Method of the second core network device

Abstract

A technique is disclosed for registering a User Equipment (UE) with a new Access and Mobility Management Function (AMF). If a new Access and Mobility Management Function (AMF) determines that the old AMFs are independent AMFs, i.e., they are not connected, the new AMF retrieves the UE context (5GMM and 5GSM context) from the old AMF via a New Generation Radio Access Network (NG-RAN). The new AMF routes a Namf_Communication_UEContextTransfer request message to the old AMF to retrieve the UE context via the NG-RAN. The old AMF sends the UE context in a Namf_Communication_UEContextTransfer response message to the new AMF via the NG-RAN. Based on the context transfer between the new AMF and the old AMF, the UE is registered with the new AMF.

Description

[Technical field]

[0001] The present disclosure discloses a procedure for handling a registration procedure and a user data transmission procedure related to disjoint slices in a 5G core network. The present subject matter discloses how a UE performs a registration procedure for disjoint AMFs when each disjoint AMF supports different network slices. [Background technology]

[0002] The network slicing capabilities defined in 3GPP Release 15 and Release 16 enable a wide variety of communication services across operators and verticals. To increase the commercial viability of network slicing, the GSMA 5GJA introduced in document NG.116 the concept of Generic Slice Templates (GSTs) [2] from which descriptions of several network slice types can be derived. Some of the parameters of the GST explicitly indicate the definition of the parameters and boundaries of the services offered to the end customer. However, the application of some of these boundaries and parameters is not yet supported in 5GS.

[0003] The 3GPP SA1 study related to Rel-18's Enhanced Access and Support for Network Slices [3] considers various use cases and scenarios using network slicing to identify potential service requirements for 5G systems. Some of the use case scenarios are: -If network slicing has restrictions such as specific frequency bands / sub-bands, RATs, geographical areas, networks, applications, etc. -If the UE is subscribed to multiple network slices and these network slices are deployed, for example, for different frequency bands / subbands, RATs, geographical areas, applications, -When there is priority for a network slice over other network slices, for example when there are conflicting constraints on the availability of network slices.

[0004] Currently, when a service spans multiple independent networks, a UE cannot simultaneously use multiple services provided by the independent networks. Switching services where services are provided by different independent networks causes a large amount of signaling and delay in service activation. Summary of the Invention [Problem to be solved by the invention]

[0005] The following presents a simplified summary of the subject matter in order to provide a basic understanding of some aspects of the subject matter embodiments. This summary is not an extensive overview of the subject matter. It is not intended to identify key / critical elements of the embodiments or to delineate the scope of the subject matter.

[0006] Its sole purpose is to present some concepts of the subject matter in a simplified form as a prelude to the more detailed description that is presented later.

[0007] According to one embodiment of the present disclosure, if the new Access and Mobility Management Function (AMF) determines that the old AMFs are independent AMFs from each other, i.e., they are not connected, the new AMF acquires the UE context (5GMM and 5GSM context) from the old AMF via a New Generation Radio Access Network (NG-RAN). The new AMF forwards a Namf_Communication_UEContextTransfer request message to the old AMF to acquire the UE context via the NG-RAN. The old AMF sends the UE context in a Namf_Communication_UEContextTransfer response message to the new AMF via the NG-RAN. Based on the context transfer between the new AMF and the old AMF, the UE is registered to the new AMF.

[0008] According to another embodiment, if the AMF receives a registration request message including a requested network slice selection assistance information (NSSAI) set in an S-NSSAI that cannot be processed by the current AMF while the UE is in the 5GMM-CONNECTED state, the AMF requests the UE to perform a re-registration procedure with the new AMF by including a re-registration indication in the registration accept message. In this way, the UE is registered with the new AMF.

[0009] According to another embodiment of the present subject matter, a management scheme for disjoint networks is introduced by introducing a disjoint network identifier, which is used to uniquely identify a disjoint network within a Public Land Mobile Network (PLMN). The disjoint network identifier is provided to the NG-RAN by the AMF so that the NG-RAN can maintain an association between the AMF and the disjoint network identifier. Effect of the Invention

[0010] These and other objects, embodiments and advantages of the present disclosure will become readily apparent to those skilled in the art from the following detailed description of the embodiments, taken in conjunction with the accompanying drawings; however, the present disclosure is not limited to the particular embodiments disclosed. [Brief description of the drawings]

[0011] The foregoing and further objects, features and advantages of the subject matter of the present invention will become apparent from the following description of illustrative embodiments which refers to the accompanying drawings, in which like reference numerals are used to represent like elements, and in which:

[0012] It should be noted, however, that the attached drawings, bearing reference numbers, depict only typical embodiments of the subject matter of the present invention and should therefore not be considered as limiting the scope of the invention, which is likewise tolerable to other, particularly advantageous, embodiments.

[0013] [Figure 1] FIG. 1 illustrates a prior art use case scenario in which a radio access network connects to two different slices using two different Access and Management Functions (AMFs) in an exemplary embodiment of the present subject matter.

[0014] [Figure 2A]FIG. 2A illustrates an example of a registration procedure involving user equipment (UE) context transfer between independent AMFs in another exemplary embodiment of the present subject matter. [Figure 2B] FIG. 2B illustrates an example of a registration procedure involving user equipment (UE) context transfer between independent AMFs in another exemplary embodiment of the present subject matter.

[0015] [Figure 3A] FIG. 3A illustrates an example of a registration procedure with Protocol Data Unit (PDU) session suspension when a UE changes access from one network slice to another network slice that belong to mutually independent networks in yet another exemplary embodiment of the present subject matter. [Figure 3B] FIG. 3B illustrates an example of a registration procedure with Protocol Data Unit (PDU) session suspension when a UE changes access from one network slice to another network slice that belong to mutually independent networks in yet another exemplary embodiment of the present subject matter.

[0016] [Figure 4A] FIG. 4A illustrates an example of a registration procedure with PDU session resumption in yet another exemplary embodiment of the present subject matter. [Figure 4B] FIG. 4B illustrates an example of a registration procedure with PDU session resumption in yet another exemplary embodiment of the present subject matter.

[0017] [Diagram 5] FIG. 5 illustrates an example of a registration procedure while the UE is in a 5GMM-CONNECTED state in an exemplary embodiment of the present subject matter.

[0018] [Figure 6] FIG. 6 illustrates independent network identifier management between 5GC and NG-RAN in an exemplary embodiment of the present subject matter.

[0019] [Figure 7] FIG. 7 illustrates a procedure in which the AMF notifies a next-generation radio access network (NG-RAN) of an independent network identifier triggered by the NG-RAN in an exemplary embodiment of the present subject matter.

[0020] [Figure 8] FIG. 8 shows a procedure triggered by the AMF in an exemplary embodiment of the present subject matter, in which the AMF notifies the NG-RAN of an independent network identifier.

[0021] [Figure 9] FIG. 9 illustrates a block diagram of a UE in an exemplary embodiment of the present subject matter.

[0022] [Figure 10] FIG. 10 illustrates a block diagram of an exemplary (R)AN node in an exemplary embodiment of the present subject matter.

[0023] [Figure 11] FIG. 11 shows a block diagram of an AMF in an exemplary embodiment of the present subject matter.

[0024] [Figure 12] FIG. 12 illustrates a registration procedure in an exemplary implementation of the present subject matter. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] Each of the exemplary embodiments described below can be implemented independently or in combination with other embodiments.

[0026] Those skilled in the art will appreciate that elements in the figures are illustrated for simplicity and may not necessarily be drawn to scale. Further, with respect to the structure of a device, one or more components of the device may be represented in the figures with conventional symbols, and the figures may show only certain details relevant to understanding the embodiments of the present disclosure, so as not to obscure the figures with details that will be readily apparent to those skilled in the art having the benefit of the description herein.

[0027] For the purposes of promoting an understanding of the principles of the disclosure, reference will be made to the embodiments illustrated in the drawings and specific language will be used to describe them. It will be understood, however, that no limitation to the scope of the disclosure is intended thereby. Such changes and further modifications in the illustrated system, and further applications of the principles of the disclosure as would normally occur to one skilled in the art, are to be construed as being within the scope of the disclosure.

[0028] The terms "comprise", "comprising", or other variations thereof, are intended to cover a non-exclusive inclusion, such that a process or method that includes a list of steps does not include only those steps, but may include other steps not expressly listed or inherent to such process or method. Similarly, the term "comprise" preceding one or more devices, entities, subsystems, elements, structures, or components does not preclude the presence of other devices, subsystems, elements, structures, components, additional devices, additional subsystems, additional elements, additional structures, or additional components, absent further constraints. The phrases "in one embodiment", "in another embodiment" and similar expressions throughout this specification may, but do not necessarily, all refer to the same embodiment.

[0029] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. The systems, methods, and examples provided herein are merely illustrative and are not intended to be limiting. In the following specification and claims, reference will be made to a number of terms, which shall be defined to have the following meanings: The singular forms "a," "an," and "the" include plural references unless the context clearly dictates otherwise.

[0030] As used herein, information is associated with data and knowledge, since data is meaningful information and represents values ​​attributed to parameters. Further knowledge refers to understanding of abstract or concrete concepts. It should be noted that this exemplary system is simplified to facilitate the description of the disclosed subject matter and is not intended to limit the scope of the present disclosure. Other devices, systems, and configurations may be used in addition to or instead of the system to implement the embodiments disclosed herein, and all such embodiments are considered to be within the scope of the present disclosure.

[0031] These figures show simplified structures showing only some elements and functional entities, all of which are logical units, whose implementation may differ from those shown. The connections shown are logical connections, and the actual physical connections may differ. It is clear to those skilled in the art that this structure may also include other functions and structures. Also, all logical units described and shown in the figures include software and / or hardware components necessary for the unit to function. Furthermore, each unit may include one or more components that are implicitly understood within itself. These components may be operatively coupled to each other and configured to communicate with each other to perform the functions of said units.

[0032] In the current state of the art, as more network slices are deployed, it is more likely that each UE will join multiple network slices. Some network slice services can be provided to UEs simultaneously, but there may be network slices that cannot provide services to UEs simultaneously. This is because network slices have multiple related factors (e.g., enterprise and personal use, separation requirements, general public and public safety use, frequency restrictions, location restrictions, etc.).

[0033] FIG. 1 illustrates a use case scenario in which a RAN node connects to slice M provided via AMF Y and slice N provided by AMF X of the same PLMN in an exemplary embodiment of the present subject matter. For example, slice M is used for public security, and slice N is used for Internet access. In 5GC, dedicated network resources and network functions are customized separately for public safety emergency services and video services to meet the separation requirements, which ensures the independence of core network resources between different network slices. Therefore, the two network slices are separated and cannot be provided to a UE at the same time. Such network slices are called network slices independent of each other.

[0034] Subscription and configuration: -UEs A1 and A3 have subscriptions to slice M. -UEs A2 and A3 have subscriptions to slice N. -For UE A3, it is configured which application uses which network slice.

[0035] introduction: -Slice N and slice M are separated. -RAN can be connected to both slice M and slice N. - Slice M and slice N are provided by the same PLMN.

[0036] A UE may be configured with network slices M and N that are independent of each other, where network slice M and network slice N are supported by two different AMFs that do not have an N14 interface, i.e. due to the independence requirement that the two AMFs cannot communicate directly. Similarly, it is assumed that a 5GC node handling network slice M cannot communicate with a 5GC node handling network slice N due to the independence requirement. For example, an AMF handling network slice M cannot communicate with any SMF handling network slice N.

[0037] At some point, the UE registers with the AMF handling network slice M in order to access services related to network slice M. The UE receives a trigger from an application to access network slice N without simultaneously accessing separate network slices. In this situation, it is not clear how the UE can be registered with the AMF handling network slice N.

[0038] For a UE authorized to access multiple network slices of one operator that cannot be used simultaneously, the 5G system must support minimal interruption when the UE changes access from one network slice to another (e.g. when triggered by a change in an active application).

[0039] According to an exemplary embodiment of the present subject matter, if the new AMF determines that the old AMF is an independent AMF, i.e., they are not connected, then the new AMF acquires the UE context (5GMM and 5GSM context) from the old AMF via the NG-RAN. The new AMF routes a Namf_Communication_UEContextTransfer request message to the old AMF to acquire the UE context via the NG-RAN. The old AMF sends the UE context in a Namf_Communication_UEContextTransfer response message to the new AMF via the NG-RAN.

[0040] FIG. 2A illustrates an example of a registration procedure involving UE context transfer between independent AMFs in an exemplary embodiment of the present subject matter. FIG. 2B illustrates an example of a registration procedure involving UE context transfer between independent AMFs in an exemplary embodiment of the present subject matter.

[0041] The detailed steps of the procedure are described below.

[0042] Step 0. The UE is configured with S-NSSAI 1 and S-NSSAI 2, which are processed by AMF1 (which only supports S-NSSAI 1) and AMF2 (which only supports S-NSSAI 2), respectively. AMF1 and AMF2 are AMFs independent of each other, i.e., direct communication between the two AMFs is not possible, i.e., there is no N14 interface between AMF1 (e.g., old AMF) and AMF2 (e.g., new AMF). AMF1 and AMF2 belong to the same PLMN.

[0043] The UE is registered with AMF1 to access services related to S-NSSAI 1. The UE is assigned 5G-GUTI 1 by AMF1 and S-NSSAI 2 is the only network slice in the allowed NSSAI. The UE is in 5GMM-IDLE state.

[0044] Step 1. A UE receives a trigger from an application to register only in S-NSSAI 2 (eg, the UE receives a trigger to send user data of an application associated with S-NSSAI 2).

[0045] Step 2. The UE establishes an RRC connection to the NG-RAN. The UE sends an RRC Setup Complete message to the NG-RAN with a dedicated NAS-Message IE containing 5G-GUTI1, S-NSSAI List IE = S-NSSAI 2, and a Registration Request message containing the requested NSSAI = S-NSSAI 2.

[0046] Step 3. The NG-RAN receives an RRC Setup Complete message containing 5G-GUTI1 and S-NSSAI2 in the S-NSSAI List IE and a Registration Request message in the dedicated NAS message IE. The NG-RAN analyzes the received RRC Setup Complete message and can conclude that the UE is registered to AMF1 based on the received 5G-GUTI 1, and that AMF1 cannot support S-NSSAI2 based on the supported S-NSSAI information received during the NG setup procedure between the NG-RAN and AMF1.

[0047] Step 4. Based on the analysis of step 3, the NG-RAN knows that the UE is associated with AMF1, but the NG-RAN sends an Initial UE message containing a Registration Request (Requested NSSAI = S-NSSAI2 and 5G-GUTI 1) to AMF2.

