Communication methods, devices, and systems

Abstract

This application provides a communication method, apparatus, and system. The method includes the following. The visited policy control network element updates a first service parameter to a second service parameter based on a mapping relationship between first network slice identification information of the visited network and second network slice identification information of the home network. The first service parameter includes the first network slice identification information of the visited network, and the second service parameter includes the second network slice identification information of the home network. The visited policy control network element sends the second service parameter to the home policy control network element, and the second service parameter is used to determine a user routing selection policy for the terminal device. The technical solution of this application helps to generate a user routing selection policy for the terminal device so that the terminal device can normally access the services of the visited network.

Description

Technical Field

[0001] [Cross - reference to Related Applications] This application claims the priority of Chinese Patent Application No. 202210699286.1, titled "NETWORK SLICE INFORMATION DETERMINING METHOD, APPARATUS, AND SYSTEM", filed with the China National Intellectual Property Administration on June 20, 2022, and Chinese Patent Application No. 202310143598.9, titled "COMMUNICATION METHOD, APPARATUS, AND SYSTEM", filed with the China National Intellectual Property Administration on February 9, 2023, and the entire contents of these applications are incorporated herein by reference.

[0002] [Technical Field] This application relates to the field of communications, and more specifically, to communication methods, apparatuses, and systems.

Background Art

[0003] To meet diverse requirements and the isolation between slices, fifth-generation (5G) network slicing technology provides a network environment that is isolated from each other for different application scenarios by virtualizing independent logical networks on the same network infrastructure, thereby allowing network functions and characteristics to be customized for different application scenarios based on their respective requirements. When network slices are deployed to the core network, if user equipment (UE) (e.g., terminal devices) needs to access a slice, the UE may provide requested network slice selection assistance information (Requested NSSAI) to the core network, thereby causing the core network to select a public data network (PDN) network route selection policy (URSP) for the UE. According to the URSP, the network side may control the UE to create a session associated with a specific application / specific type of application, thereby allowing the UE to access the application's services by using the session. Typically, the URSP is generated by the home public land mobile network (HPLMN) network. The network needs to know the attribute information of the session associated with the application in advance and generate URSPs based on that information.

[0004] When a UE is in a roaming scenario, some applications may be temporarily deployed to a visited public land mobile network (VPLMN). However, since the HPLMN is unaware of information regarding these applications, the policy control network element (PCF) (abbreviated as V-PCF) within the VPLMN needs to provide some UE policy assistance information corresponding to the visited location of the PCF (abbreviated as H-PCF) within the HPLMN. For example, the assistance information may include data network name (DNN), session and service continuity (SSC) mode, network slice information, etc., associated with some applications deployed within the VPLMN. The network slice information included in the UE policy assistance information corresponding to the visited location is single-network slice selection assistance information (S-NSSAI) within the VPLMN. In the process of generating the URSP, the H-PCF may comprehensively consider the UE policy assistance information corresponding to the visited location and transmitted by the V-PCF. Thus, the optimal URSP is determined for the roaming UE, and the roaming UE can access several applications deployed in the VPLMN by using the extended URSP. However, after the support information from the V-PCF is placed into the extended URSP, some S-NSSAIs within the URSP are HPLMN values, and some S-NSSAIs within the URSP are VPLMN values ​​(the VPLMN values ​​are from the V-PCF). This affects the UE's use of the URSP. Therefore, the VPLMN S-NSSAIs included in the support information need to be mapped to HPLMN S-NSSAIs. [Overview of the project]

[0005] This application provides a communication method, apparatus, and system for obtaining a mapping relationship between the destination network slice identification information of a terminal device and the home network slice identification information of a terminal device. This helps generate a user route selection policy for a terminal device so that the terminal device can successfully access services on the destination network.

[0006] According to the first embodiment, a communication method is determined which includes the following: The destination policy control network element updates a first service parameter to a second service parameter based on a mapping relationship between a first network slice identifier of the destination network and a second network slice identifier of the home network, wherein the first service parameter includes the first network slice identifier of the destination network and the second service parameter includes the second network slice identifier of the home network; the destination policy control network element transmits the second service parameter to the home policy control network element, wherein the second service parameter is used to determine a user route selection policy for a terminal device.

[0007] According to the technical solution of this application, service parameters can be updated based on a mapping relationship between the destination network slice identification information of the terminal device and the home network slice identification information of the terminal device. This helps generate a user route selection policy for the terminal device so that the terminal device can successfully access services on the destination network.

[0008] Referring to the first aspect, some implementations of the first aspect further include: The destination policy control network element receives a mapping relationship from the destination mobility management network element.

[0009] Referring to the first aspect, in some implementations of the first aspect, before the mapping relationship is received, the method further includes: The destination policy control network element sends a message to the destination mobility management network element to obtain the mapping relationship.

[0010] Referring to the first embodiment, in some implementations of the first embodiment, the mapping relationship includes a mapping relationship between configured network slice identifiers and home network slice identifiers, determined by the destination location for a terminal device, wherein the configured network slice identifiers include first network slice identifiers and the home network slice identifiers include second network slice identifiers.

[0011] Referring to the first aspect, some other implementations of the first aspect further include: The visited policy control network element obtains mapping relationships from the local configuration.

[0012] Referring to the first embodiment, some other implementations of the first embodiment further include: The destination policy control network element receives identification information of the network slice to which the terminal device subscribes from the destination mobility management network element. Updating the first service parameter to the second service parameter based on the mapping relationship by the destination policy control network element includes: The destination policy control network element updates the first service parameter to the second service parameter based on the mapping relationship and the identification information of the network slice to which the terminal device subscribes.

[0013] Referring to the first aspect, in some other implementations of the first aspect, before the identification information of the network slice to which the terminal device subscribes is received, the method further includes: The destination policy control network element sends a message to the destination mobility management network element to obtain the identification information of the network slice to which the terminal device subscribes.

[0014] Referring to the first aspect, some other implementations of the first aspect further include: The destination policy control network element obtains a first service parameter from the destination unified data repository network element.

[0015] Referring to the first aspect, some implementations of the first aspect further include: a destination policy control network element receives a user route selection policy from a home policy control network element, the destination policy control network element transmits the user route selection policy to a destination mobility management network element, and the user route selection policy is used by a terminal device to access services on the destination network.

[0016] According to a second embodiment, a communication system is provided that includes a destination policy control network element and a home policy control network element. The destination policy control network element is configured to update a first service parameter to a second service parameter based on a mapping relationship between a first network slice identifier of the destination network and a second network slice identifier of the home network, and to transmit the second service parameter to the home policy control network element, wherein the first service parameter includes the first network slice identifier of the destination network, and the second service parameter includes the second network slice identifier of the home network. The home policy control network element is configured to determine a user route selection policy for a terminal device based on the second service parameter, which will be used by the terminal device to access the destination service.

[0017] According to the communication system in this application, service parameters can be updated based on a mapping relationship between the destination network slice identification information of the terminal device and the home network slice identification information of the terminal device. This helps generate a user route selection policy for the terminal device so that the terminal device can successfully access services on the destination network.

[0018] Referring to the second aspect, in some implementations of the second aspect, the system further includes a destination mobility management network element, which is configured to transmit mapping relationships to a destination policy control network element.

[0019] Referring to the second embodiment, in some implementations of the second embodiment, the destination mobility management network element is further configured to receive messages from the destination policy control network element for obtaining mapping relationships.

[0020] Referring to the second embodiment, in some implementations of the second embodiment, the mapping relationship includes a mapping relationship between configured network slice identifiers and home network slice identifiers, determined by the destination location for a terminal device, wherein the configured network slice identifiers include first network slice identifiers and the home network slice identifiers include second network slice identifiers.

[0021] Referring to the second aspect, in some other implementations of the second aspect, the visited policy control network element is further configured to obtain mapping relationships from the local configuration.

[0022] Referring to the second embodiment, in some other implementations of the second embodiment, the destination mobility management network element is further configured to transmit identification information of the network slice to which the terminal device subscribes to the destination policy control network element, and the destination policy control network element is specifically configured to update the first service parameter of the terminal device to a second service parameter based on the mapping relationship and the identification information of the network slice to which the terminal device subscribes.

[0023] Referring to the second embodiment, in some other implementations of the second embodiment, the destination mobility management network element is further configured to receive messages from the destination policy control network element to obtain identification information of the network slice to which the terminal device is subscribed.

[0024] Referring to the second aspect, in some implementations of the second aspect, the system further includes a destination unified data repository network element, the destination unified data repository network element is configured to transmit the first service parameters to the destination policy control network element.

[0025] Referring to the second aspect, in some other implementation manners of the second aspect, the home policy control network element is further configured to send the user root selection policy to the visited policy control network element, and the visited policy control network element is further configured to send the URSP to the visited mobility management network element.

[0026] According to the third aspect, a communication method including the following is provided. The visited policy control network element sends the second service parameter to the home policy control network element, and the second service parameter is obtained by the visited policy control network element by updating the first service parameter based on the mapping relationship between the first network slice identification information of the visited network and the second network slice identification information of the home network. The home policy control network element determines the user root selection policy for the terminal device based on the second service parameter, and the user root selection policy will be used by the terminal device to access the visited service.

[0027] Referring to the third aspect, in some implementation manners of the third aspect, the method further includes the following. The visited policy control network element sends a message for obtaining the mapping relationship to the visited mobility management network element, and the visited mobility management network element sends the mapping relationship to the visited policy control network element based on the message.

[0028] Referring to the third aspect, in some implementation manners of the third aspect, the method further includes the following. The home policy control network element sends the user root selection policy to the visited policy control network element. The visited policy control network element is further configured to send the user root selection policy to the visited mobility management network element.

[0029] According to a fourth aspect, a communication method is provided which includes the following: A first network element transmits first information to a second network element, the first information including identification information of a first network, identification information of a first network slice of a destination network, and identification information of a network slice to which a terminal device subscribes; the first network element receives second information from the second network element, the second information including a mapping relationship between the second network slice identification information of the destination network and the first network slice identification information of the home network, the second network slice identification information of the destination network being a subset of the first network slice identification information of the destination network, the first network slice identification information of the home network being a subset of the identification information of a network slice to which a terminal device subscribes; and the second information is used to determine a user route selection policy URSP for the terminal device. Either the first and second network elements belong to a home network and the first network is a destination network, or the first and second network elements belong to a destination network and the first network is a home network. The second information is determined by the second network element based on the first information. The fact that the second network slice identifier of the visited network is a subset of the first network slice identifier of the visited network may be explained as follows: The second network slice identifier of the visited network includes some or all of the information in the first network slice identifier of the visited network. The fact that the first network slice identifier of the home network is a subset of the identifier of the network slice to which the terminal device subscribes may be explained as follows: The first network slice identifier of the home network includes some or all of the information in the identifier of the network slice to which the terminal device subscribes.

[0030] According to the technical solution of this application, a mapping relationship between the access network slice identification information of the terminal device and the home network slice identification information of the terminal device can be obtained. This helps to generate a URSP for the terminal device so that the terminal device can normally access the services of the access network.

[0031] Referring to the fourth aspect, in some implementation manners of the fourth aspect, the URSP includes the second network slice identification information of the access network. In this way, the terminal device can directly determine the mapping relationship between the access network slice identification information and the home network slice identification information according to the URSP.

[0032] Referring to the fourth aspect, in some implementation manners of the fourth aspect, the first network element and the second network element belong to the home network, and the method further includes the following. The first network element receives third information from the third network element. The third network element belongs to the access network, and the third information includes the first network slice identification information of the access network. The first network element determines the user root selection policy (URSP) of the terminal device based on the second information and the third information. The URSP is to be used by the terminal device to access the services of the access network. The first network element sends the URSP to the third network element.

[0033] Referring to the fourth aspect, some implementations of the fourth aspect further include: a first network element receives fourth information, which indicates updated identification information of the network slice to which the terminal device subscribes; the first network element transmits fifth information to a second network element, which is used to request a mapping relationship between third network slice identification information of a visited network and second network slice identification information of a home network, where third network slice identification information of the visited network is a subset of first network slice identification information of the visited network, and second network slice identification information of the home network is a subset of updated identification information of the network slice to which the terminal device subscribes.

[0034] According to the technical solution of this application, after the identification information of the network slice to which a terminal device subscribes changes or is updated, the mapping relationship between the terminal device's visited network slice identification information and the terminal device's home network slice identification information can be re-obtained based on the updated identification information of the network slice to which the terminal device subscribes. This helps generate a URSP for the terminal device so that the terminal device can successfully access the services of the visited network.

[0035] Referring to the fourth aspect, in some implementations of the fourth aspect, the first network element is a policy control network element belonging to the home network, the second network element is a network slice selection network element belonging to the home network or a mobility management network element belonging to the home network, and the third network element is a policy control network element belonging to the destination network.

[0036] Referring to the fourth aspect, in some other implementations of the fourth aspect, the first and second network elements belong to a visited network, and the method further includes: the first network element transmits second information to the fourth network element, the fourth network element belongs to a home network, and the first network element receives a user route selection policy URSP from the fourth network element, the URSP to be used by the terminal device to access services on the visited network.

[0037] Referring to the fourth aspect, some other implementations of the fourth aspect further include: a first network element receives third information from a third network element, the third network element belongs to a destination network, and the third information includes identification information of the network slice to which the terminal device subscribes.

[0038] Referring to the fourth aspect, some other implementations of the fourth aspect further include: a first network element receives fourth information from a third network element, the third network element belonging to a visited network, the fourth information comprising updated identification information of the network slice to which the terminal device subscribes; the first network element transmits fifth information to a second network element, the fifth information used to request a mapping relationship between the third network slice identification information of the visited network and the second network slice identification information of the home network, the third network slice identification information of the visited network being a subset of the first network slice identification information of the visited network, and the second network slice identification information of the home network being a subset of updated identification information of the network slice to which the terminal device subscribes.

[0039] Referring to the fourth aspect, in some other implementations of the fourth aspect, the first network element is a policy control network element belonging to the visited network, the second network element is a network slice selection network element or a mobility management network element belonging to the visited network, the third network element is a mobility management network element belonging to the visited network, and the fourth network element is a policy control network element belonging to the home network.

[0040] According to a fifth aspect, a communication method is provided which includes the following: A second network element receives first information from a first network element, the first information including identification information of a first network, identification information of a first network slice of a destination network, and identification information of a network slice to which a terminal device subscribes; the second network element transmits second information to the first network element, the second information including a mapping relationship between the second network slice identification information of the destination network of the terminal device and the first network slice identification information of the home network of the terminal device, the second network slice identification information of the destination network being a subset of the first network slice identification information of the destination network, the first network slice identification information of the home network being a subset of the identification information of a network slice to which the terminal device subscribes; and the second information is used to determine a user route selection policy URSP for the terminal device. The first network element and the second network element belong to the terminal device's home network, and the first network is the terminal device's visited network, or the first network element and the second network element belong to the terminal device's visited network, and the first network is the terminal device's home network.

[0041] According to the technical solution of this application, a mapping relationship can be obtained between the destination network slice identification information of a terminal device and the home network slice identification information of a terminal device. This helps to generate a URSP for the terminal device so that the terminal device can successfully access the services of the destination network.

[0042] Referring to the fifth aspect, in some implementations of the fifth aspect, the URSP includes a second network slice identifier of the visited network.

[0043] Referring to the fifth aspect, in some implementations of the fifth aspect, the first network element and the second network element belong to a home network, and the method further includes: The second network element determines the second information based on the first information.

[0044] Referring to the fifth aspect, some implementations of the fifth aspect further include: a second network element receives fifth information from the first network element, the fifth information indicating updated identification information of the network slice to which the terminal device subscribes; the second network element transmits sixth information to the first network element, the sixth information including a mapping relationship between third network slice identification information of the visited network and second network slice identification information of the home network, where third network slice identification information of the visited network is a subset of first network slice identification information of the visited network, and second network slice identification information of the home network is a subset of updated identification information of the network slice to which the terminal device subscribes.

[0045] Referring to the fifth aspect, in some implementations of the fifth aspect, the first network element is a policy control network element belonging to the home network, and the second network element is a network slice selection network element or a mobility management network element belonging to the home network.

[0046] Referring to the fifth aspect, in some other implementations of the fifth aspect, the first network element is a policy control network element belonging to the destination network, and the second network element is a network slice selection network element or a mobility management network element belonging to the destination network.

[0047] According to the sixth aspect, a communication method is provided which includes the following: A first network element transmits first information to a second network element, the first information including identification information of a home network and first network slice identification information of a visited network; the first and second network elements belong to a visited network; the first network element receives second information from the second network element, the second information including a mapping relationship between the first network slice identification information of the visited network and the first network slice identification information of the home network.

[0048] According to the technical solution of this application, a mapping relationship can be obtained between the destination network slice identification information and the home network slice identification information. This helps generate a URSP for the terminal device so that the terminal device can successfully access the services of the destination network.

[0049] Referring to the sixth aspect, some implementations of the sixth aspect further include: a first network element transmits second information to a third network element, the third network element belonging to a home network; the first network element receives from the third network element a user route selection policy URSP for a terminal device determined based on the second information, the URSP to be used by the terminal device to access services on a visited network.

[0050] Referring to the sixth aspect, in some implementations of the sixth aspect, the URSP includes a second network slice identifier of the destination network of the terminal device, the second network slice identifier of the destination network being a subset of the first network slice identifier of the destination network.

[0051] Referring to the sixth aspect, some implementations of the sixth aspect further include: the first network element transmits third information to the third network element, the third information includes first network slice identifier information of the network visited by the terminal device.

[0052] Referring to the sixth aspect, in some implementations of the sixth aspect, the first network element is a policy control network element belonging to the visited network, the second network element is a network slice selection network element or a mobility management network element belonging to the visited network, and the third network element is a policy control network element belonging to the home network.

[0053] According to the seventh aspect, a communication method is provided which includes the following: A third network element receives second information from a first network element, the second information including a mapping relationship between a first network slice identifier of a visited network and a first network slice identifier of a home network, the third network element belongs to the home network and the first network element belongs to the visited network, the third network element transmits a user route selection policy URSP of a terminal device to the first network element, the URSP is to be used by the terminal device to access services of the visited network.

[0054] According to the technical solution of this application, a mapping relationship can be obtained between the destination network slice identification information and the home network slice identification information. This helps generate a URSP for the terminal device so that the terminal device can successfully access the services of the destination network.

[0055] Referring to the seventh aspect, some implementations of the seventh aspect further include: a third network element obtains identification information of the network slice to which the terminal device is subscribed; the third network element determines the URSP of the terminal device based on the second information and the identification information of the network slice to which the terminal device is subscribed; the URSP includes second network slice identification information of the destination network of the terminal device, the second network slice identification information of the destination network being a subset of the first network slice identification information of the destination network.

[0056] Referring to the seventh aspect, some implementations of the seventh aspect further include: a third network element obtains updated identification information of the network slice to which the terminal device subscribes; and the third network element determines the updated URSP of the terminal device based on the second information and the updated identification information of the network slice to which the terminal device subscribes.

[0057] Referring to the seventh aspect, some implementations of the seventh aspect further include: the third network element transmits the updated URSP of the terminal device to the first network element.

[0058] Referring to the seventh aspect, in some implementations of the seventh aspect, the first network element is a policy control network element belonging to the visited network, the second network element is a network slice selection network element or a mobility management network element belonging to the visited network, and the third network element is a policy control network element belonging to the home network.

[0059] According to the eighth aspect, a communication device is provided configured to implement the above method. The communication device may be a policy control entity as described in the first to seventh aspects, or a device including a policy control entity, or the communication device may be a network slice selection entity or mobility management entity as described in the first to seventh aspects, or a device including a network slice selection entity or mobility management entity. The communication device includes corresponding modules, units, or means for implementing the above method. The modules, units, or means may be implemented by hardware, software, or hardware running the corresponding software. The hardware or software includes one or more modules or units corresponding to the above function.

[0060] Referring to the eighth aspect, in some possible implementations, the communication device may include a processing module and a transceiver module. The transceiver module may also be called a transceiver unit and is configured to implement the transmit and / or receive functions in any one of the above aspects and any one of the possible implementations of the above aspects. The transceiver module may include a transceiver circuit, a transceiver machine, a transceiver, or a communication interface. The processing module may be configured to implement the processing functions in any one of the above aspects and any one of the possible implementations of the above aspects. The processing module may be, for example, a processor.

[0061] Referring to the eighth aspect, in some possible implementations, the transceiver module includes a transmit module and a receive module, respectively, configured to implement the transmit and receive functions in any one of the above aspects and any one of the possible implementations of the above aspects.

[0062] According to the ninth aspect, a communication device including a processor is provided. The processor is coupled to memory and configured to read instructions in memory and then execute the method in any one of the above aspects according to the instructions. The communication device may be a policy control entity in the first to seventh aspects, or a device including a policy control entity, or the communication device may be a network slice selection entity or mobility management entity in the first to seventh aspects, or a device including a network slice selection entity or mobility management entity.

[0063] Referring to the ninth aspect, in possible implementations, the communication device further includes a memory, which is configured to store necessary program instructions and data.

[0064] Referring to the ninth aspect, in possible implementations, the communication device is a chip or a chip system. Optionally, when the communication device is a chip system, it may include a chip, or it may include a chip and other discrete components.

[0065] According to a tenth aspect, a communication device is provided that includes a processor and an interface circuit. The interface circuit is configured to receive a computer program or instruction and to transmit the computer program or instruction to the processor. The processor is configured to execute the computer program or instruction so that the communication device performs the method in any one of the above aspects.

[0066] Referring to the tenth aspect, in possible implementations, the communication device is a chip or a chip system. Optionally, when the communication device is a chip system, the communication device may include a chip, or it may include a chip and other discrete components.

[0067] According to the eleventh aspect, a communication system is provided which includes a first network element and a second network element in the fourth aspect. The first network element is configured to transmit first information to the second network element, the first information including identification information of the first network, first network slice identification information of the visited network, and identification information of the network slice to which the terminal device subscribes. The second network element is configured to transmit second information to the first network element, the second information including a mapping relationship between the second network slice identification information of the visited network and the first network slice identification information of the home network, wherein the second network slice identification information of the visited network is a subset of the first network slice identification information of the visited network, and the first network slice identification information of the home network is a subset of the identification information of the network slice to which the terminal device subscribes, and the second information is used to determine a user route selection policy URSP for the terminal device. The first network element and the second network element belong to the terminal device's home network, and the first network is the terminal device's visited network, or the first network element and the second network element belong to the terminal device's visited network, and the first network is the terminal device's home network.

[0068] Referring to the eleventh aspect, in some implementations of the eleventh aspect, a first network element is a policy control network element belonging to a home network, a second network element is a network slice selection network element or mobility management network element belonging to the home network, and the system further includes a third network element, the third network element is a policy control network element belonging to a destination network. The third network element is configured to transmit third information to the first network element, the third information includes first network slice identification information of the destination network of the terminal device. The first network element transmits the terminal device's user route selection policy URSP to the third network element, the URSP to be used by the terminal device to access services on the destination network.

[0069] Referring to the 11th aspect, in some other implementations of the 11th aspect, the first network element is a policy control network element belonging to the visited network, the second network element is a network slice selection network element or mobility management network element belonging to the visited network, and the system further includes a third network element, the third network element is a mobility management network element belonging to the visited network. The third network element is configured to transmit fourth information to the first network element, the fourth information including updated identification information of the network slice to which the terminal device subscribes. The first network element is further configured to transmit fifth information to the second network element, the fifth information used to request a mapping relationship between the third network slice identification information of the visited network and the second network slice identification information of the home network, where the third network slice identification information of the visited network is a subset of the first network slice identification information of the visited network, and the second network slice identification information of the home network is a subset of updated identification information of the network slice to which the terminal device subscribes.

