Communication method, device and system

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 priority to Chinese Patent Application No. 202210699286.1, entitled "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, entitled "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 separation between slices, 5th generation (5G) network slicing technology provides a mutually separated network environment for different application scenarios by virtualizing independent logical networks on the same network infrastructure, so that network functions and characteristics can be customized for different application scenarios based on their respective requirements. When a network slice is deployed in the core network, if a user equipment (UE) (e.g., a terminal device) needs to access the slice, the UE may provide requested network slice selection assistance information (Requested NSSAI) to the core network, so that the core network can select a public data network (PDN) network route access policy (UE 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 / a specific type of application, so that the UE can access the services of the application by using the session. Usually, the URSP is generated by the home public land mobile network (HPLMN) network. The network needs to know in advance the attribute information of the session associated with the application and further generate the URSP based on this information.

[0004] When the UE is in a roaming scenario, some applications can be temporarily deployed in the visited public land mobile network (VPLMN). However, since the home public land mobile network (HPLMN) does not recognize information about these applications, the policy control network element (policy control function, PCF) in the VPLMN (abbreviated as V-PCF) needs to provide some UE policy support information corresponding to the visited location of the PCF in the HPLMN (abbreviated as H-PCF). For example, the support information may include the data network name (DNN) associated with some applications deployed in the VPLMN, the session and service continuity (SSC) mode, network slice information, etc. The network slice information included in the UE policy support information corresponding to the visited location is the single-network slice selection assistance information (S-NSSAI) in the VPLMN. In the process of generating the Unified Registration and Service Profile (URSP), the H-PCF may comprehensively consider the UE policy support information corresponding to the visited location and transmitted by the V-PCF. In this way, the optimal URSP is determined for the roaming UE, and the roaming UE can access some applications deployed in the VPLMN by using the extended URSP. However, after the support information from the V-PCF is incorporated into the extended URSP, some S-NSSAIs in the URSP are HPLMN values, and some S-NSSAIs in the URSP are VPLMN values (the VPLMN values are from the V-PCF). This affects the use of the URSP by the UE. Therefore, the VPLMN S-NSSAI included in the support information needs to be mapped to the HPLMN S-NSSAI. Summary of the Invention

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

[0006] According to a first aspect, a communication method is determined that 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 the first network slice identification information of the visited network and the 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 transmits the second service parameter to the home policy control network element, and the second service parameter is used to determine a user route selection policy for the terminal device.

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

[0008] Referring to the first aspect, in some implementation manners of the first aspect, the method further includes the following. The visited policy control network element receives the mapping relationship from the visited mobility management network element.

[0009] Referring to the first aspect, in some implementation manners of the first aspect, before the mapping relationship is received, 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.

[0010] Referring to the first aspect, in some implementation manners of the first aspect, the mapping relationship includes a mapping relationship determined by the visited location of the terminal device between the configured network slice identification information and the home network slice identification information, 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.

[0011] Referring to the first aspect, in some other implementation manners of the first aspect, the method further includes the following. The visited policy control network element obtains the mapping relationship from the local configuration.

[0012] Referring to the first aspect, in some other implementation manners of the first aspect, the method further includes the following. The visited policy control network element receives the identification information of the network slice to which the terminal device belongs from the visited mobility management network element. The visited policy control network element updates the first service parameter to the second service parameter based on the mapping relationship includes the following. The visited 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 belongs.

[0013] Referring to the first aspect, in some other implementation manners 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 following. The visited policy control network element sends a message for obtaining the identification information of the network slice to which the terminal device subscribes to the visited mobility management network element.

[0014] Referring to the first aspect, in some other implementation manners of the first aspect, the method further includes the following. The visited policy control network element obtains the first service parameter from the visited unified data repository network element.

[0015] Referring to the first aspect, in some implementation manners of the first aspect, the method further includes the following. 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, and the user route selection policy will be used by the terminal device to access the services of the visited network.

[0016] According to a second aspect, a communication system including a visited policy control network element and a home policy control network element is provided. The visited policy control network element is configured to update a first service parameter to a second service parameter based on a mapping relationship between first network slice identification information of a visited network and second network slice identification information of a home network, and transmit the second service parameter to the home policy control network element. 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 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 to be used by the terminal device to access a visited service.

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

[0018] Referring to the second aspect, in some implementation manners of the second aspect, the system further includes a visited mobility management network element, and the visited mobility management network element is configured to transmit the mapping relationship to the visited policy control network element.

[0019] Referring to the second aspect, in some implementation manners of the second aspect, the visited mobility management network element is further configured to receive a message for obtaining the mapping relationship from the visited policy control network element.

[0020] Referring to the second aspect, in some implementation manners of the second aspect, the mapping relationship includes a mapping relationship determined by the visited location of the terminal device between the configured network slice identification information and the home network slice identification information, 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.

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

[0022] Referring to the second aspect, in some other implementation manners of the second aspect, the visited mobility management network element is further configured to send the identification information of the network slice to which the terminal device belongs to the visited policy control network element, and the visited policy control network element is specifically configured to update 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 belongs.

[0023] Referring to the second aspect, in some other implementation manners of the second aspect, the visited mobility management network element is further configured to receive a message for obtaining the identification information of the network slice to which the terminal device belongs from the visited policy control network element.

[0024] Referring to the second aspect, in some implementation manners of the second aspect, the system further includes a visited unified data repository network element, and the visited unified data repository network element is configured to send the first service parameter to the visited 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 route 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 a third aspect, a communication method is provided, including: The visited policy control network element sends second service parameters to the home policy control network element, where the second service parameters are obtained by the visited policy control network element by updating first service parameters based on a mapping relationship between first network slice identification information of a visited network and second network slice identification information of a home network. The home policy control network element determines a user route selection policy for the terminal device based on the second service parameters, and the user route 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 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 home policy control network element sends the user route selection policy to the visited policy control network element. The visited policy control network element is further configured to send the user route selection policy to the visited mobility management network element.

[0029] According to a fourth aspect, a communication method including the following is provided. A first network element transmits first information to a second network element. The first information includes identification information of a first network, first network slice identification information of a visited 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 includes a mapping relationship between second network slice identification information of the visited network and first network slice identification information of a home network. The second network slice identification information of the visited network is a subset of the first network slice identification information of the visited network. 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. 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 a 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 a home network. The second information is determined by the second network element based on the first information. 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 explained 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. That 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 may be explained as follows. The first network slice identification information of the home network includes some or all of the information within the identification information of the network slice to which the terminal device subscribes.

[0030] According to the technical solution of this application, a mapping relationship between the visited 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 visited 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 visited network. In this way, the terminal device can directly determine the mapping relationship between the visited 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 visited network, the third information includes the first network slice identification information of the visited 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 visited network, and the first network element sends the URSP to the third network element.

[0033] Referring to the fourth aspect, in some implementation manners of the fourth aspect, the method further includes the following. The first network element receives fourth information, where the fourth information indicates updated identification information of a network slice to which a terminal device subscribes. The first network element sends fifth information to a second network element, where the fifth information 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. The third network slice identification information of the visited network is a subset of 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.

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

[0035] Referring to the fourth aspect, in some implementation manners of the fourth aspect, the first network element is a policy control network element belonging to a 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 a visited network.

[0036] Referring to the fourth aspect, in some other implementation manners of the fourth aspect, the first network element and the second network element belong to the visited network, and the method further includes the following. The first network element sends second information to a fourth network element, the fourth network element belongs to the home network, the first network element receives a user root selection policy (URSP) of the terminal device from the fourth network element, and the URSP is to be used by the terminal device to access services of the visited network.

[0037] Referring to the fourth aspect, in some other implementation manners of the fourth aspect, the method further includes the following. The first network element receives third information from a third network element, the third network element belongs to the visited network, and the third information includes identification information of a network slice to which the terminal device subscribes.

[0038] Referring to the fourth aspect, in some other implementation manners of the fourth aspect, the method further includes the following. The first network element receives fourth information from a third network element, the third network element belongs to the visited network, the fourth information includes updated identification information of a network slice to which the terminal device subscribes, the first network element sends fifth information to a second network element, the fifth information is used to request a mapping relationship between third network slice identification information of the visited network and second network slice identification information of the home network, the third network slice identification information of the visited network is a subset of 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.

[0039] Referring to the fourth aspect, in some other implementation manners 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 the fifth aspect, a communication method is provided, including the following. The second network element receives first information from the first network element, where the first information includes 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 sends second information to the first network element, where the second information includes the mapping relationship between the second network slice identification information of the visited 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 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. The second information is used to determine the user route selection policy URSP for the terminal device. The first network element and the second network element belong to the home network of the terminal device, and the first network is the visited network of the terminal device, or the first network element and the second network element belong to the visited network of the terminal device, and the first network is the home network of the terminal device.

[0041] 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.

[0042] Referring to the fifth aspect, in some implementation manners of the fifth aspect, the URSP includes the second network slice identification information of the access network.

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

[0044] Referring to the fifth aspect, in some implementation manners of the fifth aspect, the method further includes the following. The second network element receives the fifth information from the first network element, where the fifth information indicates the updated identification information of the network slice to which the terminal device subscribes. The second network element sends the sixth information to the first network element, where the sixth information includes the mapping relationship between the third network slice identification information of the access network and the second network slice identification information of the home network. The third network slice identification information of the access network is a subset of the first network slice identification information of the access 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.

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

[0047] According to the sixth aspect, a communication method is provided, including: The first network element sends first information to the second network element, where the first information includes the identification information of the home network and the first network slice identification information of the visited network. The first network element and the second network element belong to the visited network. The first network element receives second information from the second network element, and the second information includes the 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, the mapping relationship between the visited network slice identification information and the home network slice identification information can be obtained. This helps to generate the URSP for the terminal device so that the terminal device can normally access the services of the visited network.

[0049] Referring to the sixth aspect, in some implementation manners of the sixth aspect, the method further includes the following. The first network element sends second information to a third network element, the third network element belongs to a home network, the first network element receives, from the third network element, a user routing selection policy (URSP) of a terminal device determined based on the second information, and the URSP is to be used by the terminal device to access services of a visited network.

[0050] Referring to the sixth aspect, in some implementation manners of the sixth aspect, the URSP includes second network slice identification information of the visited network of the terminal device, and the second network slice identification information of the visited network is a subset of the first network slice identification information of the visited network.

[0051] Referring to the sixth aspect, in some implementation manners of the sixth aspect, the method further includes the following. The first network element sends third information to a third network element, and the third information includes first network slice identification information of the visited network of the terminal device.

[0052] Referring to the sixth aspect, in some implementation manners 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 including the following is provided. A third network element receives second information from a first network element, where the second information includes a mapping relationship between first network slice identification information of a visited network and first network slice identification information of a home network. The third network element belongs to the home network, the first network element belongs to the visited network, and 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 between visited network slice identification information and home network slice identification information can be obtained. This helps to generate a URSP for the terminal device so that the terminal device can normally access services of the visited network.

[0055] Referring to the seventh aspect, in some implementation manners of the seventh aspect, the method further includes the following. The third network element obtains identification information of the network slice to which the terminal device subscribes. 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 subscribes. The URSP includes second network slice identification information of the visited network of the terminal device, and the second network slice identification information of the visited network is a subset of the first network slice identification information of the visited network.

[0056] Referring to the seventh aspect, in some implementation manners of the seventh aspect, the method further includes the following. The third network element obtains updated identification information of the network slice to which the terminal device belongs, 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 belongs.

[0057] Referring to the seventh aspect, in some implementation manners of the seventh aspect, the method further includes the following. The third network element sends the updated URSP of the terminal device to the first network element.

[0058] Referring to the seventh aspect, in some implementation manners 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 configured to implement the above method is provided. The communication device may be a policy control entity in the first aspect to the seventh aspect, or a device including a policy control entity, or the communication device may be a network slice selection entity or a mobility management entity in the first aspect to the seventh aspect, or a device including a network slice selection entity or a 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 executing corresponding software. The hardware or software includes one or more modules or units corresponding to the above functions.

[0060] Referring to the eighth aspect, in some possible implementation manners, the communication device may include a processing module and a transceiver module. The transceiver module, which may also be referred to as a transceiver unit, is configured to implement the transmission function and / or the reception function in any one of the above aspects and any one of the possible implementation manners 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 function in any one of the above aspects and any one of the possible implementation manners of the above aspects. The processing module may be, for example, a processor.

[0061] Referring to the eighth aspect, in some possible implementation manners, the transceiver module includes a transmission module and a reception module that are respectively configured to implement the transmission function and the reception function in any one of the above aspects and any one of the possible implementation manners of the above aspects.

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

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

[0064] Referring to the ninth aspect, in a possible implementation manner, 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 may include a chip and other discrete components.

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

[0066] Referring to the tenth aspect, in a possible implementation manner, 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 may include a chip and other discrete components.