[0048] Step 5. Upon receiving the registration request message, AMF2 checks the received 5G-GUTI1 to see whether the UE context can be obtained directly from AMF1 (e.g., old AMF).

[0049] Step 6. If AMF2 determines that it can obtain the UE context from AMF1 (e.g., old AMF) via NG-RAN based on the local configuration, AMF2 sends a Reroute_N14_Request message to NG-RAN, including 5G-GUTI 1, AMF2 address (e.g., IP address or FQDN of AMF2), and N14 message container (Namf_Communication_UEContextTransfer Request). The AMF2 address information routable from any independent network can be configured by AMF2 or obtained by AMF2 from NRF as described in Section 6.3.5 of 3GPP TS23.501[4]. Alternatively, AMF2 allocates a new 5G-GUTI to the UE and sets it in the Reroute_N14_Request message.

[0050] Step 7. When the NG-RAN receives the Reroute_N14_Request message, it sends a Reroute_N14_transfer message to AMF1 containing the AMF2 address or / and the new 5G-GUTI and the N14 message container (Namf_Communication_UEContextTransfer). The AMF1 address is derived from the GUAMI part of the 5G-GUTI. The NG-RAN may store the address of AMF2.

[0051] Note that an NG-RAN may need to manage multiple IP address spaces for each independent network, e.g., IP addresses derived from the GUAMI portion of 5G-GUTI may only be valid in such an independent network.

[0052] Note that the NG-RAN may have a Network Address Translation (NAT) function to support multiple independent networks. When messages on the N2 and N3 reference points need to pass through different independent networks, the NG-RAN performs the NAT function to enable communication between AMFs and UPFs in different independent networks.

[0053] Step 8. The AMF1 sends a Reroute_N14_Request message to the NG-RAN containing the included AMF2 address (e.g., AMF2 IP address or FQDN) or / and the new 5G-GUTI and an N14 message container (Namf_Communication_UEContextTransfer Response). The Namf_Communication_UEContextTransfer Response contains the UE context.

[0054] Step 9. When the NG-RAN receives the Reroute_N14_Request message, the NG-RAN sends a Reroute_N14_transfer message including an N14 message container (Namf_Communication_UEContextTransfer Response) to the AMF2. The Reroute_N14_transfer message including the N14 message container (Namf_Communication_UEContextTransfer Response) may include an AMF2 address or / and a new 5G-GUTI. If the new 5G-GUTI is configured in the NG-RAN, the AMF2 address is derived from the GUAMI part of the new 5G-GUTI when the Reroute_N14_Request message is received.

[0055] Step 10. The registration procedure continues as described in section 4.2.2.2.2 of 3GPP TS 23.502 [5].

[0056] Step 11. After the registration procedure is successful, AMF2 assigns 5G-GUTI2 to the UE as the new 5G-GUTI and sends it in the registration accept message.

[0057] Step 12. Upon receiving the registration accept message, the UE acknowledges the receipt of the registration accept message by sending a registration complete message to the AMF2.

[0058] According to another exemplary embodiment of the present subject matter, if the new AMF determines that AMF1 (e.g., old AMF) is an independent AMF from another AMF, i.e., they are not connected, the established PDU session is suspended because AMF2 (e.g., new AMF) cannot maintain the established PDU due to its independent requirement.

[0059] FIG. 3A illustrates an example of a registration procedure with Protocol Data Unit (PDU) session suspension when a UE changes access from one network slice to another network slice that belong to mutually independent networks in an exemplary embodiment of the present subject matter. FIG. 3B illustrates an example of a registration procedure with Protocol Data Unit (PDU) session suspension when a UE changes access from one network slice to another network slice that belong to mutually independent networks in an exemplary embodiment of the present subject matter.

[0060] The detailed steps of the procedure are defined below.

[0061] Step 0. The UE is configured with S-NSSAI 1 and S-NSSAI 2, which are processed by AMF1 (which only supports S-NSSAI 1) and AMF2 (which only supports S-NSSAI 2), respectively. AMF1 and AMF2 are AMFs independent of each other, i.e., direct communication between the two AMFs is not possible, i.e., there is no N14 interface between the old AMF and the new AMF. AMF1 and AMF2 belong to the same PLMN.

[0062] The UE is registered with AMF1 to access services related to S-NSSAI 1. The UE is assigned 5G-GUTI 1 by AMF1, and S-NSSAI 1 is the only network slice in the allowed NSSAI. The UE is in 5GMM-IDLE state. A PDU session is established for S-NSSAI 1. For example, a user plane is established between UPF1 and a data network.

[0063] Step 1. A UE receives a trigger from an application to register only in S-NSSAI 2 (eg, the UE receives a trigger to send user data of an application associated with S-NSSAI 2).

[0064] Step 2. The UE establishes an RRC connection to the NG-RAN. The UE sends an RRC Setup Complete message to the NG-RAN with a dedicated NAS-Message IE containing 5G-GUTI 1, S-NSSAI List IE = S-NSSAI 2, and a Registration Request message containing the requested NSSAI = S-NSSAI 2, and optionally a list of activated PDU sessions = S-NSSAI 2. If the UE knows that established PDU sessions need to be paused, it can set the list of PDU sessions to be paused in the Information Element (IE) using the Pause Timer IE in the Registration Request message.

[0065] Step 3. The NG-RAN receives an RRC Setup Complete message containing 5G-GUTI1 and S-NSSAI2 in the S-NSSAI List IE and a Registration Request message in the dedicated NAS message IE. The NG-RAN analyzes the received RRC Setup Complete message and can conclude that the UE is registered to AMF1 based on the received 5G-GUTI 1 and that AMF1 cannot support S-NSSAI 2 based on the supported S-NSSAI information received during the NG setup procedure between the NG-RAN and AMF1.

[0066] Step 4. Based on the analysis of step 3, the NG-RAN knows that the UE is associated with AMF1, but the NG-RAN sends an Initial UE message containing a Registration Request (requested NSSAI = S-NSSAI 2 and 5G-GUTI 1) to AMF2.

[0067] Step 5. Upon receiving the REGISTER REQUEST message, AMF2 checks the received 5G-GUTI1 to see if the UE context can be obtained directly from the AMF (e.g., old AMF). If AMF2 receives the suspend target PDU session list IE with the suspension timer IE, AMF2 may set the suspend target PDU session list IE with the suspension timer IE in the Namf_Communication_UEContextTransfer message. AMF2 may decide to set the list IE of PDU sessions to be suspended with the suspension timer IE in the Namf_Communication_UEContextTransfer message based on the local configuration.

[0068] Step 6. If AMF2 determines that the UE context can be obtained from the AMF (e.g., old AMF) through NG-RAN based on the local configuration, AMF2 sends a Reroute_N14_Request message to NG-RAN, including 5G-GUTI 1, AMF2 address (e.g., IP address or FQDN of AMF2), and N14 message container (Namf_Communication_UEContextTransfer Request). The AMF2 address information routable from any independent network can be configured by AMF2 or obtained by AMF2 from NRF as described in Section 6.3.5 of 3GPP TS 23.501 [4]. Alternatively, AMF2 allocates a new 5G-GUTI to the UE and sets it in the Reroute_N14_Request message.

[0069] Step 7. When the NG-RAN receives the Reroute_N14_Request message, it sends a Reroute_N14_transfer message to AMF1 containing the AMF2 address or / and the new 5G-GUTI and the N14 message container (Namf_Communication_UEContextTransfer). The AMF1 address is derived from the GUAMI part of the 5G-GUTI. The NG-RAN may store the address of AMF2.

[0070] Step 8. When AMF1 receives the Reroute_N14_Trasnfer message containing the Namf_Communication_UEContextTransfer message, AMF1 determines that some or all of the established PDU sessions (i.e., the PDU sessions related to S-NSSAI 1) need to be suspended or released.

[0071] This decision is taken by AMF1, for example, based on the following reasons: The received Namf_Communication_UEContextTransfer message includes a list of PDU sessions to be suspended and a suspension timer IE. -AMF1 recognizes that AMF2 does not support S-NSSAI 1. -AMF1 recognizes that AMF2 is an independent AMF.

[0072] Step 9. AMF1 invokes Nsmf_PDUSession_UpdateSMContext request (PDU Session ID, Cause, Operation Type, User Location Information, Location Age, N2SM Information (Secondary RAT Usage Data), Suspend Timer) to SMF1. The operation type is set to "UP Suspend" to indicate temporary suspension of user plane resources of the PDU session.

[0073] Step 10. The SMF1 initiates the N4 session modification procedure by sending an N4 Session Modification Request (Buffering On / Off) message to the UPF1, indicating that the data coming from the data network should be buffered at UPF1 if buffering is indicated, otherwise no data needs to be buffered. If the message contains a paused timer, the SMF starts the pause timer in the SMF.

[0074] If the pause timer expires, the SMF initiates the PDU session release procedure as described in Section 4.3.4 of 3GPP TS 23.502 [5].

[0075] UPF1 sends an N4 session modification response to confirm SMF1's request.

[0076] Step 11. SMF1 sends a Nsmf_PDUSession_UpdateSMContext response to AMF1. Please note that steps 9 to 11 in Figure 3A and Figure 3B are equivalent to steps 2 to 4 in Figure 4.8.1.2-1: NG-RAN Initiated Connection Pause Procedure in 3GPP TS 23.502 [5].

[0077] Step 12. The AMF1 sends a Reroute_N14_Request message to the NG-RAN with the included AMF2 address (e.g., AMF2 IP address or FQDN) and / or the new 5G-GUTI and an N14 message container (Namf_Communication_UEContextTransfer Response). The Namf_Communication_UEContextTransfer Response may contain the result of pausing the PDU session.

[0078] Step 13. When the NG-RAN receives the Reroute_N14_Request message, the NG-RAN sends a Reroute_N14_transfer message including an N14 message container (Namf_Communication_UEContextTransfer Response) to the AMF2. The Reroute_N14_transfer message (Namf_Communication_UEContextTransfer Response) including the N14 message container may include an AMF2 address or / and a new 5G-GUTI. If the new 5G-GUTI is configured in the NG-RAN, the AMF2 address is derived from the GUAMI part of the new 5G-GUTI when the Reroute_N14_Request message is received.

[0079] Step 14. The registration procedure continues as described in section 4.2.2.2.2 of 3GPP TS 23.502 [5].

[0080] Step 15. After the registration procedure is successful, AMF2 assigns 5G-GUTI2 to the UE as the new 5G-GUTI and sends it in a registration accept message. The list of suspended PDU sessions IE is set in the registration accept message.

[0081] According to another exemplary embodiment of the present subject matter, when AMF1 (e.g., new AMF) discovers that some of the PDU sessions have been paused, AMF2 (e.g., new AMF) resumes the paused PDU sessions.

[0082] FIG. 4A illustrates an example of a registration procedure with PDU session resumption in an exemplary embodiment of the present subject matter. FIG. 4B illustrates an example of a registration procedure with PDU session resumption in an exemplary embodiment of the present subject matter.

[0083] The detailed steps of the procedure are defined below.

[0084] Step 0. The UE is configured with S-NSSAI 1 and S-NSSAI 2, which are processed by AMF1 (which only supports S-NSSAI 1) and AMF2 (which only supports S-NSSAI 2), respectively. AMF1 and AMF2 are AMFs independent of each other, i.e., direct communication between the two AMFs is not possible, i.e., there is no N14 interface between the old AMF and the new AMF. AMF1 and AMF2 belong to the same PLMN.

[0085] The UE is registered with AMF2 to access services related to S-NSSAI 2. The UE is assigned 5G-GUTI2 by AMF2, and S-NSSAI 2 is the only network slice in the allowed NSSAI. The UE is in 5GMM-IDLE state. PDU sessions are suspended for S-NSSAI 1. User plane is established between UPF1 and the data network, for example.

[0086] Step 1. A UE receives a trigger from an application to register only in S-NSSAI 1 (eg, the UE receives a trigger to send user data of an application associated with S-NSSAI 1).

[0087] Step 2. The UE establishes an RRC connection to the NG-RAN. The UE sends an RRC Setup Complete message to the NG-RAN with a dedicated NAS-Message IE containing 5G-GUTI2, S-NSSAI List IE = S-NSSAI 1, and a Registration Request message containing the requested NSSAI = S-NSSAI 1 and optionally the list of activated PDU sessions = S-NSSAI 1. If the UE knows that an established PDU session is paused, the UE may set the list of PDU sessions to be resumed in an information element (IE) in the Registration Request message.

[0088] Step 3. The NG-RAN receives an RRC Setup Complete message containing 5G-GUTI2 and S-NSSAI1 in the S-NSSAI List IE and a Registration Request message in the dedicated NAS message IE. The NG-RAN analyzes the received RRC Setup Complete message and can conclude that the UE is registered to AMF2 based on the received 5G-GUTI 2 and that AMF2 cannot support S-NSSAI 1 based on the supported S-NSSAI information received during the NG setup procedure between the NG-RAN and AMF2.

[0089] Step 4. Based on the analysis of step 3, the NG-RAN knows that the UE is associated with AMF2, but the NG-RAN sends an Initial UE message containing a Registration Request (requested NSSAI = S-NSSAI 1 and 5G-GUTI 2) to AMF1.

[0090] Step 5. When AMF1 receives the registration request message, it checks the received 5G-GUTI and determines whether it can directly obtain the UE context from the old AMF.

[0091] Step 6. If AMF1 determines that it can obtain the UE context from the old AMF via NG-RAN based on the local configuration, AMF1 sends 5G-GUTI2, AMF1 address (e.g., AMF's IP address or FQDN1), and N14 message container (Namf_Communication_UEContextTransfer) to NG-RAN. The AMF1 address information routable from any independent network can be configured by AMF1 or obtained by AMF1 from the NRF as described in Section 6.3.5 of 3GPP TS23.501[4]. Alternatively, AMF1 allocates a new 5G-GUTI to the UE and sets it in the Reroute_N14_Request message.

[0092] Step 7. When the NG-RAN receives the Reroute_N14_Request message, it sends a Reroute_N14_transfer message to the AMF2, containing the AMF1 address or / and the new 5G-GUTI and the N14 message container (Namf_Communication_UEContextTransfer). The AMF2 address is derived from the GUAMI part of the 5G-GUTI. The NG-RAN may store the address of the AMF1.

[0093] Step 8. The AMF2 sends a Reroute_N14_Request message to the NG-RAN with the included AMF1 address (e.g., AMF2’s IP address or FQDN) and / or the new 5G-GUTI and N14 message container (Namf_Communication_UEContextTransfer Response).

