Initial registrations

Abstract

Systems and methods related to initial registrations of a User Equipment (UE) to core Network Functions (NFs) are disclosed. In one embodiment, a method performed by a Radio Access Network (RAN) node comprises receiving, from a UE, an initial registration request for registration with an Access and Mobility Management Function (AMF), selecting an AMF, and sending the initial registration request to the selected AMF. The method further comprises receiving an initial registration accept message and Non-Access Stratum (NAS) related information from the selected AMF. The initial registration accept message comprises a temporary AMF identifier (ID). The NAS related information comprises an AMF address and one or more addresses of one or more respective NFs selected for the UE. The method further comprises storing the addresses at the RAN node in association with the UE and transmitting the initial registration accept message to the UE.

Description

[0001] INITIAL REGISTRATIONS

[0002] TECHNICAL FIELD

[0003] The present disclosure relates to initial registrations for a distributed Non-Access Stratum (NAS) architecture for a core network of a wireless communications system.

[0004] BACKGROUND

[0005] Several external companies are promoting a new Non-Access Stratum (NAS) architecture in 3rdGeneration Partnership Project (3GPP) for evolved 5thGeneration Core (5GC). In this new NAS architecture, it is proposed that the Access and Mobility Management Function (AMF) as a NAS proxy be removed and NAS sublayer Network Functions (NFs) consuming NAS sublayers with the User Equipment (UE) in 5thGeneration (5G) to directly have contact with the UE using NAS. The proposals apply for the 6th Generation (6G) system (6GS), where the evolved 5GC is used.

[0006] A key concept promoted is distributed NAS which means NAS is between the UE and a specific core network NF via the Radio Access Network (RAN), meaning NAS to / from NFs other than the AMF will bypass the AMF. Each UE-NF pair has its own NAS connection e.g. each UE-AMF, UE-Session Management Function (SMF), UE-Policy Control Function (PCF), and UE-Short Message Service Function (SMSF) pair will have its own NAS connection. This is a new approach compared to the legacy approach which has a NAS proxy in the core network, which in 5G is the AMF.

[0007] The legacy approach is illustrated in Figure 1. As shown, all NAS transport passes through the AMF. More specifically, a NAS sublayer NF is an NF (e.g., SMF, PCF, and SMSF) with UE-NF communication and where the NAS communication is carried within the NAS Mobility Management (MM) layer(s), where the AMF is responsible for NAS-MM and as such the UE-NF communications pass through the AMF.

[0008] In contrast, Figures 2 and 3 illustrate examples of distributed NAS where the UE has separate NAS connections to multiple NFs in the core network. More specifically, Figure 2 illustrates a first proposed architecture to have the 6G NAS protocol between the UE and multiple NFs in the CN. As illustrated, the UE has distributed NAS connection terminations. The UE has a first NAS connection (NAS-a) to a first CN NF (NFa), a second NAS connection (NAS-b) to a second CN NF (NFb), a third NAS connection (NAS-c) to a third CN NF (NFc), a fourth NAS connection (NAS-x) to a fourth CN NF (NFx). Figure 3 illustrates another proposed architecture to have the 6G NAS protocol between the UE and multiple NFs in the CN. As illustrated, the UE has multiple NAS connections to respective CN NFs. Here, the NAS connections include a NAS-MM NAS connection between the UE and the AMF, a NAS-Session Management (SM) NAS connection between the UE and NF1, a UE policy NAS connection between the UE and NF2, and a Location Services (LCS) NAS connection between the UE and NF3. Each NAS connection of the UE has its own security context (key, integrity, and cryptographic algorithm), and these NAS connections having their own security contexts do not affect each other.

[0009] SUMMARYSystems and methods related to multiple initial registrations of a User Equipment (UE) to different Network Functions (NF) in a core network of a wireless communications system are disclosed. In one embodiment, a method performed by a Radio Access Network (RAN) node in a RAN of a wireless communications system that comprises the RAN and a core network comprises receiving, from a UE, an initial registration request for registration with an Access and Mobility Management Function (AMF) in the core network, selecting, at the RAN node, an AMF for the UE, and sending the initial registration request to the selected AMF. The method further comprises receiving an initial registration accept message and Non-Access Stratum (NAS) related information from the selected AMF. The initial registration accept message comprises a temporary AMF identifier (ID) that points to a certain AMF and is to be used by the UE for NAS signaling between the UE and the certain AMF, the certain AMF being either the selected AMF or some other AMF to which the selected AMF forwarded the initial registration request. The NAS related information comprises an address of the certain AMF and one or more additional addresses of one or more respective additional NFs selected by the certain AMF for the UE. The method further comprises storing the address of the certain AMF and the one or more additional addresses of the one or more respective additional NFs selected by the certain AMF for the UE at the RAN node in association with the UE. The method further comprises transmitting, to the UE, the initial registration accept message comprising the temporary AMF ID, in response to the initial registration request received from the UE. In this manner, the RAN node obtains and stores NF addresses during the initial registration of the UE with the AMF, where these stored NF addresses may be used by the RAN node during subsequent procedures.

[0010] In one embodiment, the initial registration accept message sent to the UE does not include the NAS related information comprising the address of the certain AMF and the one or more additional addresses of the one or more respective additional NFs.

[0011] In one embodiment, storing the address of the certain AMF and the one or more additional addresses of the one or more respective additional NFs selected by the AMF for the UE at the RAN node in association with the UE comprises storing the address of the certain AMF and the one or more additional addresses of the one or more respective additional NFs selected by the AMF for the UE at the RAN node in a RAN UE context of the UE stored by the RAN node.

[0012] In one embodiment, the one or more additional NFs selected by the AMF for which the one or more additional addresses are received and stored by the RAN node comprise any one or more of the following: a Policy and Control Function (PCF) address of a selected PCF, a Unified Data Management (UDM) address of a selected UDM, a Short Message Service Function (SMSF) address of a selected SMSF, an NF address of an NF that provides one or more policy related functions, and an NF address of an NF that stores UE subscription data.

[0013] In one embodiment, the initial registration request comprises a Subscriber Concealed Identity (SUCI) of the UE.

[0014] In one embodiment, the method further comprises receiving, from the UE, a second initial registration request for registration with a second NF in the core network, wherein the one or more additional NFs for which the RAN node received the one or more additional addresses from the certain AMF and stored the one or more additional addresses in association with the UE comprise a second NF. The method further comprises selecting, at the RAN node, the second NF for the UE based on the address of the second NF stored at the RAN node.In one embodiment, the method further comprises receiving from the UE a second initial registration request for registration with a second NF in the core network, receiving from the UE NF selection assistance information together with the second initial registration request, and selecting, at the RAN node, a second NF for the UE based on the NF selection assistance information received from the UE. In one embodiment, the NF selection assistance information received from the UE comprises any one or more of the following: a SUCI of the UE, a Data Network Name (DNN), and network slice information. In one embodiment, the method further comprises sending the second initial registration request to the second NF and receiving a second initial registration accept message and second NAS related information from the second NF in response to the second initial registration request sent to the second NF. The second initial registration accept message comprises a temporary NF ID that points to the second NF to be used by the UE for NAS signaling between the UE and the second NF and is associated to a UE context of the UE at the second NF. The second NAS related information comprises an NF address of the second NF. The method further comprises sending, to the UE, the second initial registration accept message comprising the temporary NF ID that points to the second NF, in response to the second initial registration accept message received from the UE. In one embodiment, the second initial registration accept message sent to the UE does not include the NF address of the second NF.

[0015] In one embodiment, the second NF is an SMF. In one embodiment, the method further comprises retrieving SMF selection subscription data for the UE, wherein selecting the second NF for the UE comprises selecting the SMF based on the NF selection assistance information received from the UE and the SMF selection subscription data, using local configuration or Network Repository Function (NRF) query. In one embodiment, the method further comprises selecting a UDM based on a SUCI of the UE received in or together with the second initial registration request, wherein retrieving the SMF selection subscription data for the UE comprises sending a request for the SMF selection subscription data to the selected UDM, the request comprising the SUCI of the UE, and receiving a response from the selected UDM, the response comprising the SMF selection subscription data of the UE. In one embodiment, the SMF selection subscription data of the UE comprises any one or more of the following data: a preferred network slice, DNN(s) requirements, one or more roaming policies, and one or more specific SMF capabilities needed for a service profile of the UE.

[0016] In one embodiment, the second NF is a Policy Control Function (PCF). In one embodiment, the one or more additional NFs for which the RAN node received the one or more additional addresses from the certain AMF and stored the one or more additional addresses in association with the UE comprise a selected PCF, and selecting the second NF for the UE comprises selecting the PCF based on the address of the selected PCF stored at the RAN node.

[0017] In another embodiment, the one or more additional NFs for which the RAN node received the one or more additional addresses from the certain AMF and stored the one or more additional addresses in association with the UE does not comprise a selected PCF, and the method further comprises retrieving PCF selection subscription data for the UE, wherein, if the PCF selection subscription data for the UE comprises a PCF address, selecting the second NF for the UE comprises selecting the PCF based on the PCF address comprised in the PCF selection subscription data for the UE. In one embodiment, the method further comprises selecting a UDM based on a SUCI of the UE received in or together with the second initial registration request, wherein retrieving the PCF selection subscription data for theUE comprises sending a request for the PCF selection subscription data to the selected UDM, the request comprising the SUCI of the UE, and receiving a response from the selected UDM, the response comprising the PCF selection subscription data of the UE. In one embodiment, if the PCF selection subscription data for the UE does not comprise a PCF address, selecting the second NF for the UE comprises selecting the PCF based on a Subscription Permanent Identity (SUPI) of the UE or other key, using a NRF query or local configuration.

