signaling to RAN a flag, together with the remapping network slice list, stating that "Remapping at RAN is allowed." 45

45. A method performed by an Access and Mobility Management Function, AMF, (400) comprising:

• determining (1204) that one or more network slices (of Serving Public Land Mobile Network, PLMN) is not supported by a tracking area, TA; and

• determining (1206) that new network slices (of Serving PLMN) to be used for a Protocol Data Unit, PDU, session (which is supported by entities of PDU session).

46. The method of claim 45, wherein:

• the AMF (400) indicates (1208) the change of network slices to a Session Management Function, SMF, (408),

• the SMF (408) indicates (1210) the change to a User Plane Function, UPF, (414), and

• the SMF (408) indicates (1212) the change to a Network Function, NF.

47. The method of claim 46, wherein the NF comprises one or more of a Charging Function, CHF, (602) and a Policy Control Function, PCF, (410).

48. The method of claim 45, wherein a User Equipment, UE, (312) selects (1200) a new cell and sends a registration request to the AMF (400).

49. The method of any of claims 45 to 48, wherein the AMF (400) uses (1214) a new network slice in allowed network slices and send the new network slice to the UE (312).

50. The method of any of claims 45 to 49, wherein the UE (312) locally changes (1216A) network slice (of Serving PLMN) of PDU sessions based on changed allowed network slice because the UE (312) has received before list of network slice that can be remapped. 46

51. The method of any of claims 45 to 49, wherein the UE (312) receives (1216B), from the SMF (408), an explicit signaling of change of network slice for a PDU session.

52. The method of any of claims 46 to 51, wherein, for controlling a counting of number of registered UEs for a network slice as well as PDU sessions for a network slice, the NF performs (1222) actions for decreasing a count an old network slice and increasing the count for new network slice.

53. The method of any of claims 46 to 52, wherein the NF changes (1224) to another network slice that can replace an existing network slice.

54. The method of any of claims 46 to 53, wherein the NF determines (1226) that one or more network slices (of serving PLMN) of requested network slice is of lower priority in a new Tracking Area, TA, and that network slice change is enabled, the NF performs (1226) a network slice change as per steps above but changes to highest prioritized network slice of TA for the UE.