[0094] Step 9. When the NG-RAN receives the Reroute_N14_Request message, the NG-RAN sends a Reroute_N14_transfer message including an N14 message container (Namf_Communication_UEContextTransfer Response) to the AMF1. The Reroute_N14_transfer message including the N14 message container (Namf_Communication_UEContextTransfer Response) may include an AMF1 address or / and a new 5G-GUTI. If the new 5G-GUTI is configured in the NG-RAN, the AMF1 address is derived from the GUAMI part of the new 5G-GUTI when the Reroute_N14_Request message is received.

[0095] Step 10. If the AMF1 receives the list IE of PDU sessions to be resumed in the Registration Request message of step 4 or based on local information, the AMF1 sends a Nsmf_PDUSession_UpdateSMContext Request (Resume Request, PDU Session ID) to the SMF1.

[0096] Step 11. SMF1 resumes the user plane for each PDU session by sending an N4 Session Modify Request for each PDU session to UPF1. After resuming the user plane, UPF1 sends an N4 Session Modify Response message to SMF1.

[0097] Step 12. SMF1 sends Nsmf_PDUSession_UpdateSMContext response to AMF1. Note that steps 10 to 12 in Figure 4A and Figure 4B are equivalent to steps 5 to 7 in Figure 4.8.2.3-1: Connection resumption in CM-IDLE with pause in 3GPP TS 23.502 [5].

[0098] Step 13. The registration procedure continues as described in section 4.2.2.2.2 of 3GPP TS 23.502 [5].

[0099] Step 14. After the registration procedure is successful, AMF1 assigns 5G-GUTI1 to the UE as the new 5G-GUTI and sends it in the registration accept message.

[0100] In yet another exemplary embodiment, while the UE is in a 5GMM-CONNECTED state, when the AMF receives a registration request message including a requested NSSAI set to an S-NSSAI that cannot be processed by the current AMF, the AMF requests the UE to perform a re-registration procedure including a re-registration indication in the registration accept message.

[0101] FIG. 5 illustrates an example of a registration procedure while the UE is in a 5GMM-CONNECTED state in an exemplary embodiment of the present subject matter.

[0102] The detailed steps of the procedure are defined as follows:

[0103] Step 0. The UE is configured with S-NSSAI 1 and S-NSSAI 2, which are processed by AMF1 (which only supports S-NSSAI 1) and AMF2 (which only supports S-NSSAI 2), respectively. AMF1 and AMF2 are AMFs independent of each other, i.e., no direct communication between the two AMFs is possible, i.e., there is no N14 interface between the old AMF and the new AMF. AMF1 and AMF2 belong to the same PLMN.

[0104] The UE is initially registered with AMF1 to access services related to S-NSSAI 1. The UE is assigned 5G-GUTI 1 by AMF1. The UE is in 5GMM-IDLE state. A PDU session is established for S-NSSAI 1, i.e., a user plane is established between the UPF and the data network.

[0105] Step 1. A UE receives a trigger to register to only S-NSSAI 2 (e.g., the UE receives a trigger to transmit user data related to only S-NSSAI 2).

[0106] Step 2. The UE sends a Registration Request message with Requested NSSAI=S-NSSAI 2.

[0107] Step 3. Upon receiving the Registration Request message, AMF1 determines that it cannot process S-NSSAI 2 due to independent requirements.

[0108] Step 4. After the UE transitions to the 5GMM-IDLE state, the AMF sends a registration accept message including a re-registration indication to request the UE to perform the registration procedure. In one example, the AMF can use a registration reject message instead of the registration accept message.

[0109] Step 5. Upon receiving the registration accept message containing the re-registration indication, the UE sends a registration complete message to the AMF1.

[0110] Step 6. The UE transitions to 5GMM-IDLE mode.

[0111] Step 7. When the UE transitions to 5GMM-IDLE mode, the UE initiates the registration procedure including the requested NSSAI = S-NSSAI2 in the registration request message. The UE and the network shall follow the independent inter-network registration procedure. This approach allows the UE to change access from one network slice to another without service interruption.

[0112] As an example, the UE may initiate a registration procedure including the requested NSSAI = S-NSSAI2 in the registration request message even if it has not transitioned to 5GMM-IDLE mode, which may occur if an application using S-NSSAI2 makes an urgent request to establish a connection.

[0113] In another exemplary embodiment, if the registration request message includes a requested NSSAI=S-NSSAI1+S-NSSAI2 and the AMF determines that the S-NSSAI2 has a higher priority than the S-NSSAI1 based on the user subscription, then the AMF executes this exemplary embodiment. In this case, the AMF1 includes an Allowed NSSAI=S-NSSAI 1 and a Rejected S-NSSAI=S-NSSAI2, and includes a rejection cause value set to re-registration in the registration accept message of step 4. When the UE receives the registration accept message, the UE attempts to register to the S-NSSAI2 after transitioning to 5GMM-IDLE mode. Alternatively, the AMF sends a new information element (IE) re-registration NSSAI set to S-NSSAI2 in the registration accept message. When the UE receives the registration accept message including this IE, the UE attempts to register to the S-NSSAI2 after transitioning to 5GMM-IDLE mode.

[0114] In another exemplary embodiment of the present subject matter, a management scheme for independent networks is provided by introducing independent network identifiers. As described above with reference to FIG. 1, this use case requires that each independent network is completely independent or isolated between the independent networks. This means that there is no direct connection between each independent network because they are not connected to each other. In this network environment, each independent network may have its own IP address space.

[0115] To enable communication between different independent networks, this exemplary embodiment introduces an independent network management scheme by introducing an independent network identifier. The independent network identifier is used to uniquely identify an independent network within a PLMN. The independent network identifier is provided to the NG-RAN by the AMF so that the NG-RAN can maintain an association between the AMF and the independent network identifier.

[0116] An independent network identifier is assigned per AMF (i.e., AMF identifier or AMF name) or per AMF set ID, depending on the local configuration of the PLMN.

[0117] The independent network identifier can be an AMF Set-ID as defined in 3GPP TS 23.002[7], an AMF TNL association as defined in 3GPP TS 38.413[6], a Network Identifier (NID) as defined in 3GPP TS 23.501[4], a CAG Identifier as defined in 3GPP TS 23.501[4], or any other identifier that the PLMN can manage.

[0118] The independent network identifiers may be referred to as isolated network identifiers, separate network identifiers, private network identifiers, or non-connected network identifiers.

[0119] FIG. 6 illustrates independent network identifier management between 5GC and NG-RAN in an exemplary embodiment of the present subject matter.

[0120] Each independent network has its own independent network identifier. The independent network identifiers are assigned by the PLMN operator. All 5GC nodes, including AMF, UPF, SMF, PCF, etc., are associated with independent network identifiers. Some of the 5GC nodes may belong to multiple independent network identifiers depending on the PLMN operator's policies.

[0121] Each independent network, identified by an independent network identifier, can have its own IP address space, which can be a global IP address space or a local IP address space. Because each independent network has its own IP address space, there can be overlapping IP addresses between independent networks.

[0122] When an N2 reference point is established or updated, the AMF informs the NG-RAN of the independent network identifier or a list of independent network identifiers. The NG-RAN may use the independent network identifier to use Network Address Translation (NAT) if the N2 message passes through another independent network. The NG-RAN may use the independent network identifier to use Network Address and Port Translation (NAPT) if the N2 message passes through another independent network.

[0123] FIG. 7 illustrates a procedure in which, in an exemplary embodiment of the present subject matter, the AMF is triggered by the NG-RAN to notify the NG-RAN of mutually independent network identifiers.

[0124] The detailed steps of the procedure are defined as follows:

[0125] Step 1. The NG-RAN sends an NGAP request message to the AMF. The NG-RAN may indicate a multiple independent network support indication to the AMF. The multiple independent network support indication indicates that the NG-RAN supports multiple independent networks. The NGAP request message may be a NG SETUP REQUEST message or a RAN CONFIGURATION UPDATE message.

[0126] Step 2. When the AMF receives the NGAP request message containing the multiple independent network support indication, the AMF sends an NGAP response message containing the multiple independent network support indication and the independent network identifier to the NG-RAN. The NG-RAN uses the independent network identifier to perform NAT translation or NAPT translation for N2 message processing when the N2 message passes through another independent network. The NGAP response message may be a NG SETUP RESPONSE message or a RAN CONFIGURATION UPDATE ACKNOWLEDGE message.

[0127] Figure 8 illustrates a procedure triggered by the AMF to notify the NG-RAN of an independent network identifier.

[0128] The detailed steps of the procedure are defined as follows:

[0129] Step 1. The AMF sends an NGAP request message to the NG-RAN, the NGAP request message including a multiple independent network support indication and an independent network identifier. The multiple independent network support indication indicates that the AMF supports multiple independent networks. The NGAP request message may be an AMF CONFIGURATION UPDATE message.

[0130] Step 2. When the NG-RAN receives the NGAP request message including the multiple independent network support indication and the independent network identifier, the NG-RAN sends an NGAP response message including the multiple independent network support indication to the AMF. The NG-RAN uses the independent network identifier to perform NAT translation or NAPT translation for N2 message processing when the N2 message passes through another independent network. The NGAP response message may be a CONFIGURATION UPDATE ACKNOWLEDGE message.

[0131] FIG. 9 illustrates a block diagram showing the main components of a UE in an exemplary embodiment of the present subject matter. As illustrated, the UE includes a transceiver circuit operable to transmit signals to and receive signals from connected nodes via one or more antennas. Although not necessarily illustrated in FIG. 9, the UE of course includes all the usual functionality of a conventional mobile device (such as a user interface), which may be provided by any suitable one or combination of hardware, software, and firmware, as follows: Software may be pre-installed in memory and / or downloaded over a communication network or from a removable data storage device (RMD).

[0132] The controller controls the operation of the UE according to software stored in the memory. The software includes, among others, an operating system and a communication control module having at least a transceiver control module. The communication control module (with a transceiver control submodule) is responsible for signaling and processing (generating / sending / receiving) uplink / downlink data packets between the UE and other nodes such as base stations / (R)AN nodes, MME, AMF (and other core network nodes), etc. Such signaling may include, for example, appropriately formatted signaling messages related to establishing and maintaining connections (e.g., RRC connection establishment and other RRC messages), periodic location update related messages (e.g., tracking area updates, paging area updates, location area updates), etc. Such signaling may also include, for example, receiver-side broadcast information (e.g., master information and system information).

[0133] FIG. 10 is a block diagram illustrating the main components of an exemplary (R)AN node, e.g., a base station ("eNB" in LTE, "gNB" in 5G) in an exemplary embodiment of the present subject matter. As shown, the (R)AN node comprises a transceiver circuit operable to transmit and receive signals to and from connected UEs via one or more antennas, and to transmit and receive signals to and from other network nodes (directly or indirectly) via a network interface. A controller controls the operation of the (R)AN node according to software stored in the memory. The software may be pre-installed in the memory and / or downloaded over a communication network or from a removable data storage device (RMD). The software includes, among other things, an operating system and a communication control module having at least a transceiver control module.

[0134] The communication control module (with its transceiver control submodule) is responsible for handling (generating / sending / receiving) signaling (e.g., directly or indirectly) between the (R)AN node and other nodes such as UEs, MMEs, AMFs, etc. Signaling may include, for example, suitably formatted signaling messages related to radio connectivity and location procedures (for a particular UE), in particular connection establishment and maintenance (e.g., RRC connection establishment and other RRC messages), messages related to periodic location location (e.g., tracking area updates, paging area updates, location area updates), S1 AP messages and NG AP messages (i.e., messages with N2 reference point), etc. Such signaling may also include, for example, broadcast information (e.g., master information and system information) in case of transmission.

[0135] The controller, if implemented, is also configured (by software or hardware) to handle related tasks such as UE mobility estimation and / or motion trajectory estimation.

[0136] FIG. 11 is a block diagram illustrating the main components of the AMF in an exemplary embodiment of the present subject matter. The AMF is included in the 5GC. As shown, the AMF includes a transceiver circuit operable to transmit and receive signals to other nodes (including UEs) via a network interface. A controller controls the operation of the AMF according to software stored in the memory. The software may be pre-installed in the memory and / or downloaded via a communication network or from a removable data storage device (RMD). The software includes, among other things, an operating system and a communication control module having at least a transceiver control module.

[0137] The Communications Control module (using a Transceiver Control sub-module) is responsible for handling (generating / sending / receiving) signaling (directly or indirectly) between the AMF and other nodes such as UEs, base stations / (R)AN nodes (e.g., "gNBs" or "eNBs"). Such signaling may include, for example, appropriately formatted signaling messages related to the procedures described herein, such as NG AP messages (i.e., messages over the N2 reference point) for conveying NAS messages to and from the UE.

[0138] User equipment (or "UE", "mobile station", "mobile device" or "wireless device") in this disclosure is an entity that connects to a network via an air interface.

[0139] It should be noted that the UE in this specification is not limited to a dedicated communication device, but can be applied to any device having the communication function as the UE described in this specification, as described below.

[0140] The terms "user equipment" or "UE" (as this term is used in 3GPP), "mobile station", "mobile device", and "wireless device" are generally intended to be synonymous with each other and include standalone mobile stations such as terminals, mobile phones, smartphones, tablets, cellular IoT devices, IoT devices, and machines.

[0141] It will be understood that the terms "UE" and "wireless device" also encompass devices that remain stationary for extended periods of time.

[0142] The UE may be, for example, an item of production or manufacturing equipment and / or an item of energy-related machinery (e.g. equipment or machinery such as boilers, engines, turbines, solar panels, wind turbines, hydroelectric generators, thermal generators, nuclear generators, batteries, nuclear systems, and / or related equipment, heavy electrical machinery, pumps including vacuum pumps, compressors, fans, blowers, hydraulic equipment, pneumatic equipment, metal working machinery, manipulators, robots and / or application systems thereof, tools, dies or moulds, rolls, conveying equipment, lifting equipment, material handling equipment, textile machinery, sewing machines, printing and / or related machinery, paper processing machinery, chemical machinery, mining and / or construction machinery and / or related equipment, agricultural, forestry and / or fishing machinery and / or implements, safety and / or environmental protection equipment, tractors, precision bearings, chains, gears, power transmission equipment, lubrication equipment, valves, pipe fittings, and / or application systems of any of the aforementioned equipment or machinery, etc.).

[0143] A UE may be, for example, an item of transportation equipment (e.g., rail cars, automobiles, motorcycles, bicycles, trains, buses, carts, rickshaws, boats and other watercraft, aircraft, rockets, satellites, drones, balloons, etc.).

[0144] A UE may be, for example, an item of information and communications equipment (eg, information and communications equipment such as electronic computers and related equipment, communications and related equipment, electronic components, etc.).