[0018] Corresponding embodiments of a RAN node are also disclosed. In one embodiment, a RAN node for a RAN of a wireless communications system that comprises the RAN and a core network is adapted to receive, from a UE, an initial registration request for registration with an AMF in the core network, select, at the RAN node, an AMF for the UE, and send the initial registration request to the selected AMF. The RAN node is further adapted to receive an initial registration accept message and NAS related information from the selected AMF. The initial registration accept message comprises a temporary AMF ID that points to a certain AMF and is to be used by the UE for NAS signaling between the UE and the certain AMF, the certain AMF being either the selected AMF or some other AMF to which the selected AMF forwarded the initial registration request. The NAS related information comprises an address of the certain AMF and one or more additional addresses of one or more respective additional NFs selected by the certain AMF for the UE. The RAN node is further adapted to store the address of the certain AMF and the one or more additional addresses of the one or more respective additional NFs selected by the certain AMF for the UE at the RAN node in association with the UE and transmit, to the UE, the initial registration accept message comprising the temporary AMF ID, in response to the initial registration request received from the UE.

[0019] Embodiments of a method performed by an AMF are also disclosed. In one embodiment, a method performed by an AMF in a core network of a wireless communications system that comprises a RAN and the core network comprises receiving, from a RAN node, an initial registration request for registration of a UE with the AMF, selecting, at the AMF, one or more additional NFs, and sending an initial registration accept message and NAS related information to the RAN node. The initial registration accept message comprises a temporary AMF ID that points to the AMF and is to be used by the UE for NAS signaling between the UE and the AMF. The NAS related information comprises an address of the AMF and one or more additional addresses of the one or more respective additional NFs selected by the AMF for the UE.

[0020] In one embodiment, the address of the AMF and the one or more additional addresses of the one or more respective additional NFs selected by the AMF are for storage at the RAN node in association with the UE for subsequent use by the RAN node.

[0021] In one embodiment, the one or more additional NFs selected by the AMF comprise any one or more of the following: a PCF address of a selected PCF, a UDM address of a selected UDM, an SMSF address of a selected SMSF, an NF address of an NF that provides one or more policy related functions, and an NF address of an NF that stores UE subscription data.

[0022] In one embodiment, the initial registration request received from the RAN node comprises a SUCI of the UE. In one embodiment, the method further comprises obtaining a UE context of the UE from an old AMF that was previously selected for the UE, the UE context comprising an address of at least one of the one or more additionalNF, wherein selecting the one or more additional NFs comprises selecting the one or more additional NFs based on the UE context obtained from the old AMF.

[0023] In one embodiment, the method further comprises registering with a UDM for the UE such that the UDM stores an indication that initial registration of the UE with an AMF is completed. In one embodiment, the one or more NFs comprise a selected PCF, and registering the AMF with the UDM for the UE further comprises storing a PCF ID of the selected PCF in the UDM.

[0024] Corresponding embodiments of an AMF are also disclosed. In one embodiment, an AMF for a core network of a wireless communications system that comprises a RAN and the core network is adapted to receive, from a RAN node, an initial registration request for registration of a UE with the AMF, select, at the AMF, one or more additional NFs, and send an initial registration accept message and NAS related information to the RAN node. The initial registration accept message comprises a temporary AMF ID that points to the AMF and is to be used by the UE for NAS signaling between the UE and the AMF. The NAS related information comprises an address of the AMF and one or more additional addresses of the one or more respective additional NFs selected by the AMF for the UE.

[0025] Embodiments of a method performed by an NF are also disclosed. In one embodiment, a method performed by an NF in a core network of a wireless communications system that comprises a RAN and the core network comprises receiving, from a RAN node, an initial registration request for registration of a UE with the NF, retrieving an indication that indicates whether initial registration of the UE with an AMF is completed, and, responsive to the indication indicating the initial registration of the UE with an AMF is completed, sending an initial registration accept message to the RAN node.

[0026] In one embodiment, the initial registration request comprises a SUCI of the UE, and the method further comprises retrieving a SUPI of the UE based on the SUCI of the UE, wherein retrieving the indication that indicates whether initial registration of the UE with an AMF is completed comprise retrieving the indication that indicates whether initial registration of the UE with an AMF as part of a UE Context Management (UECM) registration in which the NF is registered for the UE.

[0027] In one embodiment, the method further comprises sending an address of the NF to the RAN node together with or in association with the initial registration accept message.

[0028] In one embodiment, the initial registration accept message comprises a temporary ID of the SMF to be used by the UE for NAS signaling between the UE and the SMF, wherein, at the SMF, the temporary ID is associated to a UE context of the UE stored at the SMF.

[0029] In one embodiment, the NF is an SMF or a PCF.

[0030] In one embodiment, the NF is an SMF, and the initial registration accept message comprises an address of the SMF and a Protocol Data Unit (PDU) session ID or other parameter that associates a certain PDU session of the UE with the address of the SMF.

[0031] Corresponding embodiments of an NF are also disclosed. In one embodiment, an NF for a core network of a wireless communications system that comprises a RAN and the core network is adapted to receive, from a RAN node, an initial registration request for registration of a UE with the NF, retrieve an indication that indicates whether initialregistration of the UE with an AMF is completed, and, responsive to the indication indicating the initial registration of the UE with an AMF is completed, send an initial registration accept message to the RAN node.

[0032] BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The accompanying drawing figures incorporated in and forming a part of this specification illustrate several aspects of the disclosure, and together with the description serve to explain the principles of the disclosure.

[0034] Figure 1 illustrates the legacy Non-Access Stratum (NAS) transport in a Third Generation Partnership Project (3GPP) 5thGeneration (5G) system.

[0035] Figures 2 and 3 illustrate proposed architectures for NAS transport in a 6thGeneration (6G) system where there are separate NAS signaling connections between a User Equipment (UE) and multiple Network Functions (NFs) in a core network of the 6G system.

[0036] Figure 4 illustrates one example of a wireless communications system in which embodiments of the present disclosure may be implemented.

[0037] Figure 5 illustrates one example of the wireless communications system of Figure 4.

[0038] Figure 6 illustrates the operation of the wireless communications system for initial registrations for distributed NAS, in accordance with embodiments of the present disclosure.

[0039] Figures 7 and 8 illustrate example embodiments of step 600 of Figure 6.

[0040] Figures 9A and 9B illustrate an example embodiment of step 602 of Figure 6.

[0041] Figures 10A, 10B, and 10C illustrate an example embodiment of step 604 of Figure 6.

[0042] Figures 11 and 12 illustrate example embodiments of a network node that may implement a Network Function (NF), in accordance with embodiments of the present disclosure.

[0043] Figure 13 illustrates an example embodiment of a UE.

[0044] DETAILED DESCRIPTION

[0045] The embodiments set forth below represent information to enable those skilled in the art to practice the embodiments and illustrate the best mode of practicing the embodiments. Upon reading the following description in light of the accompanying drawing figures, those skilled in the art will understand the concepts of the disclosure and will recognize applications of these concepts not particularly addressed herein. It should be understood that these concepts and applications fall within the scope of the disclosure.

[0046] Some of the embodiments contemplated herein will now be described more fully with reference to the accompanying drawings. Embodiments are provided by way of example to convey the scope of the subject matter to those skilled in the art.

[0047] Note that while 3rdGeneration Partnership Project (3GPP) 5thGeneration (5G) terminology is oftentimes used in the following description, it is to be understood that the solutions described herein are not limited thereto. Further, such 5G terminology is to be understood in a broad sense to cover analogous terminology used for other generations of the 3GPP system (e.g., 6thGeneration (6G). For example, the term "Access and Mobility Management Function” or "AMF” is to be understood to include any mobility management NF regardless of the actual name used for that NF(e.g., in 3GPP specifications), unless otherwise explicitly stated. Likewise, the term "Session Management Function” or "SMF” is to be understood to include any NF function that manages sessions regardless of the actual name used for that NF (e.g., in 3GPP specifications), unless otherwise explicitly stated. Likewise, the term "Policy Control Function” or "PCF” is to be understood to include any NF function performs the same or similar role regardless of the name used for that NF (e.g., in 3GPP specifications), unless otherwise explicitly stated.

[0048] There currently exist certain challenge(s). Distributed Non-Access Stratum (NAS) where separate NAS connections between a User Equipment (UE) and multiple Core Network (CN) Network Functions (NFs) is likely to be included in 6thGeneration (6G). Even if distributed NAS is not fully included in 6G, there may be NFs directly connected to UE using NAS. In context of 6G discussions, modular NAS and distributed NAS security on NAS connections are being discussed. Note that modular NAS is a proposal in which NFs are directly connected to the UE using NAS.

[0049] In this context, the following issues exist. A first issue is that, in the context of distributed NAS, it is not clear which logical entity selects each sublayer NF. This could be the Radio Access Network (RAN) and / or delegated to another NF e.g., AMF. A second issue that there is currently no solution for how information needed to perform NF producer discovery (e.g., subscriber identity, subscription data) is retrieved at the NF consumer. A third issue is that the impact between the UE and the RAN (i.e., on the Radio Resource Control (RRC) level), which is needed or distributed NAS to work, is not currently defined. The existing technology does not provide a solution for how information related to an already selected producer NF, which is not selected by RAN but where the information is needed in RAN for NF selection coordination (e.g., NF Identity (ID) or NF address), is obtained by the RAN. Yet another issue is that there is no solution for how long-lived UE identities (e.g., Subscription Permanent Identifier (SUPI)) could be prevented from existing in the RAN.

[0050] Certain aspects of the disclosure and their embodiments may provide solutions to these or other challenges. In accordance with embodiments of the present disclosure, a UE performs Initial Registration or Extended Initial Registration to multiple NFs in the core network that terminate NAS (e.g. AMF, SMF, and PCF). The RAN is subscription data aware. Upon reception of the Initial Registration Request message or Extended Initial Registration Request message from the UE, the RAN (i.e., the RAN node) performs NF selection based on selection assistance parameters provided by the UE on Radio Resource Control (RRC) and retrieved subscription data. In some embodiments, Subscriber Concealed Identity (SUCI) de-concealment is triggered either by the RAN or NAS terminating NF. In some embodiments, information related to already selected producer NF(s) is made available to the RAN in subscription data and / or stored in the RAN in a RAN UE context (e.g., during initial registration procedure for an initial NF (e.g., AMF) that performs initial selection of one or more other NFs, the addresses of the AMF and one or more other NFs such as, e.g., PCF, UDM, and / or Short Message Service Function (SMSF), are provide to the RAN and stored in the RAN UE context), for coordinated NF selection.

