Method, device and equipment for selecting AMF (Advanced Media Function) switched across PLMN (Public Land

Abstract

The invention provides an access and mobile management function AMF selection method and device for switching across a public land mobile network PLMN, electronic equipment and a computer readable storage medium, and belongs to the technical field of communication. The method comprises the following steps: judging whether a user terminal is switched across PLMN or not; in response to cross-PLMN switching of the user terminal and switching initiated by a source PLMN for a visited public land mobile network VPLMN, acquiring slice information of the user terminal according to the capability level of the user terminal; sending a query request to a network element service storage function (NRF), so that the NRF selects a target AMF according to the NSSAI and the target TAI of the target PLMN in the slice information; and receiving a target AMF fed back by the NRF and executing AMF switching. The objective of the invention is to at least solve the problem that switching may be interrupted due to the fact that a target AMF with inaccurate slicing capability may be selected in a PLMN-crossing switching process in the prior art.

Description

Technical Field

[0001] The present invention relates to the field of communication technology, and in particular to a method, device, electronic device and computer-readable storage medium for selecting an AMF for cross-PLMN switching. Background Art

[0002] At present, during the cross-public land mobile network PLMN switching process, the target AMF selection is triggered by the source access and mobility management function AMF. The network element service storage function NRF query mechanism is used in the selection process. The query request sent by the source AMF to the NRF carries the target PLMN ID, source PLMN ID, slice instance identifier (NSI ID), single network slice selection auxiliary information S-NSSAI and network function service setting identifier (NFservice set ID). If the initiator is the source AMF, the query request will carry AMFregion, AMF set, GUMAI and target tracking area identifier TAI. However, for network deployment, if there are both target AMF ToB (industry users signed NSSAI 1) and target AMF ToC (public users signed NSSAI 2), when the slice capabilities of NSSAI 1 and NSSAI 2 are different, the NRF query mechanism is inaccurate for the selection of the target AMF.

[0003] For example, AMF ToB (subscribed to NSSAI 1) and AMF ToC (subscribed to NSSAI 2) belong to the same target PLMN ID, while the AMF region, AMFset, and GUMAI of the cross-network PLMN are invisible to the visited public land mobile network VPLMN. However, AMF ToB (subscribed to NSSAI 1) and AMF ToC (subscribed to NSSAI 2) are both linked to the 5G wireless access network NG-RAN to which the target TAI belongs, so it is impossible to accurately distinguish whether to select AMF ToB (subscribed to NSSAI 1) or AMF ToC (subscribed to NSSAI2). Therefore, during the cross-PLMN switching process, the target AMF with inaccurate slicing capabilities may be selected. For example, the target AMF can only meet some of the connected service capabilities of the user terminal UE, and the switching may be interrupted, affecting the UE's service experience. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a method, device, electronic device and computer-readable storage medium for selecting an AMF for cross-PLMN switching in view of the above-mentioned deficiencies in the prior art, so as to at least solve the problem that the target AMF with inaccurate slice capability may be selected during the cross-PLMN switching process in the related art, for example, the target AMF can only meet the partial connection state service capability of the user terminal UE, and the switching may be interrupted, affecting the service experience of the UE. In a first aspect, the present invention provides a method for selecting an access and mobility management function AMF for cross-public land mobile network PLMN switching, which is applied to the source AMF, and the method includes: determining whether the user terminal is cross-PLMN switching; in response to the user terminal being cross-PLMN switching and initiating switching when the source PLMN is a visited public land mobile network VPLMN, obtaining the slice information of the user terminal according to the capability level of the user terminal; sending a query request to the network element service storage function NRF, wherein the query request includes the slice information of the user terminal and the target tracking area identifier TAI, so that the NRF selects the target AMF according to the NSSAI and the target TAI of the target PLMN in the slice information; receiving the target AMF fed back by the NRF and performing AMF switching to support the service continuity of the user terminal for the cross-PLMN switching.

[0006] Preferably, the cross-PLMN handover includes one of the following: national roaming, shared network, inter-network roaming, and core network roaming. The slice information includes the single network slice selection auxiliary information S-NSSAI of the source PLMN of the allowed network slice selection auxiliary information NSSAI of the user terminal and the NSSAI of the target PLMN mapped with the allowed NSSAI.

[0007] Preferably, before determining whether the user terminal is switched across PLMNs, the method further comprises: receiving a switching request sent by a source NG-RAN, wherein the switching request comprises a result identifier of the source NG-RAN determining whether the user terminal is switched across PLMNs.

[0008] Preferably, the determining whether the user terminal is switching across PLMNs specifically includes: obtaining a target TAI, a cell identifier, and a global RAN node identifier in a switching request; determining whether the PLMN of the target TAI or the cell identifier is the same as the PLMN of the global RAN node identifier; in response to the determination result being different, determining that the user terminal is switching across PLMNs; and in response to the determination result being the same, determining that the user terminal is switching within the system.

[0009] Preferably, the method of obtaining the slice information of the user terminal according to the capability level of the user terminal specifically includes: determining whether the capability level of the user terminal supports the preset capability level; in response to the user terminal supporting the preset capability level, obtaining the slice information sent by the network after registration and carried by the user terminal; in response to the user terminal being unable to support the preset capability level, obtaining the slice information of the user terminal according to the S-NSSAI of the target PLMN, and the S-NSSAI of the source PLMN of the allowed NSSAI and the corresponding S-NSSAI of the target PLMN mapped with the allowed NSSAI in the user subscription data saved when the user terminal is registered; or, in response to the user terminal being unable to support the preset capability level, querying the roaming agreement locally configured by the AMF according to the S-NSSAI of the target PLMN of the allowed NSSAI, and determining the mapping relationship between the S-NSSAI of the source PLMN of the allowed NSSAI and the corresponding S-NSSAI of the target PLMN mapped with the allowed NSSAI, so as to obtain the slice information of the user terminal.

[0010] In a second aspect, the present invention also provides a method for selecting an AMF for cross-PLMN switching, which is applied to NRF, and the method includes: receiving a query request sent by a source AMF, wherein the query request includes slice information and a target TAI of a user terminal, and before the source AMF sends the query request, the source AMF determines whether the user terminal is switching across PLMNs, and in response to the user terminal switching across PLMNs and when the source PLMN initiates switching for a visited public land mobile network VPLMN, the source AMF obtains the slice information of the user terminal according to the capability level of the user terminal; selects a target AMF according to the NSSAI and target TAI of the target PLMN in the slice information; and feeds back the target AMF to the source AMF so that the source AMF performs AMF switching to support service continuity of user terminals switching across PLMNs.

[0011] Preferably, cross-PLMN switching includes one of the following: national roaming, shared network, inter-network roaming, core network roaming, and the slice information includes the single network slice selection auxiliary information S-NSSAI of the source PLMN of the allowed network slice selection auxiliary information NSSAI of the user terminal and the NSSAI of the target PLMN mapped with the allowed NSSAI.

[0012] Preferably, the target AMF is selected according to the NSSAI and target TAI of the target PLMN in the slice information, specifically including: finding a matching target AMF set according to the NSSAI of the target PLMN; and selecting the target AMF from the target AMF set according to the target TAI.

