Communication terminal, core network node, and method

Abstract

To provide a communication terminal and a core network that handle service access to isolated network slices, enabling separation between network slices and improving 5G security and data exchange integrity.SOLUTION: In a communication system 1, users of mobile devices 3 communicate with each other and other users via respective base stations 5 and a core network 7 using E-UTRA and / or 5G RAT. Each of the base stations 5 controls one or more associated cells. The core network 7 includes a control plane function (CPF) and a user plane function (UPF).SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present disclosure relates to communication systems. This disclosure has particular relevance, but not limited to, to wireless communication systems and devices thereof operating in accordance with 3rd Generation Partnership Project (3GPP) standards or equivalents or derivatives thereof. This disclosure is particularly, but not exclusively, relevant to on-demand registration into disjoint network slices of so-called "5G" (or "next generation") systems. [Background technology]

[0002] Network slicing capabilities defined in 3GPP Release 15 and Release 16 enable a wide variety of communication services for operators and industries. To increase the commercial viability of network slicing, GSMA 5GJA introduced the concept of Generic Slice Template (GST) in document NG.116 (Non-Patent Document 6) from which descriptions of various network slice types can be derived. Some parameters of GST explicitly indicate the definition of parameters and boundaries of the services offered to the end customer. However, the enforcement of some of these parameters and boundaries is not yet supported in 5GS.

[0003] The 3GPP SA1 study on enhanced access and support for network slices in Rel-18 (Non-Patent Document 4) considers various use cases and scenarios using network slices to identify potential service requirements for 5G systems, such as: -There are restrictions on network slicing to specific frequency bands / sub-bands, Radio Access Technologies (RATs), geographical regions, networks, and applications. -If the UE has registrations (subscriptions) to multiple network slices and these network slices are deployed, for example, for different frequency bands / sub-bands, RATs, geographic areas, and applications. When a network slice is preferred or prioritized over other network slices, for example when there are conflicting constraints on the availability of network slices. [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] 3GPP TR 21.905: "Vocabulary for 3GPP Specifications" V16.0.0 (2019-06) - https: / / www.3gpp.org / ftp / / Specs / archive / 21_series / 21.905 / 21905-g00.zip [Non-Patent Document 2] 3GPP TS 23.501: "System Architecture for the 5G System (5GS)" V16.7.0 (2020-12) - http: / / www.3gpp.org / ftp / Specs / archive / 23_series / 23.501 / 23501-g70.zip [Non-Patent Document 3] 3GPP TS 23.502: "Procedures for the 5G System (5GS)" V16.7.0 (2020-12) - http: / / www.3gpp.org / ftp / Specs / archive / 23_series / 23.502 / 23502-g70.zip [Non-Patent Document 4] 3GPP TR 22.835: "Study on Enhanced Access to and Support of Network Slices" V0.2.0 (2020-11) - http: / / www.3gpp.org / ftp / Specs / archive / 22_series / 22.835 / 22835-020.zip [Non-Patent Document 5] 3GPP TR 23.700-40: “Study on Enhancement of Network Slicing Phase 2” V1.2.0 (2020-11) - http: / / www.3gpp.org / ftp / tsg_sa / WG2_Arch / Latest_SA2_Specs / Latest_draft_S2_Specs / 23700-40-120.zip [Non-Patent Document 6] GSM Association Official Document NG.116: “Generic Network Slice Template” V2.0 (2019-10) - https: / / www.gsma.com / newsroom / wp-content / uploads / NG.116-v2.0.pdf [Non-Patent Document 7] 3GPP TS 38.413: "NG-RAN; NG Application Protocol (NGAP)" V16.3.0 (2020-09) - https: / / www.3gpp.org / ftp / / Specs / archive / 38_series / 38.413 / 38413-g30.zip Summary of the Invention [Problem to be solved by the invention]

[0005] As more network slices are deployed, each UE may be subscribed to 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 there are multiple related factors for network slicing, such as enterprise use and personal use, isolation requirements, general public use and public security use, frequency restrictions, location restrictions, etc.

[0006] Figure 1 illustrates a schematic example of disjoint network slices. Specifically, Figure 1 illustrates a use case scenario in which an (R)AN node connects to slice M, provided via a core network node for access and mobility management (e.g., AMF Y), and to slice N, provided by another core network node for access and mobility management (e.g., AMF X) for the same PLMN. For example, slice M is used for public safety, and slice N is used for Internet access. In the core network (e.g., 5GC), dedicated network resources and network functions are customized separately for public safety emergency services and video services to meet the requirements of isolation. This ensures the independence of core network resources between different network slices. Thus, the two network slices are separated and cannot be provided to a UE simultaneously. Such a network slice is called a disjoint network slice.

[0007] Subscription and configuration: - UEs A1 and A3 have registration to slice M. - UEs A2 and A3 have registration to slice N. -For UE A3, which application uses which network slice is configured.

[0008] Deployment: -Slice N and slice M are separated. -(R)AN can be connected to both slice M and slice N. Slice M and slice N are provided by the same PLMN. Problem to be solved: A telecommunication system (e.g., 5GS, etc.) has no mechanism to prevent a UE that is subscribed to multiple network slices that are not simultaneously provided to the UE (e.g., separate network slices) from simultaneously accessing multiple network slices.

[0009] To meet this requirement, telecommunications systems (e.g., 5G systems) need to be able to: -Provide optimal (e.g., based on ongoing applications, user preferences) network slices for the UE. Supports modification of the provided network slice with minimal disruption (e.g., when triggered by active applications or priority changes). [Means for solving the problem]

[0010] In one aspect, the communication terminal (3) A means for transmitting a first Non-Access Stratum (NAS) message to a core network node (10A), the first NAS message including first information indicating that the communication terminal (3) supports an on-demand registration function and second information indicating a list of network slices to which the communication terminal (3) requests registration; means for receiving a second NAS message from the core network node (10A) including third information indicating a first network slice used by the communication terminal (3) in a public land mobile network (PLMN) and fourth information indicating a second network slice to which the communication terminal (3) subscribes and which is supported by the PLMN but is not supported by the core network node (10A) in which the communication terminal (3) is registered; and means for triggering an on-demand registration to the second network slice, The first network slice and the second network slice are included in the list.

[0011] In one aspect, a core network node (10A) A means for receiving a first Non-Access Stratum (NAS) message from a communication terminal (3), the first NAS message including first information indicating that the communication terminal (3) supports an on-demand registration function and second information indicating a list of network slices to which the communication terminal (3) requests registration; means for generating, when the first NAS message is received, fourth information indicating a second network slice to which the communication terminal (3) subscribes and which is supported by a Public Land Mobile Network (PLMN) but which is not supported by the core network node (10A) to which the communication terminal (3) is registered; means for transmitting a second NAS message to the communication terminal (3), the second NAS message including third information indicating a first network slice used by the communication terminal (3) in the PLMN and the fourth information; The first network slice and the second network slice are included in the list.