[0051] Embodiments of the present disclosure may include any one or more of the following aspects:

[0052] a) RRC parameters used by RAN for NF selection. NF selection in RAN for different types of NFs (e.g., SMF and PCF).

[0053] b) Subscription information used by RAN for NF selection.

[0054] c) New triggering points for SUCI to SUPI de-concealment (e.g., RAN, PCF).d) NAS UE context information (sometimes referred to herein by the exemplary name "RAN UE context information”) stored in RAN, where this NAS UE context information includes, e.g., addresses of one or more selected NFs.

[0055] e) Selected NF address registered in Unified Data Management (UDM) by AMF, e.g., in UE Context Management (UECM) Registration (e.g., AMF_MM registered). UDM provides information to other NFs about whether AMF is registered to authorize those initial registrations.

[0056] f) Selected NF address registered in UDM in UECM Registration (e.g., MM PCF ID) for additional use by RAN and other NFs.

[0057] g) RAN uses the UECM Registration and registers in UDM. Note that, in legacy 5thGeneration (5G) Core (5GC), the Network Exposure Function (NEF) uses the UDM to find the AMF which knows the UE's last known location (location exposure). The location is usually updated via existing NAS signaling meaning, if AMF is no longer involved in every NAS exchange, the RAN may be a substitute node from which to retrieve the last known location of the UE.

[0058] Certain embodiments may provide one or more of the following technical advantage(s). RAN can perform NF selection for initial registrations using SUCI and assistance information (e.g., RRC information received from the UE) and / or subscription data obtained from the core network (e.g., UDM and / or AMF). Initial registration procedures can be performed with different NFs.

[0059] Figure 4 illustrates one example of a wireless communications system 400 in which embodiments of the present disclosure may be implemented. In the embodiments described herein, the wireless communications system 400 is a 5G System (5GS) including a Next Generation RAN (NG-RAN) and a 5G Core (5GC) or a 6thGeneration (6G) system including a 6G Core (or 5GC) and a 6G RAN or any similar wireless communication system. In this example, the RAN includes RAN nodes 402-1 and 402-2, which may be base stations (e.g., a next generation NodeB (gNB) or 6thgeneration base station). While not explicitly shown in Figure 4, the RAN nodes 402-1 and 402-2 may be implemented using a Central Unit (CU) I Distributed Unit (DU) split architecture (e.g., a gNB may include a gNB-CU and one or more gNB-DUs). The RAN nodes 402-1 and 402-2 control corresponding cells 404-1 and 404-2. The RAN nodes 402-1 and 402-2 are generally referred to herein collectively as RAN nodes 402 and individually as RAN node 402. Likewise, the cells 404-1 and 404-2 are generally referred to herein collectively as cells 404 and individually as cell 404. The RAN nodes 402 are connected to a core network 406 (e.g., a 5GC or 6G Core). The core network 410 includes various types of Network Functions (NFs), as will be appreciated by those of ordinary skill in the art.

[0060] The RAN nodes 402 provide service to UEs 408-1 and 408-2 in the corresponding cells 404. The UEs 408-1 through 408-5 are generally referred to herein collectively as UEs 408 and individually as UE 408. Note that the term "UE”, as used herein, refers to any type of wireless communication device enabled to communicate with the RAN. While only two UEs 408 are shown in Figure 4, there may be many UEs 408 within each cell 404.

[0061] Figure 5 illustrates one example of the wireless communications system 400 of Figure 4. As illustrated, in this example, the core network 406 includes various NFs such as, e.g., an Access and Mobility Management Function (AMF) 500, Policy and Control Function (PCF) 502, Session Management Function (SMF) 504, Unified Data Management (UDM) 506, and a User Plane Function (UPF) 507. The core network 406 may include additional NFssuch as, e.g., a Network Slice Selection Function (NSSF) 508, a Network Exposure Function (NEF) 510, a Network Repository Function (NRF) 512, an Application Function (AF) 514, an Edge Application Server Discovery Function (EASDF) 516, an Network Slice-specific and Standalone Non-Public Network (SNPN) Authentication and Authorization Function (NSSAAF) 518, an Authentication Server Function (AUSF) 520, a Service Communication Proxy (SCP) 522, and / or an Network Slice Admission Control Function (NSACF) 524. The core network 406 may include additional or alternative NFs. Further, the core network 406 may include multiple instances of each of the NFs (e.g., multiple AMF instances, multiple SMF instances, multiple PCF instances, etc.).

[0062] Note that 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.

[0063] It should also be noted that the example of Figure 5 is only one example architecture and should not be construed as limiting the solution(s) described herein to any particular architecture. Further, while 5G terminology is used for the various NFs in the core network 406, this terminology (e.g., the NF names) is non-limiting. For instance, while the term "AMF” is used herein, this term refers to the 5G AMF or corresponding 6G NF. Likewise, the term "UE” as used herein refers to any type of wireless communications device enabled to access the wireless communications system 400 such as, for example, a 5G or 6G UE.

[0064] Figure 6 illustrates the operation of the wireless communications system 400 for initial registrations for distributed NAS, in accordance with embodiments of the present disclosure. As illustrated, the UE QQ018 initiates initial registrations to NFs with NAS access to the UE 408, which in the example of Figure 6 includes the AMF 500, the SMF 504, and the PCF 502. More specifically, the UE 408 first performs, in this example, an initial AMF registration procedure (600). In particular, the UE 408 transmits, to the RAN node 402, an initial registration request for an AMF (step 600-1). The initial registration request of step 600-1 may include a SUCI of the UE 408, e.g., both on RRC and NAS. The initial registration request of step 600-1 may additionally or alternatively include a Rout Indicator (Rl) of the UE 408 or a 6G-GUTI of the UE 408, which may be used in addition to the SUCI or as an alternative to the SUCI in the reminder of the procedure. Note that the Rl may be provided separately or as part of the SUCI.

[0065] The RAN node 402 performs AMF selection (step 600-2), which in this example results in the selection of the AMF 500 and sends the initial registration request to the AMF 500 (step 600-3). Note that the AMF selection may be performed by the RAN node 402 using any suitable AMF selection scheme such as, e.g., the conventional AMF selection scheme specified in the current version of the 3GPP specifications. The AMF 500 may perform security handling including, e.g., authentication and activation of NAS a security context (step 600-4) and sends, to the UE 408, an Initial Registration Accept (step 600-5). While it is not necessary for understanding the solution(s) described herein, for more information regarding the security handling of step 600-4, the interested reader is directed to, e.g., 3GPP TS 33.501, chapters 6.1.2 and 6.1.3 where the AMF includes the Security Anchor Function (SEAF). As discussed below, the Initial Registration Accept of step 600-5 is provided with NAS related information, at least some of which is to be stored by the RAN node 402. More specifically, this NAS related information includes one or more NF addresses (e.g., the address of the AMF 500, an address of a PCF (e.g., the PCF 502) selected by the AMF 500 for AM policy and UE policy, and / or other NF addresses) to be stored by the RAN node 402, as discussed below. The Initial RegistrationAccept may include an AMF-Globally Unique Temporary Identifier (GUTI) of the AMF 500 to be used by the UE 408 for NAS signaling with the AMF 500. Note that the Initial Registration Accept is a NAS message that targets the UE 408. The NAS related information is sent in association with or together with the Initial Registration Accept and targets the RAN node 402.

[0066] The RAN node 402 sends the Initial Registration Accept (including the AMF-GUTI) to the UE 408 (step WT400-6). Note that in this example the AMF address included in the Initial Registration Accept is the address of the selected AMF 500 and the AMF-GUTI points to the selected AMF 500; however, in the case of AMF re-allocation where the selected AMF 500 forwards the Initial Registration Request to another AMF, e.g., as part of an AMF re-allocation procedure, the AMF address included in the Initial Registration Access alternatively includes the AMF address of this other AMF and the AMF-GUTI is that of this other AMF. The UE 408 may respond to the AMF 500 (e.g., using the AMF-GUTI) with an Initial Registration Complete (step 600-7).

[0067] The UE 408 also performs one or more additional initial registrations for one or more additional NFs (steps 602 and 604). More specifically, in step 602, the UE 408 transmits, to the RAN node 402, an initial registration request (also referred to herein as an "extended initial registration request”) for an SMF (step 602-1). The initial registration request of step 602-1 may include the SUCI of the UE 408 or an SMF-GUTI of the UE 408 (which may have been assigned by a previous procedure), both on RRC and NAS. Note that the initial registration request of step 602-1 may be an extended version of an existing message or a new message. The RAN node 402 performs SMF selection (step 602-2), which in this example results in the selection of the SMF 504, and sends the initial registration request to the SMF 504 (step 602-3). Note that the SMF selection may be performed by the RAN node 402 using any suitable SMF selection scheme such as, e.g., the conventional SMF selection scheme specified in the current version of the 3GPP specifications. As discussed below, the SMF selection of step 602-2 is based on assistance information received from the UE 408 (e.g., via RRC) (e.g., Data Network Name (DNN) and network slice information (e.g., Single Network Slice Selection Assistance Information (S-NSSAI)) and subscription data (i.e., SMF selection subscription data), e.g., using NRF query or local configuration.

[0068] The SMF 504 may perform security handling including, e.g., authentication and activation of a NAS security context (step 602-4) and sends, to the UE 408, an Initial Registration Accept (step 602-5). While it is not necessary for understanding the solution(s) described herein, the security handling of step 602-4 may be similar to that described in 3GPP TS 33.501, chapters 6.1.2 and 6.1.3 but where the SMF 504 includes the SEAF. As discussed below, the Extended Initial Registration Accept is provided together with or otherwise in association with NAS related information, at least some of which is to be stored by the RAN node 402. More specifically, this NAS related information includes one or more NF addresses (e.g., the address of the SMF 504), as discussed below. The Extended Initial Registration Accept may include an SMF-GUTI of the SMF 504 to be used by the UE 408 for NAS signaling with the SMF 504. Note that the Extended Initial Registration Accept is a NAS message that targets the UE 408. The NAS related information is sent in association with or together with the Extended Initial Registration Accept and targets the RAN node 402.The RAN node 402 sends the Extended Initial Registration Accept (including the SMF-GUTI) to the UE 408 (step WT400-6). The UE 408 optionally responds with a (extended) registration complete message (step 602-7). The messages of steps 602-5, 602-6, and 602-7 may be extended versions of existing messages or new messages.

