Session establishment method and device

Abstract

The invention provides a session establishment method and device, aims to reduce signaling overhead, and relates to the technical field of wireless communication. In the method, a first core network is located in a first PLMN, and a second core network is located in a second PLMN. Wherein the first core network receives a first session establishment request from the terminal device and basic information required for establishing a session in the second PLMN, the first session establishment request comprises first information, and the first information indicates that the session of the terminal device is established in the first PLMN and the second PLMN. And the first core network sends a second session establishment request and the basic information to a second core network, the second session establishment request comprising the first information, and establishes a session of the terminal device in the first PLMN. Based on the scheme, the terminal device can establish the session of the terminal device in the two PLMNs by sending the first session establishment request to the first core network, and the signaling overhead can be saved.

Description

Technical Field

[0001] The present application relates to the field of wireless communication technology, and in particular to a method and device for establishing a session. Background Art

[0002] At present, the related technology supports a multi-connection architecture in which a terminal device accesses a network through two or more connections through one subscription data. For example, a terminal device can select a visited public land mobile network (VPLMN) for roaming access when accessing a home public land mobile network (HPLMN).

[0003] To explain: VPLMN here does not refer to the "network where the UE subscription data is located", but in terms of geographical location, HPLMN and VPLMN can cover the location of the terminal device at the same time.

[0004] However, in the case of a multi-connection architecture, a certain degree of signaling waste may be caused when a terminal device establishes multiple sessions. Summary of the invention

[0005] In a first aspect, a session establishment method is provided. The method may be executed by a first core network, or by a chip / chip system in the first core network. In the method, the first core network is located in a first PLMN, the second core network is located in a second PLMN, and the first PLMN and the second PLMN are different. The first core network receives a first session establishment request from a terminal device and basic information required to establish a session in the second PLMN. Optionally, the basic information may be carried in the first session establishment request or may not be carried in the first session establishment request. It is understandable that the terminal device may send the first session establishment request and the basic information to the first core network through one message or two different messages. The first session establishment request includes first information, the first information indicates to establish a session of the terminal device in the first PLMN and the second PLMN, and the basic information is used by the second core network to establish a session of the terminal device in the second PLMN. The first core network sends a second session establishment request and basic information to the second core network, the second core network is located in the second PLMN, and the second session establishment request includes the first information. The first core network establishes a session of the terminal device in the first PLMN.

[0006] Based on this solution, the terminal device can establish a session of the terminal device in the first PLMN and the second PLMN by sending a first session establishment request to the first core network located in the first PLMN. Compared with the method in which the terminal device requests to establish a session to the two PLMNs separately in the related technology, signaling overhead can be saved.

[0007] In a possible implementation, the first PLMN is an HPLMN, the second PLMN is a VPLMN, the first core network includes a first access and mobility management function device, and the second core network includes a second access and mobility management function device. Based on this solution, the access and mobility management function device in the related technology can be enhanced, and through the communication between the first access and mobility management function device and the second access and mobility management function device, a session of a terminal device can be established in two PLMNs.

[0008] In a possible implementation, the first core network further includes a first session management function device and a first user plane function device, and the second core network further includes a second session management function device and a second user plane function device. The first access and mobility management function device receives a first session establishment request from a terminal device, and the first access and mobility management function device sends a second session establishment request to the second access and mobility management function device. In the method, the second session establishment request also includes information of the first session management function device, and the information of the first session management function device is used for the second session management function device to send a third session establishment request to the first session management function device, and the third session establishment request includes information of the second user plane function device and the first information, and the third session establishment request is used to request to establish a connection between the first user plane function device and the second user plane function device. It should be noted that in the above operation, the second session management function device can receive the first information from the second access and mobility management function device, so that the second session management function device can select a suitable second user plane function device to serve the terminal device, and send a third session establishment request carrying information of the second user plane function device and the first information to the first session management function device. The first session management function device receives the third session establishment request from the second session management function device, and sends the information of the second user plane function device to the first user plane function device, requesting the first user plane function device to establish a connection between the first user plane function device and the second user plane function device. The first user plane function device establishes a connection with the second user plane function device based on the information of the second user plane function device. The first user plane function device establishes a connection with the terminal device based on the first information.

[0009] Based on this solution, a session of a terminal device can be established in two PLMNs through communication between each network element in the first core network and each network element in the second core network.

[0010] In a possible implementation, the first user plane function device sends information of the first user plane function device and information of the second user plane function device to the first session management function device. Based on this solution, the user plane function device of the HPLMN can send information of the session of the terminal device established in the HPLMN and information of the session of the terminal device established in the VPLMN to the session management function device of the HPLMN, so that the session management function device of the HPLMN can manage the sessions of the two networks.

[0011] In a possible implementation, the first PLMN is a VPLMN, the second PLMN is an HPLMN, the first core network includes a first access and mobility management function device and a first session management function device, and the second core network includes a second session management function device. The first access and mobility management function device receives a first session establishment request. The first access and mobility management function device sends a fourth session establishment request to the first session management function device, and the fourth session establishment request includes first information. The first session management function device sends a second session establishment request to the second session management function device. The second session management function device sends the first information and the information of the first user plane function device to the second user plane function device, requesting the second user plane function device to establish a connection with the terminal device and requesting to establish a connection with the first user plane function device. The second user plane function device sends the information of the first user plane function device and the information of the second user plane function device to the second session management function device.

[0012] Based on this solution, by enhancing the session management function device in the related technology, the first session management function device can communicate with the second session management function device to establish a session of the terminal device in two PLMN sessions.

[0013] In one possible implementation, the first information includes one or more of indication information for instructing the terminal device to establish a session in the second PLMN, a session establishment request type, identification information of the second PLMN, a temporary identification of the terminal device in the second PLMN, and an identification of the second core network.

[0014] Based on this solution, the various possible first information mentioned above can be used to indicate to the first core network that a session of the terminal device is established in the HPLMN and in the VPLMN.

[0015] In a possible implementation, the first session establishment request also includes information about the second core network, or the information about the second core network is obtained from the context information of the terminal device. Based on this solution, the terminal device can send the information about the second core network to the first core network, or the first core network can obtain the information about the second core network from the context information of the terminal device, so that the first core network can determine the second core network located in the second PLMN.

[0016] In a second aspect, a session establishment method is provided. The method may be executed by a second core network, or by a chip / chip system in the second core network. In the method, the first core network is located in a first PLMN, the second core network is located in a second PLMN, and the first PLMN and the second PLMN are different. In the method, the second core network receives a second session establishment request from the first core network and basic information required to establish a session in the second PLMN. The second session establishment request includes first information, the first information indicates to establish a session of a terminal device in the first PLMN and the second PLMN, and the basic information is used by the second core network to establish a session of the terminal device in the second PLMN. The second core network establishes a session of the terminal device in the second PLMN.

[0017] In a possible implementation manner, the first PLMN is a HPLMN, the second PLMN is a VPLMN, the first core network includes a first access and mobility management function device, and the second core network includes a second access and mobility management function device.

[0018] In a possible implementation, the first core network further includes a first session management function device and a first user plane function device, and the second core network further includes a second session management function device and a second user plane function device. The second access and mobility management function device receives a second session establishment request from the first access and mobility management function device. The second session establishment request includes information of the first session management function device, and the second access and mobility management function device sends the first information and information of the first session management function device to the second session management function device. The second session management function device sends a third session establishment request to the first session management function device, the third session establishment request includes information of the second user plane function device and the first information, and the third session establishment request is used to request to establish a connection between the first user plane function device and the second user plane function device.

[0019] In a possible implementation, the second session management function device sends a fifth session establishment request to the second user plane function device, where the fifth session establishment request is used to request the second user plane function device to establish a connection with the terminal device. The second user plane function device establishes a connection with the terminal device.

[0020] In a possible implementation, the first core network includes a first session management function device, and the second core network includes a second session management function device. The second session management function device sends first information to the second user plane function device, requesting the second user plane function device to establish a connection with the terminal device. The second user plane function device establishes a connection with the terminal device.

[0021] In a possible implementation manner, the second user plane function device sends information about the first user plane function device and information about the second user plane function device to the second session management function device.

[0022] In one possible implementation, the first information includes one or more of indication information for instructing the terminal device to establish a session in the second PLMN, a session establishment request type, identification information of the second PLMN, a temporary identification of the terminal device in the second PLMN, and an identification of the second core network.

[0023] In a possible implementation manner, the first session establishment request also includes identification information of the second core network, or the information of the second core network is obtained from the context information of the terminal device.

[0024] Among them, the beneficial effects of various possible implementation methods of the second aspect can refer to the relevant description of the first aspect, and the repeated parts will not be repeated.

[0025] In a third aspect, a session establishment method is provided. The method may be executed by a first core network, or by a chip / chip system in the first core network. In the method, the first core network is located in a first PLMN, the second core network is located in a second PLMN, and the first PLMN and the second PLMN are different. The first core network receives a first session establishment request from a terminal device and basic information required to establish a session in the second PLMN. The first session establishment request includes first information, the first information indicates that a session of the terminal device is established in the first PLMN and the second PLMN, and the basic information is used by the second core network to establish a session of the terminal device in the second PLMN. The first core network sends a second session establishment request and basic information to the second core network, the second core network is located in the second PLMN, and the second session establishment request includes the first information. The first core network receives a first response message from the second core network, and the first response message indicates that the session establishment of the terminal device fails. The first core network sends a first response message to the terminal device.

[0026] Based on this solution, the terminal device can request to establish a session of the terminal device in two PLMNs by sending a first session establishment request to the first core network, which can save signaling overhead. In addition, in the case of a session establishment failure, the session establishment failure can be indicated to the terminal device.

[0027] In a possible implementation, the first PLMN is a HPLMN, the second PLMN is a VPLMN, the first core network includes a first access and mobility management function access and mobility management function device, and the second core network includes a second access and mobility management function device.

[0028] In a possible implementation, the first PLMN is an HPLMN, the second PLMN is a VPLMN, the first core network further includes a first session management function device and a first user plane function device, and the second core network further includes a second session management function device and a second user plane function device. The first access and mobility management function device receives a first session establishment request from a terminal device, and the first access and mobility management function device sends a second session establishment request to the second access and mobility management function device. In the method, the second session establishment request also includes information of the first session management function device, and the information of the first session management function device is used for the second session management function device to send a third session establishment request to the first session management function device, the third session establishment request includes information of the second user plane function device and the first information, and the third session establishment request is used to request to establish a connection between the first user plane function device and the second user plane function device. It should be noted that in the above operation, the second session management function device can receive the first information from the second access and mobility management function device, so that the second session management function device can select a suitable second user plane function device to serve the terminal device, and send a third session establishment request carrying information of the second user plane function device and the first information to the first session management function device. The first session management function device receives the third session establishment request from the second session management function device, and sends information of the second user plane function device to the first user plane function device, requesting the first user plane function device to establish a connection between the first user plane function device and the second user plane function device. The first user plane function device establishes a connection with the second user plane function device based on the information of the second user plane function device.

[0029] In a possible implementation, the first user plane function device sends a second response message to the first session management function device, and the second response message indicates that the session establishment of the terminal device in the first PLMN fails. The first session management function device sends a third response message to the second session management function device, and the third response message indicates that the session establishment of the terminal device in the first PLMN fails. The optional third response message is also used to indicate that the second session management function device does not establish a session of the terminal device in the second PLMN. The first access and mobility management function device receives the first response message from the second access and mobility management function device. The first access and mobility management function device sends the first response message to the terminal device.

[0030] Based on this solution, the first user plane function device can indicate to the first session management function device that the session establishment in the HPLMN has failed, thereby instructing the first session management function device to indicate to the second session management function device that the session establishment in the HPLMN has failed, and not to establish a session for the terminal device in the VPLMN, thereby reducing the charges generated by the terminal device obtaining services through the VPLMN.

[0031] In a possible implementation, the second response information includes the first indication information, and the first indication information indicates that the session establishment of the terminal device in the first PLMN fails, or the second response information does not include the information of the first user plane functional device. Based on this solution, the user plane functional device of the HPLMN can indicate the failure of the session establishment of the HPLMN by using the first indication information or not carrying the information of the first user plane functional device.

[0032] In a possible implementation, the first response information further indicates that the session establishment of the terminal device in the first PLMN fails. Based on this solution, the first core network may indicate to the terminal device that the session establishment in the HPLMN fails.

[0033] In a possible implementation, the first user plane function device sends a second response message to the first session management function device, and the second response message indicates that the session establishment of the terminal device in the first PLMN fails. The first session management function device sends a fourth response message to the second session management function device, and the fourth response message indicates that the session establishment of the terminal device in the second PLMN fails. The first access and mobility management function device receives the first response message from the second access and mobility management function device. The first access and mobility management function device sends the first response message to the terminal device. Based on this solution, the user plane function device of the HPLMN can indicate to the session management function device of the HPLMN that the session establishment in the VPLMN fails.

[0034] In a possible implementation, the second response information includes second indication information, and the second indication information indicates that the session establishment of the terminal device in the second PLMN fails, or the fourth response information does not include the information of the second user plane device. Based on this solution, the user plane function device of the HPLMN can indicate the failure of the session establishment of the VPLMN through the first indication information or without carrying the information of the second user plane device.

[0035] In a possible implementation, the first response information further indicates that the session establishment of the terminal device in the second PLMN fails. Based on this solution, the first core network may indicate to the terminal device that the session establishment in the VPLMN fails.

[0036] In a possible implementation, a session of the first terminal device is established in the first PLMN. Based on this solution, in the case that the session establishment in the VPLMN fails, a session of the terminal device can be established in the HPLMN.

[0037] In a fourth aspect, a session establishment method is provided. The method may be executed by a second core network, or by a chip / chip system in the second core network. In the method, the first core network is located in a first PLMN, the second core network is located in a second PLMN, and the first PLMN and the second PLMN are different. In the method, the second core network receives a second session establishment request from the first core network and basic information required to establish a session in the second PLMN, the first core network is located in a first PLMN different from the second PLMN, the second session establishment request includes first information, the first information indicates to establish a session of a terminal device in the first PLMN and the second PLMN, and the basic information is used by the second core network to establish a session of the terminal device in the second PLMN. The second core network sends a first response message to the first core network, and the first response message indicates that the session establishment of the terminal device has failed.

[0038] In a possible implementation, the first PLMN is a home public land network HPLMN, the second PLMN is a visited public land network VPLMN, the first core network includes a first access and mobility management function access and mobility management function device, and the second core network includes a second access and mobility management function device.

[0039] In a possible implementation, the first core network further includes a first session management function device and a first user plane function device, the second core network further includes a second session management function device and a second user plane function device, and the second access and mobility management function device receives a second session establishment request from the first access and mobility management function device. The second session establishment request includes information of the first session management function device, and the second access and mobility management function device sends the first information and information of the first session management function device to the second session management function device. The second session management function device sends a third session establishment request to the first session management function device, the third session establishment request includes information of the second user plane function device and the first information, and the third session establishment request is used to request to establish a connection between the first user plane function device and the second user plane function device.

[0040] In a possible implementation, the second session management function device receives third response information from the first session management function device, the third response information indicates that the session establishment of the terminal device in the first PLMN fails, and the third response information is also used for the second session management function device not to establish a session of the terminal device in the second PLMN. The second session management function device sends the third response information to the second access and mobility management function device. The second access and mobility management function device sends the first response information to the first access and mobility management function device.

[0041] In a possible implementation manner, the first response information further indicates that establishment of a session of the terminal device in the first PLMN fails.

[0042] In a possible implementation, the second session management function device receives fourth response information from the first session management function device, and the third response information further indicates that the session establishment of the terminal device in the second PLMN fails. The second session management function device sends the fourth response information to the second access and mobility management function device. The second access and mobility management function device sends the first response information to the first access and mobility management function device.

