Network switching method and apparatus

Abstract

A network switching method and apparatus, relating to the technical field of communications, and capable of supporting a terminal device to switch between different visited networks, and ensuring the service continuity of the terminal device during the switching process, improving the communication performance. The method comprises: a first session management network element of a first network receiving a first request from a first mobility management network element of the first network, wherein the first request is used for requesting to establish a session for a terminal device, the first request comprises identification information of a second session management network element of a second network, and the second network is a home network of the terminal device; and sending to the second session management network element a second request for requesting to acquire context information of the terminal device, receiving a second response from the second session management network element, and establishing a session for the terminal device on the basis of the second response, wherein the second response comprises the context information of the terminal device stored in a third session management network element, and the third session management network element is a network element, that establishes a session for the terminal device, in a third network.

Description

Network switching method and device

[0001] This application claims priority to the Chinese patent application filed with the State Intellectual Property Office on July 31, 2023, with application number 202310955224.7 and application name “Network Switching Method and Device”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application relates to the field of communication technology, and in particular to a network switching method and device. Background Art

[0003] In the communication system, the core network and access network can be deployed based on the network sharing mechanism, that is, the shared access network can be allowed to access different core networks respectively, so as to realize the sharing of access network resources between operators, improve network quality and reduce network deployment costs.

[0004] The shared access network and the core network may be directly connected or indirectly connected. For example, the shared access network may be directly connected to the core network 1, or indirectly connected to the core network 2 via the core network 1.

[0005] Based on the aforementioned network sharing mechanism, a terminal device can access a home network (such as core network 2) via a visited network (such as core network 1) over a shared access network. When a terminal device needs to switch from accessing the home network via visited network 1 to accessing the home network via visited network 2 during mobility, if there is no connectivity between visited networks 1 and 2, how can the terminal device switch from visited network 1 to visited network 2 while ensuring service continuity during the handover? This is a pressing technical issue to be addressed.

[0006] Summary of the Invention

[0007] The embodiments of the present application provide a network switching method and apparatus that can support terminal devices to switch between different visited networks, while ensuring service continuity of the terminal devices during the switching process and improving communication performance.

[0008] In a first aspect, an embodiment of the present application provides a network switching method, wherein the execution subject of the method can be a first session management network element of a first network, or a chip, a chip system, or a system on chip of the first session management network element. The method comprises: receiving a first request from a first mobility management network element of the first network, the first request being used to request establishment of a session for a terminal device, the first request including identification information of a second session management network element of a second network, the second network being the home network of the terminal device; sending a second request to the second session management network element, receiving a second response from the second session management network element, and establishing a session for the terminal device based on the second response; wherein the second request is used to request acquisition of context information of the terminal device, the second response including context information of the terminal device stored in a third session management network element, the third session management network element being a network element in a third network that establishes a session for the terminal device.

[0009] Based on the first aspect, when the terminal device needs to switch from the third network to the first network, the second session management network element of the terminal device's home network (i.e., the second network) can assist the first session management network element in obtaining the context information of the terminal device stored in the third session management network element. Then, the second session management network element can establish a session for the terminal device based on the context information of the terminal device, thereby realizing the switching of the terminal device between different visited networks (i.e., realizing the switching of the terminal device between the third network and the first network), while ensuring the business continuity of the terminal device during the switching process and improving communication performance.

[0010] In one possible design, the first request also includes one or more of the following: identification information of the session established by the third network for the terminal device, and identification information of the third session management network element.

[0011] In one possible design, the second request includes one or more of the following: identification information of the session established by the third network for the terminal device, and identification information of the third session management network element.

[0012] Based on the above two possible designs, by carrying the identification information of the session established by the third network for the terminal device and / or the identification information of the third session management network element in the first request and the second request, the second session management network element can determine the corresponding third session management network element based on the identification information of the session or the identification information of the third session management network element, and then obtain the context information of the terminal device.

[0013] In one possible design, a session is established for the terminal device based on the second response, including: obtaining first tunnel information and second tunnel information, sending the first tunnel information to the first user plane network element, and sending a first response to the first mobility management network element; wherein the second response includes the first tunnel information and the second tunnel information, the first response includes the second tunnel information, and the first tunnel information is used to establish a data forwarding tunnel between the first user plane network element of the first network and the second user plane network element of the second network.

[0014] In one possible design, the second tunnel information is used to establish an uplink data forwarding tunnel between a source access network device of a third network and a third user plane network element of the third network.

[0015] Based on the two possible designs described above, forwarding the first tunnel information facilitates communication between the first user plane network element and the second user plane network element via the first tunnel information. Forwarding the second tunnel information facilitates communication between the source access network device and the third user plane network element via the second tunnel information. This facilitates the subsequent establishment of a data forwarding tunnel between the source access network device, the third user plane network element, the second user plane network element, and the first user plane network element, allowing the source access network device to subsequently send service data of the terminal device to the first user plane network element via the third user plane network element and the second user plane network element, thereby ensuring service continuity for the terminal device during the handover process.

[0016] In a second aspect, an embodiment of the present application provides a network switching method, wherein the execution subject of the method can be a first mobility management network element of a first network, or a chip, chip system, or system-on-chip of the first mobility management network element. The method includes: receiving a third request from a second mobility management network element of a second network; the third request is used to request switching a terminal device from the third network to the first network, where the second network is the home network of the terminal device; obtaining identification information of a second session management network element of the second network; and sending a first request to the first session management network element of the first network; wherein the first request is used to request establishment of a session for the terminal device, and the first request includes identification information of the second session management network element.

[0017] Based on the second aspect, when the terminal device needs to switch from the third network to the first network, the second mobility management network element of the terminal device's home network (i.e., the second network) can assist the third mobility management network element of the third network to pass the terminal device's network switching request to the first mobility management network element of the first network. Then, the first mobility management network element can request the first session management network element to establish a session for the terminal device, thereby realizing the switching of the terminal device between the third network and the first network, while ensuring the business continuity of the terminal device during the switching process and improving communication performance.

[0018] In one possible design, obtaining the identification information of the second session management network element of the second network includes: determining the identification information of the second session management network element based on a third request; wherein the third request includes the identification information of the second session management network element; or, the third request includes network slice information, and determining the identification information of the second session management network element based on the network slice information; or, randomly determining the identification information of the second session management network element based on a preset configuration.

[0019] Based on this possible design, the first mobility management network element can adopt one or more of the above methods to select a second session management network element that can assist the terminal device in network switching, so that the first session management network element can obtain the context information of the terminal device stored in the third session management network element through the second session management network element selected by the first mobility management network element, thereby ensuring the service continuity of the terminal device during the switching process and improving communication performance.

[0020] In one possible design, the third request includes global identification information of the target access network device, and before sending the first request to the first session management network element of the first network, the method also includes: determining the first session management network element based on the global identification information of the target access network device; or, the third request includes network slice information; before sending the first request to the first session management network element of the first network, the method also includes: determining the first session management network element based on the network slice information.

[0021] Based on this possible design, the first mobility management network element can adopt any of the above methods to select a suitable first session management network element for the terminal device to better provide network services for the terminal device and improve communication performance.

[0022] In one possible design, the third request also includes one or more of the following: identification information of the session established by the third network for the terminal device, and identification information of the third session management network element of the third network.

[0023] In one possible design, the first request also includes one or more of the following: identification information of the session established by the third network for the terminal device, and identification information of the third session management network element of the third network.

[0024] Based on the above two possible designs, by carrying the identification information of the session established by the third network for the terminal device and / or the identification information of the third session management network element in the third request and the first request, the second session management network element can determine the corresponding third session management network element based on the identification information of the session or the identification information of the third session management network element, and then obtain the context information of the terminal device.

[0025] In one possible design, a first response is received from a first session management network element; wherein the first response includes second tunnel information; and a third response is sent to a second mobility management network element; wherein the third response is used to indicate that the first network allows the terminal device to switch from the third network to the first network, and the third response includes identification information of the first mobility management network element and the second tunnel information.

[0026] In one possible design, the second tunnel information is used to establish an uplink data forwarding tunnel between a source access network device of a third network and a third user plane network element of the third network.

[0027] Based on the two possible designs described above, forwarding the second tunnel information facilitates communication between the source access network device and the third user plane network element via the second tunnel information. This facilitates the subsequent establishment of a data forwarding tunnel between the source access network device, the third user plane network element, the second user plane network element, and the first user plane network element. This facilitates the subsequent transmission of service data of the terminal device by the source access network device to the first user plane network element via the third user plane network element and the second user plane network element, thereby ensuring service continuity for the terminal device during the handover process.

[0028] In a third aspect, an embodiment of the present application provides a network switching method, wherein the execution subject of the method can be a second mobility management network element of a second network, or a chip, chip system, or system-on-chip of the second mobility management network element. The method includes: receiving a fourth request from a third mobility management network element of a third network; wherein the fourth request is used to request switching of a terminal device from the third network to a first network, and the second network is a home network of the terminal device; obtaining identification information of a second session management network element of the second network; and sending a third request to a first mobility management network element of the first network; wherein the third request is used to request switching of the terminal device from the third network to the first network, and the third request includes identification information of the second session management network element.

[0029] Based on the third aspect, when the terminal device needs to switch from the third network to the first network, the second mobility management network element of the terminal device's home network (i.e., the second network) can assist the third mobility management network element of the third network to pass the terminal device's network switching request to the first mobility management network element of the first network, and then the first network establishes a session for the terminal device to realize the switching of the terminal device between the third network and the first network, while ensuring the business continuity of the terminal device during the switching process and improving communication performance.

[0030] In one possible design, obtaining identification information of a second session management network element of a second network includes: determining the identification information of the second session management network element according to a fourth request; wherein the fourth request includes the identification information of the second session management network element; or, the fourth request includes identification information of a session established by a third network for a terminal device, and determining, according to the identification information of the session, the identification information of the second session management network element from a pre-stored association between identification information of the session and identification information of the second session management network element; or, sending identification information of the session established by the third network for the terminal device to a third session management network element of the third network, and receiving identification information of the second session management network element corresponding to the session from the third session management network element; or, sending identification information of the session established by the third network for the terminal device to a second unified data management network element of the second network, and receiving identification information of the second session management network element corresponding to the session from the second unified data management network element; or, randomly determining the identification information of the second session management network element according to a preset configuration.

[0031] Based on this possible design, the second mobility management network element can adopt any of the above methods to select a second session management network element that can assist the terminal device in network switching, so that the first session management network element can subsequently obtain the context information of the terminal device stored in the third session management network element through the second session management network element selected by the second mobility management network element, thereby ensuring the service continuity of the terminal device during the switching process and improving communication performance.

[0032] In one possible design, the fourth request also includes first identification information and global identification information of the target access network device; wherein, the first identification information is identification information allocated by the third network to the terminal device of the second network for accessing the third network, and the global identification information of the target access network device includes second identification information, and the second identification information is identification information allocated by the first network to the terminal device of the first network for accessing the first network.

[0033] In one possible design, when the first identification information and the second identification information indicate that the terminal device switches from the third network to the first network, a third request is sent to the first mobility management network element.

[0034] Based on the two possible designs described above, the second mobility management network element can determine, based on the first identification information, that the terminal device is a roaming user on an inter-network. Based on the first identification information and the second identification information, the second mobility management network element can determine that the inter-network roaming terminal device is switching from the third network to the first network. If the second mobility management network element supports switching of the inter-network roaming terminal device from the third network to the first network, the second mobility management network element can send a third request to the first mobility management network element of the first network.

[0035] In one possible design, before sending a third request to the first mobility management network element of the first network, the method also includes: determining the first mobility management network element based on the second identification information; or, sending a service discovery request to the second topology management network element of the second network, receiving a service discovery response from the second topology management network element, and determining the first mobility management network element based on the service discovery response; wherein, the service discovery request includes the global identification information of the target access network device, the service discovery request is used to request discovery of the mobility management network element associated with the target access network device, and the service discovery response includes the identification information of the first mobility management network element.

[0036] Based on this possible design, the second mobility management network element can adopt any of the above methods to select a suitable first mobility management network element for the terminal device to better provide network services for the terminal device and improve communication performance.

[0037] In one possible design, the third request includes third identification information, where the third identification information is identification information allocated by the first network to the terminal device of the second network for accessing the first network.

[0038] Based on this possible design, the second mobility management network element may determine the third identification information when determining to send the third request to the first mobility management network element, and send the third request to the first mobility management network element using the third identification information.

[0039] In one possible design, the fourth request also includes one or more of the following: network slice information, global identification information of the target access network device, and identification information of the third session management network element of the third network.

[0040] In one possible design, the third request also includes one or more of the following: network slice information, global identification information of the target access network device, and identification information of the third session management network element of the third network.

[0041] Based on the two possible designs described above, by carrying network slicing information, network elements in the second network and the first network can determine the network elements participating in the network switching process (such as determining the second session management network element, the first session management network element, etc.) based on the network slicing information, so as to better provide network services for the terminal device and improve communication performance. By carrying the global identification information of the target access network device, each network can be facilitated to determine the network to which the terminal device is to switch, and network elements in the second network and the first network can be facilitated to determine the network elements participating in the network switching process (such as determining the second session management network element, the first mobility management network element, the first session management network element, etc.) based on the network slicing information, so as to better provide network services for the terminal device and improve communication performance. By carrying the identification information of the third session management network element, the second session management network element can be facilitated to determine the corresponding third session management network element based on the identification information of the third session management network element, and then obtain the context information of the terminal device.

[0042] In one possible design, a third response is received from the first mobility management network element; wherein the third response is used to indicate that the first network allows the terminal device to switch from the third network to the first network, and the third response includes identification information of the first mobility management network element and the second tunnel information; a fourth response is sent to the third mobility management network element; wherein the fourth response is used to indicate that the first network allows the terminal device to switch from the third network to the first network, and the fourth response includes identification information of the first mobility management network element and the second tunnel information.

[0043] In one possible design, the second tunnel information is used to establish an uplink data forwarding tunnel between a source access network device of a third network and a third user plane network element of the third network.