[0070] Referring to the eleventh aspect, in some other implementations of the eleventh aspect, the system further includes a fourth network element, the fourth network element being a policy control network element belonging to a home network. The fourth network element is configured to receive second information from the first network element and to transmit a user route selection policy URSP for a terminal device to the first network element, the URSP to be used by the terminal device to access services on the visited network.

[0071] According to the twelfth aspect, a communication system is provided. The communication system includes a first network element and a second network element in the sixth aspect. The first network element and the second network element belong to a visited network. The first network element is configured to transmit first information to the second network element, the first information including home network identification information and first network slice identification information of the visited network. The second network element is configured to transmit second information to the first network element, the second information including a mapping relationship between the first network slice identification information of the visited network and the first network slice identification information of the home network.

[0072] Referring to the twelfth aspect, in some implementations of the twelfth aspect, the system further includes a third network element, the third network element belonging to a home network. The third network element is configured to receive second information from the first network element, the second information including a mapping relationship between a first network slice identifier of a visited network and a first network slice identifier of the home network, the third network element belonging to the home network and the first network element belonging to the visited network, and is configured to transmit a user route selection policy URSP for a terminal device to the first network element, the URSP to be used by the terminal device to access services on the visited network. The third network element is further configured to obtain the identifier of the network slice to which the terminal device subscribes, and to determine the URSP for the terminal device based on the second information and the identifier of the network slice to which the terminal device subscribes.

[0073] According to the 13th aspect, a computer program product is provided. The computer program product includes computer program code, and when the computer program code is executed on a computer, the computer becomes capable of performing the method in the above aspect.

[0074] It should be noted that all or part of the computer program code may be stored in a first storage medium. The first storage medium may be packaged together with the processor or packaged separately from the processor. This is not particularly limited in the embodiments of this application.

[0075] According to the fourteenth aspect, a computer-readable medium is provided. The computer-readable medium stores program code, and when the computer program code is executed on a computer, the computer is able to perform the method according to the above aspect.

[0076] According to the 15th aspect, a chip system is provided that includes memory and a processor. The memory is configured to store computer programs, and the processor is configured to call computer programs from memory and execute computer programs, so that a communication device on which the chip system is installed performs a method in any one of the first to seventh aspects and any possible implementations of the first to seventh aspects.

[0077] The chip system may include an input chip or interface configured to transmit information or data, and an output chip or interface configured to receive information or data. [Brief explanation of the drawing]

[0078] [Figure 1] This is a schematic diagram of the system architecture according to the embodiment of this application. [Figure 2] This is a schematic diagram of an example of a communication system to which this application can be applied. [Figure 3] This is a schematic diagram of an example of a service-oriented architecture for a 5G system to which this application may apply. [Figure 4] This is a schematic diagram illustrating an example of a roaming scenario to which this application may apply. [Figure 5] This is a schematic flowchart of an example of a communication method according to this application. [Figure 6] This is a schematic flowchart of the first specific example of the communication method described in this application. [Figure 7] This is a schematic flowchart of a second specific example of the communication method described in this application. [Figure 8] This is a schematic flowchart of a third specific example of the communication method described in this application. [Figure 9] This is a schematic flowchart of another example of the communication method described in this application. [Figure 10] This is a schematic flowchart of a fourth specific example of the communication method described in this application. [Figure 11] This is a schematic flowchart of a fifth specific example of the communication method described in this application. [Figure 12] This is a schematic flowchart of a sixth specific example of the communication method described in this application. [Figure 13] This is a schematic flowchart of the seventh specific example of the communication method described in this application. [Figure 14] This is a schematic block diagram of an example of a communication device according to this application. [Figure 15] This is a schematic block diagram of an example of a communication device according to this application. [Modes for carrying out the invention]

[0079] The technical solution of this application will be described below with reference to the attached drawings.

[0080] Figure 1 is a schematic diagram of the communication system according to this application. As shown in Figure 1, the system includes a first network element 110 and a second network element 120. Optionally, the system 100 may further include a third network element 130 and a fourth network element 140. The system 100 may be configured to perform the communication method according to the embodiments of this application.

[0081] The first network element 110 is configured to transmit first information to the second network element 120, the first information including the identification information of the first network, the first network slice identification information of the visited network, and the identification information of the network slice to which the terminal device subscribes. The second network element 120 is configured to receive second information, the second information including a mapping relationship between the second network slice identification information of the visited network and the first network slice identification information of the home network, the second network slice identification information of the visited network being a subset of the first network slice identification information of the visited network, and the first network slice identification information of the home network being a subset of the identification information of the network slice to which the terminal device subscribes. The second information is used to determine the user route selection policy URSP for the terminal device. The fact that the second network slice identification information of the visited network is a subset of the first network slice identification information of the visited network may be described as follows: The second network slice identification information of the visited network includes some or all of the information within the first network slice identification information of the visited network. The fact that the first network slice identifier of a home network is a subset of the identifier of the network slice to which the terminal device subscribes may also be described as follows: The first network slice identifier of a home network includes some or all of the information within the identifier of the network slice to which the terminal device subscribes.

[0082] The second network element 120 is configured to receive first information from the first network element 110 and to transmit second information to the first network element 110.

[0083] Either the first network element and the second network element belong to the home network and the first network is a visited network, or the first network element and the second network element belong to a visited network and the first network is the home network.

[0084] Optionally, the third network element 130 is configured to transmit third information to the first network element 110, the third information including first network slice identification information of the destination network.

[0085] Optionally, a fourth network element 140 is configured to receive second information from the first network element 110 and send a user route selection policy (URSP) for a terminal device to the first network element 110, which the terminal device will use to access services on the visited network.

[0086] For example, the communication system provided in this application can obtain a mapping relationship between the destination network slice identification information of a terminal device and the home network slice identification information of a terminal device. This helps generate a URSP for the terminal device so that the terminal device can successfully access the services of the destination network.

[0087] The system 100 shown in Figure 1 may be applied to the fifth-generation (5G) network architecture shown in Figure 2 or Figure 3, and obviously may also be applied to future network architectures, such as the sixth-generation (6G) network architecture. This is not particularly limited to the embodiments of this application.

[0088] For example, suppose the communication system shown in Figure 1 is applied to the 5G network shown in Figure 2 or Figure 3. In a possible implementation, the first network element 110 may be a policy control network element (H-PCF) belonging to the home network, the second network element 120 may be a network slice selection network element (HPLMN network slice selection function, H-NSSF) belonging to the home network or a mobility management network element (HPLMN access and mobility management function, H-AMF) belonging to the home network, and the third network element 130 may be a policy control network element (V-PCF) belonging to the visited network. In this implementation, there is no fourth network element 140. In other possible implementations, the first network element 110 may be a policy control network element (V-PCF) belonging to the visited network, the second network element 120 may be a network slice selection network element (V-NSSF) belonging to the visited network, the third network element 130 may be a mobility management network element (V-AMF) belonging to the visited network, and the fourth network element 140 may be a policy control network element (H-PCF) belonging to the home network.

[0089] The following describes 5G systems in different scenarios using examples with reference to Figures 2 and 3. It should be understood that the 5G systems described in this specification are merely examples and should not constitute any limitation to this application.

[0090] Figure 2 is a schematic diagram of the basic architecture of 5G system 200. As shown in Figure 2, system 200 includes PCF, AMF, session management function (SMF), radio access network (RAN), unified data management (UDM), data network (DN), user plane function (UPF), UE, application function (AF), network slice selection function (NSSF), authentication server function (AUSF), etc. Optionally, Figure 2 may further include the following functions (not shown in Figure 2), namely, unified data repository (UDR), network exposure function (NEF), or network repository function (NRF).

[0091] The main functions of the network element are described as follows:

[0092] 1. Terminal device

[0093] The terminal device in this embodiment of the application may be user equipment (UE), mobile station (MS), mobile terminal (MT), access terminal, subscriber unit, subscriber station, mobile station, remote station, remote terminal, mobile device, user terminal, terminal, wireless communication device, user agent, user equipment, etc.

[0094] A terminal device is a device that provides voice and data connectivity to a user, for example, a handheld device or in-vehicle device with wireless connectivity. Currently, some examples of terminals include mobile phones, tablet computers, notebook computers, palmtop computers, mobile internet devices (MIDs), wearable devices, virtual reality (VR) devices, augmented reality (AR) devices, wireless terminals in industrial control, wireless terminals in self-driving or autopilot, wireless terminals in remote medical surgery, wireless terminals in smart grids, wireless terminals in transportation safety, wireless terminals in smart cities, wireless terminals in smart homes, mobile phones, cordless phones, session initiation protocol (SIP) phones, wireless local loop (WLL) stations, and personal digital assistants. Examples include PDAs, handheld devices with wireless communication capabilities, computing devices or other processing devices connected to wireless modems, in-vehicle devices, wearable devices, terminal devices in future 5G networks, terminal devices in future advanced public land mobile networks (PLMNs), etc. This is not limited to the embodiments of this application.

[0095] As an example, and not an limitation, in embodiments of this application, the terminal device may be a wearable device instead. A wearable device may also be called a wearable intelligent device, etc., and is a general term for wearable devices intelligently designed and developed for everyday wear by using wearable technology, such as eyeglasses, gloves, watches, clothing, and shoes. A wearable device is a portable device that is worn directly on the user's body or incorporated into the user's clothing or accessories. A wearable device is not only a hardware device but also achieves powerful functionality through software support, data exchange, and cloud interaction. General-purpose wearable intelligent devices include full-featured large devices that can achieve full or partial functionality without relying on a smartphone, such as smartwatches or smart glasses, and devices that need to work with other devices such as smartphones and focus on only one type of application functionality, such as various smart bands or smart jewelry for monitoring bodily signs. Furthermore, in embodiments of this application, the terminal device may be a terminal device in an Internet of Things (IoT) system instead.

[0096] 2. Wireless Access Network (RAN)

[0097] A wireless access network is an access network that provides network access functions based on wireless communication technology. A wireless access network manages wireless resources, provides wireless access services or air interface access services to terminals, and can transfer control signals and user data between terminals and the core network.

[0098] For example, and not limited to, the wireless access network may be an evolved NodeB (eNB or eNodeB) in an LTE system, or a wireless controller in a cloud radio access network (CRAN) scenario, or the access device may be a relay station, access point, in-vehicle device, wearable device, access device in a 5G network, access device in a future evolved PLMN network, access point (AP) in a WLAN, or gNB in ​​an NR system. This is not limited to the embodiments of this application.

[0099] 3. Access and Mobility Management Function Network Element (AMF)

[0100] The access and mobility management function network element is primarily used for mobility management, access management, etc., and may be configured to implement other functions in mobility management entity (MME) functions other than session management, such as lawful interception or access permission (or authentication), and may be further configured to transfer user policies between the UE and the PCF. In embodiments of this application, the access and mobility management function network element may be configured to implement the functions of the access and mobility management network element.

[0101] 4. Session Management Function Network Element SMF

[0102] Session management function network elements are primarily used for session management, Internet Protocol (IP) address assignment and management of terminal devices, user plane function (UPF) network element selection, policy control and billing function interface termination, downlink data notification, etc. In embodiments of this application, the session management function network element may be configured to implement the functions of a session management network element.

[0103] 5. User Plane Functional Network Element UPF

[0104] User plane functional network elements may be used for packet routing and forwarding, QoS parameter processing of user plane data, etc. User data can reach the data network (DN) through this network element. In embodiments of this application, user plane functional network elements may be configured to implement the functions of user plane network elements. For example, when a session is created on a different UPF, the UE's service experience will also be different. Therefore, the SMF needs to select the appropriate UPF for the UE's session.

[0105] 6. Policy Control Network Element (PCF)

[0106] Policy control network elements are configured to guide a unified policy framework for network behavior and provide policy rule information for control plane function network elements (e.g., AMF network elements or SMF network elements). Policy control network elements primarily handle policy control functions such as session-level and service flow-level billing, QoS bandwidth guarantees and mobility management, and UE policy decisions.

[0107] 7. Network Element (NEF) with Network Publish Function

[0108] The network exposure function network element is configured to expose services and network capability information (such as terminal location and whether a session is reachable) provided by 3GPP network functions to the outside world.

[0109] 8. Application Function Network Element AF

[0110] The application function network element is primarily configured to forward application-side requirements for the network side, such as QoS requirements or user state event joins. The AF may also be a third-party function entity or an application service deployed by an operator, such as an IMS voice call service. When a third-party application function entity interacts with the core network, the NEF may perform further authorization processing. For example, a third-party application function may send a request message directly to the NEF, which determines whether the AF is authorized to send the request message, and if the verification is successful, forwards the request message to the corresponding PCF or Unified Data Management UDM.

[0111] 9. Unified Data Management Network Element (UDM)

[0112] The Unified Data Management Network Element is primarily used for unified data management and supports authentication trust state processing in 3GPP authentication and key agreement mechanisms, user identity processing, access permissions, registration and mobility management, enrollment management, SMS message management, etc.

[0113] 10. Unified Data Repository Network Element (UDR)

[0114] The Unified Data Repository Network element is primarily used for accessing data types such as subscription data, policy data, and application data.

[0115] In the architecture described above, the functionality of the interface is described as follows:

[0116] N7: Represents the interface between PCF and SMF, and is configured to deliver control policies at the PDU session granularity and at the service data flow granularity.

[0117] N15: Represents the interface between PCF and AMF, and is configured to deliver UE policies and access control-related policies.

[0118] N5: Represents the interface between AF and PCF, and is configured to deliver application service requests and report network events.

[0119] N4: Represents the interface between SMF and UPF, and is configured to transfer information between the control plane and the user plane, including the distribution of forwarding rules, QoS control rules, traffic statistics rules, etc., from the control plane to the user plane, and reporting of user plane information.

[0120] N11: Represents the interface between SMF and AMF, and is configured to transfer PDU session tunnel information between RAN and UPF, transfer control messages to be sent to UE, and transfer radio resource control information to be sent to RAN, etc.

[0121] N2 represents the interface between AMF and RAN, and is configured to transfer wireless bearer control information from the core network side to the RAN, etc.

[0122] N1: Represents the interface between AMF and UE, is independent of access, and is configured to send QoS control rules to UE, etc.

[0123] N8: Represents the interface between AMF and UDM, used by AMF to obtain subscription and authentication data related to access and mobility management from UDM, and used by AMF to register the UE's current mobility management-related information with UDM.

[0124] N10: Represents the interface between SMF and UDM. It is used by SMF to retrieve session management-related enrollment data from UDM, and by SMF to register the UE's current session-related information with UDM.

[0125] Furthermore, although not shown in Figure 2, the UDR may also have direct interfaces to the PCF and UDM, which correspond to the N36 interface and the N35 interface, respectively. The N36 interface is used by the PCF to retrieve policy-related enrollment data and application data-related information from the UDR, and the N35 interface is used by the UDM to retrieve user enrollment data information from the UDR.

[0126] The network architecture described above, applicable to the embodiments of this application, is merely an example of a network architecture described in terms of conventional point-to-point and service-oriented architectures, and it should be understood that the network architecture applicable to the embodiments of this application is not limited thereto. Any network architecture capable of realizing the functions of the above network elements is applicable to the embodiments of this application.

[0127] The names of the interfaces between network elements in Figure 2 are merely examples, and it should be understood that interfaces may have other names in a particular implementation. This is not particularly limited in this application. Furthermore, the names of the messages (or signaling) transmitted between the above network elements are merely examples and do not constitute any limitation on the function of the messages.

[0128] It should be noted that network elements may also be called entities, devices, apparatus, modules, etc. This is not particularly limited in this application. Furthermore, in this application, for the sake of ease of understanding and explanation, network elements are omitted in some descriptions. For example, an SMF network element is abbreviated as SMF. In this case, "SMF" should be understood as an SMF network element. The same or similar descriptions are omitted below.

[0129] It can be understood that the network element or function described above may be a network element within a hardware device, a software function running on dedicated hardware, or a virtualization function instantiated on a platform (e.g., a cloud platform). Optionally, the network element or function may be implemented by one device, by multiple devices, or as a single functional module within a single device. This is not particularly limited to the embodiments of this application.

[0130] It should be further understood that in the communication system shown in Figure 2, the functions of the constituent network elements are merely examples. Not all functions of the constituent network elements are necessarily required when applied to embodiments of this application.

[0131] Furthermore, the names of the network elements (PCF and AMF, etc.) included in Figure 2 are merely nominal and do not constitute a limitation on the function of the network elements. In 5G networks and other future networks, the above network elements may have alternative names. This is not particularly limited to the embodiments of this application. For example, in a 6G network, some or all of the above network elements may still use the terminology used in 5G, or they may have other names. A general explanation is provided here. Further details will not be discussed again below.

[0132] The communication between the network elements of the control plane function in Figure 2 is described, for example, by using a non-service-oriented interface, but it should be further noted that this does not constitute a limitation on the scope of protection of the embodiments of this application. Those skilled in the art will understand that the network elements of the control plane function in Figure 2 may, alternatively, communicate with each other through service-oriented interfaces. For example, the external service-oriented interface provided by the AMF may be Namf, the service-oriented interface provided by the SMF may be Nsmf, the external service-oriented interface provided by the UDM may be Nudm, the service-oriented interface provided by the AF may be Naf, and the external service-oriented interface provided by the PCF may be Npcf.

[0133] The network elements in Figure 2 represent a reference point-based architecture and do not constitute a limitation to embodiments of this application. Figure 3 is a schematic diagram of a service-oriented interface-based architecture. As shown in Figure 3, the architecture includes NSSF, AUSF, UDM, NEF, NRF, PCF, AF, AMF, SMF, UE, RAN, UPF, DN, etc. In Figure 3, the external service-oriented interface provided by NSSF may be Nnssf, the external service-oriented interface provided by NEF may be Nnef, the external service-oriented interface provided by NRF may be Nnrf, the external service-oriented interface provided by AMF may be Namf, the service-oriented interface provided by SMF may be Nsmf, the external service-oriented interface provided by UDM may be Nudm, the service-oriented interface provided by AF may be Naf, the external service-oriented interface provided by PCF may be Npcf, the external service-oriented interface provided by AUSF may be Nausf, and the external service-oriented interface provided by CHF may be Nchf. The interface between the control plane function and either the RAN or UPF is a non-service-oriented interface. The UE is connected to the AMF via the N1 interface, and the UE is connected to the RAN using the radio resource control (RRC) protocol. The RAN is connected to the AMF via the N2 interface, and the RAN is connected to the UPF via the N3 interface. The UPF is connected to the DN via the N6 interface, and the UPF is connected to the SMF via the N4 interface. For further details, refer to the 5G system architecture in the standard. For brevity, the connectivity relationships in architecture 300 are not described here.

[0134] In the 5G era, hundreds of billions of Internet of Things devices will access the network, and different types of application scenarios will have different requirements for the network, some of which may even conflict. Therefore, if a single network is used to serve different types of application scenarios simultaneously, the network architecture becomes extremely complex, resulting in low network management efficiency and resource utilization. 5G network slicing technology provides a network environment that is isolated from each other for different application scenarios by virtualizing independent logical networks on the same network infrastructure. As a result, network functions and characteristics can be customized for different application scenarios based on their respective requirements, and the quality of service (QoS) requirements for different services can be effectively ensured.

[0135] When a network slice is deployed to the core network, the network slice selection process is triggered when a UE is first attached to the network. The slice selection process depends on the UE's join data, local configuration information, roaming agreements, operator policies, etc. In the network slice selection process, the above parameters must be comprehensively considered to select the optimal slice type for the UE.

[0136] Network slice identifiers include S-NSSAI and NSSAI. S-NSSAI represents support information for a single slice and typically includes slice / service type (SST) and slice differentiator (SD). SST is used to characterize the slice in terms of characteristics and services. SD is used to distinguish between different network slices that have the same SST characteristics. NSSAI is a set of S-NSSAI, and multiple network slices may be identified by using NSSAI. In 5G networks, NSSAI may be configured NSSAI, requested NSSAI, or allowed NSSAI.

[0137] When a UE needs to access a slice, the UE may provide the core network with a request NSSAI, which in turn allows the core network to select a network slice instance for the UE. Specifically, the UE may provide the core network with Network Slice Selection Assistance Information (NSSAI) containing a group of parameters, which the core network then selects for the UE.

[0138] The UE registration procedure may be described simply as follows: The UE sends a registration request to the AMF via the RAN, and the AMF retrieves the UE's enrollment data from the UDM based on the UE identifier, and the UDM may retrieve the enrollment data from the UDR after receiving the request. Furthermore, the AMF may separately initiate a User Policy Control Create Request (UE PolicyControl_Create) and an Access Management Policy Control Create Request (AM PolicyControl_Create) to the PCF to obtain the UE policy and access control policy separately. In this process, the PCF returns the UE policy and access control policy to the AMF, and the AMF provides the UE policy and access control policy to the UE.

[0139] The session creation procedure may be briefly described as follows: The UE sends a session creation request to the AMF via the RAN, the AMF selects an SMF for the session to provide services for the session, the AMF remembers the correspondence between the SMF and the PDU session, sends a session creation request to the SMF, the SMF selects the corresponding UPF for the UE, establishes a user plane transmission path, and the SMF assigns an IP address to the UE. In this process, the SMF further initiates a policy control session creation request to the PCF to create a policy control session between the SMF and the PCF. In the policy control session creation process, the SMF remembers the correspondence between the policy control session and the PDU session. Furthermore, the AF may create an AF session with the PCF, and the PCF binds the AF session to the policy control session.

[0140] Figure 4 is a diagram illustrating an exemplary application scenario of a roaming scenario to which this application may apply. The scenario includes at least an AMF, PCF, and UDR located in the VPLMN (referred to as V-AMF, V-PCF, and V-UDR, respectively) and a PCF located in the HPLMN (referred to as H-PCF). In the architecture shown in Figure 4, the network elements may communicate with each other through service-oriented interfaces. For further details, refer to the explanation in Figure 2 or Figure 3. For brevity, further details will not be explained again here.

[0141] S410: V-AMF determines that the UE will roam and register with VPLMN.

[0142] S420: V-AMF sends the first request message to V-PCF.

[0143] The first request message may also be a User Policy Control Create Request (Npcf_UEPolicyControl Create Request), which is used to request V-PCF to create a UE Policy Association.

[0144] S430:V-PCF retrieves UE policy support information corresponding to the visited location.

[0145] The UE policy support information corresponding to the visited location may also be VPLMN-supported UE policy information, and the information may include DNN, SSC mode, network slice information, etc., associated with the application deployed at the visited location. The network slice may be represented by the VPLMN S-NSSAI at the visited location. The V-PCF may obtain VPLMN-supported UE policy information in multiple ways. For example, the V-PCF may obtain VPLMN-supported UE policy information from the V-UDR. As another example, the VPLMN-supported UE policy information is configured locally in the V-PCF.

[0146] S440: V-PCF sends a second request message to H-PCF.

[0147] The second request message may also be a User Policy Control Create Request (Npcf_UEPolicyControl Create Request), which contains VPLMN-assisted UE policy information and is used to request H-PCF to create a UE Policy Association.

[0148] S450: H-PCF sends a second response message to V-PCF.

[0149] The second response message may also be a User Policy Control Create Response (Npcf_UEPolicyControl Create Response), which specifically includes a URSP generated by H-PCF for the UE based on VPLMN-assisted UE policy information.

[0150] S460: V-PCF sends the first response message to V-AMF.

[0151] The format and content of the first response message may be the same as those of the second response message, i.e., the first response message includes URSP.

[0152] When H-PCF receives VPLMN-assisted UE policy information, it can be understood that H-PCF will comprehensively generate a URSP by further considering information about the visited location. After V-AMF sends the URSP to the UE, the UE may decide how to access the services deployed at the visited location according to the URSP.