[0043] In a possible implementation manner, the second response information includes second indication information, where the second indication information indicates that establishment of a session of the terminal device in the second PLMN fails, or the fourth response information does not include information of the second user plane function device.

[0044] In a possible implementation manner, the first response information further indicates that establishment of a session of the terminal device in the second PLMN fails.

[0045] Among them, the beneficial effects of various possible implementation methods of the fourth aspect can be referred to the relevant description of the third aspect, and the repeated parts will not be repeated.

[0046] In a fifth aspect, the present application provides a session establishment method. The method can be executed by a terminal device, or by a chip / chip system in the terminal device. In the method, the first core network is located in a first PLMN, the second core network is located in a second PLMN, and the first PLMN and the second PLMN are different. The terminal device sends a first session establishment request and basic information required to establish a session in the second PLMN to the first core network. Among them, the first session establishment request includes first information, the first information indicates to establish a session of the terminal device in the first PLMN and the second PLMN, and the basic information is used by the second core network to establish a session of the terminal device in the second PLMN. In the method, the terminal device can obtain basic information after accessing the network. For example, the terminal device can use two 3GPP connections to access two different networks, such as the first PLMN and the second PLMN to obtain services through one subscription data, so that the terminal device can obtain the basic information required to establish a session in the second PLMN after accessing the network. Optionally, in the method, when the terminal device determines that it is currently in a dual-connection state, it can carry the first information in the first session request, that is, the terminal device can request to establish a session of the terminal device in the first PLMN and the second PLMN through the first session request.

[0047] In a possible implementation manner, the first core network includes a first access and mobility management function device.

[0048] In a possible implementation manner, the first PLMN is a HPLMN, and the second PLMN is a VPLMN.

[0049] In one possible implementation, the first information includes one or more of indication information for instructing the terminal device to establish a session in the second PLMN, a session establishment request type, identification information of the second PLMN, a temporary identification of the terminal device in the second PLMN, and an identification of the second core network.

[0050] In one possible implementation, the first session establishment request also includes information of the second core network, and the information of the second core network is used by the first core network to send the second session establishment request and basic information to the second core network. The second core network is located in the second PLMN, and the second session establishment request includes the first information.

[0051] In a possible implementation, the terminal device receives first response information from the first core network, and the first response information indicates that establishment of a session of the terminal device has failed.

[0052] In a possible implementation, the terminal device receives fifth response information from the first core network, and the fifth response information indicates that a session of the terminal device is successfully established in the first PLMN, and a session of the terminal device is successfully established in the second PLMN.

[0053] In a possible implementation, the first response information also indicates that a session with the terminal device in the first PLMN has failed to be established. It is understandable that, in the implementation, since a session with the terminal device in the first PLMN has failed to be established, a session with the terminal device in the second PLMN will not fail to be established. In this case, the terminal device cannot obtain services through the first PLMN and the second PLMN. Optionally, the terminal device may re-register or re-initiate the session establishment process and send a first session establishment request to the first core network. Based on this solution, the first core network may indicate to the terminal device that a session has failed to be established in the HPLMN.

[0054] In a possible implementation, the first response information also indicates that the session establishment of the terminal device in the second PLMN fails. It can be understood that in this implementation, the session establishment of the terminal device in the second PLMN fails, but the first core network can establish a session of the terminal device in the first PLMN, so the terminal device can obtain services through the session established in the first PLMN, such as sending data to the first core network and / or receiving data from the first core network. Based on this solution, the first core network can indicate to the terminal device that the session establishment in the VPLMN fails.

[0055] In a sixth aspect, the present application provides a communication system, which may include a first core network that executes the method described in the first aspect and a second core network that executes the method described in the second aspect. Alternatively, the communication system may include a first core network that executes the method described in the third aspect and a second core network that executes the method described in the fourth aspect. Optionally, the communication system also includes a terminal device that executes the method described in the fifth aspect.

[0056] In the seventh aspect, the present application provides a computer-readable storage medium, in which computer-readable instructions are stored. When a computer reads and executes the computer-readable instructions, the computer executes a method in any possible implementation of any one of the first to fifth aspects above.

[0057] In an eighth aspect, the present application provides a computer program product. When a computer reads and executes the computer program product, the computer executes a method in any possible implementation of any one of the first to fifth aspects above.

[0058] In a ninth aspect, the present application provides a chip, wherein the chip is used to read a computer program stored in a memory to execute a method in any possible implementation of any one of the first to fifth aspects above.

[0059] The technical effects that can be achieved in any of the fifth to ninth aspects mentioned above can refer to the description of the technical effects that can be achieved in any possible implementation method of any of the first to fourth aspects mentioned above, and the repetitions will not be discussed here. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] Figure 1 A schematic diagram of a communication system provided in an embodiment of the present application;

[0061] Figure 2A A schematic diagram of a dual connection architecture provided in an embodiment of the present application;

[0062] Figure 2B A schematic diagram of a network architecture for a terminal device to access HPLMN and VPLMN to obtain services provided in an embodiment of the present application;

[0063] Figure 3 A schematic diagram of an architecture for using two 3GPPs to access different networks provided in an embodiment of the present application;

[0064] Figure 4 A schematic diagram of a UE registration process provided in an embodiment of the present application;

[0065] Figure 5 A schematic diagram of a process for establishing a UE session in the HPLMN provided in an embodiment of the present application;

[0066] Figure 6 A schematic diagram of a process for establishing a UE session in a VPLMN provided in an embodiment of the present application;

[0067] Figure 7 An exemplary flow chart of a session establishment method provided in an embodiment of the present application;

[0068] Figure 8 An exemplary flow chart of another session establishment method provided in an embodiment of the present application;

[0069] Fig. 9 An exemplary flow chart of another session establishment method provided in an embodiment of the present application;

[0070] Fig.10 An exemplary flow chart of another session establishment method provided in an embodiment of the present application;

[0071] Fig.11 An exemplary flow chart of another session establishment method provided in an embodiment of the present application;

[0072] Fig.12 An exemplary flow chart of another session establishment method provided in an embodiment of the present application;

[0073] Fig.13 An exemplary flow chart of another session establishment method provided in an embodiment of the present application;

[0074] Fig.14 An exemplary flow chart of another session establishment method provided in an embodiment of the present application;

[0075] Fig.15 An exemplary flow chart of another session establishment method provided in an embodiment of the present application;

[0076] Fig.16 An exemplary flow chart of another session establishment method provided in an embodiment of the present application;

[0077] Fig.17 A schematic diagram of a communication device provided in an embodiment of the present application;

[0078] Fig.18 A schematic diagram of another communication device provided in an embodiment of the present application;

[0079] Fig.19 A schematic diagram of another communication device provided in an embodiment of the present application;

[0080] Fig. 20 A schematic diagram of another communication device provided in an embodiment of the present application. DETAILED DESCRIPTION

[0081] The following introduces the architecture of the communication system to which the method provided in this application is applied.

[0082] The technical solutions of the embodiments of the present application can be applied to New Radio (NR) systems, Long Term Evolution (LTE) systems, LTE frequency division duplex (FDD) systems, LTE time division duplex (TDD) systems, Worldwide Interoperability for Microwave Access (WiMAX) communication systems, and next-generation wireless communication systems such as 6G, etc., without limitation herein.

[0083] Figure 1 The figure shows an architecture diagram of a communication system applicable to the embodiment of the present application, wherein the fifth generation (5G) network architecture based on the service-oriented architecture is shown. Figure 1 As shown, the communication system may include three parts, namely, a terminal part, an operator network part and a data network (DN). The functions of some network elements are described below.

[0084] A terminal, also known as a terminal device or user equipment (UE), is a device with wireless transceiver capabilities that can be deployed on land, including indoors or outdoors, handheld or vehicle-mounted; it can also be deployed on the water (such as ships); it can also be deployed in the air (such as airplanes, balloons, and satellites). A terminal can be a mobile phone, a tablet computer (pad), a computer with wireless transceiver capabilities, a virtual reality (VR) terminal, an augmented reality (AR) terminal, a wireless terminal in industrial control, a wireless terminal in self-driving, a wireless terminal in remote medical, a wireless terminal in smart grid, a wireless terminal in transportation safety, a wireless terminal in smart city, a wireless terminal in smart home, etc.

[0085] The above-mentioned terminal can establish a connection with the operator network through the interface provided by the operator network (such as N1, etc.), and use the data and / or voice services provided by the operator network. The terminal can also access the DN through the operator network, use the operator services deployed on the DN, and / or services provided by a third party. Among them, the above-mentioned third party may be a service provider other than the operator network and the terminal, and can provide data and / or voice services to the terminal. Among them, the specific form of expression of the above-mentioned third party can be determined according to the actual application scenario, and is not limited here.

[0086] The operator network may be a network deployed by an operator, and may include access network equipment and core network equipment. In a possible implementation method, the operator network also includes an AF network element. Alternatively, the AF network element may not belong to the operator network, but to a third party.

[0087] Access network equipment is equipment in a wireless network, such as a radio access network (RAN) node or a radio access network device that connects a terminal to a wireless network. At present, some examples of access network equipment include: next-generation base stations (gNodeB, gNB) in 5G, transmission reception points (TRP), evolved Node B (eNB), radio network controller (RNC), Node B (NB), base station controller (BSC), base transceiver station (BTS), home base station (e.g., home evolved NodeB, or home Node B, HNB), base band unit (BBU), wireless fidelity (Wifi) access point (AP), integrated access and backhaul (IAB), etc. In one implementation, the access network equipment may also be an access network equipment in a future communication system (e.g., the 6th generation (6G) communication system).

[0088] The core network device may include at least one of the following network elements: a mobility management network element, a session management network element, a user plane network element (e.g., a user plane function (UPF) network element, a data management network element (e.g., a unified data management (UDM) network element), a unified database (UDR) network element, a network exposure network element (e.g., a network exposure function (NEF) network element), a policy control network element (e.g., a policy control function (PCF) network element), or an authentication function network element (e.g., an authentication server function (AUSF) network element), etc. Some of the network elements are described below.

[0089] In this application, the access and mobility management function (AMF) network element, or the access and mobility management function device, is a control plane network element provided by the operator network, which is responsible for the access control and mobility management of the terminal accessing the operator network, and can be used to implement other functions of the mobility management entity (MME) except session management, such as legal monitoring, or access authorization (or authentication), user equipment registration, mobility management, tracking area update process, reachability detection, selection of session management network element, mobile state transition management and other functions. In 5G, the mobility management network element can be an access and mobility management function network element. In future communications such as 6G, the mobility management network element can still be AMF, or have other names, which are not limited in this application. The following takes AMF as an example for explanation.

[0090] In this application, the session management function (SMF) network element or the session management function device is a control plane network element provided by the operator network, which is responsible for managing the protocol data unit (PDU) session of the terminal. The PDU session is a channel for transmitting PDUs, and the terminal needs to transmit PDUs to each other with the DN through the PDU session. The PDU session is established, maintained and deleted by the SMF network element. The functions of the session management network element include: session management (such as session establishment, modification and release, including tunnel maintenance between user plane network elements and access network devices), selection and control of user plane network elements, service and session continuity (SSC) mode selection, roaming, etc. In 5G, the session management network element can be a session management function network element. In future communications such as 6G, the session management network element can still be an SMF, or a network element with other names but with all or part of the functions of the session management network element, which is not limited in this application. The following takes SMF as an example for explanation.

[0091] In this application, the user plane function network element or user plane function device is a user plane network element provided by the operator, which is responsible for packet routing forwarding, policy implementation, traffic reporting, and quality of service (QoS) processing. In 5G, the user plane function network element can be a user plane function network element. In future communications such as 6G, the user plane function network element can still be a UPF, or a network element with other names but with all or part of the functions of a session management network element, which is not limited in this application. The following is an example of UPF.

[0092] In the embodiments of the present application, the communication device for realizing the function of the access network device, terminal or core network device may be the access network device, terminal or core network device itself, or may be a device capable of supporting the access network device, terminal or core network device to realize the function, such as a chip system, which may be installed in the access network device, terminal or core network device. In the technical solution provided in the embodiments of the present application, the technical solution provided in the embodiments of the present application is described by taking the device for realizing the function of the access network device as the access network device, the device for realizing the function of the terminal as the terminal, and the device for realizing the function of the core network device as the core network device as an example.

[0093] DN is a network outside the operator network. The operator network can access multiple DNs. Multiple services can be deployed on DN, which can provide data and / or voice services to terminals. For example, DN is the private network of a smart factory. The sensors installed in the workshop of the smart factory can be terminals. The control server of the sensors is deployed in DN, and the control server can provide services for the sensors. The sensors can communicate with the control server, obtain instructions from the control server, and transmit the collected sensor data to the control server according to the instructions. For another example, DN is the internal office network of a company. The mobile phones or computers of the company's employees can be terminals. The employees' mobile phones or computers can access information, data resources, etc. on the company's internal office network.

[0094] Figure 1 N1, N2, N3 and N4 are interface serial numbers. The meanings of these interface serial numbers can be found in the meanings defined in the 3rd Generation Partnership Project (3GPP) standard protocol, and are not limited here.

[0095] Figure 2A An exemplary dual steer architecture that may be applicable to the embodiments of the present application is provided. Under this architecture, when a terminal device accesses the HPLMN through a subscription data, it can additionally select a VPLMN roaming access, thereby realizing a multi-connection architecture that simultaneously accesses different networks through two 3GPP connections.

[0096] The access traffic steering, switching, splitting (ATSSS) feature is defined in the related technology. The UE can access the network to obtain services through a 3GPP connection and a non-3GPP connection. Among them, when the UE is not in the coverage of the HPLMN, but in the coverage of the VPLMN, it can access the VPLMN through 3GPP and access the HPLMN through non-3GPP at the same time. Among them, "simultaneously" can be understood as supporting both access to the VPLMN through 3GPP and access to the HPLMN through non-3GPP. After the UE accesses the network through two different access types, the UE can establish a multiple access (MA) PDU session to obtain services. When the UE accesses a PLMN through a 3GPP network and a non-3GPP network, since 3GPP and non-3GPP will select the same AMF to obtain services, the UE can establish an MA PDU session in both the 3GPP network and the non-3GPP network by sending a session establishment request. When a UE accesses different PLMNs through two different networks at the same time, such as HPLMN and VPLMN, the UE needs to initiate session establishment procedures in HPLMN and VPLMN respectively when establishing an MA PDU session. Figure 2B As shown, the sessions established for the HPLMN and the VPLMN use the same PDU session identifier (Session ID), indicating that they are the same session.

[0097] The anchor point of the MA PDU session is at the UPF, and the access network equipment sends specific rules to determine how to divert the traffic of the MA PDU session. When the UE accesses two different PLMNs, the anchor point of the session is at the UPF of the HPLMN, so the session of the VPLMN needs to be a home routed (HR) architecture. In the HR architecture, the user plane service flows back to the home UPF, that is, the UPF of the HPLMN, and accesses the DN.

[0098] In the embodiment of the present application, the UE supports dual connection or the dual connection state of the UE can be understood as the terminal device supports dual (or multiple) connection capabilities. For example, support the same access network (such as same access network), support dual (or multiple) wireless capabilities (such as dual / multiple radio capability), support dual (or multiple) 3GPP access technology (such as dual / multiple 3GPP RAT), support dual (or multiple) shunting capabilities (such as dual / multiple steer), support dual (or multiple) access (such as dual / multiple 3GPP), support dual (or multiple) 3GPP access types (such as dual / multiple3GPP access type), support dual (or multiple) registration (such as dual / multiple registration), support the same access type (such as same access type) or support the same access technology (such as same RAT).