[0012] In one aspect, a method for a communication terminal (3), comprising: A process of transmitting a first Non-Access Stratum (NAS) message to a core network node (10A), the NAS message including first information indicating that the communication terminal (3) supports an on-demand registration function and second information indicating a list of network slices to which the communication terminal (3) requests registration; A process of receiving a second NAS message from the core network node (10A), the second NAS message including third information indicating a first network slice used by the communication terminal (3) in a public land mobile network (PLMN) and fourth information indicating a second network slice to which the communication terminal (3) subscribes and which is supported by the PLMN but is not supported by the core network node (10A) in which the communication terminal (3) is registered; triggering an on-demand registration to the second network slice; The first network slice and the second network slice are included in the list.

[0013] In one aspect, a method for a core network node (10A), comprising: A process of receiving a first Non-Access Stratum (NAS) message from the communication terminal (3), the NAS message including first information indicating that the communication terminal (3) supports an on-demand registration function and second information indicating a list of network slices to which the communication terminal (3) requests registration; generating, when the first NAS message is received, fourth information indicating a second network slice to which the communication terminal (3) subscribes and which is supported by a public land mobile network (PLMN) but which is not supported by the core network node (10A) in which the communication terminal (3) is registered; transmitting a second NAS message to the communication terminal (3), the second NAS message including third information indicating a first network slice used by the communication terminal (3) in the PLMN and the fourth information; The first network slice and the second network slice are included in the list. Effect of the Invention

[0014] This disclosure proposes on-demand registration to a network slice where the UE is not registered, so that the UE can access services on the separated network slice via on-demand registration when access to the separated network slice is required by the UE or an application on the UE. Since the isolation between the separated network slices can be maintained, the security and data exchange integrity of 5G is improved. [Brief description of the drawings]

[0015] [Figure 1] FIG. 1 illustrates a schematic example of a separated network slice. [Diagram 2] FIG. 2 is a schematic timing (signaling) diagram illustrating an exemplary method for initial registration of a UE. [Diagram 3] Figure 3 shows that Solution 1 proposes "on-demand registration" in a separated network slice (e.g., separated network slice S-NSSAI_N). [Figure 4] Figure 4 shows that solution 2 proposes "on-demand registration" for a split network slice via rerouting to an AMF 10 that supports in-demand S-NSSAI (e.g., a split network slice). [Diagram 5] FIG. 5 illustrates diagrammatically a mobile (cellular or wireless) telecommunications system 1 to which the above aspects are applicable. [Figure 6] FIG. 6 is a block diagram illustrating the main components of the UE (mobile device 3) shown in FIG. [Figure 7] FIG. 7 is a block diagram illustrating the main components of an exemplary (R)AN node 5 (base station) shown in FIG. [Figure 8] FIG. 8 is a block diagram illustrating major components of a typical core network node (or function) shown in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Abbreviation 3GPP 3rd Generation Partnership Project 5G 5th Generation 5GC 5G Core Network 5GS 5G System 5G-AN 5G Access Network AF Application Function AMF Access and Mobility Management Function AS Application Server AUSF Authentication Server Function CAG Closed Access Group CST Generic Network Slice Template GSMA Global System for Mobile Communications GUAMI Globally Unique AMF Identifier gNB Next generation Node B GST Generic Slice Template MM Mobility Management MNO Mobile Network Operator NAS Non-Access Stratum NF Network Function NG-RAN Next Generation Radio Access Network NID Network identifier NPN Non-Public Network NR New Radio NSSAI Network Slice Selection Assistance Information NSSF Network Slice Selection Function PCC Policy and Charging Control PCF Policy Control Function PDU Protocol Data Unit PLMN Public land mobile network PNI-NPN Public Network Integrated NPN (R)AN (Radio) Access Network RAT Radio Access Technology RRC Radio Resource Control SAE System Architecture Evolution SNPN Stand-alone Non-Public Network S-NSSAI Single Network Slice Selection Assistance Information S-TMSI SAE-Temporary Mobile Subscriber Identity UDM Unified Data Management UDR Unified Data Repository UE User Equipment URSP UE Route Selection Policy

[0017] Definition For the purposes of this document, the terms and definitions set forth in 3GPP Technical Report (TR) 21.905 (Non-Patent Document 1) and below apply. Terms defined in this document take precedence over any definitions in 3GPP TR 21.905 (Non-Patent Document 1) of the same terms.

[0018] Commonalities -Applicability of sides All disclosures in this aspect are applicable not only to network slice processing in a PLMN, but also to network slice switching between one network slice in a PLMN and another network slice in a non-public network (NPN). Furthermore, all disclosures in this aspect are applicable to network slice processing in an NPN. The NPN may be either a standalone non-public network (SNPN) or a public network integrated NPN (PNI-NPN).

[0019] -New definition The following new definition is proposed: Available NSSAI (or other notation of network slice conforming to the definition below) - a list of one or more network slices (e.g., S-NSSAI, etc.) to which the UE 3 is subscribed and supported by the PLMN, but not supported by the current AMF 10 to which the UE 3 is registered. Members of the "Available NSSAI" are called available network slices (e.g., Available S-NSSAI, etc.). The list of available network slices may be generated based on interaction with other network nodes (e.g., the (R)AN node 5 and / or a network slice selection function node (e.g., NSSF 17, etc.) and / or a policy control function node (e.g., PCF 13, etc.) and / or a server for storing subscription information (UDM / UDR 15, etc.) and / or an operator policy and / or configuration for identifying network slices that the UE 3 did not or could not register but are supported by the PLMN and for which the UE 3 has registered. The list of available network slices may be provided to the UE 3 in an "Available NSSAI" parameter during the registration procedure (e.g., Registration Accept message), or via a UE Configuration Update procedure within a UE policy parameter (e.g., as part of a UE Route Selection Policy (URSP) parameter), or as an independent parameter. In one example, the available network slice list may be provided in an existing NAS message or a new NAS message during a NAS procedure (e.g., a service request procedure) in addition to the registration procedure or the UE Configuration Update procedure. Also, the available network slice list may be provided in an existing Access Stratum (AS) message (e.g., RRC SETUP message or RRC It can also be provided using a Reconfiguration Request message or an RRC Release message. There may be an available NSSAI for each access type: one NSSAI available for 3GPP access and another NSSAI available for non-3GPP access.In one example, the available NSSAI may be provided per PLMN or per registration area in which the UE 3 registered during the registration procedure. When the UE 3 needs to switch network slices between a network slice in a PLMN and a network slice in a PNI-NPN, or when the UE 3 needs to switch network slices within an NPN, the term "network slice" in this disclosure may be interpreted as a "closed access group (CAG)" or a combination of a "CAG" and a "network slice" or a "network identifier (NID)".

[0020] The available NSSAIs may take on different definitions. Various possible definitions are given below. One or more network slices (e.g., S-NSSAI) supported by the PLMN and also listed in the NSSAI subscribed to the UE3. One or more network slices (e.g., S-NSSAI) supported in the registration area of ​​the PLMN and also listed in the NSSAI subscribed to the UE3. One or more network slices (e.g., S-NSSAI) supported by the PLMN and also listed in the UE3's configured NSSAI. One or more network slices (e.g., S-NSSAI) that are supported in the registration area of ​​the PLMN and are also listed in the UE3's configured NSSAI. One or more network slices supported by the PLMN and listed in the UE3's subscribed NSSAI (e.g., S-NSSAI), minus one or more network slices listed in the allowed NSSAI. One or more network slices supported in the registration area of ​​the PLMN and listed in the subscribed NSSAI of the UE3 (e.g., S-NSSAI), minus one or more network slices listed in the allowed NSSAI. One or more network slices (e.g., S-NSSAI) supported by the PLMN and also listed in the UE3's configured NSSAI, minus one or more network slices listed in the allowed NSSAI. One or more network slices (e.g., S-NSSAI) supported in the registration area of ​​the PLMN and also listed in the UE3's configured NSSAI, minus one or more network slices listed in the allowed NSSAI.