[0153] However, since the network slice information included in the VPLMN-supported UE policy information is VPLMN S-NSSAI, if H-PCF directly includes the VPLMN S-NSSAI included in the VPLMN-supported UE policy information in the URSP, the URSP will include both VPLMN S-NSSAI and HPLMN S-NSSAI. As a result, the UE cannot accurately identify which S-NSSAI is the visited S-NSSAI and which S-NSSAI is the HPLMN S-NSSAI. Therefore, the VPLMN S-NSSAI included in the URSP needs to be mapped to an HPLMN S-NSSAI that can be accurately identified by the UE.

[0154] Based on this, this application provides a communication method and apparatus for obtaining a mapping relationship between a UE's visited network slice identification information and a UE's home network slice identification information. This helps generate a URSP for the UE so that the UE can successfully access the services of the visited network.

[0155] Figure 5 is a schematic flowchart of an example of a communication method according to this application. Referring to the following steps, the communication method 500 is applied to the network architecture shown in Figures 2 to 4.

[0156] S510: The first network element 110 transmits first information to the second network element 120, the first information including the identification information of the first network, the identification information of the first network slice of the destination network, and the identification information of the network slice to which the terminal device is subscribed.

[0157] Either the first network element and the second network element belong to the home network and the first network is a visited network, or the first network element and the second network element belong to a visited network and the first network is the home network.

[0158] S520: The first network element 110 receives second information from the second network element 120, the second information including a mapping relationship between the second network slice identification information of the visited network and the first network slice identification information of the home network.

[0159] The second network slice identifier of the visited network is a subset of the first network slice identifier of the visited network, and the first network slice identifier of the home network is a subset of the identifier of the network slice to which the terminal device subscribes. The second information is used to determine the user route selection policy URSP for the terminal device. The fact that the second network slice identifier of the visited network is a subset of the first network slice identifier of the visited network may be explained as follows: The second network slice identifier of the visited network includes some or all of the information within the first network slice identifier of the visited network. The fact that the first network slice identifier of the home network is a subset of the identifier of the network slice to which the terminal device subscribes may be explained as follows: The first network slice identifier of the home network includes some or all of the information within the identifier of the network slice to which the terminal device subscribes.

[0160] Optionally, the URSP includes a second network slice identifier for the visited network. In this way, the terminal device can directly determine the mapping relationship between the visited network slice identifier and the home network slice identifier according to the URSP.

[0161] In possible implementations, the system in this application may further include a third network element 130, indicated by a dashed line in Figure 1, but not a fourth network element 140, indicated by a dashed line in Figure 1. When the first network element 110 is a policy control network element belonging to the home network, the second network element 120 is a network slice selection network element belonging to the home network or a mobility management network element belonging to the home network, and the third network element is a policy control network element belonging to the visited network, the first network element 110 may further receive third information from the third network element 130, the third information including first network slice identification information of the visited network. Based on the second and third information, the first network element determines a user route selection policy URSP for the terminal device, which will be used by the terminal device to access services on the visited network. The first network element 110 may further transmit the URSP to the third network element 130.

[0162] Optionally, in the above implementation, the first network element 110 may further receive fourth information, which indicates the updated identification information of the network slice to which the terminal device subscribes. The first network element 110 then transmits fifth information to the second network element 120, which is used to request a mapping relationship between the third network slice identification information of the visited network and the second network slice identification information of the home network. The third network slice identification information of the visited network is a subset of the first network slice identification information of the visited network, and the second network slice identification information of the home network is a subset of the updated identification information of the network slice to which the terminal device subscribes. In this way, after the identification information of the network slice to which the terminal device subscribes changes or is updated, the mapping relationship between the terminal device's visited network slice identification information and the terminal device's home network slice identification information can be re-obtained based on the updated identification information of the network slice to which the terminal device subscribes. This helps generate a URSP for the terminal device so that the terminal device can successfully access the services of the visited network.

[0163] In other possible implementations, the system in this application may further include both a third network element 130 and a fourth network element 140, indicated by the dashed line in Figure 1. When the first network element 110 is a policy control network element belonging to a destination network, the second network element 120 is a network slice selection network element belonging to a destination network, the third network element 130 is a mobility management network element belonging to a destination network, and the fourth network element 140 is a policy control network element belonging to a home network, the first network element 110 may further receive third information from the third network element 130, the third information including identification information of the network slice to which the terminal device subscribes. Thus, the first network element 110 may obtain identification information of the network slice to which the terminal device subscribes, and thereby filter the first network slice identification information of the destination based on the identification information of the network slice to which the terminal device subscribes to obtain second network slice identification information of the destination suitable for the terminal device.

[0164] Optionally, in the above implementation, the first network element 110 receives fourth information from the third network element 130, the third information including updated identification information of the network slice to which the terminal device subscribes; the first network element 110 transmits fifth information to the second network element 120, the fifth information used to request a mapping relationship between the third network slice identification information of the visited network and the second network slice identification information of the home network, the third network slice identification information of the visited network being a subset of the first network slice identification information of the visited network, and the second network slice identification information of the home network being a subset of the updated identification information of the network slice to which the terminal device subscribes. In this way, after the identification information of the network slice to which the terminal device subscribes changes or is updated, the mapping relationship between the terminal device's visited network slice identification information and the terminal device's home network slice identification information can be re-obtained based on the updated identification information of the network slice to which the terminal device subscribes. This helps generate a URSP for the terminal device so that the terminal device can successfully access the services of the visited network.

[0165] According to the technical solution of this application, a mapping relationship can be obtained between the destination network slice identification information of a terminal device and the home network slice identification information of a terminal device. This helps to generate a URSP for the terminal device so that the terminal device can successfully access the services of the destination network.

[0166] Figure 6 is a schematic flowchart of a first specific example of the communication method according to this application. In the method shown in Figure 6, the communication method provided in this embodiment of the application is presented using an example in which the first network element 110 is a policy control network element (H-PCF) belonging to the home network, the second network element 120 is a network slice selection network element (H-NSSF) belonging to the home network, and the third network element 130 is a policy control network element (V-PCF) belonging to the visited network. Alternatively, the second network element 120 may be a mobility management network element (H-AMF) belonging to the home network. This is not limited to this application. In Figure 6, only the example in which the second network element 120 is a network slice selection network element (H-NSSF) belonging to the home network is used for illustrative purposes.

[0167] S601:V-AMF determines that the UE is roaming and registered with the visited network.

[0168] For registering the UE with the visited network, refer to the conventional method. Details will not be explained here. For example, the visited network is VPLMN#1.

[0169] S602: V-AMF sends the first request message to V-PCF.

[0170] Specifically, the first request message may also be a User Policy Control Create Request (Npcf_UEPolicyControl Create Request) and is used to request V-PCF to create a UE Policy Association. Both V-AMF and V-PCF are located on the visited network VPLMN#1. The first request includes the UE's subscription permanent identifier, e.g., the subscription permanent identifier (SUPI).

[0171] S603:V-PCF retrieves UE policy support information corresponding to the visited location.

[0172] Specifically, the UE policy support information corresponding to the visited location may be VPLMN-supported UE policy information, and the information may include DNN, SSC mode, network slice information, etc., associated with the application deployed at the visited location. The network slice may be represented by the VPLMN S-NSSAI at the visited location. The V-PCF may obtain the VPLMN-supported UE policy information from the V-UDR or from the local configuration. The VPLMN-supported UE policy information may include DNN, SSC mode, and network slice information associated with the application deployed in the VPLMN. The network slice identification information included in the VPLMN-supported UE policy information may be represented by the VPLMN S-NSSAI. [Table 1]

[0173] S604: V-PCF sends a second request message to H-PCF.

[0174] The second request message may also be a User Policy Control Create Request (Npcf_UEPolicyControl Create Request). The second request message is used to request the creation of a UE Policy Association. The second request message includes VPLMN assistant UE policy information corresponding to the visited location. See Table 1 for specific details of the information.

[0175] The V-PCF determines the HPLMN ID of the UE based on the join persistence identifier included in the first request message, and determines the H-PCF identifier based on the HPLMN ID. Furthermore, the second request message may also include the V-PCF identifier (V-PCF ID).

[0176] S605: H-PCF obtains UE subscription information from H-UDR.

[0177] In possible implementations, the H-PCF may send a query request message (Nudr_Query Request) to the H-UDR. The query request message is used to query the H-UDR for UE enrollment information. Correspondingly, the H-UDR may send a query response message (Nudr_Query Response) to the H-PCF. The query response message contains UE enrollment information, which includes information about the network slice to which the UE is enrolled. The information about the network slice to which the UE is enrolled includes HPLMN S-NSSAI. For example, the information about the network slice to which the UE is enrolled may be HPLMN S-NSSAI#A and / or HPLMN S-NSSAI#B.

[0178] S606: H-PCF transmits the first piece of information to H-NSSF.

[0179] Specifically, in possible implementations, the H-PCF sends a request message to the H-NSSF. The request message may be a Slice mapping information Request or a service-oriented operation Nnssf_NSSelection_Get Request, but is not limited to this application. The request message includes first information, which includes the identification information of the visited network (VPLMN ID), the identification information of the first network slice of the visited network, and the identification information of the network slice to which the UE belongs (S-NSSAI).

[0180] Based on step S604, the H-PCF may determine the identifier of the network where the V-PCF is located and determine the identification information (VPLMN ID) of the visited network. For example, according to the above example, the V-PCF is located at VPLMN#1 and the VPLMN ID is VPLMN#1. Based on step S604, the H-PCF may determine the first network slice identification information of the visited network from the UE policy support information (VPLMN assistant UE policy information) corresponding to the visited location. For example, when V-PCF is located at VPLMN#1, as shown in Table 1, the VPLMN-supported UE policy information corresponding to VPLMN#1 includes VPLMN#1 S-NSSAI#1, VPLMN#2 S-NSSAI#2, and VPLMN#3 S-NSSAI#3. Therefore, H-PCF determines that the first network slice identifier of the visited network is VPLMN#1 S-NSSAI#1, VPLMN#2 S-NSSAI#2, and VPLMN#3 S-NSSAI#3.

[0181] H-PCF may obtain UE enrollment information from H-UDR based on step S605. The UE enrollment information includes information about the network slice to which the UE is enrolled, and this information includes HPLMN S-NSSAI. For example, the information about the network slice to which the UE is enrolled may also include HPLMN S-NSSAI#A and HPLMN S-NSSAI#B.

[0182] S607: H-PCF receives second information from H-NSSF.

[0183] The H-NSSF may store a network slice roaming agreement that includes slice mapping relationships between HPLMN and VPLMN. In the implementation, the network slice roaming agreement may be pre-configured in the H-NSSF. For example, the mapping relationship for network slice identification information between HPLMN and VPLMN may be as shown in Table 2. [Table 2]

[0184] H-NSSF may determine second information based on first information, and the second information includes a mapping relationship between the second network slice identifier of the visited network and the first network slice identifier of the home network.

[0185] Example 1: For example, information about the network slice to which a UE belongs may be HPLMN S-NSSAI#A and HPLMN S-NSSAI#B. When the VPLMN ID is VPLMN#1, the first network slice identification information of the visited network includes VPLMN#1 S-NSSAI#1, VPLMN#1 S-NSSAI#2, and VPLMN#1 S-NSSAI#3 (as shown in Table 1). When the identification information of the network slice to which a UE belongs includes HPLMN S-NSSAI#A and HPLMN S-NSSAI#B, the H-NSSF may determine, based on Table 2, that VPLMN#1 S-NSSAI#1 can be mapped to HPLMN S-NSSAI#A and VPLMN#1 S-NSSAI#2 can be mapped to HPLMN S-NSSAI#B. However, while VPLMN#1 S-NSSAI#3 can be mapped to HPLMN S-NSSAI#C, the network slice to which the UE subscribes does not include HPLMN S-NSSAI#C. Therefore, for the UE, access is only available in VPLMN#1 for VPLMN#1, and VPLMN#1 S-NSSAI#2. However, the UE is not permitted to access VPLMN#1 S-NSSAI#3 in VPLMN#1. In Example 1, H-NSSF transmits the mapping relationship (i.e., second information) between the second network slice identifier of the visited network and the first network slice identifier of the home network to H-PCF. The second information includes the mapping relationship between VPLMN#1 S-NSSAI#1 and HPLMN S-NSSAI#A, and the mapping relationship between VPLMN#1 S-NSSAI#2 and HPLMN S-NSSAI#B. In other words, the second network slice identifiers for the visited network are VPLMN#1 S-NSSAI#1 and VPLMN#1 S-NSSAI#2, and the first network slice identifiers for the home network are HPLMN S-NSSAI#A and HPLMN S-NSSAI#B.

[0186] Example 2: For example, information about the network slice to which the UE belongs may be HPLMN S-NSSAI#A, HPLMN S-NSSAI#B, and HPLMN S-NSSAI#C. When the VPLMN ID is VPLMN#1, the first network slice identification information of the visited network includes (as shown in Table 1) VPLMN#1 S-NSSAI#1, VPLMN#1 S-NSSAI#2, and VPLMN#1 S-NSSAI#3. When the identification information of the network slice to which the UE subscribes includes HPLMN S-NSSAI#A, HPLMN S-NSSAI#B, and HPLMN S-NSSAI#C, the H-NSSF may determine, based on Table 2, that VPLMN#1 S-NSSAI#1 can be mapped to HPLMN S-NSSAI#A, VPLMN#1 S-NSSAI#2 can be mapped to HPLMN S-NSSAI#B, and VPLMN#1 S-NSSAI#3 can be mapped to HPLMN S-NSSAI#C. Therefore, for the UE, access to VPLMN#1 S-NSSAI#1, VPLMN#1 S-NSSAI#2, and VPLMN#1 S-NSSAI#3 in VPLMN#1 is permitted. In Example 2, the H-NSSF transmits the mapping relationship (i.e., the second information) between the second network slice identification information of the visited network and the first network slice identification information of the home network to the H-PCF. The second set of information includes the mapping relationships between VPLMN#1 S-NSSAI#1 and HPLMN S-NSSAI#A, between VPLMN#1 S-NSSAI#2 and HPLMN S-NSSAI#B, and between VPLMN#1 S-NSSAI#3 and HPLMN S-NSSAI#C. In other words, the second set of network slice identifiers for the visited network are VPLMN#1 S-NSSAI#1, VPLMN#1 S-NSSAI#2, and VPLMN#1 S-NSSAI#3, while the first set of network slice identifiers for the home network are HPLMN S-NSSAI#A, HPLMN S-NSSAI#B, and HPLMN S-NSSAI#C.

[0187] Example 3: For example, information about the network slice to which the UE belongs may be HPLMN S-NSSAI#B. When the VPLMN ID is VPLMN#1, the first network slice identifier of the visited network includes VPLMN#1 S-NSSAI#1, VPLMN#1 S-NSSAI#2, and VPLMN#1 S-NSSAI#3 (as shown in Table 1). When the identifier of the network slice to which the UE belongs includes only HPLMN S-NSSAI#B, the H-NSSF may determine, based on Table 2, that VPLMN#1 S-NSSAI#2 can be mapped to HPLMN S-NSSAI#B. However, while VPLMN#1 S-NSSAI#1 and VPLMN#1 S-NSSAI#3 can be mapped to HPLMN S-NSSAI#A and HPLMN S-NSSAI#C respectively, the network slice to which the UE subscribes does not include either HPLMN S-NSSAI#A or HPLMN S-NSSAI#C. Therefore, for the UE, access is only permitted for VPLMN#1, specifically VPLMN#1 S-NSSAI#2, but not for VPLMN#1, specifically for VPLMN#1, access is not permitted for either VPLMN#1 S-NSSAI#1 or VPLMN#1 S-NSSAI#3. In Example 3, H-NSSF transmits the mapping relationship (i.e., the second information) between the second network slice identifier of the visited network and the first network slice identifier of the home network to H-PCF. The second information includes the mapping relationship between VPLMN#1 S-NSSAI#2 and HPLMN S-NSSAI#B. In other words, the second network slice identifier for the visited network is VPLMN#1 S-NSSAI#2, and the first network slice identifier for the home network is HPLMN S-NSSAI#B.

[0188] Examples 1 to 3 above show that the second network slice identifier of the visited network and the first network slice identifier of the home network, which are included in the second information determined by H-NSSF, change along with the UE subscription information included in the first information. In Example 1, the first network slice identifier of the visited network includes VPLMN#1 S-NSSAI#1, VPLMN#1 S-NSSAI#2, and VPLMN#1 S-NSSAI#3, and the second network slice identifier of the visited network is VPLMN#1 S-NSSAI#1 and VPLMN#1 S-NSSAI#2. Therefore, the second network slice identifier of the visited network is a subset of the first network slice identifier of the visited network. In Example 2, the first network slice identifier of the visited network includes VPLMN#1 S-NSSAI#1, VPLMN#1 S-NSSAI#2, and VPLMN#1 S-NSSAI#3, and the second network slice identifier of the visited network is VPLMN#1 S-NSSAI#1, VPLMN#1 S-NSSAI#2, and VPLMN#1 S-NSSAI#3. Thus, the second network slice identifier of the visited network is a universal set of the first network slice identifier of the visited network. In embodiments of this application, a universal set is also a type of subset. Therefore, the second network slice identifier of the visited network may still be called a subset of the first network slice identifier of the visited network. In Example 3, the first network slice identifier of the visited network includes VPLMN#1 S-NSSAI#1, VPLMN#1 S-NSSAI#2, and VPLMN#1 S-NSSAI#3, and the second network slice identifier of the visited network is VPLMN#1 S-NSSAI#2. Therefore, the second network slice identifier of the visited network is a subset of the first network slice identifier of the visited network.

[0189] As another example, for the scenario in Example 1, the mapping relationship between the second network slice identifier of the visited network and the first network slice identifier of the home network may be as shown in Table 3-1. For the scenario in Example 2, the mapping relationship between the second network slice identifier of the visited network and the first network slice identifier of the home network may be as shown in Table 3-2. For the scenario in Example 3, the mapping relationship between the second network slice identifier of the visited network and the first network slice identifier of the home network may be as shown in Table 3-3. [Table 3-1] [Table 3-2] [Table 3-3]

[0190] After H-NSSF has determined the second information, H-NSSF may transmit the second information to H-PCF using a response message. In the implementation, the response message may be a network slice mapping information response or a service-oriented operation Nnssf_NSSelection_Get response. This is not limited to the present invention.

[0191] S608:H-PCF generates the UE's URSP.

[0192] H-PCF retrieves UE context policy control data from H-UDR. The UE context policy control data includes DNN, SSC mode, and network slice information associated with the application deployed on the HPLMN, as shown in Table 4-0. The network slice associated with the application deployed on the HPLMN is the HPLMN S-NSSAI, for example, HPLMN S-NSSAI#B. [Table 4-0]

[0193] Specifically, the H-PCF may generate the UE's URSP based on the information in Table 4-0 and Section 2.

[0194] For example, in Example 1, as shown in Table 3-1, the mapping relationships included in the second information are the mapping relationship between VPLMN#1 S-NSSAI#1 and HPLMN S-NSSAI#A, and the mapping relationship between VPLMN#1 S-NSSAI#2 and HPLMN S-NSSAI#B. H-PCF may search for UE policy support information (VPLMN assistant UE policy information) corresponding to the visited locations shown in Table 1 and determine that the generated URSP must not only include information about applications deployed to HPLMN in Table 4-0, but also information about applications deployed to VPLMN, such as Application#1 associated with VPLMN#1 S-NSSAI#1 and Application#2 associated with VPLMN#2 S-NSSAI#2. Since the second information does not include the mapping relationship related to VPLMN#1 S-NSSAI#3, the UE cannot access Application#3 associated with VPLMN#1 S-NSSAI#3 in VPLMN#1. Therefore, the generated URSP does not include Application#3 associated with VPLMN#1 S-NSSAI#3. The generated URSP includes HPLMN S-NSSAI, e.g., HPLMN S-NSSAI#A and HPLMN S-NSSAI#B. Optionally, the generated URSP may further include second network slice identifiers of the visited network, e.g., VPLMN#1 S-NSSAI#1 and VPLMN#1 S-NSSAI#2. For example, in this example, the information included in the URSP may be as shown in Table 4-1. Application#1 and Application#2 are expanded into VPLMN, Application#A is expanded into HPLMN, and the network slice identifier associated with Application#A is HPLMN S-NSSAI#B.

[0195] As another example, in Example 2, as shown in Table 3-2, the second information includes mapping relationships between VPLMN#1 S-NSSAI#1 and HPLMN S-NSSAI#A, between VPLMN#1 S-NSSAI#2 and HPLMN S-NSSAI#B, and between VPLMN#1 S-NSSAI#3 and HPLMN S-NSSAI#C. H-PCF may search for UE policy support information (VPLMN assistant UE policy information) corresponding to the visited locations shown in Table 1 and determine that the generated URSP should not only include information about applications deployed to HPLMN in Table 4-0, but also information about applications deployed to VPLMN, such as Application#1 associated with VPLMN#1 S-NSSAI#1, Application#2 associated with VPLMN#2 S-NSSAI#2, and Application#3 associated with VPLMN#1 S-NSSAI#3. The generated URSP includes HPLMN S-NSSAI, for example, HPLMN S-NSSAI#A, HPLMN S-NSSAI#B, and HPLMN S-NSSAI#C. Optionally, the generated URSP may further include second network slice identifiers of the visited network, for example, VPLMN#1 S-NSSAI#1, VPLMN#1 S-NSSAI#2, and VPLMN#1 S-NSSAI#3. For example, in this example, the information included in the URSP may be as shown in Table 4-2. Application#1, Application#2, and Application#3 are expanded into VPLMN, Application#A is expanded into HPLMN, and the network slice identifier associated with Application#A is HPLMN S-NSSAI#B.

[0196] As another example, in Example 3, as shown in Table 3-3, the second piece of information includes a mapping relationship between VPLMN#1 S-NSSAI#2 and HPLMN S-NSSAI#B. H-PCF may search for UE policy support information (VPLMN assistant UE policy information) corresponding to the visited location shown in Table 1 and determine that the generated URSP should not only include information about applications deployed to the HPLMN in Table 4-0, but also further include information about applications deployed to the VPLMN, such as Application#2 associated with VPLMN#1 S-NSSAI#2. The generated URSP includes the HPLMN S-NSSAI, for example, HPLMN S-NSSAI#B. Optionally, the generated URSP may further include second network slice identification information of the visited network, for example, VPLMN#1 S-NSSAI#2. For example, in this example, the information content included in the URSP may be as shown in Table 4-3. Application#2 is deployed to VPLMN, Application#A is deployed to HPLMN, and the network slice identifier associated with Application#A is HPLMN S-NSSAI#B.

[0197] As can be seen from the example above, the URSP generated by H-PCF changes along with the mapping relationships contained in the second piece of information. [Table 4-1] [Table 4-2] [Table 4-3]

[0198] S609: H-PCF sends a second response message to V-PCF.

[0199] The second response message may be a User Policy Control Create Response message (Npcf_UEPolicyControl Create Response message), and the second response message may include a URSP generated by H-PCF. For example, the URSP generated by H-PCF may be any one of Tables 4-1, 4-2, and 4-3.

[0200] S610: V-PCF sends the first response message to V-AMF.

[0201] The first response message may also be a User Policy Control Create Response message (Npcf_UEPolicyControl Create Response message), and the first response message contains a URSP generated by H-PCF.

[0202] Next, V-AMF sends a URSP to the UE so that the UE can access the services of the visited network. For example, in Example 1 above, the URSP generated by H-PCF is shown in Table 4-1, and the UE may access Application#1 and Application#2 deployed at the visited location according to the URSP. In Example 2 above, the URSP generated by H-PCF is shown in Table 4-2, and the UE may access Application#1, Application#2, and Application#3 deployed at the visited location according to the URSP. In Example 2 above, the URSP generated by H-PCF is shown in Table 4-3, and the UE may access Application#2 deployed at the visited location according to the URSP. For the UE's access to the services of the visited network, refer to prior art. Details are not described here.

[0203] According to the technical solution of this application, a mapping relationship can be obtained between the destination network slice identification information of a terminal device and the home network slice identification information of a terminal device. This helps to generate a URSP for the terminal device so that the terminal device can successfully access the services of the destination network.