[0044] Based on the two possible designs described above, forwarding the second tunnel information facilitates communication between the source access network device and the third user plane network element via the second tunnel information. This facilitates the subsequent establishment of a data forwarding tunnel between the source access network device, the third user plane network element, the second user plane network element, and the first user plane network element. This facilitates the subsequent transmission of service data of the terminal device by the source access network device to the first user plane network element via the third user plane network element and the second user plane network element, thereby ensuring service continuity for the terminal device during the handover process.

[0045] In a fourth aspect, an embodiment of the present application provides a network switching method, the execution subject of which can be a second session management network element of a second network, or a chip, chip system, or system on chip of the second session management network element. The method includes: receiving a second request from a first session management network element of a first network; wherein the second request is used to request to obtain context information of a terminal device, and the second network is a home network of the terminal device; sending a fifth request to a third session management network element of a third network; wherein the third session management network element is a network element in the third network that establishes a session for the terminal device, and the fifth request is used to request to obtain context information of the terminal device; receiving a fifth response from the third session management network element; wherein the fifth response includes the context information of the terminal device stored in the third session management network element; and sending a second response to the first session management network element; wherein the second response includes the context information of the terminal device stored in the third session management network element.

[0046] Based on the fourth aspect, when the terminal device needs to switch from the third network to the first network, the second session management network element of the terminal device's home network (i.e., the second network) can assist the first session management network element in obtaining the context information of the terminal device stored in the third session management network element, so that the second session management network element can establish a session for the terminal device based on the context information of the terminal device, realize the switching of the terminal device between different visited networks (i.e., realize the switching of the terminal device between the third network and the first network), and at the same time ensure the business continuity of the terminal device during the switching process and improve communication performance.

[0047] In one possible design, the second request includes one or more of the following: identification information of the session established by the third network for the terminal device, and identification information of the third session management network element.

[0048] Based on this possible design, by carrying the identification information of the session established by the third network for the terminal device and / or the identification information of the third session management network element in the second request, the second session management network element can determine the corresponding third session management network element based on the identification information of the session or the identification information of the third session management network element, and then obtain the context information of the terminal device.

[0049] In one possible design, the second tunnel information and the third tunnel information are obtained; the first tunnel information and the fourth tunnel information are received from the second user plane network element of the second network; wherein the fifth response includes the second tunnel information and the third tunnel information, the first tunnel information is used to establish a data forwarding tunnel between the first user plane network element of the first network and the second user plane network element of the second network, and the third tunnel information and the fourth tunnel information are used to establish a data forwarding tunnel between the second user plane network element and the third user plane network element; the first tunnel information and the second tunnel information are sent to the first session management network element; the third tunnel information is sent to the second user plane network element; and the fourth tunnel information is sent to the third session management network element of the third network.

[0050] In one possible design, the second tunnel information is used to establish an uplink data forwarding tunnel between a source access network device of a third network and a third user plane network element of the third network.

[0051] Based on the two possible designs described above, forwarding the first tunnel information can facilitate the first user plane network element to communicate with the second user plane network element through the first tunnel information, and forwarding the second tunnel information can facilitate the source access network device to communicate with the third user plane network element through the second tunnel information. Forwarding the third tunnel information and the fourth tunnel information can facilitate communication between the second user plane network element and the third user plane network element. This further facilitates the subsequent establishment of a data forwarding tunnel between the source access network device, the third user plane network element, the second user plane network element, and the first user plane network element, and facilitates the subsequent source access network device to send the service data of the terminal device to the first user plane network element through the third user plane network element and the second user plane network element, thereby ensuring the service continuity of the terminal device during the switching process.

[0052] In a fifth aspect, an embodiment of the present application provides a network switching method, the execution subject of which can be a third mobility management network element of a third network, or a chip, chip system, or system on chip of the third mobility management network element. The method includes: receiving a switching request from a terminal device; wherein the switching request includes global identification information of a target access network device, and the switching request is used to request switching to the target access network device; according to the switching request, obtaining identification information of a second session management network element of a second network; wherein the second network is a home network of the terminal device; sending a fourth request to the second mobility management network element of the second network; wherein the fourth request is used to request switching the terminal device from the third network to the first network, and the fourth request includes identification information of the second session management network element.

[0053] Based on the fifth aspect, when the terminal device needs to switch from the third network to the first network, the second mobility management network element of the terminal device's home network (i.e., the second network) can assist the third mobility management network element of the third network to pass the terminal device's switching request to the first network. By carrying the identification information of the second session management network element in the fourth request, the first session management network element of the first network can request the context information of the terminal device from the second session management network element, and then establish a session for the terminal device, thereby realizing the switching of the terminal device between the third network and the first network, while ensuring the business continuity of the terminal device during the switching process and improving communication performance.

[0054] In one possible design, obtaining identification information of a second session management network element of the second network includes: determining the identification information of the second session management network element from an association between pre-stored session identification information and identification information of the second session management network element based on identification information of a session established by a third network for a terminal device; or, sending identification information of a session established by the third network for a terminal device to a third session management network element of the third network, and receiving identification information of the second session management network element from the third session management network element; or, sending identification information of a session established by the third network for a terminal device to a unified data management network element, and receiving identification information of the second session management network element from the unified data management network element; wherein the unified data management network element is a third unified data management network element of the third network, or the unified data management network element is a second unified data management network element of the second network.

[0055] Based on this possible design, the third mobility management network element can adopt any of the above methods to select a second session management network element that can assist the terminal device in network switching, so that the first session management network element can obtain the context information of the terminal device stored in the third session management network element through the second session management network element selected by the third mobility management network element, thereby ensuring the service continuity of the terminal device during the switching process and improving communication performance.

[0056] In one possible design, the fourth request also includes first identification information and global identification information of the target access network device; wherein, the first identification information is identification information allocated by the third network to the terminal device of the second network for accessing the third network, and the global identification information of the target access network device includes second identification information, and the second identification information is identification information allocated by the first network to the terminal device of the first network for accessing the first network.

[0057] Based on this possible design, by carrying the first identification information and the global identification information of the target access network device in the fourth request, the second mobility management network element can forward the network switching request of the terminal device to the first mobility management network element of the first network when it determines that the terminal device roaming on a different network requests to switch from the third network to the first network.

[0058] In one possible design, a fourth response is received from the second mobility management network element; wherein the fourth response is used to indicate that the first network allows the terminal device to switch from the third network to the first network, and the fourth response includes identification information of the first mobility management network element of the first network and second tunnel information, and the second tunnel information is used to establish an uplink data forwarding tunnel between the source access network device of the third network and the third user plane network element of the third network; and the second tunnel information is sent to the source access network device of the terminal device.

[0059] Based on this possible design, forwarding the second tunnel information facilitates communication between the source access network device and the third user plane network element via the second tunnel information. This further facilitates the subsequent establishment of a data forwarding tunnel between the source access network device, the third user plane network element, the second user plane network element, and the first user plane network element. This facilitates the subsequent transmission of service data of the terminal device by the source access network device to the first user plane network element via the third user plane network element and the second user plane network element, thereby ensuring service continuity for the terminal device during the handover process.

[0060] In a sixth aspect, embodiments of the present application provide a network switching method, which can be performed by a second user plane network element of a second network, or by a chip, chip system, or system-on-chip of the second user plane network element. The method includes: receiving service data of a terminal device from a third user plane network element of a third network; wherein the second network is the home network of the terminal device; determining a first user plane network element of a first network based on the service data of the terminal device; and sending the service data of the terminal device to the first user plane network element of the first network.

[0061] Based on the sixth aspect, when the terminal device needs to switch from the third network to the first network, the second user plane network element of the terminal device's home network (i.e., the second network) can assist the first user plane network element to obtain the service data of the terminal device sent by the source access network device to the third user plane network element. While realizing the switching of the terminal device between different visited networks (i.e., realizing the switching of the terminal device between the third network and the first network), it ensures the service continuity of the terminal device during the switching process and improves the communication performance.

[0062] In one possible design, receiving service data of a terminal device from a third user plane network element of a third network includes: sending fourth tunnel information to a second session management network element of a second network; wherein the fourth tunnel information is used to establish an uplink data forwarding tunnel between the second user plane network element and the third user plane network element; and receiving service data of the terminal device sent by the third user plane network element according to the fourth tunnel information.

[0063] In one possible design, the service data of the terminal device is sent to the first user plane network element of the first network, including: receiving fifth tunnel information from the second session management network element of the second network; wherein the fifth tunnel information is used to establish an uplink data forwarding tunnel between the first user plane network element and the second user plane network element; and sending the service data of the terminal device to the first user plane network element according to the fifth tunnel information.

[0064] Based on the above two possible designs, the second user plane network element can forward the service data of the terminal device according to the tunnel information, ensure the service continuity of the terminal device during the switching process, and improve communication performance.

[0065] In a seventh aspect, an embodiment of the present application provides a communication device, which can be applied to the first session management network element of the first network of the first aspect above to implement the functions performed by the first session management network element above. The communication device can be the first session management network element, or it can be a chip, chip system, or system on chip of the first session management network element. The communication device can perform the functions performed by the first session management network element above through hardware, or it can perform corresponding software implementation through hardware. The hardware or software includes one or more modules corresponding to the above functions. For example, a transceiver module and a processing module. The transceiver module can independently complete the following transceiver operations, or it can cooperate with the processing module to complete the following transceiver operations; accordingly, the processing module can also independently complete the following processing operations, or it can cooperate with the transceiver module to complete the following processing operations, without limitation.

[0066] Among them, the transceiver module is used to receive a first request from a first mobility management network element of a first network, where the first request is used to request to establish a session for the terminal device, and the first request includes identification information of a second session management network element of a second network, where the second network is the home network of the terminal device; the transceiver module is also used to send a second request to the second session management network element and receive a second response from the second session management network element, and the processing module is used to establish a session for the terminal device based on the second response; wherein the second request is used to request to obtain context information of the terminal device, and the second response includes context information of the terminal device stored in a third session management network element, where the third session management network element is a network element in the third network that establishes a session for the terminal device.

[0067] In one possible design, the first request also includes one or more of the following: identification information of the session established by the third network for the terminal device, and identification information of the third session management network element.

[0068] In one possible design, the second request includes one or more of the following: identification information of the session established by the third network for the terminal device, and identification information of the third session management network element.

[0069] In one possible design, the processing module is specifically used to obtain the first tunnel information and the second tunnel information, and the transceiver module is also used to send the first tunnel information to the first user plane network element and send a first response to the first mobility management network element; wherein the first response includes the first tunnel information and the second tunnel information, the first response includes the second tunnel information, and the first tunnel information is used to establish a data forwarding tunnel between the first user plane network element of the first network and the second user plane network element of the second network.

[0070] In one possible design, the second tunnel information is used to establish an uplink data forwarding tunnel between a source access network device of a third network and a third user plane network element of the third network.

[0071] Among them, the technical effects brought about by the above-mentioned seventh aspect or any possible design in the seventh aspect can be referred to the technical effects brought about by the above-mentioned first aspect or any possible design in the first aspect, and will not be repeated here.

[0072] In an eighth aspect, an embodiment of the present application provides a communication device, which can be applied to the first mobility management network element of the first network of the second aspect above to implement the functions performed by the first mobility management network element above. The communication device can be the first mobility management network element, or it can be a chip or chip system or system on chip of the first mobility management network element, etc. The communication device can execute the functions performed by the first mobility management network element above through hardware, or it can execute the corresponding software implementation through hardware. The hardware or software includes one or more modules corresponding to the above functions. For example, a transceiver module and a processing module. The transceiver module can independently complete the following transceiver operations, or it can cooperate with the processing module to complete the following transceiver operations; accordingly, the processing module can also independently complete the following processing operations, or it can cooperate with the transceiver module to complete the following processing operations, without limitation.

[0073] Among them, the transceiver module is used to receive a third request from the second mobility management network element of the second network; the third request is used to request to switch the terminal device from the third network to the first network, and the second network is the home network of the terminal device; the processing module is used to obtain the identification information of the second session management network element of the second network; the transceiver module is also used to send a first request to the first session management network element of the first network; wherein the first request is used to request to establish a session for the terminal device, and the first request includes the identification information of the second session management network element.

[0074] In one possible design, the processing module is specifically used to: determine the identification information of the second session management network element based on the third request; wherein the third request includes the identification information of the second session management network element; or, the third request includes network slice information, and determines the identification information of the second session management network element based on the network slice information; or, randomly determine the identification information of the second session management network element based on a preset configuration.

[0075] In one possible design, the third request includes global identification information of the target access network device, and the processing module is further used to determine the first session management network element based on the global identification information of the target access network device before the transceiver module sends the first request to the first session management network element of the first network; or, the third request includes network slice information, and the processing module is further used to determine the first session management network element based on the network slice information before the transceiver module sends the first request to the first session management network element of the first network.

[0076] In one possible design, the third request also includes one or more of the following: identification information of the session established by the third network for the terminal device, and identification information of the third session management network element of the third network.

[0077] In one possible design, the first request also includes one or more of the following: identification information of the session established by the third network for the terminal device, and identification information of the third session management network element of the third network.

[0078] In one possible design, the transceiver module is also used to receive a first response from the first session management network element and send a third response to the second mobility management network element; wherein the first response includes the second tunnel information; the third response is used to indicate that the first network allows the terminal device to switch from the third network to the first network, and the third response includes the identification information of the first mobility management network element and the second tunnel information.

[0079] In one possible design, the second tunnel information is used to establish an uplink data forwarding tunnel between a source access network device of a third network and a third user plane network element of the third network.

[0080] Among them, the technical effects brought about by the above-mentioned eighth aspect or any possible design in the eighth aspect can be referred to the technical effects brought about by the above-mentioned second aspect or any possible design in the second aspect, and will not be repeated here.

[0081] In the ninth aspect, an embodiment of the present application provides a communication device, which can be applied to the second mobility management network element of the second network of the third aspect above to implement the functions performed by the second mobility management network element above. The communication device can be the second mobility management network element, or it can be a chip or chip system or system on chip of the second mobility management network element, etc. The communication device can execute the functions performed by the second mobility management network element through hardware, or it can execute the corresponding software implementation through hardware. The hardware or software includes one or more modules corresponding to the above functions. For example, a transceiver module and a processing module. The transceiver module can independently complete the following transceiver operations, or it can cooperate with the processing module to complete the following transceiver operations; accordingly, the processing module can also independently complete the following processing operations, or it can cooperate with the transceiver module to complete the following processing operations, without limitation.