[0021] -On-Demand Registration (or other notation of the procedure conforming to the definition below) - Registration by the UE3 to available network slices (e.g., available S-NSSAI(s)). An example of such available network slices are disjoint network slices that the UE3 was not initially able to register to because they are not simultaneously supported. The UE3 triggers an on-demand registration when an application on the UE3 requests access to one or more available network slices (e.g., available S-NSSAI), i.e., network slices to which the UE3 is not registered but to which the UE3 is subscribed and which are supported by the PLMN.

[0022] -On-Demand Registration Feature Support Indicator (or other representation of information conforming to the definition below) - A UE 3 that supports "on-demand registration" shall indicate an "on-demand registration feature support" indicator during registration (e.g., in a Registration Request message) so that the network can return a list of available network slices (e.g., available S-NSSAIs, etc.) if such a list exists.

[0023] -On-Demand NSSAI (or any other notation of network slice that conforms to the following definition): A list of one or more network slices (e.g., S-NSSAI) for which the UE3 triggers an on-demand registration, a PDU session establishment request, or a service request. Members of the "In demand NSSAI" parameter are called in-demand network slices (e.g., in-demand S-NSSAI) and are provided to the network during registration (e.g., in a Registration Request message) or in a UE configuration update procedure. One example of an in-demand network slice is a separate network slice that a UE3 could not previously register because separate network slices are not supported simultaneously.

[0024] Initial registration by providing UE3 with a list of available network slices The following example of an initial registration of a UE is a preparation procedure for the proposed new solution.

[0025] FIG. 2 is a schematic timing (signaling) diagram illustrating an example method for initial registration of a UE. The UE 3 subscribes to network slices S-NSSAI_M and S-NSSAI_N and camps on a cell supporting both network slices S-NSSAI_M and S-NSSAI_N. The UE 3 requests registration in both network slices, but the two requested network slices S-NSSAI_M and S-NSSAI_N are separate network slices and are supported by different AMFs 10 at the UE's location (e.g., AMF_1 10A supports S-NSSAI_M and AMF_2 10B supports S-NSSAI_N). If the UE 3 indicates "support for on-demand registration feature" in the Registration Request message, the separate network slice S-NSSAI_N is returned to the UE 3 as an available network slice supported by another AMF 10 at the UE location (e.g., AMF_2 10B).

[0026] 1). The UE 3 triggers its initial registration with the network (e.g., this step is initiated when the UE 3 is switched on).

[0027] 2). UE3 sends an RRC Connection Setup Complete message (Requested NSSAI = S-NSSAI_M, S-NSSAI_N, NAS message = Registration Request ("On-demand registration feature supported" indicator, Requested NSSAI = S-NSSAI_M, S-NSSAI_N)). The UE 3 first triggers an RRC connection establishment procedure with the (R)AN node 5, the UE 3 includes the S-NSSAI_M and S-NSSAI_N in the Requested NSSAI parameter of the RRC Connection Setup Complete message, and the UE 3 also includes a Registration Request message in the RRC Connection Setup Complete message according to TS 23.502 (Non-Patent Document 3). The UE 3 includes in the Registration Request message an "on-demand registration feature supported" indicator indicating that the UE 3 supports the "on-demand registration" feature (e.g., registration to a separate network slice).

[0028] 3). If the (R)AN node 5 cannot find an AMF 10 that supports both S-NSSAI_M and S-NSSAI_N, the (R)AN node 5 selects AMF_1 10A that supports only S-NSSAI_M.

[0029] 4). The (R)AN node 5 sends a UE initial message (NAS message = Registration Request ('on demand registration feature support' indicator, Requested NSSAI = S-NSSAI_M, S-NSSAI_N)) to the selected AMF_1 10A. The (R)AN node 5 forwards the Registration Request message from the UE 3 to the selected AMF_1 10A.

[0030] 5) Continue the registration procedure with AMF_1 10A according to 3GPP Technical Specification (TS) 23.502 (Non-Patent Document 3).

[0031] 6).If UE3 indicates "support for on-demand registration feature", AMF_1 10A checks the availability of network slices in (R)AN node 5 / NSSF17 / PCF13 / UDM / UDR15 / operator policy or configuration, and AMF_1 10A generates a list of available network slices (e.g., available NSSAI).

[0032] AMF_1 10A may get a list of UE subscribed network slices from UDM / UDR 15, AMF_1 10A may check with NSSF 17 which of these UE subscribed network slices are not supported by the PLMN, and UE 3 may also check with PCF 13 for network slice access restriction based on various criteria according to PCC rules in PCF 13 (e.g., network slice access restriction based on location or time, or restriction per specific UE 3, or access restriction based on other criteria). UDM / UDR 15 may provide additional network slice information for each subscribed network slice for subscribed and separate network slices.

[0033] The (R)AN node 5 may also provide information to the AMF_1 10A for generating a list of available network slices (e.g., available NSSAIs). For example, the AMF_1 10A may obtain information about S-NSSAIs supported by each neighboring AMF 10 from the (R)AN node 5. Each (R)AN node 5 connected to the AMF_1 10A may provide the combination of S-NSSAI with the associated AMF 10 in a NG SETUP REQUEST message, a RAN CONFIGURATION UPDATE ACKNOWLEDGE message or an AMF CONFIGURATION UPDATE message defined in 3GPP TS38.413 (Non-Patent Document 7), or other names of messages between the (R)AN node 5 and the AMF 10.

[0034] AMF_1 10A may also take into account other access restrictions of the network slice based on operator policies or settings.

[0035] Based on these interactions with the UDM / UDR 15, the NSSF 17, the PCF 13, the (R)AN node 5 and / or operator policies and / or configurations, the AMF_1 10A generates a list of network slices (e.g., available NSSAIs), referred to as available network slices. Thus, the available network slices are: - supported in the PLMN or in a registration area within the PLMN, - You have a valid UE subscription, -This is a network slice that is not provided to UE3 as an allowed network slice in this registration procedure. This list of available network slices (e.g., available NSSAIs) may include isolated network slices for which the UE 3 has requested registration but for which registration is not allowed because they are isolated network slices, even though they are supported within the PLMN or registration area, and are not supported by the AMF 10 to which the UE 3 registers (e.g., AMF_1 10A).

[0036] The list of available network slices (e.g., available NSSAIs) may also include network slices for which the UE 3 has not requested registration but for which the UE 3 has a valid subscription. The list of available network slices (e.g., available NSSAIs) may also include network slices included in the list of rejected network slices (e.g., network slices that are rejected because they are not supported by the current AMF 10 but are supported by other AMFs 10 in the PLMN, i.e., disjoint network slices) depending on the cause of the rejection.