[0069] In the illustrated example, the UE 408 performs an initial registration for a PCF (step 604). More specifically, the UE 408 transmits, to the RAN node 402, an extended initial registration request for a PCF (step 604-1). The extended initial registration request of step 604-1 may include the SUCI of the UE 408 or a PCF-GUTI of the UE 408 (which may have been assigned by a previous procedure), both on RRC and NAS. Note that the initial registration request of step 604-1 may be an extended version of an existing message or a new message. The RAN node 402 performs PCF selection (step 604-2), which in this example results in the selection of the PCF 502 and sends the extended initial registration request to the PCF 502 (step 604-3). Note that the PCF selection may be performed by the RAN node 402 using any suitable PCF selection scheme such as, e.g., the conventional PCF selection scheme specified in the current version of the 3GPP specifications. Details regarding the PCF selection of step 604-2 are provided below (see, e.g., Figures 10A and 10B).

[0070] The PCF 502 may perform security handling including, e.g., authentication and activation of a NAS security context (step 604-4) and sends, to the UE 408, an Initial Registration Accept (step 604-5). While not necessary for understanding the solution(s) described herein, the security handling of step 6024-4 may be similar to that described in 3GPP TS 33.501 (see, e.g., V18.8.0 or V19.1.0), chapters 6.1.2 and 6.1.3 but where the PCF 502 includes the SEAF. As discussed below, the Extended Initial Registration Accept is provided together with or otherwise in association with NAS related information, at least some of which is to be stored by the RAN node 402. More specifically, this NAS related information includes one or more NF addresses (e.g., the address of the PCF 502), as discussed below. The Extended Initial Registration Accept may include a PCF-GUTI of the PCF 502 to be used by the UE 408 for NAS signaling with the PCF 502. Note that the Extended Initial Registration Accept is a NAS message that targets the UE 408. The NAS related information is sent in association with or together with the Extended Initial Registration Accept and targets the RAN node 402.

[0071] The RAN node 402 sends the Extended Initial Registration Accept (including the PCF-GUTI) to the UE 408 (step WT404-6). The UE 408 optionally responds with a (extended) registration complete message (step 604-7). The messages of steps 604-5, 604-6, and 604-7 may be extended versions of existing messages or new messages.

[0072] Figure 7 illustrates one example embodiment of step 600 of Figure 6. As illustrated, the UE 408 transmits an Initial Registration Request to the RAN node 402 (step 700). Step 700 corresponds to step 600-1 of Figure 6. In the illustrated example, the Initial Registration Request includes a SUCI of the UE 408, e.g., both on RRC and NAS. The Initial Registration Request of step 700 may additionally or alternatively include an Rl of the UE 408 or a 6G-GUTI of the UE 408, which may be used in addition to the SUCI or as an alternative to the SUCI in the reminder of the procedure. Note that the Rl may be provided separately or as part of the SUCI. The RAN node 402 performs AMF selection (step 702), which in this example results in the selection of the AMF 500 and sends the initial registration request to the AMF 500 (step 704). Steps 702 and 704 correspond to steps 600-2 and 600-3 of Figure 6. Note that the AMF selection may be performed by the RAN node 402 using any suitable AMF selection scheme such as, e.g., the conventionalAMF selection scheme specified in the current version of the 3GPP specifications. For example, the AMF selection may be performed by round robin (e.g., evenly distributed over multiple AMF pools).

[0073] If there is an existing UE context for the UE 408, the AMF 500 obtains the UE context of the UE 408 from an old, or prior, AMF 705 of the UE 408 or from the same AMF 500 (e.g., from local storage at the AMF 500). In this example, the AMF 500 optionally sends a UE context transfer request to the old or prior AMF 705 of the UE 408 (step 706) and, in response, receives a UE context transfer response including a UE context of the UE 408 (step 708). The UE context may include an address of at least one of the one or more additional NFs (e.g., PCF address, UDM address, SMSF address, and / or the like). Note that, while not explicitly shown in Figure 7, the security handling of step 600-4 of Figure 6 may be performed after step 708, for example.

[0074] The AMF 500 performs UDM and optionally SMSF selection, e.g., as defined in the current 3GPP specifications (step 710). The details of the UDM and SMSF selection are not necessary for understanding the solution(s) described herein; however, for more information regarding UDM and SMSF selection, the interested reader is directed to 3GPP TS 23.501 (see, e.g., V18.8.0 or V19.2.0), Chapters 6.3.8 and 6.3.10. Note that if the UE context retrieved in steps 706 and 708 includes a UDM address, the UDM selection of step 710 may select the UDM based on the UDM address included in the UE context (i.e., select the UDM that corresponds to the UDM address included in the UE context). Likewise, if the UE context retrieved in steps 706 and 708 includes an SMSF address, the SMSF selection of step 710 may select the SMSF based on the SMSF address included in the UE context (i.e., select the SMFS that corresponds to the SMSF address included in the UE context).

[0075] The AMF 500 performs PCF selection for Access and Mobility (AM) policy and UE policy based on local configuration or via NRF query (step 712). Note that if the UE context retrieved in steps 706 and 708 includes a PCF address, the PCF selection of step 712 may select the PCF based on the PCF address included in the UE context (i.e., select the PCF that corresponds to the PCF address included in the UE context). Otherwise, the AMF 500 may perform the PCF selection, e.g., as defined in 3GPP TS 23.501, Chapter 6.3.7.1. The PCF selection may be based on various information such as, e.g., the SUPI of the UE 408, S-NSSAI(s), PCF Set ID, PCF Group ID, DNN replacement capability of the PCF, slice replacement capability of the PCF, PCF Selection Assistance Information and PCF ID(s) serving the established PDU sessions received from the UDM, URSP delivery in Evolved Packet System (EPS) capability of the PCF; however, the PCF selection is not limited thereto. The address of the selected PCF, which is the PCF 502 in this example, is stored in the AMF 500.

[0076] The AMF 500 communicates with the PCF 502 to perform AM Policy Association Establishment (step 714). The AMF 500 also communicates with the UDM 506 (i.e., the UDM selected in step 710) to perform UECM registration (step 716). As part of the UECM registration, the AMF 500 registers AM Mobility Management (MM) to the UDM 506. The registration of AM MM is or includes an indication that the AMF 500 is registered for the UE 408. This indication may be used to authorize extended registration(s) for other NF(s), as described below.

[0077] Note that, in one additional embodiment, the UECM registration of step 714 may further include a RAN ID of the RAN node 402, in which case the RAN node 402 may have previously provided its RAN ID to the AMF 500, e.g., in or in association with the Initial Registration Request of step 704. Alternatively, the RAN node 402 may register withthe UDM 506 sometime after receiving the Initial Registration Accept in step 718 (see below). In this alternative, the RAN node 402 registers with the UDM 506 for the UE 408 after step 718.

[0078] The AMF 500 sends, to the RAN node 402, an Initial Registration Accept (step 718). Step 718 corresponds to step 600-5 of Figure 6. The Initial Registration Accept is provided tougher with or otherwise in association with NAS related information, at least some of which is to be stored by the RAN node 402. More specifically, this NAS related information includes one or more NF addresses to be stored by the RAN node 402, which in the illustrated example include the PCF address (i.e., the address of the PCF 502 selected in step 712), the UDM address (i.e., the address of the UDM 506 selected in step 710), the AMF address (i.e., the address of the AMF 500 which is the AMF selected in step 702), and the SMSF address (i.e., the address of the SMSF selected in step 710). The Initial Registration Accept includes, in this example, a temporary ID assigned to the AMF 500, which in the illustrated example is an AMF-GUTI associated to the AMF 500. This temporary ID associated to the AMF 500 is to be used by the UE 408 for NAS signaling with the AMF 500. The temporary ID is created or derived by the AMF 500 in this example. Again, note that the Initial Registration Accept is a NAS message that targets the UE 408. The NAS related information is sent in association with or together with the Initial Registration Accept and targets the RAN node 402.

[0079] The RAN node 402 stores the NAS related information (i.e., the NF addresses) at the RAN node 402 in association with the UE 408, e.g., in a RAN UE context of the UE 408 stored by the RAN node 402 (step 720). The RAN node 402 sends the Initial Registration Accept (including the AMF-GUTI) to the UE 408 (step 722). Step 722 corresponds to step WT400-6 of Figure 6. The UE 408 may respond to the AMF 500 (e.g., using the AMF-GUTI) with an Initial Registration Complete (step 724), which corresponds to step 600-7 of Figure 6.

[0080] Figure 8 illustrates another example embodiment of step 600 of Figure 6. This embodiment is similar to that of Figure 7, but where instead of the AMF 500 providing the address of the AMF 500 to the RAN node 402 in the Registration Accept of step 720, the AMF 500 stores an ID of the PCF 502 (referred to by the exemplary name of MM PCF ID) in the UDM 506 in a modified step 718, which is denoted in Figure 8 as step 718'. Then, in a modified step 720, which is denoted as step 720', the AMF 500 sends, to the RAN node 402, the Registration Accept and the NF addresses other than that of the PCF 502. In modified step 722, which is denoted as step 722', the RAN node 402 stores the received NF addresses in the RAN UE context. Otherwise, the procedure of Figure 8 is the same as that of Figure 7.