[0082] Among them, the transceiver module is used to receive a fourth request from the third mobility management network element of the third network; wherein the fourth request is used to request to switch the terminal device from the third network to the first network, and the second network is the home network of the terminal device; the processing module is used to obtain the identification information of the second session management network element of the second network; the transceiver module is also used to send a third request to the first mobility management network element of the first network; wherein the third request is used to request to switch the terminal device from the third network to the first network, and the third request includes the identification information of the second session management network element.

[0083] In one possible design, the processing module is specifically configured to determine identification information of the second session management network element based on a fourth request; wherein the fourth request includes the identification information of the second session management network element. Alternatively, the fourth request includes identification information of a session established by a third network for a terminal device, and the processing module is specifically configured to determine the identification information of the second session management network element based on the session identification information from a pre-stored association between the session identification information and the identification information of the second session management network element. Alternatively, the transceiver module is further configured to send identification information of the session established by the third network for the terminal device to a third session management network element of the third network, and receive identification information of the second session management network element corresponding to the session from the third session management network element. Alternatively, the transceiver module is further configured to send identification information of the session established by the third network for the terminal device to a second unified data management network element of the second network, and receive identification information of the second session management network element corresponding to the session from the second unified data management network element. Alternatively, the processing module is specifically configured to randomly determine the identification information of the second session management network element based on a preset configuration.

[0084] In one possible design, the fourth request also includes first identification information and global identification information of the target access network device; wherein, the first identification information is identification information allocated by the third network to the terminal device of the second network for accessing the third network, and the global identification information of the target access network device includes second identification information, and the second identification information is identification information allocated by the first network to the terminal device of the first network for accessing the first network.

[0085] In one possible design, the transceiver module is specifically used to send a third request to the first mobility management network element when the first identification information and the second identification information indicate that the terminal device switches from the third network to the first network.

[0086] In one possible design, before the transceiver module sends the third request to the first mobility management network element of the first network: the processing module is also used to determine the first mobility management network element based on the second identification information; or, the transceiver module is also used to send a service discovery request to the second topology management network element of the second network, and receive a service discovery response from the second topology management network element, and the processing module determines the first mobility management network element based on the service discovery response; wherein, the service discovery request includes the global identification information of the target access network device, the service discovery request is used to request the discovery of the mobility management network element associated with the target access network device, and the service discovery response includes the identification information of the first mobility management network element.

[0087] In one possible design, the third request includes third identification information, where the third identification information is identification information allocated by the first network to the terminal device of the second network for accessing the first network.

[0088] In one possible design, the fourth request also includes one or more of the following: network slice information, global identification information of the target access network device, and identification information of the third session management network element of the third network.

[0089] In one possible design, the third request also includes one or more of the following: network slice information, global identification information of the target access network device, and identification information of the third session management network element of the third network.

[0090] In one possible design, the transceiver module is also used to receive a third response from the first mobility management network element; wherein the third response is used to indicate that the first network allows the terminal device to switch from the third network to the first network, and the third response includes the identification information of the first mobility management network element and the second tunnel information; the transceiver module is also used to send a fourth response to the third mobility management network element; wherein the fourth response is used to indicate that the first network allows the terminal device to switch from the third network to the first network, and the fourth response includes the identification information of the first mobility management network element and the second tunnel information.

[0091] In one possible design, the second tunnel information is used to establish an uplink data forwarding tunnel between a source access network device of a third network and a third user plane network element of the third network.

[0092] Among them, the technical effects brought about by the above-mentioned ninth aspect or any possible design in the ninth aspect can refer to the technical effects brought about by the above-mentioned third aspect or any possible design in the third aspect, and will not be repeated here.

[0093] In a tenth aspect, an embodiment of the present application provides a communication device, which can be applied to the second session management network element of the second network of the fourth aspect above to implement the functions performed by the second session management network element above. The communication device can be the second session management network element, or it can be a chip, chip system, or system on chip of the second session management network element. The communication device can perform the functions performed by the second session management network element above through hardware, or it can perform corresponding software implementation through hardware. The hardware or software includes one or more modules corresponding to the above functions. For example, a transceiver module and a processing module. The transceiver module can independently complete the following transceiver operations, or it can cooperate with the processing module to complete the following transceiver operations; accordingly, the processing module can also independently complete the following processing operations, or it can cooperate with the transceiver module to complete the following processing operations, without limitation.

[0094] Among them, the transceiver module is used to receive a second request from a first session management network element of a first network; wherein the second request is used to request to obtain context information of a terminal device, and the second network is a home network of the terminal device; the transceiver module is also used to send a fifth request to a third session management network element of a third network; wherein the third session management network element is a network element in the third network that establishes a session for the terminal device, and the fifth request is used to request to obtain context information of the terminal device; the transceiver module is also used to receive a fifth response from the third session management network element; wherein the fifth response includes the context information of the terminal device stored in the third session management network element; the transceiver module is also used to send a second response to the first session management network element; wherein the second response includes the context information of the terminal device stored in the third session management network element.

[0095] In one possible design, the second request includes one or more of the following: identification information of the session established by the third network for the terminal device, and identification information of the third session management network element.

[0096] In one possible design, the processing module is used to obtain the second tunnel information and the third tunnel information; the transceiver module is used to receive the first tunnel information and the fourth tunnel information from the second user plane network element of the second network; wherein the fifth response includes the second tunnel information and the third tunnel information, the first tunnel information is used to establish a data forwarding tunnel between the first user plane network element of the first network and the second user plane network element of the second network, and the third tunnel information and the fourth tunnel information are used to establish a data forwarding tunnel between the second user plane network element and the third user plane network element; the transceiver module is also used to send the first tunnel information and the second tunnel information to the first session management network element, send the third tunnel information to the second user plane network element, and send the fourth tunnel information to the third session management network element of the third network.

[0097] In one possible design, the second tunnel information is used to establish an uplink data forwarding tunnel between a source access network device of a third network and a third user plane network element of the third network.

[0098] Among them, the technical effects brought about by the above-mentioned tenth aspect or any possible design in the tenth aspect can refer to the technical effects brought about by the above-mentioned fourth aspect or any possible design in the fourth aspect, and will not be repeated here.

[0099] In the eleventh aspect, an embodiment of the present application provides a communication device, which can be applied to the third mobility management network element of the third network of the fifth aspect above to implement the functions performed by the third mobility management network element above. The communication device can be a third mobility management network element, or a chip or chip system or system on chip of the third mobility management network element, etc. The communication device can execute the functions performed by the third mobility management network element above through hardware, or can execute the corresponding software implementation through hardware. The hardware or software includes one or more modules corresponding to the above functions. For example, a transceiver module and a processing module. The transceiver module can independently complete the following transceiver operations, or cooperate with the processing module to complete the following transceiver operations; accordingly, the processing module can also independently complete the following processing operations, or cooperate with the transceiver module to complete the following processing operations, without limitation.

[0100] Among them, the transceiver module is used to receive a switching request from the terminal device; wherein the switching request includes the global identification information of the target access network device, and the switching request is used to request switching to the target access network device; the processing module is used to obtain the identification information of the second session management network element of the second network according to the switching request; wherein the second network is the home network of the terminal device; the transceiver module is also used to send a fourth request to the second mobility management network element of the second network; wherein the fourth request is used to request switching the terminal device from the third network to the first network, and the fourth request includes the identification information of the second session management network element.

[0101] In one possible design, the processing module is specifically used to determine the identification information of the second session management network element from the association relationship between the pre-stored session identification information and the identification information of the second session management network element based on the identification information of the session established by the third network for the terminal device; or, the transceiver module is further used to send the identification information of the session established by the third network for the terminal device to the third session management network element of the third network, and receive the identification information of the second session management network element from the third session management network element; or, the transceiver module is further used to send the identification information of the session established by the third network for the terminal device to the unified data management network element, and receive the identification information of the second session management network element from the unified data management network element; wherein the unified data management network element is the third unified data management network element of the third network, or the unified data management network element is the second unified data management network element of the second network.

[0102] In one possible design, the fourth request also includes first identification information and global identification information of the target access network device; wherein, the first identification information is identification information allocated by the third network to the terminal device of the second network for accessing the third network, and the global identification information of the target access network device includes second identification information, and the second identification information is identification information allocated by the first network to the terminal device of the first network for accessing the first network.

[0103] In one possible design, the transceiver module is also used to receive a fourth response from the second mobility management network element; wherein the fourth response is used to indicate that the first network allows the terminal device to switch from the third network to the first network, and the fourth response includes identification information of the first mobility management network element of the first network and second tunnel information, and the second tunnel information is used to establish an uplink data forwarding tunnel between the source access network device of the third network and the third user plane network element of the third network; the transceiver module is also used to send the second tunnel information to the source access network device of the terminal device.

[0104] Among them, the technical effects brought about by the above-mentioned eleventh aspect or any possible design in the eleventh aspect can refer to the technical effects brought about by the above-mentioned fifth aspect or any possible design in the fifth aspect, and will not be repeated here.

[0105] In the twelfth aspect, an embodiment of the present application provides a communication device, which can be applied to the second user plane network element of the second network of the sixth aspect above to implement the functions performed by the second user plane network element above. The communication device can be the second user plane network element, or it can be a chip or chip system or system on chip of the second user plane network element, etc. The communication device can execute the functions performed by the second user plane network element above through hardware, or it can execute the corresponding software implementation through hardware. The hardware or software includes one or more modules corresponding to the above functions. For example, a transceiver module and a processing module. The transceiver module can independently complete the following transceiver operations, or it can cooperate with the processing module to complete the following transceiver operations; accordingly, the processing module can also independently complete the following processing operations, or it can cooperate with the transceiver module to complete the following processing operations, without limitation.

[0106] Among them, the transceiver module is used to receive business data of the terminal device from the third user plane network element of the third network; wherein the second network is the home network of the terminal device; the processing module is used to determine the first user plane network element of the first network based on the business data of the terminal device; the transceiver module is also used to send the business data of the terminal device to the first user plane network element of the first network.

[0107] In one possible design, the transceiver module is also used to send fourth tunnel information to the second session management network element of the second network; wherein the fourth tunnel information is used to establish an uplink data forwarding tunnel between the second user plane network element and the third user plane network element; the transceiver module is also used to receive service data of the terminal device sent by the third user plane network element according to the fourth tunnel information.

[0108] In one possible design, the transceiver module is also used to receive the fifth tunnel information from the second session management network element of the second network; wherein the fifth tunnel information is used to establish an uplink data forwarding tunnel between the first user plane network element and the second user plane network element; the transceiver module is also used to send the service data of the terminal device to the first user plane network element according to the fifth tunnel information.

[0109] Among them, the technical effects brought about by the above-mentioned twelfth aspect or any possible design in the twelfth aspect can refer to the technical effects brought about by the above-mentioned sixth aspect or any possible design in the sixth aspect, and will not be repeated here.

[0110] In aspect 13, an embodiment of the present application provides a communication device, which includes one or more processors; one or more processors are used to run computer programs or instructions. When the one or more processors execute the computer instructions or instructions, the communication device executes the network switching method as described in the first aspect or any possible design of the first aspect, or executes the network switching method as described in the second aspect or any possible design of the second aspect, or executes the network switching method as described in the third aspect or any possible design of the third aspect, or executes the network switching method as described in the fourth aspect or any possible design of the fourth aspect, or executes the network switching method as described in the fifth aspect or any possible design of the fifth aspect, or executes the network switching method as described in the sixth aspect or any possible design of the sixth aspect.

[0111] In one possible design, the communication device further includes one or more memories, the one or more memories being coupled to one or more processors, and the one or more memories being used to store the above-mentioned computer programs or instructions. In one possible implementation, the memory is located outside the communication device. In another possible implementation, the memory is located within the communication device. In an embodiment of the present application, the processor and the memory may also be integrated into one device, that is, the processor and the memory may also be integrated together. In one possible implementation, the communication device further includes a transceiver, and the transceiver is used to receive information and / or send information.

[0112] In one possible design, the communication device further includes one or more communication interfaces, the one or more communication interfaces are coupled to one or more processors, and the one or more communication interfaces are used to communicate with other modules outside the communication device.

[0113] In the fourteenth aspect, an embodiment of the present application provides a communication device, which includes an input and output interface and a logic circuit; the input and output interface is used to input and / or output information; the logic circuit is used to execute the network switching method as described in the first aspect or any possible design of the first aspect, or execute the network switching method as described in the second aspect or any possible design of the second aspect, or execute the method as described in the third aspect or any possible design of the third aspect, or execute the network switching method as described in the fourth aspect or any possible design of the fourth aspect, or execute the network switching method as described in the fifth aspect or any possible design of the fifth aspect, or execute the network switching method as described in the sixth aspect or any possible design of the sixth aspect, and process and / or generate information according to the information.

[0114] In aspect 15, an embodiment of the present application provides a computer-readable storage medium storing computer instructions or programs. When the computer instructions or programs are run on a computer, the network switching method as described in the first aspect or any possible design of the first aspect is executed, or the network switching method as described in the second aspect or any possible design of the second aspect is executed, or the network switching method as described in the third aspect or any possible design of the third aspect is executed, or the network switching method as described in the fourth aspect or any possible design of the fourth aspect is executed, or the network switching method as described in the fifth aspect or any possible design of the fifth aspect is executed, or the network switching method as described in the sixth aspect or any possible design of the sixth aspect is executed.

[0115] In aspect 16, an embodiment of the present application provides a computer program product comprising computer instructions, which, when executed on a computer, enables the network switching method as described in aspect 1 or any possible design of aspect 1 to be executed, or enables the network switching method as described in aspect 2 or any possible design of aspect 2 to be executed, or enables the network switching method as described in aspect 3 or any possible design of aspect 3 to be executed, or enables the network switching method as described in aspect 4 or any possible design of aspect 4 to be executed, or enables the network switching method as described in aspect 5 or any possible design of aspect 5 to be executed, or enables the network switching method as described in aspect 6 or any possible design of aspect 6 to be executed.