[0145] The UE may be, for example, a refrigerator, a refrigerator application product, trade and / or service industry equipment, a vending machine, an automated service machine, an office machine or equipment, a household appliance and an electronic device (e.g., audio equipment, video equipment, loudspeakers, radios, televisions, microwave ovens, rice cookers, coffee makers, dishwashers, washing machines, dryers, electric fans or related equipment, household appliances such as cleaners, etc.).

[0146] The UE may be, for example, an electrical application system or device (eg, an electrical application system or device such as an x-ray system, a particle accelerator, a radioisotope device, an acoustic device, an electromagnetic application device, a power application device, etc.).

[0147] The UE may be, for example, an electronic lamp, a lighting fixture, a measuring instrument, an analyzer, a tester, or a surveying or sensing instrument (e.g., a surveying or sensing instrument such as a smoke alarm, an occupancy alarm sensor, a motion sensor, a radio tag, etc.), a watch, a laboratory instrument, an optical instrument, a medical instrument and / or system, a weapon, a knife, a hand tool, etc.

[0148] The UE may be, for example, a radio-equipped personal digital assistant or related equipment, such as a wireless card or module designed to be attached or inserted into another electronic device (eg, a personal computer, an electrical measuring instrument).

[0149] The UE may be a device or part of a system that uses various wired and / or wireless communication technologies to provide the applications, services, and solutions described below with respect to the Internet of Things (IoT).

[0150] Internet of Things devices (or "things") can be equipped with appropriate electronics, software, sensors, network connections, etc. that enable these devices to collect and exchange data with each other or with other communicating devices. IoT devices may consist of automated equipment that follows software instructions stored in their internal memory. IoT devices may operate without the need for human supervision or interaction. IoT devices may also remain stationary and inactive for long periods of time. IoT devices may be implemented as part of (typically) fixed equipment. IoT devices may also be embedded in non-fixed equipment (e.g. vehicles) or attached to animals or people being monitored / tracked.

[0151] It will be understood that IoT technologies may be implemented on any communication device capable of connecting to a communication network to transmit and receive data, regardless of whether such communication device is controlled by human input or by software instructions stored in memory.

[0152] It will be appreciated that an IoT device may also be referred to as a Machine-Type Communication (MTC) device, a Machine-to-Machine (M2M) communication device, or a Narrowband IoT UE (NB-IoT UE). It will be appreciated that a UE may support one or more IoT or MTC applications. Some examples of MTC applications are listed in Table 3 (Source: 3GPP TS22.368, Annex B, the contents of which are incorporated herein by reference). This list is not intended to be exhaustive, but rather to illustrate some examples of machine-type communication applications. The list is shown in Table 1 below.

[0153] Table 1: Some examples of machine type communication applications. [Table 1]

[0154] The applications, services, and solutions may be MVNO (Mobile Virtual Network Operator) services, emergency wireless communication systems, PBX (Private Branch Exchange) systems, PHS / digital cordless telecommunications systems, POS (Point of Sale) systems, advertising call systems, MBMS (Multimedia Broadcast and Multicast Service), V2X (Vehicle to Everything) systems, train radio systems, location-related services, disaster / emergency wireless communication services, community services, video distribution services, femtocell application services, VoLTE (Voice over LTE) services, billing services, radio on-demand services, roaming services, activity monitoring services, telecommunications carrier / communications network selection services, function restriction services, PoC (Proof of Concept) services, personal information management services, ad hoc networks / DTN (Delay Tolerant Networking) services, and the like.

[0155] Furthermore, the above-mentioned UE categories are merely examples of application of the technical concepts and exemplary embodiments described herein, and it should be understood that these technical concepts and embodiments are not limited to the above-mentioned UEs, and various modifications are possible.

[0156] Although the present invention has been particularly shown and described with reference to exemplary embodiments thereof, the present invention is not limited to these embodiments. Those skilled in the art will appreciate that various changes in form and details can be made without departing from the spirit and scope of the present disclosure as defined by this document. For example, the above embodiments are not limited to 5GS, but are also applicable to communication systems other than 5GS.

[0157] All or part of the embodiments disclosed above can be described as follows, but are not limited to these.

[0158] (Appendix 1) receiving an initial wireless terminal message from a Radio Access Network (RAN); determining whether a wireless terminal context can be obtained; sending a reroute request to the RAN; receiving a reroute forwarding message from the RAN; transmitting a registration acceptance message to the wireless terminal; A method of a second core network device comprising:

[0159] (Appendix 2) receiving a reroute forwarding message from a Radio Access Network (RAN); Pausing a Protocol Data Unit (PDU) session; Sending a PDU session related request message to a third core network device; receiving a PDU session related response message from the third core network device; sending a reroute request message to the NG-RAN; Equipped with the reroute request message is sent to the RAN before the second core network device sends a registration accept message to the wireless terminal; A method of a first core network device.

[0160] (Appendix 3) receiving an initial wireless terminal message from a Radio Access Network (RAN); determining whether a wireless terminal context can be obtained; sending a reroute request message to the RAN; receiving a reroute forwarding message from the RAN; Sending a Protocol Data Unit (PDU) session related request message to a third core network device; receiving the PDU session related response message from the third core network device; Equipped with The PDU session related response message is received before the second core network device sends a registration accept message to the wireless terminal. A method of a first core network device.

[0161] (Appendix 4) receiving a registration request from a wireless terminal; determining that the first core network device does not process a network slice associated with the second core network device; sending a registration accept message to said wireless terminal; receiving a registration complete message from the wireless terminal; A method of a first core network device comprising:

[0162] (Appendix 5) sending a request message to a first core network device, the request message including information related to the plurality of independent networks; receiving a response message from the first core network device, the response message including information associated with a plurality of independent networks and an identifier associated with the independent network; A method for a radio access network comprising:

[0163] (Appendix 6) transmitting a request message to a radio access network, the request message including information associated with a plurality of independent networks and an identifier associated with the independent networks; receiving a response message from the radio access network, the response message including information related to a plurality of independent networks; A method of a first core network device comprising:

[0164] (Appendix 7) The second core network device is a second access and mobility management function (AMF); 5. The method according to any one of claims 1 to 4.

[0165] (Appendix 8) The first core network device is a first access and mobility management function (AMF); 7. The method according to any one of claims 2 to 6.

[0166] (Appendix 9) and suspending a user plane by the third core network device. The method described in Appendix 2.

[0167] (Appendix 10) and resuming a user plane by the third core network device. The method described in Appendix 3.

[0168] (Appendix 11) The third core network device is a Session Management Function (SMF); 11. The method of claim 2, 3, 9 or 10.

[0169] (Appendix 12) The wireless terminal is a second user equipment (UE: User Equipment). 5. The method according to any one of claims 1 to 4.

[0170] All or part of the embodiments disclosed above can be expressed as follows, but are not limited to these.

[0171] <General registration> The UE is configured with S-NSSAI 1 and S-NSSAI 2. S-NSSAI 1 and S-NSSAI are independent slices from each other. That is, they are supported by two different AMFs (old AMF supports S-NSSAI 1 and new AMF supports S-NSSAI 2). There is no interface between old AMF1 and new AMF. That is, old AMF and new AMF cannot communicate directly and belong to the same registration area. In the following procedures, old AMF is AMF1 and new AMF is AMF2.

[0172] Step 0. The UE registers with the old AMF of S-NSSAI 1 and is assigned 5G-GUTI 1. The allowed NSSAI consists only of S-NSSAI 1. The UE receives a trigger to initiate services related to S-NSSAI 2 only.

[0173] Step 1. UE to (R)AN: AN message (AN parameters, Registration Request (Registration Type, SUCI or 5G-GUTI 1 or PEI, Last Visited TAI (if available), Security Parameters, Requested NSSAI, Mapping of Requested NSSAI, Defaulted NSSAI Indication, UE Radio Capability Update, UE MM Core Network Capabilities, PDU Session Status, List of Activated PDU Sessions, Subsequent Request, MICO Mode Configuration, Requested Active Time, Requested DRX Parameters for E-UTRA and NR, Requested DRX Parameters for NB-IoT, Enhanced Idle Mode DRX Parameters, Indication of LADN DNN or LADN Information Request, NAS Message Container, Support for Enhanced Coverage Usage Restrictions, Preferred Network Behaviour, UE Paging Probability Information, UE Policy Container (List of PSI, Indication of UE ANDSP Support, and Operating System Identifier)], and UE Radio Capability ID, PEI). NOTE 1: The UE Policy Container and its usage are defined in TS 23.503

[20] .

[0174] The requested NSSAI is set to S-NSSAI 2. For NG-RAN, the AN parameters include, e.g., 5G-S-TMSI or GUAMI, the selected PLMN ID (or PLMN ID and NID, see clause 5.30 of TS 23.501[2]), and NSSAI information. The AN parameters also include an establishment cause. The establishment cause provides the reason for requesting establishment of an RRC connection. Whether and how the UE includes the NSSAI information as part of the AN parameters depends on the value of the Access Stratum Connection Establishment NSSAI Inclusion Mode parameter, as specified in clause 5.15.9 of TS 23.501[2].

[0175] If the UE is an IAB node accessing 5GS, the AN parameters also include an IAB indication.

[0176] The registration type indicates whether the UE wants to perform an Initial Registration (i.e. the UE is in RM-DEREGISTERED state), a Mobility Registration Update (i.e. the UE is in RM-REGISTERED state and initiates the registration procedure for mobility or because the UE needs to update its capabilities or protocol parameters or to request a change in the set of network slices it is allowed to use), a Periodic Registration Update (i.e. the UE is in RM-REGISTERED state and initiates the registration procedure due to expiry of the Periodic Registration Update timer, see section 4.2.2.2.1), or an Emergency Registration (i.e. the UE is in a limited service state).

[0177] If the UE is using E-UTRA, the UE indicates support for CIoT 5GS Optimizations related to AMF selection in the RRC connection establishment signaling associated with the registration request.

[0178] If the UE is performing initial registration, the UE shall indicate the UE identity in the registration request message as follows, which are listed in order of decreasing priority for registration to a PLMN: i) If the UE has a valid EPS GUTI, the 5G-GUTI mapped from the EPS GUTI. ii) If available, the native 5G-GUTI assigned by the PLMN to which the UE is attempting to register. iii) If available, a native 5G-GUTI assigned by a PLMN equivalent to the PLMN to which the UE is attempting to register. iv) Native 5G-GUTI allocated by other PLMNs (if available). NOTE 2: This may also be a 5G-GUTI allocated via another access type. v) Otherwise, the UE shall include the SUCI in the registration request as defined in TS 33.501

[15] .

[0179] If the UE performing initial registration has both a valid EPS GUTI and a native 5G-GUTI, the UE shall also indicate the native 5G-GUTI as an additional GUTI. If multiple native 5G-GUTIs are available, the UE shall select a 5G-GUTI from items (ii) to (iv) in the above list in descending order of priority.

[0180] When registering to an SNPN using 5G-GUTI as UE ID, the UE MUST only use 5G-GUTIs previously assigned by the same SNPN.

[0181] If the UE is sending a Registration Request message as an initial NAS message, and the UE has a valid 5G NAS security context, and the UE needs to send non-clear text IEs, the NAS message container is included, see clause 4.4.6 of TS 24.501

[25] . If the UE does not need to send non-clear text IEs, the UE should send the Registration Request message without the NAS message container.

[0182] If the UE does not have a valid 5G NAS security context, the UE sends the Registration Request message without a NAS message container. The UE MUST include the entire Registration Request message (i.e., including the cleartext and non-cleartext IEs) in the NAS message container that is sent as part of the Security Mode Complete message in step 9b.

[0183] If the UE is performing initial registration with native 5G-GUTI (i.e., when the UE is in RM-DEREGISTERED state), the UE MUST indicate the related GUAMI information in the AN parameters. If the UE is performing initial registration with SUCI, the UE MUST NOT indicate the GUAMI information in the AN parameters.

[0184] If the UE is performing initial registration or mobility registration and CIoT 5GS optimization is supported, the UE shall indicate its preferred network behavior (see clause 5.31.2 of TS 23.501[2]). If S1 mode is supported, the UE's EPC preferred network behavior is included in the S1 UE network capabilities of the Registration Request message (see clause 8.2.6.1 of TS 24.501

[25] ).

[0185] In case of emergency registration, if the UE does not have a valid 5G-GUTI available, the SUCI will be included, if the UE has neither a SUPI nor a valid 5G-GUTI, the PEI will be included. In all other cases, the 5G-GUTI will be included, indicating the last serving AMF.

[0186] The UE may provide the UE usage settings based on its configuration as defined in clause 5.16.3.7 of TS 23.501 [2]. The UE provides the requested NSSAI as described in clause 5.15.5.2.1 of TS 23.501 [2]. In case of initial registration or mobility registration update, the UE also includes the mapping of the requested NSSAI (if available) that maps each S-NSSAI of the requested NSSAI to an HPLMN S-NSSAI and ensures that the network can verify whether the S-NSSAI in the requested NSSAI is allowed based on the subscribed S-NSSAI. In case of inter-PLMN mobility, if the serving PLMN S-NSSAI corresponding to the established PDU session does not exist in the UE, the HPLMN S-NSSAI associated with the established PDU session is provided in the mapping of the requested NSSAI as described in clause 5.15.5.2.1 of TS 23.501 [2].

[0187] If the UE is using the Default Configured NSSAI as defined in TS 23.501 [2], the UE includes the Default Configured NSSAI Indication.

[0188] If the UE supports the allocation of WUS assistance information from the AMF, it may include UE paging probability information (see TS 23.501 [2]).

[0189] In case of mobility registration update, the UE includes in its list of activated PDU sessions those PDU sessions for which there is pending uplink data. When the UE includes in its list of activated PDU sessions, it indicates PDU sessions associated only to the access to which the registration request relates. As defined in TS 24.501

[25] , the UE includes in its list of activated PDU sessions those always-on PDU sessions that are accepted by the network, even if those PDU sessions have no pending uplink data.

[0190] NOTE 3: The PDU session corresponding to the LADN is not included in the list of activated PDU sessions if the UE is outside the coverage area of ​​the LADN.

[0191] The UE MM Core Network Capability is provided by the UE and processed by the AMF as defined in clause 5.4.4a of TS 23.501 [2]. The UE includes in the UE MM Core Network Capability an indication of whether it supports the request type flag "Handover" in the PDN connection request during the attach procedure as defined in clause 5.17.2.3.1 of TS 23.501 [2]. If the UE supports "Strictly Periodic Registration Timer Indication", the UE indicates the capability of "Strictly Periodic Registration Timer Indication" in the UE MM Core Network Capability. If the UE supports CAG, the UE indicates the capability of "CAG Supported" in the UE MM Core Network Capability.

[0192] The UE can provide either an LADN DNN or an indication of LADN information request as described in clause 5.6.5 of TS 23.501 [2].