[0067] According to the 11th aspect, a communication system is provided that includes a first network element and a second network element in the 4th aspect. The first network element is configured to transmit first information to the second network element, and the first information includes 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 belongs. The second network element is configured to transmit second information to the first network element, and the second information includes 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 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 belongs. 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 home network of the terminal device, and the first network is the visited network of the terminal device, or the first network element and the second network element belong to the visited network of the terminal device, and the first network is the home network of the terminal device.

[0068] Referring to the 11th aspect, in some implementation manners of the 11th 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 or a mobility management network element belonging to the home network, and the system further includes a third network element, where the third network element is a policy control network element belonging to the visited network. The third network element is configured to send third information to the first network element, and the third information includes first network slice identification information of the visited network of the terminal device. The first network element sends the user root selection policy URSP of the terminal device to the third network element, and the URSP will be used by the terminal device to access the services of the visited network.

[0069] Referring to the 11th aspect, in some other implementation manners 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 a mobility management network element belonging to the visited network, the system further includes a third network element, and the third network element is a mobility management network element belonging to the visited network. The third network element is configured to send fourth information to the first network element, and the fourth information includes updated identification information of the network slice to which the terminal device subscribes. The first network element is further configured to send fifth information to the second network element, and the fifth information 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.

[0070] Referring to the 11th aspect, in some other implementation manners of the 11th aspect, the system further includes a fourth network element, and the fourth network element is a policy control network element belonging to the home network. The fourth network element is configured to receive second information from the first network element and send the user root selection policy URSP of the terminal device to the first network element, and the URSP will be used by the terminal device to access the services of the visited network.

[0071] According to the 12th aspect, a communication system is provided. The communication system includes the first network element and the second network element in the 6th aspect. The first network element and the second network element belong to the visited network. The first network element is configured to send the first information to the second network element, and the first information includes the identification information of the home network and the first network slice identification information of the visited network. The second network element is configured to send the second information to the first network element, and the second information includes the 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 12th aspect, in some implementation manners of the 12th aspect, the system further includes a third network element, and the third network element belongs to the home network. The third network element is configured to receive the second information from the first network element, and the second information includes the mapping relationship between the first network slice identification information of the visited network and the first network slice identification information of the home network. The third network element belongs to the home network, the first network element belongs to the visited network, and is configured to send the user root selection policy URSP of the terminal device to the first network element. The URSP is to be used by the terminal device to access the services of the visited network. The third network element is further configured to obtain the identification information of the network slice to which the terminal device subscribes, and determine the URSP of the terminal device based on the second information and the identification information 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 can execute 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 may be packaged separately from the processor. This is not particularly limited in the embodiments of this application.

[0075] According to the 14th 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 can execute the method in the above aspect.

[0076] According to the 15th aspect, a chip system including a memory and a processor is provided. The memory is configured to store a computer program, and the processor is configured to call the computer program from the memory and execute the computer program. As a result, the communication device in which the chip system is installed can execute the method in any one of the 1st to 7th aspects and the possible implementation manners of the 1st to 7th 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 Description of the Drawings

[0078]

Figure 1

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Embodiments for Carrying Out the Invention

[0079] Hereinafter, with reference to the accompanying drawings, the technical solution of this application will be described.

[0080] FIG. 1 is a schematic diagram of a communication system according to this application. As shown in FIG. 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 execute a communication method in an embodiment of this application.

[0081] The first network element 110 is configured to transmit first information to the second network element 120. The first information includes 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 first network element 110 is configured to receive second information from the second network element 120. The second information includes 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 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. The second information is used to determine a user route selection policy URSP for the terminal device. 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 explained 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. That 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 may be explained as follows. The first network slice identification information of the home network includes some or all of the information within the identification information 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 transmit second information to the first network element 110.

[0083] The first network element and the second network element belong to a 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 a home network.

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

[0085] Optionally, the fourth network element 140 is configured to receive second information from the first network element 110 and transmit the user root selection policy URSP of the terminal device to the first network element 110, and the URSP will be used by the terminal device to access the services of the visited network.

[0086] For example, according to the communication system provided in this application, a mapping relationship between the visited 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 visited network.

[0087] The system 100 shown in FIG. 1 may be applied to the 5th generation (5G) network architecture shown in FIG. 2 or FIG. 3, and obviously, it may also be applied to future network architectures, for example, the 6th generation (6G) network architecture. This is not particularly limited in the embodiments of this application.

[0088] For example, assume that the communication system shown in FIG. 1 is applied to the 5G network shown in FIG. 2 or FIG. 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) 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 is a policy control network element (V-PCF) belonging to the visited network. In this implementation, the fourth network element 140 does not exist. 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 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.

[0089] Hereinafter, the 5G system in different scenarios will be described by using the examples with reference to FIGS. 2 and 3. It should be understood that the 5G system described in this specification is merely an example and should not constitute any limitation to this application.

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

[0091] The main functions of the network elements are described as follows.

[0092] 1. Terminal device

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

[0094] The terminal device may be a device that provides voice and data connections to the user, for example, a handheld device or an in-vehicle device having a wireless connection function. Currently, some examples of terminals are 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 grid, wireless terminals in transportation safety, wireless terminals in smart city, wireless terminals in smart home, mobile phones, cordless phones, session initiation protocol (SIP) phones, wireless local loop (WLL) stations, personal digital assistants (PDAs), handheld devices having a wireless communication function, computing devices or other processing devices connected to a wireless modem, in-vehicle devices, wearable devices, terminal devices in future 5G networks, terminal devices in future evolved public land mobile networks (PLMNs), etc. This is not limited in the embodiments of this application.

[0095] By way of example and not limitation, in embodiments of this application, the terminal device may alternatively be a wearable device. A wearable device may also be referred to as a wearable intelligent device, etc., and is a general term for wearable devices that are intelligently designed and developed for daily wear by using wearable technologies, such as glasses, gloves, watches, clothes, and shoes. A wearable device is a portable device that is worn directly on the user's body or incorporated into the user's clothes or accessories. A wearable device is not only a hardware device, but also realizes powerful functions through software support, data exchange, and cloud interaction. General-purpose wearable intelligent devices include full-function large devices that can realize complete or partial functions without relying on a smartphone, such as smartwatches or smart glasses, and devices that need to operate with other devices such as smartphones with a focus on only one type of application function, such as various smart bands or smart jewelry for monitoring physical signs. Further, in embodiments of this application, the terminal device may alternatively be a terminal device in an internet of things (IoT) system.

[0096] 2. Radio Access Network RAN

[0097] A radio access network is an access network that realizes a network access function based on wireless communication technology. The radio access network manages radio resources, provides a wireless access service or an air interface access service to a terminal, and can transfer control signals and user data between the terminal and the core network.

[0098] By way of example and not limitation, the radio access network may be an evolved NodeB (eNB) in an LTE system, or a radio controller in a cloud radio access network (CRAN) scenario, or the access device may be a relay station, an access point, an in-vehicle device, a wearable device, an access device in a 5G network, an access device in a future evolved PLMN network, an access point (AP) in a WLAN, or a gNB in an NR system. This is not limited in 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 mainly used for mobility management, access management, etc., and may be configured to implement other functions in the mobility management entity (MME) function other than session management, such as functions like lawful interception or access permission (or authentication), and is further configured to transfer user policies between the UE and the PCF. In the 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] The session management function network element is mainly used for session management, Internet Protocol (IP) address assignment and management of terminal devices, user plane function (UPF) network element selection, the end point of the policy control and charging function interface, downlink data notification, etc. In the embodiments of this application, the session management function network element may be configured to implement the functions of the session management network element.

[0103] 5. User Plane Function Network Element UPF

[0104] The user plane function network element 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 the embodiments of this application, the user plane function network element may be configured to implement the functions of the user plane network element. For example, when sessions are created on different UPFs, the service experience of the UE is also different. Therefore, the SMF needs to select an appropriate UPF for the UE's session.

[0105] 6. Policy Control Network Element PCF

[0106] The policy control network element is configured to guide the unified policy framework of network behavior and provide policy rule information for control plane function network elements (such as the AMF network element or the SMF network element), etc. The policy control network element is mainly responsible for policy control functions such as session-level and service flow-level charging, QoS bandwidth guarantee, mobility management, and UE policy determination.

[0107] 7. Network Exposure Function Network Element NEF

[0108] The Network Exposure Function Network Element is configured to expose services and network capability information (such as whether the terminal location and session are reachable, etc.) provided by 3GPP network functions to the outside.

[0109] 8. Application Function Network Element AF

[0110] The Application Function Network Element is mainly configured to transfer application - side requirements for the network side, such as QoS requirements or subscription to user - state events. AF can be a third - party function entity or an application service deployed by an operator, such as an IMS voice call service. When the application function entity of a third - party application interacts with the core network, NEF may further perform authorization processing. For example, the third - party application function directly sends a request message to NEF, and NEF determines whether AF is permitted to send the request message. If the verification is successful, the request message is transferred 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 mainly used for unified data management and supports authentication trust state processing in the 3GPP authentication and key agreement mechanism, user identity processing, access authorization, registration and mobility management, subscription management, SMS message management, etc.

[0113] 10. Unified Data Repository Network Element UDR

[0114] The unified data repository network element is mainly used for the access function of types of data such as subscribed data, policy data, and application data.

[0115] In the above architecture, the functions of the interfaces are described as follows.

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

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

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

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

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

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

[0122] N1 represents the interface between the AMF and the UE, is access-independent, and is configured to, among other things, send QoS control rules to the UE.

[0123] N8 represents the interface between the AMF and the UDM, and is used by the AMF to obtain subscription data related to access and mobility management and authentication data from the UDM, and is used by the AMF to register the current mobility management related information of the UE with the UDM.

[0124] N10 represents the interface between the SMF and the UDM, and is used by the SMF to obtain subscription data related to session management from the UDM, and is used by the SMF to register the current session related information of the UE with the UDM.

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

[0126] The above-described network architecture applied to the embodiments of this application is merely an example of a network architecture described from the perspective of a conventional point-to-point architecture and a service-oriented architecture, 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 implementing the functions of the above-described network elements is applicable to the embodiments of this application.

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

[0128] It should be noted that network elements may also be referred to as entities, devices, apparatuses, 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, the SMF network element is abbreviated as SMF. In this case, "SMF" should be understood as the SMF network element. In the following, the descriptions of the same or similar cases are omitted.

[0129] It can be understood that the above-mentioned network elements or functions may also be network elements within a hardware device, software functions executed on dedicated hardware, or virtualized functions instantiated on a platform (such as a cloud platform). Optionally, the above-mentioned network elements or functions may be implemented by one device, may be implemented by multiple devices, or may be one functional module within one device. This is not particularly limited in the embodiments of this application.

[0130] In the communication system shown in FIG. 2, it should be further understood that the functions of the constituent network elements are merely examples. When the constituent network elements are applied to the embodiments of this application, not all functions are necessary.

[0131] Furthermore, the names of the network elements (such as PCF and AMF) included in FIG. 2 are merely names, and the names do not constitute a limitation on the functions of the network elements. In 5G networks and other future networks, the above network elements may alternatively have other names. This is not particularly limited in the embodiments of this application. For example, in a 6G network, some or all of the above network elements may still use the terms in 5G, or may have other names. A general description is provided here. Details will not be described again below.

[0132] The communication between the network elements of the control plane function in FIG. 2 is described by way of example as using a non-service-oriented interface, but it should be further noted that this does not constitute a limitation on the protection scope of the embodiments of this application. Those skilled in the art can understand that the network elements of the control plane function in FIG. 2 may alternatively communicate with each other through a service-oriented interface. For example, 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, and the external service-oriented interface provided by PCF may be Npcf.

[0133] The network elements in FIG. 2 are based on a reference point architecture and do not constitute a limitation on the embodiments of this application. FIG. 3 is a schematic diagram of an architecture based on a service-oriented interface. As shown in FIG. 3, the architecture includes NSSF, AUSF, UDM, NEF, NRF, PCF, AF, AMF, SMF, UE, RAN, UPF, DN, etc. In FIG. 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, the external service-oriented interface provided by CHF may be Nchf, and the interface between the control plane function and either RAN or UPF is a non-service-oriented interface. The UE is connected to the AMF through the N1 interface, and the UE is connected to the RAN by using the radio resource control (RRC) protocol. The RAN is connected to the AMF through the N2 interface, and the RAN is connected to the UPF through the N3 interface. The UPF is connected to the DN through the N6 interface, and the UPF is connected to the SMF through the N4 interface. For related descriptions, refer to the 5G system architecture in the standard. For the sake of brevity, the connection relationships in architecture 300 are not described here.

[0134] In the 5G era, hundreds of billions of Internet of Things devices access the network, and different types of application scenarios have different requirements for the network, and some requirements even conflict with each other. Therefore, when a single network is used to provide services for different types of application scenarios at the same time, the network architecture is extremely complex, and the network management efficiency and resource utilization rate are low. The 5G network slicing technology provides a network environment separated from each other for different application scenarios by virtualizing independent logical networks on the same network infrastructure. As a result, the network functions and characteristics can be customized for different application scenarios based on their respective requirements, so that the quality of service (QoS) requirements of different services can be effectively ensured.