[0037] 7).If the UE 3 indicates “support for on-demand registration feature” in the Registration Request message and the requested S-NSSAI_N is supported by another AMF 10 (e.g., AMF_2 10B), AMF_1 10A includes the S-NSSAI_N in the list of available network slices (e.g., in the “Available NSSAI” parameter of the Registration Accept message to the UE 3).

[0038] 8).AMF_1 10A sends a Registration Accept message (Allowed NSSAI=S-NSSAI_M, Available NSSAI=S-NSSAI_N) to UE3. AMF_1 10A confirms the registration of NSSAI_M by including NSSAI_M in the Allowed NSSAI parameter, and AMF_1 10A also returns S-NSSAI_N (currently available S-NSSAI) in the Available NSSAI parameter. Alternatively, the available S-NSSAI_N may be provided to UE3 with an additional differentiated tag (e.g., information, indicator, or parameter) in existing parameters such as Allowed NSSAI or Rejected NSSAI, or any other existing parameters in the Registration Accept message. This allows UE3 to distinguish S-NSSAI_N from other network slices.

[0039] 9).UE3 successfully registers S-NSSAI_M and UE3 receives S-NSSAI_N as an available S-NSSAI. If a service on such S-NSSAI is required by an application on the UE or UE3, or if UE3 receives a paging message containing an indication that UE3 requests activation of a service on such S-NSSAI, UE3 can trigger an "on-demand registration", a PDU session establishment request, or a service request for the available S-NSSAI (e.g., a separate S-NSSAI_N).

[0040] Alternatively, the UE 3 may predict, determine, or generate, independently of the network, which network slices qualify as available S-NSSAIs by subtracting the allowed S-NSSAIs from the subscribed S-NSSAI list, although this increases the likelihood that an "on-demand registration", PDU session establishment request, or service request will be rejected, since the UE cannot obtain complete information about the availability of network slices without the assistance of the network.

[0041] In one example, for a UE 3 that does not support the "on-demand registration feature", AMF_1 10A does not support S-NSSAI_N but can set S-NSSAI_N to an allowed NSSAI in the Registration Accept message. This can happen if UE 3 does not include the "on-demand registration feature support" indicator in the Registration Request message and AMF_1 10A knows that UE 3 can access S-NSSAI_N using other AMFs 10 while UE 3 stays in the registration area. After this registration procedure, when AMF_1 10A receives a PDU Session Establishment Request message or a Service Request message from UE 3 on S-NSSAI_N, AMF_1 10A sends a PDU Session Establishment Reject message or a Service Reject message to UE 3 with a new or existing cause value indicating to UE 3 that re-registration is required. When AMF_1 10A receives a new Registration Request message from the UE 3 with S-NSSAI_N set to the Requested NSSAI, AMF_1 10A treats S-NSSAI_N as an in-demand NSSAI parameter as described in Solution 2. Therefore, it can re-route the Registration Request message to a neighboring AMF 10 (e.g., AMF_2 10B) that supports S-NSSAI_N as described in Solution 2.

[0042] Solution 1 - Access to isolated network slices with on-demand registration Solution 1 proposes an "on-demand registration" to an isolated network slice (e.g., isolated network slice S-NSSAI_N) as shown in Figure 3. When an application (app) of UE3 requires a service in an isolated or available S-NSSAI (e.g., S-NSSAI_N), UE3 triggers on-demand registration by putting the required "available S-NSSAI_N" in RRC and Registration Request messages. UE3 also indicates that it supports the "on-demand registration feature".

[0043] 1). UE3 is subscribed to S-NSSAI_N and S-NSSAI_M. UE3 is in idle mode and camped on a cell that supports both S-NSSAI_N and S-NSSAI_M, and UE3 is registered for S-NSSAI_M via AMF_1 10A. UE3 is assigned an available S-NSSAI_N because S-NSSAI_N was separated from S-NSSAI_M during UE registration to AMF_1 10A for S-NSSAI_M (e.g., as shown in FIG. 2 and related description).

[0044] During the registration procedure, the UE 3 may obtain information about the support of the "on-demand registration function" from the (R)AN node 5 based on information conveyed in an RRC release or any RRC message during the registration procedure. Alternatively, the UE 3 may obtain information about the support of the "on-demand registration function" from the (R)AN node 5 via system information on a broadcast channel.

[0045] 2) An app in UE3 requires a service in an isolated network slice (e.g., "Available S-NSSAI_N"). The network slice S-NSSAI_N is available in the PLMN (e.g., supported by the PLMN), but UE3 is not registered for it. UE3 triggers an "on-demand registration" for the isolated network slice (e.g., Available S-NSSAI_N).

[0046] 3). The UE 3 sends an RRC Connection Setup Complete message (In demand NSSAI=S-NSSAI_N, Requested NSSAI=S-NSSAI_M, NAS message=Registration Request ("On demand registration feature supported" indicator, Requested NSSAI=S-NSSAI_N, S-NSSAI_M)) to the (R)AN node 5. The UE 3 first triggers an RRC connection establishment procedure with the (R)AN node 5, and the UE 3 includes the separated available S-NSSAI_N in the "In demand NSSAI" parameter and the requested S-NSSAI_M in the Requested NSSAI parameter and includes the Registration Request message as a NAS message in the RRC Connection Setup Complete message. The UE 3 may include the "In-Demand S-NSSAI_N" and the requested S_NSSAI_M in the RRC Connection Setup Complete message and may not include GUAMI or 5G-S-TMSI or 5G-GUTI in the RRC Connection Setup Complete message to force the (R)AN node 5 to perform AMF selection even though the UE 3 has not changed its location (e.g., the UE 3 remains in the same cell). If the (R)AN node 5 does not find an AMF 10 that supports both network slices S-NSSAI_N and S-NSSAI_M, the "In-Demand S-NSSAI_N" has preference / priority over the requested S-NSSAI_M. The UE 3 may not include the requested S_NSSAI_M in the RRC Connection Setup Complete message.

[0047] Alternatively, the in-demand S-NSSAI_N may be provided to the (R)AN node 5 using an additional differentiated tag (e.g., information, indication, or parameter) within an existing parameter such as the Requested NSSAI, or other existing parameter in an RRC message, allowing the (R)AN node 5 to distinguish the in-demand S-NSSAI_N from other network slices and prioritize the in-demand S-NSSAI_N when selecting an AMF 10.

[0048] In the Registration Request message, the UE 3 includes an "on-demand registration feature supported" indicator, indicating that the UE 3 supports the "on-demand registration" feature. The UE 3 also includes the S-NSSAI_N in the Requested NSSAI along with any other requested S-NSSAIs (e.g., S-NSSAI_M).

[0049] 4). (R)AN node 5 selects AMF_2 10B that supports "In-Demand S-NSSAI_N" which has a higher priority than S-NSSAI_M.

[0050] 5). The (R)AN node 5 sends a UE initial message (NAS message = Registration Request ("On-demand registration feature supported" indicator, Requested NSSAI = S-NSSAI_N, S-NSSAI_M)) to the AMF_2 10B. The (R)AN node 5 forwards the Registration Request message from the UE 3 to the AMF_2 10B.