[0193] If available, the last visited TAI is included to enable the AMF to generate the registration area for the UE.

[0194] The security parameters are used for authentication and integrity protection, see TS 33.501

[15] . The requested NSSAI indicates the network slice selection assistance information (defined in clause 5.15 of TS 23.501 [2]). The PDU session status indicates the previously established PDU session in the UE. If the UE is connected to two AMFs belonging to different PLMNs via 3GPP access and non-3GPP access, the PDU session status indicates the established PDU session in the current PLMN in the UE.

[0195] A Follow-on request is included if the UE has pending uplink signaling and the UE does not contain a list of activated PDU sessions or if the registration type indicates that the UE wants to perform an emergency registration. In the initial registration and mobility registration update, the UE provides the UE request DRX parameters as defined in clause 5.4.5 of TS 23.501 [2]. The UE can request extended idle mode DRX by providing extended idle mode DRX parameters as defined in clause 5.31.7.2 of TS 23.501 [2].

[0196] The UE provides a UE Radio Capability Update indication as described in TS 23.501 [2].

[0197] The UE contains the MICO mode configuration and, optionally, a requested active time value if the UE wants to use the MICO mode during the active time.

[0198] The UE may indicate its service gap control capability to the UE MM core network function, see clause 5.31.16 of TS 23.501 [2].

[0199] For a UE with a service gap timer running in it, the UE shall not set the follow-on requested indication or uplink data status in the registration request message, except for network access for barred priority services, such as emergency services and exception reporting (see clause 5.31.16 of TS 23.501 [2]).

[0200] If the UE supports RACS and has been assigned a UE Radio Capability ID, the UE shall indicate the UE Radio Capability ID as defined in clause 5.4.4.1a of TS 23.501 [2] as a non-context IE.

[0201] The PEI may be obtained from the UE during initial registration as described in section 4.2.2.2.1.

[0202] Step 2. If 5G-S-TMSI or GUAMI is not included, or if 5G-S-TMSI or GUAMI does not indicate a valid AMF, or if the (R)AN determines that the AMF indicated in 5G-S-TMSI or GUAMI does not support the requested NSSAI, then the (R)AN selects an AMF, if available, based on the (R)AT and the requested NSSAI. The (R)AN selects a new AMF.

[0203] The (R)AN selects the AMF as described in clause 6.3.5 of TS 23.501 [2]. If the UE is in CM-CONNECTED state, the (R)AN can forward the registration request message to the AMF based on the UE's N2 connectivity.

[0204] If the (R)AN cannot select an appropriate AMF, it forwards the registration request to an AMF configured to perform AMF selection in the (R)AN.

[0205] Step 3. (R)AN to new AMF: N2 message (N2 parameters, Registration Request (explained in step 1) and [LTE-M indication]).

[0206] If NG-RAN is used, the N2 parameters include a UE context request indicating the UE context including the selected PLMN ID (or PLMN ID and NID, see clause 5.30 of TS 23.501[2]), location information and cell ID related to the cell the UE is camped on, and security information that needs to be configured in the NG-RAN.

[0207] If NG-RAN is used, in step 1, if an indication is received in the AN parameter, the N2 parameter also contains the establishment cause and the IAB-indication.

[0208] Mappings for requested NSSAIs are provided only if available.

[0209] If the registration type indicated by the UE is periodic registration update, steps 4 to 19 may be omitted.

[0210] If the establishment cause is associated with a priority service (MPS, MCS, etc.), the AMF includes a Message Priority header indicating the priority information. Other NFs relay the priority information by including the Message Priority header in their service-based interfaces as specified in TS 29.500

[17] .

[0211] The RAT type used by the UE is determined (see section 4.2.2.2.1) and based on that the AMF decides whether the UE is performing Inter-RAT mobility to or from NB-IoT. If the AMF receives an LTE-M indication, it assumes that the RAT type is LTE-M and stores the LTE-M indication in the UE context.

[0212] When a UE has a preferred network behavior, this defines the network behavior that the UE is expected to support and be available in the network, as defined in clause 5.31.2 of TS 23.501 [2].

[0213] If the UE includes a preferred network behavior and what the UE indicates it supports in the preferred network behavior is not compatible with the network support, the AMF shall reject the registration request with an appropriate cause value (e.g., a value that avoids retries on this PLMN).

[0214] If there is a Service Gap timer running in the UE Context of the AMF of the UE and a follow-on request indication or uplink data status is included in the registration request message, the AMF shall ignore the follow-on request indication and uplink data status and shall not perform any action related to the status.

[0215] If the UE included the UE radio capability ID in step 1 and the AMF supports RACS, the AMF stores the radio capability ID in the UE context.

[0216] Step 4. [Conditional] From new AMF to old AMF: Namf_Communication_UEContextTransfer (Complete registration request), or from new AMF to UDSF: Nudsf_Unstructured Data Management_Query().

[0217] (With UDSF): If the UE's 5G-GUTI is included in the registration request, the serving AMF has changed since the last registration procedure, the new AMF and the old AMF are in the same AMF set, and UDSF is deployed, the new AMF can retrieve the stored UE's SUPI and UE context directly from the UDSF using the Nudsf_UnstructuredDataManagement_Query service operation, or share the stored UE context via implementation-specific means if UDSF is not deployed. This also includes event subscription information by each NF consumer for a given UE. In this case, the new AMF performs and verifies the integrity protection using the complete integrity-protected registration request NAS message.

[0218] (without UDSF introduction): If the UE's 5G-GUTI is included in the registration request and the serving AMF has changed since the last registration procedure, the new AMF may invoke the Namf_Communication_UEContextTransfer service operation on the old AMF with the complete registration request NAS message, possibly integrity protected as well as the access type, to request the UE's SUPI and UE Context. For details on this service operation, see section 5.2.2.2.2. In this case, the old AMF verifies the integrity protection if the invocation of the context transfer service operation corresponds to the UE's request, either with the 5G-GUTI and the integrity protected complete registration request NAS message, or with the SUPI and an indication from the new AMF that the UE is verified. The old AMF also forwards the event subscription information by each NF consumer of the UE to the new AMF. If the old AMF has not yet reported a non-zero MO Exception Data Counter to the (H-)SMF, the context response also includes the MO Exception Data Counter.

[0219] If the registration request message includes 5G-GUTI 1 and the new AMF determines that it does not have an interface with the old AMF corresponding to GUAMI of 5G-GUTI 1, the new AMF sends the Namf_Communication_UEContextTransfer service operation in the following procedure.

[0220] Step 4a. If AMF2 determines that it can obtain the UE context from AMF1 (e.g., old AMF) via NG-RAN based on the local configuration, AMF2 sends a Reroute_N14_Request message to NG-RAN, including 5G-GUTI1, AMF2 address (e.g., IP address or FQDN of AMF2), and N14 message container (Namf_Communication_UEContextTransfer Request). The AMF2 address information routable from any independent network can be configured by AMF2 or obtained by AMF2 from NRF as described in clause 6.3.5 of 3GPP TS23.501[4]. Alternatively, AMF2 allocates a new 5G-GUTI to the UE and sets it in the Reroute_N14_Request message.

[0221] Step 4b. When the NG-RAN receives the Reroute_N14_Request message, it sends a Reroute_N14_transfer message to AMF1, including the AMF2 address and / or the new 5G-GUTI and the N14 message container (Namf_Communication_UEContextTransfer). The AMF address is derived from the GUAMI part of the 5G-GUTI. The NG-RAN may store the address of AMF2.

[0222] Note that an NG-RAN may need to manage multiple IP address spaces for each independent network, e.g., IP addresses derived from the GUAMI portion of 5G-GUTI may only be valid in such an independent network.

[0223] Note that the NG-RAN may have a network address translation (NAT) function to support multiple independent networks. If messages on the N2 and N3 reference points need to pass through different independent networks, the NG-RAN performs the NAT function to enable communication between AMFs and UPFs in different independent networks. Step 4a) If the user plane is established for the PDU session associated with S-NSSAI 1, the AMF suspends the user plane by initiating a Nsmf_PDUSession_UpdateSMContext request (PDU Session ID, Cause, Operation Type, User Location Information, Location Information Age, N2 SM Information (Secondary RAT Usage Data), Suspend Timer) to SMF1. The operation type is set to "UP Suspend" to indicate the suspension of user plane resources for the PDU session.

[0224] Step 4b) The SMF1 initiates the N4 session modification procedure by sending an N4 Session Modification Request (Buffering On / Off) message to the UPF1, indicating that data from the data network should be buffered at UPF1 if buffering is indicated, otherwise no buffering is required. If the message contains a suspend timer, the SMF starts the suspend timer in the SMF.

[0225] If the pause timer expires, the SMF initiates the PDU session release procedure as described in clause 4.3.4 of 3GPP TS 23.502 [5].

[0226] UPF1 sends an N4 session modification response to confirm SMF1's request. If the old AMF has a PDU session with a different access type (different from the access type indicated in this procedure) and the old AMF determines that there is no possibility to relocate the N2 interface to the new AMF, the old AMF returns the UE's SUPI indicating that the registration request has been validated for integrity protection, but without the remaining UE context.

[0227] In the case of inter-PLMN mobility, the UE context information does not include the allowed NSSAI of the old PLMN, but includes the HPLMN S-NSSAI corresponding to the allowed NSSAI for each access type.

[0228] NOTE 4: The new AMF sets an indication that the UE is verified according to step 9a if the new AMF successfully authenticates the UE after a previous integrity check failed in the old AMF.

[0229] NOTE 5: The NF consumer does not need to re-subscribe to events in the new AMF after the UE has been successfully registered in the new AMF.

[0230] If the new AMF has already received the UE context from the old AMF during the handover procedure, steps 4, 5 and 10 are skipped.

[0231] In case of emergency registration, if the UE identifies itself with a 5G-GUTI not known to the AMF, steps 4 and 5 are skipped and the AMF immediately requests a SUPI from the UE. If the UE identifies itself with a PEI, the SUPI request is skipped. The permission of emergency registration without a User Identity depends on the local regulations.

[0232] Step 5. [Conditional] From old AMF to new AMF: Namf_Communication_UEContextTransfer(SUPI, response to AMF's UE Context (according to Table 5.2.2.2.2-1)) or UDSF to new AMF: Nudsf_Unstructured Data Management_Query(). The old AMF may start an implementation-specific (guard) timer for the UE context.

[0233] If the UDSF was queried in step 4, it responds to the new AMF with a Nudsf_Unstructured Data Management_Query call with the relevant context including the established PDU session, the old AMF contains the SMF information DNN, S-NSSAI and PDU session ID, active NGAP UE-TNLA binding to N3IWF / TNGF / W-AGF, the old AMF contains information about the NGAP UE-TNLA binding. If the old AMF was queried in step 4, it responds to the new AMF with a Namf_Communication_UEContextTransfer call by including the UE's SUPI and UE Context.

[0234] If the old AMF holds information about an established PDU session and it is not an initial registration, the old AMF contains the SMF information, DNN, S-NSSAI, and PDU session ID.

[0235] If the old AMF holds the UE context established via N3IWF, W-AGF, or TNGF, the old AMF contains the CM state via N3IWF, W-AGF, or TNGF. If the UE is in CM-CONNECTED state via N3IWF, W-AGF, or TNGF, the old AMF contains information about the NGAP UE-TNLA binding.

[0236] If the old AMF fails to check the integrity of the registration request NAS message, the old AMF indicates a failure of the integrity check. If the new AMF is configured to allow emergency services for unauthenticated UEs, the new AMF operates as follows: -If the UE only has an emergency PDU session, the AMF skips the authentication and security procedures or accepts that authentication may fail and continues with the mobility registration update procedure, or If the UE has both emergency and non-emergency PDU sessions and authentication fails, the AMF shall continue with the mobility registration update procedure and deactivate all non-emergency PDU sessions as specified in subclause 4.3.4.2.

[0237] NOTE 6: The new AMF can determine whether a PDU session is used for emergency services by checking whether the DNN matches the emergency DNN.

[0238] If the old AMF holds information about AM policy association and information about UE policy association (i.e., policy control request trigger to update UE policy defined in TS 23.503

[20] ), the old AMF contains information about AM policy association, UE policy association and PCF ID. In case of roaming, it contains V-PCF ID and H-PCF ID.

[0239] During inter-PLMN mobility, the handling of the UE Radio Capability ID in the new AMF is as defined in TS 23.501 [2].

[0240] The AMF1 sends a Reroute_N14_Request message to the NG-RAN containing the included AMF2 address (e.g., AMF2 IP address or FQDN) or / and the new 5G-GUTI and an N14 message container (Namf_Communication_UEContextTransfer Response). The Namf_Communication_UEContextTransfer Response contains the UE context.

[0241] When the NG-RAN receives the Reroute_N14_Request message, it sends a Reroute_N14_transfer message including an N14 message container (Namf_Communication_UEContextTransfer Response) to the AMF2. The Reroute_N14_transfer message (Namf_Communication_UEContextTransfer Response) including the N14 message container may include an AMF2 address or / and a new 5G-GUTI. If the new 5G-GUTI is configured in the NG-RAN, the AMF2 address is derived from the GUAMI part of the new 5G-GUTI when the Reroute_N14_Request message is received.

[0242] Step 5a. When the AMF1 receives the list IE of PDU sessions to be resumed in the Registration Request message of step 4 or based on local information, it sends a Nsmf_PDUSession_UpdateSMContext Request (Resume Request, PDU Session ID) to the SMF1.

[0243] Step 5b. SMF1 resumes the user plane for each PDU session by sending an N4 Session Change Request for each PDU session to UPF1. After resuming the user plane, UPF1 sends an N4 Session Change Response message to SMF1.

[0244] Step 5c. SMF1 sends a Nsmf_PDUSession_UpdateSMContext Response to AMF1. Please note that steps 10 to 12 in Figure 4A and Figure 4B are equivalent to steps 5 to 7 in Figure 4.8.2.3-1: Connection Resumption in CM-IDLE with Pause in 3GPP TS 23.502 [5].

[0245] Note 7: When the new AMF uses UDSF for context acquisition, the interaction between the old AMF, the new AMF and the UDSF due to UE signaling in the old AMF at the same time is an implementation issue.

[0246] Step 6. [Conditional] New AMF to UE: IdentityRequest(). If the SUCI is not provided by the UE and not obtained from the old AMF, the identity request procedure is initiated by the AMF sending an identity request message to the UE requesting the SUCI.

[0247] Step 7. [Conditional] UE to New AMF: ID response(). The UE responds with an Identity Response message containing the SUCI, which the UE derives using the HPLMN's provisioned public key as specified in TS 33.501

[15] .