[0135] When the network slice is deployed in the core network, when the UE first attaches to the network, the network slice selection process is triggered. The slice selection process depends on the UE's subscription data, local configuration information, roaming agreement, operator's policy, etc. In the network slice selection process, the above parameters need to be comprehensively considered to select the optimal slice type for the UE.

[0136] The network slice identifier includes the S-NSSAI and the NSSAI. The S-NSSAI represents the assistance information of a single slice and usually includes a slice / service type (SST) and a slice differentiator (SD). The SST is used to characterize the slice from the perspectives of characteristics and services. The SD is used to distinguish between different network slices having the same SST characteristics. The NSSAI is a set of S-NSSAIs, and multiple network slices may be identified by using the NSSAI. In a 5G network, the NSSAI may be a configured NSSAI, a requested NSSAI, or an allowed NSSAI.

[0137] When the UE needs to access a slice, the UE may provide the requested NSSAI to the core network, so that the core network selects a network slice instance for the UE. Specifically, the UE may provide network slice selection assistance information (NSSAI) including a group of parameters to the core network, and the core network selects a network slice instance for the UE.

[0138] The UE registration procedure may be briefly described as follows. The UE sends a registration request to the AMF through the RAN, and the AMF obtains the UE's subscription data from the UDM based on the UE identifier. The UDM may obtain the subscription data from the UDR after receiving the request. Further, the AMF may separately initiate a user policy control creation request (UE PolicyControl_Create) and an access management policy control creation request (AM PolicyControl_Create) to the PCF to separately obtain the UE policy and the access control policy. In this process, the PCF returns the UE policy and the access control policy to the AMF, and the AMF provides the UE policy and the 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 through 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 the session creation request to the SMF, the SMF selects the corresponding UPF for the UE, establishes the 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. Further, 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 of an exemplary application scenario of a roaming scenario to which this application is applicable. The scenario includes at least an AMF, a PCF, and a UDR (abbreviated as V-AMF, V-PCF, and V-UDR, respectively) located in the VPLMN, and a PCF (abbreviated as H-PCF) located in the HPLMN. In the architecture shown in Figure 4, the network elements may communicate with each other through service-oriented interfaces. For details, refer to the description in Figure 2 or Figure 3. For the sake of brevity, the details are not described again here.

[0141] S410: The V-AMF determines that the UE is roaming and is registered in the VPLMN.

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

[0143] The first request message may be a user policy control creation request message (Npcf_UEPolicyControl Create Request), and is used to request the V-PCF to create a UE policy association.

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

[0145] The UE policy support information corresponding to the visited location may be VPLMN supported UE policy information. The information may include the 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 in multiple ways. For example, the V-PCF may obtain the VPLMN supported UE policy information from the V-UDR. As another example, the VPLMN supported UE policy information is locally configured in the V-PCF.

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

[0147] The second request message may be a user policy control creation request message (Npcf_UEPolicyControl Create Request). The message includes the VPLMN supported UE policy information and is used to request the H-PCF to create a UE policy association.

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

[0149] The second response message may be a user policy control creation response message (Npcf_UEPolicyControl Create Response), and specifically includes the URSP generated by the H-PCF for the UE based on the VPLMN-assisted UE policy information.

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

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

[0152] When the H-PCF receives the VPLMN-assisted UE policy information, it can be understood that the H-PCF comprehensively generates the URSP by further considering the information related to the visited location. After the V-AMF sends the URSP to the UE, the UE may determine 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-assisted UE policy information is the VPLMN S-NSSAI, if the H-PCF directly includes the VPLMN S-NSSAI included in the VPLMN-assisted UE policy information in the URSP, the URSP includes both the VPLMN S-NSSAI and the 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 the 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 the visited network slice identification information of a UE and the home network slice identification information of the UE. This helps to generate a URSP for the UE so that the UE can normally access the services of the visited network.

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

[0156] S510: The first network element 110 transmits first information to the second network element 120, and the first information includes 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.

[0157] The first network element and the second network element belong to the home network, and the first network is the visited network, or the first network element and the second network element belong to the 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, and the second information includes the 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 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. The second information is used to determine the user root 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 explained 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 identification information of the home network is a subset of the identification information of the network slice to which the terminal device subscribes may be explained as follows. The first network slice identification information of the home network includes some or all of the information within the identification information of the network slice to which the terminal device subscribes.

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

[0161] In a possible implementation manner, the system in this application may further include a third network element 130 indicated by the dashed line in FIG. 1, and does not include a fourth network element 140 indicated by the dashed line in FIG. 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, and the third information includes first network slice identification information of the visited network. The first network element determines a user root selection policy URSP of the terminal device based on the second information and the third information, and the URSP will be used by the terminal device to access the services of 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 method, the first network element 110 may further receive fourth information, where the fourth information indicates updated identification information of a network slice to which the terminal device subscribes. The first network element 110 sends fifth information to the second network element 120. The fifth information 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 visited network slice identification information of the terminal device and the home network slice identification information of the terminal device can be reacquired based on the updated identification information of the network slice to which the terminal device subscribes. This helps to generate a URSP for the terminal device so that the terminal device can normally access the services of the visited network.

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

[0164] Optionally, in the above implementation method, the first network element 110 receives the fourth information from the third network element 130, the third information includes updated identification information of the network slice to which the terminal device subscribes, the first network element 110 sends the fifth information to the second network element 120, the fifth information 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 visited network slice identification information of the terminal device and the home network slice identification information of the terminal device can be reacquired based on the updated identification information of the network slice to which the terminal device subscribes. This helps to generate a URSP for the terminal device so that the terminal device can normally access the services of the visited network.

[0165] According to the technical solution of this application, the mapping relationship between the visited 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 visited 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, in this embodiment of this application, the communication method provided is such that 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. This is presented by using, for example, an example where the second network element 120 is a network slice selection network element (H-NSSF) belonging to the home 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 in this application. In Figure 6, only an example where the second network element 120 is a network slice selection network element (H-NSSF) belonging to the home network is used for the purpose of explanation.

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

[0168] Regarding the registration of the UE in the visited network, refer to the prior art. Details are not described here. For example, the visited network is VPLMN#1.

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

[0170] Specifically, the first request message may be a user policy control creation request message (Npcf_UEPolicyControl Create Request) and is used to request the V-PCF to create a UE policy association. Both the V-AMF and the V-PCF are located in the visited network VPLMN#1. The first request includes the subscription permanent identifier of the UE, for example, the subscription permanent identifier (SUPI).

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

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

Table 1

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

[0174] The second request message may be a user policy control creation request message (Npcf_UEPolicyControl Create Request). The second request message is used to request the creation of a UE policy association. The second request message includes UE policy support information (VPLMN assistant UE policy information) corresponding to the visited location. For the specific content of the information, refer to Table 1.

[0175] The V-PCF determines the UE's HPLMN ID based on the subscription permanent identifier included in the first request message, and determines the identifier of the H-PCF based on the HPLMN ID. Further, the second request message may further include the identifier of the V-PCF (V-PCF ID).

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

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

[0178] S606: The H-PCF sends the first information to the H-NSSF.

[0179] Specifically, in a possible implementation, the H-PCF sends a request message to the H-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 identifier information of the visited network (VPLMN ID), the first network slice identifier information of the visited network, and the identifier information of the network slice to which the UE subscribes (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 in 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 the V-PCF is located in VPLMN#1, as shown in Table 1, the VPLMN support 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, the H-PCF determines that the first network slice identification information of the visited network is VPLMN#1 S-NSSAI#1, VPLMN#2 S-NSSAI#2, and VPLMN#3 S-NSSAI#3.

[0181] Based on step S605, the H-PCF may obtain UE subscription information from the H-UDR. The UE subscription information includes information about the network slice to which the UE subscribes, and the information about the network slice to which the UE subscribes includes the HPLMN S-NSSAI. For example, the information about the network slice to which the UE subscribes may be HPLMN S-NSSAI#A and HPLMN S-NSSAI#B.

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

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

Table 2

[0184] The H-NSSF may determine the second information based on the first information, and the second information includes 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.

[0185] Example 1: For example, the information regarding the network slice to which the UE subscribes 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 (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 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, although VPLMN#1 S-NSSAI#3 can be mapped to HPLMN S-NSSAI#C, since the network slice to which the UE subscribes does not include HPLMN S-NSSAI#C, for the UE, the UE can access VPLMN#1 S-NSSAI#1 and VPLMN#1 S-NSSAI#2 only in VPLMN#1, but the UE is not permitted to access VPLMN#1 S-NSSAI#3 in VPLMN#1. In Example 1, the H-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 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 identification information of the visited network is VPLMN#1 S-NSSAI#1 and VPLMN#1 S-NSSAI#2, and the first network slice identification information of the home network is HPLMN S-NSSAI#A and HPLMN S-NSSAI#B.

[0186] Example 2: For example, the information regarding the network slice to which the UE subscribes 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, 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 2, the H-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 H-PCF. The second information includes 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. In other words, the second network slice identification information of 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 of the home network is HPLMN S-NSSAI#A, HPLMN S-NSSAI#B, and HPLMN S-NSSAI#C.

[0187] Example 3: For example, the information regarding 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 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 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, although 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, since the network slice to which the UE belongs does not include either HPLMN S-NSSAI#A or HPLMN S-NSSAI#C, for the UE, the UE can access VPLMN#1 S-NSSAI#2 only in VPLMN#1, but the UE is not permitted to access either VPLMN#1 S-NSSAI#1 or VPLMN#1 S-NSSAI#3 in VPLMN#1. In Example 3, the H-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 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 identification information of the visited network is VPLMN#1 S-NSSAI#2, and the first network slice identification information of the home network is HPLMN S-NSSAI#B.

[0188] As can be seen from the above Examples 1 to 3, the second network slice identification information of the visited network and the first network slice identification information of the home network included in the second information determined by the H-NSSF change together with the UE access information included in the first information. In Example 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, and the second network slice identification information of the visited network is VPLMN#1 S-NSSAI#1 and VPLMN#1 S-NSSAI#2. Therefore, the second network slice identification information of the visited network is a subset of the first network slice identification information of the visited network. In Example 2, 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, and the second network slice identification information 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 identification information of the visited network is the universal set of the first network slice identification information of the visited network. In the embodiments of this application, the universal set is also a type of subset. Therefore, the second network slice identification information of the visited network may still be referred to as a subset of the first network slice identification information of the visited network. In Example 3, 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, and the second network slice identification information of the visited network is VPLMN#1 S-NSSAI#2. Therefore, the second network slice identification information of the visited network is a subset of the first network slice identification information of the visited network.

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

Table 3-1

Table 3-2

Table 3-3

[0190] After the H-NSSF determines the second information, the H-NSSF may send the second information to the H-PCF by using a response message. In an implementation manner, the response message may be a Network Slice Mapping Information Response message or a Service-Oriented Operation Nnssf_NSSelection_Get Response. This is not limited in this application.

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

[0192] The H-PCF obtains UE context policy control data from the H-UDR. The UE context policy control data includes the DNN, SSC mode, and network slice information associated with the application deployed in the HPLMN, as shown in Table 4-0. The network slice associated with the application deployed in 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 Table 4-0 and the second piece of information.

[0194] For example, in Example 1, as shown in Table 3-1, the mapping relationships included in the second piece of 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. The H-PCF searches for UE policy support information (VPLMN assistant UE policy information) corresponding to the visited location shown in Table 1, and not only must the generated URSP contain information regarding the application deployed in the HPLMN in Table 4-0, but it may also be determined that it is necessary to further include information regarding the application deployed in the VPLMN, for example, Application#1 associated with VPLMN#1 S-NSSAI#1 and Application#2 associated with VPLMN#2 S-NSSAI#2. Since the second piece of 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, for example, HPLMN S-NSSAI#A and HPLMN S-NSSAI#B. Optionally, the generated URSP may further include the second network slice identification information of the visited network, for example, VPLMN#1 S-NSSAI#1 and VPLMN#1 S-NSSAI#2. For example, in this example, the information content included in the URSP may be as shown in Table 4-1. Application#1 and Application#2 are deployed in the VPLMN, Application#A is deployed in the HPLMN, and the network slice identification information 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 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. The H-PCF searches for UE policy support information (VPLMN assistant UE policy information) corresponding to the destination location shown in Table 1, and the generated URSP needs to include not only information regarding the application deployed in the HPLMN in Table 4-0, but may also further include information regarding the application deployed in the VPLMN, for example, 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 the second network slice identification information 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 content included in the URSP may be as shown in Table 4-2. Application#1, Application#2, and Application#3 are deployed in the VPLMN, Application#A is deployed in the HPLMN, and the network slice identification information 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 the mapping relationship between VPLMN#1 S-NSSAI#2 and HPLMN S-NSSAI#B. The H-PCF searches for UE policy support information (VPLMN assistant UE policy information) corresponding to the visited location shown in Table 1, and the generated URSP needs to include not only information regarding the application deployed in the HPLMN in Table 4-0, but may also further include information regarding the application deployed in the VPLMN, for example, 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 the 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 in the VPLMN, Application#A is deployed in the HPLMN, and the network slice identification information associated with Application#A is HPLMN S-NSSAI#B.