[0051] 6). Continue the registration procedure with AMF_2 10B according to TS 23.502 (Non-Patent Document 3).

[0052] 7) If the UE 3 indicates "support for on-demand registration feature" in the Registration Request message, the AMF_2 10B includes the S-NSSAI_M in the "Available NSSAI" parameter returned to the UE 3 because the S-NSSAI_M is not supported by the AMF_2 10B. This is because the S-NSSAI_M and the S-NSSAI_N are separate network slices and are supported by the same AMF_2 10B, but the S-NSSAI_M is available in the PLMN and the UE 3 is subscribed to it. When determining whether the S-NSSAI_M is an available S-NSSAI, the AMF_2 10B may interact with the UDM / UDR 15, the PCF 13 and / or other network nodes to verify whether the S-NSSAI_M is the UE subscribed network slice and whether the S-NSSAI_M is not restricted by PCC rules, operator policies or configurations. AMF_2 10B may also check in NSSF 17 whether S-NSSAI_M is supported by another AMF 10 at the location of UE 3.

[0053] 8).AMF_2 10B sends a Registration Accept message (Allowed NSSAI=S-NSSAI_N, Available NSSAI=S-NSSAI_M) to UE3. AMF_2 10B confirms the registration of the isolated network slice S-NSSAI_N, i.e. "In-demand S-NSSAI_N", by including S-NSSAI_N in the Allowed NSSAI parameter, and AMF_2 10B also returns S-NSSAI_M (currently available S-NSSAI) in the Available NSSAI parameter. Alternatively, the available S-NSSAI_M may be provided to UE3 with an additional differentiation tag (e.g., information, indication or parameter) in existing parameters such as Allowed NSSAI or Rejected NSSAI, or any other existing parameters in the Registration Accept message. This allows UE3 to distinguish S-NSSAI_M from other network slices.

[0054] 9).UE3 may trigger an “on-demand registration”, a PDU session establishment request, or a service request to a separate available S-NSSAI (e.g., S-NSSAI_M) if a service on such S-NSSAI is required by UE3 or an application on UE3, or if UE3 receives a paging message on such S-NSSAI containing an indication that UE3 should activate a service.

[0055] Alternatively, the UE3 may predict, determine, or generate, independently of the network, which network slices qualify as available S-NSSAIs by subtracting allowed S-NSSAIs from the subscribed S-NSSAI list; however, in this case, without the assistance of the network, the UE3 may not have complete information about the availability of network slices, increasing the likelihood that the "on-demand registration" or service request will be rejected.

[0056] In one example, the UE 3 may set the S-NSSAI_N to the Requested NSSAI and not set any of the GUAMI or 5G-S-TMSI or 5G-GUTI in the RRC Connection Setup Complete message, and the (R)AN node 5 performs AMF selection based on existing mechanisms even though the UE 3 has not changed its location (e.g., the UE 3 remains in the same cell).

[0057] Solution 2 - Access to isolated network slices by rerouting registrations on demand Solution 2 proposes "on-demand registration" of a split network slice via re-routing to an AMF 10 that supports an in-demand S-NSSAI (e.g., split network slice), as shown in Figure 4. When an application (app) of UE 3 requires a service in a split or available S-NSSAI (e.g., S-NSSAI_N), UE 3 triggers on-demand registration by placing the required available S-NSSAI_N in the "In demand NSSAI" parameter in a Registration Request message to AMF_110A. Since AMF_110A does not support S-NSSAI_N in the Requested NSSAI, AMF_110A finds an AMF 10 that supports S-NSSAI_N and forwards the Registration Request message to the found AMF 10 (e.g., AMF_210B). UE 3 also indicates that it supports the "on-demand registration" feature.

[0058] 1). UE3 is subscribed to S-NSSAI_N and S-NSSAI_M. UE3 is in idle mode and camped on a cell that supports both S-NSSAI_N and S-NSSAI_M, and UE3 is registered for S-NSSAI_M via AMF_1 10A. During UE registration of S-NSSAI_M using AMF_1 10A, UE3 is assigned an available S-NSSAI_N because the S-NSSAI_N was separated from the S-NSSAI_M (e.g., as shown in FIG. 2 and the associated description).

[0059] 2) An app in UE3 requires a service in an isolated network slice (e.g., "Available S-NSSAI_N"). The network slice S-NSSAI_N is available in the PLMN (i.e., supported by the PLMN), but UE3 is not registered for it. UE3 triggers an on-demand registration for the isolated network slice (e.g., Available S-NSSAI_N).

[0060] 3). UE3 sends a Registration Request message ("On-demand registration feature supported" indicator, Requested NSSAI=S-NSSAI_M, Requested NSSAI=S-NSSAI_N) to AMF_1 10A. In the Registration Request message to AMF_1 10A, UE3 includes the "On-demand registration feature supported" indicator indicating that UE3 supports the "On-demand registration" feature. UE3 also includes the requested available S-NSSAI_N in the "In demand NSSAI" parameter along with the S-NSSAI_M in the Requested NSSAI parameter. The S-NSSAI_N in the "In demand NSSAI" parameter takes precedence over the requested S-NSSAI_M in the Requested NSSAI parameter.

[0061] Alternatively, the in-demand S-NSSAI_N may be provided to AMF_1 10A with an additional differentiated tag (e.g., information, indicator or parameter) within an existing parameter such as the Requested NSSAI or within any other existing parameter in the Registration Request message, thereby enabling AMF_1 10A to distinguish the in-demand S-NSSAI_N from other network slices and give priority to the in-demand S-NSSAI_N when selecting an AMF 10 for re-routing.

[0062] 4). “In-Demand S-NSSAI_N” is not supported by AMF_1 10A. With the help of NSSF17, AMF_1 10A finds AMF_2 10B which supports “In-Demand S-NSSAI_N” and re-routes UE3 to AMF_2 10B via (R)AN node 5.

[0063] 5) Re-route the initial UE messages to AMF_2 10B and continue the registration procedure in AMF_2 10B according to 3GPP TS 23.502 (Non-Patent Document 3).

[0064] 6) If the UE 3 indicated "support for on-demand registration feature" in the Registration Request message, the AMF_2 10B includes the S-NSSAI_M in the "Available NSSAI" parameter it returns to the UE 3, since the S-NSSAI_M is not supported by the AMF_2 10B, since the S-NSSAI_M and the S-NSSAI_N are separate network slices and are not supported by the same AMF_2 10B, and the S-NSSAI_M is available in the PLMN to which the UE 3 is subscribed. When determining whether the S-NSSAI_M is an available S-NSSAI, the AMF_2 10B may interact with the UDM / UDR 15, the PCF 13 and / or other network nodes to verify whether the S-NSSAI_M is the UE's subscribed network slice and whether the S-NSSAI_M is not restricted by PCC rules, operator policies or configuration. AMF_2 10B may also check in NSSF 17 whether S-NSSAI_M is supported by another AMF 10 at the location of UE 3.