[0248] Step 8. The AMF may decide to initiate UE authentication by invoking the AUSF. In that case, the AMF selects the AUSF based on the SUPI or SUCI as described in clause 6.3.4 of TS 23.501 [2]. If the AMF is configured to support emergency registration for unauthenticated SUPI and the UE indicates a registration type emergency registration, the AMF shall either skip the authentication or accept that authentication may fail and continue with the registration procedure.

[0249] Step 9a. If authentication is required, the AMF requests authentication from the AUSF. If the trace requirements for the UE are available in the AMF, the AMF provides the trace requirements in a request to the AUSF. Upon request from the AMF, the AUSF performs authentication of the UE. The authentication is performed as described in TS 33.501

[15] . The AUSF selects a UDM and gets the authentication data from the UDM as described in TS 23.501 [2], clause 6.3.8. Once the UE is authenticated, the AUSF provides relevant security-related information to the AMF. If the AMF provides a SUCI to the AUSF, the AUSF returns a SUPI to the AMF only after successful authentication. After successful authentication at the new AMF, triggered by a failed integrity check at the old AMF in step 5, the new AMF invokes step 4 above again and indicates that the UE has been verified (i.e. via the reason parameter specified in subclause 5.2.2.2.2).

[0250] Step 9b. If no NAS security context exists, NAS security initiation is performed as described in TS 33.501

[15] . If the UE did not have a NAS security context in step 1, the UE includes a complete registration request message as defined in TS 24.501

[25] . The AMF decides whether the registration request needs to be rerouted as described in section 4.2.2.2.3. The first AMF refers to the AMF.

[0251] Step 9c. If the 5G-AN has requested the UE context, the AMF initiates the NGAP procedure to provide the 5G-AN with the security context as specified in TS38.413

[10] . If the AMF also determines that EPS fallback is supported (e.g., based on the UE's capability to support the request type flag "handover" in the PDN connection request during the attach procedure, subscription data and local policy as defined in clause 5.17.2.3.1 of TS23.501[2]), the AMF sends an indication "Redirection for EPS fallback for voice is possible" to the 5G-AN as specified in TS38.413

[10] . Otherwise, the AMF indicates "Redirection for EPS fallback for voice is not possible". Furthermore, if tracing requirements for the UE are available in the AMF, the AMF provides the tracing requirements to the 5G-AN in the NGAP procedure.

[0252] Step 9d. The 5G-AN stores the security context and acknowledges to the AMF. The 5G-AN uses the security context to protect messages exchanged with the UE as described in TS 33.501

[15] .

[0253] Step 10. [Conditional] From new AMF to old AMF: Namf_Communication_RegistrationStatusUpdate (PDU Session ID is released since slicing is not supported). When the AMF is changed, the new AMF notifies the old AMF that the UE's registration to the new AMF is complete by calling the Namf_Communication_RegistrationStatusUpdate service operation. If the authentication / security procedures fail, the registration is rejected and the new AMF calls the Namf_Communication_RegistrationStatusUpdate service operation with a rejection indication to the old AMF. The old AMF continues as if the UE context transfer service operation was never received. If one or more S-NSSAIs used in the old registration area cannot provide service in the target registration area, the new AMF determines which PDU sessions cannot be supported in the new registration area. The new AMF invokes the Namf_Communication_RegistrationStatusUpdate service operation with the rejected PDU session IDs to the old AMF. The new AMF then changes the PDU session status accordingly. The old AMF informs the corresponding SMF to locally release the SM context of the UE by invoking the Nsmf_PDUSession_ReleaseSMContext service operation. If the new AMF receives information about the AMF policy association and the UE policy association in the UE context transfer in step 2 based on the local policy and without using the PCF identified by the PCF ID of the AM policy association and the UE policy association, then it informs the old AMF that the AM policy association and the UE policy association in the UE context are no longer used, and PCF selection is performed in step 15.

[0254] Step 11. [Conditional] New AMF to UE: Identity Request / Response (PEI). If the PEI was not provided by the UE or was not obtained from the old AMF, the identity request procedure is initiated by the AMF sending an identity request message to the UE to obtain the PEI. The PEI is transferred encrypted unless the UE performs an emergency registration and cannot be authenticated. In case of emergency registration, the UE may include the PEI in the registration request, in which case PEI acquisition is skipped. As indicated in the UE MM core network function, if the UE supports RACS, the AMF uses the UE's PEI to obtain the IMEI / TAC for the purpose of RACS operation.

[0255] Step 12. Optionally, the new AMF initiates an ME identity check by invoking the N5g-eir_EquipmentIdentityCheck_Get service operation (see Section 5.2.4.2.2). The PEI check is performed as described in Section 4.7. For emergency registration, if the PEI is blocked, operator policy determines whether to continue or stop the emergency registration procedure.

[0256] Step 13. If step 14 is performed, the new AMF selects a UDM based on the SUPI, and then the UDM can select a UDR instance, see clause 6.3.9 of TS 23.501 [2]. The AMF selects the UDM as described in clause 6.3.8 of TS 23.501 [2].

[0257] Steps 14a-c. If the AMF has changed since the last registration procedure, or if the UE provides a SUPI that does not reference a valid context in the AMF, or if the UE registers to the same AMF already registered to a non-3GPP access (i.e. the UE is registered via a non-3GPP access and initiates this registration procedure to add a 3GPP access), the new AMF registers to the UDM using Nudm_UECM_Registration for the access to which it is registered (and subscribes to be notified when the UDM deregisters this AMF).

[0258] The AMF provides the "Homogeneous Support of IMS Voice over PS Sessions" indication (see clause 5.16.3.3 of TS 23.501[2]) to the UDM. The "Homogenous Support of IMS Voice over PS Sessions" indication is not included unless the AMF has completed its evaluation of support for "IMS Voice over PS Sessions" as specified in clause 5.16.3.2 of TS 23.501[2].

[0259] During initial registration, if the AMF and UE support SRVCC from NG-RAN to UTRAN, the AMF provides the UE SRVCC capability to the UDM.

[0260] If the AMF determines that only the UE SRVCC capability has changed, the AMF sends the UE SRVCC capability to the UDM.

[0261] NOTE 8: At this step, it may be that the AMF does not have all the information required to decide the setting of the IMS Voice over PS Session Supported indication for this UE (see clause 5.16.3.2 of TS 23.501 [2]). Therefore, the AMF may send "Homogenous Support of IMS Voice over PS Sessions" later in this procedure.

[0262] If the AMF does not have the subscription data of the UE, the AMF uses Nudm_SDM_Get to obtain the access and mobility subscription data, the SMF selection subscription data, the UE context in the SMF data, and the LCS mobile origination. If the AMF already has the subscription data of the UE, but the SoR update indication in the UE context requires the AMF to obtain the SoR information depending on the NAS registration type ("initial registration" or "emergency registration") (see Annex C of TS 23.122

[22] ), the AMF uses Nudm_SDM_Get to obtain the roaming steering information. This requires that the UDM can obtain this information from the UDR by Nudr_DM_Query. After receiving a successful response, the AMF subscribes to be notified using Nudm_SDM_Subscribe when the requested data changes, and the UDM can subscribe to the UDR by Nudr_DM_Subscribe. If the GPSI is available in the subscription data of the UE, the GPSI is provided to the AMF in the access and mobility subscription data from the UDM. The UDM may provide an indication that subscription data for network slicing has been updated for the UE. If the UE subscribes to MPS in the serving PLMN, "MPS priority" is included in the access and mobility subscription data provided to the AMF. If the UE subscribes to MCX in the serving PLMN, "MCX priority" is included in the access and mobility subscription data provided to the AMF. The UDM also provides an indication of IAB-Operation allowed to the AMF as part of the access and mobility subscription data. The AMF triggers the setup of the UE context in the NG-RAN, or, if the initial setup is in step 9c, a change in the UE context in the NG-RAN, including an indication that the IAB node is allowed.

[0263] The new AMF provides the UDM with the access type to be provided to the UE, and the access type is set to "3GPP access". The UDM stores the associated access type together with the serving AMF and does not delete the AMF IDs associated with other access types, if any. The UDM may store the information provided by Nudr_DM_Update during AMF registration in the UDR.

[0264] If the UE is registered with the old AMF for access and the old AMF and new AMF are in the same PLMN, the new AMF shall send a separate / independent Nudm_UECM_Registration to update the UDM with the access type set to the access used by the old AMF after the relocation of the old AMF is completed successfully.

[0265] The new AMF creates a UE context for the UE after getting the access and mobility subscription data from the UDM. The access and mobility subscription data includes whether the UE is allowed to include the NSSAI in the 3GPP access RRC connection establishment in clear text. The access and mobility subscription data may include Enhanced Coverage Restricted information. If received from the UDM and the UE included support for restricted use of enhanced coverage in step 1, the AMF determines whether the extended coverage is restricted for the UE as specified in clause 5.31.12 of TS 23.501 [2] and stores the updated restricted information of the extended coverage in the UE context.

[0266] The access and mobility subscription data may include NB-IoT UE priority.

[0267] The subscription data may include a service gap time parameter. If received from the UDM, the AMF stores this service gap time for the UE in its UE Context.

[0268] In the case of an emergency registration where the UE is not successfully authenticated, the AMF does not register with the UDM.

[0269] The AMF enforces the mobility restrictions as specified in clause 5.3.4.1.1 of TS 23.501[2]. In case of emergency registration, the AMF does not check mobility restrictions, access restrictions, regional restrictions, or subscription restrictions. In case of emergency registration, the AMF ignores the failed registration response from the UDM and continues the registration procedure.

[0270] NOTE 9: The AMF may use the Nudm_SDM_Subscribe service operation with immediate report indication to trigger the UDM to immediately return the subscribed data instead of the Nudm_SDM_Get service operation if the corresponding functionality is supported by both the AMF and the UDM.

[0271] Step 14d. When the UDM stores the associated access type (e.g. 3GPP) with the serving AMF as indicated in step 14a, this causes the UDM to initiate Nudm_UECM_DeregistrationNotification (see section 5.2.3.2.2) to the old AMF corresponding to the same (e.g. 3GPP) access, if any. If the timer started in step 5 is not running, the old AMF may delete the UE context of the same access type. Otherwise, the AMF may delete the UE context of the same access type when the timer expires. If the serving NF deletion reason indicated by the UDM is initial registration, the old AMF invokes the Nsmf_PDUSession_ReleaseSMContext(SM context ID) service operation to all associated SMFs of the UE to notify that the UE has been deregistered from the old AMF of the same access type, as described in section 4.2.2.3.2. The SMF releases the PDU session upon receiving this notification.

[0272] If the old AMF has established an AM policy association and a UE policy association with the PCF and the old AMF did not transfer the PCF identity to the new AMF (e.g. the new AMF is in a different PLMN), the old AMF performs an AMF initiated policy association termination procedure as defined in subclause 4.16.3.2 and an AMF initiated UE policy association termination procedure as defined in subclause 4.16.13.1. Furthermore, if the old AMF transferred the PCF identity in the UE context but the new AMF indicated in step 10 that the AM policy association information and the UE policy association information in the UE context are not used, then the old AMF performs an AMF initiated policy association termination procedure as defined in subclause 4.16.3.2 and an AMF initiated UE policy association termination procedure as defined in subclause 4.16.13.1.

[0273] If the old AMF has an N2 connection for the UE (e.g. because the UE was in RRC Inactive state and has now moved to E-UTRAN or to an area not served by the old AMF), the old AMF shall perform an AN release (see section 4.2.6) with a cause value indicating that the UE has already released the NG-RAN RRC connection locally.

[0274] Step 14e. [Conditional] If the old AMF does not have a UE context of another access type (i.e., non-3GPP access), the old AMF unsubscribes the UDM for subscription data using Nudm_SDM_unsubscribe.

[0275] Step 15. If the AMF decides to initiate PCF communication, the AMF acts as follows: If the new AMF decides to use the (V-)PCF identified by the (V-)PCF ID included in the UE context from the old AMF in step 5, the AMF contacts the (V-)PCF identified by the (V-)PCF ID to obtain policies. If the AMF decides to perform PCF discovery and selection, and the AMF selects a (V)-PCF and potentially an H-PCF (for roaming scenarios) as described in TS 23.501 [2], it follows the V-NRF and H-NRF interactions described in clauses 6.3.7.1 and 4.3.2.2.3.3.

[0276] Step 16. [Optional] The new AMF performs AM policy association establishment / modification. In case of emergency registration, this step is skipped. If the new AMF selects a new (V-)PCF in step 15, the new AMF performs the establishment of an AM policy association with the selected (V-)PCF as defined in subclause 4.16.1.2. If the (V-)PCF identified by the (V-)PCF ID included in the UE context from the old AMF is used, the new AMF performs the change of the (V-)PCF and AM policy association as defined in subclause 4.16.2.1.2. When the AMF informs the PCF of mobility restrictions (e.g. UE location) for adjustment or when the PCF updates the mobility restrictions itself due to some condition (e.g. application in use, date and time), the PCF provides the updated mobility restrictions to the AMF. If the subscription information includes tracing requirements, the AMF provides the tracing requirements to the PCF. If the AMF supports DNN substitution, the AMF shall provide the PCF with the allowed NSSAI and, if available, a mapping of the allowed NSSAI. If the PCF supports DNN replacement, the PCF provides a trigger for DNN replacement to the AMF.

[0277] Step 17. [Conditional] AMF to SMF: Nsmf_PDUSession_UpdateSMContext(). For an emergency registered UE (see TS 23.501 [2]), this step applies if the registration type is mobility registration update.

[0278] AMF calls Nsmf_PDUSession_UpdateSMContext (see Section 5.2.8.2.6) in the following scenarios: - If the registration request of step 1 includes a list of PDU sessions to be activated, the AMF sends a Nsmf_PDUSession_UpdateSMContext request to the SMF associated with the PDU sessions to activate the user plane connections of these PDU sessions. Steps from step 5 onwards described in subclause 4.2.3.2 are executed to complete the activation of the user lane connection without sending RRC Inactive Assistance Information and without sending an MM NAS Service Accept from the AMF to the (R)AN described in step 12 of subclause 4.2.3.2. When the user plane connections of the PDU sessions are activated, the AS layer of the UE informs the NAS layer of it.

[0279] If in step 3 the AMF determines that the UE is performing Inter-RAT mobility to or from NB-IoT, it sends a Nsmf_PDUSession_UpdateSMContext request to the SMF associated with the UE's PDU sessions so that the SMF can update them according to the "PDU Session Continuity in Inter-RAT Mobility" subscription data. The steps from step 5 onwards described in subclause 4.2.3.2 are performed without sending a MM NAS service accept from the AMF to the (R)AN described in step 12 of subclause 4.2.3.2.