[0081] Figures 9A and 9B illustrate one example embodiment of step 602 of Figure 6 in which the UE 408 performs an extended initial registration for an SMF. In this example, a pre-condition for the extended initial registration for an SMF is that Initial Registration with the AMF 500 has been completed (e.g., the process of Figure 7 or Figure 8 has been completed). As illustrated, the UE 408 transmits an Extended Initial Registration Request to the RAN node 402 (step 900). Step 900 corresponds to step 602-1 of Figure 6. In this example, the Extended Initial Registration Request includes the SUCI of the UE 408 at the NAS level. In addition, at the RRC level, the Extended Initial Registration Request further includes SMF selection assistance information including the SUCI of the UE 408, the DNN, network slice information (e.g., S-NSSAI), and an SMF registration indication (i.e., an indication that the extended initial registration request is a request for initial registration with an SMF).The RAN node 402 then performs SMF selection based on the SMF selection assistance information including the SUCI of the UE 408 (step 902). Step 902 corresponds to step 602-2 of Figure 6. More specifically, in this example, the RAN node 402 performs UDM selection based on a Public Land Mobile Network (PLMN) Identifier (ID) and Routing Indicator (Rl) as received in the SUCI of the UE 408, using NRF query or local configuration (step 902-1). The RAN node 402 retrieves subscription data for the UE 408 from the selected UDM, which is the UDM 506 in this example. In particular, the RAN node 402 sends, to the UDM 506, a Subscriber Data Management (SDM) Get Request including the SUCI of the UE 408 to request SMF selection subscription data for the UE 408 and UE context information in SMF subscription data (step 902-2). The UDM 506 invokes a Subscription Identifier Deconcealing Function (SIDF) for deconcealment of the SUCI of the UE 408 to a corresponding SUPI of the UE 408 and retrieves the SMF selection subscription data and the SMF subscription data (including the UE context in the SMF subscription data) for the UE 408 based on the SUPI of the UE 408 (step 902-3). The SMF selection subscription data includes a set of parameters that affect the selection of an SMF for the UE's session. The SMF selection subscription data may include, for example, a preferred network slice, DNN(s) requirements, roaming policies, and potentially one or more specific SMF capabilities needed for a service profile of the UE 408. The UE context in the SMF subscription data includes, for example, data related to already registered PDU session(s) of the UE 408. The UDM 506 then sends an SDM Get Response to the RAN node 402, where this response includes the SMF selection subscription data and the UE context in the SMF subscription data (step 902-4). The RAN node 402 then performs SMF selection for the UE 408 based on the received SMF selection subscription data received from the UDM 506 and the SMF selection assistance information (e.g., DNN, network slice information) received from the UE 408, using, e.g., NRF query or local configuration (step 902-5).

[0082] The RAN node 402 sends the Extended Initial Registration Request to the selected SMF, which in this example is the SMF 504 (step 904). In the illustrated example, the Extended Registration Request includes the SUCI of the UE 408. Note, however, that in an alternative embodiment, the SUPI of the UE 408 may be obtained by the RAN node 402 (e.g., from the UDM 506, e.g., in step 902-4), in which case the Extended Initial Registration Request sent from the RAN node 402 to the SMF 504 may include the SUPI of the UE 408. Note that, while not explicitly shown in Figure 9A, the security handling of step 602-4 of Figure 6 may be performed after step 904, for example.

[0083] If the Extended Initial Registration Request includes the SUCI of the UE 408, the SMF 504 sends, to the UDM 506, an SDM Get Request including the SUCI of the UE 408 (step 906). In response, the UDM 506 invokes an SIDF for deconcealment of the SUCI (step 908) and sends an SDM Get Response to the SMF 504 including the SUPI of the UE 408 (step 910).

[0084] The SMF 504 communications with the UDM 506 to perform UECM registration (step 912). In other words, the SMF 504 registers with the UDM 506 for the UE 408. As part of the UECM registration, the SMF 504 receives, from the UDM 506), a UECM Registration Response including an indication that registration of the UE 408 with an AMF (i.e., the AMF 500 in this example) is completed (step 914). This indication is referred to herein as "AMF_MM registration = True”. If "AMF_MM registration” is "False”, the SMF 504 may not authorize an Extended Initial Registration Accept. However, in the illustrated example, AMF_MM registration = True and, as such, the SMF 504 authorizes an Extended Initial Registration Accept.The SMF 504 sends, to the RAN node 402, an Extended Initial Registration Accept to the RAN node 402 (step 916). Step 916 corresponds to step 602-5 of Figure 6. The Extended Initial Registration Accept is provided tougher with or otherwise in association with NAS related information, at least some of which is to be stored by the RAN node 402. More specifically, this NAS related information includes the SMF address (i.e., the address of the selected SMF 504). In the case of the SMF 504, the Extended Initial Registration Accept may include a PDU session ID of a corresponding PDU session of the UE 408 or some other identifier or parameter that associates the SMF address to the PDU session. The PDU session ID or other identifier or parameter that associates the SMF address to the PDU session may be beneficial for the RAN node 402 to select the proper SMF in the case there are multiple PDU sessions having corresponding SMFs. Note that the PDU session ID or other identifier or parameter may be included both in the Extended Initial Registration Accept (which targets the UE 408) and in the NAS related information (or other information) that targets the RAN node 402. The Extended Initial Registration Accept also includes, in this example, a UE temporary ID (referred to herein as an "SMF-GUTI”) associated to the SMF 504, which is to be used by the UE 408 for NAS signaling with the SMF 504. The SMF-GUTI points to the SMF 504 having the UE context for the UE 408. The SMF-GUTI is created or derived by the SMF 504 in this example. Again, note that the Extended Initial Registration Accept is a NAS message that targets the UE 408. The NAS related information is sent in association with or together with the Extended Initial Registration Accept and targets the RAN node 402.

[0085] The RAN node 402 stores the NAS related information (i.e., the SMF address in this example) at the RAN node 402 in association with the UE 408, e.g., in the RAN UE context of the UE 408 stored by the RAN node 402 (step 918). The RAN node 402 sends the Extended Initial Registration Accept (including the SMF-GUTI) to the UE 408 (step 920). Step 922 corresponds to step WT402-6 of Figure 6. The UE 408 may respond to the SMF 504 (e.g., using the SMF-GUTI) with an Initial Registration Complete (step 922), which corresponds to step 602-7 of Figure 6.

[0086] Note that the Extended Initial Registration may be analogous to Initial Registration as used for the AMF 500 and UE 408 or a Protocol Data Unit (PDU) Session Establishment Request with additional parameters as shown in Figures 9A and 9B. If a PDU Session Establishment Request is used, a PDU Session Establishment Request replaces Extended Initial Registration Request, a PDU Session Establishment Accept replaces Extended Initial Registration Accept, and a PDU Session Establishment Complete replaces Extended Initial Registration Complete.

[0087] Figures 10A through 10C illustrate one example embodiment of step 604 of Figure 6 in which the UE 408 performs an extended initial registration for a PCF. In this example, a pre-condition for the extended initial registration for a PCF is that Initial Registration with the AMF 500 has been completed (e.g., the process of Figure 7 or Figure 8 has been completed). As illustrated, optionally, the PCF address for a PCF (e.g., PCF 502) previously selected for AM policy (e.g., during Initial Registration with the AMF 500 using, e.g., the procedure of Figure 7 or Figure 8) may be stored at the RAN node 402. In addition, an allowed S-NSSAI(s) may have been previously obtained by the RAN node 402 (e.g., from the AMF 500 during Initial Registration of the UE 408 with the AMF 500) and stored by the RAN node 402.

[0088] The UE 408 transmits an Extended Initial Registration Request to the RAN node 402 (step 1002). Step 1002 corresponds to step 604-1 of Figure 6. In this example, the Extended Initial Registration Request includes the SUCI of the UE 408 at the NAS level. In addition, at the RRC level, the Extended Initial Registration Request further includesPCF selection assistance information including the SUCI of the UE 408, network slice information (e.g., S-NSSAI), and a PCF registration indication (i.e., an indication that the extended initial registration request is a request for initial registration with a PCF).

[0089] If a PCF address for a PCF (i.e., the PCF 502 in this example) for AM policy is stored in the RAN node 402, the RAN node 402 performs PCF selection using the stored PCF address (step 1004).

[0090] If no PCF address is stored in the RAN node 402, the RAN node 402 determines whether a PCF address for a PCF (e.g., the PCF 502 in this example) for AM policy for the UE 408 is stored in the UDM 506, e.g., in AM / UE PCF selection subscription data (step 1006). More specifically, in this example, the RAN node 402 performs UDM selection based on a PLMN ID and Rl as received in the SUCI of the UE 408, using NRF query or local configuration (step 1006-1). The RAN node 402 then retrieves the AM / UE PCF selection subscription data from the selected UDM, which is the UDM 506 in this example. Specifically, the RAN node 402 sends, to the UDM 506, an SDM Get Request for the AM / UE PCF selection subscription data, where the SDM Get Request includes the SUCI of the UE 408 (step 1006-2). In response, the UDM 506 invokes an SIDF for deconcealment of the SUCI of the UE 408 to a corresponding SUPI of the UE 408 and retrieves the AM / UE PCF selection subscription data based on the SUPI of the UE 408 (step 1006-3). The AM / UE PCF selection subscription data includes a set of parameters that affect the selection of a PCF for the UE's session, e.g., if no PCF address is stored in the RAN node Q402. The AM / UE PCF selection subscription data may include, for example, any one or more of the following: a PCF address, the SUPI of the UE 408 or a new key identifying the UE 408 in the UDM 506, which may be used by the RAN node 402 to perform an NRF query for PCF selection. The UDM 506 then sends an SDM Get Response to the RAN node 402, where this response includes the AM / UE PCF selection subscription data (step 1006-4). If the AM / UE PCF selection subscription data includes the PCF address, the RAN node 402 then perform PCF selection for the UE 408 based on the received PCF address (step 1006-5).