[0065] 7).AMF_2 10B sends a Registration Accept(Allowed NSSAI=S-NSSAI_N,Available NSSAI=S-NSSAI_M) message to UE3. AMF_2 10B confirms the registration of the in-demand S-NSSAI_N by including S-NSSAI_N in the Allowed NSSAI parameter, and AMF_2 10B also returns S-NSSAI_M (currently available S-NSSAI) in the Available NSSAI parameter. Alternatively, the available S-NSSAI_M may be provided to UE3 with additional differentiation tags (e.g., information, indications or parameters) in existing parameters such as Allowed NSSAI or Rejected NSSAI, or any other existing parameters in the Registration Accept message. This allows UE3 to distinguish S-NSSAI_M from other network slices.

[0066] 8).If a service on such an S-NSSAI is required by the UE3 or an application on the UE3, or if the UE3 receives a paging message on such an S-NSSAI containing an indication that the UE3 should activate a service, the UE3 may trigger an "on-demand registration", a PDU session establishment request, or a service request to a separated available S-NSSAI (e.g., S-NSSAI_M).

[0067] Alternatively, the UE 3 may predict, determine, or generate, independently of the network, which network slices qualify as available S-NSSAIs by subtracting permitted S-NSSAIs from the subscribed S-NSSAI list, although this increases the likelihood that an "on-demand registration", PDU session establishment request, or service request will be rejected, since without the network assistance, the UE 3 cannot obtain complete information about the availability of network slices.

[0068] overview Beneficially, the above embodiments include one or more of the following features, including, but not limited to: -Available NSSAI - a list of one or more S-NSSAIs to which the UE is subscribed and which are supported by the PLMN, but are not supported by the current AMF. The list of available S-NSSAIs is provided to the UE during the registration procedure (e.g., in a new parameter in the Registration Accept message). -On-Demand NSSAI - A list of one or more available S-NSSAIs for which the UE triggers on-demand registration. The list of one or more available S-NSSAIs can be referred to as a list of on-demand S-NSSAIs. The list of on-demand S-NSSAIs is provided to the network during the registration procedure (e.g., in a new parameter in the Registration Request message). -On-Demand Registration Feature Support Indicator--A UE that supports "on-demand registration" shall indicate the "on-demand registration feature supported" indicator during the registration procedure (e.g., in the Registration Request message) so that the network returns a list of available S-NSSAIs.

[0069] To provide these capabilities, the above aspects describe an exemplary method that includes (at least some of) the following steps: - On-Demand Registration (Solution 1) - Registration by the UE to one or more available S-NSSAIs. Now, if the UE needs a service in a network slice to which it is subscribed but not registered, the UE can trigger a registration in that network slice if it is in the list of available S-NSSAIs provided to the UE at the last registration. For this, the UE mimics a location registration by adding the Requested NSSAI and the list of available S-NSSAIs in the RRC message and not including GUAMI, 5G-S-TMSI or 5G-GUTI in the RRC Connection Setup Complete message. This makes the (R)AN node perform an AMF selection as if the UE had changed its location, but the UE remains in the same cell. In this way, the NG-RAN node can select an AMF supporting an available S-NSSAI (for which service is required), since the available S-NSSAI has the priority of "on-demand registration". - On-demand registration with re-routing (Solution 2) - registration by the UE to one or more available S-NSSAIs. Now, if the UE needs a service in a network slice to which it is subscribed but not registered, the UE can trigger registration in that network slice if it is in the list of available S-NSSAIs provided to the UE during the last registration. For this, the UE includes a new parameter "In demand NSSAI" in the Registration Request message, which ensures that the UE is re-routed to a target AMF supporting the network slice in the "In demand NSSAI" parameter that has a higher priority than the network slice in the "Requested NSSAI" parameter.

[0070] System Overview FIG. 5 illustrates diagrammatically a mobile (cellular or wireless) telecommunications system 1 to which the above aspects are applicable.

[0071] In this network, users of mobile devices 3 can communicate with each other and with other users via respective base stations 5 and core networks 7 using an appropriate 3GPP radio access technology (RAT), e.g., E-UTRA and / or 5G RAT. It should be understood that multiple base stations 5 form a (radio) access network or (R)AN. As one skilled in the art will appreciate, three mobile devices 3 and one base station 5 are shown in FIG. 1. Referring to FIG. 5 for illustrative purposes, the system, when implemented, would typically include other base stations and mobile devices. The mobile devices 3 may be referred to as UEs 3 and the base stations 5 may be referred to as (R)AN nodes 5.

[0072] Each base station 5 controls (directly or via other nodes such as home base stations, relays, remote radio heads, distributed units, etc.) one or more associated cells. A base station 5 supporting the E-UTRA protocol for mobile devices 3 may be referred to as an "ng-eNB" and a base station 5 supporting next generation protocols for mobile devices 3 may be referred to as a "gNB". It will be understood that some base stations 5 may be configured to support both 4G and 5G, and / or any other 3GPP or non-3GPP communication protocols.

[0073] The mobile devices 3 and their serving base stations 5 are connected via suitable air interfaces (such as, for example, the so-called "Uu" interface). Neighbouring base stations 5 are connected to each other via suitable inter-base station interfaces (such as the so-called "X2" interface, the "Xn" interface, etc.). The base stations 5 / access networks are also connected to core network nodes via suitable interfaces (such as the so-called "NG-U" interface (for user plane), the so-called "NG-C" interface (for control plane) and / or the like).

[0074] The core network 7 typically includes logical nodes (or "functions") for supporting communications in the telecommunications system 1. Typically, for example, the core network 7 of a "next generation" / 5G system includes, among other functions, a control plane function (CPF) and a user plane function (UPF). It should be understood that the core network 7 may include, among other functions, one or more access and mobility management functions (AMFs) 10 (e.g., slice-specific AMFs 10A / 10B), a policy control function (PCF) 13, a unified data management (UDM) / unified data repository (UDR) function 15, and a network slice selection function (NSSF) 17. Although not shown in FIG. 5, the core network 7 may also be coupled to at least one application function (AF) / application server (AS), etc. A connection is also provided from the core network 7 to an external IP network / data network 20 (e.g., the Internet).

[0075] The components of the system 1 are configured to perform one or more of the methods described with reference to FIGS.

[0076] User Equipment (UE) FIG. 6 is a block diagram illustrating the main components of the UE (mobile device 3) shown in FIG. 5. As shown, the UE includes a transmit / receive (transceiver) circuit 31 operable to transmit signals to and receive signals from connected nodes via one or more antennas 33. Although not necessarily shown in FIG. 6, the UE of course has all the usual functions of a conventional mobile device (such as a user interface 35), which may suitably be provided by any one or any combination of hardware, software, and firmware. A controller 37 controls the operation of the UE according to software stored in memory 39. The software may be pre-installed in memory 39 and / or downloaded via the communication network 1 or, for example, from a removable data storage device (RMD). The software includes, among other things, an operating system 41 and a communication control module 43. The communication control module 43 is responsible for processing (generating / sending / receiving) signaling messages and uplink / downlink data packets between the UE 3 and other nodes, including the (R)AN node 5, application functions, and core network nodes. Such signaling includes appropriately formatted requests and responses related to on-demand registration of the UE 3 to the isolated network slice.