[0013] In a third aspect, the present invention also provides an AMF selection device for inter-PLMN switching, comprising: a judgment module, used to judge whether the user terminal is inter-PLMN switching, an acquisition module, connected to the judgment module, used to respond to the user terminal being inter-PLMN switching and initiating switching when the source PLMN is a visited public land mobile network VPLMN, and obtain the slice information of the user terminal according to the capability level of the user terminal; a sending module, connected to the acquisition module, used to send a query request to the NRF, wherein the query request includes the slice information and target TAI of the user terminal, so that the NRF selects the target AMF according to the NSSAI and target TAI of the target PLMN in the slice information; a first receiving module, used to receive the target AMF fed back by the NRF and perform AMF switching to support service continuity of user terminals switching across PLMNs.

[0014] Preferably, cross-PLMN switching includes one of the following: national roaming, shared network, inter-network roaming, core network roaming, and the slice information includes the single network slice selection auxiliary information S-NSSAI of the source PLMN of the allowed network slice selection auxiliary information NSSAI of the user terminal and the NSSAI of the target PLMN mapped with the allowed NSSAI.

[0015] Preferably, the device further comprises a second receiving module.

[0016] The second receiving module is used to receive a handover request sent by a source NG-RAN, wherein the handover request includes a result identifier of the source NG-RAN determining whether the user terminal is an inter-PLMN handover.

[0017] Preferably, the judging module comprises a first obtaining unit and a second judging unit.

[0018] The first acquisition unit is configured to acquire a target TAI, a cell identifier, and a global RAN node identifier in the handover request. The second judgment unit is connected to the first acquisition unit and configured to judge whether the PLMN of the target TAI or the cell identifier is the same as the PLMN of the global RAN node identifier, and in response to the judgment result being different, determine that the user terminal is switched across PLMNs, and in response to the judgment result being the same, determine that the user terminal is switched within the system.

[0019] Preferably, the acquisition module includes a second acquisition unit.

[0020] The second acquisition unit is used to determine whether the capability level of the user terminal supports the preset capability level. In response to the user terminal supporting the preset capability level, the slice information sent by the network after registration and carried by the user terminal is acquired. The second acquisition unit is also used to obtain the slice information of the user terminal according to the S-NSSAI of the target PLMN, the S-NSSAI of the source PLMN of the allowed NSSAI and the corresponding S-NSSAI of the target PLMN mapped with the allowed NSSAI in the user subscription data saved when the user terminal is registered, in response to the user terminal failing to support the preset capability level. Or, the second acquisition unit is also used to query the roaming agreement locally configured by the AMF according to the S-NSSAI of the target PLMN of the allowed NSSAI in response to the user terminal failing to support the preset capability level, and determine the mapping relationship between the S-NSSAI of the source PLMN of the allowed NSSAI and the corresponding S-NSSAI of the target PLMN mapped with the allowed NSSAI, so as to obtain the slice information of the user terminal.

[0021] In a fourth aspect, the present invention also provides an AMF selection device for inter-PLMN switching, comprising: a third receiving module, used to receive a query request sent by a source AMF, wherein the query request includes slice information and a target TAI of a user terminal, and before the source AMF sends the query request, the source AMF is used to determine whether the user terminal is switched across PLMNs, and in response to the user terminal switching across PLMNs and when the source PLMN initiates switching for a visited public land mobile network VPLMN, the source AMF is used to obtain the slice information of the user terminal according to the capability level of the user terminal.

[0022] The feedback module is connected to the third receiving module and is used to select the target AMF according to the NSSAI and target TAI of the target PLMN in the slice information, and feed back the target AMF to the source AMF so that the source AMF performs AMF switching and supports service continuity of user terminals switched across PLMNs.

[0023] Preferably, the feedback module comprises a selection unit.

[0024] The selection unit is used to find a matching target AMF set according to the NSSAI of the target PLMN, and select the target AMF from the target AMF set according to the target TAI.

[0025] In a fifth aspect, the present invention also provides an electronic device, comprising a memory and a processor, wherein the memory stores a computer program, and the processor is configured to run the computer program to implement the AMF selection method for cross-PLMN switching as described in any one of the first aspect or the second aspect.

[0026] In a sixth aspect, the present invention also provides a computer-readable storage medium having a computer program stored thereon. When the computer program is executed by a processor, the method for selecting an AMF for cross-PLMN switching as described in any one of the first aspect or the second aspect is implemented.

[0027] The present invention provides an AMF selection method, device, electronic device and computer-readable storage medium for inter-PLMN switching. When a user terminal switches across PLMNs and the source PLMN initiates switching as a visited public land mobile network VPLMN, the slice information of the user terminal is obtained according to the capability level of the user terminal, and a target AMF that better matches the slice information is selected based on the NRF query mechanism, thereby continuing the connection state service of the user terminal and avoiding service interruption caused by inaccurately selected target AMF that cannot meet the service capabilities of the user terminal. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a flow chart of a method for selecting an AMF for inter-PLMN handover according to Embodiment 1 of the present invention;

[0029] Figure 2 This is a flow chart of a method for selecting an AMF for inter-PLMN handover according to Embodiment 1 of the present invention;

[0030] Figure 3 A schematic diagram of a determination process of inter-PLMN handover in embodiment 1 of the present invention;

[0031] Figure 4 A logical diagram of an AMF obtaining slice information according to Embodiment 1 of the present invention;

[0032] Figure 5 A logical diagram of an NRF query mechanism according to Embodiment 1 of the present invention;

[0033] Figure 6 This is a schematic diagram of the structure of a device for selecting an AMF for inter-PLMN handover according to embodiment 3 of the present invention;

[0034] Figure 7 This is a schematic diagram of the structure of a device for selecting an AMF for inter-PLMN handover according to embodiment 4 of the present invention;

[0035] Figure 8 This is a schematic diagram of the structure of an electronic device according to Embodiment 5 of the present invention. DETAILED DESCRIPTION

[0036] In order to enable those skilled in the art to better understand the technical solution of the present invention, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0037] It should be understood that the specific embodiments and drawings described herein are only used to explain the present invention rather than to limit the present invention.

[0038] It can be understood that, in the absence of conflict, the various embodiments of the present invention and the various features in the embodiments can be combined with each other.

[0039] It can be understood that, for the convenience of description, the drawings of the present invention only show the parts related to the present invention, while the parts irrelevant to the present invention are not shown in the drawings.

[0040] It can be understood that each unit and module involved in the embodiments of the present invention may correspond to only one physical structure, or may be composed of multiple physical structures, or multiple units and modules may be integrated into one physical structure.

[0041] It can be understood that, without conflict, the functions and steps marked in the flowcharts and block diagrams of the present invention may occur in an order different from that marked in the drawings.

[0042] It is understood that the flowcharts and block diagrams of the present invention illustrate the possible architectures, functions, and operations of the systems, devices, equipment, and methods according to the various embodiments of the present invention. Each box in the flowchart or block diagram may represent a unit, module, program segment, or code, which contains executable instructions for implementing the specified functions. Moreover, each box or combination of boxes in the block diagram and flowchart may be implemented by a hardware-based system that implements the specified functions, or may be implemented by a combination of hardware and computer instructions.

[0043] It can be understood that the units and modules involved in the embodiments of the present invention can be implemented by software or hardware. For example, the units and modules can be located in a processor.