[0099] In dual connectivity, there is a scenario where the UE uses two 3GPP connections to access two different networks to obtain services through one subscription data. However, due to the different deployment of base stations between the two networks, one of the networks may even use satellite access, which will lead to the Tracking Area (TA) between different networks being inconsistent. There may be a problem of inconsistent mobility restrictions between the two networks. Therefore, an architecture that can collaborate between AMFs is proposed. The architecture is as follows: Figure 3 shown.

[0100] When the UE registers with the VPLMN, it carries the dual connectivity indication information and the globally unique AMF identifier (globallyunique AMF identifier, GUAMI) / fifth generation mobile communication system (5 th generation, 5G)-globally unique temporary UE identifier (globally unique temporary identifier, GUTI), AMF2 finds AMF1 based on these messages and establishes a connection. AMF1 and AMF2 interact through this interface when performing mobility management to ensure that the two networks have unified UE mobility management. Through this architecture, the AMFs of the two PLMNs can interact with each other.

[0101] Below, through Figure 4 The following are the steps to introduce the UE registration process.

[0102] S1: UE sends a registration request message to RAN.

[0103] The registration request message carries the registration type (Registration Type) and the identification information of the UE, such as the subscription concealed identifier (SUCI), 5G-GUTI or permanent equipment identifier (PEI). The registration types are as follows:

[0104] 1) Initial Registration: The registration process initiated when the UE is in the deregistered state;

[0105] 2) Mobility Registration Update: A registration process that needs to be initiated when the UE moves;

[0106] 3) Periodic Registration Update: When the UE is in the registered state, the registration process is initiated due to the expiration of the periodic registration update timer;

[0107] S2: RAN selects the target AMF.

[0108] For example, RAN can select an appropriate AMF based on AMF load information or UE service requirements. Figure 4 The target AMF shown in the figure provides services for the UE.

[0109] S3: RAN sends the registration request message sent by the UE to the selected target AMF.

[0110] Optionally, when the UE initiates registration due to AMF change, such as when the UE moves out of the current AMF service range and initiates mobility registration update, Figure 4 The illustrated embodiment also includes S4.

[0111] S4: The target AMF requests the original AMF for UE context.

[0112] Among them, the target AMF can find the original AMF based on the 5G-GUTI information provided by the UE, and request UE context information from the original AMF.

[0113] S5: The target AMF selects an authentication server function (AUSF) to perform security processes such as authentication.

[0114] S6: UE, target AMF, AUSF, and UDM interact to complete security processes such as authentication. The implementation of specific security processes can refer to existing protocols.

[0115] S7: After the UE and the core network have successfully authenticated each other, the AMF interacts with the UDM to obtain the UE's subscription data.

[0116] Optionally, when the UE changes the AMF, Figure 4 The illustrated embodiment may also include S8 and S9.

[0117] S8: UDM sends a deregistration notification to the original AMF.

[0118] For example, after UDM receives the registration request sent by the target AMF, it sends a deregistration notification to the original AMF.

[0119] S9: After receiving the deregistration notification, the original AMF initiates the deregistration process to the UDM.

[0120] S10: The target AMF sends an N2 message to the RAN.

[0121] The N2 message may include a non-access stratum (NAS) message that needs to be forwarded by the RAN to the UE. The NAS message includes a registration acceptance message sent by the target AMF to the UE.

[0122] S11: RAN forwards the NAS message sent by AMF to UE.

[0123] based on Figure 4 The UE can register with the core network. After the UE successfully registers, a PDU session can be established. In the dual-connection scenario, the UE needs to request to establish a PDU session with the HPLMN and VPLMN respectively. Figure 5 and Figure 6 This section describes the UE PDU session establishment process.

[0124] See also Figure 5 A flow chart of a UE requesting the HPLMN to establish a session is shown, which may include the following steps.

[0125] S501: UE sends a session establishment request to AMF.

[0126] If the UE wants to establish an MA PDU session, the request type (requesttype) of the session establishment request is MA PDU request (request).

[0127] S502: AMF selects a suitable SMF to serve the UE.

[0128] S503: AMF sends a session establishment request to SMF.

[0129] Among them, if there is no association between AMF and SMF regarding the PDU session identifier (Session ID), the request type indication of the session establishment request is "initial request", and AMF sends a PDU session creation message (Nsmf_PDUSession_CreateSMContext); if there is already an association between AMF and SMF regarding the PDU session identifier (SessionID), the request type indication of the session establishment request is "existing PDU session", and AMF sends a PDU session update message (Nsmf_PDUSession_UpdateSMContext).

[0130] S504: SMF sends a response message to AMF.

[0131] Among them, SMF sends a response message to AMF according to the session establishment request of AMF in S503.

[0132] S505: SMF selects a suitable UPF to serve the UE.

[0133] S506: If AMF indicates an initial request to SMF in S503, then SMF sends an N4 session establishment request to UPF. If AMF indicates an "existing PDU session" to SMF in S503, that is, a request to modify an existing session, then SMF sends an N4 session modification request to UPF.

[0134] S507: UPF sends response information to SMF.

[0135] Among them, UPF sends response information to SMF according to the request in S506.

[0136] S508: SMF sends a request message to AMF, requesting AMF to send an N1 message or an N2 message.

[0137] S509: AMF sends an N2 session establishment request to RAN.

[0138] S510: RAN configures access network (AN) resources to UE, including PDU session request reception information.

[0139] S511: RAN feeds back N2 session establishment response information to AMF.

[0140] After RAN configures AN resources for UE, AN tunnel information may be carried in N2 session establishment response information.

[0141] At this point, the uplink establishment is complete and the UE can send uplink data streams to the UPF.

[0142] S512: AMF sends a session update request to SMF and sends the AN tunnel information received from RAN to SMF.

[0143] S513: SMF sends an N4 session modification request to UPF.

[0144] S514: UPF sends an N4 session modification response to SMF.

[0145] At this point, the downlink establishment is complete and the UPF can send downlink data streams to the UE.

[0146] S515: SMF updates the session context to AMF.

[0147] Figure 5 In the example shown, AMF, UPF and SMF can be H-AMF, H-UPF and H-SMF, that is, these core network elements are located in the HPLMN.

[0148] See also Figure 6 A process of a UE requesting a VPLMN to establish a session is shown, which may include the following steps.

[0149] S601: UE sends a session establishment request to V-AMF.

[0150] If the UE wants to establish an MA PDU session, the request type (requesttype) of the session establishment request is MA PDU request (request).

[0151] S602: V-AMF selects a suitable SMF to serve the UE.

[0152] Among them, under the HR architecture, V-AMF needs to select H-SMF and V-SMF at the same time.

[0153] S603: V-AMF sends a session establishment request to V-SMF.

[0154] Among them, if there is no association between V-AMF and V-SMF regarding the PDU session identifier (Session ID), the request type of the session establishment request is indicated as "initial request", and V-AMF sends a session creation message (Nsmf_PDUSession_CreateSMContext). If there is already an association between V-AMF and V-SMF regarding the PDU session identifier (Session ID), the request type of the session establishment request is indicated as "existing PDU session", and V-AMF sends a PDU session update message (Nsmf_PDUSession_UpdateSMContext).

[0155] Among them, under the HR architecture, V-AMF also needs to send H-SMF information to V-SMF.

[0156] S604: V-SMF sends a response message to V-AMF.

[0157] Among them, V-SMF sends a response message to V-AMF according to the session establishment request in S603.

[0158] S605: The V-SMF selects a suitable V-UPF to serve the UE.

[0159] S606: If V-AMF indicates an initial request to V-SMF in S603, then V-SMF sends an N4 session establishment request to V-UPF. If V-AMF requests V-SMF to modify an existing session in S603, then V-SMF sends an N4 session modification request to V-UPF.

[0160] S607: V-UPF sends a response message to V-SMF.

[0161] Among them, the V-UPF sends a response message to the V-SMF according to the request in S606.

[0162] S608: The V-SMF sends a session establishment request to the H-SMF, and sends V-UPF information to the H-SMF to establish a connection between the H-UPF and the V-UPF.

[0163] S609: The H-SMF selects a suitable H-UPF to serve the UE.

[0164] S610: H-SMF sends an N4 session establishment request to H-UPF.

[0165] The N4 session establishment request includes V-UPF information, which is used to establish a connection between the H-UPF and the V-UPF.

[0166] S611: H-UPF sends a response message to H-SMF.

[0167] The H-UPF sends a response message to the H-SMF according to the session establishment request in S610.

[0168] After this step is completed, it can be considered that the path from H-UPF to V-UPF is established, and H-UPF can send downlink data to V-UPF.

[0169] S612: H-SMF sends a response message to V-SMF according to the session establishment request in S608, and the response message includes H-UPF information.

[0170] S613: V-SMF sends an N4 session modification request to V-UPF, including H-UPF information, to establish an uplink from V-UPF to H-UPF.

[0171] S614: V-UPF sends a response message to V-SMF according to the N4 session modification request in S613.

[0172] S615: V-SMF sends a request message to V-AMF, requesting AMF to send an N1 message or an N2 message.

[0173] S616: V-AMF sends an N2 session establishment request to RAN.

[0174] S617: RAN configures AN resources to the UE, including PDU session request reception information.

[0175] S618: RAN feeds back N2 session establishment response information to V-AMF.

[0176] At this point, the uplink establishment is complete and the UE can send uplink data streams to the UPF.

[0177] S619: V-AMF sends a session update request to V-SMF and sends the N2 SM information received from RAN to SMF.

[0178] S620: V-SMF sends an N4 session modification request to V-UPF.

[0179] S621: V-UPF sends N4 session modification response to H-VSMF

[0180] At this point, the downlink establishment is complete and the UPF can send downlink data streams to the UE.

[0181] S622: V-SMF updates the session context to V-AMF.

[0182] pass Figure 5 and Figure 6 It can be seen that when the UE accesses two different networks at the same time, when establishing an MA PDU session to obtain services, it needs to initiate a session establishment process to the two networks respectively, which will cause a certain amount of signaling waste.

[0183] In view of this, an embodiment of the present application provides a session establishment method. In the method, a first core network located in a first PLMN can receive a first session establishment request from a terminal device. The first session establishment request may include first information and basic information required to establish a session in a second PLMN. The first information may indicate that a session of the terminal device is established in the first PLMN and the second PLMN. The first core network can establish a session of the terminal device in the first PLMN, and send a second session establishment request and basic information to a second core network located in the second PLMN. The second session establishment request may include the above-mentioned first information. In this way, the second PLMN can determine that a session of the terminal device needs to be established in the second PLMN based on the first information, and establish a session for the terminal device in the second PLMN according to the basic information.

[0184] Based on this solution, the terminal device can establish a session of the terminal device in two PLMNs by sending a first session establishment request to the first core network. Compared with the method in which the terminal device requests to establish a session to two PLMNs separately in the related art, signaling overhead can be saved.

[0185] See also Figure 7 , which is an exemplary flowchart of a session establishment method provided in an embodiment of the present application, may include the following steps.

[0186] S701: The terminal device sends a first session establishment request to the first core network.

[0187] Correspondingly, the first core network receives a first session establishment request from the terminal device.

[0188] The first core network is located in the first PLMN. The first session establishment request may include first information, and the first information may indicate to establish a session of the terminal device in the first PLMN and the second PLMN.

[0189] It is understandable that when the terminal device is registered with two different networks at the same time, it can be determined that it is currently in a dual connection state. At this time, the terminal device can request to establish a session of the terminal device in the first PLMN and the second PLMN through the first session establishment request in S701.

[0190] In one possible scenario, the first session establishment request may be a PDU session establishment request (PDU session establishment request). Optionally, the first session establishment request may include a request type, and the request type may be a multipath session request (request). It is understandable that a multipath session may be a session established by two or more 3GPP access networks. The request type may also be a multipath session request (request), such as a MAPDU session request. It is understandable that the MAPDU session here supports sessions established by two or more 3GPP access networks. The specific name of the request type is not limited in the embodiments of the present application. The request type is used to indicate that the session established by the UE is a session established through two or more 3GPP access networks.

[0191] In a possible implementation, the first information may be newly added indication information in the first session establishment request, and the indication information may indicate that a session needs to be established in the second PLMN, or may indicate that a session needs to be established between the first PLMN and the second PLMN. For example, the indication information may be 1-bit indication information. When the value of the indication information is 1, it may indicate that a session needs to be established in the second PLMN, or may indicate that a session needs to be established between the first PLMN and the second PLMN. When the value of the indication information is 0, it may indicate that a session does not need to be established in the second PLMN, or may indicate that a session needs to be established in the first PLMN. Conversely, when the value of the indication information is 0, it may indicate that a session needs to be established in the second PLMN, or may indicate that a session needs to be established between the first PLMN and the second PLMN. When the value of the indication information is 1, it may indicate that a session does not need to be established in the second PLMN, or may indicate that a session needs to be established in the first PLMN.

[0192] In another possible implementation, the first information may be a session establishment request type in the first session establishment request. For example, when the session establishment request type is a multipath session request, the first core network may determine the context information of the terminal device, and if the terminal device is in a dual-connection state and is registered with two different PLMNs at the same time, the first core network considers that a session needs to be established in the two PLMNs.

[0193] In another possible implementation, the first information may be identification information about the second PLMN. For example, the first information may be identification information of the second PLMN, a temporary identification of the terminal device in the second PLMN, such as 5G-GUTI, or identification information of the second core network located in the second PLMN, such as GUAMI, etc. The first core network determines that a session needs to be established in the second PLMN through the identification information about the second PLMN.

[0194] It is understandable that the terminal device can also send the basic information required to establish a session in the second PLMN to the first core network. The basic information may include slice information required to establish a session, such as single network slice selection assistance information (S--NSSAI), and data network name (DNN) information. It should be noted that the basic information required to establish a session may also include information defined in other protocols, and the above-mentioned slice information and DNN information are only shown as examples. It is understandable that the basic information can be carried in the first session establishment request, and can also be sent to the first core network through a message different from the first session establishment request.

[0195] S702: The first core network sends a second session establishment request to the second core network.

[0196] Correspondingly, the second core network receives the second session establishment request from the first core network.

[0197] Among them, the second core network is located in the second PLMN. In the embodiment of the present application, the first PLMN and the second PLMN are different. The second session establishment request may include the first information. Optionally, the second session establishment request may be a PDU session establishment request (PDU session establishment request). In one possible scenario, the first core network may send basic information required to establish a session in the second PLMN to the second core network, and the basic information is used by the second core network to establish a session of the terminal device in the second PLMN. It can be understood that the basic information can be carried in the second session establishment request, and can also be sent to the second core network through a message different from the first session establishment request.

[0198] In one possible scenario, the first session establishment request may carry information of the second core network, such as the identifier of the second core network, the identifier of the AMF serving the UE in the second core network, or the temporary identifier of the UE in the second core network (5G-GUTI), etc. Then, the first core network can determine the second core network based on the information of the second core network carried in the first session establishment request, and send a second session establishment request to the second core network.

[0199] In another possible situation, if the first session establishment request does not carry the information of the second core network, the first core network can obtain the context information of the terminal device. The context information of the terminal device stores the information of the second core network, and the first core network can determine the second core network based on the stored information of the second core network, and send the second session establishment request to the second core network.

[0200] S703: The first core network establishes a session for the terminal device in the first PLMN.

[0201] S704: The second core network establishes a session for the terminal device in the second PLMN.

[0202] It should be noted that the embodiment of the present application does not limit the order of steps S703 and S704. S703 may be executed after S704, or S703 may be executed before S704, or S703 may be executed synchronously with S704.

[0203] Based on the above scheme, the terminal device can request to establish a session in the first PLMN and the second PLMN through the first session establishment request. The first core network and the second core network can establish a session in the first PLMN and the second PLMN based on the first information, thereby realizing establishment of a session in the two PLMN networks through a single session establishment request of the terminal device, saving signaling.

