Communication method and apparatus

Abstract

The present application provides a communication method and apparatus. A terminal is homed to a second PLMN, and there is indirect network sharing between the second PLMN and a first PLMN. An access management network element in the first PLMN receives an identifier of a network slice in the second PLMN that the terminal requests to access; and the access management network element sends an identifier of a network slice in the first PLMN that allows access and a registration response to an access network device, wherein the registration response comprises the identifier of the network slice in the second PLMN that allows access. Since the identifier sent to the terminal is the identifier of the network slice in the second PLMN, the terminal remains unaware that it has accessed an access network device involved in network sharing, thereby reducing the impact of indirect network sharing on the terminal. By considering that the access network device is a device in the first PLMN, the identifier sent to the access network device is the identifier of the network slice in the first PLMN, thereby ensuring that the access network device can correctly identify which network slice is used to serve the terminal.

Description

A communication method and device thereof

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to the Chinese patent application filed with the State Intellectual Property Office of the People's Republic of China on March 21, 2024, with application number 202410340361.4 and application name “A communication method and device thereof”, the entire contents of which are incorporated by reference into this application. Technical Field

[0003] The present application relates to the field of communication technology, and in particular to a communication method and apparatus thereof. Background Art

[0004] Network sharing refers to the sharing of network infrastructure among multiple operators. The goal is to reduce network construction costs and lower network operating expenses. Sharing can encompass sites, base stations, transmission, radio network controllers (RNCs), core networks, or even the entire network. Network sharing frees up operators' resources to optimize network coverage, allowing them to focus more on user experience and provide more competitive service capabilities. It also reduces energy consumption and redundant site construction, meeting energy conservation and emission reduction requirements.

[0005] In an indirect network sharing scenario, operator 1 shares a base station managed by itself with operator 2. This base station is subsequently referred to as a shared base station. There is an intercommunication interface between the shared base station and operator 1's core network 1, but no intercommunication interface between the shared base station and operator 2's core network 2. In other words, the shared base station is managed only by operator 1; there is an intercommunication interface between core network 1 and core network 2, which can transmit data streams. In addition to broadcasting the network identifier of operator 1, the shared base station can also broadcast the equivalent network identifier of operator 2 (for example, an equivalent public land mobile network (PLMN), or referred to as a peer PLMN, or an equivalent PLMN, or an equivalent PLMN), so that terminal devices belonging to operator 2 can access the shared base station based on the equivalent network identifier of operator 2. After the terminal device belonging to operator 2 accesses the shared base station, all data streams transmitted between the terminal device and operator 2's core network 2 need to be transmitted through core network 1.

[0006] When network slicing is introduced in the scenario of indirect network sharing, if the terminal of operator 2 accesses the shared base station based on the equivalent PLMN of operator 2, then when the terminal registers and / or establishes a session, the network slice identifier sent to the network of operator 1 is the identifier of the network slice in operator 2. It is necessary to consider how to enable the terminal of operator 2 to normally access the network slice of operator 1 based on the network slice identifier sent by the terminal of operator 2. Summary of the Invention

[0007] An embodiment of the present application provides a communication method and apparatus thereof, which are used to enable a terminal belonging to a certain operator to normally access a network slice of another operator in a network slicing scenario.

[0008] In a first aspect, the present application provides a communication method, which can be executed by an access management network element, or by other devices including the functions of an access management network element, or by a chip system (which can also be replaced by a chip) or other functional modules. The chip system or functional module can realize the functions of the access management network element, and the chip system or functional module is, for example, set in the access management network element. Take the execution of the access management network element in the first PLMN as an example to introduce the method: the terminal device belongs to the second PLMN, and there is indirect network sharing between the second PLMN and the first PLMN. The access management network element in the first PLMN receives a first message from an access network device, the first message including: a registration request of a terminal device belonging to the second PLMN, the registration request including: an identifier of a network slice in the second PLMN that the terminal device requests to access; sends a second message to the access network device, the second message including: an identifier of the network slice in the first PLMN that the terminal device is allowed to access and a registration response for sending to the terminal device; the registration response including: an identifier of the network slice in the second PLMN that the terminal device is allowed to access; an identifier of the network slice in the first PLMN that the terminal device is allowed to access is used to send to the access network device.

[0009] In this embodiment, in the registration process of a terminal device belonging to the second PLMN, the terminal device sends an identifier of a network slice in the second PLMN to a network element in the first PLMN. Considering that the terminal device is a device belonging to the second PLMN, the identifier of the network slice allowed to be accessed and sent to the terminal device is the identifier of the network slice in the second PLMN. The terminal does not perceive the access network device that has access to the shared network, which can reduce the impact of indirect network sharing on the terminal. Considering that the access network device is a device in the first PLMN, the identifier of the network slice allowed to be accessed and sent to the access network device is the identifier of the network slice in the first PLMN. This can ensure that the access network device correctly identifies which network slice to use to serve the terminal.

[0010] In one possible implementation, the registration response also includes: an identifier of the network slice in the second PLMN configured for the terminal device, and the identifier of the network slice in the second PLMN configured for the terminal device is determined based on the identifier of the network slice in the second PLMN to which the terminal device is subscribed.

[0011] In one possible implementation, the access management network element may also save at least one of the following items in the context of the terminal device: a mapping relationship between the identifier of the network slice in the first PLMN that the terminal device is allowed to access and the identifier of the network slice in the second PLMN that the terminal device is allowed to access, and a mapping relationship between the identifier of the network slice in the first PLMN configured for the terminal device and the identifier of the network slice in the second PLMN configured for the terminal device.

[0012] In this implementation, the access management network element saves the mapping relationship between the identifiers of the network slices in the context of the terminal device so as to accurately provide services to the terminal device.

[0013] In a possible implementation, the first message further includes: an identifier of an equivalent PLMN of the second PLMN, and the access management network element may further determine, based on the identifier of the equivalent PLMN, that the terminal device is a terminal device accessed through indirect network sharing.

[0014] In a possible implementation, the access management network element may further determine, based on the existence of indirect network sharing between the second PLMN and the first PLMN, that the identifier of the network slice that the terminal device is allowed to access and sent to the terminal device is the identifier of the network slice in the second PLMN, and that the identifier of the network slice that the terminal device is allowed to access and sent to the access network device is the identifier of the network slice in the first PLMN. It may also be determined that the identifier of the network slice configured for the terminal device and sent to the terminal device is the identifier of the network slice in the second PLMN.

[0015] In a possible implementation, the access management network element may also determine one or more of the following; or the access management network element obtains one or more of the following from the network slice selection function network element in the first PLMN: the identifier of the network slice in the first PLMN that the terminal device is allowed to access, the identifier of the network slice in the second PLMN that the terminal device is allowed to access, the mapping relationship between the identifier of the network slice in the first PLMN that the terminal device is allowed to access and the identifier of the network slice in the second PLMN that the terminal device is allowed to access, the identifier of the network slice in the first PLMN configured for the terminal device, the identifier of the network slice in the second PLMN configured for the terminal device, the mapping relationship between the identifier of the network slice in the first PLMN configured for the terminal device and the identifier of the network slice in the second PLMN configured for the terminal device.

[0016] In one possible implementation, the one or more items are determined based on a mapping relationship between an identifier of a network slice in the second PLMN and an identifier of a network slice in the first PLMN.

[0017] In a possible implementation, the access management network element may also map the identifier of the network slice in the second PLMN that the terminal device requests to access to the identifier of the network slice in the first PLMN requested to access based on the mapping relationship between the identifier of the network slice in the second PLMN and the identifier of the network slice in the first PLMN; determine the identifier of the network slice in the first PLMN that the terminal device is allowed to access based on the identifier of the network slice in the first PLMN requested to access; and map the identifier of the network slice in the first PLMN that the terminal device is allowed to access to the identifier of the network slice in the second PLMN allowed to access by the terminal device based on the mapping relationship between the identifier of the network slice in the second PLMN and the identifier of the network slice in the first PLMN.

[0018] In this implementation, the identifier of the network slice requested for access in the second PLMN is mapped to the first PLMN, so that the access management network element in the first PLMN can know which network slices the terminal requests to access, and the access management network element can more accurately select the network slice allowed to be accessed for the terminal.

[0019] In a second aspect, the present application provides a communication method, which can be executed by an access management network element, or by other devices including access management network element functions, or by a chip system (which can also be replaced by a chip) or other functional modules, wherein the chip system or functional module can implement the functions of the access management network element, and the chip system or functional module is, for example, provided in the access management network element. This method is described using the execution of the access management network element in the first PLMN as an example: the terminal device belongs to the second PLMN, and indirect network sharing exists between the second PLMN and the first PLMN. An access management network element in a first PLMN receives a first message from a terminal device belonging to a second PLMN, where the first message is used to request establishment of a session, and the first message includes: an identifier of a first network slice in the second PLMN; the first network slice is associated with the session requested to be established; the access management network element may send a second message to a first session management network element in the first PLMN, where the second message includes: an identifier of the first network slice in the second PLMN and an identifier of the second network slice in the first PLMN, and there is a mapping relationship between the identifier of the first network slice and the identifier of the second network slice; the access management network element may also receive a third message from the first session management network element, where the third message includes: an identifier of the second network slice in the first PLMN; the access management network element may also send a fourth message to an access network device serving the terminal device, where the fourth message includes: an identifier of the second network slice in the first PLMN and a first session establishment response for sending to the terminal device.

[0020] In this embodiment, when a terminal device belonging to the second PLMN establishes a session based on a network element in the first PLMN, the terminal device sends an identifier of a network slice in the second PLMN to the network element in the first PLMN. Considering that the access network device is a device in the first PLMN, the network element in the first PLMN maps the identifier of the first network slice in the second PLMN from the terminal device to the identifier of the second network slice in the first PLMN and informs the access network device. This ensures that the access network device correctly identifies which network slice to use to serve the terminal.

[0021] In one possible implementation, the third message also includes: an identifier of the first network slice in the second PLMN; and the first session establishment response includes: an identifier of the first network slice in the second PLMN.

[0022] In this implementation, the identifier of the network slice in the second PLMN is fed back to the terminal device belonging to the second PLMN, and the terminal does not perceive the access network device connected to the network sharing, which can reduce the impact of indirect network sharing on the terminal.

[0023] In a possible implementation, the second message further includes: first indication information, where the first indication information is used to indicate that the terminal device is a terminal device accessed through indirect network sharing.

[0024] In a possible implementation, the first session management network element may also map the identifier of the first network slice in the second PLMN to the identifier of the second network slice in the first PLMN based on the mapping relationship between the identifier of the network slice in the second PLMN and the identifier of the network slice in the first PLMN.

[0025] In a possible implementation, the second message further includes: information about a second session management network element in the second PLMN, where the information about the second session management network element is used by the first session management network element to find the second session management network element.

[0026] In a third aspect, the present application provides a communication method, which can be executed by a session management network element, or by other devices including session management network element functions, or by a chip system (which can also be replaced by a chip) or other functional module. The chip system or functional module can implement the functions of the session management network element. The chip system or functional module is, for example, set in the session management network element. This method is described by taking the execution of the session management network element in the first PLMN as an example: the terminal device belongs to the second PLMN, and there is indirect network sharing between the second PLMN and the first PLMN. During the process of the terminal device belonging to the second PLMN requesting to establish a session, the first session management network element in the first PLMN receives a second message from the access management function network element in the first PLMN, the second message including: an identifier of a first network slice in the first PLMN and an identifier of a second network slice in the second PLMN, a mapping relationship between the identifier of the first network slice and the identifier of the second network slice; the first network slice is associated with the session requested to be established; and the first session management network element sends a third message to the access management function network element, the third message including: an identifier of the second network slice in the first PLMN for sending to the access network device and a first session establishment response for sending to the terminal device.

[0027] In this embodiment, when a terminal device belonging to the second PLMN establishes a session based on a network element in the first PLMN, the terminal device sends an identifier of a network slice in the second PLMN to the network element in the first PLMN. Considering that the access network device is a device in the first PLMN, the network element in the first PLMN maps the identifier of the first network slice in the second PLMN from the terminal device to the identifier of the second network slice in the first PLMN and informs the access network device. This ensures that the access network device correctly identifies which network slice to use to serve the terminal.

[0028] In one possible implementation, the first session establishment response includes: an identifier of the first network slice in the second PLMN.

[0029] In this implementation, the identifier of the network slice in the second PLMN is fed back to the terminal device belonging to the second PLMN, and the terminal does not perceive the access network device connected to the network sharing, which can reduce the impact of indirect network sharing on the terminal.

[0030] In a possible implementation, the second message further includes: first indication information, where the first indication information is used to indicate that the terminal device is a terminal device accessed through indirect network sharing.

[0031] In a possible implementation, the first session management network element may also determine, based on the first indication information: to send the identifier of the network slice in the second PLMN to the terminal device, and to send the identifier of the network slice in the first PLMN to the access network device.

[0032] In a possible implementation, the first session management network element may also send a fifth message to the second session management network element in the second PLMN, where the fifth message includes: an identifier of the first network slice in the second PLMN; the first session management network element receives a second session establishment response from the second session association network element; and the first session establishment response is determined based on the second session establishment response.

[0033] In this implementation, since the terminal device belongs to the second PLMN, the first session management network element in the first PLMN will also inform the second session management network element in the second PLMN of the identifier of the network slice in the second PLMN associated with the session, so that the second session management network element establishes a session for the terminal device based on the identifier of the network slice in the second PLMN.