[0204] Optionally, when the identification information of the network slice to which the UE belongs changes, this embodiment may further include the following steps:

[0205] S611:H-UDR determines that the identification information for the network slice to which the UE belongs has been updated.

[0206] The updated identification information of the network slices to which the UE belongs is either greater than or less than the unupdated identification information of the network slices to which the UE belongs. This is not limited to the embodiments of this application.

[0207] For example, in Example 1 above, the identification information of the network slice to which the UE originally belonged may be HPLMN S-NSSAI#A and HPLMN S-NSSAI#B, and the updated identification information of the network slice to which the UE belongs may be HPLMN S-NSSAI#B only, or may include HPLMN S-NSSAI#A, HPLMN S-NSSAI#B and HPLMN S-NSSAI#C, or similar.

[0208] S612: The H-PCF receives updated identification information from the H-UDR for the network slice to which the UE is subscribed.

[0209] The H-PCF may receive a notification message (Nudr_DM_Notify) from the H-UDR. The notification message may include a fourth piece of information, which includes updated identification information for the network slice to which the UE subscribes. For example, the updated identification information for the network slice to which the UE subscribes may be updated from HPLMN S-NSSAI#A and HPLMN S-NSSAI#B shown in Example 1 above to HPLMN S-NSSAI#A, HPLMN S-NSSAI#B and HPLMN S-NSSAI#C shown in Example 2 above, or to HPLMN S-NSSAI#B shown in Example 3 above.

[0210] S613: H-PCF transmits the fifth piece of information to H-NSSF.

[0211] Specifically, this process is described in step S606. The fifth piece of information includes the VPLMN ID, the first network slice identifier of the visited network, and the updated identifier of the network slice to which the UE subscribes. The fifth piece of information is used to request a new mapping relationship (i.e., a new mapping relationship between the network slice identifier of the visited network and the network slice identifier of the home network), which is determined based on the updated identifier of the network slice to which the UE subscribes.

[0212] Furthermore, the H-PCF may determine the VPLMN ID based on the V-PCF identifier, and the H-PCF may determine the first network slice identifier of the destination network from the VPLMN assistant UE policy information corresponding to the destination location based on step S604. For a specific explanation, see the explanation in step 606. Details will not be explained again here.

[0213] S614: H-PCF receives the sixth piece of information from H-NSSF.

[0214] Specifically, H-NSSF may determine the sixth information based on the fifth information and transmit the sixth information to H-PCF. For the determination process, see step S607 above. Details will not be explained again here. The sixth information includes a mapping relationship between the third network slice identification information of the visited network and the second network slice identification information of the home network, which is the new mapping relationship in S613.

[0215] Example A: The VPLMN ID is VPLMN#1, and the first network slice identifier of the visited network includes VPLMN#1 S-NSSAI#1, VPLMN#1 S-NSSAI#2, and VPLMN#1 S-NSSAI#3. When the updated identifier of the network slice to which the UE belongs is updated from HPLMN S-NSSAI#A and HPLMN S-NSSAI#B shown in Example 1 to HPLMN S-NSSAI#A, HPLMN S-NSSAI#B, and HPLMN S-NSSAI#C shown in Example 2, the H-NSSF may determine, based on Table 2, that VPLMN#1 S-NSSAI#1 can be mapped to HPLMN S-NSSAI#A, VPLMN#1 S-NSSAI#2 can be mapped to HPLMN S-NSSAI#B, and VPLMN#1 S-NSSAI#3 can be mapped to HPLMN S-NSSAI#C. Therefore, with respect to the UE, the UE is permitted to access VPLMN#1 S-NSSAI#1, VPLMN#1 S-NSSAI#2, and VPLMN#1 S-NSSAI#3 in VPLMN#1. The H-NSSF transmits the mapping relationships (i.e., sixth information) between the third network slice identifier of the visited network and the second network slice identifier of the home network to the H-PCF. The sixth information includes the mapping relationships between VPLMN#1 S-NSSAI#1 and HPLMN S-NSSAI#A, between VPLMN#1 S-NSSAI#2 and HPLMN S-NSSAI#B, and between VPLMN#1 S-NSSAI#3 and HPLMN S-NSSAI#C. In other words, the third network slice identifiers for the visited network are VPLMN#1 S-NSSAI#1, VPLMN#1 S-NSSAI#2, and VPLMN#1 S-NSSAI#3, while the second network slice identifiers for the home network are HPLMN S-NSSAI#A, HPLMN S-NSSAI#B, and HPLMN S-NSSAI#C.The third network slice identifier of the visited network is a subset of the first network slice identifier of the visited network, and the second network slice identifier of the home network is a subset of the updated identifier of the network slice to which the terminal device is subscribed.

[0216] Example B: The VPLMN ID is VPLMN#1, and the first network slice identifier of the visited network includes VPLMN#1 S-NSSAI#1, VPLMN#1 S-NSSAI#2, and VPLMN#1 S-NSSAI#3. When the updated identifier of the network slice to which the UE belongs is updated from HPLMN S-NSSAI#A and HPLMN S-NSSAI#B shown in Example 1 to HPLMN S-NSSAI#B shown in Example 3, the H-NSSF may determine, based on Table 2, that VPLMN#1 S-NSSAI#2 can be mapped to HPLMN S-NSSAI#B. However, while VPLMN#1 S-NSSAI#1 and VPLMN#1 S-NSSAI#3 can be mapped to HPLMN S-NSSAI#A and HPLMN S-NSSAI#C respectively, the updated identification information of the network slice to which the UE subscribes does not include either HPLMN S-NSSAI#A or HPLMN S-NSSAI#C. Therefore, the third network slice identification information of the visited network may be VPLMN#1 S-NSSAI#2, and the second network slice identification information of the home network may be HPLMN S-NSSAI#B. The third network slice identification information of the visited network is a subset of the first network slice identification information of the visited network, and the second network slice identification information of the home network is a subset of the updated identification information of the network slice to which the terminal device subscribes.

[0217] Examples A and B above are intended merely to illustrate the technical solutions of this application and should not be used as limitations on the technical solutions of this application. It should be understood that the updated identification information of the network slice to which the UE subscribes may be one network slice identification information or a combination of multiple network slice identification information. For example, the updated identification information of the network slice to which the UE subscribes may include only HPLMN S-NSSAI#A or only HPLMN S-NSSAI#B. As another example, the updated identification information of the network slice to which the UE subscribes may include HPLMN S-NSSAI#A and HPLMN S-NSSAI#B. As yet another example, the updated identification information of the network slice to which the UE subscribes may include HPLMN S-NSSAI#B and HPLMN S-NSSAI#C.

[0218] S614: H-PCF generates a new URSP based on the sixth piece of information.

[0219] Specifically, for this step, refer to step S608 above.

[0220] For example, in Example A, the new mapping relationships included in the sixth piece of information are the mapping relationship between VPLMN#1 S-NSSAI#1 and HPLMN S-NSSAI#A, the mapping relationship between VPLMN#1 S-NSSAI#2 and HPLMN S-NSSAI#B, and the mapping relationship between VPLMN#1 S-NSSAI#3 and HPLMN S-NSSAI#C. H-PCF may search for UE policy support information (VPLMN assistant UE policy information) corresponding to the visited locations shown in Table 1 and determine that the generated URSP must not only include information about applications deployed to HPLMN in Table 4-0, but also further include information about applications deployed to VPLMN, such as Application#1 associated with VPLMN#1 S-NSSAI#1, Application#2 associated with VPLMN#2 S-NSSAI#2, and Application#3 associated with VPLMN#1 S-NSSAI#3. The generated URSP includes HPLMN S-NSSAI, for example, HPLMN S-NSSAI#A, HPLMN S-NSSAI#B, and HPLMN S-NSSAI#C. Optionally, the generated URSP may further include third network slice identifiers of the visited network, for example, VPLMN#1 S-NSSAI#1, VPLMN#1 S-NSSAI#2, and VPLMN#1 S-NSSAI#3. For example, in this example, the information included in the URSP may be as shown in Table 4-2. Application#1, Application#2, and Application#3 are expanded into VPLMN, Application#A is expanded into HPLMN, and the network slice identifier associated with Application#A is HPLMN S-NSSAI#B.

[0221] As another example, in Example B, the new mapping relationship included in the sixth piece of information is the mapping relationship between VPLMN#1 S-NSSAI#1 and HPLMN S-NSSAI#A. H-PCF may search for UE policy support information (VPLMN assistant UE policy information) corresponding to the visited location shown in Table 1 and determine that the generated URSP must not only include information about applications deployed to HPLMN in Table 4-0, but also further include information about applications deployed to VPLMN, e.g., Application#1 associated with VPLMN#1 S-NSSAI#1. The generated URSP includes HPLMN S-NSSAI, e.g., HPLMN S-NSSAI#A. Optionally, the generated URSP may further include third network slice identification information of the visited network, e.g., VPLMN#1 S-NSSAI#1. For example, in this example, the information content included in the URSP may be as shown in Table 4-3. Application#1 is deployed to VPLMN, Application#A is deployed to HPLMN, and the network slice identifier associated with Application#A is HPLMN S-NSSAI#B.

[0222] Although not shown in the diagram, after generating a new URSP, H-PCF may send the new URSP to V-PCF using a User Policy Control Update Notify Request (Npcf_UEPolicyControl UpdateNotify Request), V-PCF may further send the new URSP to V-AMF using a User Policy Control Update Notify Request (Npcf_UEPolicyControl UpdateNotify Request), and it should be understood that V-AMF sends the URSP to the UE so that the UE can access services on the visited network. For example, V-AMF sends the URSP to the UE using a UE configuration update procedure.

[0223] According to the technical solution of this application, after the identification information of the network slice to which a terminal device subscribes changes or is updated, the mapping relationship between the terminal device's visited network slice identification information and the terminal device's home network slice identification information can be re-obtained based on the updated identification information of the network slice to which the terminal device subscribes. This helps generate a URSP for the terminal device so that the terminal device can successfully access the services of the visited network.

[0224] Figure 7 is a schematic flowchart of a second specific example of the communication method according to this application. In the method shown in Figure 7, the communication method provided in this embodiment of the application is presented using an example in which the first network element 110 is a policy control network element (V-PCF) belonging to the visited network, the second network element 120 is a network slice selection network element (V-NSSF) belonging to the visited network, the third network element 130 is a mobility management network element (V-AMF) belonging to the visited network, and the fourth network element 140 is a policy control network element (H-PCF) belonging to the home network.

[0225] S701:V-NSSF stores the network slice roaming agreement.

[0226] The network slice roaming agreement includes a mapping relationship for network slice identification information between HPLMN and VPLMN. For example, the mapping relationship for network slice identification information between HPLMN and VPLMN may be as shown in Table 5. [Table 5]

[0227] S702:V-AMF determines that the UE is roaming and registered with the visited network.

[0228] S702 is the same as S601, and I won't go into detail here.

[0229] S703: V-AMF sends the first request message to V-PCF.

[0230] The first request message may also be a User Policy Control Create Request (Npcf_UEPolicyControl Create Request) and is used to request V-PCF to create a UE Policy Association. The first request message includes the UE's SUPI and UE enrollment information. The UE enrollment information includes the identification information of the network slice to which the UE is enrolled, and the identification information of the network slice to which the UE is enrolled includes the HPLMN S-NSSAI. For example, the information about the network slice to which the UE is enrolled may be HPLMN S-NSSAI#A and HPLMN S-NSSAI#B.

[0231] Furthermore, the method for obtaining UE enrollment information by V-AMF is as follows: V-AMF may send a query request message (Nudm_SDM_Get Request) to H-UDM, which is used to query UE enrollment information from H-UDM. Correspondingly, H-UDM may send a query response message (Nudm_SDM_Get Response) to V-AMF, which contains the UE enrollment information.

[0232] S704:V-PCF retrieves UE policy support information corresponding to the visited location.

[0233] S704 is the same as S603, and I won't go into detail here again.

[0234] S705: V-PCF transmits the first piece of information to V-NSSF.

[0235] Specifically, in possible implementations, the V-PCF sends a request message to the V-NSSF. The request message may be a Slice mapping information Request or a service-oriented operation Nnssf_NSSelection_Get Request, but is not limited to this application. The request message includes first information, which includes the home network identifier (HPLMN ID), the first network slice identifier of the visited network, and the identifier of the network slice to which the UE subscribes (S-NSSAI).

[0236] V-PCF may determine the UE's home network identifier (HPLMN ID) by using the UE's SUPI. For example, the HPLMN ID may be HPLMN#1. Based on step S704, V-PCF may determine the first network slice identifier of the visited network from the UE policy support information (VPLMN assistant UE policy information) corresponding to the visited location. For example, when V-PCF is located at VPLMN#1, as shown in Table 1, the VPLMN-assisted UE policy information corresponding to VPLMN#1 includes VPLMN#1 S-NSSAI#1, VPLMN#1 S-NSSAI#2, and VPLMN#1 S-NSSAI#3. Therefore, V-PCF determines that the first network slice identifier of the visited network is VPLMN#1 S-NSSAI#1, VPLMN#2 S-NSSAI#2, and VPLMN#3 S-NSSAI#3.

[0237] The V-PCF may determine the identification information of the network slice to which the UE belongs based on step S703. The information regarding the network slice to which the UE belongs includes the HPLMN S-NSSAI. For example, the information regarding the network slice to which the UE belongs may also include HPLMN S-NSSAI#A and HPLMN S-NSSAI#B.

[0238] S706: V-PCF receives second information from V-NSSF.

[0239] V-NSSF may determine second information based on first information, and the second information includes a mapping relationship between the second network slice identifier of the visited network and the first network slice identifier of the home network.

[0240] Example a: For example, the identification information of the network slice to which the UE belongs may be HPLMN S-NSSAI#A and HPLMN S-NSSAI#B. When the VPLMN ID is VPLMN#1, the identification information of the first network slice of the visited network may include VPLMN#1 S-NSSAI#1, VPLMN#1 S-NSSAI#2 and VPLMN#1 S-NSSAI#3 (as shown in Table 5). When the identification information of the network slice to which the UE belongs includes HPLMN S-NSSAI#A and HPLMN S-NSSAI#B, the V-NSSF may determine, based on Table 5, that VPLMN#1 S-NSSAI#1 can be mapped to HPLMN S-NSSAI#A and VPLMN#1 S-NSSAI#2 can be mapped to HPLMN S-NSSAI#B. However, while VPLMN#1 S-NSSAI#3 can be mapped to HPLMN S-NSSAI#C, the network slice to which the UE subscribes does not include HPLMN S-NSSAI#C. Therefore, for the UE, access is only available in VPLMN#1, and VPLMN#1 S-NSSAI#2 is available in VPLMN#1. However, the UE is not permitted to access VPLMN#1 S-NSSAI#3 in VPLMN#1. In example a, V-NSSF transmits the mapping relationship (i.e., second information) between the second network slice identifier of the visited network and the first network slice identifier of the home network to V-PCF. The second information includes the mapping relationship between VPLMN#1 S-NSSAI#1 and HPLMN S-NSSAI#A, and the mapping relationship between VPLMN#1 S-NSSAI#2 and HPLMN S-NSSAI#B. In other words, the second network slice identifiers for the visited network are VPLMN#1 S-NSSAI#1 and VPLMN#1 S-NSSAI#2, and the first network slice identifiers for the home network are HPLMN S-NSSAI#A and HPLMN S-NSSAI#B.

[0241] Example b: For example, information about the network slice to which the UE belongs may be HPLMN S-NSSAI#A, HPLMN S-NSSAI#B, and HPLMN S-NSSAI#C. When the VPLMN ID is VPLMN#1, the first network slice identification information of the visited network includes (as shown in Table 5) VPLMN#1 S-NSSAI#1, VPLMN#1 S-NSSAI#2, and VPLMN#1 S-NSSAI#3. When the identification information of the network slice to which the UE subscribes includes HPLMN S-NSSAI#A, HPLMN S-NSSAI#B, and HPLMN S-NSSAI#C, the V-NSSF may determine, based on Table 5, that VPLMN#1 S-NSSAI#1 can be mapped to HPLMN S-NSSAI#A, VPLMN#1 S-NSSAI#2 can be mapped to HPLMN S-NSSAI#B, and VPLMN#1 S-NSSAI#3 can be mapped to HPLMN S-NSSAI#C. Therefore, for the UE, the UE is permitted to access VPLMN#1 S-NSSAI#1, VPLMN#1 S-NSSAI#2, and VPLMN#1 S-NSSAI#3 in VPLMN#1. In example b, the V-NSSF sends the mapping relationship (i.e., the second information) between the second network slice identification information of the visited network and the first network slice identification information of the home network to the V-PCF. The second set of information includes the mapping relationships between VPLMN#1 S-NSSAI#1 and HPLMN S-NSSAI#A, between VPLMN#1 S-NSSAI#2 and HPLMN S-NSSAI#B, and between VPLMN#1 S-NSSAI#3 and HPLMN S-NSSAI#C. In other words, the second set of network slice identifiers for the visited network are VPLMN#1 S-NSSAI#1, VPLMN#1 S-NSSAI#2, and VPLMN#1 S-NSSAI#3, while the first set of network slice identifiers for the home network are HPLMN S-NSSAI#A, HPLMN S-NSSAI#B, and HPLMN S-NSSAI#C.

[0242] Example c: For example, information about the network slice to which the UE belongs may be HPLMN S-NSSAI#B. When the VPLMN ID is VPLMN#1, the first network slice identifier of the visited network includes VPLMN#1 S-NSSAI#1, VPLMN#1 S-NSSAI#2, and VPLMN#1 S-NSSAI#3 (as shown in Table 5). When the identifier of the network slice to which the UE belongs includes only HPLMN S-NSSAI#B, the V-NSSF may determine, based on Table 2, that VPLMN#1 S-NSSAI#2 can be mapped to HPLMN S-NSSAI#B. However, while VPLMN#1 S-NSSAI#1 and VPLMN#1 S-NSSAI#3 can be mapped to HPLMN S-NSSAI#A and HPLMN S-NSSAI#C respectively, the network slice to which the UE subscribes does not include either HPLMN S-NSSAI#A or HPLMN S-NSSAI#C. Therefore, for the UE, access is only permitted for VPLMN#1 S-NSSAI#2, but not for VPLMN#1 S-NSSAI#1 or VPLMN#1 S-NSSAI#3. In example c, V-NSSF transmits the mapping relationship (i.e., the second information) between the second network slice identifier of the visited network and the first network slice identifier of the home network to V-PCF. The second information includes the mapping relationship between VPLMN#1 S-NSSAI#2 and HPLMN S-NSSAI#B. In other words, the second network slice identifier for the visited network is VPLMN#1 S-NSSAI#2, and the first network slice identifier for the home network is HPLMN S-NSSAI#B.

[0243] From examples a to c above, it can be seen that the second network slice identifier of the destination network and the first network slice identifier of the home network, which are included in the second information determined by V-NSSF, change along with the UE subscription information included in the first information. In example a, the first network slice identifier of the destination network includes VPLMN#1 S-NSSAI#1, VPLMN#1 S-NSSAI#2, and VPLMN#1 S-NSSAI#3, and the second network slice identifier of the destination network is VPLMN#1 S-NSSAI#1 and VPLMN#1 S-NSSAI#2. Therefore, the second network slice identifier of the destination network is a subset of the first network slice identifier of the destination network. In example b, the first network slice identifier of the visited network includes VPLMN#1 S-NSSAI#1, VPLMN#1 S-NSSAI#2, and VPLMN#1 S-NSSAI#3, and the second network slice identifier of the visited network is VPLMN#1 S-NSSAI#1, VPLMN#1 S-NSSAI#2, and VPLMN#1 S-NSSAI#3. Therefore, the second network slice identifier of the visited network is a universal set of the first network slice identifier of the visited network. A universal set is also a type of subset. Therefore, the second network slice identifier of the visited network may still be called a subset of the first network slice identifier of the visited network. In example c, the first network slice identifier of the visited network includes VPLMN#1 S-NSSAI#1, VPLMN#1 S-NSSAI#2, and VPLMN#1 S-NSSAI#3, and the second network slice identifier of the visited network is VPLMN#1 S-NSSAI#2. Therefore, the second network slice identifier of the visited network is a subset of the first network slice identifier of the visited network.

[0244] For example, in the scenario in Example a, the mapping relationship between the second network slice identifier of the visited network and the first network slice identifier of the home network may be as shown in Table 3-1. In the scenario in Example b, the mapping relationship between the second network slice identifier of the visited network and the first network slice identifier of the home network may be as shown in Table 3-2. In the scenario in Example c, the mapping relationship between the second network slice identifier of the visited network and the first network slice identifier of the home network may be as shown in Table 3-3. For brevity, the contents of Tables 3-1, 3-2, and 3-3 are not shown again here.

[0245] After determining the second piece of information, the V-NSSF may transmit the second piece of information to the V-PCF using a response message. In the implementation, the response message may be a network slice mapping information response or a service-oriented operation Nnssf_NSSelection_Get response. This is not limited to the present invention.

[0246] S707: V-PCF sends a second request message to H-PCF.

[0247] The second request message may also be a User Policy Control Create Request (Npcf_UEPolicyControl Create Request). The second request message is used to request the creation of a UE Policy Association. The second request message includes the second information and UE policy support information (VPLMN assistant UE policy information) corresponding to the visited location.

[0248] The V-PCF determines the HPLMN ID of the UE based on the join persistence identifier included in the first request message, and determines the H-PCF identifier based on the HPLMN ID. Furthermore, the second request message may also include the V-PCF identifier (V-PCF ID).

[0249] Optionally, UE policy support information corresponding to the visited location (VPLMN assistant UE policy information) transmitted to H-PCF by V-PCF may be processed by V-PCF. For example, in example a, the second information includes the mapping relationship between VPLMN#1 S-NSSAI#1 and HPLMN S-NSSAI#A, and the mapping relationship between VPLMN#1 S-NSSAI#2 and HPLMN S-NSSAI#B. The second network slice identifiers for the visited network are VPLMN#1 S-NSSAI#1 and VPLMN#1 S-NSSAI#2, and the first network slice identifiers for the home network are HPLMN S-NSSAI#A and HPLMN S-NSSAI#B. When the identification information of the network slice to which the UE belongs includes HPLMN S-NSSAI#A and HPLMN S-NSSAI#B, the V-PCF may filter the UE policy support information corresponding to the visited location (VPLMN assistant UE policy information) based on the identification information of the network slice to which the UE belongs. As shown in Table 1, when the VPLMN ID is VPLMN#1, the VPLMN-assisted UE policy information includes Application#1 associated with VPLMN#1 S-NSSAI#1, Application#2 associated with VPLMN#2 S-NSSAI#2, and Application#3 associated with VPLMN#1 S-NSSAI#3.However, since the identification information of the network slice to which the UE belongs does not include HPLMN S-NSSAI#C which has a mapping relationship with VPLMN#1 S-NSSAI#3, meaning that the UE is not permitted to access VPLMN#1 S-NSSAI#3 in VPLMN#1, in order to reduce signaling overhead and the computational load on the UE, Application#3 associated with VPLMN#1 S-NSSAI#3 may be removed from the VPLMN-assisted UE policy information before the V-PCF sends the VPLMN-assisted UE policy information corresponding to the visited location to the H-PCF. As shown in Table 6-1, in example a, the VPLMN-assisted UE policy information processed by the V-PCF includes only information about Application#1 associated with VPLMN#1 S-NSSAI#1 and information about Application#2 associated with VPLMN#1 S-NSSAI#2.