[0091] Otherwise, if no PCF address is stored in the RAN node 402 and no PCF address is included in the AM / UE PCF selection subscription data, the RAN node 402 retrieves the SUPI of the UE 408 or some other key for NRF query (step 1008). More specifically, the RAN node 402 performs UDM selection based on the PLMN ID and Rl as received in the SUCI of the UE 408, using NRF query or local configuration (step 1008-1). The RAN node 402 retrieves the SUPI of the UE 408 or other key for NRF query from the UDM 506. Specifically, in this example, the RAN node 402 sends an SDM Get Request including the SUCI of the UE 408 to the UDM 506 (step 1008-2). The SDM Get Request may also include PCF selection data, which may be an indicator that indicates that the SDM Get Request is to get the SUPI of the UE 408 for the purpose of PCF selection. In response, the UDM 506 invokes an SIDF for SUCI deconcealment and, optionally, retrieves a key for NRF query based on the resulting SUPI of the UE 408 (step 1008-3). The UDM 506 then sends an SDM Get Response to the RAN node 402, where the SDM Get Response includes either the SUPI of the UE 408 or the retrieved key for NRF query (step 1008-4). Note that procedures for requesting AM / UE PCF Selection Subscription Data (e.g., steps 1006-1 through 1006-4) and requesting parameters for NRF query (e.g., steps 1008-1 through 1008-4) can be combined into one UDM selection and one UDM request. The RAN node 402 then performs PCF selection (for UE policy) using NRF query or local configuration, based on the SUPI of the UE 408 or retrieved key (e.g. by use of legacy or similar PCF Selection Subscription Data) (step 1008-5). The RAN node 402 controls the PCF selectin such that the network slice is within the set of Allowed S-NSSAIs for the UE 408.Once PCF selection has been performed, the RAN node 402 sends the Extended Initial Registration Request to the selected PCF, which in this example is the PCF 502 (step 1010). In the illustrated example, the Extended Registration Request includes the SUCI of the UE 408. Note, however, that in an alternative embodiment, the SUPI of the UE 408 may be obtained by the RAN node 402 (e.g., from the UDM 506, e.g., in step 1008-4), in which case the Extended Initial Registration Request sent from the RAN node 402 to the PCF 502 may include the SUPI of the UE 408. Note that, while not explicitly shown in Figure 10, the security handling of step 604-4 of Figure 6 may be performed after step 1010, for example.

[0092] The PCF 502 performs UDM selection based on either the PLMN ID and Rl as received in the SUCI or the SUPI of the UE 408, using NRF query or local configuration (step 1012). If the Extended Initial Registration Request includes the SUCI of the UE 408 (but not the SUPI of the UE 408), the PCF 502 sends, to the selected UDM 506, an SDM Get Request including the SUCI of the UE 408 (step 1014). In response, the UDM 506 invokes an SIDF for deconcealment of the SUCI (step 1016) and sends an SDM Get Response to the PCF 502 including the SUPI of the UE 408 (step 1016).

[0093] The PCF 502 communicates with the UDM 506 to perform UECM registration (step 1018). In other words, the PCF 502 registers with the UDM 506 for the UE 408. As part of the UECM registration, the PCF 502 receives, from the UDM 506), a UECM Registration Response including an indication that registration of the UE 408 with an AMF (i.e., the AMF 500 in this example) is completed (step 1020). This indication is referred to herein as "AMF_MM registration = True”. If "AMF_MM registration” is "False”, the PCF 502 may not authorize an Extended Initial Registration Accept. However, in the illustrated example, AMF_MM registration = True and, as such, the PCF 502 authorizes an Extended Initial Registration Accept.

[0094] The PCF 502 sends, to the RAN node 402, an Extended Initial Registration Accept to the RAN node 402 (step 1022). Step 1022 corresponds to step 604-5 of Figure 6. The Extended Initial Registration Accept is provided together with or otherwise in association with NAS related information, at least some of which is to be stored by the RAN node 402. More specifically, this NAS related information includes the PCF address (i.e., the address of the selected PCF 502). The Extended Initial Registration Accept includes, in this example, a UE temporary ID (referred to herein as an "PCF-GUTI”) associated to the PCF 502, which is to be used by the UE 408 for NAS signaling with the PCF 502. The PCF-GUTI points to the PCF 502 having the UE context for the UE 408. The PCF-GUTI is created or derived by the PCF 502 in this example. Note that the Extended Initial Registration Accept is a NAS message that targets the UE 408. The NAS related information is sent in association with or together with the Extended Initial Registration Accept and targets the RAN node 402.

[0095] The RAN node 402 stores the NAS related information (i.e., the PCF address in this example) at the RAN node 402 in association with the UE 408, e.g., in the RAN UE context of the UE 408 stored by the RAN node 402 (step 1024). The RAN node 402 sends the Extended Initial Registration Accept (including the PCF-GUTI) to the UE 408 (step 1026). Step 1026 corresponds to step WT404-6 of Figure 6. The UE 408 may respond to the PCF 502 (e.g., using the PCF-GUTI) with an Extended Initial Registration Complete (step 1028), which corresponds to step 604-7 of Figure 6.Note that the Extended Initial Registration may be analogous to Initial Registration as used for the AMF 500 and UE 408 or a PDU Session Establishment Request with additional parameters as shown in Figures 10A through 103. If a PDU Session Establishment Request is used, a PDU Session Establishment Request replaces Extended Initial Registration Request, a PDU Session Establishment Accept replaces Extended Initial Registration Accept, and a PDU Session Establishment Complete replaces Extended Initial Registration Complete.

[0096] Figure 11 is a schematic block diagram of a network node 1100 according to some embodiments of the present disclosure. Optional features are represented by dashed boxes. The network node 1100 may be, for example, a RAN node 402 or a network node that implements all or part of the functionality of a NF (e.g., AMF 500, SMF 504, or PCF 502) as described herein. As illustrated, the network node 1100 includes a control system 1102 that includes one or more processors 1104 (e.g., Central Processing Units (CPUs), Application Specific Integrated Circuits (ASICs), Field Programmable Gate Arrays (FPGAs), and / or the like), memory 1106, and a network interface 1108. The one or more processors 1104 are also referred to herein as processing circuitry. In addition, if the network node 1100 is a RAN node (e.g., the RAN node 402 or a network node that implements part of the functionality of the RAN node 402 such as, e.g., a DU of the RAN node 402), the network node 1100 may include one or more radio units 1110 that each includes one or more transmitters 1112 and one or more receivers 1114 coupled to one or more antennas 1116. The radio units 1110 may be referred to or be part of radio interface circuitry. In some embodiments, the radio unit(s) 1110 is external to the control system 1102 and connected to the control system 1102 via, e.g., a wired connection (e.g., an optical cable). However, in some other embodiments, the radio unit(s) 1110 and potentially the antenna(s) 1116 are integrated together with the control system 1102. The one or more processors 1104 operate to provide one or more functions of the network node 1100 as described herein (e.g., one or more functions of the RAN node 402 or one or more functions of an NF such as the AMF 500, PCF 502, or SMF 504, as described herein). In some embodiments, the function(s) are implemented in software that is stored, e.g., in the memory 1106 and executed by the one or more processors 1104.

[0097] Figure 12 is a schematic block diagram that illustrates a virtualized embodiment of the network node 1100 according to some embodiments of the present disclosure. Again, optional features are represented by dashed boxes. As used herein, a "virtualized” network node is an implementation of the network node 1100 in which at least a portion of the functionality of the network node 1100 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, if the network node 1100 is a RAN node (e.g., the RAN node 402), the network node 1100 may include the control system 1102 and / or the one or more radio units 1110, as described above. The control system 1102 may be connected to the radio unit(s) 1110 via, for example, an optical cable or the like. The network node 1100 includes one or more processing nodes 1200 coupled to or included as part of a network(s) 1202. If present, the control system 1102 or the radio unit(s) are connected to the processing node(s) 1200 via the network 1202. Each processing node 1200 includes one or more processors 1204 (e.g., CPUs, ASICs, FPGAs, and / or the like), memory 1206, and a network interface 1208.

[0098] In this example, functions 1210 of the network node 1100 described herein (e.g., one or more functions of the RAN node 402 or one or more functions of an NF such as the AMF 500, PCF 502, or SMF 504, as described herein) are implemented at the one or more processing nodes 1200 or distributed across the one or more processing nodes1200 and the control system 1102 and / or the radio unit(s) 1110 in any desired manner. In some particular embodiments, some or all of the functions 1210 of the network node 1100 described herein are implemented as virtual components executed by one or more virtual machines implemented in a virtual environment(s) hosted by the processing node(s) 1200. As will be appreciated by one of ordinary skill in the art, additional signaling or communication between the processing node(s) 1200 and the control system 1102 may be used in order to carry out at least some of the desired functions 1210. Notably, in some embodiments, the control system 1102 may not be included, in which case the radio unit(s) 1110 may communicate directly with the processing node(s) 1200 via an appropriate network interface(s).

[0099] 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 network node 1100 or a node (e.g., a processing node 1200) implementing one or more of the functions 1210 of the network node 1100 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).

[0100] Figure 13 is a schematic block diagram of the UE 408 according to some embodiments of the present disclosure. As illustrated, the UE 408 includes one or more processors 1302 (e.g., CPUs, ASICs, FPGAs, and / or the like), memory 1304, and one or more transceivers 1306 each including one or more transmitters 1308 and one or more receivers 1310 coupled to one or more antennas 1312. The transceiver(s) 1306 includes radio-front end circuitry connected to the antenna(s) 1312 that is configured to condition signals communicated between the antenna(s) 1312 and the processor(s) 1302, as will be appreciated by one of ordinary skill in the art. The processors 1302 are also referred to herein as processing circuitry. The transceivers 1306 are also referred to herein as radio circuitry. In some embodiments, the functionality of the UE 408 described above may be fully or partially implemented in software that is, e.g., stored in the memory 1304 and executed by the processor(s) 1302. Note that the UE 408 may include additional components not illustrated in Figure 13 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 UE 408 and / or allowing output of information from the UE 408), a power supply (e.g., a battery and associated power circuitry), etc.

[0101] 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 UE 408 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).