[0034] In one possible implementation, the second message further includes: information about a second session management network element in the second PLMN, where the information about the second session management network element is used by the first session management network element to find the second session management network element; or, the method further includes: the first session management network element determining the second session management network element in the second PLMN.

[0035] In a possible implementation, the first session management network element may also determine the first user plane network element in the first PLMN serving the terminal device based on the identifier of the second network slice in the first PLMN.

[0036] In a fourth aspect, a communication device is provided, which may be the access management network element described in the first aspect. The communication device has the functions of the access management network element. The communication device is, for example, a functional module in the access management network element, such as a baseband device or a chip system. Alternatively, the communication device may be the access management network element described in the second aspect. The communication device has the functions of the access management network element. The communication device is, for example, a functional module in the access management network element, such as a baseband device or a chip system. Alternatively, the communication device may be the first session management network element described in the third aspect. The communication device has the functions of the first session management network element. The communication device is, for example, a functional module in the first session management network element, such as a baseband device or a chip system.

[0037] In an optional implementation, the communication device includes a baseband device and a radio frequency device. In another optional implementation, the communication device includes a processing unit (sometimes also referred to as a processing module) and a transceiver unit (sometimes also referred to as a transceiver module). The transceiver unit can implement a sending function and a receiving function. When the transceiver unit implements the sending function, it can be called a sending unit (sometimes also referred to as a sending module). When the transceiver unit implements the receiving function, it can be called a receiving unit (sometimes also referred to as a receiving module). The sending unit and the receiving unit can be the same functional module, which is called a transceiver unit, and the functional module can implement a sending function and a receiving function; or, the sending unit and the receiving unit can be different functional modules, and the transceiver unit is a general term for these functional modules.

[0038] In one possible implementation, the communication device further includes a storage unit (sometimes also referred to as a storage module), and the processing unit is used to couple with the storage unit and execute the program or instructions in the storage unit, enabling the communication device to perform the function of the access management network element described in the first aspect above, or perform the function of the access management network element described in the second aspect above, or perform the function of the first session management network element described in the third aspect above.

[0039] When the communication device is the access management network element described in the first aspect, at least one of the following possible implementations is included:

[0040] In one possible implementation, the transceiver unit is used to receive a first message from an access network device, the first message including: a registration request of a terminal device belonging to a second PLMN, the registration request including: an identifier of a network slice in the second PLMN to which the terminal device requests to access; indirect network sharing exists between the second PLMN and the first PLMN; the transceiver unit is further used to send a second message to the access network device, the second message including: an identifier of a network slice in the first PLMN to which the terminal device is allowed to access and a registration response for sending to the terminal device; the registration response including: an identifier of a network slice in the second PLMN to which the terminal device is allowed to access; an identifier of a network slice in the first PLMN to which the terminal device is allowed to access is used to send to the access network device.

[0041] In one possible implementation, the registration response also includes: an identifier of the network slice in the second PLMN configured for the terminal device, and the identifier of the network slice in the second PLMN configured for the terminal device is determined based on the identifier of the network slice in the second PLMN to which the terminal device is subscribed.

[0042] In one possible implementation, the processing unit is used to save at least one of the following items in the context of the terminal device: a mapping relationship between an identifier of a network slice in the first PLMN that the terminal device is allowed to access and an identifier of a network slice in the second PLMN that the terminal device is allowed to access, and a mapping relationship between an identifier of a network slice in the first PLMN configured for the terminal device and an identifier of a network slice in the second PLMN configured for the terminal device.

[0043] In a possible implementation, the first message further includes: an identifier of an equivalent PLMN of the second PLMN, and the processing unit is further configured to determine, based on the identifier of the equivalent PLMN, that the terminal device is a terminal device accessed through indirect network sharing.

[0044] In one possible implementation, the processing unit is used to determine, based on the existence of indirect network sharing between the second PLMN and the first PLMN: the identifier of the network slice that the terminal device is allowed to access and sent to the terminal device is the identifier of the network slice in the second PLMN, and the identifier of the network slice that the terminal device is allowed to access and sent to the access network device is the identifier of the network slice in the first PLMN.

[0045] In one possible implementation, the processing unit is used to determine one or more of the following; or obtain one or more of the following from the network slice selection function network element in the first PLMN: the identifier of the network slice in the first PLMN that the terminal device is allowed to access, the identifier of the network slice in the second PLMN that the terminal device is allowed to access, the mapping relationship between the identifier of the network slice in the first PLMN that the terminal device is allowed to access and the identifier of the network slice in the second PLMN that the terminal device is allowed to access, the identifier of the network slice in the first PLMN configured for the terminal device, the identifier of the network slice in the second PLMN configured for the terminal device, the mapping relationship between the identifier of the network slice in the first PLMN configured for the terminal device and the identifier of the network slice in the second PLMN configured for the terminal device.

[0046] In one possible implementation, the one or more items are determined based on a mapping relationship between an identifier of a network slice in the second PLMN and an identifier of a network slice in the first PLMN.

[0047] In one possible implementation, the processing unit is used to map the identifier of the network slice in the second PLMN that the terminal device requests to access to the identifier of the network slice in the first PLMN requested to access based on the mapping relationship between the identifier of the network slice in the second PLMN and the identifier of the network slice in the first PLMN; determine the identifier of the network slice in the first PLMN that the terminal device is allowed to access based on the identifier of the network slice in the first PLMN requested to access; and map the identifier of the network slice in the first PLMN that the terminal device is allowed to access to the identifier of the network slice in the second PLMN allowed to access to the identifier of the network slice in the second PLMN allowed to access by the terminal device based on the mapping relationship between the identifier of the network slice in the second PLMN and the identifier of the network slice in the first PLMN.

[0048] When the communication device is the access management network element described in the second aspect, at least one of the following possible implementations is included:

[0049] In one possible implementation, the transceiver unit is used to receive a first message from a terminal device belonging to a second PLMN, where the first message is used to request to establish a session, and the first message includes: an identifier of a first network slice in the second PLMN; the first network slice is associated with the session requested to be established; and there is indirect network sharing between the second PLMN and the first PLMN; the transceiver unit is also used to send a second message to a first session management network element in the first PLMN, where the second message includes: an identifier of the first network slice in the second PLMN and an identifier of the second network slice in the first PLMN, and there is a mapping relationship between the identifier of the first network slice and the identifier of the second network slice; the transceiver unit is also used to receive a third message from the first session management network element, where the third message includes: an identifier of the second network slice in the first PLMN; the transceiver unit is also used to send a fourth message to an access network device serving the terminal device, where the fourth message includes: an identifier of the second network slice in the first PLMN and a first session establishment response for sending to the terminal device.

[0050] In one possible implementation, the third message also includes: an identifier of the first network slice in the second PLMN; and the first session establishment response includes: an identifier of the first network slice in the second PLMN.

[0051] In a possible implementation, the second message further includes: first indication information, where the first indication information is used to indicate that the terminal device is a terminal device accessed through indirect network sharing.

[0052] In one possible implementation, the processing unit is used to map the identifier of the first network slice in the second PLMN to the identifier of the second network slice in the first PLMN based on a mapping relationship between the identifier of the network slice in the second PLMN and the identifier of the network slice in the first PLMN.

[0053] In a possible implementation, the second message further includes: information about a second session management network element in the second PLMN, where the information about the second session management network element is used by the first session management network element to find the second session management network element.

[0054] When the communication device is the first session management network element described in the third aspect, at least one of the following possible implementations is included:

[0055] In one possible implementation, the transceiver unit is used to receive a second message from the access management function network element in the first PLMN during a process in which a terminal device belonging to the second PLMN requests to establish a session, the second message including: an identifier of a first network slice in the first PLMN and an identifier of a second network slice in the second PLMN, and a mapping relationship exists between the identifier of the first network slice and the identifier of the second network slice; the first network slice is associated with the session requested to be established; there is indirect network sharing between the second PLMN and the first PLMN; and send a third message to the access management function network element, the third message including: an identifier of the second network slice in the first PLMN for sending to the access network device and a first session establishment response for sending to the terminal device.

[0056] In one possible implementation, the first session establishment response includes: an identifier of the first network slice in the second PLMN.

[0057] In a possible implementation, the second message further includes: first indication information, where the first indication information is used to indicate that the terminal device is a terminal device accessed through indirect network sharing.

[0058] In one possible implementation, the processing unit is used to determine, based on the first indication information: sending an identifier of the network slice in the second PLMN to the terminal device, and sending an identifier of the network slice in the first PLMN to the access network device.

[0059] In one possible implementation, the transceiver unit is further used to send a fifth message to the second session management network element in the second PLMN, where the fifth message includes: an identifier of the first network slice in the second PLMN; and receiving a second session establishment response from the second session association network element; the first session establishment response is determined based on the second session establishment response.

[0060] In a possible implementation, the second message further includes: information about a second session management network element in the second PLMN, where the information about the second session management network element is used by the first session management network element to find the second session management network element; or, the processing unit is configured to determine the second session management network element in the second PLMN.

[0061] In one possible implementation, the processing unit is used to determine the first user plane network element in the first PLMN serving the terminal device based on the identifier of the second network slice in the first PLMN.

[0062] In a fifth aspect, a communication device is provided, comprising an interface circuit and a processor, and optionally, a memory. The memory is configured to store a computer program, and the processor is coupled to the memory and the interface circuit. When the processor reads the computer program or instructions, the communication device executes the method performed by the access management network element in the first aspect, the method performed by the access management network element in the second aspect, or the method performed by the first session management network element in the third aspect. Exemplarily, the interface circuit is configured to receive a signal from a communication device other than the communication device and transmit it to the processor, or to send a signal from the processor to a communication device other than the communication device. The processor implements the method performed by the access management network element in the first aspect, the method performed by the access management network element in the second aspect, or the method performed by the first session management network element in the third aspect through logic circuitry or by executing code instructions.

[0063] In a possible implementation, the communication device is a chip or a chip system.

[0064] In a sixth aspect, a communication device is provided, comprising a processor, and optionally, a memory; the processor and the memory are coupled; the memory is used to store computer programs or instructions; the processor is used to execute part or all of the computer programs or instructions in the memory, and when the part or all of the computer programs or instructions are executed, it is used to implement the function of the access management network element in the first aspect above, or to implement the function of the access management network element in the second aspect above, or to implement the function of the first session management network element in the third aspect above.

[0065] In one possible implementation, the apparatus may further include a transceiver configured to transmit a signal processed by the processor or receive a signal input to the processor. The transceiver may perform the transmitting action or receiving action performed by the access management network element in the first aspect, the access management network element in the second aspect, or the first session management network element in the third aspect.

[0066] In one possible implementation, the processing unit in the fourth, fifth and sixth aspects can be implemented by the processor, the storage unit in the fourth, fifth and sixth aspects can be implemented by the memory, and the transceiver unit in the fourth, fifth and sixth aspects can be implemented by the transceiver.

[0067] In a possible implementation, the communication device is a chip or a chip system.

[0068] In a seventh aspect, a communication system is provided, comprising an access management network element and a first session management network element, wherein the access management network element is configured to execute the methods described in the first and second aspects by the access management network element, and the first session management network element is configured to execute the method described in the third aspect by the first session management network element. For example, the access management network element and the first session management network element may be implemented by the communication device described in the fourth aspect.

[0069] In an eighth aspect, a computer-readable storage medium is provided, wherein the computer-readable storage medium is used to store computer programs or instructions, which, when executed, enables the method in the above-mentioned first aspect, second aspect, or third aspect to be implemented.

[0070] In a ninth aspect, a computer program product comprising instructions is provided, which, when executed on a computer, enables the method in the first aspect, or the second aspect, or the third aspect to be implemented. BRIEF DESCRIPTION OF THE DRAWINGS

[0071] FIG1a is a schematic diagram of the architecture of a 5G communication system provided by this application;

[0072] FIG1b is a schematic diagram of the architecture of another 5G communication system provided by this application;

[0073] FIG2a is a schematic diagram of a system architecture for indirect network sharing provided by the present application;

[0074] FIG2 b is a schematic diagram of a system architecture in which core network 1 and core network 2 are connected, as provided in the present application;

[0075] FIG3 is a flow chart of a communication method provided by the present application;

[0076] FIG4 is a flow chart of a communication method provided by the present application;

[0077] FIG5 is a flow chart of a communication method provided by the present application;

[0078] FIG6 is a flow chart of a communication method provided by the present application;

[0079] FIG7 is a flow chart of a communication method provided by the present application;

[0080] FIG8 is a flow chart of a communication method provided by the present application;

[0081] FIG9 is a structural diagram of a communication device provided by the present application;

[0082] FIG10 is a structural diagram of a communication device provided in this application. DETAILED DESCRIPTION

[0083] The technical solution of the present application can be applied to a terrestrial network (TN) or a non-terrestrial network (NTN), such as a satellite network. The technical solution of the present application can be applied to various wireless communication systems, and can be applied to, but not limited to, the fourth generation mobile communication technology (the 4th generation, 4G) system (also known as the long term evolution (LTE) system), the fifth generation mobile communication technology (the 5th generation, 5G) system (also known as the new radio (NR) system), or can also be applied to the next generation mobile communication system or other similar communication systems (such as the sixth generation mobile communication technology (the 6th generation, 6G) system), etc., without specific restrictions. In addition, the technical solution of the present application can be applied to device-to-device (D2D) scenarios, such as NR-D2D scenarios, etc., or can be applied to V2X scenarios, such as NR-V2X scenarios, etc. The technical solution of the present application can also be applied to fields such as intelligent driving, assisted driving, or intelligent connected vehicles, or factory manufacturing scenarios.