[0250] As another example, in example c, the second piece of information includes a mapping relationship between VPLMN#1 S-NSSAI#2 and HPLMN S-NSSAI#B. The second network slice identifier for the visited network is VPLMN#1 S-NSSAI#2, and the first network slice identifier for the home network is HPLMN S-NSSAI#B. When the identifier of the network slice to which the UE belongs includes HPLMN S-NSSAI#B, the V-PCF may filter the UE policy support information corresponding to the visited location (VPLMN assistant UE policy information) based on the identifier of the network slice to which the UE belongs. As shown in Table 1, when the VPLMN ID is VPLMN#1, the VPLMN-assisted UE policy information includes Application#1 associated with VPLMN#1 S-NSSAI#1, Application#2 associated with VPLMN#2 S-NSSAI#2, and Application#3 associated with VPLMN#1 S-NSSAI#3. However, since the identification information of the network slice to which the UE belongs does not include either HPLMN S-NSSAI#A, which has a mapping relationship with VPLMN#1 S-NSSAI#1, or HPLMN S-NSSAI#C, which has a mapping relationship with VPLMN#1 S-NSSAI#3, in other words, the UE is not permitted to access either VPLMN#1 S-NSSAI#1 or VPLMN#1 S-NSSAI#3 in VPLMN#1, in order to reduce signaling overhead and the computational load on the UE, Application#1 associated with VPLMN#1 S-NSSAI#1 and Application#3 associated with VPLMN#1 S-NSSAI#3 may be removed from the VPLMN-assisted UE policy information before the V-PCF sends the UE policy support information corresponding to the visited location (VPLMN assistant UE policy information) to the H-PCF.As shown in Table 6-2, in Example a, the VPLMN-supported UE policy information processed by V-PCF includes only information about Application#2 associated with VPLMN#1 S-NSSAI#2.

[0251] In example b, the second information includes the mapping relationships between VPLMN#1 S-NSSAI#1 and HPLMN S-NSSAI#A, between VPLMN#1 S-NSSAI#2 and HPLMN S-NSSAI#B, and between VPLMN#1 S-NSSAI#3 and HPLMN S-NSSAI#C. The second network slice identification information for the visited network is VPLMN#1 S-NSSAI#1, VPLMN#1 S-NSSAI#2, and VPLMN#1 S-NSSAI#3, and the first network slice identification information for the home network is HPLMN S-NSSAI#A, HPLMN S-NSSAI#B, and HPLMN S-NSSAI#C. When the network slice to which the UE belongs may be HPLMN S-NSSAI#A, HPLMN S-NSSAI#B, and HPLMN S-NSSAI#C, the information regarding the network slice to which the UE belongs is exactly the same as the first network slice identification information of the home network. Therefore, the V-PCF does not need to filter the UE policy support information corresponding to the visited location based on the identification information of the network slice to which the UE belongs. In other words, the VPLMN-assisted UE policy information remains unchanged and is still shown in Table 1. In this case, in example b, the VPLMN-assisted UE policy information includes information about Application#1 associated with VPLMN#1 S-NSSAI#1, information about Application#2 associated with VPLMN#1 S-NSSAI#2, and information about Application#3 associated with VPLMN#1 S-NSSAI#3. [Table 6-1] [Table 6-2]

[0252] S708:H-PCF generates the UE's URSP.

[0253] Specifically, for this step, see step S608. The H-PCF may obtain UE context policy control data from the H-UDR. The information contained in the UE context policy control data may be as shown in Table 4-0. The network slice associated with the application deployed on the HPLMN is the HPLMN S-NSSAI, for example, HPLMN S-NSSAI#B.

[0254] H-PCF may generate the UE's URSP based on the information in Table 4-0 and Section 2.

[0255] For example, in the scenario of Example a, the mapping relationships included in the second information are the mapping relationship between VPLMN#1 S-NSSAI#1 and HPLMN S-NSSAI#A, and the mapping relationship between VPLMN#1 S-NSSAI#2 and HPLMN S-NSSAI#B. H-PCF may search for UE policy support information corresponding to the visited location (VPLMN assistant UE policy information) and determine that the generated URSP must not only include information about applications deployed to HPLMN in Table 4-0, but also information about applications deployed to VPLMN, such as Application#1 associated with VPLMN#1 S-NSSAI#1 and Application#2 associated with VPLMN#2 S-NSSAI#2. Since the second information does not include the mapping relationship related to VPLMN#1 S-NSSAI#3, the UE cannot access Application#3 associated with VPLMN#1 S-NSSAI#3 in VPLMN#1. Therefore, the generated URSP does not include Application#3 associated with VPLMN#1 S-NSSAI#3. The generated URSP includes HPLMN S-NSSAI, e.g., HPLMN S-NSSAI#A and HPLMN S-NSSAI#B. Optionally, the generated URSP may further include second network slice identifiers of the visited network, e.g., VPLMN#1 S-NSSAI#1 and VPLMN#1 S-NSSAI#2. In the scenario of Example a, the information included in the URSP may be as shown in Table 4-1. Application#1 and Application#2 are expanded into VPLMN, Application#A is expanded into HPLMN, and the network slice identifier associated with Application#A is HPLMN S-NSSAI#B.

[0256] In the scenario of Example b, the second piece of information includes the mapping relationships between VPLMN#1 S-NSSAI#1 and HPLMN S-NSSAI#A, between VPLMN#1 S-NSSAI#2 and HPLMN S-NSSAI#B, and between VPLMN#1 S-NSSAI#3 and HPLMN S-NSSAI#C. The H-PCF retrieves the UE policy support information (VPLMN assistant UE policy information) corresponding to the visited locations shown in Table 1 and may determine that the generated URSP should not only include information about applications deployed to HPLMN in Table 4-0, but also information about applications deployed to VPLMN, such as Application#1 associated with VPLMN#1 S-NSSAI#1, Application#2 associated with VPLMN#2 S-NSSAI#2, and Application#3 associated with VPLMN#1 S-NSSAI#3. The generated URSP includes HPLMN S-NSSAI, for example, HPLMN S-NSSAI#A, HPLMN S-NSSAI#B, and HPLMN S-NSSAI#C. Optionally, the generated URSP may further include second network slice identifiers of the visited network, for example, VPLMN#1 S-NSSAI#1, VPLMN#1 S-NSSAI#2, and VPLMN#1 S-NSSAI#3. The information included in the URSP may be as shown in Table 4-2. Application#1, Application#2, and Application#3 are expanded into VPLMN, Application#A is expanded into HPLMN, and the network slice identifier associated with Application#A is HPLMN S-NSSAI#B.

[0257] In the scenario of Example c, the second piece of information includes the mapping relationship between VPLMN#1 S-NSSAI#2 and HPLMN S-NSSAI#B. H-PCF may search for UE policy support information corresponding to the visited location (VPLMN assistant UE policy information) and determine that the generated URSP should not only include information about applications deployed to the HPLMN in Table 4-0, but also further include information about applications deployed to the VPLMN, e.g., Application#2 associated with VPLMN#1 S-NSSAI#2. The generated URSP includes the HPLMN S-NSSAI, e.g., HPLMN S-NSSAI#B. Optionally, the generated URSP may further include second network slice identification information of the visited network, e.g., VPLMN#1 S-NSSAI#2. The information content included in the URSP may be as shown in Table 4-3. Application#2 is deployed to VPLMN, Application#A is deployed to HPLMN, and the network slice identifier associated with Application#A is HPLMN S-NSSAI#B.

[0258] S709: V-PCF receives a second response message from H-PCF.

[0259] The second response message may be a User Policy Control Create Response (Npcf_UEPolicyControl Create Response), and the second response message may include a URSP generated by H-PCF. For example, the URSP generated by H-PCF may be any one of Tables 4-1, 4-2, and 4-3.

[0260] S710: V-AMF receives the first response message from V-PCF.

[0261] The first response message may also be a User Policy Control Create Response (Npcf_UEPolicyControl Create Response), and the first response message contains a URSP generated by H-PCF.

[0262] Next, V-AMF sends a URSP to the UE so that the UE can access the services of the visited network. For example, in example a above, the URSP generated by H-PCF is shown in Table 4-1, and the UE may access Application#1 and Application#2 deployed at the visited location according to the URSP. In example b above, the URSP generated by H-PCF is shown in Table 4-2, and the UE may access Application#1, Application#2, and Application#3 deployed at the visited location according to the URSP. In example c above, the URSP generated by H-PCF is shown in Table 4-3, and the UE may access Application#2 deployed at the visited location according to the URSP. For the UE's access to the services of the visited network, refer to prior art. Details are not described here.

[0263] According to the technical solution of this application, a mapping relationship can be obtained between the destination network slice identification information of a terminal device and the home network slice identification information of a terminal device. This helps to generate a URSP for the terminal device so that the terminal device can successfully access the services of the destination network.

[0264] Optionally, when the identification information of the network slice to which the UE belongs changes, this embodiment may further include the following steps:

[0265] S711:V-AMF determines that the identification information for the network slice to which the UE belongs has been updated.

[0266] The updated identification information of the network slice to which the UE subscribes can be more or less than the unupdated identification information of the network slice to which the UE subscribes. This is not limited in the embodiments of this application.

[0267] For example, in the above example a, the identification information of the network slice to which the UE originally subscribed may be HPLMN S-NSSAI#A and HPLMN S-NSSAI#B, and the updated identification information of the network slice to which the UE subscribes may be only HPLMN S-NSSAI#B, may include HPLMN S-NSSAI#A, HPLMN S-NSSAI#B, and HPLMN S-NSSAI#C, or may be similar.

[0268] S712: The V-PCF receives, from the V-AMF, the updated identification information of the network slice to which the UE subscribes.

[0269] The V-PCF may receive a user policy control update request message (Npcf_UEPolicyControl Update Request) from the V-AMF. The update request message may include a fourth piece of information, and the fourth piece of information includes the updated identification information of the network slice to which the UE subscribes. By way of example and not limitation, the updated identification information of the network slice to which the UE subscribes may be updated from HPLMN S-NSSAI#A and HPLMN S-NSSAI#B shown in the above example 1 to HPLMN S-NSSAI#A, HPLMN S-NSSAI#B, and HPLMN S-NSSAI#C shown in the above example 2, or to HPLMN S-NSSAI#B shown in the above example 3.

[0270] Furthermore, the update request message further includes the UE's SUPI.

[0271] S613: The V-PCF sends a fifth piece of information to the V-NSSF.

[0272] Specifically, this process is described in step S705. The fifth piece of information includes the HPLMN ID, the first network slice identifier of the visited network, and the updated identifier of the network slice to which the UE subscribes. The fifth piece of information is used to request a new mapping relationship (i.e., a new mapping relationship between the network slice identifier of the visited network and the network slice identifier of the home network), which is determined based on the updated identifier of the network slice to which the UE subscribes.

[0273] The V-PCF may determine the UE's home network identifier (HPLMN ID) by using the UE's SUPI. For example, the HPLMN ID could be HPLMN#1.

[0274] S714: V-PCF receives the sixth piece of information from V-NSSF.

[0275] Specifically, the V-NSSF may determine the sixth information based on the fifth information and transmit the sixth information to the V-PCF. For the determination process, see step S706 above. Details will not be explained again here. The sixth information includes a mapping relationship between the third network slice identification information of the visited network and the second network slice identification information of the home network, which is the new mapping relationship in S713.

[0276] Example 1: The first network slice identifier of the visited network includes VPLMN#1 S-NSSAI#1, VPLMN#1 S-NSSAI#2, and VPLMN#1 S-NSSAI#3. When the identifier of the network slice to which the UE belongs is updated from HPLMN S-NSSAI#A and HPLMN S-NSSAI#B shown in Example a to HPLMN S-NSSAI#A, HPLMN S-NSSAI#B, and HPLMN S-NSSAI#C shown in Example b, the V-NSSF may determine, based on Table 5, that VPLMN#1 S-NSSAI#1 can be mapped to HPLMN S-NSSAI#A, VPLMN#1 S-NSSAI#2 can be mapped to HPLMN S-NSSAI#B, and VPLMN#1 S-NSSAI#3 can be mapped to HPLMN S-NSSAI#C. Therefore, with respect to the UE, the UE is permitted to access VPLMN#1 S-NSSAI#1, VPLMN#1 S-NSSAI#2, and VPLMN#1 S-NSSAI#3 in VPLMN#1. The V-NSSF transmits the mapping relationships (i.e., sixth information) between the third network slice identifier of the visited network and the second network slice identifier of the home network to the V-PCF. The sixth information includes the mapping relationships between VPLMN#1 S-NSSAI#1 and HPLMN S-NSSAI#A, between VPLMN#1 S-NSSAI#2 and HPLMN S-NSSAI#B, and between VPLMN#1 S-NSSAI#3 and HPLMN S-NSSAI#C. In other words, the third network slice identifiers for the visited network are VPLMN#1 S-NSSAI#1, VPLMN#1 S-NSSAI#2, and VPLMN#1 S-NSSAI#3, while the second network slice identifiers for the home network are HPLMN S-NSSAI#A, HPLMN S-NSSAI#B, and HPLMN S-NSSAI#C.The third network slice identifier of the visited network is a subset of the first network slice identifier of the visited network, and the second network slice identifier of the home network is a subset of the updated identifier of the network slice to which the terminal device is subscribed.

[0277] Example 2: The first network slice identifier of the visited network includes VPLMN#1 S-NSSAI#1, VPLMN#1 S-NSSAI#2, and VPLMN#1 S-NSSAI#3. When the updated identifier of the network slice to which the UE belongs is updated from HPLMN S-NSSAI#A and HPLMN S-NSSAI#B shown in Example a to HPLMN S-NSSAI#B shown in Example c, the V-NSSF may determine, based on Table 2, that VPLMN#1 S-NSSAI#2 can be mapped to HPLMN S-NSSAI#B. However, while VPLMN#1 S-NSSAI#1 and VPLMN#1 S-NSSAI#3 can be mapped to HPLMN S-NSSAI#A and HPLMN S-NSSAI#C respectively, the updated identification information of the network slice to which the UE subscribes does not include either HPLMN S-NSSAI#A or HPLMN S-NSSAI#C. Therefore, the third network slice identification information of the visited network may be VPLMN#1 S-NSSAI#2, and the second network slice identification information of the home network may be HPLMN S-NSSAI#B. The third network slice identification information of the visited network is a subset of the first network slice identification information of the visited network, and the second network slice identification information of the home network is a subset of the updated identification information of the network slice to which the terminal device subscribes.

[0278] Examples 1 and 2 above are intended merely to illustrate the technical solutions of this application and should not be used as limitations on the technical solutions of this application. It should be understood that the updated identification information of the network slice to which the UE subscribes may be one network slice identification information or a combination of multiple network slice identification information. For example, the updated identification information of the network slice to which the UE subscribes may include only HPLMN S-NSSAI#A or only HPLMN S-NSSAI#C. As another example, the updated identification information of the network slice to which the UE subscribes may include HPLMN S-NSSAI#A and HPLMN S-NSSAI#C. As yet another example, the updated identification information of the network slice to which the UE subscribes may include HPLMN S-NSSAI#B and HPLMN S-NSSAI#C.

[0279] S715: VPCF sends a third request message to H-PCF.

[0280] Specifically, the V-PCF may send a third request message to the H-PCF. The third request message may be a User Policy Control Update Request (Npcf_UEPolicyControl Update Request). The update request message includes a sixth piece of information, which includes a mapping relationship between the third network slice identifier of the visited network and the second network slice identifier of the home network.

[0281] S716:H-PCF generates a new URSP based on the sixth piece of information.

[0282] Specifically, for this step, refer to step S708 above.

[0283] For example, in Example 1, the new mapping relationships included in the sixth piece of information are the mapping relationship between VPLMN#1 S-NSSAI#1 and HPLMN S-NSSAI#A, the mapping relationship between VPLMN#1 S-NSSAI#2 and HPLMN S-NSSAI#B, and the mapping relationship between VPLMN#1 S-NSSAI#3 and HPLMN S-NSSAI#C. H-PCF may search for UE policy support information (VPLMN assistant UE policy information) corresponding to the visited locations shown in Table 1 and determine that the generated URSP must not only include information about applications deployed to HPLMN in Table 4-0, but also further include information about applications deployed to VPLMN, such as Application#1 associated with VPLMN#1 S-NSSAI#1, Application#2 associated with VPLMN#2 S-NSSAI#2, and Application#3 associated with VPLMN#1 S-NSSAI#3. The generated URSP includes HPLMN S-NSSAI, for example, HPLMN S-NSSAI#A, HPLMN S-NSSAI#B, and HPLMN S-NSSAI#C. Optionally, the generated URSP may further include third network slice identifiers of the visited network, for example, VPLMN#1 S-NSSAI#1, VPLMN#1 S-NSSAI#2, and VPLMN#1 S-NSSAI#3. For example, in this example, the information included in the URSP may be as shown in Table 4-2. Application#1, Application#2, and Application#3 are expanded into VPLMN, Application#A is expanded into HPLMN, and the network slice identifier associated with Application#A is HPLMN S-NSSAI#B.

[0284] As another example, in Example 2, the new mapping relationship included in the sixth piece of information is the mapping relationship between VPLMN#1 S-NSSAI#1 and HPLMN S-NSSAI#A. H-PCF may search for UE policy support information (VPLMN assistant UE policy information) corresponding to the visited location shown in Table 1 and determine that the generated URSP must not only include information about applications deployed to HPLMN in Table 4-0, but also further include information about applications deployed to VPLMN, e.g., Application#1 associated with VPLMN#1 S-NSSAI#1. The generated URSP includes HPLMN S-NSSAI, e.g., HPLMN S-NSSAI#A. Optionally, the generated URSP may further include third network slice identification information of the visited network, e.g., VPLMN#1 S-NSSAI#1. For example, in this example, the information content included in the URSP may be as shown in Table 4-3. Application#1 is deployed to VPLMN, Application#A is deployed to HPLMN, and the network slice identifier associated with Application#A is HPLMN S-NSSAI#B.

[0285] Although not shown in the diagram, after generating a new URSP, H-PCF may send a third response message to V-PCF. The third response message may be a User Policy Control Update Notify Request (Npcf_UEPolicyControl UpdateNotify Request) message, which contains the new URSP. V-PCF may further send the new URSP to V-AMF using the User Policy Control Update Notify Request (Npcf_UEPolicyControl UpdateNotify Request) message, and it should be understood that V-AMF sends the URSP to the UE so that the UE can access the services of the visited network. For example, V-AMF sends the URSP to the UE using the UE configuration update procedure.

[0286] According to the technical solution of this application, after the identification information of the network slice to which a terminal device subscribes changes or is updated, the mapping relationship between the terminal device's visited network slice identification information and the terminal device's home network slice identification information can be re-obtained based on the updated identification information of the network slice to which the terminal device subscribes. This helps generate a URSP for the terminal device so that the terminal device can successfully access the services of the visited network.

[0287] Figure 8 is a schematic flowchart of a third specific example of the communication method according to this application. In the method shown in Figure 8, the communication method provided in this embodiment of the application is presented using an example in which the first network element 110 is a policy control network element (V-PCF) belonging to the visited network, the second network element 120 is a network slice selection network element (V-NSSF) belonging to the visited network, and the third network element 130 is a policy control network element (H-PCF) belonging to the home network. Alternatively, the second network element 120 may be a mobility management network element (V-AMF) belonging to the visited network. This is not limited to this application. In Figure 8, only the example in which the second network element 120 is a network slice selection network element (H-NSSF) belonging to the visited network is used for illustrative purposes.

[0288] S801:V-NSSF stores the network slice roaming agreement.

[0289] S801 is the same as S701, and I won't go into detail here.

[0290] S802:V-AMF determines that the UE is roaming and registered with the visited network.

[0291] S802 is the same as S702 and will not be described again here in detail.

[0292] S803: V-AMF sends the first request message to V-PCF.

[0293] The first request message may be a user policy control creation request message (Npcf_UEPolicyControl Create Request) and is used to request V-PCF to create a UE policy association. The first request message includes the SUPI of the UE. Different from the case of S703, the first request message does not include the identification information of the network slice to which the UE subscribes.

[0294] S804: V-PCF obtains the UE policy support information corresponding to the visited location.

[0295] S804 is the same as S704 and will not be described again here in detail.

[0296] S805: V-PCF sends the first information to V-NSSF.

[0297] Specifically, in a possible implementation manner, V-PCF sends a request message to V-NSSF. The request message may be a network slice mapping information request message (Slice mapping information Request) or a service-oriented operation Nnssf_NSSelection_Get Request. This is not limited in this application. The request message includes the first information. The first information includes the identification information of the home network (HPLMN ID) and the first network slice identification information of the visited network.

[0298] V-PCF may determine the UE's home network identifier (HPLMN ID) by using the UE's SUPI. For example, the HPLMN ID may be HPLMN#1. Based on step S804, V-PCF may determine the first network slice identifier of the visited network from the UE policy support information (VPLMN assistant UE policy information) corresponding to the visited location. For example, when the V-PCF's visited network identifier VPLMN ID is VPLMN#1, the first network slice identifier of the visited network may be VPLMN#1 S-NSSAI#1, VPLMN#1 S-NSSAI#2, and VPLMN#1 S-NSSAI#3.

[0299] S806: V-PCF receives second information from V-NSSF.

[0300] V-NSSF may determine second information based on first information, and the second information includes a mapping relationship between the first network slice identification information of the visited network and the first network slice identification information of the home network.

[0301] For example, the first network slice identifier of the visited network includes VPLMN#1 S-NSSAI#1, VPLMN#1 S-NSSAI#2, and VPLMN#1 S-NSSAI#3 (as shown in Table 7), and the first network slice identifier of the home location includes HPLMN S-NSSAI#A, HPLMN S-NSSAI#B, and HPLMN S-NSSAI#C. In this case, V-NSSF may determine, based on Table 5, that VPLMN#1 S-NSSAI#1 can be mapped to HPLMN S-NSSAI#A, VPLMN#1 S-NSSAI#2 can be mapped to HPLMN S-NSSAI#B, and VPLMN#1 S-NSSAI#3 can be mapped to HPLMN S-NSSAI#C. Therefore, V-NSSF transmits the mapping relationship (i.e., second information) between the first network slice identifier of the visited network and the first network slice identifier of the home network to V-PCF. As shown in Table 7, the second set of information includes the mapping relationships between VPLMN#1 S-NSSAI#1 and HPLMN S-NSSAI#A, between VPLMN#1 S-NSSAI#2 and HPLMN S-NSSAI#B, and between VPLMN#1 S-NSSAI#3 and HPLMN S-NSSAI#C. [Table 7]

[0302] After determining the second piece of information, the V-NSSF may transmit the second piece of information to the V-PCF using a response message. In the implementation, the response message may be a network slice mapping information response or a service-oriented operation Nnssf_NSSelection_Get response. This is not limited to the present invention.

[0303] S807: V-PCF sends a second request message to H-PCF.

[0304] The second request message may also be a User Policy Control Create Request (Npcf_UEPolicyControl Create Request). The second request message is used to request the creation of a UE Policy Association. The second request message includes the second information and UE policy support information (VPLMN assistant UE policy information) corresponding to the visited location.

[0305] The V-PCF determines the HPLMN ID of the UE based on the join persistence identifier included in the first request message, and determines the H-PCF identifier based on the HPLMN ID. Furthermore, the second request message may also include the V-PCF identifier (V-PCF ID).

[0306] S808:H-PCF retrieves the identification information of the network slice to which the UE belongs.

[0307] Specifically, the H-PCF may obtain identification information of the network slice to which the UE is subscribed from the H-UDR. For example, the H-PCF may send a query request message (Nudr_Query Request) to the H-UDR, which is used to query the H-UDR for UE subscription information. Correspondingly, the H-UDR may send a query response message (Nudr_Query Response) to the H-PCF. The query response message contains UE subscription information, which contains information about the network slice to which the UE is subscribed, and this information contains HPLMN S-NSSAI. For example, the information about the network slice to which the UE is subscribed may be HPLMN S-NSSAI#A, HPLMN S-NSSAI#B and / or HPLMN S-NSSAI#C.

[0308] S809:H-PCF generates the UE's URSP.