[0204] In an embodiment of the present application, in one possible case, the first AMF may send a second session establishment request to the second AMF to establish a session of the terminal device in two PLMN sessions. In another possible case, the first SMF may send a second session establishment request to the second SMF to establish a session of the terminal device in two PLMN sessions. The following is a detailed introduction through method one and method two.

[0205] Method 1: Enhance AMF.

[0206] In method 1, the AMF in the related technology can be enhanced, and through the communication between the first AMF and the second AMF, a session of the terminal device can be established between two PLMN sessions.

[0207] See also Figure 8 , which is an exemplary flow chart of a session establishment method provided in an embodiment of the present application, may include the following steps. Figure 8 In the illustrated embodiment, the first core network may include a first AMF, a first SMF, and a first UPF. Similarly, the second core network may include a second AMF, a second SMF, and a second UPF. When a terminal device is registered with two different networks at the same time and determines that it is currently in a dual-connection state, the terminal device can complete the establishment of a multipath session by sending a session establishment request to the network.

[0208] In one possible scenario, Figure 8In the illustrated embodiment, the first PLMN may be a HPLMN, the second PLMN may be a VPLMN, and the first core network may include an H-AMF, an H-SMF, and an H-UPF. Similarly, the second core network may include a V-AMF, a V-SMF, and a V-UPF. In another possible scenario, the first PLMN may be a VPLMN, the second PLMN may be a HPLMN, and the first core network may include a V-AMF, a V-SMF, and a V-UPF. Similarly, the second core network may include an H-AMF, an H-SMF, and an H-UPF.

[0209] S801: The terminal device sends a first session establishment request to the first AMF.

[0210] Correspondingly, the first AMF receives a first session establishment request from the terminal device.

[0211] S801 may be a possible implementation of S701. The first session establishment request may include first information, and the first information may indicate establishing a session of the terminal device in the HPLMN and the VPLMN. In one possible case, the first session establishment request may be a PDU session establishment request (PDU session establishment request). Optionally, the first session establishment request may include a request type, and the request type may be a multipath session request (request).

[0212] In one example, the terminal device sends basic information required for establishing a session in the second PLMN to the first AMF. For example, the basic information may be carried in the first session establishment request, or may not be carried in the first session establishment request.

[0213] Optional, Figure 8 The illustrated embodiment may further include S802.

[0214] S802: The first AMF selects a suitable first SMF to provide services for the terminal device.

[0215] It can be understood that the embodiment of the present application does not specifically limit the way in which the first AMF selects the first SMF. The first AMF can select an appropriate first SMF to provide services for the terminal device according to the needs of the terminal device.

[0216] S803: The first AMF sends a second session establishment request to the second AMF.

[0217] Correspondingly, the second AMF receives a second session establishment request from the first AMF.

[0218] S803 may be a possible implementation of S702. The second session establishment request may include the first information. In one possible case, the second session establishment request may be a PDU session establishment request. In one example, the first AMF may send basic information required for the second PLMN to establish a session to the second AMF. Optionally, the basic information may be carried in the second session establishment request, or the basic information may not be carried in the second session establishment request.

[0219] Optionally, if the first AMF selects the first SMF in S802, the second session establishment request may also include information of the first SMF selected by the first AMF, such as an identifier of the first SMF or an address of the first SMF.

[0220] In one possible scenario, if the first session establishment request carries the information of the second AMF, such as the identifier (GUAMI) of the second AMF or the address of the second AMF, then the first AMF can send the second session establishment request to the second AMF based on the information of the second AMF. In another possible scenario, if the first session establishment request does not carry the information of the second AMF, then the first AMF can obtain the information of the second AMF by obtaining the context information of the terminal device, and the context information stores the information of the second AMF, such as the identifier (GUAMI) of the second AMF, then the first AMF can send the second session establishment request to the second AMF based on the second AMF information stored in the context information. In an example, if the first session establishment request does not carry the information of the second AMF, then the first AMF can determine that a session of the terminal device needs to be established between the first PLMN and the second PLMN based on the first information, so the first AMF needs to obtain the information of the second AMF, such as obtaining the information of the second AMF by obtaining the context information of the terminal device.

[0221] S804: The second AMF selects the second SMF to provide services for the terminal device.

[0222] Similarly, the embodiment of the present application does not specifically limit the manner in which the second AMF selects the second SMF. The second AMF can select a suitable second SMF to provide services for the terminal device according to the needs of the terminal device.

[0223] In one possible situation, if the first AMF selects the first SMF in S802, or the second session establishment request contains information about the first SMF, then the second AMF can select the second SMF to provide services for the terminal device in S804, that is, the second AMF in S804 does not need to select the first SMF to provide services for the terminal device.

[0224] In another possible situation, if the first AMF does not select the first SMF, or the second session establishment request does not contain information about the first SMF, then in S804 the second AMF may select the second SMF and the first SMF to provide services for the terminal device, that is, the second AMF needs to select the second SMF and the first SMF to provide services for the terminal device.

[0225] Optionally, if the first PLMN is the HPLMN and the second PLMN is the VPLMN, then in S804, the V-AMF can select the H-SMF and the V-SMF to provide services for the terminal device if the H-AMF does not select the A-SMF or the second session establishment request does not contain the H-SMF information. If the first PLMN is the VPLMN and the second PLMN is the HPLMN, then in S802, the V-AMF needs to select a suitable V-SMF to provide services for the terminal device, so the second session establishment request will contain the V-SMF information, and in S804, the H-AMF can select a suitable H-SFM to provide services for the terminal device.

[0226] S805: The second AMF sends the first information and the information of the first SMF to the second SMF.

[0227] For example, the second AMF may send a session establishment request to the second SMF. If there is no association between the second AMF and the second SMF regarding the PDU session identifier (Session ID), the request type of the session establishment request is indicated as "initial request", and the second AMF may send a session establishment request for indicating the establishment of an initial session, such as a session creation message (Nsmf_PDUSession_CreateSMContext). If there is already an association between the second AMF and the second SMF regarding the PDU session identifier (Session ID), the request type of the session establishment request is indicated as "existing PDU session", and the second AMF may send a request for indicating the modification of an existing PDU session, such as a PDU session update message (Nsmf_PDUSession_UpdateSMContex). The session establishment request in S805 may carry the first information and information of the first SMF, such as the identifier of the first SMF or the address of the first SMF.

[0228] It is understandable that the above session creation message or PDU session update message is only shown as an example, and may be called other names in the next generation communication network, such as 6G, and this application does not make specific limitations. The following is an example of a session creation message or a PDU session update message.

[0229] Optional, Figure 8The illustrated embodiment may further include S806 .

[0230] S806: The second SMF sends a session establishment response to the second AMF.

[0231] Correspondingly, the second AMF receives a session establishment response from the second SMF. The second SMF may send a session establishment response to the second AMF according to the session establishment request in S805.

[0232] S807: The second SMF selects a suitable second UPF to provide services for the terminal device.

[0233] It can be understood that the embodiment of the present application does not specifically limit the way in which the second SMF selects the second UPF. The second SMF can select an appropriate second UPF to provide services for the terminal device according to the needs of the terminal device.

[0234] S808: The second SMF sends a fifth session establishment request to the second UPF.

[0235] Correspondingly, the second UPF receives the fifth session establishment request from the second SMF.

[0236] Optionally, the fifth session establishment request may be an N4 message, such as an N4 session establishment request (N4 session establishment request).

[0237] S804 to S808 may be a possible implementation of S704. The fifth session establishment request may be used to request to establish a connection between the second UPF and the terminal device, or the fifth session establishment request is used to request to establish a session of the terminal device. It is understandable that the way in which the second UPF establishes a session for the terminal device can refer to Figure 6 In the embodiment shown, S613 to S622 are implemented or can refer to Figure 5 In the illustrated embodiment, S507 to S515 are implemented and will not be described in detail here.

[0238] After executing S613 to S622 or S507 to S515, it can be considered that a session of the terminal device is established in the second PLMN, and the terminal device can send uplink user plane data to the second PLMN and receive downlink user plane data from the second PLMN.

[0239] Optional, Figure 8 The illustrated embodiment may further include S809.

[0240] S809: The second UPF sends a session establishment response to the fifth session establishment request to the second SMF.

[0241] The second UPF may establish a connection with the terminal device. Optionally, the session establishment response of the fifth session establishment request may be an N4 message, such as an N4 session establishment response (N3 session establishment response).

[0242] S810: The second SMF sends a third session establishment request to the first SMF.

[0243] Correspondingly, the first SMF receives a third session establishment request from the second SMF.

[0244] The third session establishment request may carry the first information and the information of the second UPF, such as the identifier of the second UPF or the address of the second UPF. Optionally, the third session establishment request may be an Nsmf PDU session creation request (Nsmf_PDU session_createSMcontext Request). The third session establishment request may be used to request to establish a connection between the first UPF and the second UPF.

[0245] S811: The first SMF selects a suitable first UPF to provide services for the terminal device.

[0246] Similarly, the embodiment of the present application does not specifically limit the manner in which the first SMF selects the first UPF. The first SMF can select an appropriate first UPF to provide services to the terminal device according to the needs of the terminal device.

[0247] S812: The first SMF sends the second UPF information and the first information to the first UPF.

[0248] Correspondingly, the first UPF receives the second UPF information and the first information from the first SMF.

[0249] Among them, the first SMF can send the information of the second UPF to the first UPF to request to establish a connection between the first UPF and the second UPF, and the first SMF can send the first information to the first UPF to request to establish a connection between the first UPF and the terminal device, or to establish a session for the terminal device in the first PLMN. For example, the first SMF can send an N4 message to the first UPF, such as an N4 session establishment request (N4session establishment request), and the N4 session establishment request can include the information of the second UPF, which is used to request to establish a connection between the first UPF and the second UPF. The N4 session establishment request can also include the first information for requesting to establish a connection between the terminal device and the first UPF, or the N4 session establishment request can include indication information for indicating the session established for the terminal device in the first PLMN, which is used to request the first UPF to establish a session for the terminal device.

[0250] After this step is completed, it can be considered that the path from the first UPF to the second UPF is established, and the first UPF can send downlink data to the second UPF.

[0251] In one possible implementation, if the first PLMN is a HPLMN and the second PLMN is a VPLMN, then Figure 8 The illustrated embodiment may further include the following steps S813A to S816A.

[0252] S813A: The first UPF sends, to the first SMF, information about the session established for the terminal device in the first PLMN and information about the session established for the terminal device in the second PLMN.

[0253] For example, the first UPF may send information of the first UPF, such as an identifier of the first UPF or an address of the first UPF, and information of the second UPF, such as an identifier of the second UPF or an address of the second UPF, to the first SMF.

[0254] After this step is completed, it can be considered that the path from the first UPF to the second UPF is established, and the first UPF can send data to the second UPF.

[0255] S814A: The first SMF sends response information of the third session establishment request to the second SMF.

[0256] Correspondingly, the second SMF receives response information of the third session establishment request from the first SMF.

[0257] For example, the first SMF may send an NsmfPDU session establishment response (Nsmf_PDU Session_create response) to the second SMF according to the third session establishment request sent by the second SMF, wherein the response information of the third session establishment request may include the information of the first UPF.

[0258] S815A: The second SMF sends the information of the first UPF to the second UPF.

[0259] Correspondingly, the second UPF receives information from the first UPF of the second SMF.

[0260] Among them, the second SMF can send the information of the first UPF to the second UPF to request to establish a connection between the second UPF and the first UPF, and the second SMF can send the first information to the second UPF to request to establish a connection between the second UPF and the terminal device, or to establish a session for the terminal device in the second PLMN. For example, the second SMF can send an N4 message to the second UPF, such as an N4 session establishment request (N4session establishment request), and the N4 session establishment request can include the information of the first UPF to request to establish a connection between the second UPF and the first UPF. The N4 session establishment request can also include the first information to request to establish a connection between the terminal device and the second UPF, or the N4 session establishment request can include indication information for indicating the session established for the terminal device in the second PLMN, which is used to request the second UPF to establish a session for the terminal device.

[0261] S816A: The second UPF sends response information to the second SMF.

[0262] Correspondingly, the second UPF receives response information from the second SMF.

[0263] For example, the second UPF may send an N4 session modification response to the second SMF.

[0264] After this step is completed, it can be considered that the path from the second UPF to the first UPF is established, and the second UPF can send data to the first UPF.

[0265] In another possible implementation, if the first PLMN is a VPLMN and the second PLMN is a HPLMN, then Figure 8 The embodiment shown may also include the following steps S813B-816B

[0266] S813B: The first UPF sends response information to the first SMF.

[0267] For example, the first UPF may send an N4 session establishment response to the first SMF.

[0268] S814B: The first SMF sends response information of the third session establishment request to the second SMF.

[0269] Correspondingly, the second SMF receives the response information of the third session establishment request from the first SMF, wherein the response information may include the information of the first UPF.

[0270] S815B: The second SMF sends the information of the first UPF and the first information to the second UPF.

[0271] Correspondingly, the second UPF receives the information of the first UPF and the first information from the second SMF. The second SMF may send the information of the first UPF to the second UPF, requesting to establish a connection between the second UPF and the first UPF. For example, the second SMF may send an N4 message to the second UPF, such as an N4 session establishment request, and the N4 session establishment request may include the information of the first UPF, which is used to request to establish a connection between the second UPF and the first UPF. The N4 session establishment request may also include the first information, which is used to request to establish a connection between the terminal device and the second UPF, or the N4 session establishment request may include indication information for indicating a session established for the terminal device in the second PLMN, which is used to request the second UPF to establish a session for the terminal device.

[0272] S816B: The second UPF sends to the second SMF the information of the session established for the terminal device in the first PLMN and the information of the session established for the terminal device in the second PLMN.

[0273] For example, the first UPF may send information of the first UPF, such as an identifier of the first UPF or an address of the first UPF, and information of the second UPF, such as an identifier of the second UPF or an address of the second UPF, to the first SMF. For example, the second UPF may send an N4 session modification response to the second SMF. The response information may include information of a session established for the terminal device in the HPLMN and information of a session established for the terminal device in the VPLMN, such as information of the second UPF and information of the first UPF.

[0274] After this step is completed, it can be considered that the path from the second UPF to the first UPF is established, and the second UPF can send data to the first UPF.

[0275] In the embodiment of the present application, the first UPF establishing a connection with the terminal device can be understood as establishing a session for the terminal device in the first PLMN. It can be understood that if the first PLMN is the HPLMN, the way in which the first UPF establishes a session for the terminal device can refer to Figure 5 In the embodiment shown in FIG. 507-515, if the first PLMN is a VPLMN, the first UPF may establish a session for the terminal device in a manner as described in the embodiment shown in FIG. Figure 6 S613 to S622 are implemented in the illustrated embodiment and will not be described in detail here.

[0276] Similarly, the second UPF establishing a connection with the terminal device can be understood as establishing a session for the terminal device in the second PLMN. It can be understood that if the second PLMN is the HPLMN, the way in which the second UPF establishes a session for the terminal device can refer to Figure 5 In the embodiment shown in FIG. 1 , S507 to S515 are implemented. If the second PLMN is a VPLMN, the second UPF may establish a session for the terminal device in a manner similar to that described in FIG. 1 . Figure 6 S613 to S622 are implemented in the illustrated embodiment and will not be described in detail here.

[0277] It should be noted that in the embodiment of the present application, when the first PLMN is the HPLMN and the second PLMN is the VPLMN, the step of the first UPF establishing a connection with the terminal device can be performed after S813A, and the first SMF sends a request message to the first AMF to initiate the session establishment process. The step of the second UPF establishing a connection with the terminal device can be performed after S8016A, and the second SMF sends a request message to the second AMF to initiate the session establishment process.