[0044] Embodiment 1:

[0045] This implementation provides a method for selecting an access and mobility management function AMF for handover across public land mobile networks (PLMNs), supporting more accurate selection of AMF in handover of user connection-state services from VPMN to HPLMN network, where connection-state services include data services and / or voice services. The selection method is applicable to a variety of scenarios for handover across PLMNs, such as national roaming, shared network, inter-network roaming, core network roaming, etc. For example, participating operators and hosted access network (RAN) operators provide services for user terminals (UEs) moving between their service areas, and the services provided are based on the user subscription and billing requirements of participating operators, including service logic provided by participating operators and hosted RAN operators, such as UE's voice, short message service (SMS), and data communications, etc.

[0046] Application scenarios include that user terminals can register with VPLMN, that is, they can log in to the 5G system through the NG-RAN and AMF of VPLMN, there is an intercommunication interface between VPLMN and HPLMN to transmit messages between network elements, and a cooperation agreement is signed between VPLMN and HPLMN, allowing terminals to switch between PLMNs to ensure business continuity. HPLMN allows terminals to move from VPLMN to HPLMN and allows terminal-related information to be transmitted between PLMNs. For example, the source PLMN (VPLMN) is a hosted RAN operator of the NG-RAN access network; the core network of the target PLMN has no direct connection with the shared NG-RAN of the source PLMN (VPLMN); there is a connection between the core network CN of the source PLMN (VPLMN) and the CN of the target PLMN. Application scenarios such as UE belongs to the target PLMN, and the UE successfully registers with the network of the target PLMN through the shared NG-RAN. The UE successfully initiates a service under the shared network of the source PLMN (VPLMN), such as a 5G voice call to any operator user.

[0047] like Figure 1 As shown, this embodiment provides a method for selecting an access and mobility management function AMF for handover across a public land mobile network PLMN, which is applied to a source AMF, including:

[0048] Step 101, determining whether the user terminal is switching across PLMNs.

[0049] In this embodiment, there are two ways for the source AMF to determine whether the user terminal is switched across PLMNs. One way is for the source RAN to determine whether the user terminal is switched across PLMNs, and send the result identifier corresponding to the determination result to the source AMF. When the source AMF trusts the determination result of the source NG-RAN, the source AMF directly determines whether the user terminal is switched across PLMNs based on the received result identifier. This method can save the computing resources of the source AMF and improve the efficiency of the target AMF selection. Another way is when the source AMF does not trust the determination result of the source RAN, the source AMF determines on its own whether the user terminal is switched across PLMNs. The reasons why the source AMF does not trust the source NG-RAN may be: the operator's configuration, or the source NG-RAN and the source AMF are from different manufacturers or different construction units. Therefore, this method can ensure the accuracy of the determination result of the cross-PLMN switching. The following details two specific ways to determine whether the user terminal is switched across PLMNs:

[0050] S1. The source AMF receives a handover request sent by the source NG-RAN, wherein the handover request includes a result identifier of the source NG-RAN determining whether the user terminal is an inter-PLMN handover.

[0051] In this embodiment, the UE moves from the source PLMN (VPLMN) shared network to the 5G area of ​​the target PLMN, such as Figure 2 As shown, the source NG-RAN (i.e., S-NG-RAN) assists the source AMF (i.e., S-AMF) in determining whether the user terminal is switching across PLMNs. For example, the source NG-RAN compares the PLMN used in the target network with the PLMN of the source Global RAN Node ID, and carries the parameters corresponding to the judgment result to the next network element source AMF, and the parameters include an indication of "intra-system switching". In the case of switching to the target PLMN, the source NG-RAN determines the PLMN to be used in the target network. The source NG-RAN shall indicate the selected PLMN ID (or PLMN ID and NID) to the AMF as part of the tracking area ID sent in the HO required message. This embodiment proposes that the source NG-RAN needs to compare the PLMN used in the target network with the PLMN of the source Global RAN Node ID. If the target PLMN is the same as the source PLMN, the source NG-RAN will carry the result identifier "intra-system handover" in the handover request sent to the source AMF. If they are not the same, the source NG-RAN will not carry the "intra-system handover", or the source NG-RAN will carry the result identifier "intra-system handover" in the handover request, but the result identifier "intra-system handover" = 0;

[0052] For example:

[0053] Global RAN Node ID also contains

[0054] PLMN Identity = 460abc (source PLMN)

[0055] CHOICE gNB ID

[0056] >gNB ID

[0057] >>gNB ID

[0058] The gNB ID is a BIT STRING (SIZE(22..32)) equal to the leftmost bits of the NR Cell Identity IE contained in the NR CGI IE for each cell served by the gNB.

[0059] Target PLMN Identity = 460xyz (target PLMN)

[0060] CHOICE Target ID

[0061] >NG-RAN

[0062] >>Global RAN Node ID

[0063] >>Selected TAI

[0064] S2, the source AMF (S-AMF) determines whether the user terminal is switching across PLMNs based on the result identifier "intra-system switching" (none, 0, 1) carried by the source NG-RAN in the switching request.

[0065] In this embodiment, Figure 3 As shown, the first message seen by the source AMF is from the source NG-RAN to the source AMF: a handover request message (carrying a target identifier (i.e., target ID), source-to-target transparent information, SMN2 information list, protocol data unit PDU session ID, and intra-system handover), where the value of the intra-system handover refers to step S1; the source-to-target transparent data (container) includes the NG-RAN information created by the source RAN for use by the target RAN, which is transparent to the 5G core network 5GC. It also contains the corresponding user plane security mandatory information, quality of service QoS flow / DRB information, etc. for each PDU session; when the source AMF receives a handover request sent from the wireless side, it first detects whether it carries the result identifier "intra-system handover". If the handover request does not carry the result identifier "intra-system handover", or the result identifier "intra-system handover = 0", the source AMF determines that the user terminal is a cross-PLMN handover. If the result identifier "intra-system handover" in the handover request = 1, the source AMF determines that the user terminal is not a cross-PLMN handover. Among them, Figure 3 The corresponding process 1 in Figure 2 The RAN in the process determines whether it is a PLMN handover, corresponding to process 2. Figure 2 The S-AMF in the system determines whether it is a PLMN handover. If "intra-system handover = 1", the intra-system handover process is performed according to the prior art.

[0066] When the source AMF does not trust the source NG-RAN, the source AMF determines on its own whether the user terminal is switching across PLMNs.

[0067] Specifically, the source AMF determines whether the user terminal is switched across PLMNs, including: obtaining the target tracking area identifier TAI, cell identifier, and global RAN node identifier in the switching request; determining whether the PLMN of the target TAI or cell identifier is the same as the PLMN of the global RAN node identifier; in response to the judgment result being different, determining that the user terminal is switched across PLMNs; in response to the judgment result being the same, determining that the user terminal is switched within the system.