[0280] When the serving AMF is changed, the new serving AMF informs the SMFs of each PDU session that it has taken over responsibility for the signaling path to the UE, and the new serving AMF invokes the Nsmf_PDUSession_UpdateSMContext service operation using the SMF information received from the old AMF in step 5. It also indicates whether to reactivate the PDU session.

[0281] NOTE 10: When the UE moves to another PLMN, the AMF of the serving PLMN may insert or change the V-SMF in the serving PLMN of the Home Routed PDU session. In this case, the same procedures as described in subclause 4.23.3 apply for the change of the V-SMF as for the change of the I-SMF (i.e. by replacing the I-SMF with the V-SMF). During the change between PLMNs, if the same SMF is used, session continuity can be supported depending on the operator policy.

[0282] The steps listed in Section 4.2.3.2 starting from step 5 are executed. If an intermediate UPF insertion, deletion, or modification is performed for a PDU session that is not included in the "PDU session to be reactivated", this procedure is performed without interaction of N11 and N2 to update the N3 user plane between the (R)AN and the 5GC.

[0283] AMF invokes the Nsmf_PDUSession_ReleaseSMContext service operation to SMF in the following scenarios: -If any PDU session status indicates that it has been released at the UE, the AMF invokes the Nsmf_PDUSession_ReleaseSMContext service operation to the SMF to release network resources related to the PDU session.

[0284] If the serving AMF has changed, the new AMF waits until step 18 is completed in all SMFs associated with the UE. Otherwise, steps 19 to 22 can continue in parallel with this step.

[0285] Step 18. [Conditional] If the new AMF and the old AMF are in the same PLMN, the new AMF sends a UE context modification request to the N3IWF / TNGF / W-AGF as specified in TS 29.413

[64] .

[0286] When the AMF is changed and the old AMF indicates that the UE is in CM-CONNECTED state via the N3IWF, W-AGF, or TNGF, and if the new AMF and the old AMF are in the same PLMN, the new AMF creates an NGAP UE association to the N3IWF / TNGF / W-AGF to which the UE is connected, which automatically releases the existing NGAP UE association between the old AMF and the N3IWF / TNGF / W-AGF.

[0287] Step 19. The N3IWF / TNGF / W-AGF sends a UE context modification response to the new AMF.

[0288] Step 19a. [Conditional] After the new AMF receives a response message from the N3IWF, W-AGF, or TNGF in step 19, the new AMF registers to the UDM using Nudm_UECM_Registration as step 14a, but with the access type set to "non-3GPP access". The UDM stores the associated access type with the serving AMF and does not delete the AMFID, if any, associated with other access types. The UDM may store the information provided by Nudr_DM_Update during AMF registration in the UDR.

[0289] Step 19b. [Conditional] When the UDM stores the associated access type (i.e. non-3GPP) with the serving AMF as shown in step 19a, this causes the UDM to initiate a Nudm_UECM_DeregistrationNotification (see section 5.2.3.2.2) to the old AMF corresponding to the same (i.e. non-3GPP) access. The old AMF deletes the UE context of the non-3GPP access.

[0290] Step 19c. The old AMF unsubscribes from the UDM for subscription data using Nudm_SDM_unsubscribe.

[0291] Step 20a. Void.

[0292] Step 21. New AMF to UE: Registration Accept (5G-GUTI, Registration Area, Mobility Restriction, PDU Session Status, Allowed NSSAI, Allowed NSSAI Mapping, Configured NSSAI in Serving PLMN, Configured NSSAI Mapping, Rejected S-NSSAI, Pending NSSAI, Pending NSSAI Mapping, Periodic Registration Update Timer, Active Time, Strict Periodic Registration Timer Indication, LADN Information, Accepted MICO Mode, IMS Voice over , [Supported Indication for PS Sessions], [Emergency Service Support Indication], [Accepted DRX Parameters for E-UTRA and NR], [Accepted DRX Parameters for NB-IoT], [Extended Idle Mode DRX Parameters], [Paging Time Window], [Network Support for Interworking without N26], [Access Stratum Connection Establishment NSSAI Inclusion Mode], [Network Slicing Subscription Change Indication], [Operator Defined Access Category Definition], [List of Equivalent PLMNs], [Extended Coverage Restriction Information], [Supported Network Behavior], [Service Gap Time], [UE Radio Capability ID for PLMN Allocation], [Removal of UE Radio Capability ID for PLMN Allocation], [WUS Assistance [Information], [Shortened 5G-S-TMSI Configuration]).

[0293] If the requested NSSAI does not contain an S-NSSAI that maps to an S-NSSAI of the HPLMN that is subject to network slice specific authentication and authorization and the AMF determines that it cannot provide an S-NSSAI for the UE's authorized NSSAIs in the current UE tracking area, and if no default S-NSSAIs that have not yet been involved in the current UE registration procedure are further considered, the AMF shall reject the UE registration and shall include in the rejection message the list of rejected S-NSSAIs, each with an appropriate rejection reason value.

[0294] The allowed NSSAIs of the UE's access type are included in the N2 message carrying the Registration Accept message. The allowed NSSAIs include S-NSSAIs that do not require network slice specific authentication and authorization based on subscription information, and S-NSSAIs that are network slice specific authentication and authorization based on the UE context of the AMF and have been previously successful regardless of the access type. The mapping of pending NSSAIs is to map each S-NSSAI of the pending NSSAIs of the serving PLMN to the HPLMN S-NSSAI.

[0295] If the UE indicated support for network slice specific authentication and authorization procedures in the UE MM core network function in the registration request, the AMF includes in the pending NSSAI the S-NSSAIs that map to the S-NSSAIs of the HPLMNs that are indicated in the subscription information to be subject to network slice specific authentication and authorization as described in clause 4.6.2.4 of TS 24.501

[25] . In such a case, the AMF shall trigger in step 25 the network slice specific authentication and authorization procedures as specified in clause 4.2.9.2 for the S-NSSAIs that require network slice specific authentication and authorization that have already been initiated with another access type for the same S-NSSAI, except based on the network policy. The UE shall not attempt to re-register to an S-NSSAI included in the list of pending NSSAIs until the network slice specific authentication and authorization procedures are completed, regardless of the access type.

[0296] If the UE does not indicate support for network slice specific authentication and authorization procedures in the UE 5GMM core network functions in the registration request and the requested NSSAI includes S-NSSAIs that are mapped to HPLMN S-NSSAIs that are subject to network slice specific authentication and authorization, the AMF shall include those S-NSSAIs in the requested NSSAI in the rejected S-NSSAI.

[0297] The reasons why an S-NSSAI cannot be designated an permitted NSSAI include: -All S-NSSAIs within the requested NSSAI are subject to network slice-specific authentication and authorization, or - If a requested NSSAI was not provided or an S-NSSAI in the requested NSSAI does not match any subscribed S-NSSAI, all S-NSSAIs marked as default in the subscribed S-NSSAI are subject to network slice-specific authentication and authorization.

[0298] The AMF provides an empty authorized NSSAI. Upon receiving an empty authorized NSSAI and a pending NSSAI, the UE registers with the PLMN but does not attempt to use any services offered by the PLMN upon access, e.g., except for emergency services (see TS 24.501

[25] ), until the UE receives an authorized NSSAI and must wait for the completion of network slice specific authentication and authorization procedures.

[0299] The AMF stores the NB-IoT Priority obtained in step 14 and associates it with the 5G-S-TMSI assigned to the UE.

[0300] The AMF sends a Registration Accept message to the UE indicating that the registration request has been accepted. If the AMF assigns a new 5G-GUTI, the 5G-GUTI is included. Upon receiving a Registration Request message of type "Initial Registration" or "Mobility Registration Update" from the UE, the AMF MUST include the new 5G-GUTI in the Registration Accept message. Upon receiving a Registration Request message of type "Periodic Registration Update" from the UE, the AMF MUST include the new 5G-GUTI in the Registration Accept message. If the UE is already in RM-REGISTERED state via another access in the same PLMN, the UE shall use the 5G-GUTI received in the Registration Accept for both registrations. If the Registration Accept does not include the 5G-GUTI, the UE shall use the 5G-GUTI assigned to the existing registration for the new registration as well. If the AMF assigns a new registration area, the AMF shall send the registration area to the UE via the Registration Accept message. If the Registration Accept message does not include a registration area, the UE shall consider the old registration area to be valid. If mobility restrictions apply to the UE and the registration type is not emergency registration, the mobility restrictions are included. The AMF informs the UE of the established PDU sessions in the PDU session status. The UE locally deletes the internal resources related to the PDU sessions that are not marked as established in the received PDU session status. If the AMF calls the Nsmf_PDUSession_UpdateSMContext procedure for UP activation of the PDU session in step 18 and receives a rejection from the SMF, the AMF informs the UE of the PDU session ID and the reason why the user plane resources were not activated. If the UE is connected to two AMFs belonging to different PLMNs via 3GPP access and non-3GPP access, the UE locally deletes the internal resources related to the PDU sessions of the current PLMN that are not marked as established in the received PDU session status. If the PDU session status information was included in the registration request, the AMF indicates the PDU session status to the UE.

[0301] If the RAT type is NB-IoT and the network is configured to use the control plane relocation indication procedure, the AMF shall include in the registration accept message a truncated 5G-S-TMSI configuration to be used by the UE using control plane CIoT 5GS optimization to create a truncated 5G-S-TMSI, see clause 5.31.4.3 of TS 23.501[2].

[0302] The allowed NSSAIs provided in the registration grant are valid in the registration area and apply to all PLMNs whose tracking area is included in the registration area. The mapping of allowed NSSAIs is the mapping of each S-NSSAI of the allowed NSSAI to the HPLMN S-NSSAI. The mapping of configured NSSAIs is the mapping of each S-NSSAI of the configured NSSAI of the serving PLMN to the HPLMN S-NSSAI.

[0303] The AMF shall include in the registration accept message the LADN information, which is the list of LADNs available within the registration area determined by the AMF for the UE, as described in clause 5.6.5 of TS 23.501 [2]. The AMF shall include the operator-defined access category definitions, as described in TS 24.501

[25] , to allow the UE to determine the applicable operator-specific access category definitions.

[0304] If the UE included the MICO mode in the Registration Request, the AMF responds in the Registration Accept message whether to use the MICO mode. If the MICO mode is allowed for the UE, the AMF may include an active time value and / or a strictly periodic registration timer indication in the Registration Accept message. The AMF determines the periodic registration update timer value, the active time value and the strictly periodic registration timer indication based on local configuration, expected UE behavior if available, UE indicated preferences, UE capabilities, UE subscription information and network policies, or any combination thereof, to enable UE power saving, as described in clause 5.31.7 of TS 23.501 [2]. If the UE indicated the capability of strictly periodic registration timer indication in the Registration Request message, as described in step 1, the AMF decides to apply the strictly periodic registration timer indication to the UE. If the AMF provides the UE with a periodic registration update timer value together with a strict periodic registration timer indication, the UE and the AMF start the periodic registration update timer after this step as described in clause 5.31.7.5 of TS 23.501 [2].

[0305] In case of registration via 3GPP access, the AMF sets the IMS Voice over PS session support indication as described in clause 5.16.3.2 of TS 23.501 [2]. To set the IMS Voice over PS session support indication, the AMF may need to check the compatibility of the UE and NG-RAN radio capabilities related to IMS Voice over PS by performing the UE Capability Match Request procedure in clause 4.2.8a. If the AMF does not receive a voice support match indication from the NG-RAN on time, based on the implementation, the AMF may set the IMS Voice over PS session support indication and update it at a later stage.

[0306] In case of registration via non-3GPP access, the AMF sets the IMS Voice over PS session support indication as described in clause 5.16.3.2a of TS 23.501 [2].

[0307] The emergency service support indication informs the UE that emergency services are supported, i.e. the UE can request an emergency service PDU session. If the AMF receives "MPS priority" from the UDM as part of the access and mobility subscription data based on the operator policy, the "MPS priority" is included in the registration accept message to the UE to inform the UE whether the configuration of Access Identity 1 is valid in the selected PLMN as specified in TS 24.501

[25] . If the AMF receives "MCX priority" from the UDM as part of the access and mobility subscription data based on the operator policy and the UE subscription to MCX services, the "MCX priority" is included in the registration accept message to the UE to inform the UE whether the configuration of Access Identity 2 is valid in the selected PLMN as specified in TS 24.501

[25] . The accepted DRX parameters are defined in clause 5.4.5 of TS 23.501 [2]. If the UE included the NB-IoT requested DRX parameters in the registration request message, the AMF includes the NB-IoT accepted DRX parameters. The AMF configures the network support for interworking without N26 parameters as described in clause 5.17.2.3.1 of TS 23.501 [2]. If the AMF accepts the use of extended idle mode DRX, the AMF includes the extended idle mode DRX parameters and the paging time window as described in clause 5.31.7.2 of TS 23.501 [2].

[0308] A network slicing subscription change indication is included if the UDM is intended to indicate to the UE that the subscription has changed. If the AMF contains a network slicing subscription change indication, the UE shall locally clear all network slicing configurations for all PLMNs and, if applicable, update the current PLMN configurations based on the received information.

[0309] The Access Stratum Connection Establishment NSSAI Inclusion Mode specified in clause 5.15.9 of TS 23.501[2] is included to indicate to the UE which NSSAI, if any, to include in the Access Stratum Connection Establishment. The AMF can set the values ​​for operation modes a, b, c defined in clause 5.15.9 of TS 23.501[2] for 3GPP access only if the RRC Connection Establishment Allowed indicates that it is allowed by including the NSSAI.

[0310] For a UE registered in a PLMN, the AMF may provide a list of equivalent PLMNs to be processed as specified in TS 24.501

[25] . For a UE registered in a SNPN, the AMF does not provide the UE with a list of equivalent PLMNs.

[0311] If the UE included support for enhanced coverage usage restriction in step 1, the AMF sends the enhanced coverage restriction information to the NG-RAN in the N2 message. The AMF also sends the Enhanced Coverage Restricted information to the UE in the Registration Accept message.

[0312] If the UE receives the extended coverage restriction information in the registration accept message, the UE stores this information and uses the value of the extended coverage restriction information to determine whether to use the extended coverage function.

[0313] If the UE and the AMF negotiate to enable the MICO mode and the AMF uses the Extended Connected Timer, the AMF provides the Extended Connected Time value to the NG-RAN in this step (see clause 5.31.7.3 of TS 23.501 [2]). The Extended Connected Time value indicates the minimum time the RAN shall keep the UE in RRC-CONNECTED state regardless of inactivity.

[0314] If the UE includes a preferred network behavior in its registration request, the AMF indicates the supported and accepted CIoT 5GS optimizations in the supported network behavior information (see clause 5.31.2 of TS 23.501 [2]).