[0077] (R)AN Node FIG. 7 is a block diagram illustrating the main components of an exemplary (R)AN node 5 (base station) shown in FIG. 5. As shown, the (R)AN node 5 includes a transceiver circuit 51 operable to transmit and receive signals to and from a connected UE 3 via one or more antennas 53, and to transmit and receive signals to and from a network node (directly or indirectly) via a network interface 55. The network interface 55 typically includes a suitable base station-base station interface (such as X2 / Xn) and a suitable base station-core network interface (such as NG-U / NG-C). A controller 57 controls the operation of the (R)AN node 5 according to software stored in a memory 59. The software may be pre-installed in the memory 59 and / or downloaded via the communication network 1 or, for example, from a removable data storage device (RMD). The software includes, among other things, an operating system 61 and a communication control module 63. The communication control module 63 is responsible for handling (generating / sending / receiving) signaling between the (R)AN node 5, other nodes such as the UE 3, and the core network nodes. Such signaling includes properly formatted requests and responses for on-demand registration of the UE 3 to the isolated network slice.

[0078] Core Network Node FIG. 8 is a block diagram illustrating the main components of a generic core network node (or function) shown in FIG. 5, such as, for example, the AMF 10, the PCF 13, the UDM / UDR 15, and the NSSF 17. As shown, the core network node includes a transceiver circuit 71 operable to transmit and receive signals to and from other nodes (including the UE 3 and the (R)AN node 5) via a network interface 75. A controller 77 controls the operation of the core network node according to software stored in a memory 79. The software may be pre-installed in the memory 79 and / or downloaded via the communication network 1 or, for example, from a removable data storage device (RMD). The software includes, among other things, an operating system 81 and at least a communication control module 83. The communication control module 83 is responsible for handling (generating / sending / receiving) signaling between the core network node and other nodes, such as the UE 3, the (R)AN node 5, and other core network nodes. Such signaling includes appropriately formatted requests and responses for on-demand registration of the UE 3 to an isolated network slice.

[0079] Modifications and substitutions Detailed embodiments have been described above. As those skilled in the art will appreciate, many modifications and alternatives can be made to the above embodiments while still benefiting from the invention embodied therein. For purposes of example only, some of these alternatives and modifications are described herein.

[0080] In the above description, particular messages and parameters are used for illustrative purposes. However, it should be understood that any other suitable messages and parameters may be used, where appropriate. The above-mentioned parameters may be included in one or more appropriately formatted information elements, or the like.

[0081] In the above description, the UE, (R)AN node, and core network node are described as having several separate modules (such as a communications control module) for ease of understanding. These modules may be provided in this way for a particular application, for example where an existing system has been modified to implement the above aspects, but in other applications, the modules may not be identifiable as separate entities, as they are built into the overall operating system or code, for example in a system designed from the beginning with the inventive features in mind. These modules may also be implemented in software, hardware, firmware, or a combination of these.

[0082] Each controller may comprise any suitable form of processing circuitry including, for example, but not limited to, a microprocessor, a central processing unit (CPU), an arithmetic logic unit (ALU), input / output (IO) circuitry, internal memory / cache (program and / or data), processing registers, communications buses (e.g., control, data, and / or address buses), direct memory access (DMA) capabilities, hardware or software implemented counters, pointers, and / or timers, and / or the like.

[0083] In the above aspects, several software modules have been described. As those skilled in the art will appreciate, the software modules may be provided in compiled or uncompiled form and may be provided to the UE, the (R)AN node, and the core network node as a signal via a computer network or on a recording medium. Furthermore, the functions performed by some or all of this software may be performed using one or more dedicated hardware circuits. However, the use of software modules is preferred to facilitate the updating of the UE, the (R)AN node, and the core network node to update functions.

[0084] The above aspects may also be applied to "non-mobile" or generally stationary user equipment.

[0085] Various other modifications will be apparent to those skilled in the art and will not be described in further detail here.

[0086] All or part of the embodiments disclosed above can be described as follows, but are not limited to these. (Appendix 1) A communication terminal (3), A means for transmitting a first Non-Access Stratum (NAS) message to a core network node (10A), the first NAS message including first information indicating that the communication terminal (3) supports an on-demand registration function and second information indicating a list of network slices to which the communication terminal (3) requests registration; means for receiving a second NAS message from the core network node (10A) including third information indicating a first network slice used by the communication terminal (3) in a public land mobile network (PLMN) and fourth information indicating a second network slice to which the communication terminal (3) subscribes and which is supported by the PLMN but is not supported by the core network node (10A) in which the communication terminal (3) is registered; and means for triggering an on-demand registration to the second network slice, A communication terminal (3), wherein the first network slice and the second network slice are included in the list. (Appendix 2) The triggering means is executed when the communication terminal (3) or an application in the communication terminal (3) requests a service in the second network slice, or when the communication terminal (3) receives a paging message indicating that the communication terminal (3) needs to enable a service in the second network slice. 2. The communication terminal (3) according to claim 1. (Appendix 3) the triggering means transmits a third NAS message including the first information and the second information to a second core network node (10B); 3. A communication terminal (3) according to claim 1 or 2. (Appendix 4) The triggering means transmits a fourth NAS message including the first information, the fifth information, and the sixth information to the core network node (10A), the fifth information indicating the first network slice as a network slice to which the communication terminal (3) requests registration, and the sixth information indicating the second network slice as a network slice to which the communication terminal (3) did not previously register. 3. A communication terminal (3) according to claim 1 or 2. (Appendix 5) The receiving means receives a fifth NAS message from the second core network node (10B), the fifth NAS message including seventh information indicating the second network slice used by the communication terminal (3) in the PLMN, and eighth information indicating the first network slice to which the communication terminal (3) subscribes and which is supported by the PLMN but is not supported by the second core network node (10B) in which the communication terminal (3) is registered. A communication terminal (3) according to any one of appendix 1 to 4. (Appendix 6) The fourth information is set for each access type, PLMN, or registration area. A communication terminal (3) according to any one of appendix 1 to 5. (Appendix 7) A core network node (10A), A means for receiving a first Non-Access Stratum (NAS) message from a communication terminal (3), the first NAS message including first information indicating that the communication terminal (3) supports an on-demand registration function and second information indicating a list of network slices to which the communication terminal (3) requests registration; means for generating, when the first NAS message is received, fourth information indicating a second network slice to which the communication terminal (3) subscribes and which is supported by a Public Land Mobile Network (PLMN) but which is not supported by the core network node (10A) to which the communication terminal (3) is registered; means for transmitting a second NAS message to the communication terminal (3), the second NAS message including third information indicating a first network slice used by the communication terminal (3) in the PLMN and the fourth information; The first network slice and the second network slice are included in the list. A core network node (10A). (Appendix 8) the fourth information being generated based on at least one of an interaction with a network node (5, 17, 13, 15), an operator policy, and a configuration; A core network node (10A) as described in Supplementary Note 7. (Appendix 9) The receiving means receives a fourth NAS message from the communication terminal (3), the fourth NAS message including the first information, the fifth information, and the sixth information, the fifth information indicating the first network slice as a network slice to which the communication terminal (3) requests registration, and the sixth information indicating the second network slice as a network slice to which the communication terminal (3) has not previously registered; The core network node (10A) further includes a means for finding a second core network node (10B) that supports the second network slice when the second network slice indicated by the fifth information is not supported by the core network node (10A); means for rerouting the communication terminal (3) to the second core network node (10B); A core network node (10A) according to Supplementary Note 7 or 8. (Appendix 10) the second core network node (10B) is discovered based on an interaction with a network node (17); A core network node (10A) according to Supplementary Note 7 or 8. (Appendix 11) A communication terminal (3), A process of transmitting a first Non-Access Stratum (NAS) message to a core network node (10A), the NAS message including first information indicating that the communication terminal (3) supports an on-demand registration function and second information indicating a list of network slices to which the communication terminal (3) requests registration; A process of receiving a second NAS message from the core network node (10A), the second NAS message including third information indicating a first network slice used by the communication terminal (3) in a public land mobile network (PLMN) and fourth information indicating a second network slice to which the communication terminal (3) subscribes and which is supported by the PLMN but is not supported by the core network node (10A) in which the communication terminal (3) is registered; triggering an on-demand registration to the second network slice; A method, wherein the first network slice and the second network slice are included in the list. (Appendix 12) The triggering process is executed when the communication terminal (3) or an application in the communication terminal (3) requests a service in the second network slice, or when the communication terminal (3) receives a paging message indicating that the communication terminal (3) needs to enable a service in the second network slice. 12. The method according to claim 11. (Appendix 13) In the triggering process, a fourth NAS message including the first information, the fifth information, and the sixth information is sent to the core network node (10A), the fifth information indicating the first network slice as a network slice to which the communication terminal (3) requests registration, and the sixth information indicating the second network slice as a network slice to which the communication terminal (3) did not previously register. 13. The method according to claim 11 or 12. (Appendix 14) A core network node (10A), A process of receiving a first Non-Access Stratum (NAS) message from the communication terminal (3), the NAS message including first information indicating that the communication terminal (3) supports an on-demand registration function and second information indicating a list of network slices to which the communication terminal (3) requests registration; generating, when the first NAS message is received, fourth information indicating a second network slice to which the communication terminal (3) subscribes and which is supported by a public land mobile network (PLMN) but which is not supported by the core network node (10A) in which the communication terminal (3) is registered; transmitting a second NAS message to the communication terminal (3), the second NAS message including third information indicating a first network slice used by the communication terminal (3) in the PLMN and the fourth information; The first network slice and the second network slice are included in the list. method. (Appendix 15) the fourth information being generated based on at least one of an interaction with a network node (5, 17, 13, 15), an operator policy, and a configuration; 15. The method according to claim 14.