[0068] In this embodiment, the source AMF can determine whether the user terminal meets the inter-PLMN handover conditions through TAI or cell ID. First, it determines whether the user terminal enters the handover process through the handover request handover require message, and then determines whether it is an inter-PLMN handover. Specifically, by judging the PLMN in the target ID, if there is no PLMN for the current session in the system, the source PLMN can be identified through the PLMN Identity in the Global RAN Node ID. The specific method of identification is: in order to reduce the system load, the right matching method can be used, because the MCC in China is the same. If it involves cross-border inter PLMN switching, left matching is required. If it is an int type, use "==" to determine whether it is equal; if it is an Integer type, the equals method can be used for equality comparison. For example:

[0069] >int target ID PLMN = 10;

[0070] >int local set PLMN = 10;

[0071] >System.out.print(target ID PLMN==local set PLMN)

[0072] If System.out.print = 1, the PLMN in the target ID is equal to the local PLMN, and it is not a handover between PLMNs. The subsequent AMF selection, AMF reselection, and handover process can be implemented according to the existing technology;

[0073] If System.out.print = 0, the PLMN in the target ID is not equal to the local PLMN, and inter-PLMN handover requires AMF selection for inter-PLMN handover;

[0074] The local set PLMN determined above can be the PLMN of the AMF set by the system or the source RAN information extracted by the N2 interface. The former is less accurate. The special scenario is that the AMF serves two PLMNs at the same time, that is, there are two local set PLMNs. At this time, it is still necessary to use the RAN side information of the N2 interface to determine which PLMN is used for the current call. If there is only one default PLMN configured by the AMF, it is not necessary to rely on the N2 interface information, such as Figure 2 shown.

[0075] Step 102, in response to the user terminal switching across PLMNs and the switching being initiated when the source PLMN is a visited public land mobile network VPLMN, the slice information of the user terminal is obtained according to the capability level of the user terminal.

[0076] In this embodiment, the slice information includes a single network slice selection auxiliary information S-NSSAI of the source PLMN of the allowed network slice selection auxiliary information NSSAI of the user terminal and the corresponding S-NSSAI of the target PLMN of the allowed NSSAI mapping, wherein the corresponding S-NSSAI of the target PLMN is the NSSAI of the target PLMN.

[0077] Before obtaining the slice information of the user terminal, it is necessary to determine that the source AMF currently serving the roaming user terminal is the source AMF of the VPLMN, and the user terminal is in the VPLMN initiating handover logic. The source AMF identifies that the UE is currently in a roaming scenario based on the NSSAI and other information of the VPLMN in the PDU context saved by the UE in the source AMF, or based on the NSSAI and other information of the VPLMN in the user subscription data of the user terminal in the source AMF, or based on the comparison between the source PLMN and the target PLMN in step 101. Figure 4 As shown, the source AMF obtains the slice information of the user terminal according to the capability level of the user terminal.

[0078] Specifically, the source AMF obtains the slice information of the user terminal according to the capability level of the user terminal, including: determining whether the capability level of the user terminal supports the preset capability level; in response to the user terminal supporting the preset capability level, obtaining the slice information sent by the network after registration and carried by the user terminal; in response to the user terminal not being able to support the preset capability level, obtaining the slice information of the user terminal according to the S-NSSAI of the target PLMN, and the S-NSSAI of the source PLMN of the allowed NSSAI and the corresponding S-NSSAI of the target PLMN mapped with the allowed NSSAI in the user subscription data saved when the user terminal is registered; or, in response to the user terminal not being able to support the preset capability level, querying the roaming agreement locally configured by the AMF according to the S-NSSAI of the target PLMN of the allowed NSSAI, and determining the mapping relationship between the S-NSSAI of the source PLMN of the allowed NSSAI and the corresponding S-NSSAI of the target PLMN mapped with the allowed NSSAI, so as to obtain the slice information of the user terminal.

[0079] In this embodiment, if the UE already supports the preset capability level (e.g., R16), the UE is capable of providing the S-NSSAI of the HPLMN and VPLMN to the network. That is, in the PDU session establishment request message, the UE includes the S-NSSAI of the allowed NSSAI from the current access type. If the network provides the UE with the allowed NSSAI mapping when the UE registers, the UE should provide the S-NSSAI of the VPLMN from the allowed NSSAI and the corresponding S-NSSAI of the HPLMN from the allowed NSSAI mapping. That is, the UE needs to carry the allowed S-NSSAI and the mapped HPLMN SST+mappedHPLMN SD issued by the network after registration.

[0080] The source AMF may adopt the "S-NSSAI of the VPLMN with allowed NSSAI and the corresponding S-NSSAI of the HPLMN with allowed NSSAI mapping" carried by the UE. If in some scenarios, the source AMF cannot trust the parameters carried by the UE, the source AMF may compare the "S-NSSAI of the VPLMN with allowed NSSAI and the corresponding S-NSSAI of the HPLMN with allowed NSSAI mapping" carried by the UE with the "S-NSSAI of the VPLMN with allowed NSSAI and the corresponding S-NSSAI of the HPLMN with allowed NSSAI mapping" in the user subscription data stored by the AMF to further and more accurately determine whether to use the UE parameters or the network parameters.

[0081] Among them, the "S-NSSAI of the VPLMN of the allowed NSSAI and the corresponding S-NSSAI of the HPLMN of the allowed NSSAI mapping" in the user subscription data saved by the source AMF is finally obtained by judging the roaming agreement signed by the roaming user when the UDM user contract information and other processes are executed when the user terminal is registered. If the AMF does not trust the "S-NSSAI of the VPLMN of the allowed NSSAI and the corresponding S-NSSAI of the HPLMN of the allowed NSSAI mapping" carried by the UE, it can still rely on the "S-NSSAI of the VPLMN of the allowed NSSAI and the corresponding S-NSSAI of the HPLMN of the allowed NSSAI mapping" saved by the AMF.

[0082] In this embodiment, if the UE does not support the preset capability level (for example, a user terminal before R16), the UE is only capable of providing the S-NSSAI of the HPLMN to the network (HPLMN S-NSSAI, not Mapped S-NSSAI). That is, in the PDU session establishment request message, the UE includes the S-NSSAI of the allowed NSSAI of the home network access type. Or it is also possible that the network did not provide the UE with the allowed NSSAI mapping when the UE registered, then the UE cannot provide the S-NSSAI of the VPLMN from the allowed NSSAI and the corresponding S-NSSAI from the HPLMN from the allowed NSSAI mapping. In the above two cases, the UE does not carry the "S-NSSAI of the VPLMN with allowed NSSAI", and the UE is only capable of providing the S-NSSAI of the home PLMN to the network (HPLMNS-NSSAI, not Mapped S-NSSAI). At this time, there are the following two mechanisms:

[0083] (1) When the user is roaming access at the time of registration, that is, accessing from the VPLMN, the "S-NSSAI of the VPLMN of the allowed NSSAI and the corresponding S-NSSAI of the HPLMN of the allowed NSSAI mapping" in the usersubscription data saved by the S-AMF is the final result of judging the roaming agreement signed by the roaming user when registering and executing the UDM user subscription information and other processes. It is stored in the S-AMF or in the usersubscriptiondata saved by the S-AMF. When the UE's PDU session is switched without carrying the "S-NSSAI of the VPLMN with allowed NSSAI" or the AMF does not save the "S-NSSAI of the VPLMN with allowed NSSAI" and the "S-NSSAI of the VPLMN with allowed NSSAI and the corresponding S-NSSAI of the HPLMN mapped with allowed NSSAI" when the PDU session is established, the VPLMN and HPLMN and the corresponding S-NSSAI are obtained according to the S-NSSAI of the home PLMN and the "S-NSSAI of the VPLMN with allowed NSSAI and the corresponding S-NSSAI of the HPLMN mapped with allowed NSSAI" in the user subscription data saved by the S-AMF during registration;