[0084] For example, Figure 1a is a schematic diagram of a 5G communication system architecture to which the present application may be applied. Specifically, Figure 1a is a schematic diagram of a 5G network architecture based on a service-oriented architecture. For example, Figure 1b is a schematic diagram of another 5G communication system architecture to which the present application may be applied. Specifically, Figure 1b is a schematic diagram of a 5G architecture based on point-to-point. The main difference between Figure 1a and Figure 1b is that the interface between the network elements in Figure 1a is a service-oriented interface, while the interface between the network elements in Figure 1b is a point-to-point interface.

[0085] The 5G network architecture shown in Figures 1a and 1b includes terminal equipment, an access network, and a core network. Optionally, it also includes data network (DN) and application function (AF) network elements. Terminals access the core network through the access network, and the core network communicates with the DN or AF. The following briefly describes the functions of some of these network elements.

[0086] A terminal device (UE), also known as user equipment (UE), is a device with wireless transceiver capabilities that can be deployed on land, including indoors or outdoors, handheld or vehicle-mounted; on water (such as ships); or in the air (such as airplanes, balloons, and satellites). The terminal device can be a mobile phone, tablet computer, computer with wireless transceiver capabilities, virtual reality (VR) terminal, augmented reality (AR) terminal, wireless terminal in industrial control, wireless terminal in self-driving, wireless terminal in remote medical, wireless terminal in smart grid, wireless terminal in transportation safety, wireless terminal in smart city, wireless terminal in smart home, etc.

[0087] The (R)AN device in this application is a device that provides wireless communication functions for terminal devices. The (R)AN device is also called an access network device. The RAN equipment in this application includes but is not limited to: the next generation base station (g nodeB, gNB) in 5G, evolved node B (evolved node B, eNB), radio network controller (radio network controller, RNC), node B (node ​​B, NB), base station controller (base station controller, BSC), base transceiver station (base transceiver station, BTS), home base station (for example, home evolved nodeB, or home node B, HNB), baseband unit (baseBand unit, BBU), transmission point (transmitting and receiving point, TRP), transmission point (transmitting point, TP), mobile switching center, etc. In systems using different wireless access technologies, the names of devices with base station functions may vary. For example, in the fifth generation (5G) system, it is called RAN or gNB (5G NodeB); in the LTE system, it is called evolved NodeB (eNB or eNodeB); in the third generation (3G) system, it is called Node B, etc.

[0088] A data network (DN) can deploy a variety of services, providing data and / or voice services to terminal devices. For example, a DN is the private network of a smart factory. Sensors installed in the workshop can be terminal devices. The DN contains sensors and a control server, which provides services to the sensors. Sensors can communicate with the control server, receive instructions from the control server, and transmit collected sensor data to the control server according to the instructions. Another example is a DN that is a company's internal office network. Employees' mobile phones or computers can be terminal devices, allowing them to access information and data resources on the company's internal office network.

[0089] The application network element mainly supports interaction with the 3rd Generation Partnership Project (3GPP) core network to provide services, such as influencing data routing decisions, policy control functions, or providing some third-party services to the network side. In the 5G communication system, the application network element can be an application function (AF) network element. In future communication systems, the application network element can still be an AF network element, or it can have other names, which are not limited in this application.

[0090] The core network may include one or more of the following network elements:

[0091] The access management network element (also known as the mobility management network element) is a control plane network element provided by the operator network, responsible for access control and mobility management of terminal devices accessing the operator network, such as mobile state management, allocation of user temporary identity, authentication and user functions. In the 5G communication system, the access management network element can be an access and mobility management function (AMF) network element. In future communication systems, the access management network element can still be an AMF network element, or it can have other names, which are not limited in this application.

[0092] The session management network element is primarily responsible for session management in mobile networks, such as session establishment, modification, and release. Specific functions include allocating IP addresses to users and selecting user plane network elements that provide message forwarding functions. In 5G communication systems, this session management network element may be a session management function (SMF) network element. In future communication systems, the session management network element may still be an SMF network element, or it may have other names, which are not limited in this application.

[0093] The user plane network element is responsible for forwarding and receiving user data in the terminal device. It can receive user data from the data network and transmit it to the terminal device through the access network device; the user plane network element can also receive user data from the terminal device through the access network device and forward it to the data network. The transmission resources and scheduling functions that provide services to the terminal device in the user plane network element are managed and controlled by the SMF network element. In the 5G communication system, the user plane network element can be a user plane function (UPF) network element. In future communication systems, the user plane network element can still be a UPF network element, or it can have other names, which are not limited in this application.

[0094] The data management network element is used for generating authentication credentials, user identification processing (such as storing and managing user permanent identities), access control, and contract data management. In a 5G communication system, this data management network element can be a unified data management (UDM) network element. In future communication systems, the unified data management can still be a UDM network element, or it can have other names, which are not limited in this application.

[0095] The data storage network element is responsible for storing structured data information, including contract information, policy information, and network data or service data defined in a standard format. In a 5G communication system, the data storage network element can be a unified data repository (UDR). In future communication systems, the network open function network element can still be a UDR network element, or it can have other names, which are not limited in this application.

[0096] The policy control network element mainly supports providing a unified policy framework to control network behavior, provides policy rules to the control layer network function, and is responsible for obtaining user subscription information related to policy decisions. In the 4G communication system, the policy control network element can be a policy and charging rules function (PCRF) network element. In the 5G communication system, the policy control network element can be a policy control function (PCF) network element. In future communication systems, the policy control network element can still be a PCF network element, or it can have other names, which are not limited in this application.

[0097] The network storage network element can be used to provide network element discovery function and provide network element information corresponding to the network element type based on the request of other network elements. NRF also provides network element management services, such as network element registration, update, deregistration, and network element status subscription and push. In the 5G communication system, the network storage network element can be a network repository function (NRF) network element. In future communication systems, the network storage network element can still be an NRF network element, or it can have other names, which are not limited in this application.

[0098] A network exposure function element can be used to securely expose services and capabilities provided by 3GPP network function devices to the outside world. In a 5G communication system, the network exposure function element can be a network exposure function (NEF) element. In future communication systems, the network exposure function element can still be an NEF element, or it can have other names, which are not limited in this application.

[0099] The network slice selection function network element can be used to select a suitable network slice for the terminal's service. In a 5G communication system, the network slice selection network element can be a network slice selection function (NSSF) network element. In future communication systems, the network open function network element can still be an NSSF network element, or it can have other names, which are not limited in this application.

[0100] The network data analysis function network element can collect data from various network functions (NFs), such as policy control network elements, session management network elements, user plane network elements, access management network elements, and application function network elements (through network capability exposure function network elements), and perform analysis and prediction. In a 5G communication system, the network data analysis network element can be a network data analysis function (NWDAF). In future communication systems, the network exposure function network element can still be an NWDAF network element, or it can have other names, which are not limited in this application.

[0101] It is understood that the above-mentioned network element or function can be a network element in a hardware device, a software function running on dedicated hardware, or a virtualized function instantiated on a platform (e.g., a cloud platform). In one possible implementation, the above-mentioned network element or function can be implemented by a single device, or can be implemented by multiple devices together, or can be a functional module within a single device, which is not specifically limited in the embodiments of the present application.

[0102] Figure 2a is a schematic diagram of the system architecture of indirect network sharing that can be applied to an embodiment of the present application. Operator 1 (operator 1) shares a base station managed by itself with operator 2 (operator 2). Operator 1 can also be called the hosting operator, and operator 2 can be called a participating operator. The base station is subsequently referred to as a shared RAN. There is an interconnection interface (such as N2 / N3 interface) between the shared base station and the core network 1 of operator 1, and there is no interconnection interface between the shared base station and the core network 2 of operator 2, that is, the shared base station is only managed by operator 1. There is an interconnection interface between core network 1 and core network 2, and data streams can be transmitted. A roaming architecture is adopted between core network 1 and core network 2. Figure 2b shows a possible schematic diagram of the architecture of network interconnection between operator 1's network and operator 2. It can be understood that there are multiple core network elements not drawn in Figure 2b.

[0103] When the terminal accesses the base station, it first synchronizes with the network downlink based on the synchronization signal sent by the base station, and then selects the operator's public land mobile network (PLMN) to access the base station. The shared base station broadcasts the identifier of operator 1's PLMN, and the terminal of operator 1 can access the shared base station based on operator 1's PLMN. In order to ensure that the terminal of operator 2 can access the shared base station, the shared base station will also broadcast the identifier of operator 2's equivalent public land mobile network (EPLMN) (note that it is not operator 2's PLMN, but operator 2's equivalent PLMN). When the terminal of operator 2 accesses the network, it selects operator 2's equivalent PLMN to access the shared base station. The shared base station sends operator 2's equivalent PLMN to the core network 1. The network elements in the core network 1 can determine that the terminal is a user accessing through indirect network sharing through operator 2's equivalent PLMN.

[0104] Network slicing is introduced in the scenario of indirect network sharing. If the terminal of operator 2 accesses the shared base station based on the equivalent PLMN of operator 2, then when the terminal registers and / or establishes a session, the network slice identifier sent to the network of operator 1 is the identifier of the network slice in operator 2. It is necessary to consider how to enable the terminal of operator 2 to normally access the network slice of operator 1 based on the network slice identifier sent by the terminal of operator 2.

[0105] Based on this, the present application proposes a communication method, in which the terminal belonging to operator 2 sends the identifier of the network slice of operator 2 to the core network 1 of operator 1, and the core network 1 returns the identifier of the network slice of operator 2 to the terminal. The terminal does not perceive the access network device connected to the network sharing, which can reduce the impact of indirect network sharing on the terminal; in addition, the core network 1 sends the identifier of the network slice of operator 1 to the shared base station, so that the shared base station can correctly identify which network slice to use to serve the terminal.

[0106] Below, some terms or concepts in the embodiments of the present application are explained to facilitate understanding by those skilled in the art.

[0107] 1) A network slice can be identified by single network slice selection assistance information (S-NSSAI). S-NSSAI includes slice type / service type (SST) and slice differentiator (SD). SST is used to describe the characteristics of the slice in terms of features and services; SD is used to distinguish different network slices with the same SST characteristics. SD is optional information and may not be included in S-NSSAI. A set of S-NSSAI, that is, multiple network slices, can be identified by network slice selection assistance information NSSAI.

[0108] 2) The terminal device belonging to OP#2 accesses the core network of OP#1 through the access network device. The access network device is managed by OP#1. There is an intercommunication interface (such as N2 / N3 interface) between the access network device and the core network of OP#1, and there is no intercommunication interface (such as N2 / N3 interface) between the access network device and the core network of OP#2. There is indirect network sharing between OP#1 and OP#2. The PLMN of OP#1 is called the first PLMN, and the PLMN of OP#2 is called the second PLMN, which can also be called the home PLMN (HPLMN). Indirect network sharing exists between the second PLMN and the first PLMN. The access network device or shared RAN mentioned in this application is the access network device for indirect network sharing between the second PLMN (or OP#2) and the first PLMN (or OP#1).

[0109] In an embodiment of the present application, the first PLMN and OP#1 can be replaced with each other; in addition, the identifier of the network slice in the first PLMN, the identifier of the network slice in the first PLMN, the identifier of the network slice in OP#1, the identifier of the network slice in OP#1, the NSSAI of OP#1 value, the NSSAI of OP#1 NSSAI value, and the OP#1 NSSAI value can be replaced with each other.

[0110] In an embodiment of the present application, the second PLMN and OP#2 can be replaced with each other; in addition, the identifier of the network slice in OP#2, the identifier of the network slice in OP#2, the identifier of the network slice in the HPLMN, the identifier of the network slice in the HPLMN, the identifier of the network slice in the second PLMN, the identifier of the network slice in the second PLMN, NSSAI of OP#2 value, NSSAI of HPLMN value, NSSAI of OP#2 NSSAI value, NSSAI of HPLMN NSSAI value, OP#2 NSSAI value, and HPLMN NSSAI value can be replaced with each other.

[0111] Network slice / NSSAI, for example: network slice requested for access / requested NSSAI, network slice allowed for access / allowed NSSAI, configured network slice / configured NSSAI, subscribed network slice / subscribed NSSAI, first network slice associated with the session, second network slice associated with the session, etc.

[0112] In the embodiments of the present application, the network slice requested for access, the network slice allowed for access, the configured network slice, the subscribed network slice, the first network slice associated with the session, and the second network slice associated with the session are all at the UE granularity. For example, the network slice requested for access refers to the network device requested for access by the terminal device, the network slice allowed for access refers to the network device allowed for access by the terminal device, the configured network slice refers to the network slice configured for the terminal device, and the subscribed network slice refers to the network slice subscribed by the terminal device. For the convenience of description, the term "terminal device" is omitted in some embodiments of the present application.

[0113] In order to better describe the embodiments of the present application, the following describes the methods provided by the embodiments of the present application in conjunction with the accompanying drawings. Unless otherwise specified, the steps indicated by dotted lines in the accompanying drawings corresponding to the various embodiments of the present application are all optional steps.