[0309] H-PCF retrieves UE context policy control data from H-UDR. The UE context policy control data includes DNN, SSC mode, and network slice information associated with the application deployed on the HPLMN, as shown in Table 4-0. The network slice associated with the application deployed on the HPLMN is the HPLMN S-NSSAI, for example, HPLMN S-NSSAI#B.

[0310] Specifically, the H-PCF may first determine a second network slice identifier for the destination network that can be used to generate the URSP, based on the second information and the identifier of the network slice to which the UE is subscribed, and then generate the UE's URSP based on the second network slice identifier for the destination network and Table 4-0.

[0311] Example M: ​​The second set of information includes the mapping relationships between VPLMN#1 S-NSSAI#1 and HPLMN S-NSSAI#A, between VPLMN#1 S-NSSAI#2 and HPLMN S-NSSAI#B, and between VPLMN#1 S-NSSAI#3 and HPLMN S-NSSAI#C, and the information regarding the network slice to which the UE belongs is HPLMN S-NSSAI#A and HPLMN S-NSSAI#B. In this case, H-PCF may determine that the second network slice identifiers of the visited network are VPLMN#1 S-NSSAI#1 and VPLMN#1 S-NSSAI#2. Therefore, the second network slice identifiers of the visited network are a subset of the first network slice identifiers of the visited network. After determining the second network slice identifier of the visited network, H-PCF may look up VPLMN-supported UE policy information and determine that the generated URSP must not only include information about applications deployed to HPLMN in Table 4-0, but also information about applications deployed to VPLMN, such as Application#1 associated with VPLMN#1 S-NSSAI#1 and Application#2 associated with VPLMN#2 S-NSSAI#2. Since the information about the network slice to which the UE belongs does not include HPLMN#1 S-NSSAI#C, the UE cannot access Application#3 associated with VPLMN#1 S-NSSAI#3 in VPLMN#1 (a mapping relationship exists between VPLMN#1 S-NSSAI#3 and HPLMN#1 S-NSSAI#C). Therefore, the generated URSP does not include Application#3 associated with VPLMN#1 S-NSSAI#3. The generated URSP includes HPLMN S-NSSAI, for example, HPLMN S-NSSAI#A and HPLMN S-NSSAI#B.Optionally, the generated URSP may further include second network slice identifiers of the visited network, such as VPLMN#1 S-NSSAI#1 and VPLMN#1 S-NSSAI#2. For example, in this example, the information included in the URSP may be as shown in Table 4-1. Application#1 and Application#2 are expanded into VPLMN, Application#A is expanded into HPLMN, and the network slice identifier associated with Application#A is HPLMN S-NSSAI#B.

[0312] Example N: The second set of information includes the mapping relationships between VPLMN#1 S-NSSAI#1 and HPLMN S-NSSAI#A, between VPLMN#1 S-NSSAI#2 and HPLMN S-NSSAI#B, and between VPLMN#1 S-NSSAI#3 and HPLMN S-NSSAI#C, and the network slices to which the UE subscribes are HPLMN S-NSSAI#A, HPLMN S-NSSAI#B, and HPLMN S-NSSAI#C. In this case, the H-PCF may determine that the second network slice identifiers of the visited network are VPLMN#1 S-NSSAI#1, VPLMN#1 S-NSSAI#2, and VPLMN#1 S-NSSAI#3. Therefore, the second network slice identifiers of the visited network are a subset of the first network slice identifiers of the visited network. After determining the second network slice identifier of the destination network, the H-PCF may search for UE policy assistance information (VPLMN assistant UE policy information) corresponding to the destination location and determine that the generated URSP must not only include information about applications deployed to HPLMN in Table 4-0, but also information about applications deployed to VPLMN, such as Application#1 associated with VPLMN#1 S-NSSAI#1, Application#2 associated with VPLMN#2 S-NSSAI#2, and Application#3 associated with VPLMN#1 S-NSSAI#3. The generated URSP includes HPLMN S-NSSAI, such as HPLMN S-NSSAI#A, HPLMN S-NSSAI#B, and HPLMN S-NSSAI#C. Optionally, the generated URSP may further include second network slice identification information of the visited network, such as VPLMN#1 S-NSSAI#1, VPLMN#1 S-NSSAI#2, and VPLMN#1 S-NSSAI#3. For example, in this example, the information content included in the URSP may be as shown in Table 4-2.Application#1, Application#2, and Application#3 are deployed to VPLMN, Application#A is deployed to HPLMN, and the network slice identifier associated with Application#A is HPLMN S-NSSAI#B.

[0313] Example Q: The second piece of information includes the mapping relationships between VPLMN#1 S-NSSAI#1 and HPLMN S-NSSAI#A, between VPLMN#1 S-NSSAI#2 and HPLMN S-NSSAI#B, and between VPLMN#1 S-NSSAI#3 and HPLMN S-NSSAI#C, and the information regarding the network slice to which the UE belongs is HPLMN S-NSSAI#B. In this case, H-PCF may determine that the second network slice identifier for the visited network is VPLMN#1 S-NSSAI#2. After determining the second network slice identifier for the visited network, H-PCF may search for UE policy support information (VPLMN assistant UE policy information) corresponding to the visited location and determine that the generated URSP should not only include information about applications deployed to HPLMN in Table 4-0, but also further include information about applications deployed to VPLMN, such as Application#2 associated with VPLMN#1 S-NSSAI#2. The generated URSP includes HPLMN S-NSSAI, for example, HPLMN S-NSSAI#B. Optionally, the generated URSP may further include a second network slice identifier for the visited network, for example, VPLMN#1 S-NSSAI#2. For example, in this example, the information included in the URSP may be as shown in Table 4-3. Application#2 is expanded into VPLMN, Application#A is expanded into HPLMN, and the network slice identifier associated with Application#A is HPLMN S-NSSAI#B.

[0314] As can be seen from the example above, the URSP generated by H-PCF changes along with the mapping relationships contained in the second piece of information.

[0315] S810: V-PCF receives a second response message from H-PCF.

[0316] The second response message may be a User Policy Control Create Response (Npcf_UEPolicyControl Create Response), and the second response message may include a URSP generated by H-PCF. For example, the URSP generated by H-PCF may be any one of Tables 4-1, 4-2, and 4-3.

[0317] S811: V-AMF receives the first response message from V-PCF.

[0318] The first response message may also be a User Policy Control Create Response (Npcf_UEPolicyControl Create Response), and the first response message contains a URSP generated by H-PCF.

[0319] Next, V-AMF sends a URSP to the UE so that the UE can access the services of the visited network. For example, in Example M above, the URSP generated by H-PCF is shown in Table 4-1, and the UE may access Application#1 and Application#2 deployed at the visited location according to the URSP. In Example N above, the URSP generated by H-PCF is shown in Table 4-2, and the UE may access Application#1, Application#2, and Application#3 deployed at the visited location according to the URSP. In Example Q above, the URSP generated by H-PCF is shown in Table 4-3, and the UE may access Application#2 deployed at the visited location according to the URSP. For the UE's access to the services of the visited network, refer to prior art. Details are not described here.

[0320] According to the technical solution of this application, a mapping relationship can be obtained between the destination network slice identification information of a terminal device and the home network slice identification information of a terminal device. This helps to generate a URSP for the terminal device so that the terminal device can successfully access the services of the destination network.

[0321] Optionally, when the identification information of the network slice to which the UE belongs changes, this embodiment may further include the following steps:

[0322] S812:H-UDR determines that the identification information for the network slice to which the UE belongs has been updated.

[0323] The updated identification information of the network slices to which the UE belongs is either greater than or less than the unupdated identification information of the network slices to which the UE belongs. This is not limited to the embodiments of this application.

[0324] For example, in example M above, the identification information of the network slice to which the UE originally belonged may be HPLMN S-NSSAI#A and HPLMN S-NSSAI#B, and the updated identification information of the network slice to which the UE belongs may be HPLMN S-NSSAI#B only, or may include HPLMN S-NSSAI#A, HPLMN S-NSSAI#B and HPLMN S-NSSAI#C, or similar.

[0325] S813: The H-PCF receives updated identification information from the H-UDR for the network slice to which the UE is subscribed.

[0326] The H-PCF may receive a notification message (Nudr_DM_Notify) from the H-UDR. The notification message may include a third piece of information, which includes updated identification information for the network slice to which the UE subscribes. For example, the updated identification information for the network slice to which the UE subscribes may be updated from HPLMN S-NSSAI#A and HPLMN S-NSSAI#B shown in Example M above to HPLMN S-NSSAI#A, HPLMN S-NSSAI#B and HPLMN S-NSSAI#C shown in Example N above, or to HPLMN S-NSSAI#B shown in Example Q above.

[0327] S814: H-PCF generates a new URSP.

[0328] For this process, refer to step S809 above.

[0329] Example X: The second piece of information includes the mapping relationships between VPLMN#1 S-NSSAI#1 and HPLMN S-NSSAI#A, between VPLMN#1 S-NSSAI#2 and HPLMN S-NSSAI#B, and between VPLMN#1 S-NSSAI#3 and HPLMN S-NSSAI#C. When the updated identification information of the network slice to which the UE belongs is updated from HPLMN S-NSSAI#A and HPLMN S-NSSAI#B shown in Example M above to HPLMN S-NSSAI#A, HPLMN S-NSSAI#B and HPLMN S-NSSAI#C shown in Example N above, the H-PCF may look up UE policy support information (VPLMN assistant UE policy information) corresponding to the visited location and determine that the generated URSP must not only include information about applications deployed to HPLMN in Table 4-0, but also information about applications deployed to VPLMN, such as Application#1 associated with VPLMN#1 S-NSSAI#1, Application#2 associated with VPLMN#2 S-NSSAI#2, and Application#3 associated with VPLMN#1 S-NSSAI#3. The generated URSP includes HPLMN S-NSSAI, for example, HPLMN S-NSSAI#A, HPLMN S-NSSAI#B, and HPLMN S-NSSAI#C. Optionally, the generated URSP may further include second network slice identifiers of the visited network, for example, VPLMN#1 S-NSSAI#1, VPLMN#1 S-NSSAI#2, and VPLMN#1 S-NSSAI#3. For example, in this example, the information included in the URSP may be as shown in Table 4-2. Application#1, Application#2, and Application#3 are expanded into VPLMN, Application#A is expanded into HPLMN, and the network slice identifier associated with Application#A is HPLMN S-NSSAI#B.

[0330] Example Y: The second piece of information includes the mapping relationships between VPLMN#1 S-NSSAI#1 and HPLMN S-NSSAI#A, between VPLMN#1 S-NSSAI#2 and HPLMN S-NSSAI#B, and between VPLMN#1 S-NSSAI#3 and HPLMN S-NSSAI#C. When the updated identification information of the network slice to which the UE belongs is updated from HPLMN S-NSSAI#A and HPLMN S-NSSAI#B shown in Example M above to HPLMN S-NSSAI#B shown in Example Q above, the H-PCF may determine that it needs to retrieve UE policy support information (VPLMN assistant UE policy information) corresponding to the visited location and that the generated URSP should not only include information about applications deployed to HPLMN in Table 4-0, but also further include information about applications deployed to VPLMN, such as Application#2 associated with VPLMN#1 S-NSSAI#2. The generated URSP includes HPLMN S-NSSAI, for example, HPLMN S-NSSAI#B. Optionally, the generated URSP may further include a second network slice identifier for the visited network, for example, VPLMN#1 S-NSSAI#2. For example, in this example, the information included in the URSP may be as shown in Table 4-3. Application#2 is expanded into VPLMN, Application#A is expanded into HPLMN, and the network slice identifier associated with Application#A is HPLMN S-NSSAI#B.

[0331] Examples X and Y above are intended merely to illustrate the technical solutions of this application and should not be used as limitations on the technical solutions of this application. It should be understood that the updated identification information of the network slice to which the UE subscribes may be one network slice identification information or a combination of multiple network slice identification information. For example, the updated identification information of the network slice to which the UE subscribes may include only HPLMN S-NSSAI#A or only HPLMN S-NSSAI#B. As another example, the updated identification information of the network slice to which the UE subscribes may include HPLMN S-NSSAI#A and HPLMN S-NSSAI#B. As yet another example, the updated identification information of the network slice to which the UE subscribes may include HPLMN S-NSSAI#B and HPLMN S-NSSAI#C.

[0332] Although not shown in the diagram, after generating a new URSP, H-PCF may send the new URSP to V-PCF using the User Policy Control Update Notify Request (Npcf_UEPolicyControl UpdateNotify Request) message, and V-PCF may further send the new URSP to V-AMF using the User Policy Control Update Notify Request (Npcf_UEPolicyControl UpdateNotify Request) message, and it should be understood that V-AMF sends the URSP to the UE so that the UE can access services on the visited network. For example, V-AMF sends the URSP to the UE using the UE configuration update procedure.

[0333] According to the technical solution of this application, after the identification information of the network slice to which a terminal device subscribes changes or is updated, the mapping relationship between the terminal device's visited network slice identification information and the terminal device's home network slice identification information can be re-obtained based on the updated identification information of the network slice to which the terminal device subscribes. This helps generate a URSP for the terminal device so that the terminal device can successfully access the services of the visited network.

[0334] Embodiments of this application further provide other implementations of the communication system in Figure 1. In this implementation, the communication system includes a first network element 110 and a second network element 120. Optionally, the system 100 may further include a third network element 130 and a fourth network element 140. The system 100 may be configured to perform any of the communication methods in the embodiments shown in Figures 9 to 13 of this application.

[0335] The first network element 110 is configured to update the first service parameter to the second service parameter based on the mapping relationship between the first network slice identification information of the visited network and the second network slice identification information of the home network, and to transmit the second service parameter to the second network element 120, wherein the first service parameter includes the first network slice identification information of the visited network, and the second service parameter includes the second network slice identification information of the home network.

[0336] The second network element 120 is configured to determine a user route selection policy for a terminal device based on a second service parameter, which the terminal device will use to access the destination service.

[0337] Optionally, the third network element 130 is configured to transmit a mapping relationship between the first network slice identification information of the visited network and the second network slice identification information of the home network to the first network element 110.

[0338] Optionally, the fourth network element 140 is configured to send the first service parameters to the first network element 110.

[0339] For specific interaction processes between network elements, please refer to the following explanations in Figures 9-13. Further details are not provided here.

[0340] For example, the communication system provided in this application can obtain a mapping relationship between the destination network slice identification information of a terminal device and the home network slice identification information of a terminal device. This helps generate a user route selection policy for the terminal device so that the terminal device can successfully access services on the destination network.

[0341] In this implementation method, the system 100 shown in Figure 1 may be applied to the 5th generation (5G) network architecture shown in Figure 2 or Figure 3, and obviously may also be applied to future network architectures, such as the 6th generation (6G) network architecture. This is not particularly limited to the embodiments of this application. For example, when the communication system shown in Figure 1 is applied to the 5G network shown in Figure 2 or Figure 3, the first network element 110 may be a policy control network element (V-PCF) in the visited network, the second network element 120 may be a policy control network element (H-PCF) in the home network, the third network element 130 may be a mobility management network element (V-AMF) in the visited network, and the fourth network element 140 may be a mobility management network element (V-UDR) in the visited network.

[0342] Figure 9 is a schematic flowchart of another example of the communication method according to this application.

[0343] S910: The destination policy control network element updates the first service parameter to the second service parameter based on the mapping relationship, the first service parameter containing the first network slice identifier of the destination network, and the second service parameter containing the second network slice identifier of the home network.

[0344] The mapping relationship includes the mapping relationship between the first network slice identification information of the visited network and the second network slice identification information of the home network.

[0345] In a possible implementation, the destination policy control network element may receive mapping relationships from the destination mobility management network element.

[0346] Optionally, before receiving the mapping relationship, the destination policy control network element sends a message to the destination mobility management network element to retrieve the mapping relationship.

[0347] Optionally, the mapping relationship includes a mapping relationship between the configured network slice identifier and the home network slice identifier, determined by the destination location for the terminal device, wherein the configured network slice identifier includes the first network slice identifier and the home network slice identifier includes the second network slice identifier.

[0348] In other possible implementations, the visited policy control network element obtains mapping relationships from the local configuration.

[0349] Optionally, the destination policy control network element receives identification information of the network slice to which the terminal device subscribes from the destination mobility management network element. Updating the first service parameter to the second service parameter based on the mapping relationship by the destination policy control network element includes the following: The destination policy control network element updates the first service parameter to the second service parameter based on the mapping relationship and the identification information of the network slice to which the terminal device subscribes.

[0350] Optionally, before receiving the identification information of the network slice to which the terminal device belongs, the destination policy control network element sends a message to the destination mobility management network element to obtain the identification information of the network slice to which the terminal device belongs.

[0351] Optionally, the destination policy control network element retrieves the first service parameter from the destination unified data repository network element.

[0352] S920: The destination policy control network element sends a second service parameter to the home policy control network element to determine the user route selection policy for the terminal device.

[0353] Optionally, the Visited Policy Control Network element receives the User Route Selection Policy from the Home Policy Control Network element, and the Visited Policy Control Network element sends the User Route Selection Policy to the Visited Mobility Management Network element, which is then used by the terminal device to access services on the Visited Network.

[0354] According to the technical solution of this application, service parameters can be updated based on a mapping relationship between the destination network slice identification information of the terminal device and the home network slice identification information of the terminal device. This helps generate a user route selection policy for the terminal device so that the terminal device can successfully access services on the destination network.

[0355] Figure 10 is a schematic flowchart of a fourth specific example of the communication method according to this application. For the sake of clarity, in the embodiments shown in Figures 10 to 13, the destination policy control network element is abbreviated as V-PCF, the destination mobility management network element is abbreviated as V-AMF, the destination unified data repository network element is abbreviated as V-UDR, the home policy control network element is abbreviated as H-PCF, the terminal device is abbreviated as UE, network slice identification information may be replaced with a network slice equivalent in terms of representation, URSP is used as an example of a user route selection policy, and the user route selection policy includes but is not limited to URSP. Both the destination location and the home location are related to the UE. The destination location is the destination network of the UE, and the home location is the home network of the UE.

[0356] S1001: V-AMF stores the network slice roaming agreement.

[0357] In this embodiment, V-AMF may store a network slice roaming agreement that includes a slice mapping relationship between HPLMN and VPLMN. In the implementation, the network slice roaming agreement may be pre-configured in V-AMF. For example, the mapping relationship for network slice identification information between HPLMN and VPLMN may be one of those shown in Table 8. [Table 8]

[0358] Table 8 shows that different mapping relationships exist between different destination network slice identification information (VPLMN S-NSSAI) and HPLMN S-NSSAI. It should be understood that Table 8 is merely a possible example and should not be used as a limitation to this application.

[0359] S1002:UE roams and registers with the visited network.

[0360] For registering the UE with the visited network, refer to the conventional method. Details will not be explained here. For example, the visited network is VPLMN#1.

[0361] S1003: V-AMF sends the first request message to V-PCF.

[0362] Specifically, the first request message may also be a User Policy Control Create Request (Npcf_UEPolicyControl Create Request) and is used to request V-PCF to create a UE Policy Association. Both V-AMF and V-PCF are located on the visited network VPLMN#1. The first request message includes the UE's subscription permanent identifier, e.g., the subscription permanent identifier (SUPI).

[0363] S1004: V-PCF obtains the first service parameter from V-UDR.

[0364] Optionally, the V-PCF may decide whether or not to perform step 1004 based on the destination network configuration information or identification information of the UE's home network.

[0365] Optionally, the V-PCF may obtain the first service parameter from the local configuration as an alternative. This is not limited to this application.

[0366] The first service parameter may be delivered as a service parameter specific to the visited location (VPLMN-specific service parameter), or it may be such a service parameter. The VPLMN-specific service parameter may include DNN, SSC mode, and network slice information associated with the application deployed in the VPLMN. The network slice identification information included in the VPLMN-specific service parameter may be represented by the VPLMN S-NSSAI.

[0367] For example, the information included in the VPLMN-specific service parameters may be as shown in Table 9. Application#1, Application#2, and Application#3 are expanded into VPLMN#1, and the network slice identification information associated with Application#1, Application#2, and Application#3 respectively is VPLMN#1 S-NSSAI#1, VPLMN#2 S-NSSAI#2, and VPLMN#3 S-NSSAI#3. [Table 9]

[0368] S1005: V-PCF sends a second request message to H-PCF.

[0369] The second request message may also be a User Policy Control Create Request (Npcf_UEPolicyControl Create Request), which is used to request the creation of a UE Policy Association. The V-PCF determines the HPLMN ID of the UE based on the join persistence identifier included in the first request message, and determines the H-PCF identifier based on the HPLMN ID. Furthermore, the second request message may also include the V-PCF identifier (V-PCF ID).

[0370] It should be noted that the second request message does not include VPLMN-specific service parameters.

[0371] S1006: H-PCF generates the URSP for the UE.

[0372] Specifically, the H-PCF retrieves UE context policy control data from the H-UDR, which includes DNN, SSC mode, and network slice information associated with the application deployed on the HPLMN. As shown in Table 10, the network slice associated with the application deployed on the HPLMN is the HPLMN S-NSSAI, for example, HPLMN S-NSSAI#B. [Table 10]

[0373] Table 10 shows that in this case, the URSP is generated by H-PCF based solely on the home network slice identification information HPLMN S-NSSAI, e.g., HPLMN S-NSSAI#B. For ease of distinction, the URSP may be referred to as the first URSP.

[0374] S1007: H-PCF sends a second response message to V-PCF.

[0375] The second response message may also be a User Policy Control Create Response message (Npcf_UEPolicyControl Create Response message), and the second response message contains the first URSP generated by H-PCF.

[0376] S1008: V-PCF sends a first response message to V-AMF.

[0377] Specifically, the first response message may be a User Policy Control Create Response message (Npcf_UEPolicyControl Create Response message), and the first response message includes the first URSP generated by H-PCF.

[0378] The first response message further includes first information used to obtain a mapping relationship. The mapping relationship includes a mapping relationship between the network slice identifier of the visited network and the network slice identifier of the home network. The first information may also be PolicyControl Request Trigger information sent to the V-AMF to instruct the V-AMF to send a User Policy Control Update Request message (Npcf_UEPolicyControl Update Request) to the V-PCF when pre-configured conditions are met. The request message must include a mapping relationship. The pre-configured conditions being met are not limited in this application. For example, this may include cases where a mapping relationship exists or when a mapping relationship has been updated.

[0379] S1009: Optionally, V-AMF sends the UE's URSP to the UE.

[0380] This step is optional. V-AMF sends a first URSP to the UE to allow the UE to access services on the visited network. However, the first URSP is generated based only on the home network slice identifier HPLMN S-NSSAI and does not consider the visited network slice identifier VPLMN S-NSSAI. Therefore, the first URSP may not be able to enable the UE to access services on the visited network.

[0381] S1010: V-AMF sends a third request message to V-PCF, which includes a mapping relationship.

[0382] This step should be understood to further include: V-AMF obtains the identification information of the network slice to which the UE is subscribed, determines a mapping relationship based on the identification information of the network slice to which the UE is subscribed and the roaming agreement, the mapping relationship including a mapping relationship between the network slice identification information of the visited network and the network slice identification information of the home network.

[0383] For example, V-AMF obtains the network slice to which the UE is subscribed and determines the configured network slice identifier (Configured NSSAI) and / or the mapping of the Configured NSSAI based on the network slice to which the UE is subscribed and the roaming agreement. The network slice identifier included in the Configured NSSAI is the network slice identifier of the visited network. The mapping of the Configured NSSAI means that the Configured NSSAI includes the network slice identifier of the visited network and the network slice identifier of the home network. The network slice of the home network included in the mapping of the Configured NSSAI is the network slice to which the UE is subscribed. V-AMF may also determine the mapping relationship based on the Configured NSSAI and / or the mapping of the Configured NSSAI. For example, the mapping relationship may include the Configured NSSAI and the mapping of the Configured NSSAI, or the mapping relationship may include the mapping of the Configured NSSAI.