[0197] As can be seen from the above example, the URSP generated by the H-PCF changes together with the mapping relationship included in the second piece of information.

Table 4-1

Table 4-2

Table 4-3

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

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

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

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

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

[0203] 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.

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

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

[0206] The updated identification information of the network slice to which the UE subscribes may 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.

[0207] For example, in the above Example 1, 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.

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

[0209] The H-PCF may receive a notification message (Nudr_DM_Notify) from the H-UDR. The notification message may include fourth information, and the fourth information includes 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 the HPLMN S-NSSAI#A and HPLMN S-NSSAI#B shown in Example 1 above, to the HPLMN S-NSSAI#A, HPLMN S-NSSAI#B, and HPLMN S-NSSAI#C shown in Example 2 above, or to the HPLMN S-NSSAI#B shown in Example 3 above.

[0210] S613: The H-PCF sends fifth information to the H-NSSF.

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

[0212] Furthermore, the H-PCF may determine the VPLMN ID based on the identifier of the V-PCF, and the H-PCF may determine the first network slice identification information of the visited network from the UE policy support information corresponding to the visited location (VPLMN assistant UE policy information) based on step S604. For specific explanations, refer to the explanations in step 606. Details will not be described again here.

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

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

[0215] Example A: The VPLMN ID is VPLMN#1, and 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. When the updated identification information of the network slice to which the UE subscribes 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, 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. The H-NSSF sends the mapping relationship (i.e., the sixth piece of information) between the third network slice identification information of the visited network and the second network slice identification information of the home network to the H-PCF. The sixth piece of information includes 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. In other words, the third network slice identification information of the visited network is VPLMN#1 S-NSSAI#1, VPLMN#1 S-NSSAI#2, and VPLMN#1 S-NSSAI#3, and the second network slice identification information of the home network is HPLMN S-NSSAI#A, HPLMN S-NSSAI#B, and HPLMN S-NSSAI#C.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.

[0216] Example B: The VPLMN ID is VPLMN#1, and 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. When the updated identification information of the network slice to which the UE subscribes is updated from the HPLMN S-NSSAI#A and HPLMN S-NSSAI#B shown in Example 1 to the 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, although 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, and 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, 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] The above Examples A and B are merely intended to illustrate the technical solutions of this application and should not be construed as limitations to the technical solutions of this application. It can 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 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: The H-PCF generates a new URSP based on the sixth piece of information.

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

[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. The H-PCF searches for UE policy support information (VPLMN assistant UE policy information) corresponding to the visited location shown in Table 1, and the generated URSP needs to include not only information regarding the applications deployed in the HPLMN in Table 4-0, but may also further include information regarding the applications deployed in the VPLMN, for example, 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-NSSAIs, for example, HPLMN S-NSSAI#A, HPLMN S-NSSAI#B, and HPLMN S-NSSAI#C. Optionally, the generated URSP may further include the third network slice identification information 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 content included in the URSP may be as shown in Table 4-2. Application#1, Application#2, and Application#3 are deployed in the VPLMN, Application#A is deployed in the HPLMN, and the network slice identification information 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. The H-PCF searches for UE policy support information (VPLMN assistant UE policy information) corresponding to the visited location shown in Table 1, and the generated URSP needs to include not only information regarding the application deployed in the HPLMN in Table 4-0, but may also be determined to further include information regarding the application deployed in the VPLMN, for example, Application#1 associated with VPLMN#1 S-NSSAI#1. The generated URSP includes the HPLMN S-NSSAI, for example, HPLMN S-NSSAI#A. Optionally, the generated URSP may further include the third network slice identification information of the visited network, for example, 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 in the VPLMN, Application#A is deployed in the HPLMN, and the network slice identification information associated with Application#A is HPLMN S-NSSAI#B.

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

[0223] According to the technical solution of this application, after the identification information of the network slice to which the terminal device subscribes changes or is updated, the mapping relationship between the visited network slice identification information of the terminal device and the home network slice identification information of the terminal device can be reacquired based on the updated identification information of the network slice to which the terminal device subscribes. This helps to generate the URSP for the terminal device so that the terminal device can normally 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, in this embodiment provided by this application, the communication method uses an example where 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: The V-NSSF stores the network slice roaming agreement.

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

Table 5

[0227] S702: The V-AMF determines that the UE roams and is registered in the visited network.

[0228] S702 is the same as S601 and will not be described again in detail here.

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

[0230] 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 UE's SUPI and UE subscription information. The UE subscription information includes the identification information of the network slice to which the UE subscribes, and the identification information of the network slice to which the UE subscribes includes the HPLMN S-NSSAI. For example, the information about the network slice to which the UE subscribes may be HPLMN S-NSSAI#A and HPLMN S-NSSAI#B.

[0231] Furthermore, the method for V-AMF to obtain UE subscription information is as follows. V-AMF may send a query request message (Nudm_SDM_Get Request) to H-UDM, and the query request message is used to inquire about UE subscription information from H-UDM. Correspondingly, H-UDM may send a query response message (Nudm_SDM_Get Response) to V-AMF, and the query response message includes the UE subscription information.

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

[0233] S704 is the same as S603 and will not be described again in detail here.

[0234] S705:V-PCF sends the first information to V-NSSF.

[0235] Specifically, in a possible implementation manner, 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. This is not limited in this application. The request message includes first information. The first information includes the identification information of the home network (HPLMN ID), the first network slice identification information of the visited network, and the identification information of the network slice to which the UE subscribes (S-NSSAI).

[0236] The V-PCF may determine the identification information of the UE's home network (HPLMN ID) by using the UE's SUPI. For example, the HPLMN ID may be HPLMN#1. The V-PCF may determine the first network slice identification information of the visited network from the visited network's UE policy assistance information (VPLMN assistant UE policy information) based on step S704. For example, when the V-PCF is located in VPLMN#1, as shown in Table 1, the VPLMN assistance 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, the V-PCF determines that the first network slice identification information 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 subscribes based on step S703. The information regarding the network slice to which the UE subscribes includes the HPLMN S-NSSAI. For example, the information regarding the network slice to which the UE subscribes may be HPLMN S-NSSAI#A and HPLMN S-NSSAI#B.

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

[0239] The V-NSSF may determine the second information based on the first information, and the second information includes 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.

[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 (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 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, although VPLMN#1 S-NSSAI#3 can be mapped to HPLMN S-NSSAI#C, since the network slice to which the UE belongs does not include HPLMN S-NSSAI#C, for the UE, the UE can access VPLMN#1 S-NSSAI#1 and VPLMN#1 S-NSSAI#2 only in VPLMN#1, but the UE is not permitted to access VPLMN#1 S-NSSAI#3 in VPLMN#1. In Example a, the V-NSSF sends the mapping relationship (i.e., the second piece of information) between the identification information of the second network slice of the visited network and the identification information of the first network slice of the home network to the V-PCF. The second piece of 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 identification information of the second network slice of the visited network is VPLMN#1 S-NSSAI#1 and VPLMN#1 S-NSSAI#2, and the identification information of the first network slice of the home network is HPLMN S-NSSAI#A and HPLMN S-NSSAI#B.

[0241] Example b: For example, the information regarding 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 belongs 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 information includes 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. In other words, the second network slice identification information of 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 of the home network is HPLMN S-NSSAI#A, HPLMN S-NSSAI#B, and HPLMN S-NSSAI#C.

[0242] Example c: For example, the information regarding 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 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 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, although 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, since the network slice to which the UE belongs does not include either HPLMN S-NSSAI#A or HPLMN S-NSSAI#C, for the UE, the UE can access only VPLMN#1 S-NSSAI#2 in VPLMN#1, but the UE is not permitted to access either VPLMN#1 S-NSSAI#1 or VPLMN#1 S-NSSAI#3 in VPLMN#1. In Example c, the V-NSSF sends the mapping relationship (i.e., the second piece of 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 piece of information includes the mapping relationship between VPLMN#1 S-NSSAI#2 and HPLMN S-NSSAI#B. In other words, the second network slice identification information of the visited network is VPLMN#1 S-NSSAI#2, and the first network slice identification information of the home network is HPLMN S-NSSAI#B.

[0243] As can be seen from the above Examples a to c, the second network slice identification information of the visited network and the first network slice identification information of the home network included in the second information determined by the V-NSSF change together with the UE access information included in the first information. In Example a, 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, and the second network slice identification information of the visited network is VPLMN#1 S-NSSAI#1 and VPLMN#1 S-NSSAI#2. Therefore, the second network slice identification information of the visited network is a subset of the first network slice identification information of the visited network. In Example b, 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, and the second network slice identification information 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 identification information of the visited network is the universal set of the first network slice identification information of the visited network. The universal set is also a type of subset. Therefore, the second network slice identification information of the visited network may still be referred to as a subset of the first network slice identification information of the visited network. In Example c, 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, and the second network slice identification information of the visited network is VPLMN#1 S-NSSAI#2. Therefore, the second network slice identification information of the visited network is a subset of the first network slice identification information of the visited network.

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

[0245] After determining the second piece of information, the V-NSSF may send the second piece of information to the V-PCF by using a response message. In an implementation manner, the response message may be a Network Slice Mapping Information Response message or a Service-Oriented Operation Nnssf_NSSelection_Get Response. This is not limited in this application.

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

[0247] The second request message may be a User Policy Control Creation Request message (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 piece of information and UE policy assistance information (VPLMN assistant UE policy information) corresponding to the visited location.

[0248] The V-PCF determines the UE's HPLMN ID based on the subscription permanent identifier included in the first request message, and determines the identifier of the H-PCF based on the HPLMN ID. Further, the second request message may further include the identifier of the V-PCF (V-PCF ID).

[0249] Optionally, the UE policy assistance information (VPLMN assistant UE policy information) corresponding to the destination location sent by the V-PCF to the H-PCF may be processed by the 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 identification information of the destination network is VPLMN#1 S-NSSAI#1 and VPLMN#1 S-NSSAI#2, and the first network slice identification information of the home network is HPLMN S-NSSAI#A and HPLMN S-NSSAI#B. When the identification information of the network slice to which the UE subscribes includes HPLMN S-NSSAI#A and HPLMN S-NSSAI#B, the V-PCF may filter the UE policy assistance information (VPLMN assistant UE policy information) corresponding to the destination location based on the identification information of the network slice to which the UE subscribes. 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 the HPLMN S-NSSAI#C that has a mapping relationship with the VPLMN#1 S-NSSAI#3, that is, the UE is not permitted to access the VPLMN#1 S-NSSAI#3 in VPLMN#1, in order to reduce signaling overhead and the computational load of the UE, before the V-PCF sends the UE policy support information corresponding to the visited location (VPLMN assistant UE policy information) to the H-PCF, the Application#3 associated with the VPLMN#1 S-NSSAI#3 may be deleted from the VPLMN-assisted UE policy information. As shown in Table 6-1, in Example a, the VPLMN-assisted UE policy information processed by the V-PCF includes only the information regarding Application#1 associated with the VPLMN#1 S-NSSAI#1 and the information regarding Application#2 associated with the VPLMN#1 S-NSSAI#2.

[0250] As another example, in Example c, the second information includes the mapping relationship between VPLMN#1 S-NSSAI#2 and HPLMN S-NSSAI#B. The second network slice identification information of the visited network is VPLMN#1 S-NSSAI#2, and the first network slice identification information of the home network is HPLMN S-NSSAI#B. When the identification information of the network slice to which the UE subscribes includes HPLMN S-NSSAI#B, the V-PCF may filter the UE policy support information (VPLMN assistant UE policy information) corresponding to the visited location based on the identification information of the network slice to which the UE subscribes. 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 subscribes does not include either HPLMN S-NSSAI#A having a mapping relationship with VPLMN#1 S-NSSAI#1 or HPLMN S-NSSAI#C having a mapping relationship with VPLMN#1 S-NSSAI#3, that is, 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 of the UE, before the V-PCF sends the UE policy support information (VPLMN assistant UE policy information) corresponding to the visited location to the H-PCF, Application#1 associated with VPLMN#1 S-NSSAI#1 and Application#3 associated with VPLMN#1 S-NSSAI#3 may be deleted from the VPLMN-assisted UE policy information.As shown in Table 6-2, in Example a, the VPLMN-assisted UE policy information processed by the V-PCF includes only the information regarding 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 of 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 of the home network is HPLMN S-NSSAI#A, HPLMN S-NSSAI#B, and HPLMN S-NSSAI#C. When the information regarding the network slice to which the UE subscribes may also be HPLMN S-NSSAI#A, HPLMN S-NSSAI#B, and HPLMN S-NSSAI#C, the information regarding the network slice to which the UE subscribes 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 (VPLMN assistant UE policy information) corresponding to the visited location based on the identification information of the network slice to which the UE subscribes. In other words, the VPLMN-assisted UE policy information is still shown in Table 1 and does not change. In this case, in Example b, the VPLMN-assisted UE policy information includes the information regarding Application#1 associated with VPLMN#1 S-NSSAI#1, the information regarding Application#2 associated with VPLMN#1 S-NSSAI#2, and the information regarding 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, refer to step S608. H-PCF may obtain UE context policy control data from H-UDR. The information included in the UE context policy control data may be as shown in Table 4-0. The network slice associated with the application deployed in the HPLMN is the HPLMN S-NSSAI, for example, HPLMN S-NSSAI#B.