[0278] Similarly, in the embodiment of the present application, when the first PLMN is a VPLMN and the second PLMN is a HPLMN, the step of the first UPF establishing a connection with the terminal device can be performed after S813B, and the first SMF sends a request message to the first AMF to initiate a session establishment process. The step of the second UPF establishing a connection with the terminal device can be performed after S8016B, and the second SMF sends a request message to the second AMF to initiate a session establishment process.

[0279] Method 2: Enhance SMF.

[0280] In the second method, the SMF in the related technology can be enhanced, and the establishment of a session of the terminal device in two PLMN sessions can be achieved through the communication between the first SMF and the second SMF.

[0281] See also Fig. 9 , which is an exemplary flow chart of a session establishment method provided in an embodiment of the present application, may include the following steps. Fig. 9 In the illustrated embodiment, the first PLMN may be a VPLMN, the second PLMN may be a HPLMN, and the first core network may be a core network of the VPLMN, including a V-AMF, a V-SMF, and a V-UPF. Similarly, the second core network may be a core network of the HPLMN, including an H-AMF, an H-SMF, and an H-UPF.

[0282] S901: The terminal device sends a first session establishment request to the V-AMF.

[0283] Correspondingly, V-AMF receives a first session establishment request from the terminal device.

[0284] S901 may be a possible implementation of S701. The first session establishment request may include first information, and the first information may indicate establishing a session of the terminal device in the HPLMN and the VPLMN. In one possible case, the first session establishment request may be a PDU session establishment request (PDU session establishment request). Optionally, the first session establishment request may include a request type, and the request type may be a multipath session request (request).

[0285] S902: V-AMF selects a suitable V-SMF to provide services for the terminal device.

[0286] S903: V-SMF sends a fourth session establishment request to V-SMF.

[0287] Correspondingly, V-SMF receives the fourth session establishment request from V-AMF.

[0288] Among them, the first information may be included in the fourth session establishment request. If there is no association between V-AMF and V-SMF regarding the PDU session identifier (Session ID), the request type indication of the session establishment request is "initial request", and V-AMF sends a session creation message (Nsmf_PDUSession_CreateSMContext). If there is already an association between V-AMF and V-SMF regarding the PDU session identifier (Session ID), the request type indication of the session establishment request is "existing PDU session", and V-AMF sends a PDU session update message (Nsmf_PDUSession_UpdateSMContex).

[0289] Optional, Fig. 9 The illustrated embodiment may further include S904 .

[0290] S904: V-SMF sends response information of the fourth session establishment request to V-AMF.

[0291] Correspondingly, V-AMF receives response information of the fourth session establishment request from V-SMF.

[0292] For example, V-AMF may send a session establishment response to V-AMF based on the session establishment request in S903.

[0293] S905: The V-SMF selects a suitable V-UPF to provide services for the terminal device.

[0294] S906: V-SMF sends a fifth session establishment request to V-UPF.

[0295] Correspondingly, the V-UPF receives the fifth session establishment request from the V-SMF.

[0296] The fifth session establishment request may be used to request to establish a connection between the V-UPF and the terminal device, or in other words, the fifth session establishment request is used to request to establish a session of the terminal device.

[0297] Optionally, the fifth session establishment request may be an N4 message, such as an N4 session establishment request (N4 session establishment request).

[0298] Optional, Fig. 9 The illustrated embodiment may further include S907 .

[0299] S907: The V-UPF sends a session establishment response to the fifth session establishment request to the V-SMF.

[0300] The V-UPF may establish a connection with the terminal device. Optionally, the session establishment response of the fifth session establishment request may be an N4 message, such as an N4 session establishment response (N3 session establishment response).

[0301] S908: V-SMF sends a second session establishment request to H-SMF.

[0302] Correspondingly, H-SMF receives the second session establishment request from V-SMF.

[0303] S908 may be a possible implementation of S702. The second session establishment request may include the first information. In one example, the V-SMF may send basic information required to establish a session in the HPLMN to the H-SMF. Optionally, the basic information may be carried in the second session establishment request or may not be carried in the second session establishment request. In one possible scenario, the second session establishment request may be an N4 PDU session establishment request (N4 PDU session establishment request). The second session establishment request may also include information of the V-UPF.

[0304] S909: The H-SMF selects a suitable H-UPF to provide services for the terminal device.

[0305] S910: H-SMF sends V-UPF information and first information to H-UPF.

[0306] Correspondingly, the H-UPF receives the V-UPF information and the first information from the H-SMF.

[0307] Among them, the H-SMF can send V-UPF information to the H-UPF to request to establish a connection between the H-UPF and the V-UPF, and the H-SMF can send first information to the H-UPF to request to establish a connection between the H-UPF and the terminal device, or to establish a session for the terminal device in the HPLMN. For example, the H-SMF can send an N4 message to the H-UPF, such as an N4 session establishment request (N4 session establishment request), and the N4 session establishment request can include V-UPF information for requesting to establish a connection between the H-UPF and the V-UPF. The N4 session establishment request can also include first information for requesting to establish a connection between the terminal device and the H-UPF, or the N4 session establishment request can include indication information for indicating a session established for the terminal device in the HPLMN, for requesting the H-UPF to establish a session for the terminal device.

[0308] S911: The H-UPF sends the session information established for the terminal device in the HPLMN and the session information established for the terminal device in the VPLMN to the H-SMF. For example, the H-UPF may send the H-UPF information and the H-UPF information to the V-SMF.

[0309] Among them, the H-UPF can establish a connection with the V-UPF according to the information of the V-UPF, and the H-UPF can establish a connection with the terminal device. The H-UPF can obtain the information of the V-UPF from the V-UPF and send it to the H-SMF.

[0310] After this step is completed, it can be considered that the path from H-UPF to V-UPF is established, and H-UPF can send data to V-UPF.

[0311] S912 to S922 can be implemented with reference to S612 to S622.

[0312] After executing 912 to S923, it can be understood that a session of the terminal device is established in the VPLMN, and the terminal device can send uplink data to the VPLMN through the user, and receive downlink data from the VPLMN.

[0313] S923 to S929 can be implemented with reference to S509 to S515.

[0314] S930: H-SMF updates the session context information of the terminal device to H-AMF.

[0315] Fig. 9In the illustrated embodiment, H-AMF does not participate in the previous operation, so H-SMF needs to update the session context to H-AMF.

[0316] Similarly, after executing S923 to S930, it can be understood that a session of the terminal device is established in the HPLMN, and the terminal device can send uplink data to the HPLMN through the user interface, and receive downlink data from the HPLMN.

[0317] It should be noted that Fig. 9 The operation of establishing a session in the HPLMN is placed after the operation of establishing a session in the VPLMN for exemplary purposes, and does not limit the order between the operation of establishing a session in the HPLMN and the operation of establishing a session in the VPLMN, and the two operations can be performed simultaneously.

[0318] It can be understood that in the embodiment of the present application, the step of the first UPF establishing a connection with the terminal device can be performed after S914, and the first SMF sends a request message to the first AMF to initiate the session establishment process. The step of the second UPF establishing a connection with the terminal device can be performed after S911, and the second SMF sends a request message to the second AMF to initiate the session establishment process.

[0319] based on Fig. 9 The solution shown can enhance the SMF in the related technology and realize the interaction between the first SMF and the second SMF, so that the terminal device can establish a session in two networks through one session establishment request.

[0320] Another session establishment method is also provided in the embodiment of the present application. Fig.10 , which is an exemplary flowchart of a session establishment method provided in an embodiment of the present application, may include the following operations. Fig.10 In the illustrated embodiment, the first core network is located in a first PLMN, and the second core network is located in a second PLMN.

[0321] S1001: The terminal device sends a first session establishment request to the first core network.

[0322] Correspondingly, the first core network receives a first session establishment request from the terminal device.

[0323] S1001 can be implemented with reference to S701.

[0324] S1002: The first core network sends a second session establishment request to the second core network.

[0325] Correspondingly, the second core network receives the second session establishment request from the first core network.

[0326] S1002 can be implemented with reference to S703.

[0327] S1003: The second core network sends first response information to the first core network.

[0328] Correspondingly, the first core network receives the first response information from the second core network.

[0329] The first response information may indicate that establishment of a session with the terminal device has failed.

[0330] Optionally, the first response information may also indicate failure to establish a session in the first PLMN and / or failure to establish a session in the second PLMN.

[0331] S1004: The first core network sends a first response message to the terminal device.

[0332] Correspondingly, the terminal device receives the first response information from the first core network.

[0333] In a possible implementation, the first core network may include a first AMF, a first SMF and a first UPF. Similarly, the second core network may include a second AMF, a second SMF and a second UPF. Fig.11 Provide a detailed introduction.

[0334] See also Fig.11 , which is an exemplary flow chart of a session establishment method provided in an embodiment of the present application, may include the following steps. In one possible scenario, if the first PLMN is an HPLMN and the second PLMN is a VPLMN, then S1101 to S1112 may be implemented with reference to S801 to S812. In another possible scenario, if the first PLMN is a VPLMN and the second PLMN is an HPLMN, then S1101 to S1105 may be implemented with reference to S801 to S812 and S813B to S815B. Fig.11 The illustrated embodiment may also include the following steps.

[0335] S1116: H-UPF sends a second response message to H-SMF.

[0336] Correspondingly, the H-SMF receives the second response information from the H-UPF.

[0337] The second response information may indicate that a session of the terminal device fails to be established in the first PLMN, or fails to be established in the second PLMN. For example, the second response information may indicate that a session of the terminal device fails to be established in the HPLMN, or fails to be established in the VPLMN.

[0338] In one possible scenario, the second response information may carry an indication information, such as indicating that the HPLMN PDU session establishment failed (session establish fail) or indicating that the VPLMN PDU session establishment failed (session establish fail). In another possible scenario, the second response information may be a 1-bit indication information, such as when the value is 0, it indicates that the session establishment of the terminal device in the HPLMN failed, and when the value is 1, it indicates that the session establishment of the terminal device in the VPLMN failed. Conversely, when the value is 1, it indicates that the session establishment of the terminal device in the HPLMN failed, and when the value is 0, it indicates that the session establishment of the terminal device in the VPLMN failed.

[0339] Optionally, the second response information may only include the session information of the first PLMN, that is, the second response information may not include the session information of the second PLMN, thereby indicating that the session establishment of the terminal device in the second PLMN has failed. Similarly, the second response information may only include the session information of the second PLMN, that is, the second response information may not include the session information of the first PLMN, thereby indicating that the session establishment of the terminal device in the first PLMN has failed. For example, the second response information may only include the session information of the VPLMN, such as the information of the V-UPF, and does not include the session information of the HPLMN, such as the information of the H-UPF. The H-SMF may determine that the session establishment of the terminal device in the HPLMN has failed if the session information of the HPLMN is not received. For another example, the second response information may only include the session information of the HPLMN, such as the information of the H-UPF, and does not include the session information of the VPLMN, such as the information of the V-UPF. The H-SMF may determine that the session establishment of the terminal device in the VPLMN has failed if the session information of the VPLMN is not received.

[0340] Optionally, the second response information may be an N4 session establishment failure response (N4 session establishmentresponse).

[0341] S1117: The H-SMF sends a third response message to the V-SMF. The third response message may indicate that the session establishment for the terminal device fails. Optionally, the third response message may also carry the reason for the session establishment failure, such as the failure to establish a session for the terminal device in the HPLMN or the failure to establish a session for the terminal device in the VPLMN.

[0342] In one example, if the third response information indicates that the session establishment of the terminal device in the VPLMN fails, the core network of the HPLMN can still establish a session of the terminal device in the HPLMN, which can be implemented with reference to S509 to S515. Among them, the step of the HPLMN establishing a session of the terminal device can be performed after S1116, and the H-SMF sends a request message to the H-AMF to initiate the session establishment process.

[0343] In another example, if the third response information indicates that the session establishment of the terminal device in the HPLMN fails, the core network of the VPLMN will not establish the session of the terminal device in the VPLMN. Fig.11 The illustrated embodiment may further include the following operations S1118 to S1120 .

[0344] S1118: V-SMF sends a third response message to V-AMF.

[0345] Correspondingly, V-AMF receives the third response information from V-SMF.

[0346] The third response information may indicate that the session establishment for the terminal device fails. Optionally, if S1117 indicates that the session establishment for the terminal device in the HPLMN fails, S1118 may also carry the reason for the session establishment failure, such as the session establishment for the terminal device in the HPLMN fails.

[0347] Optionally, the third response information may be an Nsmf PDU session establishment response (Nsmf_PDU session_creatresponse).

[0348] S1119: V-AMF sends the first response information to H-AMF.

[0349] Correspondingly, H-AMF receives the first response information from V-AMF.

[0350] The first response information may indicate that the session establishment for the terminal device fails. Optionally, if the third response information carries the reason for the session establishment failure, the first response information may also carry the reason for the session establishment failure, such as the session establishment failure for the terminal device in the HPLMN.

[0351] Optionally, the first information may be a PDU session establishment response (PDU session establishment response).

[0352] S1120: H-AMF sends a first response message to the terminal device.

[0353] Correspondingly, the terminal device receives the first response information from H-AMF.

[0354] Based on the above solution, when the session establishment of the terminal device in the HPLMN fails, the session of the terminal device will not be established in the VPLMN.

[0355] It should be noted that the names of the various messages shown in the embodiments of the present application are only shown as examples, and their names may change in the next generation of communications. The present application does not specifically limit the names of the various messages. The information carried in each message can be implemented with reference to the information shown in the aforementioned embodiments.

[0356] pass Figure 7 to Figure 11 A method for establishing a session provided by an embodiment of the present application is introduced. The following further introduces the method for establishing a session provided by an embodiment of the present application through some specific embodiments.

[0357] Embodiment 1:

[0358] See also Fig.12 , which is an exemplary flowchart of a session establishment method provided in an embodiment of the present application, may include the following operations.

[0359] When the UE is registered with two different networks at the same time, the UE determines that it is currently in a dual-connection state. At this time, the UE can complete the establishment of a multi-path session by sending a session establishment request to the network.

[0360] S1201: UE sends a session establishment request to H-AMF.

[0361] Accordingly, the H-AMF receives a session establishment request from the UE.

[0362] The request type carried by the UE is a multipath session request.

[0363] It is understandable that the UE needs to indicate to the H-AMF that the session is established in two PLMNs, such as the HPLMN and the VPLMN. In one possible implementation, the UE may carry additional indication information in the session establishment request in S1201, indicating that the session needs to be established in two different PLMNs, such as the VPLMN and the HPLM. In another possible implementation, the UE does not need additional indication information. The H-AMF confirms the UE's context information based on the UE's request type being a multi-path session request. If the UE is in a dual-connected state and is registered with two different PLMNs, the H-AMF considers that a session needs to be established in the two PLMNs. In another possible implementation, the UE may carry identification information corresponding to the V-AMF of the VPLMN, such as GUAMI or 5G-GUTI, and use this identification information to indicate that the H-AMF needs to establish a session in two PLMNs, and instruct the H-AMF to send a session establishment request to the V-AMF.

[0364] In addition, the UE needs to carry information such as the corresponding S-NSSAI and DNN in the VPLMN in the session establishment request.

[0365] Optional, Fig.12 The illustrated embodiment also includes the following operation S1202.

[0366] S1202: The H-AMF selects a suitable H-SMF to serve the UE.

[0367] S1203: H-AMF sends a session establishment request to V-AMF.

[0368] Correspondingly, V-AMF receives the session establishment request from H-AMF.