[0384] Optionally, in other implementations, if V-AMF cannot determine the mapping relationship based on the identification information of the network slice to which the UE belongs and the roaming agreement, V-AMF may obtain the mapping relationship by requesting it from V-NSSF. For example, V-AMF sends the identification information of the network slice to which the UE belongs to V-NSSF, V-NSSF determines the mapping relationship, and returns the mapping relationship to V-AMF.

[0385] Optionally, after obtaining the Configured NSSAI and / or the Configured NSSAI mapping, V-AMF may store the Configured NSSAI and / or the Configured NSSAI mapping in the UE context based on the UE's home HPLMN ID.

[0386] Specifically, V-AMF determines that the pre-configured conditions have been met and sends the mapping relationship to V-PCF by sending a third request message. The third request message may also be a User Policy Control Create Update Message (Npcf_UEPolicyControl UpdateRequest), which is used to request V-PCF to modify the UE policy association.

[0387] For example, the mapping relationships may be those shown in Table 11.

[0388] [Table 11] The mapping relationship includes a mapping relationship between the configured network slice identifier (Configured NSSAI) and the home network slice identifier, determined by the UE's visited location. The Configured NSSAI includes the first network slice identifier (e.g., VPLMN#1 S-NSSAI#1 and VPLMN#1 S-NSSAI#2), and the home network slice identifier includes the second network slice identifier (e.g., HPLMN S-NSSAI#A and HPLMN S-NSSAI#B). Furthermore, HPLMN S-NSSAI#A and HPLMN S-NSSAI#B belong to the identifier of the network slice to which the UE subscribes. The home network slice included in the mapping relationship is the network slice to which the UE subscribes. This can be understood as the home network slice having a mapping relationship with the network slice identifier of the visited network included in the mapping relationship belonging to the identifier of the network slice to which the UE subscribes.

[0389] S1011: V-PCF updates the first service parameter to the second service parameter.

[0390] The first service parameter includes the network slice identification information S-NSSAI of the visited network VPLMN, and the second service parameter includes the home network slice identification information HPLMN S-NSSAI.

[0391] For example, if the network slice identification information included in the first service parameter (VPLMN specific service parameter) is (as shown in Table 9) VPLMN#1 S-NSSAI#1, VPLMN#1 S-NSSAI#2, and VPLMN#1 S-NSSAI#3, and the mapping relationship includes (as shown in Table 11) that HPLMN S-NSSAI#A can be mapped to VPLMN#1 S-NSSAI#1 and HPLMN S-NSSAI#B can be mapped to VPLMN#1 S-NSSAI#2, then V-PCF may decide, based on the mapping relationship, to map VPLMN#1 S-NSSAI#1 and VPLMN#1 S-NSSAI#2 included in the PLMN specific service parameter to HPLMN S-NSSAI#A and HPLMN S-NSSAI#B, respectively. The network slice identification information included in the second service parameter is HPLMN S-NSSAI#A and HPLMN S-NSSAI#B. Since the mapping relationship does not indicate which HPLMN S-NSSAI has a mapping relationship with VPLMN#1 S-NSSAI#3, the second service parameter does not need to include VPLMN#1 S-NSSAI#3. The network slice identifier included in the second service parameter is the HPLMN S-NSSAI, and it can be understood that it belongs to the identifier of the network slice to which the UE is subscribed.

[0392] S1012: V-PCF sends a fourth request message to H-PCF.

[0393] The fourth request message may also be a User Policy Control Create Update Request (Npcf_UEPolicyControl Update Request), which is used to request a UE Policy Association Modification.

[0394] It should be noted that the fourth request message includes the second service parameter.

[0395] S1013: H-PCF updates the UE's URSP.

[0396] Specifically, H-PCF updates the first URSP based on the second service parameter to obtain the updated URSP for the UE. For ease of distinction, the updated URSP may be called the second URSP.

[0397] For example, the contents of the second URSP may be those shown in Table 12. [Table 12]

[0398] Application#1 and Application#2 will be deployed to VPLMN, and Application#A will be deployed to HPLMN.

[0399] Table 12 shows that the second URSP includes HPLMN S-NSSAI, which has a mapping relationship with VPLMN S-NSSAI. Optionally, the second URSP may further include VPLMN S-NSSAI. Thus, the UE may directly determine HPLMN S-NSSAI and VPLMN S-NSSAI according to the URSP.

[0400] S1014: H-PCF sends a fourth response message to V-PCF.

[0401] Specifically, the fourth response message may be a User Policy Control Create Response message (Npcf_UEPolicyControl Create Response message), and the fourth response message includes the URSP updated by H-PCF, i.e., the second URSP.

[0402] S1015: V-PCF sends a third response message to V-AMF.

[0403] Specifically, the third response message may be a User Policy Control Create Update Response (Npcf_UEPolicyControl Update Response), and the third response message includes the URSP updated by H-PCF, i.e., the second URSP.

[0404] S1016: V-AMF sends the updated URSP to the UE.

[0405] The updated URSP for the UE may also be the second URSP shown in Table 12, which will be used by the UE to access the visited service.

[0406] According to the technical solution of this application, service parameters can be updated based on a mapping relationship between the destination network slice identification information of the terminal device and the home network slice identification information of the terminal device. This helps generate a user route selection policy for the terminal device so that the terminal device can successfully access services on the destination network.

[0407] Figure 11 is a schematic flowchart of a fifth specific example of the communication method according to this application. Compared to the embodiment described in Figure 10, in this embodiment, V-AMF sends a User Policy Control Create Request (Npcf_UEPolicyControl Create Request) message and actively includes mapping relationships in the request message.

[0408] S1101 is the same as S1001, and the details will not be explained again here.

[0409] S1102 is the same as S1002, and the details will not be explained again here.

[0410] S1103: V-AMF determines that the mapping relationship needs to be sent to V-PCF.

[0411] Specifically, V-AMF determines that a mapping relationship needs to be sent to V-PCF based on the UE's HPLMN ID. For example, see Table 11 for the contents of the mapping relationship. Further details will not be explained here.

[0412] S1104: V-AMF sends a first request message to V-PCF, which includes a mapping relationship.

[0413] Specifically, V-AMF sends the mapping relationship to V-PCF by sending a first request message. The first request message may also be a User Policy Control Create Request (Npcf_UEPolicyControl Create Request) and is used to request V-PCF to create a UE Policy Association.

[0414] S1105 is the same as S1004, and the details will not be explained again here.

[0415] S1106 is the same as S1011, and the details will not be explained again here.

[0416] S1107: V-PCF sends a second request message to H-PCF.

[0417] The second request message may also be a User Policy Control Create Request (Npcf_UEPolicyControl Create Request), which is used to request the creation of a UE Policy Association.

[0418] It should be noted that the second request message includes the second service parameter.

[0419] S1108: H-PCF generates the UE's URSP.

[0420] Specifically, the H-PCF generates a URSP based on the UE context policy control data obtained from the H-UDR and a second service parameter received from the V-PCF. For ease of distinction, the URSP may also be called a third URSP. For example, the contents of the UE context policy control data may be as shown in Table 10, the contents of the third URSP may be the same as the contents of the second URSP in Figure 10, and the contents of the third URSP may be as shown in Table 12.

[0421] S1109: H-PCF sends a second response message to V-PCF.

[0422] Specifically, the second response message may be a User Policy Control Create Response message (Npcf_UEPolicyControl Create Response message), and the second response message may include a third URSP generated by H-PCF.

[0423] S1110: V-PCF sends a first response message to V-AMF.

[0424] Specifically, the first response message may be a User Policy Control Create Response message (Npcf_UEPolicyControl Create Response message), and the first response message includes a third URSP generated by H-PCF.

[0425] Optionally, after receiving a third URSP, V-AMF may send a third URSP to the UE, thereby allowing the UE to access the visited service.

[0426] S1111: V-AMF determines the updated mapping relationships.

[0427] Specifically, when the UE's subscription data is updated at some point, V-AMF generates a new mapping relationship based on the UE's latest subscription data and the roaming agreement. For example, V-AMF determines the updated configured network slice identification information (new Configured NSSAI) and / or the updated mapping of the Configured NSSAI based on the UE's latest subscription data and the roaming agreement, and determines the updated mapping relationship based on the new Configured NSSAI and / or the new mapping of the Configured NSSAI.

[0428] Furthermore, V-AMF updates locally stored mapping relationships, for example, updating locally stored Configured NSSAI and / or Configured NSSAI mappings.

[0429] S1112: V-AMF sends a third request message to V-PCF, which includes the updated mapping relationship.

[0430] Specifically, V-AMF sends a new mapping relationship to V-PCF by sending a third request message. This third request message may be a User Policy Control Update Request (Npcf_UEPolicyControl Update Request) and is used to request V-PCF to modify the UE policy association.

[0431] S1113: V-PCF, H-PCF, and V-AMF perform the UE's URSP update procedure.

[0432] Specifically, V-PCF updates the service parameters based on the new mapping relationships and sends the updated service parameters to H-PCF. H-PCF updates the UE's URSP based on the updated service parameters and sends the updated UE's URSP to V-PCF. V-PCF sends the updated UE's URSP to V-AMF. For the specific process, please refer to the explanation above, and the details will not be explained again here.

[0433] According to the technical solution of this application, service parameters can be updated based on a mapping relationship between the destination network slice identification information of the terminal device and the home network slice identification information of the terminal device. This helps generate a user route selection policy for the terminal device so that the terminal device can successfully access services on the destination network.

[0434] Figure 12 is a schematic flowchart of a sixth specific example of the communication method according to this application. Compared to Figure 10, in this embodiment, the V-PCF stores the network slice roaming agreement, and the V-PCF only needs to obtain the identification information of the network slice to which the UE subscribes (Subscribe NSSAI) from the V-AMF.

[0435] S1201: V-PCF stores the network slice roaming agreement.

[0436] For specific steps and details regarding how V-PCF stores network slice roaming agreements, refer to the explanation in S1001 regarding how V-AMF stores network slice roaming agreements. Further details will not be explained here.

[0437] S1202 is the same as S1002, and the details will not be explained again here.

[0438] S1203 is the same as S1003, and the details will not be explained again here.

[0439] S1204 is the same as S1004, and the details will not be explained again here.

[0440] S1205 is the same as S1005, and the details will not be explained again here.

[0441] S1206 is the same as S1006, and the details will not be explained again here.

[0442] S1207 is the same as S1007, and the details will not be explained again here.

[0443] S1208: V-PCF sends a first response message to V-AMF.

[0444] Specifically, the first response message may be a User Policy Control Create Response message (Npcf_UEPolicyControl Create Response message), and the first response message includes the first URSP generated by H-PCF.

[0445] The first response message further includes second information used to obtain the Subscribed NSSAI of the network slice to which the UE subscribes. The second information may be PolicyControl Request Trigger information, which may instruct the V-AMF to send an Npcf_UEPolicyControl Update Request message to the V-PCF when pre-configured conditions are met. The request message must include the Subscribed NSSAI of the network slice to which the UE subscribes. The pre-configured conditions being met are not limited in this application. For example, this may be when the Subscribed NSSAI of the network slice to which the UE subscribes exists or when the Subscribed NSSAI of the network slice to which the UE subscribes has been updated.

[0446] S1209 is the same as S1009, and the details will not be explained again here.

[0447] S1210: V-AMF sends a third request message to V-PCF, which includes the identification information of the network slice to which the UE is subscribed.

[0448] Specifically, after obtaining the identification information of the network slice to which the UE belongs and determining that pre-configured conditions are met, V-AMF sends the identification information of the network slice to which the UE belongs to V-PCF by sending a third request message. The third request message may also be a User Policy Control Creation Update Request (Npcf_UEPolicyControl UpdateRequest) message, which is used to request V-PCF to modify the UE policy association.

[0449] S1211: V-PCF updates the first service parameter to the second service parameter.

[0450] Specifically, the V-PCF needs to determine the mapping relationship based on the identification information of the network slice to which the UE is subscribed and the roaming agreement. The mapping relationship includes the mapping relationship between the network slice identification information of the visited network and the network slice identification information of the home network. The first service parameter includes the network slice identification information S-NSSAI of the visited network VPLMN, and the second service parameter includes the home network slice identification information HPLMN S-NSSAI.

[0451] For example, if the network slice identification information included in the first service parameter (VPLMN specific service parameter) is (as shown in Table 9) VPLMN#1 S-NSSAI#1, VPLMN#1 S-NSSAI#2, and VPLMN#1 S-NSSAI#3, and the mapping relationship includes (as shown in Table 11) that HPLMN S-NSSAI#A can be mapped to VPLMN#1 S-NSSAI#1 and HPLMN S-NSSAI#B can be mapped to VPLMN#1 S-NSSAI#2, then V-PCF may decide, based on the mapping relationship, to map VPLMN#1 S-NSSAI#1 and VPLMN#1 S-NSSAI#2 included in the PLMN specific service parameter to HPLMN S-NSSAI#A and HPLMN S-NSSAI#B, respectively. The network slice identification information included in the second service parameter is HPLMN S-NSSAI#A and HPLMN S-NSSAI#B. Since the mapping relationship does not indicate which HPLMN S-NSSAI has a mapping relationship with VPLMN#1 S-NSSAI#3, the second service parameter does not need to include VPLMN#1 S-NSSAI#3. The network slice identifier included in the second service parameter is the HPLMN S-NSSAI, which can be understood to belong to the network slice to which the UE is subscribed.

[0452] S1212 is the same as S1012, and the details will not be explained again here.

[0453] S1213 is the same as S1013, and the details will not be explained again here.

[0454] S1214 is the same as S1014, and the details will not be explained again here.

[0455] S1215 is the same as S1015, and the details will not be explained again here.

[0456] S1216 is the same as S1016, and the details will not be explained again here.

[0457] According to the technical solution of this application, service parameters can be updated based on a mapping relationship between the destination network slice identification information of the terminal device and the home network slice identification information of the terminal device. This helps generate a user route selection policy for the terminal device so that the terminal device can successfully access services on the destination network.

[0458] Figure 12 is a schematic flowchart of a seventh specific example of the communication method according to this application. Compared to the embodiment in Figure 12, in this embodiment, the V-PCF no longer sends PolicyControl Request Trigger information to the V-AMF, and the V-AMF proactively sends a User Policy Control Create Request message (Npcf_UEPolicyControl Create Request). The request message includes identification information of the network slice to which the UE is subscribed.

[0459] S1301 is the same as S1201, and the details will not be explained again here.

[0460] S1302 is the same as S1202 and S1002, and details will not be explained again here.

[0461] S1303: V-AMF determines that the identification information of the network slice to which the UE belongs needs to be sent to V-PCF.

[0462] Specifically, V-AMF determines, based on the HPLMN ID, that the identification information (Subscribed NSSAI) of the network slice to which the UE subscribes needs to be sent to V-PCF.

[0463] S1304: V-AMF sends a first request message to V-PCF, which includes the identification information of the network slice to which the UE is subscribed.

[0464] Specifically, V-AMF sends the V-PCF the identification information of the network slice to which the UE is subscribed by sending a first request message. The first request message may also be a User Policy Control Create Request (Npcf_UEPolicyControl Create Request) and is used to request V-PCF to create a UE Policy Association.

[0465] S1305 is the same as S1204 and S1004, and details will not be explained again here.

[0466] S1306 is the same as S1211, and the details will not be explained again here.

[0467] S1307: V-PCF sends a second request message to H-PCF.

[0468] The second request message may also be a User Policy Control Create Request (Npcf_UEPolicyControl Create Request), which is used to request the creation of a UE Policy Association.

[0469] It should be noted that the second request message includes the second service parameter.

[0470] S1308: H-PCF generates the URSP for the UE.

[0471] Specifically, the H-PCF generates a URSP based on the UE context policy control data obtained from the H-UDR and a second service parameter received from the V-PCF. For ease of distinction, the URSP may also be called a third URSP. For example, the contents of the UE context policy control data may be as shown in Table 10, the contents of the third URSP may be the same as the contents of the second URSP in Figure 10, and the contents of the third URSP may be as shown in Table 12.

[0472] S1309: H-PCF sends a second response message to V-PCF.

[0473] Specifically, the second response message may be a User Policy Control Create Response message (Npcf_UEPolicyControl Create Response message), and the second response message may include a third URSP generated by H-PCF.

[0474] S1310: V-PCF sends a first response message to V-AMF.

[0475] Specifically, the first response message may be a User Policy Control Create Response message (Npcf_UEPolicyControl Create Response message), and the first response message includes a third URSP generated by H-PCF.

[0476] Optionally, after receiving a third URSP, V-AMF may send a third URSP to the UE, thereby allowing the UE to access the visited service.

[0477] S1311:V-AMF determines the updated identification information of the network slice to which the UE belongs.

[0478] Specifically, when a UE's subscription data is updated at some point, V-AMF determines the updated identification information of the network slice to which the UE is subscribed, based on the UE's latest subscription data.

[0479] S1312: V-AMF sends a third request message to V-PCF, which contains updated identification information for the network slice to which the UE is subscribed.

[0480] Specifically, V-AMF sends updated identification information for the network slice to which the UE is subscribed to to V-PCF by sending a third request message. The third request message may also be a User Policy Control Update Request (Npcf_UEPolicyControl Update Request) message, which is used to request V-PCF to modify the UE policy association.

[0481] S1313: V-PCF, H-PCF, and V-AMF perform the UE's URSP update procedure.

[0482] Specifically, the V-PCF determines a new mapping relationship based on the updated identification information of the network slice to which the UE is subscribed, updates the service parameters based on the new mapping relationship, and sends the updated service parameters to the H-PCF. The H-PCF updates the UE's URSP based on the updated service parameters and sends the updated UE's URSP to the V-PCF. The V-PCF then sends the updated UE's URSP to the V-AMF. For the specific process, please refer to the explanation above, as further details will not be provided here.

[0483] According to the technical solution of this application, service parameters can be updated based on a mapping relationship between the destination network slice identification information of the terminal device and the home network slice identification information of the terminal device. This helps generate a user route selection policy for the terminal device so that the terminal device can successfully access services on the destination network.

[0484] This application further provides a communication system comprising a destination policy control network element and a home policy control network element. The destination policy control network element is configured to update a first service parameter to a second service parameter based on a mapping relationship between a first network slice identifier of the destination network and a second network slice identifier of the home network, and to transmit the second service parameter to the home policy control network element, wherein the first service parameter includes the first network slice identifier of the destination network, and the second service parameter includes the second network slice identifier of the home network. The home policy control network element is configured to determine a user route selection policy for a terminal device based on the second service parameter, which will be used by the terminal device to access the destination service.

[0485] Optionally, the communication system further includes a destination mobility management network element. The destination mobility management network element is configured to transmit mapping relationships to the destination policy control network element, or to transmit identification information of the network slice to which the terminal device is subscribed to to the destination policy control network element.

[0486] For example, the communication system provided in this application can obtain a mapping relationship between the destination network slice identification information of a terminal device and the home network slice identification information of a terminal device. This helps generate a user route selection policy for the terminal device so that the terminal device can successfully access services on the destination network.

[0487] It should be understood that the sequence numbers of the processes described above do not indicate the order of execution. The order of execution of the processes should be determined according to the function and internal logic of the processes and should not constitute any limitation to the implementation processes of the embodiments of this application.

[0488] In the embodiments of this application, unless otherwise specified or unless there is a logical inconsistency, the terminology and / or descriptions between different embodiments are consistent and may be mutually referenced, and technical features in different embodiments may be combined into new embodiments based on their internal logical relationships.

[0489] In the above embodiments of this application, it may be understood that the methods implemented by the communication device may, alternatively, be implemented by components (e.g., chips or circuits) that can be configured within the communication device.

[0490] It should be noted that the above describes the method using an example in which the “terminal device” in this application is a UE. In actual use, the UE may also be replaced with other terminal devices, and this is not limited to this application. Optionally, the UE may access the visited service by creating a session. The “session” may be a PDU session or any other type of session, and this is not limited to this application.

[0491] The communication methods provided in embodiments of this application are described in detail above with reference to Figures 5 to 13. The above communication methods are described primarily in terms of the interaction between network elements. To realize the above functions, it can be understood that each network element includes a corresponding hardware structure and / or software module for performing the function. Those skilled in the art should recognize, with reference to the exemplary units and algorithmic steps described in embodiments disclosed in this specification, that this application can be implemented in hardware or in combination of hardware and computer software. Whether the functions are performed by hardware or by hardware driven by computer software depends on the specific application and design constraints of the technical solution. Those skilled in the art may use different methods to realize the described functions for each specific application, but the implementation should not be considered to exceed the scope of this application.

[0492] A communication device provided in the embodiments of this application will be described in detail below with reference to Figures 14 and 15. It should be understood that the description of the device embodiments corresponds to the description of the method embodiments. Therefore, for matters not described in detail, refer to the method embodiments described above. For brevity, some matters will not be explained again.

[0493] In embodiments of this application, the transmitting or receiving device may be divided into functional modules according to the example of the method described above. For example, each functional module may be obtained through division based on its corresponding function, or two or more functions may be integrated into a single processing module. The integrated module may be implemented in hardware form or in the form of a software functional module. It should be noted that the division into modules in embodiments of this application is an example and is merely a logical functional division. Other division methods may exist in actual implementations. An example in which each functional module is obtained through division based on its corresponding function is used below for illustrative purposes.

[0494] Figure 14 is a schematic block diagram of an example of a communication device 1400 according to this application. Any network element in any one of the above methods 500 to 1300, for example, a policy control network element or a mobility management network element, may be implemented by the communication device shown in Figure 14.

[0495] It should be understood that the communication device 1400 may be a physical device, a component of a physical device (e.g., an integrated circuit or chip), or a functional module within a physical device.

[0496] As shown in Figure 14, the communication device 1400 includes one or more processors 1410. The processors 1410 may store execution instructions for performing the methods of the embodiments of this application. Optionally, the processors 1410 may invoke interfaces for implementing receive and transmit functions. The interfaces may be logical interfaces or physical interfaces, but are not limited to these. For example, the interfaces may be transceiver circuits or interface circuits. Transceiver circuits or interface circuits configured to implement receive and transmit functions may be separate or integrated. The transceiver circuits or interface circuits may be configured to read and write code / data, or the transceiver circuits or interface circuits may be configured to transmit or transfer signals.

[0497] Optionally, the interface may be implemented through a transceiver. Optionally, the communication device 1400 may further include a transceiver 1430. The transceiver 1430 may also be called a transceiver unit, transceiver machine, transceiver circuit, transceiver, etc., and is configured to implement receiving and transmitting functions.

[0498] Optionally, the communication device 1400 may further include a memory 1420. The specific location of the memory 1420 is not particularly limited in this embodiment of this application. The memory may be integrated with the processor or independent of the processor. When the communication device 1400 does not include memory, the communication device 1400 must have only processing functions, and the memory may be located elsewhere (e.g., in a cloud system).

[0499] The processor 1410, memory 1420, and transceiver 1430 communicate with each other by using internal connection paths to transfer control signals and / or data signals.

[0500] Although not shown in the figures, it can be understood that the communication device 1400 may further include other devices, such as an input device, an output device, or a battery.

[0501] Optionally, in some embodiments, memory 1420 may store execution instructions for performing the method according to embodiments of this application. The processor 1410 may execute the instructions stored in memory 1420 and, in combination with other hardware (e.g., transceiver 1430), complete the steps performed in the following manner. For specific operating processes and beneficial effects, refer to the description of embodiments of the method above.