[0116] In aspect 17, an embodiment of the present application provides a computer program, which, when running on a computer, enables the network switching method as described in the first aspect or any possible design of the first aspect to be executed, or enables the network switching method as described in the second aspect or any possible design of the second aspect to be executed, or enables the network switching method as described in the third aspect or any possible design of the third aspect to be executed, or enables the network switching method as described in the fourth aspect or any possible design of the fourth aspect to be executed, or enables the network switching method as described in the fifth aspect or any possible design of the fifth aspect to be executed, or enables the network switching method as described in the sixth aspect or any possible design of the sixth aspect to be executed.

[0117] In aspect 18, an embodiment of the present application provides a chip, comprising: a processor, the processor being coupled to a memory, the memory being used to store programs or instructions, and when the program or instructions are executed by the processor, the chip executes the network switching method described in the first aspect or any possible design of the first aspect, or executes the network switching method described in the second aspect or any possible design of the second aspect, or executes the network switching method described in the third aspect or any possible design of the third aspect, or executes the network switching method described in the fourth aspect or any possible design of the fourth aspect, or executes the network switching method described in the fifth aspect or any possible design of the fifth aspect, or executes the network switching method described in the sixth aspect or any possible design of the sixth aspect.

[0118] Among them, the technical effects brought about by any design method from the thirteenth to the eighteenth aspects can refer to the technical effects brought about by the above-mentioned first aspect or any possible design in the first aspect, or refer to the technical effects brought about by the above-mentioned second aspect or any possible design in the second aspect, or refer to the technical effects brought about by the above-mentioned third aspect or any possible design in the third aspect, or refer to the technical effects brought about by the above-mentioned fourth aspect or any possible design in the fourth aspect, or refer to the technical effects brought about by the above-mentioned fifth aspect or any possible design in the fifth aspect, or refer to the technical effects brought about by the above-mentioned sixth aspect or any possible design in the sixth aspect.

[0119] In the nineteenth aspect, an embodiment of the present application provides a communication system, which may include the communication device described in the seventh aspect or any possible design of the seventh aspect, the communication device described in the eighth aspect or any possible design of the eighth aspect, the communication device described in the ninth aspect or any possible design of the ninth aspect, the communication device described in the tenth aspect or any possible design of the tenth aspect, and the communication device described in the eleventh aspect or any possible design of the eleventh aspect, or may also include the communication device described in the twelfth aspect or any possible design of the twelfth aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0120] FIG1 is a schematic diagram of a network sharing research content provided by an embodiment of the present application;

[0121] FIG2 is a schematic diagram of a network sharing provided in an embodiment of the present application;

[0122] FIG3 is a schematic diagram of a network switching based on inter-network roaming provided by an embodiment of the present application;

[0123] FIG4 is a schematic diagram of a communication system provided in an embodiment of the present application;

[0124] FIG5 is a schematic diagram of a 5G communication system provided in an embodiment of the present application;

[0125] FIG6 is a structural diagram of a communication device provided in an embodiment of the present application;

[0126] FIG7 is a flow chart of a network switching method provided in an embodiment of the present application;

[0127] FIG8 is a flowchart of a process for establishing a data forwarding tunnel provided in an embodiment of the present application;

[0128] FIG9 is a schematic diagram of forwarding service data of a terminal device provided in an embodiment of the present application;

[0129] FIG10 is a flow chart of a network switching method provided in an embodiment of the present application;

[0130] FIG11 is a flow chart of a network switching method provided in an embodiment of the present application;

[0131] FIG12 is a flow chart of a network switching method provided in an embodiment of the present application;

[0132] FIG13 is a flow chart of a network switching method provided in an embodiment of the present application;

[0133] FIG14 is a flow chart of a network switching method provided in an embodiment of the present application;

[0134] FIG15 is a schematic diagram of a communication device provided in an embodiment of the present application;

[0135] FIG16 is a structural diagram of a communication device provided in an embodiment of the present application. DETAILED DESCRIPTION

[0136] Before describing the embodiments of the present application, the technical terms involved in the embodiments of the present application are described.

[0137] Network sharing: When deploying access and core networks, the shared access network is allowed to connect to different core networks. This is a way for operators to share access network resources. Network sharing enables operators to maximize network deployment, improve overall network quality, and reduce network deployment costs.

[0138] The Third Generation Partnership Project (3GPP) communications system has supported various types of network sharing since Rel-5, most of which have been inherited by the fifth-generation (5G) mobile communications system (Rel-15 and beyond). 3GPP TS 23.251 allows shared access networks to be connected to different operator core networks, allowing operators to share not only radio network elements but also the radio resources themselves. As 5G deployment expands, more network sharing scenarios may emerge, depending on the strategies of different operators, commercial agreements, and specific regulations / legislation in different countries.

[0139] As network sharing continues to develop, one of the challenges facing operators is maintaining the interconnection between the shared access network and the core networks of participating operators (i.e., the core networks participating in network sharing). This is due to the large number of network interfaces that need to be maintained. This leads to high network deployment and operating costs, especially when a large number of shared access network devices are involved. Therefore, it is necessary to explore alternative network sharing scenarios, such as those without direct connections between the shared access network and the core networks of participating operators, to reduce network deployment and operating costs.

[0140] For example, referring to the network sharing research content shown in Figure 1, the business requirements of this research content mainly include: network sharing is transparent to users, that is, the user's terminal device only displays the name of the contracted operator, and the service provider of the terminal device is its contracted operator; support for mobility management between core networks participating in network sharing; support for business continuity and quality of service (QoS) between core networks participating in network sharing; support for international roaming based on network sharing; security requirements; billing requirements; user / service experience; regulatory requirements; emergency services; public warning system (PWS) support and other requirements.

[0141] Based on this, it is proposed that the shared access network can directly access the core network 1 (ie, direct connection), or access the core network 2 through the core network 1 (ie, indirect connection).

[0142] For example, as shown in FIG2 , operator (OP) 1 deploys a wireless access network, which can be shared with the core networks of other operators (such as OP2, OP3, and OP4) under certain conditions. The shared access network can be directly connected to the core networks participating in network sharing, such as the shared access network can be directly connected to the core network of OP1, and the shared access network can also be directly connected to the core network of OP4. The shared access network can also be indirectly connected to the core networks participating in network sharing, such as the shared access network can be indirectly connected to the core network of OP2 through the core network of OP1, and the shared access network can also be indirectly connected to the core network of OP3 through the core network of OP1.

[0143] Among them, specific conditions may refer to a specific 5G frequency band or a specific area, etc., without restriction.

[0144] The shared access network device may access the core network of OP1 and the core network of OP4 in a multi-operator core network (MOCN) manner.

[0145] Based on the above network sharing, OP1's terminal devices (such as UE1), OP2's terminal devices (such as UE2), OP3's terminal devices (such as UE3), and OP4's terminal devices (such as UE4) can all access OP1's shared access network, and OP2's terminal devices and OP3's terminal devices can be indirectly routed back to their core network through OP1's core network (such as UE2 is indirectly routed back to OP2's core network through OP1's core network, and UE3 is indirectly routed back to OP3's core network through OP1's core network) to achieve network access.

[0146] The operator name displayed on OP1's terminal devices is OP1's name. The operator name displayed on OP2's terminal devices is OP2's name, and OP2's terminal devices are unaware of OP1's core network. The operator name displayed on OP3's terminal devices is OP3's name, and OP3's terminal devices are unaware of OP1's core network. The operator name displayed on OP4's terminal devices is OP4's name.

[0147] Network switching based on roaming on different networks: When the terminal device moves out of the coverage of the home network, the terminal device can access the home network through the visited network based on the shared access network device. When the terminal device moves within the coverage of the home network, the terminal device can switch from the shared access network device to the access network device of the home network and access the home network through the access network device of the home network.

[0148] For example, referring to the visited network and the home network shown in FIG3 , the terminal device may switch from the shared access network device to the access network device of the home network according to the following steps:

[0149] Step 1: The terminal device sends a handover request to the mobility management network element of the visited network. Correspondingly, the mobility management network element of the visited network receives the handover request from the terminal device.

[0150] The switching request may be used to request switching to a target access network device. The switching request may include global identification information of the target access network device. The target access network device may be an access network device of a home network of the terminal device.

[0151] The global identification information of the target access network device may include the public land mobile network (PLMN) to which the target access network device belongs and identification information of the target access network device in the PLMN.

[0152] Optionally, the switching request may further include global identification information of the terminal device.

[0153] The global identification information of the terminal device may include the PLMN to which the terminal device belongs and identification information of the terminal device in the PLMN.

[0154] Exemplarily, the global identification information of the terminal device may be a subscription permanent identifier (SUPI) of the terminal device.

[0155] Step 2: The mobility management network element of the visited network sends a handover request to the mobility management network element of the home network. Correspondingly, the mobility management network element of the home network receives the handover request from the mobility management network element of the visited network.

[0156] Among them, the mobility management network element of the visited network can determine the PLMN to which the terminal device belongs based on the global identification information of the terminal device, and determine the PLMN to which the target access network device belongs based on the global identification information of the target access network device. When the PLMN to which the target access network device belongs is the same as the PLMN to which the terminal device belongs, it can be determined that the terminal device needs to switch to the home network, and then send a switching request to the mobility management network element of the home network.

[0157] Step 3: The mobility management network element of the home network interacts with other network elements on the home network side according to the handover request to establish a session for the terminal device.

[0158] The session management network element of the home network can establish a session for the terminal device by interacting with the mobility management network element and the user plane network element of the home network.

[0159] Step 4: The session management network element of the home network and the session management network element of the visited network establish a session for the terminal device.

[0160] Among them, the session management network element of the home network and the session management network element of the visited network can exchange tunnel information allocated by the user plane network element of the home network and the tunnel information allocated by the user plane network element of the visited network to achieve communication between the user plane network element of the home network and the user plane network element of the visited network.

[0161] Optionally, the session management network element of the home network may also obtain the context information of the terminal device by interacting with the session management network element of the visited network.

[0162] Step 5: The session management network element of the home network sends a session establishment completion response to the mobility management network element of the home network. Correspondingly, the mobility management network element of the home network receives the session establishment completion response from the session management network element of the home network.

[0163] Step 6: The mobility management network element of the home network sends a handover completion response to the mobility management network element of the visited network. Correspondingly, the mobility management network element of the visited network receives the handover completion response from the mobility management network element of the home network.

[0164] Step 7: The mobility management network element of the visited network may notify the terminal device to perform handover through the shared access network device.

[0165] Step 8: The terminal device switches to the target access network device.

[0166] The above-mentioned network switching based on inter-network roaming only supports switching between shared access network devices and access network devices of the home network. When the terminal device needs to switch from accessing the home network through visited network 1 to accessing the home network through visited network 2 during the movement, if there is no connection between visited network 1 and visited network 2, how the terminal device can switch from visited network 1 to visited network 2 while ensuring the business continuity of the terminal device during the switching process has become a technical problem that needs to be solved urgently.

[0167] In order to solve the above technical problems, an embodiment of the present application provides a network switching method, in which a first session management network element of a first network can receive a first request from a first mobility management network element of the first network, where the first request is used to request establishment of a session for a terminal device, and the first request may include identification information of a second session management network element of a second network, where the second network is a home network of the terminal device; a second request is sent to the second session management network element to request acquisition of context information of the terminal device, a second response is received from the second session management network element, and a session is established for the terminal device based on the second response; wherein the second response includes the context information of the terminal device stored in a third session management network element, and the third session management network element is a network element in the third network that establishes a session for the terminal device.

[0168] In an embodiment of the present application, when a terminal device needs to switch from a third network to a first network, the second session management network element of the terminal device's home network (i.e., the second network) can assist the first session management network element in obtaining the context information of the terminal device stored in the third session management network element. Then, the second session management network element can establish a session for the terminal device based on the context information of the terminal device, thereby enabling the terminal device to switch between different visited networks (i.e., enabling the terminal device to switch between the third network and the first network), while ensuring the service continuity of the terminal device during the switching process and improving communication performance.

[0169] The following describes in detail the implementation of the embodiments of the present application in conjunction with the accompanying drawings.

[0170] The network switching method provided in the embodiment of the present application can be used in any communication system, which may be a 3GPP communication system, for example, a long term evolution (LTE) system, or a 5G mobile communication system, a new radio (NR) communication system, a new radio vehicle to everything (NR V2X) system, and can also be applied to a system of LTE and 5G hybrid networking, or a non-terrestrial network (NTN) system, a device-to-device (D2D) communication system, a machine-to-machine (M2M) communication system, an Internet of Things (IoT), and other next-generation communication systems, such as future communication systems such as 6G, and may also be non-3GPP communication systems without limitation.

[0171] The communication system provided in the embodiment of the present application is described below using FIG4 as an example.

[0172] Figure 4 is a schematic diagram of a communication system provided in an embodiment of the present application. As shown in Figure 4, the communication system may include a first network, a second network and a third network, and each network may include an access network device and a core network device.

[0173] Taking the second network as the home network of the terminal device as an example, when the terminal device is within the coverage of the second network, the terminal device can access the core network of the second network through the access network device in the second network. When the terminal device is within the coverage of the first network, the terminal device can access the core network of the second network through the core network of the first network through the shared access network device in the first network. When the terminal device is within the coverage of the third network, the terminal device can access the core network of the second network through the core network of the third network through the shared access network device of the third network. The terminal device can also switch between the access network devices of the first network, the access network devices of the second network, and the access network devices of the third network.

[0174] Among them, the terminal device in Figure 4 can be located within the beam / cell coverage of the access network device, and the access network device can provide communication services for the terminal device.

[0175] The terminal device in Figure 4 can be a device with wireless transceiver capabilities or a chip or chip system that can be installed in the device, which can allow users to access the network and is used to provide voice and / or data connectivity to users. The terminal device can also be called user equipment (UE), subscriber unit (subscriber unit), terminal (terminal), mobile station (MS), or mobile terminal (MT).