[0114] FIG3 is a schematic diagram of a communication process provided in an embodiment of the present application, including the following steps:

[0115] Step 301: A terminal device belonging to a second PLMN sends a registration request to an access network device, and the access network device receives the registration request. The registration request includes an identifier of a network slice in the second PLMN to which the terminal device requests access.

[0116] The access network device is an access network device in a first PLMN. The access network device may carry an identifier of the first PLMN in a broadcast message. Furthermore, indirect network sharing exists between the first PLMN and the second PLMN. An identifier of an equivalent PLMN of the second PLMN may be preconfigured in the access network device. In this way, the access network device may also carry an identifier of the equivalent PLMN of the second PLMN in a broadcast message. A terminal device belonging to the second PLMN may select the identifier of the equivalent PLMN of the second PLMN in the broadcast message to send a registration request to the access network device.

[0117] Step 302: The access network device sends a first message to the access management network element in the first PLMN. Correspondingly, the access management network element receives the first message, where the first message includes the registration request.

[0118] Further optionally, the first message further includes: an identifier of an equivalent PLMN of the second PLMN, the identifier of the equivalent PLMN being outside the registration request. The access management network element may determine, based on the identifier of the equivalent PLMN, that the terminal device is a terminal device accessed through indirect network sharing.

[0119] Step 303: The access management network element sends a second message to the access network device. Correspondingly, the access network device receives the second message, which includes: a registration response and an identifier of the network slice in the first PLMN that is allowed to be accessed.

[0120] The identifier of the network slice in the first PLMN allowed to be accessed is used to send to the access network device. The identifier of the network slice in the first PLMN allowed to be accessed refers to the identifier of the network slice in the first PLMN allowed to be accessed by the terminal device.

[0121] The registration response is used to send to the terminal device, and the registration response may be a registration acceptance response, and the registration response includes: an identifier of the network slice in the second PLMN that is allowed to be accessed. The identifier of the network slice in the second PLMN that is allowed to be accessed refers to the identifier of the network slice in the second PLMN that the terminal device is allowed to access.

[0122] Further optionally, the registration response also includes: an identifier of the network slice in the second PLMN configured for the terminal device; wherein the identifier of the network slice in the second PLMN configured for the terminal device is determined based on the identifier of the network slice in the second PLMN subscribed by the terminal device. Optionally, the access management network element may also obtain the identifier of the network slice in the second PLMN subscribed by the terminal device from a network element in the second PLMN (e.g., a UDM network element).

[0123] In a possible implementation, the access management network element may determine, based on the identifier of the equivalent PLMN of the second PLMN, that the identifier of the network slice sent to the terminal device is the identifier of the network slice in the second PLMN, and that the identifier of the network slice sent to the access network device is the identifier of the network slice in the first PLMN. Alternatively, based on the existence of indirect network sharing between the first PLMN and the second PLMN, it may be determined that the identifier of the network slice sent to the terminal device is the identifier of the network slice in the second PLMN, and that the identifier of the network slice sent to the access network device is the identifier of the network slice in the first PLMN.

[0124] Step 304: The access network device sends the registration response in step 303 to the terminal device.

[0125] Step 305: The access management network element saves at least one of the following items in the context of the terminal device: a mapping relationship between the identifier of the network slice in the first PLMN allowed to access and the identifier of the network slice in the second PLMN allowed to access, and a mapping relationship between the identifier of the network slice in the first PLMN configured for the terminal device and the identifier of the network slice in the second PLMN configured for the terminal device.

[0126] Step 305 is an optional step, and the order of step 303 and step 305 is not limited.

[0127] In this embodiment, in the registration process of a terminal device belonging to the second PLMN, the terminal device sends an identifier of a network slice in the second PLMN to a network element in the first PLMN. Considering that the terminal device is a device belonging to the second PLMN, the identifier of the network slice allowed to be accessed sent to the terminal device is the identifier of the network slice in the second PLMN. The terminal device does not perceive that it has accessed an access network device for network sharing, which can reduce the impact of indirect network sharing on the terminal. Considering that the access network device is a device in the first PLMN, the identifier of the network slice allowed to be accessed sent to the access network device is the identifier of the network slice in the first PLMN. This can ensure that the access network device correctly identifies which network slice to use to serve the terminal. In addition, the access management network element saves the mapping relationship between the identifiers of the network slices in the context of the terminal device to accurately provide services to the terminal device.

[0128] The one or more pieces of information mentioned in the above steps 303 and 305 (for example, the identifier of the network slice in the first PLMN that is allowed to be accessed in the first PLMN and the identifier of the network slice in the second PLMN and the mapping relationship between the two, the identifier of the network slice in the first PLMN configured for the terminal and the identifier of the network slice in the second PLMN and the mapping relationship between the two) are determined by one or more network elements in the first PLMN. For example, the access management network element (for example, the AMF network element) in the first PLMN determines this one or more pieces of information. The access management network element can be the initial access management network element or the target access management network element after relocation. For another example, the network slice selection function network element (for example, the NSSF network element) in the first PLMN determines this one or more pieces of information. For another example, the access management network element and the network slice selection function network element in the first PLMN jointly determine this one or more pieces of information.

[0129] In conjunction with the content of Figure 3, the following takes the initial AMF determination as an example: the identifier of the network slice in the first PLMN (or replaced by OP#1) allowed to access and the identifier of the network slice in the second PLMN (or replaced by OP#2) and the mapping relationship between the two, the identifier of the network slice in the first PLMN configured for the terminal device and the identifier of the network slice in the second PLMN and the mapping relationship between the two, as shown in Figure 4, a detailed communication process diagram is introduced, including the following steps:

[0130] Step 400a: The EPLMN ID of OP#2 is pre-configured in the shared RAN of OP#1. The shared RAN may carry the EPLMN ID of OP#2 in a broadcast message.

[0131] In addition, it can be understood that the PLMN ID of OP#1 can be pre-configured in the shared RAN of OP#1, and the shared RAN can carry the PLMN ID of OP#1 in the broadcast message.

[0132] Step 400b: The EPLMN ID of OP#2 is pre-configured in the AMF of OP#1, and the mapping relationship of the network slices (S-NSSAI) between OP#1 and OP#2 is also configured.

[0133] For example, the S-NSSAI values ​​of OP#1 include S-NSSAI#a, S-NSSAI#b, S-NSSAI#c, and S-NSSAI#d; the S-NSSA values ​​of OP#2 include S-NSSAI#A, S-NSSAI#B, S-NSSAI#C, and S-NSSAI#D. The mapping relationship is: S-NSSAI#a maps to S-NSSAI#A, S-NSSAI#b maps to S-NSSAI#B, S-NSSAI#c maps to S-NSSAI#C, and S-NSSAI#d maps to S-NSSAI#D.

[0134] As shown in Table 1, a mapping relationship of S-NSSAI between OP#1 and OP#2 is introduced. It can be understood that the mapping relationship can be expressed in the form of a table or in other forms.

[0135] Table 1: S-NSSAI mapping relationship between OP#1 and OP#2.

[0136] In addition, it can be understood that the PLMN ID of OP#1 can be pre-configured in the AMF of OP#1.

[0137] Step 400c: OP#1's shared RAN carries OP#2's EPLMN ID in the broadcast message.

[0138] Optionally, the shared RAN of OP#1 may carry not only the EPLMN ID of OP#2 but also the PLMN ID of OP#1 in the broadcast message, which is not limited in this application.

[0139] Step 401: The UE of OP#2 sends an RRC message to the shared RAN, where the RRC message includes a registration request message (the registration request message is a NAS message).

[0140] The UE of OP#2 selects the EPLMN ID of OP#2 to access the shared RAN, and then sends an RRC message to the shared RAN.

[0141] For example, the registration request message includes the UE identifier and the identifier of the network slice in OP#2 to which the UE requests access (which may be referred to as the requested NSSAI of OP#2 value). For example, the identifier of the network slice in OP#2 to which the UE requests access includes the identifiers of one or more network slices, for example, the requested NSSAI of OP#2 value may be one or more of S-NSSAI#A and S-NSSAI#B. For example, the UE identifier is a user permanent identifier (SUPI), and the SUPI includes the PLMN ID of OP#2.

[0142] Optionally, in addition to the NAS message, the RRC message also includes: the identifier of the network slice in OP#2 to which access is requested. In the embodiment of the present application, the identifier of the network slice in OP#2 to which access is requested other than the NAS message is not introduced in detail.

[0143] Step 402: The shared RAN determines the AMF.

[0144] For example, the shared RAN determines the AMF based on the PLMN selected by the UE. The identifier of the PLMN selected by the UE is the EPLMN ID of OP#2. The AMF determined in step 402 is called the initial AMF.

[0145] Step 403: The shared RAN sends an N2 message to the initial AMF. The N2 message includes: the identifier of the PLMN selected by the UE (i.e., the EPLMN ID of OP#2) and the registration request message (NAS message) in step 401.

[0146] Step 404: The initial AMF determines that the UE is a user accessing through indirect network sharing.

[0147] For example: the initial AMF determines that the UE is a user accessed through indirect network sharing based on the identifier of the PLMN selected by the UE (i.e., the EPLMN ID of OP#2). For example, if the initial AMF determines that the identifier of the PLMN selected by the UE is different from the identifier of the PLMN of OP#1, it can be determined that the UE is a user accessed through indirect network sharing. Further optionally, the initial AMF can also determine that the UE is a user accessed through indirect network sharing based on the identifier of the UE in the NAS message. For example, the initial AMF can determine that the PLMN to which the UE belongs is PLMN#2 (i.e., OP#2) based on the identifier of the UE. The initial AMF pre-configured that there is an indirect network sharing (indirect network sharing) relationship between OP#1 and OP#2, and therefore determines that the UE is a user accessed through indirect network sharing.

[0148] Step 405: The initial AMF obtains the identifier of the network slice subscribed by the UE in OP#2 (subscribed NSSAI of OP#2 value) from the network element of OP#2 (e.g., UDM).

[0149] The initial AMF determines that the UE is a user accessing through indirect network sharing, and may determine OP#2 based on the identifier of the PLMN selected by the UE (i.e., the EPLMN ID of OP#2). Alternatively, the initial AMF determines that the UE is a user accessing through indirect network sharing, and may determine OP#2 based on the UE identifier. For example, the UE identifier may be a Subscription Permanent Identifier (SUPI), which includes the PLMN ID of OP#2.

[0150] For example, the subscribed NSSAI of OP#2 value includes: S-NSSAI#A, S-NSSAI#B, S-NSSAI#C, and S-NSSAI#D.

[0151] Step 406: The initial AMF determines the identifiers of the network slices in OP#1 and OP#2 that are allowed to be accessed and the mapping relationship between the two, and the identifiers of the network slices in OP#1 and OP#2 configured for the terminal and the mapping relationship between the two. Specifically, it includes the following multiple contents: the identifier of the network slice in OP#1 that is allowed to be accessed (which can be called allowed NSSAI of OP#1 value), the identifier of the network slice in OP#2 that is allowed to be accessed (which can be called allowed NSSAI of OP#2 value), the mapping relationship between the identifier of the network slice in OP#1 that is allowed to be accessed and the identifier of the network slice in OP#2 (which can be called mapping of allowed NSSAI), the identifier of the network slice in OP#1 configured for the UE (which can be called configured NSSAI of OP#1 value), the identifier of the network slice in OP#2 configured for the UE (which can be called configured NSSAI of OP#2 value), and the mapping relationship between the identifier of the network slice in OP#1 configured for the UE and the identifier of the network slice in OP#2 (which can be called mapping of configured NSSAI).

[0152] The network slice allowed for access is determined based on the network slice requested for access and the network slice contracted for access. The network slice allowed for access belongs to the network slice requested for access and to the network slice contracted for access. The following describes an example of the initial AMF determining the identifier of the network slice in OP#2 allowed for access and the identifier of the network slice in OP#1 allowed for access:

[0153] In one example: the initial AMF can map the identifier of the network slice in OP#2 requested for access (Requested NSSAI of OP#2 value) to the identifier of the network slice in OP#1 requested for access (Requested NSSAI of OP#1 value) based on the mapping relationship between the S-NSSAI of OP#1 and OP#2 configured locally. For example, the identifier of the network slice in OP#2 requested for access includes: S-NSSAI#A and S-NSSAI#B, and after mapping, S-NSSAI#a and S-NSSAI#b are obtained. The initial AMF can also map the identifier of the network slice in the contracted OP#2 to the identifier of the network slice in the contracted OP#1 based on the mapping relationship between the S-NSSAI of OP#1 and OP#2 configured locally. For example, the identifiers of the network slices in the subscribed OP#2 include: S-NSSAI#A, S-NSSAI#B, S-NSSAI#C and S-NSSAI#D, and after mapping, S-NSSAI#a, S-NSSAI#b, S-NSSAI#c and S-NSSAI#d are obtained. The initial AMF selects the identifier of the network slice in OP#1 that is allowed to access from the identifier of the network slice in OP#1 that requests access and the identifier of the network slice in the subscribed OP#1, wherein the identifier of the network slice in OP#1 that is allowed to access belongs to the identifier of the network slice in OP#1 that requests access and belongs to the identifier of the network slice in OP#1 that is subscribed.

[0154] The initial AMF can also map the identifier of the network slice in OP#1 that is allowed to access to the identifier of the network slice in OP#2 that is allowed to access based on the mapping relationship between the S-NSSAI of OP#1 and OP#2 configured locally.