[0102] Although the computing devices described herein (e.g., UEs, network nodes, hosts) may include the illustrated combination of hardware components, other embodiments may comprise computing devices with different combinations of components. It is to be understood that these computing devices may comprise any suitable combination of hardware and / or software needed to perform the tasks, features, functions, and methods disclosedherein. Determining, calculating, obtaining or similar operations described herein may be performed by processing circuitry, which may process information by, for example, converting the obtained information into other information, comparing the obtained information or converted information to information stored in the network node, and / or performing one or more operations based on the obtained information or converted information, and as a result of said processing making a determination. Moreover, while components are depicted as single boxes located within a larger box, or nested within multiple boxes, in practice, computing devices may comprise multiple different physical components that make up a single illustrated component, and functionality may be partitioned between separate components. For example, a communication interface may be configured to include any of the components described herein, and / or the functionality of the components may be partitioned between the processing circuitry and the communication interface. In another example, non-computationally intensive functions of any of such components may be implemented in software or firmware and computationally intensive functions may be implemented in hardware.

[0103] In certain embodiments, some or all of the functionality described herein may be provided by processing circuitry executing instructions stored on in memory, which in certain embodiments may be a computer program product in the form of a non-transitory computer-readable storage medium. In alternative embodiments, some or all of the functionality may be provided by the processing circuitry without executing instructions stored on a separate or discrete device-readable storage medium, such as in a hard-wired manner. In any of those particular embodiments, whether executing instructions stored on a non-transitory computer-readable storage medium or not, the processing circuitry can be configured to perform the described functionality. The benefits provided by such functionality are not limited to the processing circuitry alone or to other components of the computing device, but are enjoyed by the computing device as a whole, and / or by end users and a wireless network generally.

[0104] Those skilled in the art will recognize improvements and modifications to the embodiments of the present disclosure. All such improvements and modifications are considered within the scope of the concepts disclosed herein.

Claims

CLAIMS1. A method performed by a Radio Access Network, RAN, node (402) in a RAN of a wireless communications system (400) that comprises the RAN and a core network (406), the method comprising:receiving (600-1; 700), from a User Equipment, UE, (408), an initial registration request for registration with an Access and Mobility Management Function, AMF, in the core network (406);selecting (600-2; 702), at the RAN node (402), an AMF (500) for the UE (408);sending (600-3; 704) the initial registration request to the selected AMF (500);receiving (600-5; 718) an initial registration accept message and Non-Access Stratum, NAS, related information from the selected AMF (500), wherein:the initial registration accept message comprises a temporary AMF identifier, ID, that points to a certain AMF and is to be used by the UE (408) for NAS signaling between the UE (408) and the certain AMF, the certain AMF being either the selected AMF (500) or some other AMF to which the selected AMF (500) forwarded the initial registration request; andthe NAS related information comprises an address of the certain AMF and one or more additional addresses of one or more respective additional NFs selected by the certain AMF for the UE (408); storing (600-5; 720) the address of the certain AMF and the one or more additional addresses of the one or more respective additional NFs selected by the certain AMF for the UE (408) at the RAN node (402) in association with the UE (408); andtransmitting (600-6; 722), to the UE (408), the initial registration accept message comprising the temporary AMF ID, in response to the initial registration request received from the UE (408).

2. The method of claim 1, wherein the initial registration accept message sent to the UE (408) does not include the NAS related information comprising the address of the certain AMF and the one or more additional addresses of the one or more respective additional NFs.

3. The method of claim 1 or 2, wherein storing (600-5) the address of the certain AMF and the one or more additional addresses of the one or more respective additional NFs selected by the AMF (500) for the UE (408) at the RAN node (402) in association with the UE (408) comprises storing (600-5) the address of the certain AMF and the one or more additional addresses of the one or more respective additional NFs selected by the AMF (500) for the UE (408) at the RAN node (402) in a RAN UE context of the UE (408) stored by the RAN node (402).

4. The method of any of claims 1 to 3, wherein the one or more additional NFs selected by the AMF (500) for which the one or more additional addresses are received and stored by the RAN node (402) comprise any one or more of the following: a Policy and Control Function, PCF, address of a selected PCF, a Unified Data Management, UDM, address of a selected UDM, a Short Message Service Function, SMSF, address of a selected SMSF, an NF address of an NF that provides one or more policy related functions, and an NF address of an NF that stores UE subscription data.

5. The method of any of claims 1 to 4, wherein the initial registration request comprises a Subscriber Concealed Identity, SUCI, of the UE (408).

6. The method of any of claims 1 to 5, further comprising:receiving (602-1; 604-1), from the UE (408), a second initial registration request for registration with a second Network Function, NF, (504; 502) in the core network (406), wherein the one or more additional NFs for which the RAN node (402) received the one or more additional addresses from the certain AMF and stored the one or more additional addresses in association with the UE (408) comprise a second NF (504; 502); andselecting (602-2; 604-2), at the RAN node (402), the second NF (504; 502) for the UE (408) based on the address of the second NF stored at the RAN node (402).

7. The method of any of claims 1 to 5, further comprising:receiving (602-1; 604-1), from the UE (408), a second initial registration request for registration with a second Network Function, NF, (504; 502) in the core network (406);receiving (602-1; 604-1), from the UE (408), NF selection assistance information together with the second initial registration request; andselecting (602-2; 604-2), at the RAN node (402), a second NF (504; 502) for the UE (408) based on the NF selection assistance information received from the UE (408).

8. The method of claim 7, wherein the NF selection assistance information received from the UE (408) comprises any one or more of the following: a Subscriber Concealed Identity, SUCI, of the UE (408); a Data Network Name, DNN; and network slice information.

9. The method of claim 7 or 8, further comprising:sending (602-3; 604-3) the second initial registration request to the second NF (504; 502); and receiving (602-5; 604-5) a second initial registration accept message and second NAS related information from the second NF (504; 502) in response to the second initial registration request sent to the second NF (504; 502), wherein:the second initial registration accept message comprises a temporary NF ID that points to the second NF (504; 502) to be used by the UE (408) for NAS signaling between the UE (408) and the second NF (504; 502) and is associated to a UE context of the UE (408) at the second NF (504; 502); andthe second NAS related information comprises an NF address of the second NF (504; 502); and sending (602-6; 604-6), to the UE (408), the second initial registration accept message comprising the temporary NF ID that points to the second NF (504; 502), in response to the second initial registration accept message received from the UE (408).

10. The method of claim 9, wherein the second initial registration accept message sent to the UE (408) does not include the NF address of the second NF (504; 502).

11. The method of any of claims 7 to 10, wherein the second NF (504) is an SMF (504).

12. The method of claim 11, further comprising:retrieving (902-2 and 902-4) SMF selection subscription data for the UE (408);wherein selecting (602-2) the second NF (504) for the UE (408) comprises selecting (602-2) the SMF (504) based on the NF selection assistance information received from the UE (408) and the SMF selection subscription data, using local configuration or Network Repository Function, NRF, query.

13. The method of claim 12, further comprising:selecting (902-1) a Unified Data Management, UDM, (506) based on a Subscription Concealed Identity, SUCI, of the UE (408) received in or together with the second initial registration request;wherein retrieving (902-2 and 902-4) the SMF selection subscription data for the UE (408) comprises: sending (902-2) a request for the SMF selection subscription data to the selected UDM (506), the request comprising the SUCI of the UE (408); andreceiving (902-4) a response from the selected UDM (506), the response comprising the SMF selection subscription data of the UE (408).

14. The method of claim 13, wherein the SMF selection subscription data of the UE (408) comprises any one or more of the following data: a preferred network slice, DNN(s) requirements, one or more roaming policies, and one or more specific SMF capabilities needed for a service profile of the UE (408).

15. The method of any of claims 7 to 10, wherein the second NF (504) is a Policy Control Function, PCF, (502).

16. The method of claim 15, wherein:the one or more additional NFs for which the RAN node (402) received the one or more additional addresses from the certain AMF and stored the one or more additional addresses in association with the UE (408) comprise a selected PCF (502); andselecting (604-2) the second NF (502) for the UE (408) comprises selecting (604-2) the PCF (502) based on the address of the selected PCF (502) stored at the RAN node (402).

17. The method of claim 15, wherein:the one or more additional NFs for which the RAN node (402) received the one or more additional addresses from the certain AMF and stored the one or more additional addresses in association with the UE (408) does not comprise a selected PCF (502);the method further comprises retrieving (1006-2 and 1006-4) PCF selection subscription data for the UE (408); if the PCF selection subscription data for the UE (408) comprises a PCF address, selecting (604-2) the second NF (502) for the UE (408) comprises selecting (1006-5) the PCF (502) based on the PCF address comprised in the PCF selection subscription data for the UE (408).

18. The method of claim 17, further comprising:selecting (1006-1) a Unified Data Management, UDM, (506) based on a Subscription Concealed Identity, SUCI, of the UE (408) received in or together with the second initial registration request;wherein retrieving (1006-2 and 1006-4) the PCF selection subscription data for the UE (408) comprises: sending (1006-2) a request for the PCF selection subscription data to the selected UDM (506), the request comprising the SUCI of the UE (408); andreceiving (1006-4) a response from the selected UDM (506), the response comprising the PCF selection subscription data of the UE (408).

19. The method of claim 17, wherein, if the PCF selection subscription data for the UE (408) does not comprise a PCF address, selecting (604-2) the second NF (502) for the UE (408) comprises selecting (1008-5) the PCF (502) based on a Subscription Permanent Identity, SUPI, of the UE (408) or other key, using a Network Repository Function, NRF, query or local configuration.

20. A Radio Access Network, RAN, node (402) for a RAN of a wireless communications system (400) that comprises the RAN and a core network (406), the RAN node (402) adapted to:receive (600-1; 700), from a User Equipment, UE, (408), an initial registration request for registration with an Access and Mobility Management Function, AMF, in the core network (406);select (600-2; 702), at the RAN node (402), an AMF (500) for the UE (408);send (600-3; 704) the initial registration request to the selected AMF (500);receive (600-5; 718) an initial registration accept message and Non-Access Stratum, NAS, related information from the selected AMF (500), wherein:the initial registration accept message comprises a temporary AMF identifier, ID, that points to a certain AMF and is to be used by the UE (408) for NAS signaling between the UE (408) and the certain AMF, the certain AMF being either the selected AMF (500) or some other AMF to which the selected AMF (500) forwarded the initial registration request; andthe NAS related information comprises an address of the certain AMF and one or more additional addresses of one or more respective additional NFs selected by the certain AMF for the UE (408); store (600-5; 720) the address of the certain AMF and the one or more additional addresses of the one or more respective additional NFs selected by the certain AMF for the UE (408) at the RAN node (402) in association with the UE (408); andtransmit (600-6; 722), to the UE (408), the initial registration accept message comprising the temporary AMFID, in response to the initial registration request received from the UE (408).