[0176] Exemplarily, the terminal device in FIG4 may be a mobile phone, a tablet computer, or a computer with wireless transceiver function. The terminal device may also be a user station, a mobile station, a remote station, a remote terminal device, a mobile terminal device, a user terminal device, a wireless communication device, a user agent, a user device, a cellular phone, a cordless phone, a session initiation protocol (SIP) phone, a wireless local loop (WLL) station, a personal digital assistant (PDA), a handheld device with wireless communication capabilities, a computing device, a processing device connected to a wireless modem, an in-vehicle device, a wearable device, a terminal device in the Internet of Things, a home appliance, a virtual reality (VR) terminal, an augmented reality (AR) terminal, a wireless terminal in industrial control, a wireless terminal in unmanned driving, a wireless terminal in telemedicine, a wireless terminal in a smart grid, a wireless terminal in a smart city, a wireless terminal in a smart home, a vehicle with vehicle-to-vehicle (V2V) communication capabilities, an intelligent connected vehicle, a UAV to UAV (UAV to Unmanned aerial vehicles (UAVs, U2Us) with communication capabilities, terminal devices in future networks, or terminal devices in future evolved public land mobile networks (PLMNs), etc. are not restricted.

[0177] The access network device in Figure 4 can be any device deployed in the access network that can communicate wirelessly with a terminal device. It can also be a chip or chip system that can be installed in the above-mentioned device. It can also be a logical node or logical module or a function implemented in software. It can be used to implement wireless physical control functions, resource scheduling and wireless resource management, wireless access control, and mobility management. Specifically, the network device can be a device that supports wired access or a device that supports wireless access.

[0178] Exemplarily, the access network equipment may be composed of one or more access network (AN) / radio access network (RAN) nodes. AN / RAN nodes may be: a gNB, a transmission reception point (TRP), an evolved NodeB (eNB), a radio network controller (RNC), a NodeB (NB), a base station controller (BSC), a base transceiver station (BTS), a home base station (e.g., a home evolved NodeB, or HNB), a base band unit (BBU), or a wireless fidelity (Wi-Fi) access point (AP).

[0179] In another example, the access network device may also be a device including a centralized unit (CU) node, or a distributed unit (DU) node, or a CU node and a DU node. For example, the access network device can be divided into CU and DU from a logical function perspective, with some protocol layer functions placed in the CU for centralized control, and the remaining part or all of the protocol layer functions distributed in the DU, which is centrally controlled by the CU. Furthermore, the centralized unit CU can also be divided into a control plane (CU-CP) and a user plane (CU-UP). In different systems, CU (including CU-CP or CU-UP) or DU may also have different names. For example, in an open radio access network (O-RAN) system, CU may also be called O-CU (open CU), DU may also be called O-DU, CU-CP may also be called O-CU-CP, and CU-UP may also be called O-CU-UP.

[0180] Among them, the core network equipment of each network in Figure 4 may include one or more of the following: mobility management network element, session management network element, user plane network element, network topology management network element, unified data management network element, and security edge protection agent network element.

[0181] Among them, the mobility management network element in Figure 4 is mainly responsible for access authentication of terminal devices, mobility management, signaling interaction between various functional network elements, and termination of non-access stratum (NAS) layer signaling security. For example, it manages the user's registration status, reachability status, N1 / N2 interface signaling transmission, access authentication and authorization, user connection status, user registration and network entry, tracking area update, cell handover user authentication, key security, etc.

[0182] Among them, the session management network element in Figure 4 mainly provides session management for terminal device sessions (such as session establishment, modification, and release), network protocol (Internet protocol, IP) address allocation and management, and user plane network element selection and control.

[0183] Among them, the user plane network element in Figure 4 is mainly responsible for providing user plane functions such as forwarding user messages, processing connections with data networks (DNs), session anchors, and QoS policy execution.

[0184] The network topology management NE in FIG4 mainly provides the ability to register and discover NEs in the network.

[0185] Among them, the unified data management network element in Figure 4 can provide storage capabilities for contract data, policy data, and capability exposure-related data.

[0186] Among them, the security edge protection agent network element in Figure 4 is mainly responsible for providing filtering and policy of control plane interface signaling during cross-PLMN interaction, as well as hiding the network element topology within the PLMN.

[0187] Optionally, the core network equipment of each network in Figure 4 can also include one or more of the following: network slice selection network element, network open network element, policy control network element, network slice access control network element, authentication service network element, application function network element, specific network slice authentication and authorization network element, etc., without restriction.

[0188] Taking the communication system shown in Figure 4 as a 5G communication system as an example, as shown in Figure 5, the network element or entity corresponding to the above-mentioned access network device may be the RAN in the 5G communication system, the network element or entity corresponding to the mobility management network element may be the access and mobility management function (AMF) in the 5G communication system, the network element or entity corresponding to the session management network element may be the session management function (SMF) in the 5G communication system, the network element or entity corresponding to the user plane network element may be the user plane function (UPF) in the 5G communication system, the network element or entity corresponding to the network topology management network element may be the network repository function (NRF) in the 5G communication system, the network element or entity corresponding to the security edge protection proxy network element may be the security edge protection proxy (SEPP) in the 5G communication system, the network element or entity corresponding to the network slice selection network element may be the network slice selection function (NSSF) in the 5G communication system, and the network element or entity corresponding to the network open network element may be the network open function (NRF) in the 5G communication system. The network element or entity corresponding to the policy control network element may be a policy control function (NEF) in a 5G communication system; the network element or entity corresponding to the network slice access control network element may be a network slice admission control function (NSACF) in a 5G communication system; the network element or entity corresponding to the unified data management network element may be a unified data repository (UDR) or unified data management (UDM) in a 5G communication system; the network element or entity corresponding to the authentication service network element may be an authentication server function (AUSF) in a 5G communication system; and the network element or entity corresponding to the application function network element may be an application function (APP) in a 5G communication system.AF), the network element or entity corresponding to the specific network slice authentication and authorization network element can be a specific network slice authentication and authorization function (NSSAAF) in the 5G communication system.

[0189] As shown in Figure 5, the RAN communicates with the AMF through the N2 interface. The RAN can also communicate with the UPF through the N3 interface. The UPF can communicate with the SMF through the N4 interface. The UPF can also communicate with the application server in the DN through the N6 interface. Core network devices can obtain each other's services by calling each other's service-based interfaces. For example, core network devices can call services provided by the AMF through the Namf interface, call services provided by the SMF through the Nsmf interface, call services provided by the NRF through the Nnrf interface, call services provided by the NSSF through the Nnssf interface, call services provided by the NEF through the Nnef interface, call services provided by the PCF through the Npcf interface, call services provided by the NSACF through the Nnsacf interface, call services provided by the UDM through the Nudm interface, call services provided by the UDR through the Nudr interface, call services provided by the AUSF through the Nausf interface, call services provided by the AF through the Naf interface, and call services provided by the NSSAAF through the Nnssaaf interface.

[0190] It should be noted that the terminal devices, access network devices, and core network devices in the embodiments of the present application can be one or more chips, or a system on chip (SOC), etc. Figure 4 or Figure 5 is only an exemplary figure, and the number of devices included is not limited. The names of the various devices and links in Figure 4 or Figure 5 are not limited. In addition to the names shown in Figure 4 or Figure 5, each device and each link can also be named with other names without limitation.

[0191] In specific implementation, each terminal device, access network device, and core network device shown in Figure 4 or Figure 5 can adopt the composition structure shown in Figure 6, or include the components shown in Figure 6. Figure 6 is a schematic diagram of the composition of a communication device 600 provided in an embodiment of the present application. The communication device 600 can be a terminal device or a chip or system on chip in a terminal device; it can also be an access network device or a chip or system on chip in an access network device; it can also be a core network device or a chip or system on chip in a core network device. As shown in Figure 6, the communication device 600 includes a processor 601, a transceiver 602, and a communication line 603.

[0192] Furthermore, the communication device 600 may further include a memory 604 , wherein the processor 601 , the memory 604 and the transceiver 602 may be connected via a communication line 603 .

[0193] The processor 601 is a central processing unit (CPU), a general-purpose processor, a network processor (NP), a digital signal processor (DSP), a microprocessor, a microcontroller, a programmable logic device (PLD), or any combination thereof. The processor 601 may also be other devices with processing functions, such as circuits, devices, or software modules, without limitation.

[0194] Transceiver 602 is used to communicate with other devices or other communication networks. Such other communication networks may be Ethernet, radio access networks (RAN), wireless local area networks (WLAN), etc. Transceiver 602 may be a module, circuit, transceiver, or any device capable of communication.

[0195] The communication line 603 is used to transmit information between the components included in the communication device 600.

[0196] The memory 604 is used to store instructions, where the instructions may be computer programs.

[0197] The memory 604 may be a read-only memory (ROM) or other type of static storage device that can store static information and / or instructions, or a random access memory (RAM) or other type of dynamic storage device that can store information and / or instructions, or an electrically erasable programmable read-only memory (EEPROM), a compact disc read-only memory (CD-ROM) or other optical disc storage, optical disc storage (including compact disc, laser disc, optical disc, digital versatile disc, Blu-ray disc, etc.), magnetic disk storage media or other magnetic storage devices, etc., without limitation.

[0198] It should be noted that the memory 604 can exist independently of the processor 601 or can be integrated with the processor 601. The memory 604 can be used to store instructions, program code, or some data. The memory 604 can be located within the communication device 600 or outside the communication device 600, without limitation. The processor 601 is configured to execute the instructions stored in the memory 604 to implement the network switching method provided in the following embodiments of the present application.

[0199] In an example, the processor 601 may include one or more CPUs, such as CPU0 and CPU1 in FIG. 6 .

[0200] As an optional implementation, the communication device 600 includes multiple processors. For example, in addition to the processor 601 in FIG. 6 , it may also include a processor 607 .

[0201] As an optional implementation, the communication apparatus 600 further includes an output device 605 and an input device 606. For example, the input device 606 is a keyboard, a mouse, a microphone, a joystick, and the like, and the output device 605 is a display screen, a speaker, and the like.

[0202] It should be noted that the communication device 600 may be a desktop computer, a portable computer, a network server, a mobile phone, a tablet computer, a wireless terminal, an embedded device, a chip system, or a device having a structure similar to that shown in FIG6 . Furthermore, the structure shown in FIG4 does not limit the communication device. In addition to the components shown in FIG6 , the communication device may include more or fewer components than shown, or combine certain components, or arrange the components differently.

[0203] In the embodiment of the present application, the chip system can be composed of chips, or can include chips and other discrete devices.

[0204] In addition, the actions, terms, etc. involved in the various embodiments of this application can refer to each other without limitation. The message names or parameter names in the messages exchanged between the various devices in the embodiments of this application are only examples, and other names can also be used in specific implementations without limitation.

[0205] In conjunction with the communication system shown in Figure 4 or Figure 5, the network switching method provided in the embodiment of the present application is described with reference to Figure 7 below. The terminal device, access network device, core network device (such as mobility management network element, session management network element, user plane network element, etc.) described in the following embodiments can all have the components shown in Figure 6. The processing performed by a single execution subject (terminal device or access network device or core network device) shown in the embodiment of the present application can also be divided into multiple execution subjects, and these execution subjects can be logically and / or physically separated without limitation.

[0206] For example, referring to Figure 7 below, the network switching method provided in an embodiment of the present application is described by taking the case where the home network of the terminal device is the second network and the terminal device switches from the source access network device of the third network to the target access network device of the first network as an example.

[0207] The source access network device may be an access network device shared by the third network and the second network, and the terminal device may access the core network of the second network through the core network of the third network via the source access network device. The target access network device may be an access network device shared by the second network and the first network, and the terminal device may access the core network of the second network through the core network of the first network via the target access network device.

[0208] FIG7 is a flow chart of a network switching method provided in an embodiment of the present application. As shown in FIG7 , the method may include:

[0209] Step 701: The terminal device sends a handover request to a third mobility management network element of a third network. Correspondingly, the third mobility management network element receives the handover request from the terminal device.

[0210] The third mobility management network element may be any one or more of one or more mobility management network elements in the third network corresponding to a session established by the third network for the terminal device. The handover request may include global identification information of the target access network device, and the handover request may be used to request handover to the target access network device.

[0211] The target access network device belongs to the first network, and the global identification information of the target access network device may include the second identification information and the identification information of the target access network device in the first network. The second identification information may be the network identification information of the first network, such as the PLMN ID of the first network. The PLMN may also be the PLMN selected when the terminal device of the first network accesses the first network, i.e., the selected PLMN. It may also be the home PLMN of the terminal device of the first network. The second identification information may also be described as identification information allocated by the first network to the terminal device of the first network for accessing the first network, or as the second identification information being the PLMN of the network (i.e., the first network) to which the target access network device belongs, etc., without limitation.

[0212] Optionally, the switching request may further include first identification information.

[0213] The first identification information may be identification information allocated by the third network to the terminal device of the second network for accessing the third network.

[0214] Exemplarily, the first identification information may be a PLMN allocated by the third network to the terminal device of the second network for accessing the third network. The PLMN may also be referred to as a selected PLMN, or an alternative PLMN, etc., without limitation.

[0215] Optionally, the handover request may further include global identification information of the terminal device. Wherein, the home network of the terminal device is the second network, and the global identification information of the terminal device may include fourth identification information and identification information of the terminal device in the second network. The fourth identification information may be identification information allocated by the second network to the terminal device of the second network for accessing the second network.

[0216] Exemplarily, the fourth identification information may be the PLMN of the second network, or may be described as the PLMN of the home network (ie, the second network) of the terminal device, or may be described as the PLMN to which the terminal device belongs, etc., without limitation.

[0217] Exemplarily, the global identification information of the terminal device may be SUPI.

[0218] Optionally, the switching request may further include identification information of the session of the terminal device.

[0219] Optionally, the terminal device may send a handover request to the third mobility management network element when moving from the coverage area of ​​the source access network device to the coverage area of ​​the target access network device.

[0220] Step 702: The third mobility management network element obtains identification information of the second session management network element of the second network according to the handover request.

[0221] In a first possible design, when the third mobility management network element establishes a session for the terminal device on the third network, it may save an association between identification information of the established session and identification information of the second session management network element. When the third mobility management network element receives a handover request from the terminal device, the third mobility management network element may determine, based on the identification information of the terminal device's session in the handover request, the identification information of the second session management network element corresponding to the identification information of the terminal device's session from a pre-saved association.

[0222] Among them, the second session management network element determined by this possible design can be any one or more of the one or more session management network elements in the second network corresponding to the session established by the second network for the terminal device.