[0155] In another example, the initial AMF does not map the identifier of the network slice in OP#2 requested for access to OP#1, nor does it map the identifier of the network slice in the subscribed OP#2 to OP#1. The initial AMF may select the identifier of the network slice in OP#2 allowed for access from the identifier of the network slice in OP#2 requested for access and the identifier of the network slice in OP#2 subscribed to, wherein the identifier of the network slice in OP#2 allowed for access belongs to the identifier of the network slice in OP#2 requested for access and belongs to the identifier of the subscribed network slice OP#2.

[0156] The initial AMF can also map the identifier of the network slice in OP#2 that is allowed to access to the identifier of the network slice in OP#1 that is allowed to access based on the mapping relationship between the S-NSSAI of OP#1 and OP#2 configured locally.

[0157] The initial AMF in OP#1 may not be able to know the type of network slice requested for access or the type of business it is responsible for based on the identifier of the network slice in OP#2 for which access is requested. The initial AMF in OP#1 may not be able to know the type of network slice contracted for or the type of business it is responsible for based on the identifier of the network slice in OP#2 for which access is requested.

[0158] The following describes an example of the initial AMF determining the identifier of the network slice configured for the UE in OP#2 and the identifier of the network slice configured for the UE in OP#1:

[0159] The network slice configured for the UE is determined based on the subscribed network slice, and the network slice configured for the UE is part or all of the subscribed network slice.

[0160] In one example, the initial AMF maps the identifier of the network slice in the contracted OP#2 to the identifier of the network slice in the contracted OP#1 according to the mapping relationship between the S-NSSAI of OP#1 and OP#2 configured locally, and selects the identifier of the network slice in OP#1 configured for the UE from the identifiers of the network slice in the contracted OP#1. The initial AMF may also map the identifier of the network slice in OP#1 configured for the UE to the identifier of the network slice in OP#2 configured for the UE according to the mapping relationship between the S-NSSAI of OP#1 and OP#2 configured locally.

[0161] In another example, the initial AMF selects the identifier of the network slice in OP#2 configured for the UE from the identifier of the network slice in the subscribed OP#2. The initial AMF may also map the identifier of the network slice in OP#2 configured for the UE to the identifier of the network slice in OP#1 configured for the UE based on the mapping relationship between the S-NSSAI of the locally configured OP#1 and OP#2. The initial AMF in OP#1 may not be able to know the type of the subscribed network slice or the type of service it is responsible for based on the identifier of the network slice in OP#2 subscribed by the UE.

[0162] In one possible implementation, one or more of the multiple contents determined by the initial AMF in step 406 may also be determined by other functional network elements (such as NSSF) in OP#1, and the initial AMF may send the information necessary to determine the one or more items to the other functional network elements. For example, the necessary information includes: the mapping relationship between the S-NSSAI of OP#1 and OP#2, the identifier of the network slice in OP#2 requesting access, and the identifier of the network slice in the subscribed OP#2. In addition, the mapping relationship between the S-NSSAI of OP#1 and OP#2 may also be pre-configured in other functional network elements in advance, without the need for the initial AMF to send it; the identifier of the network slice in the subscribed OP#2 may also be obtained by other functional network elements from the network element in OP#2 (such as UDM), without the need for the initial AMF to send it. After obtaining the necessary information, the other functional network elements determine the one or more items in the same way as the initial AMF, and then send them to the initial AMF.

[0163] Step 407: The initial AMF saves the mapping relationship between the identifier of the network slice related to the UE in OP#1 and the identifier of the network slice related to the UE in OP#2 in the context of the UE.

[0164] For example, save: the mapping relationship between the identifier of the network slice in OP#1 that the UE is allowed to access and the identifier of the network slice in OP#2 allowed by the UE (mapping of allowed NSSAI), and the mapping relationship between the identifier of the network slice in OP#1 configured for the UE and the identifier of the network slice in OP#2 configured for the UE (mapping of configured NSSAI).

[0165] Step 408: The initial AMF sends an N2 message to the shared RAN, and accordingly, the shared RAN receives the N2 message; the N2 message includes: the identifier of the network slice in OP#1 allowed for access (allowed NSSAI of OP#1 value) sent to the shared RAN and a registration response message sent to the UE (the registration response message is a NAS message).

[0166] After the shared RAN receives the allowed NSSAI of OP#1 value, it can save the allowed NSSAI of OP#1 value to the UE context.

[0167] For example, the registration response includes the identifier of the network slice in OP#2 that is allowed to be accessed (allowed NSSAI of OP#2 value). Optionally, the registration response also includes: the identifier of the network slice in OP#2 configured for the UE (configured NSSAI of OP#2 value). For example, the identifier of the network slice in OP#2 that the UE reports and requests to access includes: S-NSSAI#A and S-NSSAI#B, and the identifier of the network slice in OP#2 that is allowed to be accessed issued to the UE includes: S-NSSAI#A and S-NSSAI#B. For example, the identifier of the network slice in OP#2 configured for the UE includes: S-NSSAI#A, S-NSSAI#B, S-NSSAI#C and S-NSSAI#D.

[0168] The order of step 407 and step 408 is not limited.

[0169] Step 409: The shared RAN sends the registration response message (NAS message) in step 408 to the UE. The UE receives the registration response message. The UE saves the identifier of the network slice in OP#2 allowed for access (allowed NSSAI of OP#2 value) in the registration response message. Optionally, it also saves the identifier of the network slice in OP#2 configured for the UE (configured NSSAI of OP#2 value).

[0170] Optionally, after step 406, the initial AMF may also interact with the policy control network element (e.g., PCF) to obtain the policy information for UE access to OP#1 from the policy control network element. For example, the initial AMF sends to the policy control network element: the identifier of the terminal device (e.g., SUPI), the identifier of the network slice in OP#1 allowed to be accessed, and indication information; wherein, the indication information is used to indicate that the UE is a user accessing through indirect network sharing. The information sent by the initial AMF to the policy control network element may be carried in an AM policy assocaition establishment request. The policy control network element determines the policy information for UE access to OP#1 based on the indication information and / or the identifier of the network slice in OP#1 allowed to be accessed, and then sends the policy information for UE access to OP#1 to the initial AMF, and the policy information may be carried in an AM policy assocaition establishment responset. The initial AMF may also send the policy information for UE access to OP#1 to the UEs in the shared RAN and OP#2. For example, the policy information includes a radio frequency selection priority (RAT / frequency selection priority, RFSP) index. The policy control network element can also save the identifier of the network slice in OP#1 that the UE is allowed to access for subsequent use.

[0171] In conjunction with the content of Figure 3, the target AMF after relocation determines: the identifier of the network slice in the first PLMN (or replaced by OP#1) allowed to access and the identifier of the network slice in the second PLMN (or replaced by OP#2) and the mapping relationship between the two, the identifier of the network slice in the first PLMN configured for the terminal device and the identifier of the network slice in the second PLMN and the mapping relationship between the two as an example, as shown in Figure 5, a detailed communication process diagram is introduced, including the following steps:

[0172] Step 500a, step 500b, and step 500c may refer to step 400a, step 400b, and step 400c, respectively.

[0173] In addition, it should be noted that in step 500b, OP#1's AMF includes the initial AMF and the target AMF. That is, both the initial AMF and the target AMF will be pre-configured with OP#1's PLMN, OP#2's EPLMN ID, and the S-NSSAI mapping relationship between OP#1 and OP#2. In addition, the mapping relationship between OP#2's EPLMN ID and the S-NSSAI between OP#1 and OP#2 will also be pre-configured in the NSSF.

[0174] Steps 501 to 505 may refer to steps 401 and 405 respectively, and will not be described in detail.

[0175] Step 505, in which the initial AMF obtains the identifier of the network slice subscribed by the UE in OP#2 (subscribed NSSAI of OP#2 value) from the network element of OP#2 (e.g., UDM), is an optional step. In this embodiment, since the switch is to be made from the initial AMF to the target AMF, in addition to the initial AMF obtaining the identifier of the network slice subscribed by the UE in OP#2 from the network element of OP#2 (e.g., UDM), the target AMF can also obtain the identifier of the network slice subscribed by the UE in OP#2 from the network element of OP#2 (e.g., UDM).

[0176] Step 506: The initial AMF determines that it cannot serve the UE in OP#2 and AMF relocation is required. The initial AMF obtains the target AMF information from the Network Slice Selection Function (NSSF).

[0177] For example, the initial AMF sends the identifier of the network slice in OP#2 that the UE requests to access to the NSSF. The NSSF maps the identifier of the network slice in OP#2 that the UE requests to access to the identifier of the network slice in OP#1 based on the pre-configured S-NSSAI mapping relationship between OP#1 and OP#2. The NSSF determines the target AMF based on the identifier of the network slice in OP#1 that the UE requests to access, and sends the information of the target AMF to the initial AMF.

[0178] Step 507: An AMF relocation process is performed between the initial AMF and the target AMF.

[0179] Step 508: The initial AMF sends the following information to the target AMF: the UE identifier (e.g., SUPI), the identifier of the network slice in OP#2 to which access is requested, and indication information.

[0180] This indication information is used to indicate that the UE is a user accessing through indirect network sharing. For example, the indication information is: OP#2's HPLMN. For another example, the indication information occupies 1 bit. For example, when the 1 bit value is 1, it indicates that the UE is a user accessing through indirect network sharing. When the 1 bit value is 0, it indicates that the UE is not a user accessing through indirect network sharing. Optionally, if the indication information does not include OP#2's HPLMN, the initial AMF may also send OP#2's HPLMN to the target AMF.

[0181] Optionally, in step 508, the initial AMF may also send the identifier of the network slice in OP#2 to which the UE is subscribed obtained in step 505 to the target AMF.

[0182] Step 509: The target AMF determines, based on the indication information in step 508, that the UE is a user accessing through indirect network sharing.

[0183] Optionally, step 510: the target AMF determines OP#2 based on the EPLMN ID of OP#2, and the target AMF obtains the identifier of the network slice subscribed by the UE in OP#2 (subscribed NSSAI of OP#2 value) from the network element of OP#2 (e.g., UDM). For example, the subscribed NSSAI of OP#2 value includes: S-NSSAI#A, S-NSSAI#B, S-NSSAI#C, and S-NSSAI#D. If the initial AMF sends the identifier of the network slice in OP#2 subscribed by the UE to the target AMF in step 508, step 510 may not be performed.

[0184] Step 511 and the steps thereafter are similar to step 406 and the steps thereafter, except that the execution subject is replaced by the target AMF instead of the initial AMF.

[0185] Step 511: The target AMF determines the identifiers of the network slices in OP#1 and OP#2 that are allowed to be accessed and the mapping relationship between the two, and the identifiers of the network slices in OP#1 and OP#2 configured for the terminal and the mapping relationship between the two. Specifically, it includes the following multiple contents: the identifier of the network slice in OP#1 that is allowed to be accessed (which can be called allowed NSSAI of OP#1 value), the identifier of the network slice in OP#2 that is allowed to be accessed (which can be called allowed NSSAI of OP#2 value), the mapping relationship between the identifier of the network slice in OP#1 that the UE is allowed to access and the identifier of the network slice in OP#2 (which can be called mapping of allowed NSSAI), the identifier of the network slice in OP#1 configured for the UE (which can be called configured NSSAI of OP#1 value), the identifier of the network slice in OP#2 configured for the UE (which can be called configured NSSAI of OP#2 value), and the mapping relationship between the identifier of the network slice in OP#1 configured for the UE and the identifier of the network slice in OP#2 (which can be called mapping of configured NSSAI).

[0186] The process of the target AMF determining these contents is the same as the process of the initial AMF determining these contents in step 406. Please refer to the description in step 406 and will not be repeated in detail.

[0187] In one possible implementation, one or more of the multiple contents determined by the target AMF in step 511 may also be determined by other functional network elements (such as NSSF) in OP#1, and the target AMF can send the information necessary to determine the one or more items to the other functional network elements. For example, the necessary information includes: the mapping relationship between the S-NSSAI of OP#1 and OP#2, the identifier of the network slice in OP#2 requesting access, and the identifier of the network slice in the subscribed OP#2. In addition, the mapping relationship between the S-NSSAI of OP#1 and OP#2 may also be pre-configured in other functional network elements in advance, without the need for the target AMF to send it; the identifier of the network slice in the subscribed OP#2 may also be obtained by other functional network elements from the network element in OP#2 (such as UDM), without the need for the target AMF to send it. After obtaining the necessary information, the other functional network elements determine the one or more items in the same way as the target AMF, and then send them to the target AMF.

[0188] Step 512: The target AMF saves the mapping relationship between the identifier of the network slice related to the UE in OP#1 and the identifier of the network slice related to the UE in OP#2 in the context of the UE.

[0189] For example, save: the mapping relationship between the identifier of the network slice in OP#1 that the UE is allowed to access and the identifier of the network slice in OP#2 that the UE is allowed to access (mapping of allowed NSSAI), and the mapping relationship between the identifier of the network slice in OP#1 configured for the UE and the identifier of the network slice in OP#2 configured for the UE (mapping of configured NSSAI).

[0190] Step 513: The target AMF sends an N2 message to the shared RAN, and accordingly, the shared RAN receives the N2 message; the N2 message includes: the identifier of the network slice in the OP#1 allowed to access (allowed NSSAI of OP#1 value) sent to the shared RAN and the registration response message (NAS message) sent to the UE.