[0254] H-PCF may generate the UE's URSP based on Table 4-0 and the second piece of information.

[0255] For example, in the scenario of Example a, the mapping relationships included in the second piece of 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. The H-PCF searches for UE policy support information (VPLMN assistant UE policy information) corresponding to the visited location, and the generated URSP not only needs to include information about the applications deployed in the HPLMN as shown in Table 4-0, but may also further include information about the applications deployed in the VPLMN, for example, Application#1 associated with VPLMN#1 S-NSSAI#1 and Application#2 associated with VPLMN#2 S-NSSAI#2. Since the second piece of 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, for example, HPLMN S-NSSAI#A and HPLMN S-NSSAI#B. Optionally, the generated URSP may further include the second network slice identification information of the visited network, for example, VPLMN#1 S-NSSAI#1 and VPLMN#1 S-NSSAI#2. In the scenario of Example a, the information content included in the URSP may be as shown in Table 4-1. Application#1 and Application#2 are deployed in the VPLMN, Application#A is deployed in the HPLMN, and the network slice identification information associated with Application#A is HPLMN S-NSSAI#B.

[0256] In the scenario of 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 H-PCF searches for UE policy support information (VPLMN assistant UE policy information) corresponding to the visited location shown in Table 1, and the generated URSP needs to include not only information regarding the applications deployed in the HPLMN in Table 4-0, but also information regarding the applications deployed in the VPLMN, for example, 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. It may also be determined that the generated URSP further includes HPLMN S-NSSAIs, for example, HPLMN S-NSSAI#A, HPLMN S-NSSAI#B, and HPLMN S-NSSAI#C. Optionally, the generated URSP may further include the second network slice identification information of the visited network, for example, VPLMN#1 S-NSSAI#1, VPLMN#1 S-NSSAI#2, and VPLMN#1 S-NSSAI#3. The information content included in the URSP may be as shown in Table 4-2. Application#1, Application#2, and Application#3 are deployed in the VPLMN, Application#A is deployed in the HPLMN, and the network slice identification information 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. The H-PCF searches for UE policy support information corresponding to the visited location (VPLMN assistant UE policy information), and the generated URSP needs to include not only information regarding the application deployed in the HPLMN as shown in Table 4-0, but may also further include information regarding the application deployed in the VPLMN, for example, Application#2 associated with VPLMN#1 S-NSSAI#2. The generated URSP includes an HPLMN S-NSSAI, for example, HPLMN S-NSSAI#B. Optionally, the generated URSP may further include the second network slice identification information of the visited network, for example, VPLMN#1 S-NSSAI#2. The information content included in the URSP may be as shown in Table 4-3. Application#2 is deployed in the VPLMN, Application#A is deployed in the HPLMN, and the network slice identification information associated with Application#A is HPLMN S-NSSAI#B.

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

[0259] The second response message may be a user policy control creation response message (Npcf_UEPolicyControl Create Response), and the second response message includes the URSP generated by the H-PCF. For example, the URSP generated by the H-PCF may be any one of Table 4-1, Table 4-2, and Table 4-3.

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

[0261] The first response message may be a user policy control creation response message (Npcf_UEPolicyControl Create Response), and the first response message includes a URSP generated by the H-PCF.

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

[0263] According to the technical solution of this application, a mapping relationship between the visited 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 visited 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: The V-AMF determines that the identification information of 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 is 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 fourth information, and the fourth information includes the updated identification information of the network slice to which the UE subscribes. By way of non-limiting example, 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 SUPI of the UE.

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

[0272] Specifically, for this process, refer to step S705. The fifth piece of information includes the HPLMN ID, the first network slice identification information of the visited network, and the updated identification information 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 identification information of the visited network and the network slice identification information of the home network), and the new mapping relationship is determined based on the updated identification information of the network slice to which the UE subscribes.

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

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

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

[0276] Example 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. When the identification information of the network slice to which the UE subscribes 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, 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. The V-NSSF sends the mapping relationship (i.e., the sixth piece of information) between the third network slice identification information of the visited network and the second network slice identification information of the home network to the V-PCF. The sixth piece of information includes 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. In other words, the third network slice identification information of the visited network is VPLMN#1 S-NSSAI#1, VPLMN#1 S-NSSAI#2, and VPLMN#1 S-NSSAI#3, and the second network slice identification information of the home network is HPLMN S-NSSAI#A, HPLMN S-NSSAI#B, and HPLMN S-NSSAI#C.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.

[0277] Example 2: 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. When the updated identification information of the network slice to which the UE subscribes 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, although 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, and 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, 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] It should be understood that the above Examples 1 and 2 are merely intended to illustrate the technical solutions of this application and should not be used as limitations to the technical solutions of this application. It can 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 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: The VPCF sends a third request message to the 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 message (Npcf_UEPolicyControl Update Request). The update request message includes sixth information, and 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.

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

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

[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. The H-PCF searches for UE policy support information (VPLMN assistant UE policy information) corresponding to the visited location shown in Table 1, and the generated URSP needs to include not only information regarding the applications deployed in the HPLMN in Table 4-0, but may also further include information regarding the applications deployed in the VPLMN, for example, 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-NSSAIs, for example, HPLMN S-NSSAI#A, HPLMN S-NSSAI#B, and HPLMN S-NSSAI#C. Optionally, the generated URSP may further include the third network slice identification information 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 content included in the URSP may be as shown in Table 4-2. Application#1, Application#2, and Application#3 are deployed in the VPLMN, Application#A is deployed in the HPLMN, and the network slice identification information 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. The H-PCF searches for UE policy support information (VPLMN assistant UE policy information) corresponding to the visited location shown in Table 1, and the generated URSP needs to include information regarding the application deployed in the HPLMN in Table 4-0, and may further determine that it needs to include information regarding the application deployed in the VPLMN, for example, Application#1 associated with VPLMN#1 S-NSSAI#1. The generated URSP includes an HPLMN S-NSSAI, for example, HPLMN S-NSSAI#A. Optionally, the generated URSP may further include the third network slice identification information of the visited network, for example, 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 in the VPLMN, Application#A is deployed in the HPLMN, and the network slice identification information associated with Application#A is HPLMN S-NSSAI#B.

[0285] Although not shown in the drawings, after generating a new URSP, the H-PCF may send a third response message to the V-PCF. The third response message may be a user policy control update notification request message (Npcf_UEPolicyControl UpdateNotify Request), and the message includes the new URSP. The V-PCF may further send the new URSP to the V-AMF by using the user policy control update notification request message (Npcf_UEPolicyControl UpdateNotify Request), and it should be understood that the V-AMF sends the URSP to the UE so that the UE can access the services of the visited network. For example, the V-AMF sends the URSP to the UE by 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 the terminal device subscribes changes or is updated, the mapping relationship between the visited network slice identification information of the terminal device and the home network slice identification information of the terminal device can be reacquired based on the updated identification information of the network slice to which the terminal device subscribes. This helps to generate a URSP for the terminal device so that the terminal device can normally access the services of the visited network.

[0287] FIG. 8 is a schematic flowchart of a third specific example of the communication method according to this application. In the method shown in FIG. 8, in this embodiment provided by this application, the communication method is presented by 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 in this application. In FIG. 8, only an 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 illustration.

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

[0289] S801 is the same as S701, and the details will not be described again here.

[0290] S802: The V-AMF determines that the UE roams and is registered in 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 UE's SUPI. 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 acquires 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] The V-PCF may determine the identification information (HPLMN ID) of the UE's home network by using the UE's SUPI. For example, the HPLMN ID may be HPLMN#1. The V-PCF may determine the first network slice identification information of the visited network from the visited network UE policy assistance information (VPLMN assistant UE policy information) based on step S804. For example, when the visited network identification information VPLMN ID of the V-PCF is VPLMN#1, the first network slice identification information of the visited network may be VPLMN#1 S-NSSAI#1, VPLMN#1 S-NSSAI#2, and VPLMN#1 S-NSSAI#3.

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

[0300] The V-NSSF may determine the second information based on the first information, and the second information includes the 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 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 7), and the first network slice identification information of the home location includes HPLMN S-NSSAI#A, HPLMN S-NSSAI#B, and HPLMN S-NSSAI#C. In this case, 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, the V-NSSF sends the mapping relationship (i.e., the second information) between the first network slice identification information of the visited network and the first network slice identification information of the home network to the V-PCF. As shown in Table 7, the second information includes 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.

Table 7

[0302] After determining the second information, the V-NSSF may send the second information to the V-PCF by using a response message. In an implementation manner, the response message may be a network slice mapping information response message (Slice mapping information Response) or a service-oriented operation Nnssf_NSSelection_Get Response. This is not limited in this application.

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

[0304] The second request message may be a user policy control creation request message (Npcf_UEPolicyControl Create Request). The second request message is used to request the creation of a UE policy association. The second request message includes second information and UE policy assistance 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 subscription permanent identifier included in the first request message, and determines the identifier of the H-PCF based on the HPLMN ID. Further, the second request message may further include the identifier of the V-PCF (V-PCF ID).

[0306] S808: The H-PCF obtains the identification information of the network slice to which the UE subscribes.

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

[0308] S809: The H-PCF generates the URSP of the UE.

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

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

[0311] Example M: The second information includes 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. The information regarding the network slice to which the UE subscribes is HPLMN S-NSSAI#A and HPLMN S-NSSAI#B. In this case, the H-PCF may determine that the second network slice identification information of the visited network is VPLMN#1 S-NSSAI#1 and VPLMN#1 S-NSSAI#2. Therefore, the second network slice identification information of the visited network is a subset of the first network slice identification information of the visited network. After determining the second network slice identification information of the visited network, the H-PCF searches for VPLMN-assisted UE policy information, and the generated URSP needs to include not only the information regarding the application deployed in the HPLMN in Table 4-0, but also the information regarding the application deployed in the VPLMN, for example, Application#1 associated with VPLMN#1 S-NSSAI#1 and Application#2 associated with VPLMN#2 S-NSSAI#2 may also be further included. Since the information regarding the network slice to which the UE subscribes does not include HPLMN#1 S-NSSAI#C, the UE cannot access Application#3 associated with VPLMN#1 S-NSSAI#3 in VPLMN#1 (there is a mapping relationship 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 identification information of the visited network, for example, VPLMN#1 S-NSSAI#1 and VPLMN#1 S-NSSAI#2. For example, in this example, the information content included in the URSP may be as shown in Table 4-1. Application#1 and Application#2 are deployed in the VPLMN, Application#A is deployed in the HPLMN, and the network slice identification information associated with Application#A is HPLMN S-NSSAI#B.

[0312] Example N: 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 information regarding the network slice to which the UE subscribes is 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 identification information 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 identification information of the visited network is a subset of the first network slice identification information of the visited network. After determining the second network slice identification information of the visited network, the H-PCF searches for UE policy support information (VPLMN assistant UE policy information) corresponding to the visited location. The generated URSP needs to include not only the information regarding the applications deployed in the HPLMN as shown in Table 4-0, but also the information regarding the applications deployed in the VPLMN, for example, 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 the second network slice identification information 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 content included in the URSP may be as shown in Table 4-2.Application#1, Application#2, and Application#3 are deployed in the VPLMN, Application#A is deployed in the HPLMN, and the network slice identification information associated with Application#A is HPLMN S-NSSAI#B.

[0313] Example Q: The second information includes 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. The information about the network slice to which the UE subscribes is HPLMN S-NSSAI#B. In this case, the H-PCF may determine that the second network slice identification information of the visited network is VPLMN#1 S-NSSAI#2. After determining the second network slice identification information of the visited network, the H-PCF searches for the UE policy support information (VPLMN assistant UE policy information) corresponding to the visited location. The generated URSP should not only include the information about the application deployed in the HPLMN in Table 4-0, but may also further include the information about the application deployed in the VPLMN, for example, 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 the 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 in the VPLMN, Application#A is deployed in the HPLMN, and the network slice identification information associated with Application#A is HPLMN S-NSSAI#B.

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

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

[0316] The second response message may be a user policy control creation response message (Npcf_UEPolicyControl Create Response), and the second response message includes the URSP generated by the H-PCF. For example, the URSP generated by the H-PCF may be any one of Table 4-1, Table 4-2, and Table 4-3.

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

[0318] The first response message may be a user policy control creation response message (Npcf_UEPolicyControl Create Response), and the first response message includes the URSP generated by the H-PCF.