[0223] In a second possible design, a third session management network element of a third network may save an association between identification information of the established session and identification information of the second session management network element when establishing a session for a terminal device on the third network. When the third mobility management network element receives a handover request from the terminal device, the third mobility management network element may determine identification information of the session of the terminal device based on the handover request, and then send the identification information of the session to the third session management network element. Based on the identification information of the session, the third session management network element may determine the identification information of the second session management network element corresponding to the identification information of the session from a pre-saved association, and send the identification information of the second session management network element to the third mobility management network element.

[0224] The third session management network element may be any one or more of one or more session management network elements in the third network that correspond to a session established by the third network for the terminal device (or the third session management network element may be described as a network element in the third network that establishes a session for the terminal device). The second session management network element determined by this possible design may be any one or more of one or more session management network elements in the second network that correspond to a session established by the second network for the terminal device.

[0225] In a third possible design, when the third mobility management network element receives a handover request from a terminal device, the third mobility management network element may determine identification information of a session of the terminal device based on the handover request, and send the identification information of the session to the unified data management network element. The unified data management network element determines, based on the identification information of the session, identification information of a second session management network element corresponding to the identification information of the session from a pre-stored association, and sends the identification information of the second session management network element to the third mobility management network element.

[0226] The unified data management network element may be a unified data management network element of the third network (or referred to as a third unified data management network element), or may be a unified data management network element of the second network (or referred to as a second unified data management network element). The second session management network element determined by this possible design may be any one or more of one or more session management network elements in the second network corresponding to a session established by the second network for the terminal device.

[0227] It should be noted that, upon receiving the handover request sent by the terminal device, the third mobility management network element may execute step 702 above, obtain the identification information of the second session management network element, and then execute step 703 below. The third mobility management network element may also skip step 702 above and directly execute step 703 below upon receiving the handover request sent by the terminal device.

[0228] Step 703: The third mobility management network element sends a fourth request to the second mobility management network element of the second network. Correspondingly, the second mobility management network element receives the fourth request from the third mobility management network element.

[0229] The second mobility management network element may be a mobility management network element in the second network specifically used to forward handover requests between different visited networks, or may be any one or more of one or more mobility management network elements corresponding to a session established by the second network for the terminal device. The fourth request may be used to request handover of the terminal device from the third network to the first network.

[0230] The third mobility management network element may carry the identification information of the target access network device and the global identification information of the terminal device in the handover request in the fourth request.

[0231] Optionally, the fourth request may further include first identification information.

[0232] The first identification information may be identification information allocated by the third network to the terminal device of the second network for accessing the third network.

[0233] Exemplarily, the first identification information may be a PLMN allocated by the third network to the terminal device of the second network for accessing the third network. The PLMN may also be referred to as a selected PLMN, or an alternative PLMN, etc., without limitation.

[0234] Optionally, if the third mobility management network element performs step 702, the fourth request may include the identification information of the second session management network element determined according to step 702. If the third mobility management network element does not perform step 702, the fourth request does not include the identification information of the second session management network element determined according to step 702.

[0235] Optionally, the fourth request may further include identification information of the session established by the third network for the terminal device.

[0236] Optionally, the fourth request may also include network slice information corresponding to the terminal device.

[0237] Optionally, the fourth request may further include identification information of the third session management network element.

[0238] The third mobility management network element may determine the identification information of the third session management network element according to the identification information of the session established by the third network for the terminal device.

[0239] Optionally, the fourth request may further include context information of the terminal device stored in the third mobility management network element.

[0240] Optionally, the fourth request may be an AMF redirect message.

[0241] Step 704: The second mobility management network element obtains identification information of a second session management network element of the second network.

[0242] In a first possible design, when the fourth request includes identification information of the second session management network element, the second mobility management network element may determine the identification information of the second session management network element based on the fourth request.

[0243] Among them, the second session management network element determined by this possible design can be any one or more of the one or more session management network elements in the second network corresponding to the session established by the second network for the terminal device.

[0244] In a second possible design, when the second network establishes a session for the terminal device, the second mobility management network element may save an association between identification information of the established session and identification information of the second session management network element. When the second mobility management network element receives a fourth request from the third mobility management network element, the second mobility management network element may determine, based on the fourth request, the identification information of the session established for the terminal device, and then, based on the identification information, determine, from a pre-saved association, the identification information of the second session management network element corresponding to the identification information of the terminal device's session.

[0245] If the fourth request includes identification information of the session established by the third network for the terminal device, the second mobility management network element may determine the identification information of the second session management network element based on the identification information. Alternatively, the second mobility management network element may determine the identification information of the session of the terminal device based on the global identification information of the terminal device in the fourth request, and then determine the identification information of the second session management network element.

[0246] Among them, the second session management network element determined by this possible design can be any one or more of the one or more session management network elements in the second network corresponding to the session established by the second network for the terminal device.

[0247] In a third possible design, when the third session management network element establishes a session for the terminal device on the third network, it may save the association between the identification information of the established session and the identification information of the second session management network element. When the second mobility management network element receives a fourth request from the third mobility management network element, the second mobility management network element may determine the identification information of the session established for the terminal device based on the fourth request, and then send the identification information of the session to the third session management network element. Based on the identification information of the session, the third session management network element determines the identification information of the second session management network element corresponding to the identification information of the session from the pre-saved association, and sends the identification information of the second session management network element to the second mobility management network element.

[0248] Among them, the second session management network element determined by this possible design can be any one or more of the one or more session management network elements in the second network corresponding to the session established by the second network for the terminal device.

[0249] In a fourth possible design, the second unified data management network element may save the association between the identification information of the established session and the identification information of the second session management network element when establishing a session for the terminal device in the second network. When the second mobility management network element receives a fourth request from the third mobility management network element, the second mobility management network element may determine the identification information of the session established for the terminal device based on the fourth request, and then send the identification information of the session to the second unified data management network element. Based on the identification information of the session, the second unified data management network element determines the identification information of the second session management network element corresponding to the identification information of the session from the pre-saved association relationship, and sends the identification information of the second session management network element to the second mobility management network element.

[0250] Among them, the second session management network element determined by this possible design can be any one or more of the one or more session management network elements in the second network corresponding to the session established by the second network for the terminal device.

[0251] In a fifth possible design, the second mobility management network element may also randomly determine the identification information of the second session management network element according to a preset configuration.

[0252] Specifically, network element information of one or more session management network elements in the second network can be pre-configured on the second mobility management network element. When the second mobility management network element receives the fourth request from the third mobility management network element, the second mobility management network element can randomly select one or more session management network elements from the pre-configured network element information as the second session management network element. That is, the second session management network element determined by this possible design can be any one or more session management network elements in the second network. The second session management network element can be any one or more of the one or more session management network elements in the second network corresponding to the session established by the second network for the terminal device, or the second session management network element can also be one or more session management network elements in the second network that are unrelated to the session established by the second network for the terminal device, without limitation.

[0253] It should be noted that, when the second mobility management network element receives the fourth request sent by the third mobility management network element, it may execute the above step 704 to obtain the identification information of the second session management network element, and then execute the following step 705. The second mobility management network element may also skip the above step 704 and directly execute the following step 705 when receiving the fourth request sent by the third mobility management network element.

[0254] Step 705: The second mobility management network element sends a third request to the first mobility management network element of the first network. Correspondingly, the first mobility management network element receives the third request from the second mobility management network element.

[0255] The third request may be used to request switching the terminal device from the third network to the first network.

[0256] The second mobility management network element may determine the first identification information based on the fourth request, and determine the second identification information based on the global identification information of the target access network device in the fourth request. The first identification information is identification information allocated by the third network to the terminal device of the second network for accessing the third network (for example, a different PLMN allocated by the third network), and the second identification information is identification information allocated by the first network to the terminal device of the first network for accessing the first network (for example, the PLMN of the first network).

[0257] According to the first identification information, the second mobility management network element can determine that the terminal device is a roaming user of a different network.

[0258] Based on the first identification information and the second identification information, the second mobility management network element can determine that the terminal device switches from the third network to the first network. If the second mobility management network element supports the terminal device switching from the third network to the first network, the second mobility management network element can send a third request to the first mobility management network element of the first network.

[0259] If the second mobility management network element supports communication with the third network and supports communication with the first network, it can be considered that the second mobility management network element supports the terminal device to switch from the third network to the first network.

[0260] In a first possible design, the second mobility management network element may determine the first mobility management network element based on the second identification information.

[0261] Specifically, network element information of mobility management network elements of different networks may be pre-configured on the second mobility management network element (e.g., network element information of one or more mobility management network elements of the first network, network element information of one or more mobility management network elements of the third network, etc.). When the second mobility management network element determines that a third request needs to be sent to the first mobility management network element of the first network, the second mobility management network element may determine the first network based on the second identification information, and then randomly select one or more mobility management network elements of the first network as the first mobility management network element from the pre-configured network element information.

[0262] That is, the first mobility management network element determined by this possible design can be any one or more mobility management network elements in the first network. The first mobility management network element can be a mobility management network element in the first network that corresponds to the target access network device, or can be a mobility management network element in the first network that is unrelated to the target access network device, without limitation.

[0263] In a second possible design, the second mobility management network element may determine the first mobility management network element through a service discovery process.

[0264] Among them, the second mobility management network element can send a service discovery request to the topology management network element of the second network (or referred to as the second topology management network element), and the service discovery request can include the global identification information of the target access network device. The service discovery request is used to request the discovery of the mobility management network element associated with the target access network device. The second topology management network element can send the service discovery request to the topology management network element of the first network (or referred to as the first topology management network element), and the first topology management network element determines the mobility management network element corresponding to the target access network device (i.e., the first mobility management network element) based on the service discovery request, and carries the identification information of the first mobility management network element in the service discovery response and sends it to the second mobility management network element through the second topology management network element.

[0265] That is, the first mobility management network element determined by this possible design may be a mobility management network element in the first network corresponding to the target access network device.

[0266] Based on the above description, when the second mobility management network element sends the third request to the first mobility management network element, the information in the fourth request may be carried in the third request.

[0267] The third request may include the global identification information of the target access network device and the global identification information of the terminal device.

[0268] Optionally, if the second mobility management network element performs step 704, the third request may include the identification information of the second session management network element determined according to step 704. If the second mobility management network element does not perform step 704, the third request does not include the identification information of the second session management network element determined according to step 704.

[0269] Optionally, the third request may further include identification information of the session established by the third network for the terminal device.

[0270] Optionally, the third request may also include network slice information corresponding to the terminal device.

[0271] Optionally, the third request may further include identification information of a third session management network element.

[0272] Optionally, the third request may further include context information of the terminal device stored in the third mobility management network element.

[0273] Optionally, the third request may further include third identification information, where the third identification information is identification information allocated by the first network to the terminal device of the second network for accessing the first network.

[0274] Exemplarily, the third identification information may be a PLMN allocated by the first network to the terminal device of the second network for accessing the first network. The PLMN may also be referred to as a selected PLMN, or an alternative PLMN, etc., without limitation.

[0275] Specifically, when determining to send the third request to the first mobility management network element, the second mobility management network element may determine the third identification information, and send the third request to the first mobility management network element using the third identification information.

[0276] Step 706: The first mobility management network element obtains identification information of the second session management network element of the second network.

[0277] In a first possible design, when the third request includes identification information of the second session management network element, the first mobility management network element may determine the identification information of the second session management network element based on the third request.

[0278] Among them, the second session management network element determined by this possible design can be any one or more of the one or more session management network elements in the second network corresponding to the session established by the second network for the terminal device, or it can also be one or more session management network elements in the second network that are unrelated to the session established by the second network for the terminal device, without restriction.

[0279] In a second possible design, when the third request includes network slice information corresponding to the terminal device, the first mobility management network element can determine the identification information of the second session management network element based on the network slice information.

[0280] The first mobility management network element may determine the identification information of the second session management network element through a service discovery process.

[0281] Exemplarily, the first mobility management network element may send a service discovery request to the first topology management network element, where the service discovery request may include network slice information, and the service discovery request is used to request the discovery of a session management network element associated with the network slice information. The first topology management network element may send the service discovery request to the second topology management network element, which determines the session management network element (i.e., the second session management network element) corresponding to the network slice information based on the service discovery request, and carries the identification information of the second session management network element in the service discovery response and sends it to the first mobility management network element through the first topology management network element.

[0282] Among them, the second session management network element determined by this possible design can be any one or more of the one or more session management network elements in the second network corresponding to the session established by the second network for the terminal device, or it can also be one or more session management network elements in the second network that are unrelated to the session established by the second network for the terminal device, without restriction.

[0283] In a third possible design, the first mobility management network element may also randomly determine the identification information of the second session management network element according to a preset configuration.

[0284] Specifically, network element information of one or more session management network elements in the second network can be pre-configured on the first mobility management network element. When the first mobility management network element receives the third request from the second mobility management network element, the first mobility management network element can randomly select one or more session management network elements from the pre-configured network element information as the second session management network element. That is, the second session management network element determined by this possible design can be any one or more session management network elements in the second network. The second session management network element can be any one or more of the one or more session management network elements in the second network corresponding to the session established by the second network for the terminal device, or the second session management network element can also be one or more session management network elements in the second network that are unrelated to the session established by the second network for the terminal device, without limitation.

[0285] Step 707: The first mobility management network element sends a first request to the first session management network element of the first network. Correspondingly, the first session management network element receives the first request from the first mobility management network element of the first network.

[0286] The first request may be used to request establishment of a session for the terminal device, and the first request may include identification information of the second session management network element.

[0287] In the first possible design, when the third request includes the global identification information of the target access network device, the first mobility management network element can determine the session management network element corresponding to the target access network device in the first network as the first session management network element based on the global identification information of the target access network device.

[0288] In the second possible design, when the third request includes network slice information, the first mobility management network element can determine the session management network element corresponding to the network slice information in the first network as the first session management network element based on the network slice information.

[0289] Based on the above description, when the first mobility management network element sends the first request to the first session management network element, the information in the third request may also be carried in the first request.

[0290] The first request may include the global identification information of the target access network device and the global identification information of the terminal device.

[0291] Optionally, the first request may further include identification information of the session established by the third network for the terminal device.

[0292] Optionally, the first request may further include identification information of a third session management network element.

[0293] Optionally, the first request may further include context information of the terminal device stored in the third mobility management network element.