[0084] (2) If the information is not stored in the S-AMF or the user subscription data saved by the S-AMF, the roaming agreement locally configured by the AMF can be queried through the S-NSSAI of the HPLMN of the allowed NSSAI to determine the mapping relationship between the S-NSSAI of the VPLMN of the allowed NSSAI and the corresponding S-NSSAI of the HPLMN of the allowed NSSAI mapping. If the user subscription data lacks the necessary information for mapping, it is necessary to query the UDM for the exact user information before performing the mapping. Generally, the mapping can be completed in the S-AMF, and it is not ruled out that the NSSF assists in completing the mapping. The S-AMF needs to obtain an accurate mapping relationship between the S-NSSAI of the VPLMN of the allowed NSSAI and the corresponding S-NSSAI of the HPLMN of the allowed NSSAI mapping to complete the seventh step. The above step (2) is the enhanced part of AMF. If the user subscription data lacks the necessary mapping information, the corresponding technical process needs to be triggered, including: obtaining the necessary user information through UDM query, based on the mapping relationship between the S-NSSAI in the Requested NSSAI carried by the UE and the S-NSSAI of the HPLMN, and providing the mapping relationship to the network slice selection process, not only to determine the Allowed NSSAI of the UE, but also to determine the mapping relationship between the S-NSSAI in the Allowed NSSAI and the S-NSSAI of the HPLMN according to the roaming agreement. Among them, the network slice mapping relationship can be determined by the AMF or NSSF, and the Allowed NSSAI is determined by the visited domain NSSF or AMF.

[0085] Step 103, send a query request to the network element service storage function NRF, wherein the query request includes the slice information of the user terminal and the target tracking area identifier TAI, so that the NRF selects the target AMF according to the NSSAI and target TAI of the target PLMN in the slice information.

[0086] Specifically, the NRF selects the target AMF according to the NSSAI and target TAI of the target PLMN in the slice information, which specifically includes: the NRF finds a matching target AMF set according to the NSSAI of the target PLMN; the NRF selects the target AMF from the target AMF set according to the target TAI.

[0087] Or, select the target AMF according to the NSSAI and target TAI of the target PLMN in the slice information, specifically including: finding a matching target AMF set according to the target TAI; selecting the target AMF from the target AMF set according to the NSSAI of the target PLMN.

[0088] NSSAI of target PLMN In this embodiment, the source AMF shall adopt the NRF query mechanism when performing the target AMF (i.e. T-AMF) selection. NF service users can request to create a subscription to a specific NF instance or a group of NF instances for the "subscrCond" attribute of the "SubscriptionData" object type, according to the requested instance type reqNfType, the FQDN of the instance reqNfFqdn, the requested NSSAI reqSnssais, the requested NSSAI of each PLMN reqPerPlmnSnssais, the requested PLMN list reqPlmnList, etc. Figure 5 As shown, the NRF query mechanism includes steps S11-S12.

[0089] S11 requires that when AMF queries the instance through NRF, it can carry the S-NSSAI of the VPLMN of the UE's allowed NSSAI and the corresponding S-NSSAI of the HPLMN mapped with the allowed NSSAI, which is obtained or stored by AMF, corresponding to the PDU session. That is, when AMF queries NRF, it carries the PLMN+NSSAI of the user requesting the service and the target PLMN+NSSAI, where the PLMN+NSSAI is the S-NSSAI of the VPLMN and the VPLMN of the allowed NSSAI. The target PLMN+NSSAI is the corresponding S-NSSAI of the HPLMN and the HPLMN mapped with the allowed NSSAI.

[0090] In this embodiment, when the source AMF receives the Handover Required message, it performs target AMF selection: When the S-AMF can no longer serve the UE, the S-AMF selects the T-AMF. When moving across PLMNs, the S-AMF selects the AMF instance in the target PLMN by querying the target PLMN level NRF using the source PLMN level NRF of the target PLMNID. The target PLMN level NRF returns the AMF instance address according to the target network configuration.

[0091] S12, the source NRF needs to support the PLMN+NSSAI and the target PLMN+NSSAI carried by the service requesting user, as well as the NRF's authentication permission for the query method, and route the HPLMN NRF according to the target PLMN+NSSAI, and carry the target PLMN+NSSAI. The HPLMN NRF makes a judgment based on the query of the target PLMN+NSSAI and the data of the roaming agreement between the VPLMN NRF and the HPLMN NRF, and uses the target PLMN+NSSAI as one of the bases for selecting T-AMF when selecting T-AMF.

[0092] In this embodiment, when the VPLMN S-AMF sends a query request to the VPLMN NRF, if the target NF being queried is the AMF, the request may include: AMF area, AMF set, GUAMI and target TAI. In the present invention, targetPLMN+NSSAI also needs to be carried. The VPLMN NRF carries this information to the HPLMN NRF. The HPLMN NRF selects the regional affiliation (large area) of the AMF according to the AMF area, and then selects an AMF set (a province) in the large area. However, the GUAMI is generally inaccurate and is not even carried in cross-region selection. Of course, the AMF area and AMF set may not be carried in cross-region selection (because it is an AMF parameter across PLMNs, and the AMF parameter is only valid within the PLMN). Then the valid parameters will only be the target PLMN+NSSAI and TAI. At this time, the HPLMN NRF can select a relatively accurate AMF instance through network configuration and return it to the VPLMN NRF, including the AMF area, AMF set, GUAMI, NSSAI, FQDN and IP address to which the AMF belongs. Of course, for network security, the AMF area and other information may be desensitized. For example, the HPLMN NRF first determines whether the VPLMN NRF has signed an agreement with it for cross-PLMN switching and network selection. If the HPLMN NRF determines that the contract is reasonable, it extracts the target PLMN+NSSAI and TAI information, first matches the NSSAI supported by the AMF, selects a part of the AMF, and then corresponds to the TAI information, which can further improve the accuracy of the AMF selection. In this embodiment, the order of parameter matching is not limited. According to the TAI, a suitable AMF instance is found and returned to the destination NRF, including the AMF area, AMF set, GUAMI, NSSAI and FQDN to which the AMF belongs. It should be noted that TAI information can be subdivided and operated consistently across PLMNs through planning means. For example, TAI has different planning granularities according to different ranges specified by different parameters. The more detailed the planning means, the more accurate the AMF found according to TAI, but it may bring more operational burden. The T-AMF obtained according to the target PLMN+NSSAI and TAI information will greatly increase the accuracy of AMF during switching, reduce QoE and QoS issues such as dropped calls, and better meet SLA. The VPLMN NRF forwards this information to the VPLMN AMF, and the AMF executes the subsequent S-AMF to T-AMF:NAMF_Communication_CreateUEContextRequest and continues the subsequent operations. When UE 2 moves between the shared network and the non-shared network, the service continues and the service experience is improved.