[0369] Among them, if the identification information of V-AMF is carried in S1201, H-AMF sends a session establishment request to V-AMF according to the identification information. If the identification information of V-AMF is not carried in S1201, H-AMF can select the corresponding V-AMF according to the information of V-AMF stored in the UE context information, and send a session establishment request.

[0370] In one possible implementation, if the H-AMF in S1202 selects a suitable H-SMF to serve the UE, the session establishment request in S1203 needs to include information about the H-SMF selected in S1202. In another possible implementation, the H-AMF does not select the H-SMF, and S1203 does not carry information about the H-SMF, and the V-AMF selects the H-SMF.

[0371] S1204: V-AMF selects a suitable SMF to serve the UE.

[0372] For example, the V-AMF selects a suitable V-SMF to serve the UE. Optionally, if S1203 does not carry information of the H-SMF, the V-AMF may select a suitable H-SMF to serve the UE in S1204.

[0373] S1205: V-AMF sends a session establishment request to V-SMF.

[0374] Correspondingly, V-SMF receives a session establishment request from V-AMF.

[0375] Among them, if there is no association between V-AMF and V-SMF regarding the PDU session ID (PDU Session ID), the type of request indicated in S1205 is "initial request", and V-AMF calls Nsmf_PDUSession_CreateSMContext. If there is already an association between V-AMF and V-SMF regarding the PDU session ID (PDU Session ID), the type of request indicated in S1205 is "existing PDU session", and V-AMF calls Nsmf_PDUSession_UpdateSMContext.

[0376] Under the HR architecture, V-AMF also needs to send H-SMF information to V-SMF.

[0377] S1206: V-SMF sends a response message to V-AMF according to the request of V-AMF in S1205.

[0378] Correspondingly, V-AMF receives the response information from V-SMF.

[0379] S1207: The V-SMF selects a suitable V-UPF to serve the UE.

[0380] S1208: If V-AMF indicates an initial request to V-SMF in S1205, then V-SMF sends an N4 session establishment request to V-UPF. If V-AMF requests V-SMF to modify an existing session in S1205, then V-SMF sends an N4 session modification request to V-UPF.

[0381] S1209: V-UPF sends response information to V-SMF according to the request of S1208.

[0382] Correspondingly, V-SMF receives response information from V-UPF.

[0383] S1210: V-SMF sends a session establishment request to H-SMF, and sends V-UPF information to H-SMF.

[0384] Correspondingly, H-SMF receives the session establishment request from V-SMF and the information from V-UPF.

[0385] Among them, the information of V-UPF is used to establish the connection between H-UPF and V-UPF. In addition, V-SMF needs to instruct H-SMF to establish a session in HPLMN. In one possible implementation, V-SMF can attach an indication information to the session establishment request to directly indicate that an additional session is required. In another possible implementation, V-SMF indicates to H-SMF that the UE is in a dual-connection state and a multi-path session is established, implicitly indicating that an additional session needs to be established in the HPLMN.

[0386] S1211: H-SMF selects a suitable H-UPF to serve the UE.

[0387] S1212: H-SMF sends an N4 session establishment request to H-UPF.

[0388] Correspondingly, the H-UPF receives the N4 session establishment request from the H-SMF. The N4 session establishment request may include V-UPF information (info) for establishing a connection between the H-UPF and the V-UPF. In addition, the H-SMF also needs to instruct the UPF to establish a connection in the HPLMN, that is, the H-UPF needs to directly establish a connection with the UE.

[0389] S1213: The H-UPF sends response information to the H-SMF according to the request in S1212, and the H-UPF needs to feed back the HPLMN session information and the VPLMN session information to the H-SMF, such as the H-UPF information and the V-UPF information.

[0390] Correspondingly, the H-SMF receives the response information from the H-UPF, as well as the HPLMN session information and the VPLMN session information.

[0391] After this step is completed, it can be considered that the path from H-UPF to V-UPF is established, and H-UPF can send downlink data to V-UPF.

[0392] S1214: H-SMF sends a response message to V-SMF according to the request in S1210, and the response message includes H-UPF information.

[0393] Correspondingly, V-SMF receives the response information from H-SMF.

[0394] S1215: V-SMF sends an N4 session modification request to V-UPF, including H-UPF information.

[0395] Correspondingly, the V-UPF receives the N4 session modification request from the V-SMF, including the H-UPF information, wherein the H-UPF information is used to establish an uplink from the V-UPF to the H-UPF.

[0396] S1216: V-UPF sends a response message to V-SMF according to the request of S1215.

[0397] Correspondingly, V-SMF receives response information from V-UPF.

[0398] After this step is completed, it can be considered that the path from V-UPF to H-UPF is established, and V-UPF can send uplink data to H-UPF.

[0399] The following describes an implementation method for establishing a VPLMN session.

[0400] S1217~S1220 can be implemented with reference to S615~S618.

[0401] After completing S1220, the uplink establishment can be considered complete, and the UE can send an uplink data flow to the V-UPF.

[0402] S1221~S1223 can be implemented with reference to S619~S621.

[0403] After completing S1223, the downlink establishment can be considered complete, and the V-UPF can send downlink data flow to the UE.

[0404] S1224: V-SMF updates the session context to V-AMF.

[0405] The following describes an implementation method for establishing a HPLMN session.

[0406] S1225~S1228 can be implemented with reference to S508~S511.

[0407] After completing S1228, it can be considered that the uplink establishment is completed, and the UE can send an uplink data flow to the H-UPF.

[0408] S1229~S1231 can be implemented with reference to S512~S514.

[0409] After completing S1231, it can be considered that the downlink establishment is completed, and the H-UPF can send the downlink data flow to the UE.

[0410] S1232: H-SMF updates the session context to H-AMF.

[0411] It should be noted that Fig.12 The operation of establishing a session in the HPLMN is placed after the operation of establishing a session in the VPLMN for exemplary purposes, and does not limit the order between the operation of establishing a session in the HPLMN and the operation of establishing a session in the VPLMN, and the two operations can be performed simultaneously.

[0412] It can be understood that the step of establishing a session in the HPLMN in the embodiment of the present application can be performed after S1213, and the H-SMF sends a request message to the H-AMF to initiate the session establishment process. The step of establishing a session in the VPLMN can be performed after S1216, and the V-SMF sends a request message to the V-AMF to initiate the session establishment process.

[0413] exist Fig.12 The illustrated embodiment describes a scenario in which a session is successfully established. The scenario in which a session is failed to be established can be divided into the following two situations.

[0414] In the first case, the UE fails to establish a session on the HPLMN side. In this case, the network should consider that the UE cannot obtain the service and reject the UE from establishing the session. Fig.13 , which is an exemplary flowchart of a session establishment method provided in an embodiment of the present application, may include the following operations.

[0415] S1301 to S1312 can be implemented with reference to S1601 to S1612.

[0416] S1313: H-UPF feeds back to H-SMF the failure of establishing the HPLMN session.

[0417] In one possible implementation, the H-UPF explicitly indicates the H-SMF session establishment failure, such as carrying an indication information, for example, indicating that the HPLMN PDU session establishment failure (HPLMN PDU Session establish fail). In another possible implementation, the H-UPF may implicitly indicate the H-SMF session establishment failure, such as when feeding back the session establishment information to the H-SMF, only the session information of the VPLMN is fed back. The H-SMF determines based on its own logic that if the session information of the HPLMN is not received, it considers that the session establishment of the HPLMN has failed.

[0418] S1314: H-SMF indicates to V-SMF that session establishment has failed.

[0419] Optionally, the H-SMF may indicate to the V-SMF that the reason for the session establishment failure is the HPLMN session establishment failure.

[0420] S1315: V-SMF feeds back to V-AMF that session establishment failed.

[0421] Optionally, if the H-SMF indicates to the V-SMF in S1314 that the reason for the failure to establish the session is the failure to establish the session of the HPLMN, the V-SMF indicates to the V-AMF that the reason for the failure to establish the session is the failure to establish the session of the HPLMN.

[0422] S1316: V-AMF feeds back to H-AMF that session establishment failed.

[0423] Among them, if the V-SMF carries the reason for the failure when feeding back the session establishment failure to the V-AMF that the session establishment failure of the HPLMN fails, the V-AMF indicates to the H-SMF that the reason for the session establishment failure is the session establishment failure of the HPLMN.

[0424] S1317: H-AMF sends a response message of session establishment failure to the UE.

[0425] Among them, if the V-AMF feeds back to the H-AMF the failure of session establishment and carries the cause of the failure is the failure of session establishment of the HPLMN, the H-AMF indicates to the UE that the cause of the failure of session establishment is the failure of session establishment of the HPLMN.

[0426] exist Fig.13 In the illustrated embodiment, since the session establishment in the HPLMN fails, there is no need to establish a session in the VPLMN.

[0427] In the second case, the UE fails to establish a session in the VPLMN. In this case, the network should assume that the UE cannot obtain services in the VPLMN and only establish a session in the HPLMN.

[0428] See also Fig.14 , which is an exemplary flowchart of a session establishment method provided in an embodiment of the present application, may include the following operations.

[0429] S1401 to S1412 can be implemented with reference to S1601 to S1612.

[0430] S1413: H-UPF feeds back to H-SMF the failure of establishing the VPLMN session.

[0431] In one possible implementation, the H-UPF explicitly indicates to the H-SMF that the session establishment fails, such as carrying an indication information, for example, indicating that the VPLMN PDU session establishment fails (VPLMN PDU Session establish fail). In another possible implementation, the H-UPF may implicitly indicate to the H-SMF that the session establishment fails, such as when feeding back the session establishment information to the H-SMF, only the session information of the HPLMN is fed back. The H-SMF determines based on its own logic that if the session information of the VPLMN is not received, it considers that the session establishment of the VPLMN fails.

[0432] S1414: H-SMF indicates to V-SMF that session establishment has failed.

[0433] Optionally, the H-SMF may indicate to the V-SMF that the reason for the session establishment failure is the session establishment failure of the VPLMN.

[0434] S1415: V-SMF feeds back to V-AMF that session establishment failed.

[0435] If the H-SMF indicates to the V-SMF in S1414 that the reason for the session establishment failure is the failure to establish a session of the VPLMN, the V-SMF indicates to the V-AMF that the reason for the session establishment failure is the failure to establish a session of the VPLMN.

[0436] S1416: V-AMF sends a response message of session establishment failure to the UE.

[0437] If the V-SMF feeds back to the V-AMF the failure of session establishment and carries the reason of failure as the failure of session establishment of the VPLMN, the H-AMF indicates to the UE that the reason of session establishment failure is the failure of session establishment of the VPLMN.

[0438] S1417 to S1424 may be implemented with reference to S508 to S515. It is understandable that the step of establishing a session in the HPLMN in the embodiment of the present application may be performed after S1413, with the H-SMF sending a request message to the H-AMF to initiate the session establishment process.

[0439] Embodiment 2

[0440] See also Fig.15 , which is an exemplary flowchart of a session establishment method provided in an embodiment of the present application, may include the following operations.

[0441] When the UE is registered with two different networks at the same time, the UE determines that it is currently in a dual-connection state. At this time, the UE can complete the establishment of a multi-path session by sending a session establishment request to the network.

[0442] S1501: UE sends a session establishment request to V-AMF.

[0443] Correspondingly, the V-AMF receives a session establishment request from the UE, wherein the request type carried by the UE is a multipath session request.

[0444] It is understandable that the UE needs to indicate to the V-AMF that the session is established in two PLMNs, such as the HPLMN and the VPLMN. In another possible implementation, the UE may carry additional indication information in the session establishment request in S1501, indicating that the session needs to be established in two different PLMNs, such as the VPLMN and the HPLM. In another possible implementation, the UE does not need additional indication information. The V-AMF confirms the UE's context information based on the UE's request type being a multi-path session request. If the UE is in a dual-connected state and is registered with two different PLMNs, the V-AMF considers that a session needs to be established in the two PLMNs. In another possible implementation, the UE may carry identification information corresponding to the H-AMF of the HPLMN, such as GUAMI or 5G-GUTI, and use this identification information to indicate that the V-AMF needs to establish a session in two PLMNs, and instruct the V-AMF to send a session establishment request to the H-AMF.

[0445] S1502: V-AMF selects a suitable V-SMF to serve the UE.

[0446] S1503: V-AMF sends a session establishment request to V-SMF.

[0447] Correspondingly, V-SMF receives a session establishment request from V-AMF.

[0448] Among them, if there is no association between V-AMF and V-SMF regarding the PDU Session ID (PDU Session ID), then the type of request indicated in S1503 is "initial request", and V-AMF calls Nsmf_PDUSession_CreateSMContext. If there is already an association between V-AMF and V-SMF regarding the PDU Session ID (PDU Session ID), then the type of request indicated in S1503 is "existing PDU session", and V-AMF calls Nsmf_PDUSession_UpdateSMContext. In addition, V-AMF needs to indicate to V-SMF that the session needs to be established in two PLMNs.

[0449] S1504: V-SMF sends a response message to V-AMF according to the session establishment request in S1503.

[0450] S1505: The V-SMF selects a suitable V-UPF to serve the UE.

[0451] S1506: If V-AMF indicates an initial request to V-SMF in S1503, then V-SMF sends an N4 session establishment request to V-UPF. If V-AMF requests V-SMF to modify an existing session in S1503, then V-SMF sends an N4 session modification request to V-UPF.

[0452] S1507: V-UPF sends a response message to V-SMF according to the session establishment request in S1506.

[0453] S1508: V-SMF sends a session establishment request to H-SMF, and sends V-UPF information to H-SMF.

[0454] Among them, the information of V-UPF is used to establish the connection between H-UPF and V-UPF. In addition, V-SMF needs to instruct H-SMF to establish a session for the terminal device in the HPLMN. In one possible implementation, V-SMF can carry an indication information in the session establishment request, directly indicating that an additional session is required, that is, to establish a session in the HPLMN. In another possible implementation, V-SMF indicates that the UE is in a dual-connection state and a multi-path session is established, implicitly indicating that an additional session needs to be established in the HPLMN.

[0455] S1509: The H-SMF selects a suitable H-UPF to serve the UE.

[0456] S1510: H-SMF sends an N4 session establishment request to H-UPF.

[0457] Correspondingly, the H-UPF receives an N4 session establishment request from the H-SMF. The N4 session establishment request may include V-UPF information for establishing a connection between the H-UPF and the V-UPF. In addition, the H-SMF also needs to instruct the H-UPF to establish a connection in the HPLMN, that is, the H-UPF needs to establish a connection directly with the UE.

[0458] S1511: H-UPF sends a response message to H-SMF according to the N4 session establishment request in S1510.

[0459] Accordingly, the H-SMF receives the response information from the H-UPF. In addition, the H-UPF needs to feed back the HPLMN session information and the VPLMN session information to the H-SMF, such as the H-UPF information and the V-UPF information, such as the H-UPF address and the V-UPF address.

[0460] After this step is completed, it can be considered that the path from H-UPF to V-UPF is established, and H-UPF can send downlink data to V-UPF.

[0461] S1512: H-SMF sends a response message to V-SMF according to the session establishment request in S1508.

[0462] Correspondingly, the V-SMF receives the response information from the H-SMF, wherein the response information may include the H-UPF information.

[0463] S1513: V-SMF sends an N4 session modification request to V-UPF.

[0464] Correspondingly, the V-UPF receives an N4 session modification request from the V-SMF, wherein the N4 session modification request includes information of the H-UPF for establishing an uplink from the V-UPF to the H-UPF.

[0465] S1514: V-UPF sends a response message to V-SMF according to the session establishment request in S1513.

[0466] Correspondingly, V-SMF receives the response information from V-UPF. After this step is completed, it can be considered that the path from V-UPF to H-UPF is established, and V-UPF can send uplink data to H-UPF.