[0315] The AMF may operate the UE out of 5GC by rejecting the registration request. Before operating the UE out of 5GC, the AMF must consider the preferred and supported network behavior (see clause 5.31.2 of TS 23.501[2]) and the availability of EPC to the UE.

[0316] If the AMF accepts the MICO mode and is aware that there may be mobile terminated data or pending signaling, the AMF shall maintain the N2 connection for at least the extended connection time and provide the value of the extended connection time to the RAN, as described in clause 5.31.7.3 of TS 23.501[2].

[0317] If the Service Gap Time is present in the subscription information (steps 14a to 14c) or if the Service Gap Time is updated by the subscription information update notification procedure to the AMF (see section 4.5.1) and the UE has indicated UE service gap control capability, the AMF includes the Service Gap Time.

[0318] If the UE receives a Service Gap Time in the Registration Accept message, the UE shall store this parameter and apply the Service Gap Control (see clause 5.31.16 of TS 23.501[2]).

[0319] If the network supports WUS grouping (see TS 23.501[2]), the AMF sends WUS assistance information to the UE. If the UE provides UE paging probability information in step 1, the AMF takes it into account when determining the WUS assistance information.

[0320] If the UE and AMF support RACS as defined in clause 5.4.4.1a of TS 23.501 [2], the AMF must configure the UE with a UE Radio Capability ID, and the AMF already has a UE radio capability other than the NB-IoT radio capability of the UE, the AMF may provide the UE Radio Capability ID of the UE radio capability to the UE, which the UCMF returns in the Nucmf_assign service operation for this UE. Alternatively, if the UE and AMF support RACS, the AMF may provide an indication to the UE to delete the UE Radio Capability ID of the PLMN assignment within this PLMN (see clause 5.4.4.1a of TS 23.501 [2]).

[0321] If the UE is "CAG supported" and the AMF needs to update the UE's CAG information, the AMF may include the CAG information as part of the mobility restriction in the registration accept message.

[0322] Step 21b. [Optional] The new AMF performs UE policy association establishment as defined in clause 4.16.11. In case of emergency registration, this step is skipped. The new AMF sends an Npcf_UEPolicyControl Create Request to the PCF. The PCF sends an Npcf_UEPolicyControl Create Response to the new AMF. The PCF triggers the UE Configuration Update Procedure as defined in subclause 4.2.4.3.

[0323] Step 22. [Conditional] UE to New AMF: Registration complete(). After receiving the Configured NSSAI for the Serving PLMN, the Mapping Of Configured NSSAI, and either the Network Slicing Subscription Change Indication or the CAG information in step 21, if the UE successfully updates itself, the UE sends a Registration Complete message to the AMF.

[0324] The UE sends a registration complete message to the AMF to check whether a new 5G-GUTI has been assigned.

[0325] If a new 5G-GUTI is assigned, the UE passes the new 5G-GUTI to the lower layers of the 3GPP access when the lower layers (3GPP access or non-3GPP access) indicate to the RM layer of the UE that the registration complete message has been successfully transferred over the air interface.

[0326] NOTE 11: The above is necessary because the NG-RAN may use the RRC Inactive state and part of the 5G-GUTI is used to calculate the Paging Frame (see TS 38.304

[44] and TS 36.304

[43] ). It is assumed that the Registration Complete is delivered reliably to the AMF after the 5G-AN has confirmed its reception by the UE.

[0327] If the List Of PDU Sessions To Be Activated is not included in the Registration Request and the Registration procedure was not started in the CM-CONNECTED state, the AMF shall release the signaling connection with the UE according to clause 4.2.6.

[0328] If a follow-on request is included in the registration request, the AMF should not release the signaling connection after the registration procedure is completed.

[0329] If the AMF is aware that some signaling is pending within the AMF or between the UE and the 5GC, the AMF should not release the signaling connection immediately after completion of the registration procedure.

[0330] In step 21, if a PLMN-assigned UE Radio Capability ID is included, upon receiving the registration complete message, the AMF stores the PLMN-assigned UE Radio Capability ID in the UE context.

[0331] If the UE receives the PLMN assigned UE radio capability ID deletion indication in step 21, the UE deletes the PLMN assigned UE radio capability ID for this PLMN.

[0332] Step 23. [Conditional] AMF to UDM: If the access and mobility subscription data provided by the UDM to the AMF in 14b includes a roaming information manipulation indicating that the UDM requests an acknowledgement of receipt of this information from the UE, the AMF provides the UE's acknowledgement to the UDM using Nudm_SDM_Info. For further details on roaming information manipulation, see TS 23.122

[22] .

[0333] Step 23a. Upon registration via 3GPP access, if the AMF does not release the signaling connection, the AMF sends RRC Inactive Assistance Information to the NG-RAN. In the case of registration via non-3GPP access, if the UE is also in CM-CONNECTED state in 3GPP access, the AMF sends RRC inactive assistance information to the NG-RAN. The AMF also uses the Nudm_SDM_Info service operation to provide an acknowledgement to the UDM that the UE has received and acted upon the CAG information or network slicing subscription change indication (see steps 21 and 22).

[0334] Step 24. [Conditional] AMF to UDM: After step 14a, in parallel with any of the previous steps, the AMF sends a "Homogeneous support for IMS Voice over PS sessions" indication to the UDM using Nudm_UECM_Update. - If the AMF is evaluating support for IMS Voice over PS sessions, see clause 5.16.3.2 of TS 23.501 [2]. - If the AMF determines that it is necessary to update the homogeneous support for IMS Voice over PS sessions, refer to clause 5.16.3.3 of TS 23.501 [2].

[0335] Step 25. [Conditional] If the UE indicates support for network slice specific authentication and authorization procedures in the UE MM Core Network Function in the Registration Request and the S-NSSAI in the HPLMN is subject to network slice specific authentication and authorization, the relevant procedures are performed in this step (see Section 4.2.9.1). Once the network slice specific authentication and authorization procedures are completed for all S-NSSAIs, the AMF triggers the UE Configuration Update procedure to deliver the allowed NSSAIs, including also the S-NSSAIs for which the network slice specific authentication and authorization was successful, and includes the rejected NSSAIs with the appropriate rejection reason value.

[0336] Due to pending network slice-specific authentication and authorization, the AMF removes the mobility restriction if the Tracking Areas of the registration area were previously assigned as Non-Allowed Areas.

[0337] The AMF stores in the UE context an indication for any S-NSSAI of the HPLMN that is subject to network slice specific authentication and authorization for which network slice specific authentication and authorization was successful.

[0338] Upon completion of the network slice specific authentication and authorization procedures, if the AMF determines that an S-NSSAI already authenticated and authorized by the PLMN cannot be provided in the UE's allowed NSSAIs and if a default S-NSSAI cannot be further considered, the AMF shall perform the network-initiated deregistration procedure described in subclause 4.2.2.3.3, where the explicit deregistration request message includes a list of rejected S-NSSAIs, each with an appropriate rejection reason value.

[0339] Mobility related event notifications to NF consumers are triggered at the end of this procedure for the cases described in subclause 4.15.4. (List of Abbreviations)

[0340] For the purposes of this document, the abbreviations defined in 3GPP TR21.905[1] and shown below apply. Abbreviations defined in this document take precedence over those defined in 3GPP TR21.905[1].

[0341] 4G-GUTI 4G Globally Unique Temporary UE Identity 5GC 5G Core Network 5GLAN 5G Local Area Network 5GS 5G System 5G-AN 5G Access Network 5G-AN PDB 5G Access Network Packet Delay Budget 5G-EIR 5G-Equipment Identity Register 5G-GUTI 5G Globally Unique Temporary Identifier 5G-BRG 5G Broadband Residential Gateway 5G-CRG 5G Cable Residential Gateway 5G GM 5G Grand Master 5G-RG 5G Residential Gateway 5G-S-TMSI 5G S-Temporary Mobile Subscription Identifier 5G VN 5G Virtual Network 5QI 5G QoS Identifier AF Application Function AMF Access and Mobility Management Function AS Access Stratum ATSSS Access Traffic Steering, Switching, Splitting ATSSS-LL ATSSS Low-Layer AUSF Authentication Server Function AUTN Authentication token BMCA Best Master Clock Algorithm BSF Binding Support Function CAG Closed Access Group CAPIF Common API Framework for 3GPP northbound APIs CHF Charging Function CN PDB Core Network Packet Delay Budget CP Control Plane DAPS Dual Active Protocol Stacks DL Downlink DN Data Network DNAI DN Access Identifier DNN Data Network Name DRX Discontinuous Reception DS-TT Device-side TSN translator ePDG evolved Packet Data Gateway EBI EPS Bearer Identity EPS Evolved Packet System EUI Extended Unique Identifier FAR Forwarding Action Rule FN-BRG Fixed Network Broadband RG FN-CRG Fixed Network Cable RG FN-RG Fixed Network RG FQDN Fully Qualified Domain Name GFBR Guaranteed Flow Bit Rate GMLC Gateway Mobile Location Centre GPSI Generic Public Subscription Identifier GUAMI Globally Unique AMF Identifier GUTI Globally Unique Temporary UE Identity HR Home Routed (roaming) IAB Integrated access and backhaul IMEI / TAC IMEI Type Allocation Code IPUPS Inter PLMN UP Security I-SMF Intermediate SMF I-UPF Intermediate UPF LADN Local Area Data Network LBO Local Break Out (roaming) LMF Location Management Function LoA Level of Automation LPP LTE Positioning Protocol LRF Location Retrieval Function MCC Mobile country code MCX Mission Critical Service MDBV Maximum Data Burst Volume MFBR Maximum Flow Bit Rate MICO Mobile Initiated Connection Only MITM Man In the Middle MNC Mobile Network Code MPS Multimedia Priority Service MPTCP Multi-Path TCP Protocol N3IWF Non-3GPP InterWorking Function N5CW Non-5G-Capable over WLAN NAI Network Access Identifier NAPT Network Address Port Translation NAT Network Address TranslationNEF Network Exposure Function NF Network Function NGAP Next Generation Application Protocol NID Network identifier NPN Non-Public Network NR New Radio NRF Network Repository Function NSI ID Network Slice Instance Identifier NSSAA Network Slice-Specific Authentication and Authorization NSSAAF Network Slice-Specific Authentication and Authorization Function NSSAI Network Slice Selection Assistance Information NSSF Network Slice Selection Function NSSP Network Slice Selection Policy NW-TT Network-side TSN translator NWDAF Network Data Analytics Function PCF Policy Control Function PDB Packet Delay Budget PDR Packet Detection Rule PDU Protocol Data Unit PEI Permanent Equipment Identifier PER Packet Error Rate PFD Packet Flow Description PNI-NPN Public Network Integrated Non-Public Network PPD Paging Policy Differentiation PPF Paging Proceed Flag PPI Paging Policy Indicator PSA PDU Session Anchor PTP Precision Time Protocol QFI QoS Flow Identifier QoE Quality of Experience RACS Radio Capabilities Signalling optimization (R)AN (Radio) Access Network RG Residential Gateway RIM Remote Interference Management RQA Reflective QoS Attribute RQI Reflective QoS Indication RSN Redundancy Sequence Number SA NR Standalone New Radio SBA Service Based Architecture SBI Service Based Interface SCP Service Communication Proxy SD Slice Differentiator SEAF Security Anchor Functionality SEPP Security Edge Protection Proxy SMF Session Management Function SMSF Short Message Service Function SN Sequence Number SN name Serving Network Name SNPN Stand-alone Non-Public Network S-NSSAI Single Network Slice Selection Assistance Information SSC Session and Service Continuity SSCMSP Session and Service Continuity Mode Selection Policy SST Slice / Service Type SUCI Subscription Concealed Identifier SUPI Subscription Permanent Identifier SV Software Version TMSI Temporary Mobile Subscriber Identity TNAN Trusted Non-3GPP Access Network TNAP Trusted Non-3GPP Access Point TNGF Trusted Non-3GPP Gateway Function TNL Transport Network Layer TNLA Transport Network Layer Association TSC Time Sensitive Communication TSCAI TSC Assistance Information TSN Time Sensitive Networking TSN GM TSN Grand Master TSP Traffic Steering Policy TT TSN Translator TWIF Trusted WLAN Interworking Function UCMF UE radio Capability Management Function UDM Unified Data Management UDR Unified Data Repository UDSF Unstructured Data Storage Function UL Uplink UL CL Uplink Classifier UPF User Plane Function URLLC Ultra Reliable Low Latency Communication URRP-AMF UE Reachability Request Parameter for AMF URSP UE Route Selection Policy VID VLAN Identifier VLAN Virtual Local Area Network W-5GAN Wireline 5G Access Network W-5GBAN Wireline BBF Access Network W-5GCAN Wireline 5G Cable Access Network W-AGF Wireline Access Gateway Function (definition)

[0342] For the purposes of this document, the terms and definitions set forth in 3GPP TR21.905[1] and below apply. Terms defined in this document take precedence over those defined in 3GPP TR21.905[1]. (References list)

[0343] [1] 3GPP TR 21.905: "Vocabulary for 3GPP Specifications". V16.0.0 (2019-06) [2] GSM Association Official Document NG.116: “Generic Network Slice Template” V2.0 (2019-10) [3] 3GPP TR 22.835: "Study on Enhanced Access to and Support of Network Slices" V0.2.0 (2020-11) [4] 3GPP TS 23.501: "System architecture for the 5G System (5GS)". V16.7.0 (2020-12) [5] 3GPP TS 23.502: "Procedures for the 5G System (5GS)". V16.7.0 (2020-12) [6] 3GPP TS 38.413: "NG Application Protocol (NGAP)". V16.4.0 (2021-01) [7] 3GPP TS 23.003: "Numbering, addressing and identification". V17.0.0 (2020-12)

[0344] Although the present invention has been described above with reference to the embodiment, the present invention is not limited to the above embodiment. Various modifications that can be understood by those skilled in the art can be made to the configuration and details of the present invention within the scope of the invention.

[0345] This application is based on Indian Patent Application No. 202111005728 filed on February 10, 2021, the disclosure of which is incorporated herein by reference in its entirety.

Claims

1. receiving a registration request from a Radio Access Network (RAN); determining whether a radio terminal context (UE context) can be obtained from a first core network device based on the registration request; If the UE context can be obtained from the first core network device, sending a reroute request to the RAN; receiving a reroute transfer message from the RAN, the reroute transfer message including the UE context obtained by the RAN from the first core network device; transmitting a registration acceptance message to the wireless terminal; A method of a second core network device comprising:

2. The second core network device is a second Access and Mobility Management Function (AMF); The method of claim 1.

3. The first core network device is a first Access and Mobility Management Function (AMF); The method of claim 1.

4. The wireless terminal is a user equipment (UE), The method of claim 1.

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