[0093] Step 104, receiving the target AMF fed back by the NRF and performing AMF switching to support service continuity of the user terminal that switches across PLMNs. The method for selecting the AMF for cross-PLMN switching of this embodiment, when the user terminal switches across PLMNs and the source PLMN initiates switching for a visited public land mobile network VPLMN, obtains the slice information of the user terminal according to the capability level of the user terminal, and selects the target AMF that better matches the slice information based on the NRF query mechanism, so that the connection state service of the user terminal continues, avoiding the situation where the service is interrupted due to the inaccurate selection of the target AMF and the inability to meet the service capabilities of the user terminal. Furthermore, the source RAN determines whether the user terminal switches across PLMNs, and sends the result identifier corresponding to the judgment result to the source AMF. The source AMF directly determines whether the user terminal switches across PLMNs based on the received result identifier, which can save the computing resources of the source AMF and improve the efficiency of the target AMF selection. The source AMF determines whether the user terminal switches across PLMNs by itself, which can ensure the accuracy of the judgment result of the cross-PLMN switching. In addition, the accuracy of target AMF selection can be improved by finding the appropriate AMF based on the S-NSSAI of the VPLMN of the UE's allowed NSSAI and the corresponding S-NSSAI of the HPLMN mapped with the allowed NSSAI. Finally, the T-AMF obtained based on the NSSAI of the target PLMN and the target TAI information will greatly increase the accuracy of the AMF during handover, reduce QoE and QoS issues such as dropped calls, and better meet SLA.

[0094] Embodiment 2:

[0095] This embodiment provides a method for selecting an access and mobility management function AMF for handover across a public land mobile network PLMN, which is applied to an NRF. The method includes:

[0096] Step 201, receiving a query request sent by a source AMF, wherein the query request includes the slice information and target TAI of the user terminal. Before the source AMF sends the query request, the source AMF determines whether the user terminal is switched across PLMNs. In response to the user terminal switching across PLMNs and when the source PLMN initiates switching as a visited public land mobile network VPLMN, the source AMF obtains the slice information of the user terminal according to the capability level of the user terminal.

[0097] Step 202, select the target AMF according to the NSSAI and target TAI of the target PLMN in the slice information.

[0098] Step 203: Feedback the target AMF to the source AMF so that the source AMF performs AMF switching to support service continuity of user terminals switched across PLMNs.

[0099] Optionally, cross-PLMN switching includes one of the following: national roaming, shared network, inter-network roaming, and core network roaming. The slice information includes the single network slice selection auxiliary information S-NSSAI of the source PLMN of the allowed network slice selection auxiliary information NSSAI of the user terminal and the corresponding S-NSSAI of the target PLMN of the allowed NSSAI mapping, wherein the corresponding S-NSSAI of the target PLMN is the NSSAI of the target PLMN.

[0100] Optionally, before determining whether the user terminal is switched across PLMNs, the source AMF receives a switching request sent by a source NG-RAN, wherein the switching request includes a result identifier of the source NG-RAN determining whether the user terminal is switched across PLMNs.

[0101] The source AMF determines whether the user terminal is switched across PLMNs, specifically including: the source AMF obtains the target tracking area identifier TAI, cell identifier, and global RAN node identifier in the switching request; the source AMF determines whether the PLMN of the target TAI or cell identifier is the same as the PLMN of the global RAN node identifier; in response to the judgment result being different, the source AMF determines that the user terminal is switched across PLMNs; in response to the judgment result being the same, the source AMF determines that the user terminal is switched within the system.

[0102] The source AMF obtains the slice information of the user terminal according to the capability level of the user terminal, specifically including: the source AMF determines whether the capability level of the user terminal supports the preset capability level; in response to the user terminal supporting the preset capability level, the source AMF obtains the slice information sent by the network after registration and carried by the user terminal; in response to the user terminal failing to support the preset capability level, the source AMF obtains the slice information of the user terminal according to the S-NSSAI of the target PLMN, the S-NSSAI of the source PLMN of the allowed NSSAI in the user subscription data saved when the user terminal registers, and the corresponding S-NSSAI of the target PLMN mapped with the allowed NSSAI; or, in response to the user terminal failing to support the preset capability level, the source AMF queries the roaming agreement locally configured by the AMF according to the S-NSSAI of the target PLMN of the allowed NSSAI, and determines the mapping relationship between the S-NSSAI of the source PLMN of the allowed NSSAI and the corresponding S-NSSAI of the target PLMN mapped with the allowed NSSAI, so as to obtain the slice information of the user terminal.

[0103] Optionally, the target AMF is selected according to the NSSAI and target TAI of the target PLMN in the slice information, specifically including: finding a matching target AMF set according to the NSSAI of the target PLMN; selecting the target AMF from the target AMF set according to the target TAI. Or, the target AMF is selected according to the NSSAI and target TAI of the target PLMN in the slice information, specifically including: finding a matching target AMF set according to the target TAI; selecting the target AMF from the target AMF set according to the NSSAI of the target PLMN.

[0104] In this embodiment, the source AMF shall adopt the NRF query mechanism when performing the target AMF (i.e., T-AMF) selection. The NF service user may request to create a subscription to a specific NF instance or a group of NF instances for the "subscrCond" attribute of the "SubscriptionData" object type, according to the requested instance type reqNfType, the FQDN of the instance reqNfFqdn, the requested NSSAI reqSnssais, the requested NSSAI for each PLMN reqPerPlmnSnssais, the requested PLMN list reqPlmnList, etc. The NRF query mechanism includes steps S11-S12.

[0105] S11 requires that when AMF queries the instance through NRF, it can carry the S-NSSAI of the VPLMN of the UE's allowed NSSAI and the corresponding S-NSSAI of the HPLMN mapped with the allowed NSSAI, which is obtained or stored by AMF, corresponding to the PDU session. That is, when AMF queries NRF, it carries the PLMN+NSSAI of the user requesting the service and the target PLMN+NSSAI, where the PLMN+NSSAI is the S-NSSAI of the VPLMN and the VPLMN of the allowed NSSAI. The target PLMN+NSSAI is the corresponding S-NSSAI of the HPLMN and the HPLMN mapped with the allowed NSSAI.

[0106] In this embodiment, when the source AMF receives the Handover Required message, it performs target AMF selection: When the S-AMF can no longer serve the UE, the S-AMF selects the T-AMF. When moving across PLMNs, the S-AMF selects the AMF instance in the target PLMN by querying the target PLMN level NRF using the source PLMN level NRF of the target PLMNID. The target PLMN level NRF returns the AMF instance address according to the target network configuration.

[0107] S12, the source NRF needs to support the PLMN+NSSAI and the target PLMN+NSSAI carried by the service requesting user, as well as the NRF's authentication permission for the query method, and route the HPLMN NRF according to the target PLMN+NSSAI, and carry the target PLMN+NSSAI. The HPLMN NRF makes a judgment based on the query of the target PLMN+NSSAI and the data of the roaming agreement between the VPLMN NRF and the HPLMN NRF, and uses the target PLMN+NSSAI as one of the bases for selecting T-AMF when selecting T-AMF.

[0108] Embodiment 3:

[0109] like Figure 6 As shown, this embodiment provides an AMF selection device for inter-PLMN switching, which is applied to the source AMF, including:

[0110] The judging module 61 is used to judge whether the user terminal is switching across PLMNs.

[0111] The acquisition module 62 is connected to the judgment module 61, and is used to obtain the slice information of the user terminal according to the capability level of the user terminal in response to the user terminal switching across PLMNs and initiating switching when the source PLMN is a visited public land mobile network VPLMN.