21. The RAN node (402) of claim 20, further adapted to perform the method of any of claims 2 to 19.

22. A Radio Access Network, RAN, node (402) for a RAN of a wireless communications system (400) that comprises the RAN and a core network (406), the RAN node (402) comprising processing circuitry configured to cause the RAN node to:receive (600-1; 700), from a User Equipment, UE, (408), an initial registration request for registration with an Access and Mobility Management Function, AMF, in the core network (406);select (600-2; 702), at the RAN node (402), an AMF (500) for the UE (408);send (600-3; 704) the initial registration request to the selected AMF (500);receive (600-5; 718) an initial registration accept message and Non-Access Stratum, NAS, related information from the selected AMF (500), wherein:the initial registration accept message comprises a temporary AMF identifier, ID, that points to a certain AMF and is to be used by the UE (408) for NAS signaling between the UE (408) and the certain AMF, the certain AMF being either the selected AMF (500) or some other AMF to which the selected AMF (500) forwarded the initial registration request; andthe NAS related information comprises an address of the certain AMF and one or more additional addresses of one or more respective additional NFs selected by the certain AMF for the UE (408); store (600-5; 720) the address of the certain AMF and the one or more additional addresses of the one or more respective additional NFs selected by the certain AMF for the UE (408) at the RAN node (402) in association with the UE (408); andtransmit (600-6; 722), to the UE (408), the initial registration accept message comprising the temporary AMF ID, in response to the initial registration request received from the UE (408).

23. The RAN node (402) of claim 22, wherein the processing circuitry is further configured to cause the RAN node (402) to perform the method of any of claims 2 to 19.

24. A method performed by an Access and Mobility Management Function, AMF, (500) in a core network (406) of a wireless communications system (400) that comprises a Radio Access Network, RAN, and the core network (406), the method comprising:receiving (704), from a RAN node (402), an initial registration request for registration of a User Equipment, UE, (408) with the AMF (500);selecting (710 and 712), at the AMF (500), one or more additional Network Functions, NFs, (502; 504); sending (718) an initial registration accept message and Non-Access Stratum, NAS, related information to the RAN node (402), wherein:the initial registration accept message comprises a temporary AMF identifier, ID, that points to theAMF (500) and is to be used by the UE (408) for NAS signaling between the UE (408) and the AMF (500); andthe NAS related information comprises an address of the AMF (500) and one or more additional addresses of the one or more respective additional NFs selected by the AMF (500) for the UE (408).

25. The method of claim 24, wherein the address of the AMF (500) and the one or more additional addresses of the one or more respective additional NFs selected by the AMF (500) are for storage at the RAN node (402) in association with the UE (408) for subsequent use by the RAN node (402).

26. The method of claim 24 or 25, wherein the one or more additional NFs selected by the AMF (500) comprise any one or more of the following: a Policy and Control Function, PCF, address of a selected PCF, a Unified Data Management, UDM, address of a selected UDM, a Short Message Service Function, SMSF, address of a selected SMSF, an NF address of an NF that provides one or more policy related functions, and an NF address of an NF that stores UE subscription data.

27. The method of any of claims 24 to 26, wherein the initial registration request received from the RAN node (402) comprises a Subscriber Concealed Identity, SUCI, of the UE (408).

28. The method of any of claims 24 to 27, further comprising obtaining (706-708) a UE context of the UE (408) from an old AMF (705) that was previously selected for the UE (408), the UE context comprising an address of at least one of the one or more additional NF (502; 504), wherein selecting (710; 712) the one or more additional NFs comprises selecting the one or more additional NFs based on the UE context obtained from the old AMF (705).

29. The method of any of claims 24 to 28, further comprising registering (716) with a Unified Data Management, UDM, (506) for the UE (408) such that the UDM (506) stores an indication that initial registration of the UE (408) with an AMF is completed.

30. The method claim 29, wherein the one or more NFs comprise a selected Policy and Control Function, PCF, (502), and registering (716) the AMF (500) with the UDM (506) for the UE (408) further comprises storing (718') a PCF identifier, ID, of the selected PCF in the UDM (506).

31. An Access and Mobility Management Function, AMF, (500) for a core network (406) of a wireless communications system (400) that comprises a Radio Access Network, RAN, and the core network (406), the AMF (500) adapted to:receive (704), from a RAN node (402), an initial registration request for registration of a User Equipment, UE, (408) with the AMF (500);select (710 and 712), at the AMF (500), one or more additional Network Functions, NFs, (502; 504);send (718) an initial registration accept message and Non-Access Stratum, NAS, related information to the RAN node (402), wherein:the initial registration accept message comprises a temporary AMF identifier, ID, that points to the AMF (500) and is to be used by the UE (408) for Non-Access Stratum, NAS, signaling between the UE (408) and the AMF (500); andthe NAS related information comprises an address of the AMF (500) and one or more additional addresses of the one or more respective additional NFs selected by the AMF (500) for the UE (408).

32. The AMF (500) of claim 31 , further adapted to perform the method of any of claims 25 to 30.

33. A network node for implementing an Access and Mobility Management Function, AMF, (500) for a core network (406) of a wireless communications system (400) that comprises a Radio Access Network, RAN, and the core network (406), the network node comprising processing circuitry configured to cause the network node to:receive (704), from a RAN node (402), an initial registration request for registration of a User Equipment, UE, (408) with the AMF (500);select (710 and 712), at the AMF (500), one or more additional Network Functions, NFs, (502; 504); send (718) an initial registration accept message and Non-Access Stratum, NAS, related information to the RAN node (402), wherein:the initial registration accept message comprises a temporary AMF identifier, ID, that points to the AMF (500) and is to be used by the UE (408) for Non-Access Stratum, NAS, signaling between the UE (408) and the AMF (500); andthe NAS related information comprises an address of the AMF (500) and one or more additional addresses of the one or more additional NFs selected by the AMF (500).

34. The network node of claim 33, wherein the processing circuitry is further configured to cause the network node to perform the method of any of claims 25 to 30.

35. A method performed by Network Function, NF, (502; 504) in a core network (406) of a wireless communications system (400) that comprises a Radio Access Network, RAN, and the core network (406), the method comprising:receiving (904; 1010), from a RAN node (402), an initial registration request for registration of a User Equipment, UE, (408) with the NF;retrieving (912-914; 1018-1020) an indication that indicates whether initial registration of the UE (408) with an Access and Mobility Management Function, AMF, (500) is completed; andresponsive to the indication indicating the initial registration of the UE (408) with an AMF (500) is completed, sending (916; 1022) an initial registration accept message to the RAN node (402).

36. The method of claim 35, wherein the initial registration request comprises a Subscription Concealed Identity, SUCI, of the UE (408), and the method further comprises:retrieving (906, 910; 1014, 1016) a Subscription Permanent Identity, SUPI, of the UE (408) based on the SUCI of the UE (408);wherein retrieving (912-914; 1018-1020) the indication that indicates whether initial registration of the UE (408) with an AMF (500) is completed comprise retrieving (912-914; 1018-1020) the indication that indicates whether initial registration of the UE (408) with an AMF (500) as part of a UE Context Management, UECM, registration in which the NF (502; 504) is registered for the UE (408).

37. The method of claim 35 or 36, further comprising sending (916; 10922) an address of the NF (502; 504) to the RAN node (402) together with or in association with the initial registration accept message.

38. The method of any of claims 35 to 37, wherein the initial registration accept message comprises a temporary identity, ID, of the SMF (504) to be used by the UE (408) for NAS signaling between the UE (408) and the SMF (504), wherein, at the SMF (504), the temporary ID is associated to a UE context of the UE (408) stored at the SMF (504).

39. The method of any of claims 35 to 38, wherein the NF (504) is a Session Management Function, SMF, (504) or a Policy Control Function, PCF, (502).

40. The method of any of claims 35 to 38, wherein the NF (504) is a Session Management Function, SMF, (504), and the initial registration accept message comprises an address of the SMF and a Protocol Data Unit, PDU, session ID or other parameter that associates a certain PDU session of the UE (408) with the address of the SMF (504).

41. A Network Function, NF, (502; 504) for a core network (406) of a wireless communications system (400) that comprises a Radio Access Network, RAN, and the core network (406), the NF (502; 504) adapted to:receive (904; 810), from a RAN node (402), an initial registration request for registration of a User Equipment, UE, (408) with the NF;retrieve (912-914; 1018-1020) an indication that indicates whether initial registration of the UE (408) with an Access and Mobility Management Function, AMF, (500) is completed; andresponsive to the indication indicating the initial registration of the UE (408) with an AMF (500) is completed, send (916; 1022) an initial registration accept message to the RAN node (402).

42. The NF (502; 504) of claim 41 , further adapted to perform the method of any of claims 36 to 40.

43. A network node for implementing a Network Function, NF, (502; 504) for a core network (406) of a wireless communications system (400) that comprises a Radio Access Network, RAN, and the core network (406), the network node comprising processing circuitry configured to cause the network node to:receive (904; 810), from a RAN node (402), an initial registration request for registration of a User Equipment, UE, (408) with the NF;retrieve (912-914; 1018-1020) an indication that indicates whether initial registration of the UE (408) with an Access and Mobility Management Function, AMF, (500) is completed; andresponsive to the indication indicating the initial registration of the UE (408) with an AMF (500) is completed, send (916; 1022) an initial registration accept message to the RAN node (402).

44. The network node of claim 43, wherein the processing circuitry is further configured to cause the network node to perform the method of any of claims 36 to 40.

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