[0294] Step 708: The first session management network element sends a second request to the second session management network element. Correspondingly, the second session management network element receives the second request from the first session management network element.

[0295] The second request may be used to request to obtain context information of the terminal device.

[0296] The first session management network element may determine the second session management network element according to the first request, and then send the second request to the second session management network element.

[0297] Optionally, when the first session management network element sends the second request to the second session management network element, the information in the first request may be carried in the second request.

[0298] Optionally, the second request may further include identification information of the session established by the third network for the terminal device.

[0299] Optionally, the second request may further include identification information of a third session management network element.

[0300] Step 709: The second session management network element sends a fifth request to the third session management network element of the third network. Correspondingly, the third session management network element receives the fifth request from the second session management network element.

[0301] The fifth request may be used to request to obtain context information of the terminal device.

[0302] The second session management network element may determine the third session management network element based on the identification information of the session established by the third network for the terminal device included in the second request, and then send the fifth request to the third session management network element. Alternatively, the second session management network element may determine the third session management network element based on the identification information of the third session management network element included in the second request, and then send the fifth request to the third session management network element.

[0303] Optionally, the fifth request may include identification information of the session established by the third network for the terminal device.

[0304] Step 710: The third session management network element sends a fifth response to the second session management network element. Correspondingly, the second session management network element receives the fifth response from the third session management network element.

[0305] The fifth response may include context information of the terminal device stored in the third session management network element.

[0306] The third session management network element may determine the context information of the terminal device according to the fifth request, and then carry the context information in the fifth response and send it to the second session management network element.

[0307] Step 711: The second session management network element sends a second response to the first session management network element. Correspondingly, the first session management network element receives the second response from the second session management network element.

[0308] The second response may include context information of the terminal device stored in the third session management network element.

[0309] Step 712: The first session management network element establishes a session for the terminal device according to the second response.

[0310] Among them, the first network, the second network and the third network can refer to the method shown in Figure 8 below to establish a data forwarding tunnel corresponding to the session for the terminal device, refer to the method shown in Figure 9 below to forward the service data of the terminal device through the established data forwarding tunnel, and refer to the method shown in Figure 10 below to inform the terminal device to allow it to switch from the third network to the first network, so that the terminal device can switch from the source access network device to the target access network device to realize network switching.

[0311] Based on the method shown in FIG. 7 , the home network (i.e., the second network) of a terminal device can assist the terminal device in performing handover between different visited networks participating in network sharing (e.g., switching from a third network to the first network). Specifically, when a terminal device performs handover between different visited networks participating in network sharing, the mobility management element of the home network can transfer the terminal device's context information between the mobility management elements of the different visited networks (i.e., the second mobility management element assists the first mobility management element in obtaining the terminal device's context information stored in the third mobility management element). Furthermore, the session management element of the home network can transfer the terminal device's context information between the session management elements of the different visited networks (i.e., the second session management element assists the first session management element in obtaining the terminal device's context information stored in the third session management element). This assists the session management elements of the different visited networks in establishing data forwarding tunnels, enabling handover of the terminal device between different visited networks (i.e., enabling handover of the terminal device between the third network and the first network), while ensuring service continuity for the terminal device during the handover process and improving communication performance.

[0312] Compared to the inter-network roaming-based network handover shown in FIG3 , the inter-network roaming-based network handover shown in FIG3 only supports handover between a visited network and a home network that participate in network sharing. In this embodiment of the present application, when a terminal device performs handover between different visited networks that participate in network sharing, because the different visited networks cannot communicate directly, for example, handover signaling between the mobility management network element of the first network and the mobility management network element of the third network cannot be directly transmitted, the session management network element of the first network cannot directly obtain the terminal device context information stored in the session management network element of the third network. Instead, the mobility management network element and session management network element of the home network perform indirect information forwarding and data acquisition and forwarding. Therefore, during handover, the mobility management network element of the third network needs to inform the mobility management network element of the first network of the identification information of the session management network element of the home network, which can assist the session management network element of the first network in obtaining the terminal device context information. This enables handover of the terminal device between different visited networks, while ensuring service continuity for the terminal device during the handover process and improving communication performance.

[0313] FIG8 is a flowchart of a process for establishing a data forwarding tunnel provided in an embodiment of the present application. As shown in FIG8 , the method may include:

[0314] Step 801: The third session management network element sends second tunnel information and third tunnel information to the second session management network element. Correspondingly, the second session management network element receives the second tunnel information and third tunnel information from the third session management network element.

[0315] Among them, the second tunnel information can be used to establish an uplink data forwarding tunnel between the source access network device of the third network and the third user plane network element of the third network, and the third tunnel information can be used to establish a downlink data forwarding tunnel between the second user plane network element and the third user plane network element of the second network.

[0316] The third user plane network element may be one or more of one or more user plane network elements in the third network corresponding to a session established by the third network for the terminal device. The second user plane network element may be one or more of one or more user plane network elements in the second network corresponding to a session established by the second network for the terminal device.

[0317] Optionally, the third session management network element may carry the second tunnel information and the third tunnel information in a fifth response and send the response to the second session management network element.

[0318] Optionally, the third session management network element may send a session establishment request to the third user plane network element. The third user plane network element may allocate the second tunnel information and the third tunnel information based on the session establishment request and send the information to the third session management network element. Upon receiving the second tunnel information and the third tunnel information, the third session management network element may include the information in a fifth response and send it to the second session management network element.

[0319] Step 802: The second session management network element sends third tunnel information to the second user plane network element. Correspondingly, the second user plane network element receives the third tunnel information from the second session management network element.

[0320] Step 803: The second session management network element sends second tunnel information to the first session management network element. Correspondingly, the first session management network element receives the second tunnel information from the second session management network element.

[0321] Optionally, the second session management network element may carry the second tunnel information in a second response and send it to the first session management network element.

[0322] Step 804: The second session management network element sends fourth tunnel information to the third session management network element. Correspondingly, the third session management network element receives the fourth tunnel information from the second session management network element.

[0323] The fourth tunnel information may be used by the second user plane network element and the third user plane network element to establish an uplink data forwarding tunnel.

[0324] Optionally, the second session management network element may send a session establishment request to the second user plane network element. The second user plane network element may allocate the first tunnel information and the fourth tunnel information based on the session establishment request and send them to the second session management network element. Upon receiving the first tunnel information and the fourth tunnel information, the second session management network element may execute step 804 to send the fourth tunnel information to the third session management network element, and may also execute step 806 to send the first tunnel information to the first session management network element.

[0325] The first tunnel information may be used to establish a data forwarding tunnel between a first user plane network element and a second user plane network element of the first network.

[0326] The first user plane network element may be one or more user plane network elements in the first network corresponding to the session established by the first network for the terminal device.

[0327] Step 805: The third session management network element sends fourth tunnel information to the third user plane network element. Correspondingly, the third user plane network element receives the fourth tunnel information from the third session management network element.

[0328] Step 806: The second session management network element sends the first tunnel information to the first session management network element. Correspondingly, the first session management network element receives the first tunnel information from the second session management network element.

[0329] The second session management network element may carry the first tunnel information in a second response and send it to the first session management network element.

[0330] Step 807: The first session management network element sends first tunnel information to the first user plane network element.

[0331] Step 808: The first session management network element sends the fifth tunnel information to the second session management network element. Correspondingly, the second session management network element receives the fifth tunnel information from the first session management network element.

[0332] The fifth tunnel information may be used by the first user plane network element and the second user plane network element to establish an uplink data forwarding tunnel.

[0333] Optionally, the first session management network element may send a session establishment request to the first user plane network element. The first user plane network element may allocate fifth tunnel information based on the session establishment request and send it to the first session management network element. Upon receiving the fifth tunnel information, the first session management network element may send it to the second session management network element.

[0334] Step 809: The second session management network element sends the fifth tunnel information to the second user plane network element. Correspondingly, the second user plane network element receives the fifth tunnel information from the second session management network element.

[0335] Step 810: The first session management network element sends second tunnel information to the first mobility management network element. Correspondingly, the first mobility management network element receives the second tunnel information from the first session management network element.

[0336] Optionally, the first session management network element may carry the second tunnel information in the first response and send it to the first mobility management network element.

[0337] Step 811: The first mobility management network element sends second tunnel information to the second mobility management network element. Correspondingly, the second mobility management network element receives the second tunnel information from the first mobility management network element.

[0338] Optionally, the first mobility management network element may carry the second tunnel information in a third response and send the response to the second mobility management network element.

[0339] The third response may be used to indicate that the first network allows the terminal device to switch from the third network to the first network.

[0340] Step 812: The second mobility management network element sends the second tunnel information to the third mobility management network element. Correspondingly, the third mobility management network element receives the second tunnel information from the second mobility management network element.

[0341] The second mobility management network element may carry the second tunnel information in a fourth response and send the response to the third mobility management network element.

[0342] The fourth response may be used to indicate that the first network allows the terminal device to switch from the third network to the first network.

[0343] Step 813: The third mobility management network element sends the second tunnel information to the source access network device. Correspondingly, the source access network device receives the second tunnel information from the third mobility management network element.

[0344] Based on the method shown in Figure 8 above, a data forwarding tunnel can be established between the source access network device, the third user plane network element, the second user plane network element, and the first user plane network element, so that the source access network device can subsequently send the service data of the terminal device to the first user plane network element through the third user plane network element and the second user plane network element, thereby ensuring the service continuity of the terminal device during the switching process.

[0345] FIG9 is a schematic diagram of forwarding service data of a terminal device provided in an embodiment of the present application. As shown in FIG9 , the method may include:

[0346] Step 901: The source access network device sends service data of the terminal device to the third user plane network element. Correspondingly, the third user plane network element receives the service data of the terminal device from the source access network device.

[0347] Among them, the source access network device can send the service data of the terminal device to the third user plane network element according to the second tunnel information.

[0348] Step 902: The third user plane network element sends service data of the terminal device to the second user plane network element. Correspondingly, the second user plane network element receives the service data of the terminal device from the third user plane network element.

[0349] Among them, the third user plane network element can determine the second user plane network element according to the service data of the terminal device, and then send the service data of the terminal device to the second user plane network element.

[0350] Among them, the third user plane network element can send the service data of the terminal device to the second user plane network element according to the fourth tunnel information.

[0351] Step 903: The second user plane network element sends the service data of the terminal device to the first user plane network element. Correspondingly, the first user plane network element receives the service data of the terminal device from the second user plane network element.

[0352] The second user plane network element may determine the first user plane network element based on the service data of the terminal device, and then send the service data of the terminal device to the first user plane network element.

[0353] Among them, the second user plane network element can send the service data of the terminal device to the first user plane network element based on the fifth tunnel information.

[0354] Based on the method shown in Figure 9 above, the source access network equipment and the user-side network elements of each network can forward the service data of the terminal device based on the tunnel information allocated in Figure 8 above, ensure the service continuity of the terminal device during the switching process, and improve communication performance.

[0355] Based on the method shown in FIG. 7 above, the first network, the second network, and the third network may also refer to the method shown in FIG. 10 below to inform the terminal device to allow it to switch from the third network to the first network.

[0356] FIG10 is a flow chart of a network switching method provided in an embodiment of the present application. As shown in FIG10 , the method may include:

[0357] Step 713: The first session management network element sends a first response to the first mobility management network element. Correspondingly, the first mobility management network element receives the first response from the first session management network element.

[0358] The first response may be a session establishment response.

[0359] Step 714: The first mobility management network element sends a third response to the second mobility management network element. Correspondingly, the second mobility management network element receives the third response from the first mobility management network element.

[0360] The third response may be used to indicate that the first network allows the terminal device to switch from the third network to the first network.

[0361] Optionally, the third response may include identification information of the first mobility management network element.

[0362] Step 715: The second mobility management network element sends a fourth response to the third mobility management network element. Correspondingly, the third mobility management network element receives the fourth response from the second mobility management network element.

[0363] The fourth response may be used to indicate that the first network allows the terminal device to switch from the third network to the first network.

[0364] Optionally, the fourth response may include identification information of the first mobility management network element.

[0365] Step 716: The third mobility management network element notifies the terminal device to perform switching. Accordingly, the terminal device switches from the source access network device to the target access network device.

[0366] Based on the method shown in FIG10 above, the terminal device can switch from the source access network device to the target access network device when the first network, the second network, and the third network complete the session establishment, thereby realizing the switching of the terminal device between the third network and the first network.

[0367] Based on the methods shown in Figures 7 to 10 above, referring to Figure 11 below, taking the third mobility management network element as vAMF1, the third session management network element as vSMF1, the second mobility management network element as hAMF, the second session management network element as hSMF, the first mobility management network element as vAMF2, and the first session management network element as vSMF2 as an example, the network switching process of the above-mentioned terminal device switching from the source access network device to the target access network device is illustrated.

[0368] FIG11 is a flow chart of a network switching method provided in an embodiment of the present application. As shown in FIG11 , the method may include:

[0369] Step 0: vAMF1 determines the identification information (hSMF ID) of the hSMF.

[0370] In a first possible design, vAMF 1 can save the hSMF ID during the process of establishing a session for the terminal device in the third network.

[0371] In the second possible design, vAMF1 does not save the hSMF ID when establishing a session for the terminal device in the third network. vAMF1 can send a request to vSMF1 (the request carries the session ID to be switched, that is, the identification information of the session of the terminal device). vSMF1 obtains the corresponding hSMF ID based on the session ID and returns it to vAMF1.

[0372] In a third possible design, vAMF1 requests the hSMF ID corresponding to the session of the terminal device from vUDM (ie, the third unified data management network element) / hUDM (ie, the second unified data management network element).

[0373] Step 1: vAMF1 sends an AMF redirect message to hAMF.

[0374] The AMF redirection message may include the hSMF ID, the selected PLMN ID allocated by the first network to the terminal device, the SUPI of the terminal device, and the global identification information (target ID) of the target RAN.

[0375] Optionally, the AMF redirection message may also include UE context information (UE context information) to be switched in vAMF1.