[0467] The following describes an implementation method for establishing a VPLMN session.

[0468] S1515~S1518 can be implemented with reference to S615~S618.

[0469] After completing S1518, the uplink establishment can be considered complete, and the UE can send uplink data flow to the V-UPF.

[0470] S1519~S1521 can be implemented with reference to S615~S621.

[0471] After completing S1521, the downlink establishment can be considered complete, and the V-UPF can send downlink data flow to the UE.

[0472] S1522: V-SMF updates the session context to V-AMF.

[0473] The following describes an implementation method for establishing a HPLMN session.

[0474] S1523 to S1526 can be implemented with reference to S508 to S511.

[0475] After completing S1526, it can be considered that the uplink establishment is completed, and the UE can send an uplink data flow to the H-UPF.

[0476] S1527~S1529 can be implemented with reference to S512~S514.

[0477] After completing S1529, it can be considered that the downlink establishment is completed, and the H-UPF can send the downlink data flow to the UE.

[0478] S1530: H-SMF updates the session context to H-AMF.

[0479] It should be noted that Fig.15 The operation of establishing a session in the HPLMN is placed after the operation of establishing a session in the VPLMN for exemplary purposes, and does not limit the order between the operation of establishing a session in the HPLMN and the operation of establishing a session in the VPLMN, and the two operations can be performed simultaneously.

[0480] It can be understood that the step of establishing a session in the HPLMN in the embodiment of the present application can be performed after S1511, and the H-SMF sends a request message to the H-AMF to initiate the session establishment process. The step of establishing a session in the VPLMN can be performed after S1514, and the V-SMF sends a request message to the V-AMF to initiate the session establishment process.

[0481] In addition, the difference between the first embodiment and the second embodiment is that the methods of triggering the establishment of a session are different, and the processing of the failure of the session establishment is the same, so the relevant process of the failure of the session establishment in the first embodiment can be referred to.

[0482] Embodiment three:

[0483] See also Fig.16 , which is an exemplary flowchart of a session establishment method provided in an embodiment of the present application, may include the following operations.

[0484] When the UE is registered with two different networks at the same time, the UE determines that it is currently in a dual-connection state. At this time, the UE can complete the establishment of a multi-path session by sending a session establishment request to the network.

[0485] S1601: UE sends a session establishment request to V-AMF.

[0486] Correspondingly, V-AMF receives a session establishment request from the UE.

[0487] The request type carried by the UE is a multipath session request.

[0488] It is understandable that the UE needs to indicate to the H-AMF that the session is established in two PLMNs, such as the HPLMN and the VPLMN. In one possible implementation, the UE may carry additional indication information in the session establishment request in S1601, indicating that the session needs to be established in two different PLMNs, such as the VPLMN and the HPLM. In another possible implementation, the UE does not need additional indication information. The H-AMF confirms the UE's context information based on the UE's request type being a multi-path session request. If the UE is in a dual-connected state and is registered with two different PLMNs, the H-AMF considers that a session needs to be established in the two PLMNs. In another possible implementation, the UE may carry identification information corresponding to the V-AMF of the VPLMN, such as GUAMI or 5G-GUTI, and use this identification information to indicate that the H-AMF needs to establish a session in two PLMNs, and instruct the H-AMF to send a session establishment request to the V-AMF.

[0489] In addition, the UE needs to carry the corresponding S-NSSAI and DNN information in the HPLMN in the session establishment request.

[0490] S1602: The V-AMF selects a suitable V-SMF to serve the UE.

[0491] S1603: V-AMF sends a session establishment request to H-AMF.

[0492] Correspondingly, H-AMF receives the session establishment request from V-AMF.

[0493] Among them, if the UE carries the identification information of H-AMF in S1601, V-AMF sends a session establishment request to H-AMF according to the identification information. If the UE does not carry the identification information of H-AMF in S1601, V-AMF can select the corresponding H-AMF according to the information of H-AMF stored in the context information of UE, and send a session establishment request. Among them, the session establishment request needs to include the information of V-SMF selected in S1602.

[0494] S1604: H-AMF selects a suitable H-SMF to serve the UE.

[0495] S1605: H-AMF sends a session establishment request to H-SMF.

[0496] Correspondingly, H-SMF receives a session establishment request from H-AMF.

[0497] Among them, if there is no association between H-AMF and H-SMF regarding the PDU session ID (PDU Session ID), the request type indication in S1605 is "initial request", and H-AMF calls Nsmf_PDUSession_CreateSMContext. If there is already an association between H-AMF and H-SMF regarding the PDU session ID (PDU Session ID), the request type indication in S1605 is "existing PDU session", and H-AMF calls Nsmf_PDUSession_UpdateSMContext.

[0498] Additionally, H-AMF needs to instruct H-SMF to establish a session in the VPLMN. In one possible implementation, HSMF may attach an indication message to the session establishment request, directly indicating that an additional session is required. In another possible implementation, H-AMF indicates to H-SMF that the UE is in a dual-connected state and a multi-path session is established, implicitly indicating that an additional session needs to be established in the VPLMN.

[0499] S1606: H-SMF sends a response message to H-AMF according to the session establishment request in S1605.

[0500] Correspondingly, H-AMF receives the response information from H-SMF.

[0501] S1607: The H-SMF selects a suitable H-UPF to serve the UE.

[0502] S1608: If H-AMF indicates an initial request to H-SMF in S1605, then H-SMF sends an N4 session establishment request to H-UPF. If H-AMF requests H-SMF to modify an existing session in S1605, then H-SMF sends an N4 session modification request to H-UPF.

[0503] S1609: H-UPF sends response information to H-SMF according to the request in S1608.

[0504] Correspondingly, H-SMF receives response information from H-UPF.

[0505] S1610: H-SMF sends a session establishment request to V-SMF, and sends H-UPF information to V-SMF.

[0506] Correspondingly, the V-MF receives the session establishment request from the H-SMF and the H-UPF information, which is used to establish a connection between the H-UPF and the V-UPF.

[0507] S1611: V-SMF selects a suitable V-UPF to serve the UE.

[0508] S1612: V-SMF sends an N4 session establishment request to V-UPF.

[0509] Correspondingly, the V-UPF receives an N4 session establishment request from the V-SMF. The N4 session establishment request may include information of the H-UPF, which is used to establish a connection between the H-UPF and the V-UPF.

[0510] After this step is completed, it can be considered that the path from V-UPF to H-UPF is established, and V-UPF can send uplink data to H-UPF.

[0511] S1613: V-UPF sends a response message to V-SMF according to the N4 session establishment request in S1612.

[0512] Correspondingly, V-SMF receives response information from V-UPF.

[0513] S1614: V-SMF sends a response message to H-SMF according to the session establishment request information in S1610.

[0514] Correspondingly, the H-SMF receives the response information from the V-SMF, wherein the response information may include the information of the V-UPF.

[0515] In addition, the H-SMF also needs to instruct the H-UPF to establish a connection in the VPLMN, that is, the H-UPF and the V-UPF need to establish a connection.

[0516] S1615: H-SMF sends an N4 session modification request to H-UPF.

[0517] Correspondingly, the H-UPF receives the N4 session modification request from the H-SMF, wherein the N4 session modification request may include V-UPF information for establishing an uplink from the V-UPF to the H-UPF.

[0518] After this step is completed, it can be considered that the path from H-UPF to V-UPF is established, and H-UPF can send downlink data to V-UPF.

[0519] S1616: H-UPF sends a response message to H-SMF according to the N4 session modification request in S1615.

[0520] Correspondingly, the H-SMF receives the response information from the H-UPF. The H-UPF can simultaneously feed back the HPLMN session information and the VPLMN session information to the H-SMF, such as the H-UPF information and the V-UPF information.

[0521] The following describes an implementation method for establishing a VPLMN session.

[0522] S1617~S1620 can be implemented with reference to S615~S618.

[0523] After completing S1620, the uplink establishment can be considered complete, and the UE can send an uplink data stream to the V-UPF.

[0524] S1621~S1623 can be implemented with reference to S619~S621.

[0525] After completing S1623, the downlink establishment can be considered complete, and the V-UPF can send downlink data flow to the UE.

[0526] S1624: V-SMF updates the session context to V-AMF.

[0527] The following describes an implementation method for establishing a HPLMN session.

[0528] S1625~S1628 can be implemented with reference to S508~S511.

[0529] After completing S1628, it can be considered that the uplink establishment is completed, and the UE can send an uplink data flow to the H-UPF.

[0530] S1629~S1631 can be implemented with reference to S512~S514.

[0531] After completing S1631, the downlink establishment can be considered complete, and the H-UPF can send the downlink data flow to the UE.

[0532] S1632: H-SMF updates the session context to H-AMF.

[0533] It should be noted that Fig.16 The operation of establishing a session in the HPLMN is placed after the operation of establishing a session in the VPLMN for exemplary purposes, and does not limit the order between the operation of establishing a session in the HPLMN and the operation of establishing a session in the VPLMN, and the two operations can be performed simultaneously.

[0534] It can be understood that the step of establishing a session in the HPLMN in the embodiment of the present application can be performed after S1616, and the H-SMF sends a request message to the H-AMF to initiate the session establishment process. The step of establishing a session in the VPLMN can be performed after S163, and the V-SMF sends a request message to the V-AMF to initiate the session establishment process.

[0535] exist Fig.16 The illustrated embodiment describes a scenario where a session is successfully established. For a scenario where a session is failed to be established, it may be that the UE fails to establish a session on the HPLMN side. In this case, the network should consider that the UE cannot obtain the service and refuse the UE to establish a session.

[0536] Based on the concept of the above embodiment, see Fig.17 The embodiment of the present application provides a communication device 1700, which includes a processing unit 1701 and a transceiver unit 1702. The device 1700 can be a communication device, or a device applied to a communication device and capable of supporting the communication device to execute a session establishment method.

[0537] Among them, the transceiver unit may also be referred to as a transceiver module, a transceiver, a transceiver, a transceiver device, etc. The processing unit may also be referred to as a processor, a processing board, a processing unit, a processing device, etc. Optionally, the device used to implement the receiving function in the transceiver unit may be regarded as a receiving unit. It should be understood that the transceiver unit is used to perform the sending operation and the receiving operation of the communication device in the above method embodiment, and the device used to implement the sending function in the transceiver unit is regarded as a sending unit, that is, the transceiver unit includes a receiving unit and a sending unit.

[0538] In addition, it should be noted that if the device is implemented using a chip / chip circuit, the transceiver unit can be an input-output circuit and / or a communication interface, performing input operations (corresponding to the aforementioned receiving operations) and output operations (corresponding to the aforementioned sending operations); the processing unit is an integrated processor or microprocessor or integrated circuit.

[0539] The following describes in detail an implementation method of applying the device 1700 to the first core network and the second core network.

[0540] Exemplarily, when the device 1700 is applied to the first core network, the operations performed by each unit thereof are described in detail.

[0541] In an optional implementation manner, the communication device 1700 can be applied to the first core network to execute the method executed by the first core network, for example, Figure 7 to Figure 16The method executed by the terminal device in the illustrated embodiment. It can be understood that the communication device 1700 can also be applied to various network elements in the first core network, such as AMF, SMF and UPF. Among them, the communication device 1700 can be located in the first PLMN. The transceiver unit 1702 is used to receive a first session establishment request from the terminal device and basic information required to establish a session in the second PLMN, and the first PLMN and the second PLMN are different. Among them, the first session establishment request includes first information, the first information indicates to establish a session of the terminal device in the first PLMN and the second PLMN, and the basic information is used by the second core network to establish a session of the terminal device in the second PLMN. The transceiver unit 1702 is also used to send a second session establishment request and basic information to the second core network, the second core network is located in the second PLMN, and the second session establishment request includes the first information. The processing unit 1701 is used to establish a session of the terminal device in the first PLMN.

[0542] Exemplarily, when the device 1700 is applied to the second core network, the operations performed by each unit thereof are described in detail.

[0543] In an optional implementation manner, the communication device 1700 can be applied to the second core network to execute the method executed by the second core network, for example, Figure 7 to Figure 16 The method executed by the second core network in the illustrated embodiment. It can be understood that the communication device 1700 can also be applied to various network elements in the second core network, such as AMF, SMF and UPF. Among them, the communication device 1700 can be located in the second PLMN. The transceiver unit 1702 is used to receive a second session establishment request from the first core network and the basic information required to establish a session in the second PLMN. Among them, the first core network is located in the first PLMN, the first PLMN and the second PLMN are different, the second session establishment request contains first information, the first information indicates to establish a session of the terminal device in the first PLMN and the second PLMN, and the basic information is used by the second core network to establish a session of the terminal device in the second PLMN. The processing unit 1701 is used to establish a session of the terminal device in the second PLMN.

[0544] Based on the concept of the embodiment, Fig.18 As shown, an embodiment of the present application provides a communication device 1800. The communication device 1800 includes a processor 1810. Optionally, the communication device 1800 may also include a memory 1820 for storing instructions executed by the processor 1810 or storing input data required by the processor 1810 to execute instructions or storing data generated after the processor 1810 executes instructions. The processor 1810 can implement the method shown in the above method embodiment through the instructions stored in the memory 1820.

[0545] Based on the concept of the embodiment, Fig.19 As shown, the embodiment of the present application provides a communication device 1900, which can be a chip or a chip system. Optionally, in the embodiment of the present application, the chip system can be composed of a chip, or can include a chip and other discrete devices.

[0546] The communication device 1900 may include at least one processor 1910, which is coupled to a memory. Optionally, the memory may be located inside or outside the device. For example, the communication device 1900 may also include at least one memory 1920. The memory 1920 stores the necessary computer programs, configuration information, computer programs or instructions and / or data for implementing any of the above embodiments; the processor 1910 may execute the computer program stored in the memory 1920 to complete the method in any of the above embodiments. Optionally, the memory may also be integrated with the processor.

[0547] The coupling in the embodiment of the present application is an indirect coupling or communication connection between devices, units or modules, which can be electrical, mechanical or other forms, and is used for information exchange between devices, units or modules. The processor 1910 may operate in conjunction with the memory 1920. The specific connection medium between the above-mentioned transceiver 1930, the processor 1910 and the memory 1920 is not limited in the embodiment of the present application.

[0548] The communication device 1900 may further include a transceiver 1930, and the communication device 1900 may exchange information with other devices through the transceiver 1930. The transceiver 1930 may be a circuit, a bus, a transceiver, or any other device that can be used for information exchange, or may be called a signal transceiver unit. Fig.19 As shown, the transceiver 1930 includes a transmitter 1931, a receiver 1932 and an antenna 1933. In addition, when the communication device 1900 is a chip-type device or circuit, the transceiver in the communication device 1900 may also be an input-output circuit and / or a communication interface, which may input data (or receive data) and output data (or send data), and the processor may be an integrated processor or a microprocessor or an integrated circuit, and the processor may determine output data according to input data.

[0549] In a possible implementation, the communication device 1900 can be applied to a communication device, and the specific communication device 1900 can be a communication device, or a device that can support a communication device to implement the functions of a terminal device or a network device in any of the above-mentioned embodiments. The memory 1920 stores the necessary computer programs, computer programs or instructions and / or data for implementing the functions of the first core network or the second core network in any of the above-mentioned embodiments. The processor 1910 can execute the computer program stored in the memory 1920 to complete the method executed by the terminal device or the network device in any of the above-mentioned embodiments.

[0550] Since the communication device 1900 provided in this embodiment can be applied to a terminal device or a network device to complete the method executed by the terminal device or the network device, the technical effects that can be obtained can refer to the above method embodiments and will not be repeated here.