[0191] After the shared RAN receives the allowed NSSAI of OP#1 value, it can save the allowed NSSAI of OP#1 value to the UE context.

[0192] The registration response is a registration acceptance. For example, the registration response includes the identifier of the network slice in OP#2 that is allowed to be accessed (allowed NSSAI of OP#2 value). Optionally, the registration response also includes: the identifier of the network slice in OP#2 configured for the UE (configured NSSAI of OP#2 value). For example, the identifier of the network slice in OP#2 that the UE requests to access includes: S-NSSAI#A and S-NSSAI#B, and the identifier of the network slice in OP#2 that is allowed to be accessed issued to the UE includes: S-NSSAI#A and S-NSSAI#B. For example, the identifier of the network slice in OP#2 configured for the UE includes: S-NSSAI#A, S-NSSAI#B, S-NSSAI#C and S-NSSAI#D.

[0193] The order of step 512 and step 513 is not limited.

[0194] Step 514: The shared RAN sends the registration response message (NAS message) in step 513 to the UE. The UE receives the registration response message (NAS message). The UE saves the identifier of the network slice in OP#2 allowed for access (allowed NSSAI of OP#2 value) in the NAS message. Optionally, it also saves the identifier of the network slice in OP#2 configured for the UE (configured NSSAI of OP#2 value).

[0195] Optionally, after step 511, the target AMF may also interact with the policy control network element (e.g., PCF) to obtain the policy information for UE access to OP#1 from the policy control network element. For example, the target AMF sends to the policy control network element: the identifier of the terminal device (e.g., SUPI), the identifier of the network slice in OP#1 allowed to be accessed, and indication information; wherein, the indication information is used to indicate that the UE is a user accessing through indirect network sharing. The information sent by the target AMF to the policy control network element may be carried in an AM policy assocaition establishment request. The policy control network element determines the policy information for UE access to OP#1 based on the indication information and / or the identifier of the network slice in OP#1 allowed to be accessed, and then sends the policy information for UE access to OP#1 to the target AMF, and the policy information may be carried in an AM policy assocaition establishment responset. The target AMF may also send the policy information for UE access to OP#1 to the UEs in the shared RAN and OP#2. For example, the policy information includes a radio frequency selection priority (RAT / frequency selection priority, RFSP) index. The policy control network element can also save the identifier of the network slice in OP#1 that is allowed to access for subsequent use.

[0196] In conjunction with the content of Figure 3, the following takes the example where the initial AMF determines through the NSSF: the identifier of the network slice in the first PLMN allowed to be accessed and the identifier of the network slice in the second PLMN and the mapping relationship between the two, the identifier of the network slice in the first PLMN configured for the terminal and the identifier of the network slice in the second PLMN and the mapping relationship between the two, and the initial AMF sends this information to the target AMF after relocation. As shown in Figure 6, a detailed communication process diagram is introduced, including the following steps:

[0197] Step 600a, step 600b, and step 600c may refer to step 500a, step 500b, and step 500c, respectively.

[0198] Steps 601 to 605 may refer to steps 501 and 505 respectively, and will not be described in detail.

[0199] Step 606: The initial AMF sends the following information to the NSSF: the PLMN of OP#2, the identifier of the network slice in OP#2 that the UE requests to access (requested NSSAI of OP#2 value), and the identifier of the network slice in OP#2 that the UE subscribes to (subscribed NSSAI of OP#2 value).

[0200] The PLMN of OP#2 may be derived from the identifier of the UE. For example, the identifier of the UE may be a subscription permanent identifier (SUPI), and the SUPI includes the PLMN ID of OP#2.

[0201] In addition, the initial AMF determines that it cannot serve the UE in OP#2 and AMF relocation is required. The initial AMF can also request the NSSF network element to determine the information of the target AMF.

[0202] The information initially sent by the AMF to the NSSF in step 606 is carried in Nnssf_NSSelection_GetRequest.

[0203] Step 607: NSSF sends one or more of the following information to the initial AMF: information of the target AMF, identifiers of the network slices in OP#1 and OP#2 that are allowed to be accessed and the mapping relationship between the two, identifiers of the network slices in OP#1 and OP#2 configured for the terminal and the mapping relationship between the two. Specifically, it includes the following information: the identifier of the network slice in OP#1 that is allowed to be accessed (which may be called allowed NSSAI of OP#1 value), the identifier of the network slice in OP#2 that is allowed to be accessed (which may be called allowed NSSAI of OP#2 value), the mapping relationship between the identifier of the network slice in OP#1 that the UE is allowed to access and the identifier of the network slice in OP#2 that the UE is allowed to access (which may be called mapping of allowed NSSAI), the identifier of the network slice in OP#1 configured for the UE (which may be called configured NSSAI of OP#1 value), the identifier of the network slice in OP#2 configured for the UE (which may be called configured NSSAI of OP#2 value), the mapping relationship between the identifier of the network slice in OP#1 configured for the UE and the identifier of the network slice in OP#2 configured for the UE (which may be called mapping of configured NSSAI).

[0204] After receiving the information from the initial AMF, NSSF determines the one or more contents. The process of NSSF determining these contents is the same as the process of the initial AMF determining these contents in step 406. Please refer to the description in step 406 and will not be repeated in detail.

[0205] The information sent by NSSF to the initial AMF in step 607 is carried in Nnssf_NSSelection_GetResponse.

[0206] Step 608: An AMF relocation process is performed between the initial AMF and the target AMF.

[0207] Step 609: The initial AMF sends one or more of the following information to the target AMF: UE identification (e.g., SUPI), indication information, identification and mapping relationship of the network slices in OP#1 and OP#2 allowed to be accessed, and identification and mapping relationship of the network slices in OP#1 and OP#2 configured for the UE.

[0208] This indication information is used to indicate that the UE is a user accessing through indirect network sharing. For example, the indication information is: OP#2's HPLMN. For another example, the indication information occupies 1 bit. For example, when the 1 bit value is 1, it indicates that the UE is a user accessing through indirect network sharing. When the 1 bit value is 0, it indicates that the UE is not a user accessing through indirect network sharing. Optionally, if the indication information does not include OP#2's HPLMN, the initial AMF may also send OP#2's HPLMN to the target AMF.

[0209] The information sent by the initial AMF to the target AMF in step 609 is carried in Namf_communication N1 MessageNotify.

[0210] Step 610 and the steps thereafter are the same as step 511 and the steps thereafter, and will not be repeated.

[0211] In a possible implementation, the information sent by the NSSF to the initial AMF in step 607 does not include: the identifier of the network slice in OP#2 allowed for access (which may be called allowed NSSAI of OP#2 value) and the identifier of the network slice in OP#2 configured for the UE (which may be called configured NSSAI of OP#2 value). Then in step 609, the information sent by the initial AMF to the target AMF does not include: the identifier of the network slice in OP#2 allowed for access and the identifier of the network slice in OP#2 configured for the UE. Then the target AMF needs to map the identifier of the network slice in OP#1 allowed for access to the identifier of the network slice in OP#2 allowed for access, and map the identifier of the network slice in OP#1 configured for the UE to the identifier of the network slice in OP#2 configured for the UE based on the mapping relationship. The target AMF then carries the identifier of the network slice in OP#2 allowed for access and the identifier of the network slice in OP#2 configured for the UE in a registration response message (NAS message) and sends it to the UE.

[0212] The foregoing describes embodiments related to the registration of a terminal device belonging to a second PLMN. The following describes embodiments for establishing a session by a terminal device belonging to a second PLMN.

[0213] As shown in FIG7 , a flow chart of a communication method is introduced, which includes the following steps:

[0214] Step 701: A terminal device belonging to a second PLMN sends a first message, and correspondingly, an access management network element in a first PLMN receives the first message.

[0215] The first message is used to request to establish a session, where the session is a session between the terminal device and the core network of the PLMN (i.e., the second PLMN) to which the terminal device belongs. For example, the first message includes an N1 SM container, which carries the session establishment request.

[0216] The first message also includes: an identifier of a first network slice in the second PLMN, where the first network slice is a network slice associated with the session. The number of first network slices may be one or more. For example, the identifier of the first network slice in the second PLMN includes: S-NSSAI#A, S-NSSAI#B. Optionally, the first message may also include an identifier of the session.

[0217] The first message is a NAS message, and the access network device transparently transmits the NAS message from the terminal device to the access management network element. After receiving the NAS message, the access management network element can parse the above-mentioned contents.

[0218] Step 702: The access management network element in the first PLMN sends a second message, and accordingly, the first session management network element in the first PLMN receives the second message. The second message includes: an identifier of a first network slice in the second PLMN and an identifier of a second network slice in the first PLMN, and there is a mapping relationship between the identifier of the first network slice and the identifier of the second network slice.

[0219] The access management network element may select a first session management network element in the first PLMN. For example, the access management network element selects the first session management network element based on the identifier of the second network slice in the first PLMN.

[0220] When the terminal device belonging to the second PLMN registers, the access management network element in the first PLMN has learned that the terminal device is a user accessing through indirect network sharing. When the terminal device belonging to the second PLMN requests to establish a session, the access management network element will map the identifier of the network slice in the second PLMN reported by the terminal device to the identifier of the network slice in the first PLMN.

[0221] For example, the identifier of the first network slice in the second PLMN includes: S-NSSAI#A, S-NSSAI#B; the identifier of the second network slice in the first PLMN includes: S-NSSAI#a, S-NSSAI#b; S-NSSAI#A has a mapping relationship with S-NSSAI#a, and S-NSSAI#B has a mapping relationship with S-NSSAI#b. The access management network element in the first PLMN is pre-configured with a mapping relationship between the identifier of the network slice in the first PLMN and the identifier of the network slice in the second PLMN. The access management network element can map the identifier of the first network slice in the second PLMN to the identifier of the second network slice in the first PLMN based on the mapping relationship. The mapping relationship can be a mapping relationship between the identifiers of the network slices in the first PLMN and the second PLMN that are allowed to be accessed and stored in the context of the terminal device; or, the mapping relationship is not stored in the context of the terminal device, for example, it is a mapping relationship between the identifiers of the network slices in the full amount of the first PLMN and the second PLMN.

[0222] In an optional example, the second message further includes at least one of the following: the first indication information, the session identifier in the NAS message of step 701, and the N1 SM container in the NAS message of step 701. The N1 SM container carries a session establishment request (PDU session establishment request).

[0223] Based on the registration process of the terminal device, the access management network element in the first PLMN knows that the terminal device belongs to the second PLMN. Therefore, the access management network element in the first PLMN can generate the first indication information by itself. The first indication information is used to indicate that the terminal device is a terminal device accessed through indirect network sharing. The first session management network element learns that the terminal device accesses through indirect network sharing based on the first indication information. Alternatively, the first session management network element can know that the terminal device is a terminal device accessed through indirect network sharing based on the identifiers of the network slices included in the second message, which are the identifiers of the network slices in the first PLMN and the identifiers of the network slices in the second PLMN. In this way, the second message does not need to include the first indication information.

[0224] Step 703: The first session management network element sends a third message to the access management function network element. Correspondingly, the access management network element receives the third message, and the third message includes: a session establishment response sent to the terminal device and an identifier of the second network slice in the first PLMN.

[0225] For example, the session establishment response is a successful establishment response. Optionally, the session establishment response includes an identifier of the first network slice in the second PLMN. The identifier of the first network slice in the second PLMN is used to send to the terminal device, and the identifier of the second network slice in the first PLMN is used to send to the access network device. For example, the third message includes: an N1 SM container and an N2 SM container; wherein, the N1 SM container is used to send to the terminal device, and the N1SM container includes the session establishment response; the N2 SM container is used to send to the access network device, and the N2 SM container includes the identifier of the second network slice in the first PLMN.

[0226] The first session management network element determines, based on the first indication information in the second message, that the identifier of the network slice sent to the terminal device is the identifier of the network slice in the second PLMN, and determines that the identifier of the network slice sent to the access network device is the identifier of the network slice in the first PLMN. Alternatively, even if the second message does not include the first indication information, the first session management network element may also determine, based on other methods (such as protocol provisions), that the identifier of the network slice sent to the terminal device is the identifier of the network slice in the second PLMN, and determine that the identifier of the network slice sent to the access network device is the identifier of the network slice in the first PLMN.

[0227] The identifier of the slice in the third message is determined by a network element in the second PLMN, for example, by a first session management network element (such as SMF) in the first PLMN, or a network slice selection network element (such as NSSF) in the first PLMN.

[0228] Step 704: The access management network element sends a fourth message to the access network device. Correspondingly, the access network device receives the fourth message. The fourth message includes: the session establishment response sent to the terminal device and the identifier of the second network slice in the first PLMN.

[0229] For example, the session establishment response is a successful establishment response. Optionally, the session establishment response includes an identifier of the first network slice in the second PLMN. The identifier of the first network slice in the second PLMN is used to send to the terminal device, and the identifier of the second network slice in the first PLMN is used to send to the access network device. For example, the fourth message includes: an N1 SM container and an N2 SM container; wherein, the N1 SM container is used to send to the terminal device, and the N1SM container includes the session establishment response; the N2 SM container is used to send to the access network device, and the N2 SM container includes the identifier of the second network slice in the first PLMN.

[0230] Step 705: The access network device sends the session establishment response in step 704 to the terminal device.

[0231] For example, the access network device sends an N1SM container to the terminal device, where the N1SM container includes a session establishment response.