[0502] The methods disclosed in embodiments of this application may be applied to or implemented by a processor 1410. The processor 1410 may be an integrated circuit chip having signal processing capabilities. In the implementation process, the steps of the method may be completed by using instructions in the form of hardware integrated logic circuits or software within the processor. The processor may be a general-purpose processor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device, a discrete gate or transistor logic device, or a discrete hardware component. The processor may implement or execute the methods, steps and logic block diagrams disclosed in embodiments of this application. The general-purpose processor may be a microprocessor, or the processor may be any conventional processor, etc. The steps of the methods disclosed with reference to embodiments of this application may be performed directly by a hardware decoding processor, or by a combination of hardware modules and software modules within the decoding processor. The software module may reside in a mature storage medium in the art, such as random access memory (RAM), flash memory, read-only memory (ROM), programmable read-only memory, electrically erasable programmable memory, or registers. The storage medium resides in memory, and the processor reads instructions from memory and, in combination with the processor hardware, completes the steps of the method described above.

[0503] Memory 1420 may be volatile memory or non-volatile memory, or it may include both volatile and non-volatile memory. Non-volatile memory may be read-only memory ROM, programmable read-only memory (programmable ROM, PROM), erasable programmable read-only memory (erasable PROM, EPROM), electrically erasable programmable read-only memory (electrically EPROM, EEPROM), or flash memory. Volatile memory may be random-access memory RAM used as an external cache. Many forms of RAM are available, not as an example but as an example, such as static random access memory (static RAM, SRAM), dynamic random access memory (dynamic RAM, DRAM), synchronous dynamic random access memory (synchronous DRAM, SDRAM), double data rate synchronous dynamic random access memory (double data rate SDRAM, DDR SDRAM), enhanced synchronous dynamic random access memory (enhanced SDRAM, ESDRAM), synchlink dynamic random access memory (synchlink DRAM, SLDRAM), and direct rambus random access memory (direct rambus RAM, DR RAM). It should be noted that the memory for the systems and methods described in this specification is intended to include, but is not limited to, these types of memory and any other suitable types of memory.

[0504] Figure 15 is a schematic block diagram of the communication device 1500 according to this application.

[0505] Optionally, the specific form of the communication device 1500 may be a general-purpose computer device or a chip within a general-purpose computer device. This is not limited to this embodiment of the application. As shown in Figure 15, the communication device includes a processing unit 1510 and a transceiver unit 1520.

[0506] Specifically, the communication device 1500 may be any of the network elements in this application, and may implement functions that can be realized by the network elements. It should be understood that the communication device 1500 may be a physical device, a component of a physical device (e.g., an integrated circuit or chip), or a functional module within a physical device.

[0507] In a possible design, the communication device 1500 may be a policy control device in an embodiment of the above method, or a chip configured to implement the functions of a policy control device in an embodiment of the above method.

[0508] For example, transceiver unit 1520 is configured to transmit first information, which includes identification information for a first network, identification information for a first network slice of a destination network, and identification information for the network slice to which the terminal device subscribes. Transceiver unit 1520 is further configured to receive second information, which includes a mapping relationship between the second network slice identification information for a destination network and the first network slice identification information for a home network, where the second network slice identification information for the destination network is a subset of the first network slice identification information for the destination network, and the first network slice identification information for the home network is a subset of the identification information for the network slice to which the terminal device subscribes. The second information is used to determine the user route selection policy URSP for the terminal device.

[0509] Optionally, when the communication device 1500 belongs to a home network, the transceiver unit 1520 is further configured to receive third information, which includes first network slice identification information of the visited network. The processing unit 1510 is configured to determine a user route selection policy URSP for the terminal device based on the second and third information, which the terminal device will use to access services on the visited network. The transceiver unit 1520 is further configured to transmit the URSP.

[0510] Optionally, the transceiver unit 1520 is further configured to receive a fourth piece of information, which indicates updated identification information for the network slice to which the terminal device is subscribed. The transceiver unit 1520 is further configured to transmit a fifth piece of information, which is used to request a mapping relationship between a third network slice identification information for a visited network and a second network slice identification information for a home network, where the third network slice identification information for the visited network is a subset of the first network slice identification information for the visited network, and the second network slice identification information for the home network is a subset of updated identification information for the network slice to which the terminal device is subscribed.

[0511] Optionally, when the communication device 1500 belongs to a destination network, the transceiver unit 1520 is further configured to transmit second information and receive a URSP, which will be used by the terminal device to access services on the destination network. The transceiver unit 1520 is further configured to receive third information, which includes identification information of the network slice to which the terminal device subscribes.

[0512] Optionally, the transceiver unit 1520 is further configured to receive a fourth piece of information, the fourth piece of information, which includes updated identification information for the network slice to which the terminal device subscribes; and to transmit a fifth piece of information, the fifth piece of information, which is used to request a mapping relationship between a third network slice identification information for the visited network and a second network slice identification information for the home network, the third network slice identification information for the visited network being a subset of the first network slice identification information for the visited network, and the second network slice identification information for the home network being a subset of updated identification information for the network slice to which the terminal device subscribes.

[0513] As another example, the processing unit 1510 is configured to update a first service parameter to a second service parameter based on a mapping relationship between a first network slice identifier of the visited network and a second network slice identifier of the home network, wherein the first service parameter includes the first network slice identifier of the visited network and the second service parameter includes the second network slice identifier of the home network, and the transceiver unit 1520 is configured to transmit the second service parameter to a home policy control network element, wherein the second service parameter is used to determine a user route selection policy for a terminal device.

[0514] Optionally, the transceiver unit 1520 may be further configured to receive mapping relationships from the destination mobility management network element.

[0515] Optionally, the transceiver unit 1520 may be further configured to send a message to the destination mobility management network element to obtain a mapping relationship.

[0516] Optionally, the transceiver unit 1520 is further configured to acquire mapping relationships from the local configuration.

[0517] Optionally, the transceiver unit 1520 is further configured to receive identification information of the network slice to which the terminal device is subscribed from the destination mobility management network element. The processing unit 1510 is further configured to update the first service parameter to the second service parameter based on the mapping relationship and the identification information of the network slice to which the terminal device is subscribed.

[0518] Optionally, the transceiver unit 1520 may be further configured to send a message to a destination mobility management network element to obtain identification information of the network slice to which the terminal device is subscribed.

[0519] Optionally, the transceiver unit 1520 may be further configured to retrieve a first service parameter from the visited unified data repository network element.

[0520] Optionally, the transceiver unit 1520 may be further configured to receive user route selection policies from a home policy control network element and transmit the user route selection policies to a destination mobility management network element, which will then be used by terminal devices to access services on the destination network.

[0521] When the communication device 1500 is a policy control device, it should be understood that the transceiver unit 1520 within the communication device 1500 may be implemented using a communication interface (e.g., a transceiver or an input / output interface), and the processing unit 1510 within the communication device 1500 may be implemented using at least one processor, which may correspond to, for example, the processor 1410 shown in Figure 14.

[0522] The communication device 1500 may optionally further include a storage unit. The storage unit may be configured to store instructions or data. The processing unit may retrieve the instructions or data stored in the storage unit to perform the corresponding operation.

[0523] It should be further understood that the specific process by which the unit performs the corresponding steps described above is described in detail in the embodiments of the method described above. For the sake of brevity, the details will not be explained here.

[0524] In other possible designs, the communication device 1500 may be a network slice selection network element or an access management network element in the embodiment of the above method, or it may be a chip configured to implement the functions of a network slice selection network element or an access management network element in the embodiment of the above method.

[0525] For example, transceiver unit 1520 is configured to receive first information, which includes identification information for a first network, identification information for a first network slice of a destination network, and identification information for the network slice to which the terminal device subscribes. Processing unit 1510 is configured to determine second information based on the first information. Transceiver unit 1520 is further configured to transmit second information, which includes a mapping relationship between the identification information for a second network slice of a destination network of the terminal device and the identification information for a first network slice of the terminal device's home network, where the identification information for the second network slice of the destination network is a subset of the identification information for the first network slice of the destination network, and the identification information for the first network slice of the home network is a subset of the identification information for the network slice to which the terminal device subscribes. The second information is used to determine the user route selection policy URSP for the terminal device.

[0526] Optionally, the transceiver unit 1520 is further configured to receive a fifth piece of information, which indicates updated identification information for the network slice to which the terminal device is subscribed. The second network element transmits a sixth piece of information to the first network element, which includes a mapping relationship between the third network slice identification information of the visited network and the second network slice identification information of the home network, where the third network slice identification information of the visited network is a subset of the first network slice identification information of the visited network, and the second network slice identification information of the home network is a subset of updated identification information for the network slice to which the terminal device is subscribed.

[0527] When the communication device 1500 is a network slice selection network element or an access management network element, the transceiver unit 1520 within the communication device 1500 may be implemented using a communication interface (e.g., a transceiver or an input / output interface), for example, corresponding to the communication interface 1430 shown in Figure 14, and the processing unit 1510 within the communication device 1500 may be implemented using at least one processor, for example, corresponding to the processor 1410 shown in Figure 14.

[0528] The communication device 1500 may optionally further include a storage unit. The storage unit may be configured to store instructions or data. The processing unit may retrieve the instructions or data stored in the storage unit to perform the corresponding operation.

[0529] It should be further understood that the specific process by which the unit performs the corresponding steps described above is described in detail in the embodiments of the method described above. For the sake of brevity, the details will not be explained here.

[0530] It should be further understood that the device 1500 may be further configured to implement the functions of network elements such as the PCF, AMF, and NSSF in the embodiments of the method described above. The transceiver unit 1520 may be configured to implement operations related to receiving and transmitting. The processing unit 1510 may be configured to implement operations other than receiving and transmitting. For further details, refer to the description of the embodiments of the method described above. Details are not listed again here.

[0531] Furthermore, in this application, the communication device 1500 is presented in the form of a functional module. Herein, “module” may be an application-specific integrated circuit (ASIC), a circuit, a processor that runs one or more software or firmware programs, and memory, integrated logic circuits, and / or other components that can provide the above functions. In a simple embodiment, those skilled in the art will understand that the device 1500 may be in the form shown in Figure 15. The processing unit 1510 may be implemented using the processor 1410 shown in Figure 14. Optionally, if the computer device shown in Figure 14 includes memory 1420, the processing unit 1510 may be implemented using the processor 1410 and memory 1420. The transceiver unit 1520 may be implemented using the transceiver 1430 shown in Figure 14. The transceiver 1430 has receiving and transmitting functions. Specifically, the processor is implemented by running a computer program stored in memory. Optionally, when the device 1500 is a chip, the functions and / or implementation processes of the transceiver unit 1520 may be implemented by means of pins, circuits, etc. Optionally, the memory may be a storage unit on the chip, such as a register or cache. The storage unit may be a storage unit located within a computer device but outside the chip, for example, the memory 1420 shown in Figure 14, or a storage unit located in another system or device but not in a computer device. A person skilled in the art will recognize, in combination with the examples described in the embodiments disclosed in this specification, that the units and algorithm steps may be implemented by electronic hardware, or a combination of computer software and electronic hardware. Whether the functions are implemented by hardware or software depends on the specific application and design constraints of the technical solution. A person skilled in the art may use different methods to implement the functions described for each specific application, but the implementation methods should not be considered to exceed the scope of this application.

[0532] Aspects or features of this application may be realized as methods, apparatus or products using standard programming and / or engineering techniques. As used in this application, the term “product” covers a computer program accessible from any computer-readable component, carrier or medium. For example, computer-readable medium may include, but is not limited to, magnetic storage components (e.g., hard disk drives, floppy disks or magnetic tapes), optical discs (e.g., compact discs (CDs) or digital versatile discs (DVDs)), smart cards and flash memory components (e.g., erasable programmable read-only memory (EPROMs), cards, sticks or key drives). Furthermore, the various storage media described in this specification may refer to one or more devices and / or other machine-readable media configured to store information. The term “machine-readable medium” may include, but is not limited to, wireless channels and various other media capable of storing, containing and / or carrying instructions and / or data.

[0533] According to the methods provided in embodiments of this application, this application further provides a computer program product, which includes computer program code. When the computer program code is executed on a computer, the computer becomes capable of performing the methods in either of the embodiments shown in Figures 5 and 13.

[0534] According to the method provided in embodiments of this application, this application further provides a computer-readable medium that stores program code. When the program code is executed on a computer, the computer is able to perform the method in either of the embodiments shown in Figures 5 and 8.

[0535] According to the method provided in embodiments of this application, this application further provides a system, the system including the above-described apparatus or device.

[0536] All or part of the embodiments described above may be implemented by software, hardware, firmware, or a combination thereof. When software is used to implement an embodiment, all or part of the embodiment may be implemented in the form of a computer program product. A computer program product includes one or more computer instructions. When the computer instructions are loaded into a computer and executed, all or part of the procedures or functions according to the embodiments of this application are generated. The computer may be a general-purpose computer, a dedicated computer, a computer network, or other programmable device. The computer instructions may be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another. For example, computer instructions may be transmitted by wired means (e.g., coaxial cable, optical fiber, or digital subscriber line (DSL)) or wireless means (e.g., infrared, radio, or microwave) from one website, computer, server, or data center to another. The computer-readable storage medium may be any available medium accessible by a computer, or a data storage device such as a server or data center that integrates one or more available media. The usable media may also be magnetic media (e.g., floppy disks, hard disks, or magnetic tapes), optical media (e.g., digital video discs (DVDs)), semiconductor media (e.g., solid state drives (SSDs)), etc.

[0537] As used in this specification, terms such as “component,” “module,” and “system” are used to indicate computer-related entities, hardware, firmware, combinations of hardware and software, software, or running software. For example, a component may be, but is not limited to, a process running on a processor, a processor, an object, an executable file, an execution thread, a program, and / or a computer. As illustrated by the drawings, both a computing device and an application running on a computing device may be components. One or more components may reside in a process and / or an execution thread, and components may reside on one computer and / or be distributed between two or more computers. Furthermore, these components may run from various computer-readable media that store various data structures. For example, components may communicate using local and / or remote processes based on signals having one or more data packets (e.g., data from a local system, a distributed system, and / or data from two components interacting with other systems across a network such as the Internet, which interacts with other systems using signals).

[0538] The term "and / or" in this specification simply refers to an association between related objects, and it should be understood that there may be three possible relationships. For example, A and / or B may indicate the following three cases: that only A exists, that both A and B exist, and that only B exists. Furthermore, the letter " / " in this specification usually indicates an "or" relationship between related objects.

[0539] Furthermore, it should be understood that the numbers such as "first," "second," etc., are introduced in the embodiments of this application solely to distinguish between different objects, for example, between different "information," "devices," or "units." Understanding the correspondence between specific objects and different objects should be determined based on the function and internal logic of the objects and should not constitute any limitation on the implementation process of the embodiments of this application.

[0540] A person skilled in the art will recognize, in combination with the examples described in the embodiments disclosed in this specification, that the units and algorithmic steps may be implemented by electronic hardware, or by a combination of computer software and electronic hardware. Whether the functions are implemented by hardware or software depends on the specific application and design constraints of the technical solution. A person skilled in the art may use different methods to implement the functions described for each specific application, but the implementation methods should not be considered to exceed the scope of this application.

[0541] For the sake of convenience and conciseness of explanation, it will be readily apparent to those skilled in the art that the specific operating processes of the above systems, devices, and units can be described by referring to the corresponding processes in the embodiments of the above methods. Further details will not be described here.

[0542] In some embodiments provided in this application, it should be understood that the systems, apparatus and methods disclosed may be implemented in other ways. For example, the embodiments of the apparatus described are merely examples. For example, the division into units is merely a logical functional division. Other division methods may exist in actual implementations. For example, multiple units or components may be combined or integrated into other systems, or some features may be ignored or not performed. Furthermore, the mutual coupling, direct coupling or communication connection indicated or discussed may be implemented through some interfaces, and the indirect coupling or communication connection between apparatus or units may be implemented in electrical, mechanical or other forms.

[0543] Units described as separate parts may or may not be physically separate, and parts shown as units may or may not be physical units, may be located in one place, or may be distributed across multiple network units. Some or all of the units may be selected according to the actual requirements in order to achieve the objectives of the solution in the embodiment.

[0544] Furthermore, the functional units in the embodiments of this application may be integrated into a single processing unit, or each unit may exist physically independently, or two or more units may be integrated into a single unit.

[0545] When a function is implemented in the form of a software function unit and sold or used as an independent product, the function may be stored on a computer-readable storage medium. Based on this understanding, the technical solution of this application, or a portion of the technical solution that contributes to the prior art, may be implemented in the form of a software product. A computer software product is stored on a storage medium and includes several instructions for instructing a computer device (which may be a personal computer, server, or network device) to perform all or part of the steps of the method described in embodiments of this application. The storage medium includes any medium capable of storing program code, such as a USB flash drive, a removable hard disk, read-only memory (ROM), random access memory (RAM), a magnetic disk, or an optical disk. The above description is merely a specific implementation of this application. However, the scope of protection of this application is not limited thereto. Any modification or substitution that is readily conceivable by a person skilled in the art within the technical scope disclosed in this application shall fall within the scope of protection of this application. Accordingly, the scope of protection of this application shall be subject to the scope of protection of the claims.

Claims

1. A method of communication, The steps include: updating a first service parameter to a second service parameter based on a mapping relationship between a first network slice identifier of the visited network and a second network slice identifier of the home network, wherein the first service parameter includes the first network slice identifier of the visited network, and the second service parameter includes the second network slice identifier of the home network; The steps include: the visited policy control network element transmits the second service parameter to the home policy control network element, the second service parameter being used to determine the user route selection policy for the terminal device; and Includes, The mapping relationship includes a mapping relationship between a configured network slice identification information and a home network slice identification information, determined by the visited network for the terminal device, wherein the configured network slice identification information includes the first network slice identification information, and the home network slice identification information includes the second network slice identification information.

2. The method according to claim 1, further comprising the step of receiving the mapping relationship from the destination mobility management network element via the destination policy control network element.

3. The method according to claim 2, further comprising the step of the destination policy control network element sending a message to the destination mobility management network element for obtaining the mapping relationship.

4. The method according to claim 1, further comprising the step of obtaining the first service parameter from the Visited Unified Data Repository Network element using the Visited Policy Control Network element.

5. The method according to claim 1, further comprising the step of obtaining the mapping relationship from the local configuration using the destination policy control network element.

6. The destination policy control network element further includes the step of receiving identification information of the network slice to which the terminal device is subscribed from the destination mobility management network element, The step of updating the first service parameter to the second service parameter based on the mapping relationship between the first network slice identification information of the visited network and the second network slice identification information of the home network, using a visited policy control network element, The method according to claim 5, further comprising the step of updating the first service parameter to the second service parameter based on the mapping relationship and the identification information of the network slice to which the terminal device is subscribed, using the destination policy control network element.

7. The method according to claim 6, further comprising the step of the destination policy control network element sending a message to the destination mobility management network element for obtaining the identification information of the network slice to which the terminal device is subscribed.

8. The steps include: receiving the user route selection policy from the home policy control network element using the destination policy control network element; The steps include: transmitting the user route selection policy from the destination policy control network element to the destination mobility management network element, wherein the user route selection policy will be used by the terminal device to access the services of the destination network; and The method according to claim 1, further comprising:

9. A communication system including a destination policy control network element and a destination mobility management network element, The destination mobility management network element is configured to transmit a mapping relationship between the first network slice identification information of the destination network and the second network slice identification information of the home network to the destination policy control network element. The visited policy control network element is configured to update the first service parameter to a second service parameter based on the mapping relationship, and to transmit the second service parameter to the home policy control network element, wherein the first service parameter includes the first network slice identifier of the visited network, and the second service parameter includes the second network slice identifier of the home network. The mapping relationship includes a mapping relationship between a configured network slice identification information and a home network slice identification information, determined by the visited network for a terminal device, wherein the configured network slice identification information includes the first network slice identification information, and the home network slice identification information includes the second network slice identification information.

10. The system further includes the home policy control network element, The system according to claim 9, wherein the home policy control network element is configured to determine a user route selection policy for a terminal device based on the second service parameter, and the user route selection policy is used by the terminal device to access a visited service.

11. The system according to claim 10, wherein the destination mobility management network element is further configured to receive messages from the destination policy control network element for obtaining the mapping relationship.

12. The system according to claim 9, wherein the mapping relationship includes a mapping relationship between configured network slice identification information and home network slice identification information determined by the visited network for a terminal device, the configured network slice identification information includes the first network slice identification information, and the home network slice identification information includes the second network slice identification information.

13. The system according to claim 9, wherein the destination policy control network element is further configured to obtain the mapping relationship from the local configuration.

14. The destination mobility management network element is further configured to transmit identification information of the network slice to which the terminal device is subscribed to to the destination policy control network element. The destination policy control network element is configured to update the first service parameter to the second service parameter based on the mapping relationship between the first network slice identification information of the destination network and the second network slice identification information of the home network, The system according to claim 13, specifically comprising updating the first service parameter of the terminal device to the second service parameter based on the mapping relationship and the identification information of the network slice to which the terminal device is subscribed.

15. The system according to claim 14, wherein the destination mobility management network element is further configured to receive a message from the destination policy control network element for obtaining the identification information of the network slice to which the terminal device is subscribed.

16. The system according to claim 9, further comprising a destination unified data repository network element, wherein the destination unified data repository network element is configured to transmit the first service parameter to the destination policy control network element.

17. The home policy control network element is further configured to transmit the user route selection policy to the destination policy control network element. The system according to claim 10, wherein the destination policy control network element is further configured to transmit the user route selection policy to the destination mobility management network element, the user route selection policy to be used by the terminal device to access services of the destination network.

18. A communication device, A communication device including a processor configured to execute computer instructions stored in memory so that the communication device performs the method described in any one of claims 1 to 8.

19. A computer-readable storage medium, A computer-readable storage medium that stores a computer program, and when the computer program is executed by a communication device, the method described in any one of claims 1 to 8 is executed.

20. It is a chip system, A chip system including a processor configured to call a computer program or instruction from memory and execute the computer program or instruction, such that a communication device on which the chip system is installed implements the method described in any one of claims 1 to 8.

21. A method of communication, The steps include: the destination mobility management network element transmits to the destination policy control network element the mapping relationship between the first network slice identification information of the destination network and the second network slice identification information of the home network; The steps include updating a first service parameter to a second service parameter based on the mapping relationship using the destination policy control network element, wherein the first service parameter includes the first network slice identification information of the destination network, and the second service parameter includes the second network slice identification information of the home network. The steps include: the visited policy control network element transmitting the second service parameter to the home policy control network element; Includes, The mapping relationship includes a mapping relationship between a configured network slice identification information and a home network slice identification information, determined by the visited network for a terminal device, wherein the configured network slice identification information includes the first network slice identification information, and the home network slice identification information includes the second network slice identification information.

22. The method according to claim 21, comprising the step of determining a user route selection policy for a terminal device based on the second service parameter using the home policy control network element, wherein the user route selection policy will be used by the terminal device to access the visited service.

23. The method according to claim 22, further comprising the step of the destination mobility management network element receiving a message from the destination policy control network element for obtaining the mapping relationship.

24. The step further includes the destination mobility management network element transmitting identification information of the network slice to which the terminal device is subscribed to to the destination policy control network element, The step of updating the first service parameter to the second service parameter based on the mapping relationship using the destination policy control network element is as follows: The method according to claim 21, further comprising the step of updating the first service parameter of the terminal device to the second service parameter based on the mapping relationship and the identification information of the network slice to which the terminal device is subscribed, using the destination policy control network element.

25. The method according to claim 24, further comprising the step of the destination mobility management network element receiving a message from the destination policy control network element for obtaining the identification information of the network slice to which the terminal device is subscribed.

26. The method according to claim 21, further comprising the step of transmitting the first service parameter to the destination policy control network element via a destination unified data repository network element.

27. The home policy control network element transmits the user route selection policy to the destination policy control network element. The steps include: the destination policy control network element transmits the user route selection policy to the destination mobility management network element, the user route selection policy being used by the terminal device to access the services of the destination network; and The method according to claim 21, further comprising:

28. A communication device comprising means for performing the method described in any one of claims 1 to 8.

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