[0112] The sending module 63 is connected to the acquisition module 62, and is used to send a query request to the NRF, wherein the query request includes the slice information and target TAI of the user terminal, so that the NRF selects the target AMF according to the NSSAI and target TAI of the target PLMN in the slice information.

[0113] The first receiving module 64 is used to receive the target AMF fed back by the NRF and perform AMF switching to support service continuity of user terminals switched across PLMNs.

[0114] Optionally, cross-PLMN switching includes one of the following: national roaming, shared network, inter-network roaming, and core network roaming. The slice information includes the single network slice selection auxiliary information S-NSSAI of the source PLMN of the allowed network slice selection auxiliary information NSSAI of the user terminal and the corresponding S-NSSAI of the target PLMN of the allowed NSSAI mapping, wherein the corresponding S-NSSAI of the target PLMN is the NSSAI of the target PLMN.

[0115] Optionally, the selection device further includes a second receiving module.

[0116] The second receiving module is used to receive a handover request sent by a source NG-RAN, wherein the handover request includes a result identifier of the source NG-RAN determining whether the user terminal is an inter-PLMN handover.

[0117] Optionally, the judging module includes a first obtaining unit and a second judging unit.

[0118] The first acquisition unit is used to acquire the target TAI, the cell identifier, and the global RAN node identifier in the handover request.

[0119] The second judgment unit is connected to the first acquisition unit, and is used to judge whether the PLMN identified by the target TAI or cell is the same as the PLMN identified by the global RAN node. In response to the judgment result being different, it is determined that the user terminal is switched across PLMNs; in response to the judgment result being the same, it is determined that the user terminal is switched within the system.

[0120] Optionally, the acquisition module includes a second acquisition unit.

[0121] The second acquisition unit is used to determine whether the capability level of the user terminal supports the preset capability level, and in response to the user terminal supporting the preset capability level, obtain the slice information sent by the network after registration and carried by the user terminal. The second acquisition unit is also used to obtain the slice information of the user terminal according to the S-NSSAI of the target PLMN, the S-NSSAI of the source PLMN of the allowed NSSAI in the user subscription data saved when the user terminal is registered, and the corresponding S-NSSAI of the target PLMN mapped with the allowed NSSAI in response to the user terminal being unable to support the preset capability level. Or, the second acquisition unit is also used to query the roaming agreement locally configured by the AMF according to the S-NSSAI of the target PLMN of the allowed NSSAI in response to the user terminal being unable to support the preset capability level, and determine the mapping relationship between the S-NSSAI of the source PLMN of the allowed NSSAI and the corresponding S-NSSAI of the target PLMN mapped with the allowed NSSAI, so as to obtain the slice information of the user terminal.

[0122] Optionally, the NRF is used to find a matching target AMF set based on the NSSAI of the target PLMN, and the NRF is also used to select a target AMF from the target AMF set based on the target TAI.

[0123] Embodiment 4:

[0124] like Figure 7 The present embodiment provides a device for selecting an AMF for inter-PLMN switching, which is applied to an NRF, including:

[0125] The third receiving module 71 is used to receive the query request sent by the source AMF, wherein the query request includes the slice information and target TAI of the user terminal. Before the source AMF sends the query request, the source AMF is used to determine whether the user terminal is switched across PLMNs. In response to the user terminal switching across PLMNs and when the source PLMN initiates switching as a visited public land mobile network VPLMN, the source AMF is used to obtain the slice information of the user terminal according to the capability level of the user terminal.

[0126] The feedback module 72 is connected to the third receiving module 71, and is used to select the target AMF according to the NSSAI and target TAI of the target PLMN in the slice information, and feed back the target AMF to the source AMF so that the source AMF performs AMF switching to support service continuity of user terminals switched across PLMNs.

[0127] Optionally, the feedback module comprises a selection unit.

[0128] The selection unit is used to find a matching target AMF set according to the NSSAI of the target PLMN, and select the target AMF from the target AMF set according to the target TAI.

[0129] Among them, the specific functions of the source AMF are as described in Example 1 and Example 3 and will not be repeated here.

[0130] Embodiment 5:

[0131] like Figure 8 As shown, this embodiment provides an electronic device, including a memory 81 and a processor 82, wherein the memory 81 stores a computer program, and the processor 82 is configured to run the computer program to implement the AMF selection method for cross-PLMN switching as described in Example 1 or Example 2.

[0132] Embodiment 6:

[0133] This embodiment provides a computer-readable storage medium on which a computer program is stored. When the computer program is executed by a processor, the AMF selection method for inter-PLMN switching as described in Example 1 or Example 2 is implemented.

[0134] The AMF selection device for cross-PLMN switching of Example 3 and Example 4, the electronic device of Example 5, and the computer-readable storage medium of Example 6 are used to obtain the slice information of the user terminal through the capability level of the user terminal when the user terminal is switching across PLMNs and the source PLMN initiates switching for a visited public land mobile network VPLMN, and select a target AMF that better matches the slice information based on the NRF query mechanism, so that the connection state service of the user terminal continues, avoiding the situation where the service is interrupted due to the inaccurate selection of the target AMF and the inability to meet the service capabilities of the user terminal. Furthermore, the source RAN determines whether the user terminal is switching across PLMNs, and sends the result identifier corresponding to the judgment result to the source AMF. The source AMF is used to directly determine whether the user terminal is switching across PLMNs based on the received result identifier, which can save the computing resources of the source AMF and improve the efficiency of the target AMF selection. The source AMF determines whether the user terminal is switching across PLMNs by itself, which can ensure the accuracy of the judgment result of the cross-PLMN switching. In addition, the S-NSSAI of the VPLMN of the UE's allowed NSSAI and the corresponding S-NSSAI of the HPLMN mapped with the allowed NSSAI are used to find the appropriate AMF, which can improve the accuracy of the target AMF selection. Finally, the T-AMF obtained according to the target PLMN+NSSAI and TAI information will greatly increase the accuracy of the AMF during handover, reduce QoE and QoS issues such as dropped calls, and better meet SLA.

[0135] It is to be understood that the above embodiments are merely exemplary embodiments used to illustrate the principles of the present invention, but the present invention is not limited thereto. For those of ordinary skill in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. A method for selecting an access and mobility management function AMF for handover across a public land mobile network PLMN, applied to a source AMF, characterized in that: The method comprises: Determine whether the user terminal is switched across PLMNs; In response to the user terminal performing inter-PLMN handover and initiating handover when the source PLMN is a visited public land mobile network VPLMN, acquiring slice information of the user terminal according to a capability level of the user terminal; Send a query request to the network element service storage function NRF, where the query request includes the slice information of the user terminal and the target tracking area identifier TAI, so that the NRF selects the target AMF according to the NSSAI of the target PLMN and the target TAI in the slice information; The target AMF receives NRF feedback and performs AMF switching to support service continuity of user terminals switched across PLMNs.

2. The method according to claim 1, characterized in that Cross-PLMN switching includes one of the following: national roaming, shared network, different network roaming, core network roaming, The slice information includes the single network slice selection assistance information S-NSSAI of the source PLMN of the allowed network slice selection assistance information NSSAI of the user terminal and the NSSAI of the target PLMN mapped with the allowed NSSAI.