[0232] In this embodiment, when a terminal device belonging to the second PLMN establishes a session based on a network element in the first PLMN, the terminal device sends an identifier of a network slice in the second PLMN to the network element in the first PLMN. Considering that the access network device is a device in the first PLMN, the network element in the first PLMN maps the identifier of the first network slice in the second PLMN from the terminal device to the identifier of the second network slice in the first PLMN and informs the access network device. This ensures that the access network device correctly identifies which network slice to use to serve the terminal.

[0233] In a possible example, after step 702, the first session management network element in the first PLMN can also determine the first user plane network element in the first PLMN serving the terminal device based on the identifier of the second network slice in the first PLMN.

[0234] In one possible example, after step 702, the first session management network element may further interact with a second session management network element in the second PLMN, and send the identifier of the first network slice in the second PLMN to the second session management network element in the second PLMN, so that the second session management network element establishes a session for the terminal device based on the identifier of the first network slice in the second PLMN. Exemplarily, after step 702 and before step 703, the following steps are performed:

[0235] The first session management network element sends a fifth message to the second session management network element. Correspondingly, the second session management network element receives the fifth message, where the fifth message includes: an identifier of the first network slice in the second PLMN.

[0236] The second session management network element sends a second session establishment response to the first session management network element. Correspondingly, the first session management network element receives the second session establishment response, where the second session establishment response is used to indicate that the session establishment is successful.

[0237] In one possible implementation, whether the session establishment indicated by the first session establishment response in step 703 is successful can be determined based on the second session establishment response. That is, if the second session establishment response indicates that the session establishment is successful, the first session establishment response also indicates that the session establishment is successful; if the second session establishment response indicates that the session establishment fails, the first session establishment response also indicates that the session establishment fails.

[0238] The first session management network element can determine the second session management network element itself. For example, the first session management network element determines the second session management network element based on the identifier of the first network slice in the second PLMN. Alternatively, the access management network element in the first PLMN determines the second session management network element. In this case, the second message in step 702 may also include information about the second session management network element. This information about the second session management network element is used by the first session management network element to locate the second session management network element. The information about the second session management network element may be the identifier of the second session management network element. For example, the access management network element selects the second session management network element in the second PLMN based on the identifier of the first network slice in the second PLMN.

[0239] In an optional example, the fifth message also includes: first indication information, where the first indication information is used to indicate that the terminal device is a terminal device accessed through indirect network sharing. The first indication information in the fifth message may come from the second message, or the second message does not include the first indication information. The first session management network element may learn that the terminal device is accessed through indirect network sharing based on the identifiers of the network slices included in the second message, which are the identifiers of the network slices in the first PLMN and the identifiers of the network slices in the second PLMN, and thus carry the first indication information in the fifth message.

[0240] In a possible example, the second session management network element in the second PLMN can also determine the second user plane network element in the second PLMN serving the terminal device based on the identifier of the first network slice in the second PLMN.

[0241] The fifth information can be carried in Nsmf_PDUSession_CreateSMContext Request.

[0242] The sixth information can be carried in Nsmf_PDUSession_CreateSMContext Response.

[0243] In conjunction with the example of FIG7 , taking the second PLMN as OP#2, the first PLMN as OP#1, the access management network element as AMF, and the session management network element as SMF as an example, as shown in FIG8 , a communication method is introduced, including the following steps:

[0244] Step 800a: The EPLMN ID of OP#2 is pre-configured in the AMF of OP#1, and the mapping relationship of the network slices (S-NSSAI) between OP#1 and OP#2 is also configured.

[0245] For example, the S-NSSAI values ​​of OP#1 include S-NSSAI#a, S-NSSAI#b, S-NSSAI#c, and S-NSSAI#d; the S-NSSA values ​​of OP#2 include S-NSSAI#A, S-NSSAI#B, S-NSSAI#C, and S-NSSAI#D. The mapping relationship is: S-NSSAI#a maps to S-NSSAI#A, S-NSSAI#b maps to S-NSSAI#B, S-NSSAI#c maps to S-NSSAI#C, and S-NSSAI#d maps to S-NSSAI#D.

[0246] As shown in Table 2, a mapping relationship of S-NSSAI between OP#1 and OP#2 is introduced. It can be understood that the mapping relationship can be expressed in the form of a table or in other forms.

[0247] Table 2: S-NSSAI mapping relationship between OP#1 and OP#2.

[0248] Step 800b: Registration process of OP#2's UE. Referring to the examples in Figures 4, 5 and 6, the AMF determines whether the UE is a user accessing through indirect network sharing based on the PLMN selected by the UE.

[0249] Step 801: The UE of OP#2 sends a NAS message, which includes: a session identifier, an identifier of the first network slice in OP#2 (e.g., OP#2 S-NSSAI value), and an N1 SM container. The N1 SM container carries a session establishment request (PDU session establishment request).

[0250] Step 802: AMF maps the identifier of the first network slice in OP#2 (OP#2 S-NSSAI value) to the identifier of the second network slice in OP#1 (OP#1 S-NSSAI value).

[0251] For example, AMF maps the identifier of the first network slice in OP#2 (OP#2S-NSSAI value) to the identifier of the second network slice in OP#1 (OP#1 S-NSSAI value) based on the mapping relationship between the identifier of the network slice in the first PLMN allowed to access and the identifier of the network slice in the second PLMN saved in the context of the UE (i.e., mapping of Allowed NSSAI).

[0252] In addition, AMF selects OP#1 SMF and OP#2 SMF to trigger the home routed session establishment process.

[0253] Step 803: AMF sends to OP#1 SMF: the identifier of the first network slice in OP#2 (OP#2 S-NSSAI value), the identifier of the second network slice in OP#1 (OP#1 S-NSSAI value, mapped in step 802), OP#2 SMF ID (also called H-SMF ID), first indication information, and N1 SM container. The first indication information is used to indicate that the UE is a user accessing through indirect network sharing. The N1 SM container carries a session establishment request (PDU session establishment request).

[0254] The information in step 803 may be carried in Nsmf_PDUSession_CreateSMContext Request.

[0255] Step 804: OP#1 SMF selects OP#1 UPF (which may be called V-UPF) based on the identifier of the first network slice in OP#1 (OP#1 S-NSSAI value).

[0256] Step 805: OP#1 SMF sends to OP#2 SMF: the identifier of the first network slice in OP#2 (OP#2 S-NSSAI value).

[0257] The information in step 805 may be carried in Nsmf_PDUSession_CreateSMContext Request.

[0258] The order of step 804 and step 805 is not limited.

[0259] Step 806: OP#2 SMF selects OP#2 UPF (which may be called H-UPF) based on the identifier of the first network slice in step 805 (OP#2 S-NSSAI value).

[0260] OP#2 SMF establishes a session for the UE based on the OP#2 S-NSSAI value in step 805. Optionally, OP#2 SMF may also request the OP#2 PCF to establish an SM Policy Association based on the OP#2 S-NSSAI value in step 805.

[0261] Step 807: OP#2 SMF sends a second session establishment response to OP#1 SMF, indicating that the session establishment is successful.

[0262] For example, the response of step 807 may be carried in Nsmf_PDUSession_CreateSMContext Response.

[0263] Step 808: OP#1 SMF determines based on the first indication in step 805 that the identifier of the network slice sent to the UE is the identifier of the network slice in OP#2, and the identifier of the network slice sent to the shared RAN is the identifier of the network slice in OP#1.

[0264] Step 809: OP#1 SMF sends to AMF: a first session establishment response for sending to the UE and an identifier of the second network slice in OP#1 for sending to the shared RAN.

[0265] The first session establishment response is determined based on the second session establishment response. The second session establishment response indicates that the session establishment is successful, and the first session establishment response also indicates that the session establishment is successful. The first session establishment response includes the identifier of the first network slice in OP#2. The information sent to the UE is carried in the N1 SM container, and the information sent to the shared RAN is carried in the N2 SM container. For example, OP#1 SMF sends to AMF: N1 SM container and N2 SM container, where the N1 SM container includes the first session establishment response and the N2 SM container includes the identifier of the second network slice in OP#1.

[0266] For example, the information in step 809 may be carried in Namf_Communication_N1N2MessageTransfer.

[0267] Step 810: AMF sends an N2 message to the shared RAN, where the N2 message includes: a session establishment response for sending to the UE and an identifier of the second network slice in OP#1 for sending to the shared RAN.

[0268] For example, the AMF sends an N2 message to the shared RAN, and the N2 message includes: an N1 SM container and an N2 SM container; wherein the N1 SM container includes a session establishment response, and the session establishment response includes the identifier of the first network slice in OP#2; the N2 SM container includes the identifier of the second network slice in OP#1.

[0269] The shared RAN saves the identifier of the second network slice in OP#1 in the N2 message in the context of the UE.

[0270] Step 811: The shared RAN sends a NAS message to the UE, and accordingly, the UE receives the NAS message; the NAS message includes: a session establishment response, and the session establishment response includes the identifier of the first network slice in OP#2.

[0271] For example, the shared RAN sends a NAS message to the UE, where the NAS message includes an N1 SM container, where the N1 SM container includes a session establishment response. The UE saves the identifier of the first network slice in OP#2 in the session establishment response.

[0272] It is understood that, to implement the functions in the above embodiments, the access management network element, the first session management network element, and the second session management network element include hardware structures and / or software modules corresponding to the respective functions. Those skilled in the art should readily appreciate that, in conjunction with the various exemplary units and method steps described in the embodiments disclosed herein, the present application can be implemented in the form of hardware or a combination of hardware and computer software. Whether a function is implemented in hardware or in a hardware-driven manner by computer software depends on the specific application scenario and design constraints of the technical solution.

[0273] Figures 9 and 10 are schematic diagrams of the structures of possible communication devices provided in the embodiments of the present application. These communication devices can be used to implement the functions of the access management network element, the first session management network element, and the second session management network element in the above method embodiments, and thus can also achieve the beneficial effects possessed by the above method embodiments. In the embodiments of the present application, the communication device can be the AMF in operator 1 as shown in Figure 2b, the SMF in operator 1 as shown in Figure 2b, the SMF in operator 2 as shown in Figure 2b, or a module (such as a chip) applied to the AMF or SMF.

[0274] As shown in FIG. 9 , the communication device 900 includes a processing unit 910 and a transceiver unit 920 .

[0275] For example, the communication device 900 is used to implement the functions of the access management network element in the first PLMN (also referred to as the AMF in OP#1), the first session management network element in the first PLMN (also referred to as the SMF in OP#1), and the second session management network element in the second PLMN (also referred to as the SMF in OP#2) in the method embodiments shown in Figures 3, 4, 5, 6, 7, and 8. The transceiver unit 920 can perform the receiving and sending actions performed by the access management network element, the first session management network element, and the second session management network element in the method embodiments. The processing unit 910 can perform other actions, except for the sending and receiving actions, among the actions performed by the access management network element, the first session management network element, and the second session management network element in the method embodiments.

[0276] Exemplarily, when the communication device 900 is used to implement the function of the access management network element in the method embodiment shown in FIG3 , the transceiver unit 920 is used to receive a first message and send a second message. The processing unit 910 is used to parse the first message and generate the second message. The processing unit is used to store the mapping relationship of the identifier of the network slice.

[0277] Exemplarily, when the communication device 900 is used to implement the function of the first session management network element in the method embodiment shown in Figure 7: the transceiver unit 920 is used to receive the second information and send the third message. The processing unit 910 is used to determine to parse the second message and generate the third message.

[0278] Exemplarily, when the communication device 900 is used to implement the function of the second session management network element (SMF in OP#2) in the method embodiment shown in FIG8 : the transceiver unit 920 is used to receive the identifier of the first network slice in OP#2 and send a second session establishment response. The processing unit 910 is used to select the UPF in OP#2 based on the identifier of the first network slice in OP#2.

[0279] A more detailed description of the processing unit 910 and the transceiver unit 920 can be directly obtained by referring to the relevant description of the method embodiments shown in Figures 3 to 8, and will not be repeated here. The processing unit 910 can be implemented by a processor, and the transceiver unit 920 can be implemented by a transceiver.

[0280] As shown in Figure 10, communication device 1000 includes a processor 1010 and an interface circuit 1020. Processor 1010 and interface circuit 1020 are coupled to each other. It is understood that interface circuit 1020 can be a transceiver or an input / output interface. Optionally, communication device 1000 may also include a memory 1030 for storing instructions executed by processor 1010, or storing input data required by processor 1010 to execute instructions, or storing data generated after processor 1010 executes instructions. Sometimes, interface circuit 1020 can also be understood as part of processor 1010, in which case communication device 1000 includes processor 1010.

[0281] When the communication device 1000 is used to implement the methods shown in FIG. 3 to FIG. 8 , the processor 1010 is used to implement the functions of the processing unit 910 , and the interface circuit 1020 is used to implement the functions of the transceiver unit 920 .

[0282] When the above-mentioned communication device is a chip applied to a terminal device, the terminal device chip implements the functions of the terminal device in the above-mentioned method embodiment. When the terminal device chip receives information from the network device, it can be understood that the information is first received by other modules in the terminal device (such as a radio frequency module or antenna) and then sent to the terminal device chip by these modules. When the terminal device chip sends information to the network device, it can be understood that the information is first sent to other modules in the terminal device (such as a radio frequency module or antenna) and then sent to the network device by these modules.