[0087] This application is based on and claims priority to Indian Patent Application No. 202011057170, filed on December 30, 2020, the disclosure of which is incorporated herein by reference in its entirety. [Explanation of symbols]

[0088] 1. Communication Systems 20 IP Networks / Data Networks 3. UE 31 Transmitting and receiving circuit 33 Antenna 35 User Interface 37 Controller 39 Memory 41 Operating Systems 43 Communication Control Module 5 (R)AN node (base station) 7 Core Network 51 Transmitting and receiving circuit 53 Antenna 55 Network Interface 57 Controller 59 Memory 61 Operating Systems 63 Communication Control Module 10 AMF 13 PCF 15 UDM / UDR 17 NSSF 71 Transmitting and receiving circuit 75 Network Interface 77 Controller 79 Memory 81 Operating Systems 83 Communication Control Module

Claims

1. A communication terminal, Transmitting a first message to a core network node, the first message including first information indicating support for use of the network slice; receiving a second message from the core network node, the second message including an Allowed Network Slice Selection Assistance Information (NSSAI), a Configured NSSAI, and second information; The second information indicates that an S-NSSAI (Single Network Slice Selection Assistance Information) included in the Configured NSSAI can be registered in a network on demand in response to a request from an application of the communication terminal, When the application of the communication terminal requests use of a service using the S-NSSAI, a third message including the S-NSSAI in a Requested NSSAI is sent to the core network node; Communications terminal.

2. The PDU session establishment procedure is initiated after the registration procedure of the S-NSSAI is successfully completed. The communication terminal according to claim 1.

3. The first information indicates that the communication terminal supports an on-demand registration function. The communication terminal according to claim 1.

4. A core network node, receiving a first message from a communication terminal, the first message including first information indicating support for use of a network slice; Sending a second message to the communication terminal, the second message including an Allowed NSSAI (Network Slice Selection Assistance Information), a Configured NSSAI, and second information; The second information indicates that an S-NSSAI (Single Network Slice Selection Assistance Information) included in the Configured NSSAI can be registered in a network on demand in response to a request from an application of the communication terminal, receiving a third message including the S-NSSAI in a Requested NSSAI from the communication terminal when the application of the communication terminal requests use of a service using the S-NSSAI; Core network node.

5. The PDU session establishment procedure is initiated after the registration procedure of the S-NSSAI is successfully completed. A core network node according to claim 4.

6. The first information indicates that the communication terminal supports an on-demand registration function. A core network node as claimed in claim 4.

7. means for determining said second information based on subscriber data in a UDM; A core network node according to claim 4.

8. The communication terminal, Transmitting a first message to a core network node, the first message including first information indicating support for use of the network slice; receiving a second message from the core network node, the second message including an Allowed Network Slice Selection Assistance Information (NSSAI), a Configured NSSAI, and second information; The second information indicates that an S-NSSAI (Single Network Slice Selection Assistance Information) included in the Configured NSSAI can be registered in a network on demand in response to a request from an application of the communication terminal, When the application of the communication terminal requests use of a service using the S-NSSAI, a third message including the S-NSSAI in a Requested NSSAI is sent to the core network node; method.

9. The PDU session establishment procedure is initiated after the registration procedure of the S-NSSAI is successfully completed. The method according to claim 8.

10. The first information indicates that the communication terminal supports an on-demand registration function. The method according to claim 8.

11. A core network node receiving a first message from a communication terminal, the first message including first information indicating support for use of a network slice; Sending a second message to the communication terminal, the second message including an Allowed NSSAI (Network Slice Selection Assistance Information), a Configured NSSAI, and second information; The second information indicates that an S-NSSAI (Single Network Slice Selection Assistance Information) included in the Configured NSSAI can be registered in a network on demand in response to a request from an application of the communication terminal, receiving a third message including the S-NSSAI in a Requested NSSAI from the communication terminal when the application of the communication terminal requests use of a service using the S-NSSAI; method.

12. The PDU session establishment procedure is initiated after the registration procedure of the S-NSSAI is successfully completed. The method of claim 11.

13. The first information indicates that the communication terminal supports an on-demand registration function. The method of claim 11.

14. and determining the second information based on subscriber data in the UDM. The method of claim 11.

15. The second message may include, in addition to the second information, and third information indicating that a part of the S-NSSAI in the list of Configured NSSAIs is permitted; The communication terminal according to claim 1.

16. receiving the second information from the core network node in response to transmitting the first information to the core network node; The communication terminal according to claim 1.

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