3. The method according to claim 1, characterized in that Before determining whether the user terminal is switched across PLMNs, the method further includes: Receive a handover request sent by a source NG-RAN, wherein the handover request includes a result identifier of the source NG-RAN determining whether the user terminal is an inter-PLMN handover.

4. The method according to claim 1, characterized in that: The determining whether the user terminal is switched across PLMNs specifically includes: Obtain the target TAI, cell ID, and global RAN node ID in the handover request; Determine whether the PLMN identified by the target TAI or cell is the same as the PLMN identified by the global RAN node; In response to the determination result being different, determining that the user terminal is switched across PLMNs; In response to the determination result being the same, it is determined that the user terminal is switched within the system.

5. The method according to claim 4, characterized in that The acquiring slice information of the user terminal according to the capability level of the user terminal specifically includes: Determine whether the capability level of the user terminal supports the preset capability level; In response to the user terminal supporting a preset capability level, obtaining slice information sent by the network after registration and carried by the user terminal; In response to the user terminal being unable to support the preset capability level, acquiring slice information of the user terminal according to the S-NSSAI of the target PLMN, the S-NSSAI of the source PLMN of the allowed NSSAI in the user subscription data saved when the user terminal is registered, and the corresponding S-NSSAI of the target PLMN mapped with the allowed NSSAI; Or, in response to the user terminal being unable to support a preset capability level, the roaming agreement locally configured by the AMF is queried according to the S-NSSAI of the target PLMN of the allowed NSSAI, and the mapping relationship between the S-NSSAI of the source PLMN of the allowed NSSAI and the corresponding S-NSSAI of the target PLMN mapped with the allowed NSSAI is determined to obtain the slice information of the user terminal.

6. A method for selecting an AMF for inter-PLMN handover, characterized in that: Applied to NRF, the method comprises: Receive a query request sent by the source AMF, where the query request includes the slice information and the target TAI of the user terminal. Before the source AMF sends the query request, the source AMF determines whether the user terminal is switched across PLMNs. In response to the user terminal switching across PLMNs and when the source PLMN is a visited public land mobile network VPLMN initiating the switch, the source AMF obtains the slice information of the user terminal according to the capability level of the user terminal; Select the target AMF based on the NSSAI and target TAI of the target PLMN in the slice information; The target AMF is fed back to the source AMF so that the source AMF performs AMF switching to support service continuity of user terminals switched across PLMNs.

7. The method according to claim 6, characterized in that Cross-PLMN switching includes one of the following: national roaming, shared network, different network roaming, core network roaming, The slice information includes the single network slice selection assistance information S-NSSAI of the source PLMN of the allowed network slice selection assistance information NSSAI of the user terminal and the NSSAI of the target PLMN mapped with the allowed NSSAI.

8. The method according to claim 6, characterized in that The target AMF is selected according to the NSSAI and target TAI of the target PLMN in the slice information, including: Find the matching target AMF set based on the NSSAI of the target PLMN; Select the target AMF from the target AMF set according to the target TAI.

9. A device for selecting an AMF for inter-PLMN handover, characterized in that: include: A judgment module is used to judge whether the user terminal is switched across PLMNs. The acquisition module is connected to the judgment module, and is used to obtain the slice information of the user terminal according to the capability level of the user terminal in response to the user terminal switching across PLMNs and the switching being initiated when the source PLMN is a visited public land mobile network VPLMN, A sending module is connected to the acquisition module and is used to send a query request to the NRF, wherein the query request includes the slice information and the target TAI of the user terminal, so that the NRF selects the target AMF according to the NSSAI and the target TAI of the target PLMN in the slice information, The first receiving module is used to receive the target AMF fed back by the NRF and perform AMF switching to support service continuity of user terminals switched across PLMNs.

10. The device according to claim 9, characterized in that Cross-PLMN switching includes one of the following: national roaming, shared network, different network roaming, core network roaming, The slice information includes the single network slice selection assistance information S-NSSAI of the source PLMN of the allowed network slice selection assistance information NSSAI of the user terminal and the NSSAI of the target PLMN mapped with the allowed NSSAI.

11. The device according to claim 9, characterized in that Also includes a second receiving module, The second receiving module is used to receive a handover request sent by a source NG-RAN, wherein the handover request includes a result identifier of the source NG-RAN determining whether the user terminal is an inter-PLMN handover.

12. The device according to claim 9, characterized in that The judging module includes a first obtaining unit and a second judging unit. The first acquisition unit is configured to acquire a target TAI, a cell identifier, and a global RAN node identifier in a handover request. The second judgment unit is connected to the first acquisition unit, and is used to judge whether the PLMN identified by the target TAI or cell is the same as the PLMN identified by the global RAN node. In response to the judgment result being different, it is determined that the user terminal is switched across PLMNs; in response to the judgment result being the same, it is determined that the user terminal is switched within the system.

13. The device according to claim 12, characterized in that The acquisition module includes a second acquisition unit, The second acquisition unit is used to determine whether the capability level of the user terminal supports the preset capability level, and in response to the user terminal supporting the preset capability level, acquire the slice information sent by the network after registration and carried by the user terminal, The second acquisition unit is further configured to, in response to the user terminal being unable to support the preset capability level, acquire the slice information of the user terminal according to the S-NSSAI of the target PLMN, the S-NSSAI of the source PLMN of the allowed NSSAI in the user subscription data saved when the user terminal is registered, and the corresponding S-NSSAI of the target PLMN mapped with the allowed NSSAI, Or, the second acquisition unit is also used to query the roaming agreement locally configured by the AMF according to the S-NSSAI of the target PLMN of the allowed NSSAI in response to the user terminal being unable to support the preset capability level, and determine the mapping relationship between the S-NSSAI of the source PLMN of the allowed NSSAI and the corresponding S-NSSAI of the target PLMN mapped with the allowed NSSAI, so as to obtain the slice information of the user terminal.

14. A device for selecting an AMF for inter-PLMN handover, characterized in that: include: The third receiving module is used to receive a query request sent by the source AMF, wherein the query request includes the slice information and the target TAI of the user terminal. Before the source AMF sends the query request, the source AMF is used to determine whether the user terminal is switched across PLMNs. In response to the user terminal switching across PLMNs and when the source PLMN initiates switching as a visited public land mobile network VPLMN, the source AMF is used to obtain the slice information of the user terminal according to the capability level of the user terminal. The feedback module is connected to the third receiving module and is used to select the target AMF according to the NSSAI and target TAI of the target PLMN in the slice information, and feed back the target AMF to the source AMF so that the source AMF performs AMF switching and supports service continuity of user terminals switched across PLMNs.

15. The device according to claim 14, characterized in that The feedback module includes a selection unit, The selection unit is used to find a matching target AMF set according to the NSSAI of the target PLMN, and select the target AMF from the target AMF set according to the target TAI.

16. An electronic device, characterized in that: It includes a memory and a processor, wherein the memory stores a computer program, and the processor is configured to run the computer program to implement the AMF selection method for cross-PLMN switching as described in any one of claims 1-5 or claims 6-8.

17. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the method for selecting an AMF for inter-PLMN switching as described in any one of claims 1-5 or claims 6-8 is implemented.

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