[0283] When the above-mentioned communication device is a chip applied to a network device, the network device chip implements the functions of the network device in the above-mentioned method embodiment. The network device chip receives information from the terminal device, which can be understood as the information being first received by other modules in the network device (such as a radio frequency module or antenna) and then sent to the network device chip by these modules. The network device chip sends information to the terminal device, which can be understood as the information being sent to other modules in the network device (such as a radio frequency module or antenna) and then sent to the terminal device by these modules. The network device module here can be a baseband chip of the network device, or it can be a DU or other module. The DU here can be a DU under the open radio access network O-RAN architecture.

[0284] In the present application, when entity A sends information to entity B, it can be that A sends it directly to B, or that A sends it to B indirectly through other entities. Similarly, when entity B receives information from entity A, it can be that entity B directly receives the information sent by entity A, or that entity B indirectly receives the information sent by entity A through other entities. Entities A and B here can be network devices or terminal devices, or modules within a network device or modules within a terminal device. The sending and receiving of information can be information interaction between a network device and a terminal device, or information interaction between two network devices, such as information interaction between a CU and a DU; the sending and receiving of information can also be information interaction between different modules within a device, such as information interaction between a terminal device chip and other modules of the terminal device, or information interaction between a network device chip and other modules in the network device.

[0285] It is understood that the processor in the embodiments of the present application may be a central processing unit (CPU), or may be other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field programmable gate arrays (FPGA), or other programmable logic devices, transistor logic devices, hardware components, or any combination thereof. The general-purpose processor may be a microprocessor or any conventional processor.

[0286] The present application also provides a computer-readable storage medium storing a computer program, which, when executed by a computer, enables the computer to perform the above-mentioned communication method. In other words, the computer program includes instructions for implementing the above-mentioned communication.

[0287] An embodiment of the present application further provides a computer program product, including: computer program code, which, when executed on a computer, enables the computer to execute the communication method provided above.

[0288] An embodiment of the present application further provides a communication system, which includes: an access management network element and a first session management network element in a first PLMN that executes the above-mentioned communication method.

[0289] The method steps in the embodiments of the present application can be implemented by hardware or by a processor executing software instructions. The software instructions can be composed of corresponding software modules, and the software modules can be stored in a random access memory, a flash memory, a read-only memory, a programmable read-only memory, an erasable programmable read-only memory, an electrically erasable programmable read-only memory, a register, a hard disk, a mobile hard disk, a compact disc read-only memory (CD-ROM) (also known as a read-only optical disc) or any other form of storage medium well known in the art. An exemplary storage medium is coupled to the processor so that the processor can read information from the storage medium and write information to the storage medium. Of course, the storage medium can also be an integral part of the processor. The processor and the storage medium can be located in an ASIC. In addition, the ASIC can be located in a base station or a terminal. Of course, the processor and the storage medium can also be present in a base station or a terminal as discrete components.

[0290] The above embodiments can be implemented in whole or in part using software, hardware, firmware, or any combination thereof. When implemented using software, they can be implemented in whole or in part in the form of a computer program product. The computer program product includes one or more computer programs or instructions. When the computer programs or instructions are loaded and executed on a computer, the processes or functions described in the embodiments of this application are performed in whole or in part. The computer can be a general-purpose computer, a special-purpose computer, a computer network, a network device, a first control plane network element, a user equipment, or other programmable device. The computer program or instructions can be stored in a computer-readable storage medium or transferred from one computer-readable storage medium to another. For example, the computer program or instructions can be transferred from one website, computer, server, or data center to another website, computer, server, or data center via wired or wireless means. The computer-readable storage medium can be any available medium accessible by a computer or a data storage device such as a server or data center that integrates one or more available media. The available medium can be a magnetic medium, such as a floppy disk, hard disk, or magnetic tape; an optical medium, such as a digital video disk; or a semiconductor medium, such as a solid-state drive. The computer-readable storage medium may be a volatile or nonvolatile storage medium, or may include both volatile and nonvolatile types of storage media.

[0291] In the various embodiments of the present application, unless otherwise specified or there is any logical conflict, the terms and / or descriptions between different embodiments are consistent and can be referenced by each other. The technical features in different embodiments can be combined to form new embodiments according to their inherent logical relationships.

[0292] In the embodiments of the present application, the number of nouns, unless otherwise specified, means "singular noun or plural noun", that is, "one or more". "At least one" means one or more, and "plural" means two or more. "And / or" describes the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone, where A or B can be singular or plural. The character " / " generally indicates that the previous and next associated objects are in an "or" relationship. For example, A / B means: A or B. "At least one of the following items" or "one or more of them" and other similar expressions refer to any combination of these items, including any combination of single items or plural items. For example, at least one of a, b, or c, or one or more of a, b, or c, means: a, b, c, a and b, a and c, b and c, or a and b and c. Each of a, b, and c can be single or multiple.

[0293] The ordinal numbers "first" and "second" mentioned in the embodiments of this application are used to distinguish multiple objects and are not used to limit the size, content, order, timing, priority, or importance of multiple objects. Moreover, such names do not indicate differences in the content, sender / receiver, transmission order, size, application scenario, priority, or importance of the two pieces of information. In addition, the numbering of the steps in the various embodiments introduced in this application is only for distinguishing different steps and is not used to define the order of the steps.

Claims

1. A communication method, characterized in that: The access management network element applied to the first public land mobile network PLMN includes: receiving a first message from an access network device, the first message including: a registration request of a terminal device belonging to a second PLMN, the registration request including: an identifier of a network slice in the second PLMN to which the terminal device requests access; and indirect network sharing exists between the second PLMN and the first PLMN; A second message is sent to the access network device, the second message including: an identifier of the network slice in the first PLMN that the terminal device is allowed to access and a registration response for sending to the terminal device; the registration response includes: an identifier of the network slice in the second PLMN that the terminal device is allowed to access; and an identifier of the network slice in the first PLMN that the terminal device is allowed to access is used to send to the access network device.

2. The method according to claim 1, wherein The registration response also includes: an identifier of the network slice in the second PLMN configured for the terminal device, and the identifier of the network slice in the second PLMN configured for the terminal device is determined based on the identifier of the network slice in the second PLMN to which the terminal device is subscribed.

3. The method according to claim 1 or 2, wherein: Also includes: At least one of the following items is saved in the context of the terminal device: a mapping relationship between an identifier of a network slice in the first PLMN that the terminal device is allowed to access and an identifier of a network slice in the second PLMN that the terminal device is allowed to access, and a mapping relationship between an identifier of a network slice in the first PLMN configured for the terminal device and an identifier of a network slice in the second PLMN configured for the terminal device.

4. The method according to any one of claims 1 to 3, wherein The first message further includes: an identifier of an equivalent PLMN of the second PLMN, The method further comprises: It is determined according to the identifier of the equivalent PLMN that the terminal device is a terminal device accessed through indirect network sharing.

5. The method according to any one of claims 1 to 4, characterized in that Also includes: Based on the existence of indirect network sharing between the second PLMN and the first PLMN, it is determined that: the identifier of the network slice allowed to be accessed by the terminal device sent to the terminal device is the identifier of the network slice in the second PLMN, and the identifier of the network slice allowed to be accessed by the terminal device sent to the access network device is the identifier of the network slice in the first PLMN.

6. The method according to any one of claims 1 to 5, wherein: Also includes: Determine one or more of the following; or obtain one or more of the following from a network slice selection function network element in the first PLMN: The identifier of the network slice in the first PLMN that the terminal device is allowed to access, the identifier of the network slice in the second PLMN that the terminal device is allowed to access, the mapping relationship between the identifier of the network slice in the first PLMN that the terminal device is allowed to access and the identifier of the network slice in the second PLMN that the terminal device is allowed to access, the identifier of the network slice in the first PLMN configured for the terminal device, the identifier of the network slice in the second PLMN configured for the terminal device, the mapping relationship between the identifier of the network slice in the first PLMN configured for the terminal device and the identifier of the network slice in the second PLMN configured for the terminal device.

7. The method according to claim 6, wherein The one or more items are determined based on the mapping relationship between the identifier of the network slice in the second PLMN and the identifier of the network slice in the first PLMN.

8. The method according to any one of claims 1 to 5, wherein: Also includes: Based on the mapping relationship between the identifier of the network slice in the second PLMN and the identifier of the network slice in the first PLMN, mapping the identifier of the network slice in the second PLMN that the terminal device requests to access to the identifier of the network slice in the first PLMN requested to access; Determining, based on the identifier of the network slice in the first PLMN to which access is requested, an identifier of the network slice in the first PLMN to which the terminal device is allowed to access; Based on the mapping relationship between the identifier of the network slice in the second PLMN and the identifier of the network slice in the first PLMN, the identifier of the network slice in the first PLMN that the terminal device is allowed to access is mapped to the identifier of the network slice in the second PLMN that the terminal device is allowed to access.

9. A communication method, characterized in that: The access management network element applied to the first public land mobile network PLMN includes: receiving a first message from a terminal device belonging to a second PLMN, where the first message is used to request establishment of a session, and the first message includes: an identifier of a first network slice in the second PLMN; association of the first network slice with the session requested to be established; and indirect network sharing between the second PLMN and the first PLMN; Sending a second message to a first session management network element in the first PLMN, where the second message includes: an identifier of a first network slice in the second PLMN and an identifier of a second network slice in the first PLMN, where there is a mapping relationship between the identifier of the first network slice and the identifier of the second network slice; receiving a third message from the first session management network element, the third message including: an identifier of a second network slice in the first PLMN; A fourth message is sent to the access network device serving the terminal device, where the fourth message includes: an identifier of the second network slice in the first PLMN and a first session establishment response for sending to the terminal device.

10. The method according to claim 9, wherein The third message further includes: an identifier of the first network slice in the second PLMN; The first session establishment response includes: an identifier of the first network slice in the second PLMN.

11. The method according to claim 9 or 10, wherein: The second message also includes: first indication information, where the first indication information is used to indicate that the terminal device is a terminal device accessed through indirect network sharing.

12. The method according to any one of claims 9 to 11, wherein: Also includes: Based on the mapping relationship between the identifier of the network slice in the second PLMN and the identifier of the network slice in the first PLMN, the identifier of the first network slice in the second PLMN is mapped to the identifier of the second network slice in the first PLMN.

13. The method according to any one of claims 9 to 12, wherein: The second message further includes: information about a second session management network element in the second PLMN, where the information about the second session management network element is used by the first session management network element to find the second session management network element.

14. A communication method, characterized in that: A first session management network element applied to a first public land mobile network PLMN includes: In a process in which a terminal device belonging to a second PLMN requests to establish a session, a second message is received from an access management function network element in the first PLMN, where the second message includes: an identifier of a first network slice in the first PLMN and an identifier of a second network slice in the second PLMN, a mapping relationship between the identifier of the first network slice and the identifier of the second network slice; the first network slice is associated with the session requested to be established; and indirect network sharing exists between the second PLMN and the first PLMN; A third message is sent to the access management function network element, where the third message includes: an identifier of the second network slice in the first PLMN for sending to the access network device and a first session establishment response for sending to the terminal device.

15. The method according to claim 14, wherein The first session establishment response includes: an identifier of the first network slice in the second PLMN.

16. The method according to claim 14 or 15, characterized in that The second message also includes: first indication information, where the first indication information is used to indicate that the terminal device is a terminal device accessed through indirect network sharing.

17. The method according to claim 16, wherein Also includes: Based on the first indication information, determine: sending the identifier of the network slice in the second PLMN to the terminal device, and sending the identifier of the network slice in the first PLMN to the access network device.

18. The method according to any one of claims 14 to 17, wherein: Also includes: Sending a fifth message to a second session management network element in the second PLMN, the fifth message including: an identifier of the first network slice in the second PLMN; A second session establishment response is received from the second session-associated network element; and the first session establishment response is determined based on the second session establishment response.

19. The method according to claim 18, wherein The second message further includes: information about a second session management network element in the second PLMN, where the information about the second session management network element is used by the first session management network element to find the second session management network element; or, The method further includes determining a second session management network element in the second PLMN.

20. The method according to any one of claims 14 to 19, wherein: Also includes: Based on the identifier of the second network slice in the first PLMN, determine the first user plane network element in the first PLMN serving the terminal device.

21. A communication device, characterized in that: The method comprises a module for executing the method according to any one of claims 1 to 20.

22. A communication device, characterized in that: comprising a processor coupled to a memory; The memory is used to store computer programs or instructions; The processor is configured to execute part or all of the computer programs or instructions in the memory, and when the part or all of the computer programs or instructions are executed, is configured to implement the method according to any one of claims 1 to 20.

23. A communication device, characterized in that: including processor and memory; The memory is used to store computer programs or instructions; The processor is configured to execute part or all of the computer programs or instructions in the memory, and when the part or all of the computer programs or instructions are executed, is configured to implement the method according to any one of claims 1 to 20.

24. A chip system, characterized in that: comprising a processor and an interface circuit, wherein the processor is coupled to the memory; The memory is used to store computer programs or instructions; The processor is configured to execute part or all of the computer programs or instructions in the memory, and when the part or all of the computer programs or instructions are executed, is configured to implement the method according to any one of claims 1 to 20.

25. A computer-readable storage medium, characterized in that The storage medium stores a computer program or instruction. When the computer program or instruction is executed by the communication device, the method according to any one of claims 1 to 20 is implemented.

26. A computer program product, characterized in that The computer program product comprises computer instructions, and when the computer instructions are executed on a computer, the method according to any one of claims 1 to 20 is implemented.

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