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

[0320] According to the technical solution of this application, the mapping relationship between the visited 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 visited network.

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

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

[0323] The updated identification information of the network slice to which the UE subscribes may 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.

[0324] For example, in the above example M, 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.

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

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

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

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

[0329] Example X: The second information includes 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. When the updated identification information of the network slice to which the UE subscribes 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 searches for UE policy support information (VPLMN assistant UE policy information) corresponding to the visited location, and the generated URSP should not only include information regarding the applications deployed in the HPLMN in Table 4-0, but may also further include information regarding the applications deployed in the VPLMN, for example, 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-NSSAIs, for example, HPLMN S-NSSAI#A, HPLMN S-NSSAI#B, and HPLMN S-NSSAI#C. Optionally, the generated URSP may further include the second network slice identification information 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 content included in the URSP may be as shown in Table 4-2. Application#1, Application#2, and Application#3 are deployed in the VPLMN, Application#A is deployed in the HPLMN, and the network slice identification information associated with Application#A is HPLMN S-NSSAI#B.

[0330] Example Y: The second information includes 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. When the updated identification information of the network slice to which the UE subscribes is updated from HPLMN S-NSSAI#A and HPLMN S-NSSAI#B shown in the above Example M to HPLMN S-NSSAI#B shown in the above Example Q, the H-PCF searches for UE policy support information corresponding to the visited location (VPLMN assistant UE policy information). The generated URSP needs to include not only information regarding the application deployed in the HPLMN in Table 4-0, but may also further include information regarding the application deployed in the VPLMN, for example, Application#2 associated with VPLMN#1 S-NSSAI#2. The generated URSP includes an HPLMN S-NSSAI, for example, HPLMN S-NSSAI#B. Optionally, the generated URSP may further include the 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 in the VPLMN, Application#A is deployed in the HPLMN, and the network slice identification information associated with Application#A is HPLMN S-NSSAI#B.

[0331] It should be understood that the above Examples X and Y are merely intended to illustrate the technical solutions of this application and should not be used as limitations to the technical solutions of this application. It can 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 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 drawings, after generating a new URSP, the H-PCF may send the new URSP to the V-PCF by using a user policy control update notification request message (Npcf_UEPolicyControl UpdateNotify Request), and the V-PCF may further send the new URSP to the V-AMF by using a user policy control update notification request message (Npcf_UEPolicyControl UpdateNotify Request). It should be understood that the V-AMF sends the URSP to the UE so that the UE can access the services of the visited network. For example, the V-AMF sends the URSP to the UE by using a UE configuration update procedure.

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

[0334] The embodiment of this application further provides another implementation manner of the communication system in FIG. 1. In this implementation manner, 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 execute any communication method in the embodiments shown in FIGS. 9 to 13 of this application.

[0335] 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 first network element 110 updates the first service parameter to the second service parameter and is configured to send the second service parameter to the second network element 120. 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 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.

[0337] Optionally, the third network element 130 is configured to send 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 parameter to the first network element 110.

[0339] For the specific interaction process between network elements, refer to the following descriptions in FIGS. 9 to 13. Details are not described here.

[0340] For example, according to the communication system provided in this application, a mapping relationship between the visited 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 user routing selection policy for the terminal device so that the terminal device can normally access the services of the visited network.

[0341] In this implementation method, the system 100 shown in FIG. 1 may be applied to the 5th generation (5G) network architecture shown in FIG. 2 or FIG. 3. Obviously, it may also be applied to future network architectures, for example, the 6th generation (6G) network architecture. This is not particularly limited in the embodiments of this application. For example, when the communication system shown in FIG. 1 is applied to the 5G network shown in FIG. 2 or FIG. 3, the first network element 110 may be a Policy Control Network Element in the visited network (V-PCF), the second network element 120 may be a Policy Control Network Element in the home network (H-PCF), the third network element 130 may be a Mobility Management Network Element in the visited network (V-AMF), and the fourth network element 140 may be a Mobility Management Network Element in the visited network (V-UDR).

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

[0343] S910: The visited Policy Control Network Element updates the first service parameter to the second service parameter based on the mapping relationship. 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.

[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 method, the visited Policy Control Network Element may receive the mapping relationship from the visited Mobility Management Network Element.

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

[0347] Optionally, the mapping relationship includes a mapping relationship determined by the visited location of the terminal device between the configured network slice identification information and the home network slice identification information, 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.

[0348] In other possible implementation manners, the visited policy control network element obtains the mapping relationship from the local configuration.

[0349] Optionally, the visited policy control network element receives, from the visited mobility management network element, identification information of the network slice to which the terminal device belongs. The visited policy control network element updating the first service parameter to the second service parameter based on the mapping relationship includes the following. The visited 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 belongs.

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

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

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

[0353] Optionally, the visited policy control network element receives the user root selection policy from the home policy control network element, and the visited policy control network element sends the user root selection policy to the visited mobility management network element, and the user root selection policy will be used by the terminal device to access the services of the visited network.

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

[0355] FIG. 10 is a schematic flowchart of a fourth specific example of the communication method according to this application. For the sake of easy explanation, in the embodiments shown in FIGS. 10 to 13, the visited policy control network element is abbreviated as V-PCF, the visited mobility management network element is abbreviated as V-AMF, the visited 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, the network slice identification information may be replaced equivalently with the network slice from the perspective of expression, URSP is used as an example of the user root selection policy, and the user root selection policy includes but is not limited to URSP. Both the visited location and the home location are related to the UE. The visited location is the visited network of the UE, and the home location is the home network of the UE.

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

[0357] In this embodiment, the V-AMF may store a network slice roaming agreement including a slice mapping relationship between the HPLMN and the VPLMN. In the implementation manner, the network slice roaming agreement may be pre-configured in the V-AMF. For example, the mapping relationship regarding the network slice identification information between the HPLMN and the VPLMN may be as shown in Table 8.

Table 8

[0358] From Table 8, it can be seen that there are different mapping relationships between different visited 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: The UE roams and registers with the visited network.

[0360] Regarding the registration of the UE with the visited network, refer to the prior art. Details are not described here. For example, the visited network is VPLMN#1.

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

[0362] Specifically, the first request message may be a user policy control creation request message (Npcf_UEPolicyControl Create Request) and is used to request the V-PCF to create a UE policy association. Both the V-AMF and the V-PCF are located in the visited network VPLMN#1. The first request message includes a permanent subscription identifier of the UE, for example, a subscription permanent identifier (SUPI).

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

[0364] Optionally, the V-PCF may determine whether to execute step 1004 based on the visited network configuration information or identification information of the UE's home network.

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

[0366] The first service parameter may be carried by a visited location specific service parameter (VPLMN specific service parameter) or be the said service parameter. The VPLMN specific service parameter may include a DNN, SSC mode, and network slice information associated with an 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 content included in the VPLMN-specific service parameters may be as shown in Table 9. Application#1, Application#2, and Application#3 are deployed in 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: The V-PCF sends a second request message to the H-PCF.

[0369] The second request message may be a user policy control creation request message (Npcf_UEPolicyControl Create Request), and the second request message is used to request the creation of a UE policy association. The V-PCF determines the UE's HPLMN ID based on the subscription persistent identifier included in the first request message, and determines the identifier of the H-PCF based on the HPLMN ID. Further, the second request message may further include the identifier of the V-PCF (V-PCF ID).

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

[0371] S1006: The H-PCF generates the UE's URSP.

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

Table 10

[0373] From Table 10, it can be seen that in this case, the URSP is generated by the H-PCF based only on the home network slice identification information HPLMN S-NSSAI, for example, HPLMN S-NSSAI#B. For ease of distinction, the URSP may be referred to as the first URSP.

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

[0375] The second response message may be a user policy control creation response message (Npcf_UEPolicyControl Create Response message), and the second response message includes the first URSP generated by the H-PCF.

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

[0377] Specifically, the first response message may be a user policy control creation response message (Npcf_UEPolicyControl Create Response message), and the first response message includes the first URSP generated by the H-PCF.

[0378] The first response message further includes first information used to obtain the mapping relationship. 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 information may be policy control creation request trigger information (PolicyControl Request Trigger) sent to the V-AMF for instructing the V-AMF to send a user policy control update request message (Npcf_UEPolicyControl Update Request) to the V-PCF when a pre-set condition is met. The request message needs to include the mapping relationship. When the pre-set condition is met, it is not limited in this application. For example, in that case, it may be when the mapping relationship exists or when the mapping relationship is updated.

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

[0380] This step is optional. The V-AMF sends the first URSP to the UE so that the UE can access the services of the visited network. However, the first URSP is generated only based on the home network slice identification information HPLMN S-NSSAI, and the visited network slice identification information VPLMN S-NSSAI is not considered. Therefore, the first URSP may not be able to enable the UE to access the services of the visited network.

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

[0382] It should be understood that this step further includes the following. The V-AMF obtains the identification information of the network slice to which the UE subscribes, and determines the mapping relationship based on the identification information of the network slice to which the UE subscribes 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.

[0383] For example, the V-AMF obtains the network slice to which the UE subscribes, and determines the Configured Network Slice Identification (Configured NSSAI) and / or the mapping of the Configured NSSAI based on the network slice to which the UE subscribes and the roaming agreement. The network slice identification information included in the Configured NSSAI is the network slice identification information of the visited network. The mapping of the Configured NSSAI means that the Configured NSSAI includes the network slice identification information of the visited network and the network slice identification information 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 subscribes. The V-AMF may determine the mapping relationship based on the Configured NSSAI and / or the mapping of the Configured NSSAI. For example, the mapping relationship includes the Configured NSSAI and the mapping of the Configured NSSAI, or the mapping relationship includes the mapping of the Configured NSSAI.

[0384] Optionally, in other implementation manners, when the 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, the V-AMF may obtain the mapping relationship by requesting the V-NSSF. For example, the V-AMF sends the identification information of the network slice to which the UE belongs to the V-NSSF, and the V-NSSF determines the mapping relationship and returns the mapping relationship to the V-AMF.

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

[0386] Specifically, the V-AMF determines that the pre-set conditions are met and sends a third request message to send the mapping relationship to the V-PCF. The third request message may be a user policy control creation update message (Npcf_UEPolicyControl UpdateRequest) and is used to request the V-PCF to change the UE policy association (UE Policy Association Modification).

[0387] For example, the mapping relationship may be as shown in Table 11.

[0388]

Table 11

[0389] S1011: The 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, when the network slice identification information included in the first service parameter (VPLMN specific service parameter) is VPLMN#1 S-NSSAI#1, VPLMN#1 S-NSSAI#2, and VPLMN#1 S-NSSAI#3 (as shown in Table 9), and the mapping relationship is such that (as shown in Table 11) 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, the V-PCF may determine 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 based on the mapping relationship. 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. It can be understood that the network slice identification information included in the second service parameter is HPLMN S-NSSAI and belongs to the identification information of the network slice to which the UE subscribes.

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

[0393] The fourth request message may be a user policy control creation update request message (Npcf_UEPolicyControl Update Request), and the fourth request message is used to request the update of the UE policy association (UE Policy Association Modification).

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

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

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

[0397] For example, the content included in the second URSP may be as shown in Table 12.

Table 12

[0398] Application#1 and Application#2 are deployed in the VPLMN, and Application#A is deployed in the HPLMN.

[0399] From Table 12, it can be seen that the second URSP includes the HPLMN S-NSSAI having a mapping relationship with the VPLMN S-NSSAI. Optionally, the second URSP may further include the VPLMN S-NSSAI. In this way, the UE may directly determine the HPLMN S-NSSAI and the VPLMN S-NSSAI according to the URSP.

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

[0401] Specifically, the fourth response message may be a User Policy Control Create Response message, and the fourth response message includes the URSP updated by the H-PCF, that is, the second URSP.

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

[0403] Specifically, the third response message may be a user policy control creation update response message (Npcf_UEPolicyControl Update Response), and the third response message includes the URSP updated by the H-PCF, that is, the second URSP.

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

[0405] The updated URSP of the UE may be the second URSP shown in Table 12 and will be used by the UE to access the visited service.

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

[0407] FIG. 11 is a schematic flowchart of a fifth specific example of the communication method according to this application. Compared with the embodiment described in FIG. 10, in this embodiment, the V-AMF sends a user policy control creation request message (Npcf_UEPolicyControl Create Request) and actively includes the mapping relationship in the request message.

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

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

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

[0411] Specifically, the V-AMF determines that the mapping relationship needs to be sent to the V-PCF based on the UE's HPLMN ID. For example, refer to Table 11 for the content included in the mapping relationship. Details will not be elaborated here again.

[0412] S1104: The V-AMF sends a first request message to the V-PCF, and the first request message contains the mapping relationship.

[0413] Specifically, the V-AMF sends the mapping relationship to the V-PCF by sending the first request message. The first request message may be a user policy control creation request message (Npcf_UEPolicyControl Create Request) and is used to request the V-PCF to create a UE policy association.