[0551] In the embodiments of the present application, the processor may be a general-purpose processor, a digital signal processor, an application-specific integrated circuit, a field programmable gate array or other programmable logic device, a discrete gate or transistor logic device, or a discrete hardware component, and may implement or execute the methods, steps, and logic block diagrams disclosed in the embodiments of the present application. The general-purpose processor may be a microprocessor or any conventional processor, etc. The steps of the method disclosed in the embodiments of the present application may be directly embodied as being executed by a hardware processor, or may be executed by a combination of hardware and software modules in the processor.

[0552] In an embodiment of the present application, the memory may be a non-volatile memory, such as a hard disk drive (HDD) or a solid-state drive (SSD), etc., or a volatile memory (volatile memory), such as a random-access memory (RAM). The memory may also be any other medium that can be used to carry or store the desired program code in the form of an instruction or data structure and can be accessed by a computer, but is not limited thereto. The memory in an embodiment of the present application may also be a circuit or any other device that can implement a storage function, for storing a computer program, a computer program or an instruction and / or data.

[0553] Based on the above embodiments, see Fig. 20 The embodiment of the present application also provides another communication device 2000, including: an input-output interface 2010 and a logic circuit 2020; the input-output interface 2010 is used to receive code instructions and transmit them to the logic circuit 2020; the logic circuit 2020 is used to run code instructions to execute the method executed by the first core network or the second core network in any of the above embodiments.

[0554] The following describes in detail the operations performed by the device 2000 when applied to the first core network or the second core network.

[0555] In an optional implementation manner, the communication device 2000 can be applied to the first core network to execute the method executed by the first core network, for example, Figure 7 to Figure 16 The method executed by the first core network in the illustrated embodiment. It can be understood that the communication device 2000 can also be applied to various network elements in the first core network, such as AMF, SMF and UPF. Among them, the communication device 2000 can be located in the first PLMN. The input-output interface 2010 is used to input the first session establishment request from the terminal device and the basic information required to establish a session in the second PLMN, and the first PLMN and the second PLMN are different. Among them, the first session establishment request includes first information, the first information indicates to establish a session of the terminal device in the first PLMN and the second PLMN, and the basic information is used by the second core network to establish a session of the terminal device in the second PLMN. The input-output interface 2010 is also used to output the second session establishment request and basic information to the second core network, the second core network is located in the second PLMN, and the second session establishment request includes the first information. The logic circuit 2020 is used to establish a session of the terminal device in the first PLMN.

[0556] In an optional implementation manner, the communication device 2000 can be applied to the second core network to execute the method executed by the second core network, for example, Figure 7 to Figure 16 The method executed by the second core network in the illustrated embodiment. It can be understood that the communication device 2000 can also be applied to various network elements in the second core network, such as AMF, SMF and UPF. Among them, the communication device 2000 can be located in the second PLMN. The input-output interface 2010 is used to input the second session establishment request from the first core network and the basic information required to establish a session in the second PLMN. Among them, the first core network is located in the first PLMN, and the first PLMN and the second PLMN are different. The second session establishment request includes first information, and the first information indicates to establish a session of the terminal device in the first PLMN and the second PLMN, and the basic information is used by the second core network to establish a session of the terminal device in the second PLMN. The logic circuit 2020 is used to establish a session of the terminal device in the second PLMN.

[0557] Since the communication device 2000 provided in this embodiment can be applied to the first core network or the second core network, and executes the method executed by the first core network or the second core network, the technical effects that can be obtained can refer to the above method embodiments, and will not be repeated here.

[0558] Based on the above embodiments, the embodiments of the present application further provide a communication system, which includes at least one first core network and at least one second core network. Optionally, the communication system also includes at least one terminal device. The technical effects that can be obtained can refer to the above method embodiments, which will not be repeated here.

[0559] Based on the above embodiments, the embodiments of the present application further provide a computer-readable storage medium, which stores a computer program or instruction. When the instruction is executed, the method executed by the communication device in any of the above embodiments is implemented. The computer-readable storage medium may include: a USB flash drive, a mobile hard disk, a read-only memory, a random access memory, a magnetic disk or an optical disk, and other media that can store program codes.

[0560] In order to achieve the above Figures 17 to 20 In order to realize the functions of the communication device, the embodiment of the present application further provides a chip, including a processor, for supporting the communication device to realize the functions involved in the first core network or the second core network in the above method embodiment. In one possible design, the chip is connected to a memory or the chip includes a memory, and the memory is used to store computer programs or instructions and data necessary for the terminal device or network device.

[0561] Those skilled in the art will appreciate that the embodiments of the present application may be provided as methods, systems, or computer program products. Therefore, the present application may adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment in combination with software and hardware. Moreover, the present application may adopt the form of a computer program product implemented in one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) that include computer-usable program code.

[0562] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by a computer program or instruction. These computer programs or instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0563] These computer programs or instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer-readable memory produce a manufactured product including an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0564] These computer programs or instructions may also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for executing on the computer or other programmable device to implement the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0565] Obviously, those skilled in the art can make various changes and modifications to the embodiments of the present application without departing from the scope of the embodiments of the present application. Thus, if these modifications and variations of the embodiments of the present application fall within the scope of the claims of the present application and their equivalents, the present application is also intended to include these modifications and variations.

Claims

1. A session establishment method, characterized in that: Applied to a first core network, the first core network is located in a first public land mobile network PLMN, the method comprising: receiving a first session establishment request from a terminal device and basic information required for establishing a session in a second PLMN, wherein the first session establishment request includes first information, wherein the first information indicates that a session of the terminal device is established in the first PLMN and the second PLMN, and the second PLMN is different from the first PLMN; Sending a second session establishment request and the basic information to a second core network, where the second core network is located in the second PLMN, the second session establishment request includes the first information, and the basic information is used by the second core network to establish a session of the terminal device in the second PLMN; Establishing a session for the terminal device in the first PLMN.

2. The method according to claim 1, characterized in that The first PLMN is a home public land mobile network HPLMN, the second PLMN is a visited public land mobile network VPLMN, the first core network includes a first access and mobility management function device, and the second core network includes a second access and mobility management function device.

3. The method according to claim 2, characterized in that The first core network further includes a first session management function device and a first user plane function device, the second core network further includes a second session management function device and a second user plane function device, and the receiving a first session establishment request from the terminal device includes: The first access and mobility management function device receives a first session establishment request from the terminal device; The sending the second session establishment request and the basic information to the second core network includes: The first access and mobility management function device sends the second session establishment request to the second access and mobility management function device; The method further comprises: The second session establishment request also includes information of the first session management function device, the information of the first session management function device is used by the second session management function device to send a third session establishment request to the first session management function device, the third session establishment request includes information of the second user plane function device and the first information, and the third session establishment request is used to request to establish a connection between the first user plane function device and the second user plane function device; The first session management function device receives the third session establishment request from the second session management function device; The first session management function device sends information of the second user plane function device to the first user plane function device, requesting the first user plane function device to establish a connection between the first user plane function device and the second user plane function device; The first user plane function device establishes a connection with the second user plane function device based on the information of the second user plane function device; The establishing a session of the terminal device in the first PLMN includes: The first user plane functional device establishes a connection with the terminal device based on the first information.

4. The method according to claim 3, characterized in that: Also includes: The first user plane function device sends information about the first user plane function device and information about the second user plane function device to the first session management function device.

5. The method according to claim 1, characterized in that The first PLMN is a VPLMN, the second PLMN is a HPLMN, the first core network includes a first access and mobility management function device and a first session management function device, and the second core network includes a second session management function device; The receiving a first session establishment request from a terminal device includes: The first access and mobility management function device receives the first session establishment request; The first access and mobility management function device sends a fourth session establishment request to the first session management function device, where the fourth session establishment request includes the first information; The sending a second session establishment request to the second core network includes: The first session management function device sends the second session establishment request to the second session management function device.

6. The method according to any one of claims 1 to 5, characterized in that: The first information includes one or more of indication information for instructing the terminal device to establish a session in the second PLMN, a session establishment request type, identification information of the second PLMN, a temporary identification of the terminal device in the second PLMN, and an identification of the second core network.

7. The method according to any one of claims 1 to 6, characterized in that: The first session establishment request also includes identification information of the second core network, or information of the second core network is obtained from context information of the terminal device.

8. A session establishment method, characterized in that: Applied to a second core network, the second core network is located in a second public land network PLMN, the method comprising: receiving a second session establishment request from a first core network and basic information required for establishing a session in the second PLMN, where the first core network is located in a first PLMN, the second PLMN is different from the first PLMN, the second session establishment request includes first information, the first information indicates that a session of the terminal device is established in the first PLMN and the second PLMN, and the basic information is used by the second core network to establish the session of the terminal device in the second PLMN; Establish a session for the terminal device in the second PLMN.

9. The method according to claim 8, characterized in that The first PLMN is a home public land network HPLMN, the second PLMN is a visited public land network VPLMN, the first core network includes a first access and mobility management function access and mobility management function device, and the second core network includes a second access and mobility management function device.

10. The method according to claim 9, characterized in that The first core network further includes a first session management function device and a first user plane function device, the second core network further includes a second session management function device and a second user plane function device, and the receiving a second session establishment request from the first core network includes: The second access and mobility management function device receives the second session establishment request from the first access and mobility management function device; The method further comprises: The second session establishment request includes information of the first session management function device, and the second access and mobility management function device sends the first information and information of the first session management function device to the second session management function device; The second session management function device sends a third session establishment request to the first session management function device, wherein the third session establishment request includes information of the second user plane function device and the first information, and the third session establishment request is used to request establishment of a connection between the first user plane function device and the second user plane function device.

11. The method according to claim 10, characterized in that The establishing a connection with the terminal device in the second PLMN includes: The second session management function device sends a fifth session establishment request to the second user plane function device, where the fifth session establishment request is used to request the second user plane function device to establish a connection with the terminal device; The second user plane function device establishes a connection with the terminal device.

12. The method according to claim 8, characterized in that The first core network includes a first session management function device, the second core network includes a second session management function device and a second user plane function device, and further includes: The second session management function device sends the first information to the second user plane function device, requesting the second user plane function device to establish a connection with the terminal device; The second user plane function device establishes a connection with the terminal device.

13. The method according to claim 12, characterized in that Also includes: The second user plane function device sends information about the first user plane function device and information about the second user plane function device to the second session management function device.

14. The method according to any one of claims 8 to 13, characterized in that: The first information includes one or more of indication information for instructing the terminal device to establish a session in the second PLMN, a session establishment request type, identification information of the second PLMN, a temporary identification of the terminal device in the second PLMN, and an identification of the second core network.

15. The method according to any one of claims 8 to 14, characterized in that: The second session establishment request also includes identification information of the second core network, or information of the second core network is obtained from context information of the terminal device.

16. A session establishment method, characterized in that: Applied to a first core network, the first core network is located in a first public land network PLMN, the method includes: receiving a first session establishment request from a terminal device and basic information required for establishing a session with a second PLMN, wherein the first session establishment request includes first information, and the first information indicates that a session of the terminal device is established in the first PLMN and the second PLMN, and the second PLMN is different from the first PLMN; Sending a second session establishment request and the basic information to a second core network, where the second core network is located in the second PLMN, the second session establishment request includes the first information, and the basic information is used by the second core network to establish a session of the terminal device in the second PLMN; Receiving first response information of the second session establishment request from the second core network, where the first response information indicates that establishment of the session of the terminal device fails; Send the first response information to the terminal device.

17. The method according to claim 16, characterized in that The first PLMN is a home public land network HPLMN, the second PLMN is a visited public land network VPLMN, the first core network includes a first access and mobility management function device, and the second core network includes a second access and mobility management function device.

18. The method according to claim 17, characterized in that The first core network further includes a first session management function device and a first user plane function device, the second core network further includes a second session management function device and a second user plane function device, and the receiving a first session establishment request from the terminal device includes: The first access and mobility management function device receives a first session establishment request from the terminal device; The sending the second session establishment request and the basic information to the second core network includes: The first access and mobility management function device sends the second session establishment request to the second access and mobility management function device; The method further comprises: The second session establishment request also includes information of the first session management function device, the information of the first session management function device is used by the second session management function device to send a third session establishment request to the first session management function device, the third session establishment request includes information of the second user plane function device and the first information, and the third session establishment request is used to request to establish a connection between the first user plane function device and the second user plane function device; The first session management function device receives the third session establishment request from the second session management function device; The first session management function device sends information of the second user plane function device to the first user plane function device, requesting the first user plane function device to establish a connection with the second user plane function device.

19. The method according to claim 18, characterized in that The receiving first response information from the second core network includes: The first user plane function device sends second response information to the first session management function device, where the second response information indicates that establishment of a session of the terminal device in the first PLMN fails; The first user plane function device sends third response information to the second user plane function device, where the third response information indicates that the session establishment of the terminal device in the first PLMN fails, and the third response information is further used to instruct the second user plane function device not to establish the session of the terminal device in the second PLMN; The first access and mobility management function device receives the first response information from the second access and mobility management function device; The sending, to the terminal device, information that establishment of a session of the terminal device fails, includes: The first access and mobility management function device sends the first response information to the terminal device.

20. The method according to claim 19, characterized in that The second response information includes first indication information, where the first indication information indicates that establishment of a session of the terminal device in the first PLMN fails, or the second response information does not include information of the first user plane functional device.

21. The method according to any one of claims 18 to 20, characterized in that: The first response information also indicates that establishment of a session for the terminal device in the first PLMN fails.

22. The method according to claim 18, characterized in that The receiving first response information from the second core network includes: The first user plane function device sends second response information to the first session management function device, where the second response information indicates that establishment of a session of the terminal device in the second PLMN fails; The first session management function device sends fourth response information to the second session management function device, where the fourth response information indicates that establishment of a session of the terminal device in the second PLMN fails; The first access and mobility management function device receives the first response information from the second access and mobility management function device; The sending, to the terminal device, information that establishment of a session of the terminal device fails, includes: The first access and mobility management function device sends the first response information to the terminal device.

23. The method according to claim 22, characterized in that The second response information includes second indication information, where the second indication information indicates that establishment of a session of the terminal device in the second PLMN fails, or the fourth response information does not include information of a second user plane functional device.

24. The method according to claim 22 or 23, characterized in that The first response information also indicates that establishment of a session for the terminal device in the second PLMN fails.

25. The method according to any one of claims 22 to 24, characterized in that: Also includes: Establish a session for the first terminal device in the first PLMN.

26. A communication device, characterized in that: The method comprises a unit for executing the method according to any one of claims 1 to 7, or comprises a unit for executing the method according to any one of claims 8 to 15, or comprises a unit for executing the method according to any one of claims 16 to 25.

27. A communication device, characterized in that: include: Processor and memory; The memory is used to store computer programs or instructions; The processor is used to execute the computer program or instructions in the memory, so that the device performs the method according to any one of claims 1 to 7, or the method according to any one of claims 8 to 15, or the method according to any one of claims 16 to 25.

28. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores computer-executable instructions, which, when called by an electronic device, cause the electronic device to execute the method as described in any one of claims 1 to 7, or cause the electronic device to execute the method as described in any one of claims 8 to 15, or cause the electronic device to execute the method as described in any one of claims 16 to 25.

29. A computer program product, characterized in that The method comprises computer execution instructions, which, when executed on a computer, enable the computer to execute the method according to any one of claims 1 to 7, enable the computer to execute the method according to any one of claims 8 to 15, or enable the computer to execute the method according to any one of claims 16 to 25.

30. A chip system, characterized in that: The chip system comprises: Communication interface; A processor, used to call and run the instruction through the communication interface, so that the device installed with the chip system executes the method as described in any one of claims 1 to 7, or the device installed with the chip system executes the method as described in any one of claims 8 to 15, or the device installed with the chip system executes the method as described in any one of claims 16 to 25.

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