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

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

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

[0417] The second request message may be a user policy control creation request message (Npcf_UEPolicyControl Create Request), and the second request message is used to request to create a UE policy association.

[0418] It should be noted that the second request message contains the second service parameters.

[0419] S1108: The 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 the second service parameters received from the V-PCF. For ease of distinction, the URSP may be referred to as the third URSP. For example, the content included in the UE context policy control data may be as shown in Table 10, the content included in the third URSP may be the same as the content of the second URSP in FIG. 10, and the content of the third URSP may be as shown in Table 12.

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

[0422] Specifically, the second response message may be a user policy control creation response message (Npcf_UEPolicyControl Create Response message), and the second response message includes the third URSP generated by the H-PCF.

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

[0424] Specifically, the first response message may be a user policy control creation response message (Npcf_UEPolicyControl Create Response message), and the first response message includes the third URSP generated by the H-PCF.

[0425] Optionally, after receiving the third URSP, the V-AMF may send the third URSP to the UE, so that the UE can access the destination service.

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

[0427] Specifically, when the subscription data of the UE is updated at a certain point in time, the V-AMF generates a new mapping relationship based on the latest subscription data of the UE and the roaming agreement. For example, the 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 latest subscription data of the UE 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, the V-AMF updates the locally stored mapping relationship, for example, updates the locally stored Configured NSSAI and / or the mapping of the Configured NSSAI.

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

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

[0431] S1113: The V-PCF, H-PCF, and V-AMF execute the URSP update procedure for the UE.

[0432] Specifically, the V-PCF updates 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 URSP of the UE to the V-PCF. The V-PCF sends the updated URSP of the UE to the V-AMF. For the specific process, refer to the above description and details will not be elaborated here again.

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

[0434] Figure 12 is a schematic flowchart of the sixth specific example of the communication method according to this application. Compared with 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 (Subscribe NSSAI) of the network slice to which the UE subscribes from the V-AMF.

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

[0436] For the specific steps and content of the V-PCF storing the network slice roaming agreement, refer to the description in S1001 where the V-AMF stores the network slice roaming agreement. Details will not be elaborated here again.

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

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

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

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

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

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

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

[0444] Specifically, the first response message may be a user policy control creation 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 identification information of the network slice (Subscribed NSSAI) to which the UE subscribes. The second information may be policy control request trigger information (PolicyControl Request Trigger), and may instruct V-AMF to send a user policy control update request message (Npcf_UEPolicyControl Update Request) to V-PCF when a preset condition is met. The request message needs to include the identification information of the network slice (Subscribed NSSAI) to which the UE subscribes. When the preset condition is met, it is not limited in this application. For example, in that case, it may be when the identification information of the network slice to which the UE subscribes exists or when the identification information of the network slice to which the UE subscribes is updated.

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

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

[0448] Specifically, after obtaining the identification information of the network slice to which the UE belongs and determining that the preset conditions are met, V-AMF sends a third request message to send the identification information of the network slice to which the UE belongs to V-PCF. The third request message may be a user policy control creation update request message (Npcf_UEPolicyControl UpdateRequest) and is used to request V-PCF to change the UE policy association (UE Policy Association Modification).

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

[0450] Specifically, V-PCF needs to determine the mapping relationship based on the identification information of the network slice to which the UE belongs 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, when the network slice identification information included in the first service parameter (VPLMN specific service parameter) is VPLMN#1 S-NSSAI#1, VPLMN#1 S-NSSAI#2, and VPLMN#1 S-NSSAI#3 (as shown in Table 9), and the mapping relationship is 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 (as shown in Table 11), the V-PCF may determine 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 based on the mapping relationship. 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. It can be understood that the network slice identification information included in the second service parameter is HPLMN S-NSSAI and belongs to the network slice to which the UE subscribes.

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

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

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

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

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

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

[0458] FIG. 12 is a schematic flowchart of a seventh specific example of the communication method according to this application. Compared with the embodiment in FIG. 12, in this embodiment, the V-PCF no longer sends the PolicyControl Request Trigger to the V-AMF, and the V-AMF actively sends a user policy control creation request message (Npcf_UEPolicyControl Create Request). The request message includes the identification information of the network slice to which the UE subscribes.

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

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

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

[0462] Specifically, the 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 the V-PCF.

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

[0464] Specifically, the V-AMF sends the identification information of the network slice to which the UE belongs to the V-PCF by sending a first request message. The first request message may be a user policy control creation request message (Npcf_UEPolicyControl Create Request), and is used to request the V-PCF to create a UE policy association.

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

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

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

[0468] The second request message may be a user policy control creation request message (Npcf_UEPolicyControl Create Request), and the second request message is used to request to create a UE policy association.

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

[0470] S1308: The H-PCF generates the UE's URSP.

[0471] Specifically, the H-PCF generates a URSP based on the UE context policy control data obtained from the H-UDR and the second service parameters received from the V-PCF. For ease of distinction, the URSP may be referred to as the third URSP. For example, the content included in the UE context policy control data may be as shown in Table 10, the content included in the third URSP may be the same as the content of the second URSP in FIG. 10, and the content of the third URSP may be as shown in Table 12.

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

[0473] Specifically, the second response message may be a user policy control creation response message (Npcf_UEPolicyControl Create Response message), and the second response message includes the third URSP generated by the H-PCF.

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

[0475] Specifically, the first response message may be a user policy control creation response message (Npcf_UEPolicyControl Create Response message), and the first response message includes the third URSP generated by the H-PCF.

[0476] Optionally, after receiving the third URSP, the V-AMF may send the third URSP to the UE, so that the UE can access the visited service.

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

[0478] Specifically, when the subscription data of the UE is updated at a certain point in time, the V-AMF determines the updated identification information of the network slice to which the UE subscribes based on the latest subscription data of the UE.

[0479] S1312: The V-AMF sends a third request message to the V-PCF, and the third request message includes the updated identification information of the network slice to which the UE subscribes.

[0480] Specifically, by sending the third request message, the V-AMF sends the updated identification information of the network slice to which the UE subscribes to the V-PCF. The third request message may be a user policy control update request message (Npcf_UEPolicyControl Update Request) and is used to request the V-PCF to change the UE policy association (UE Policy Association Modification).

[0481] S1313: The V-PCF, H-PCF, and V-AMF execute the URSP update procedure for the UE.

[0482] Specifically, the V-PCF determines a new mapping relationship based on the updated identification information of the network slice to which the UE subscribes, 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 URSP of the UE based on the updated service parameters and sends the updated URSP of the UE to the V-PCF. The V-PCF sends the updated URSP of the UE to the V-AMF. For the specific process, refer to the above description and details are not repeated here.

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

[0484] This application further provides a communication system. The communication system includes a visited policy control network element and a home policy control network element. The visited 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 visited network and the second network slice identification information of the home network, and send the second service parameter to the home policy control network element. 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 home policy control network element is configured to determine a universal routing selection policy for the terminal device based on the second service parameter, and the universal routing selection policy will be used by the terminal device to access the visited service.

[0485] Optionally, the communication system further includes a visited mobility management network element. The visited mobility management network element is configured to send the mapping relationship to the visited policy control network element, or send the identification information of the network slice to which the terminal device belongs to the visited policy control network element.

[0486] For example, according to the communication system provided in this application, a mapping relationship between the visited network slice identification information of a terminal device and the home network slice identification information of the terminal device can be obtained. This helps to generate a universal routing selection policy for the terminal device so that the terminal device can normally access the services of the visited network.

[0487] It should be understood that the sequence numbers of the above processes do not mean the order of execution. The order of execution of the processes should be determined according to the functions and internal logics of the processes, and should not constitute any limitation to the implementation process of the embodiments of this application.

[0488] In the embodiments of this application, unless otherwise specified, or unless there is no logical contradiction, the terms and / or descriptions between different embodiments are consistent and may be referred to each other. It should be further understood that the technical features in different embodiments may be combined into new embodiments based on their internal logical relationships.

[0489] It can be understood that in the above embodiments of this application, the method implemented by the communication device may alternatively be implemented by components (such as chips or circuits) configured in the communication device.

[0490] It should be noted that the above uses the example where the "terminal device" in this application is a UE to explain the method. In actual applications, the UE may also be replaced by other terminal devices. This is not limited in this application. Optionally, the UE may access the visited service by creating a session. The "session" may be a PDU session or other sessions. This is not limited in this application.

[0491] The communication method provided in the embodiments of this application is described in detail above with reference to FIGS. 5 to 13. The above communication method is mainly described from the perspective of the interaction between network elements. To implement the above functions, it can be understood that each network element includes a corresponding hardware structure and / or software module for executing the functions. Those skilled in the art should recognize that this application can be implemented in the form of hardware or a combination of hardware and computer software with reference to the exemplary units and algorithm steps described in the embodiments disclosed in this specification. Whether the function is executed 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 implement the described functions for each specific application, but the implementation method should not be considered to exceed the scope of this application.

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

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

[0494] FIG. 14 is a schematic block diagram of an example of a communication device 1400 according to this application. Any one of the network elements 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 FIG. 14.

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

[0496] As shown in FIG. 14, the communication device 1400 includes one or more processors 1410. The processor 1410 may store execution instructions for executing the methods in the embodiments of this application. Optionally, the processor 1410 may call an interface for realizing reception and transmission functions. The interface may be a logical interface or a physical interface. This is not limited. For example, the interface may be a transceiver circuit or an interface circuit. The transceiver circuit or the interface circuit configured to realize reception and transmission functions may be separated or integrated. The transceiver circuit or the interface circuit may be configured to read and write code / data, or the transceiver circuit or the interface circuit may be configured to transmit or transfer signals.

[0497] Optionally, the interface may be realized through a transceiver. Optionally, the communication device 1400 may further include a transceiver 1430. The transceiver 1430 may be referred to as a transceiver unit, a transceiver machine, a transceiver circuit, a transceiver, etc., and is configured to realize reception and transmission functions.

[0498] Optionally, the communication device 1400 may further include a memory 1420. The specific arrangement location of the memory 1420 is not particularly limited in this embodiment of this application. The memory may be integrated with the processor or may be independent of the processor. When the communication device 1400 does not include a memory, the communication device 1400 only needs to have a processing function, and the memory may be arranged at other locations (for example, a cloud system).

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

[0500] Although not shown, 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, the memory 1420 may store execution instructions for executing the methods in the embodiments of this application. The processor 1410 executes the instructions stored in the memory 1420 and may complete the steps executed in the following manner in combination with other hardware (for example, the transceiver 1430). For specific operation processes and beneficial effects, refer to the descriptions in the method embodiments above.

[0502] The method disclosed in the embodiments of this application may be applied to processor 1410 or may be implemented by processor 1410. Processor 1410 may be an integrated circuit chip and has signal processing capabilities. In the implementation process, the steps of the method may be completed by using integrated logic circuits of hardware in the processor or instructions in the form of software. The above-mentioned 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 devices, discrete gates or transistor logic devices, or discrete hardware components. The processor may implement or execute the methods, steps and logic block diagrams disclosed in the embodiments of this application. The general-purpose processor may be a microprocessor, or the processor may be any conventional processor or the like. The steps of the method disclosed with reference to the embodiments of this application may be directly executed by a hardware decoding processor, or may be executed by a combination of a hardware module and a software module in the decoding processor. The software module may be located in a mature storage medium in the art, such as a random access memory (RAM), a flash memory, a read-only memory (ROM), a programmable read-only memory, an electrically erasable programmable memory or a register. The storage medium is located in the memory, and the processor reads the instructions in the memory and combines them with the hardware of the processor to complete the steps of the above method.

[0503] Memory 1420 may be volatile memory, non-volatile memory, or may include both volatile memory and non-volatile memory. It can be understood that non-volatile memory may be read-only memory (ROM), programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), or flash memory. Volatile memory may be random access memory (RAM) used as an external cache. By way of example and not limitation, many forms of RAM are available, such as static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), double data rate SDRAM (DDR SDRAM), enhanced SDRAM (ESDRAM), synchlink DRAM (SLDRAM), and 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 any of these memories and other suitable types of memory, but is not limited thereto.

[0504] FIG. 15 is a schematic block diagram of a 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 in this embodiment of this application. As shown in FIG. 15, the communication device includes a processing unit 1510 and a transceiver unit 1520.

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

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

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

[0509] Optionally, when the communication device 1500 belongs to the home network, the transceiver unit 1520 is further configured to receive third information, which includes the first network slice identification information of the visited network. The processing unit 1510 is configured to determine the user root selection policy URSP of the terminal device based on the second information and the third information, and the URSP will be used by the terminal device to access the services of 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 fourth information, which indicates the updated identification information of the network slice to which the terminal device belongs. The transceiver unit 1520 is further configured to transmit fifth information, which is used to request the 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 belongs.

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

[0512] Optionally, the transceiver unit 1520 is further configured to receive fourth information, the fourth information including updated identification information of a network slice to which the terminal device subscribes, and is further configured to transmit fifth information, the fifth information being 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, the third network slice identification information of the visited network being a subset of 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.

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

[0514] Optionally, the transceiver unit 1520 is further configured to receive a mapping relationship from a visited mobility management network element.

[0515] Optionally, the transceiver unit 1520 is further configured to transmit a message for obtaining the mapping relationship to a visited mobility management network element.

[0516] Optionally, the transceiver unit 1520 is further configured to obtain a mapping relationship from a local configuration.

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

[0518] Optionally, the transceiver unit 1520 is further configured to send a message for obtaining identification information of a network slice to which the terminal device subscribes to a visited mobility management network element.

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

[0520] Optionally, the transceiver unit 1520 receives a user root selection policy from a home policy control network element and sends the user root selection policy to a visited mobility management network element, and the user root selection policy is to be used by the terminal device to access services of the visited network.

[0521] When the communication device 1500 is a policy control device, the transceiver unit 1520 in the communication device 1500 may be implemented by using a communication interface (for example, a transceiver or an input / output interface), and the processing unit 1510 in the communication device 1500 may be implemented by using at least one processor, for example, corresponding to the processor 1410 shown in FIG. 14. It should be understood that this is also possible.

[0522] Optionally, the communication device 1500 may further include a memory unit. The memory unit may be configured to store instructions or data. The processing unit may call the instructions or data stored in the memory unit to implement corresponding operations.

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

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

[0525] For example, the transceiver unit 1520 is configured to receive first information, where the first information includes 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 processing unit 1510 is configured to determine second information based on the first information. The transceiver unit 1520 is further configured to transmit the second information, where the second information includes the mapping relationship between the second network slice identification information of the visited 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 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. 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 fifth information, where the fifth information indicates 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, where 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. 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.

[0527] When the communication device 1500 is a network slice selection network element or an access management network element, the transceiver unit 1520 in the communication device 1500 may be implemented by using a communication interface (for example, a transceiver or an input / output interface), for example, corresponding to the communication interface 1430 shown in FIG. 14. The processing unit 1510 in the communication device 1500 may be implemented by using at least one processor, for example, corresponding to the processor 1410 shown in FIG. 14. It should be understood that this is the case.

[0528] Optionally, the communication device 1500 may further include a storage unit. The storage unit may be configured to store instructions or data. The processing unit may call the instructions or data stored in the storage unit to implement corresponding operations.

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

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

[0531] Furthermore, in this application, the communication device 1500 is presented in the form of functional modules. Here, the "module" may be an application-specific integrated circuit ASIC, a circuit, a processor that executes one or more software or firmware programs, and a memory, an integrated logic circuit, and / or other components that can provide the above functions. In a simple embodiment, those skilled in the art can understand that the device 1500 may also be in the form shown in FIG. 15. The processing unit 1510 may be realized by using the processor 1410 shown in FIG. 14. Optionally, when the computer device shown in FIG. 14 includes the memory 1420, the processing unit 1510 may be realized by using the processor 1410 and the memory 1420. The transceiver unit 1520 may be realized by using the transceiver 1430 shown in FIG. 14. The transceiver 1430 has a receiving function and a transmitting function. Specifically, the processor is realized by executing a computer program stored in the memory. Optionally, when the device 1500 is a chip, the function and / or realization process of the transceiver unit 1520 may be alternatively realized by using pins, circuits, etc. Optionally, the memory may be a storage unit on the chip such as a register or a cache. The storage unit may be a storage unit within the computer device and located outside the chip, for example, the memory 1420 shown in FIG. 14, or a storage unit arranged in another system or device but not located in the computer device. Those skilled in the art can recognize that, in combination with the examples described in the embodiments disclosed in this specification, the units and algorithm steps may be realized by electronic hardware, or a combination of computer software and electronic hardware. Whether the function is realized by hardware or by 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 realization method should not be considered to exceed the scope of this application.

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

[0533] According to the method provided in an embodiment of this application, this application further provides a computer program product. The computer program product includes computer program code. When the computer program code is executed on a computer, the computer is capable of executing the method in any of the embodiments shown in FIGS. 5 and 13.

[0534] According to the method provided in an embodiment of this application, this application further provides a computer-readable medium. The computer-readable medium stores program code. When the program code is executed on a computer, the computer is capable of executing the method in any of the embodiments shown in FIGS. 5 and 8.

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

[0536] All or part of the above embodiments may be implemented by software, hardware, firmware, or any combination thereof. When software is used to implement the embodiments, all or part of the embodiments may be implemented in the form of a computer program product. The computer program product includes one or more computer instructions. When the computer instructions are loaded and executed on a computer, the procedures or functions according to the embodiments of this application are all or partially generated. The computer may be a general-purpose computer, a dedicated computer, a computer network, or other programmable apparatuses. The computer instructions may be stored in a computer-readable storage medium, or transmitted from one computer-readable storage medium to another computer-readable storage medium. For example, the computer instructions may be transmitted in a wired (such as coaxial cable, optical fiber, or digital subscriber line (DSL)) or wireless (such as infrared, wireless, or microwave) manner from a website, computer, server, or data center to another website, computer, server, or data center. 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 integrating one or more available media. The available medium may be a magnetic medium (such as a floppy disk, hard disk, or magnetic tape), an optical medium (such as a digital video disc (DVD)), a semiconductor medium (such as a solid state drive (SSD)), etc.

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

[0538] It should also be understood that the term "and / or" in this specification is merely an association relationship of related objects, indicating that three relationships may exist. For example, A and / or B may indicate the following three cases, namely, only A exists, both A and B exist, and only B exists. Further, the character " / " in this specification usually indicates an "or" relationship between related objects.

[0539] Furthermore, it should be understood that numbers such as "first" and "second" are introduced in the embodiments of this application only for the purpose of distinguishing between different objects, for example, only for the purpose of distinguishing between different "information", "devices" or "units". The understanding of specific objects and the corresponding relationships between different objects should be determined based on the functions and internal logics of the objects, and should not constitute any limitation to the implementation process of the embodiments of this application.

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

[0541] For the sake of convenience and brevity of description, those skilled in the art can clearly understand by referring to the corresponding processes in the embodiments of the above method for the specific operation processes of the above system, device and unit. Details will not be described again here.

[0542] In some embodiments provided in this application, it should be understood that the disclosed systems, devices and methods may be implemented in other ways. For example, the embodiments of the described devices are merely examples. For example, the division into units is merely a logical function division. In actual implementation methods, other division methods may exist. For example, a plurality of units or components may be combined or integrated into other systems, or some features may be ignored or not executed. Furthermore, the couplings or direct couplings or communication connections shown or discussed may be realized through some interfaces, and the indirect couplings or communication connections between devices or units may be realized in electrical, mechanical or other forms.

[0543] The units described as separate parts may or may not be physically separate, and the parts shown as units may or may not be physical units. They may be located in one place or distributed among a plurality of network units. Some or all of the units may be selected according to actual requirements to achieve the purpose of the solution in the embodiments.

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

[0545] When the function is realized in the form of a software functional unit and sold or used as an independent product, the function may be stored in a computer-readable storage medium. Based on such an understanding, the technical solution of this application, in essence, or the part that contributes to the prior art or a part of the technical solution, may also be realized in the form of a software product. The computer software product is stored in a storage medium and contains several instructions for instructing a computer device (which may be a personal computer, a server, or a network device) to execute all or part of the steps of the method described in the embodiments of this application. The above storage medium includes any medium that can store program code, such as a USB flash drive, a removable hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk, or an optical disk. The above description is merely a specific implementation manner of this application. However, the protection scope of this application is not limited thereto. Any change or substitution that can be easily conceived by those skilled in the art within the technical scope disclosed in this application shall fall within the protection scope of this application. Therefore, the protection scope of this application shall follow the protection scope of the claims.

Claims

1. A communication method, comprising: updating a first service parameter to a second service parameter based on a mapping relationship between first network slice identification information of a visited network and second network slice identification information of a home network by a visited policy control network element, 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; and sending, by the visited policy control network element, the second service parameter to a home policy control network element, wherein the second service parameter is used to determine a user routing selection policy for a terminal device. The method as described above.

2. The method according to claim 1, further comprising receiving, by the visited policy control network element, the mapping relationship from a visited mobility management network element.

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

4. The mapping relationship includes a mapping relationship determined by the visited network for the terminal device between configured network slice identification information and home network slice identification information, 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. The method according to any one of claims 1 to 3.

5. The method according to claim 1, further comprising obtaining, by the visited policy control network element, the mapping relationship from a local configuration.

6. The method according to claim 1, further comprising receiving, by the visited policy control network element, identification information of a network slice to which the terminal device subscribes from a visited mobility management network element. A step of updating a first service parameter to a second service parameter based on a mapping relationship between first network slice identification information of a visited network and second network slice identification information of a home network by a visited policy control network element is The method according to claim 5, further comprising a step of updating the first service parameter to the second service parameter by the visited policy control network element based on the mapping relationship and the identification information of the network slice to which the terminal device belongs.

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

8. The method according to any one of claims 1 to 7, further comprising a step of the visited policy control network element obtaining the first service parameter from a visited unified data repository network element.

9. A step of the visited policy control network element receiving the user route selection policy from the home policy control network element; and A step of the visited policy control network element sending the user route selection policy to the visited mobility management network element, wherein the user route selection policy is to be used by the terminal device to access services of the visited network. The method according to any one of claims 1 to 8, further comprising the above steps.

10. A communication system including a visited policy control network element and a visited mobility management network element, The visited mobility management network element is configured to send a mapping relationship between first network slice identification information of a visited network and second network slice identification information of a home network to the visited policy control network element. The visited policy control network element is configured to update a first service parameter to a second service parameter based on the mapping relationship and send the second service parameter to a home policy control network element. 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.

11. The system further includes the home policy control network element, 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 will be used by the terminal device to access a visited service. The system according to claim 10.

12. The visited mobility management network element is further configured to receive a message for obtaining the mapping relationship from the visited policy control network element. The system according to claim 11.

13. The mapping relationship includes a mapping relationship determined by the visited network for the terminal device between the configured network slice identification information and the home network slice identification information. 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. The system according to any one of claims 10 to 12.

14. The visited policy control network element is further configured to obtain the mapping relationship from a local configuration. The system according to claim 10.

15. The visited mobility management network element is further configured to send identification information of a network slice to which the terminal device belongs to the visited policy control network element. The access 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 access destination network and the second network slice identification information of the home network. The system according to claim 14, specifically including 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 belongs.

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

17. The system further includes an access destination unified data repository network element, and the access destination unified data repository network element is configured to transmit the first service parameter to the access destination policy control network element. The system according to any one of claims 10 to 16.

18. The home policy control network element is further configured to transmit the user route selection policy to the access destination policy control network element. The access destination policy control network element is further configured to transmit the user route selection policy to the access destination mobility management network element. The user route selection policy is to be used by the terminal device to access the service of the access destination network. The system according to any one of claims 11 to 17.

19. A communication device, including a processor configured to execute computer instructions stored in a memory so that the communication device executes the method according to any one of claims 1 to 9.

20. A computer-readable storage medium, A computer-readable storage medium stores a computer program, and when the computer program is executed by a communication device, the method according to any one of claims 1 to 9 is executed.

21. A chip system, including a processor configured to call a computer program or instructions from a memory and execute the computer program or the instructions so that a communication device in which the chip system is installed realizes the method according to any one of claims 1 to 9.

22. A communication method, including the steps of: transmitting, by a visited mobility management network element, a mapping relationship between first network slice identification information of a visited network and second network slice identification information of a home network to a visited policy control network element; updating, by the visited policy control network element, a first service parameter to a second service parameter based on the mapping relationship, where 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; and transmitting, by the visited policy control network element, the second service parameter to a home policy control network element.

23. The method according to claim 22, further including the step of determining, by the home policy control network element, a user route selection policy for a terminal device based on the second service parameter, where the user route selection policy is to be used by the terminal device to access a visited service.

24. The method according to claim 23, further including the step of receiving, by the visited mobility management network element, a message for obtaining the mapping relationship from the visited policy control network element.

25. ​ The method further includes a step of transmitting, by the visited mobility management network element, identification information of a network slice to which the terminal device subscribes to the visited policy control network element. The step of updating, by the visited policy control network element, the first service parameter to the second service parameter based on the mapping relationship is: The method according to claim 22, including a step of updating, by the visited policy control network element, 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 subscribes. **Claim 26** The method according to claim 25, further including a step of receiving, by the visited mobility management network element, a message for acquiring the identification information of the network slice to which the terminal device subscribes from the visited policy control network element. **Claim 27** The method according to any one of claims 22 to 26, further including a step of transmitting, by the visited unified data repository network element, the first service parameter to the visited policy control network element. **Claim 28** A step of transmitting, by the home policy control network element, a user route selection policy to the visited policy control network element; A step of transmitting, by the visited policy control network element, the user route selection policy to the visited mobility management network element, wherein the user route selection policy is to be used by the terminal device to access the services of the visited network. The method according to any one of claims 22 to 27, further including the above steps.

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