[0376] Step 2. hAMF determines, based on the selected PLMN ID, SUPI, and PLMN ID information in the target ID in the AMF redirection message received from vAMF1, that the terminal device is a roaming user on a different network, and that the terminal device is performing a direct handover of a shared RAN between different operators (i.e., switching from a shared RAN in a visited network to a shared RAN in another visited network). If, based on the configuration of hAMF, it is determined that the handover operation of the terminal device is supported, a session establishment request may be sent to vAMF2 to forward the information received from vAMF1 to vAMF2.

[0377] In the first possible design, hAMF is pre-configured with the interface vAMF ID corresponding to the PLMN of different operators. hAMF can determine vAMF2 by querying the configuration based on the PLMN ID in the target ID.

[0378] In the second possible design, hAMF obtains the vAMF2 ID corresponding to the target ID through the service discovery process of hNRF (ie, the second network topology management network element) and vNRF (ie, the first network topology management network element) based on the target ID.

[0379] Step 3: vAMF2 selects vSMF2 based on the message received from hAMF and sends a PDU session establishment request to vSMF2.

[0380] The session establishment request may include hSMF ID and UE context information.

[0381] Step 4: vSMF2 sends a request to the hSMF ID based on the hSMF ID obtained from the session establishment request. The request carries the session ID (such as PDU session ID) to request to obtain the SM context of the terminal device.

[0382] Step 5: hSMF requests the SM context of the terminal device from vSMF1 according to the received session ID.

[0383] Step 6: vSMF1 returns the SM context of the terminal device to hSMF.

[0384] Step 7: hSMF returns the SM context of the terminal device in vSMF1 to vSMF2.

[0385] Step 8: vSMF2 interacts with hSMF to establish a session for the terminal device.

[0386] Among them, vSMF2 can select vUPF2, send the tunnel information of vUPF2 to hSMF, and obtain the tunnel information of hUPF through hSMF.

[0387] Step 9: vSMF2 returns a session establishment response message to vAMF2.

[0388] Step 10: vAMF2 sends a session establishment response message to hAMF to notify hAMF that the session establishment on the VPLMN2 side is complete.

[0389] The session establishment response message may carry an N2 Notify URI, such as a vAMF2 ID.

[0390] Step 11: hAMF sends a session establishment response message to vAMF1.

[0391] The session establishment response message may carry an N2 Notify URI, such as a vAMF2 ID.

[0392] Step 12: vAMF1 notifies the terminal device to complete the switching.

[0393] Different from the above-mentioned determination of hSMF ID by vAMF1 in FIG11 , referring to FIG12 below, hSMF ID may also be determined by hAMF, that is, steps 0 to 2 in FIG11 above may be replaced by steps 1 and 2 in FIG12 below.

[0394] FIG12 is a flow chart of a network switching method provided in an embodiment of the present application. As shown in FIG12 , the method may include:

[0395] Step 1. vAMF sends an AMF redirect message to hAMF.

[0396] Among them, the AMF redirection message may include the selected PLMN ID allocated by the first network to the terminal device, the SUPI of the terminal device, and the target ID.

[0397] Optionally, the AMF redirection message may also include UE context information to be switched in vAMF1.

[0398] Step 2. hAMF determines that the terminal device belongs to a roaming user on a different network based on the selected PLMN ID, SUPI, and PLMN ID information in the target ID in the AMF redirection message received from vAMF1, and that the terminal device is performing a direct handover of a shared RAN between different operators (i.e., switching from a shared RAN in a visited network to a shared RAN in another visited network). If, based on the configuration of hAMF, it is determined that the handover operation of the terminal device is supported, a suitable vAMF2 can be selected, and the hSMF ID currently being used by the terminal device can be determined, and an AMF redirection message is sent to vAMF2.

[0399] The AMF redirect message may include hSMF ID and N2 Notify URI (such as vAMF2 ID), and the hSMF ID is used to obtain the SM context of the terminal device in vSMF1.

[0400] In the first possible design, when hAMF saves the context information of the terminal device and establishes a session for the terminal device, hAMF will save the corresponding hSMF ID information.

[0401] In the second possible implementation, when hAMF does not save the context information of the terminal device, hAMF can request the hSMF ID information corresponding to the session ID (such as PDU Session ID) from vSMF1, or hAMF can request the hSMF ID information corresponding to the session ID from hUDM (i.e., the second unified data management network element).

[0402] Unlike the above-mentioned FIG12 where hAMF determines the hSMF ID based on the session ID, referring to the following FIG13 , hAMF may also randomly determine the hSMF ID, that is, steps 1 to 7 in the above-mentioned FIG12 may be replaced by steps 1 to 7 in the following FIG13 .

[0403] FIG13 is a flow chart of a network switching method provided in an embodiment of the present application. As shown in FIG13 , the method may include:

[0404] Step 1. vAMF sends an AMF redirect message to hAMF.

[0405] Among them, the AMF redirection message may include the selected PLMN ID allocated by the first network to the terminal device, the SUPI of the terminal device, the target ID, and the vSMF1 ID.

[0406] Optionally, the AMF redirection message may also include UE context information to be switched in vAMF1.

[0407] Step 2. hAMF determines that the terminal device belongs to a roaming user on a different network based on the selected PLMN ID, SUPI, and PLMN ID information in the target ID in the AMF redirection message received from vAMF1, and that the terminal device is performing a direct handover of a shared RAN between different operators (i.e., switching from a shared RAN in a visited network to a shared RAN in another visited network). If, according to the configuration of hAMF, it is determined that the handover operation of the terminal device is supported, a suitable vAMF2 can be selected, and the hSMF ID can be randomly determined, and an AMF redirection message is sent to vAMF2.

[0408] The hAMF may randomly determine the hSMF ID according to the default configuration. The hSMF ID may be an hSMF ID unrelated to the session in VPLMN1 or an hSMF ID corresponding to the session in VPLMN1, without limitation. That is, the type of the hSMF ID may be default.

[0409] Among them, the AMF redirection message may include hSMF ID, vSMF1 ID, N2 Notify URI (such as vAMF2 ID), and the hSMF ID is used by vSMF2 to obtain the SM context of the terminal device in vSMF1.

[0410] Optionally, the AMF redirection message may also include UE context information.

[0411] Step 3: vAMF2 selects vSMF2 based on the message received from hAMF and sends a PDU session establishment request to vSMF2.

[0412] The session establishment request may include hSMF ID and vSMF1 ID.

[0413] Step 4: vSMF2 determines the hSMF ID and its type obtained from the session establishment request, and sends a request to the hSMF ID. The request carries the vSMF1 ID to request the SM context of the terminal device.

[0414] Step 5: hSMF requests the SM context of the terminal device from vSMF1 according to the received vSMF1 ID.

[0415] Step 6: vSMF1 returns the SM context of the terminal device to hSMF.

[0416] Step 7: hSMF returns the SM context of the terminal device in vSMF1 to vSMF2.

[0417] Unlike the above-mentioned Figures 11 to 13 in which the hSMF ID is determined by vAMF1 or hAMF, referring to the following Figure 14 , the hSMF ID can also be determined by vAMF2, that is, steps 0 to 7 in the above-mentioned Figure 11 can be replaced by steps 1 to 7 in the following Figure 14 .

[0418] FIG14 is a flow chart of a network switching method provided in an embodiment of the present application. As shown in FIG14 , the method may include:

[0419] Step 1. vAMF sends an AMF redirect message to hAMF.

[0420] Among them, the AMF redirection message may include the selected PLMN ID allocated by the first network to the terminal device, the SUPI of the terminal device, the target ID, and the vSMF1 ID.

[0421] Optionally, the AMF redirection message may also include UE context information to be switched in vAMF1.

[0422] Step 2. hAMF determines that the terminal device is a roaming user on a different network based on the selected PLMN ID, SUPI, and PLMN ID information in the target ID in the AMF redirection message received from vAMF1, and that the terminal device is performing a direct handover of a shared RAN between different operators (i.e., switching from a shared RAN in a visited network to a shared RAN in another visited network). If, based on the configuration of hAMF, it is determined that the handover operation of the terminal device is supported, a suitable vAMF2 may be selected, and an AMF redirection message may be sent to vAMF2.

[0423] The AMF redirect message may include vSMF1 ID and N2 Notify URI (such as vAMF2 ID).

[0424] Optionally, the AMF redirection message may also include UE context information.

[0425] Step 3. vAMF2 selects the hSMF ID based on the network slice information (such as the slice information of home S-NSSAI) according to the message received from hAMF.

[0426] Among them, vAMF2 can select the hSMF ID corresponding to the slice information of home S-NSSAI through the service discovery process of vNRF and hNRF according to the slice information of home S-NSSAI, or the hSMF ID corresponding to the home PLMN of the terminal device is pre-configured on vAMF2, and vAMF2 can also randomly determine the hSMF ID according to the default configuration of vAMF2.

[0427] Step 4: vAMF2 selects vSMF2 based on the message received from hAMF and sends a PDU session establishment request to vSMF2.

[0428] The session establishment request may include hSMF ID and vSMF1 ID.

[0429] Step 5: vSMF2 sends a request to the hSMF ID based on the hSMF ID obtained from the session establishment request. The request carries the vSMF1 ID to request to obtain the SM context of the terminal device.

[0430] Step 6: hSMF requests the SM context of the terminal device from vSMF1 according to the received vSMF1 ID.

[0431] Step 7: vSMF1 returns the SM context of the terminal device to hSMF, and hSMF returns the SM context of the terminal device in vSMF1 to vSMF2.

[0432] It should be noted that the various embodiments of this application can be implemented independently or in combination, without limitation. Unless otherwise specified or there is a logical conflict, the terms and / or descriptions of the different embodiments provided in this application are consistent and can be referenced by each other. The technical features in different embodiments can be combined to form new embodiments based on their inherent logical relationships.

[0433] It is understood that in the embodiments of the present application, the execution subject may perform some or all of the steps in the embodiments of the present application. These steps or operations are merely examples, and the embodiments of the present application may also perform other operations or variations of various operations. In addition, the various steps may be performed in a different order than those presented in the embodiments of the present application, and it is possible that not all operations in the embodiments of the present application need to be performed.

[0434] The above mainly introduces the solution provided by the embodiment of the present application from the perspective of interaction between devices. It is understandable that, in order to realize the above functions, each device includes a hardware structure and / or software module corresponding to the execution of each function. Those skilled in the art should easily realize that, in combination with the algorithm steps of each example described in the embodiments disclosed herein, the present application can be implemented in the form of hardware or a combination of hardware and computer software. Whether a function is executed in the form of hardware or computer software driving hardware depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of this application.

[0435] The embodiments of the present application can divide the functional modules of each device according to the above method examples. For example, each functional module can be divided according to each function, or two or more functions can be integrated into one processing module. The above integrated modules can be implemented in the form of hardware or in the form of software functional modules. It should be noted that the division of modules in the embodiments of the present application is schematic and is only a logical function division. In actual implementation, there may be other division methods.

[0436] In the case of dividing each functional module according to each function, Figure 15 shows a communication device 150, which can execute the actions performed by the terminal device or access network device or core network device in the methods shown in Figures 7 to 14 above. All relevant contents of each step involved in the above method embodiment can be referred to the functional description of the corresponding functional module. The technical effects that can be obtained can be referred to the above method embodiment and will not be repeated here.

[0437] The communication device 150 may include a transceiver module 1501 and a processing module 1502. Exemplarily, the communication device 150 may be a communication device, or a chip used in a communication device, or other combined device or component having the aforementioned communication device functionality. When the communication device 150 is a communication device, the transceiver module 1501 may be a transceiver, which may include an antenna and radio frequency circuits, etc.; the processing module 1502 may be a processor (or processing circuit), such as a baseband processor, which may include one or more CPUs. When the communication device 150 is a component having the aforementioned communication device functionality, the transceiver module 1501 may be a radio frequency unit; the processing module 1502 may be a processor (or processing circuit), such as a baseband processor. When the communication device 150 is a system-on-chip (SoC), the transceiver module 1501 may be the input / output interface of the SoC (e.g., a baseband chip); the processing module 1502 may be the SoC's processor (or processing circuit), which may include one or more central processing units. It should be understood that the transceiver module 1501 in the embodiment of the present application can be implemented by a transceiver or a transceiver-related circuit component; the processing module 1502 can be implemented by a processor or a processor-related circuit component (or, referred to as a processing circuit).

[0438] Among them, the transceiver module 1501 can be used to perform all transceiver operations performed by the communication device in the embodiments shown in Figures 7 to 14, and / or to support other processes of the technology described in this document; the processing module 1502 can be used to perform all operations other than transceiver operations performed by the communication device in the embodiments shown in Figures 7 to 14, and / or to support other processes of the technology described in this document.

[0439] Exemplarily, when the communication device 150 is used to execute the action performed by the first session management network element, the transceiver module 1501 is used to receive a first request from the first mobility management network element of the first network, where the first request is used to request to establish a session for the terminal device, and the first request includes identification information of the second session management network element of the second network, where the second network is the home network of the terminal device; the transceiver module 1501 is also used to send a second request to the second session management network element and receive a second response from the second session management network element, and the processing module 1502 is used to establish a session for the terminal device based on the second response; wherein the second request is used to request to obtain context information of the terminal device, and the second response includes context information of the terminal device stored in a third session management network element, and the third session management network element is a network element in the third network that establishes a session for the terminal device.

[0440] In another example, when the communication device 150 is used to execute the action performed by the first mobility management network element, the transceiver module 1501 is used to receive a third request from the second mobility management network element of the second network; the third request is used to request to switch the terminal device from the third network to the first network, and the second network is the home network of the terminal device; the processing module 1502 is used to obtain the identification information of the second session management network element of the second network; the transceiver module 1501 is also used to send a first request to the first session management network element of the first network; wherein the first request is used to request to establish a session for the terminal device, and the first request includes the identification information of the second session management network element.

[0441] In another example, when the communication device 150 is used to execute the action performed by the second mobility management network element, the transceiver module 1501 is used to receive a fourth request from the third mobility management network element of the third network; wherein the fourth request is used to request to switch the terminal device from the third network to the first network, and the second network is the home network of the terminal device; the processing module 1502 is used to obtain the identification information of the second session management network element of the second network; the transceiver module 1501 is also used to send a third request to the first mobility management network element of the first network; wherein the third request is used to request to switch the terminal device from the third network to the first network, and the third request includes the identification information of the second session management network element.

[0442] In another example, when the communication device 150 is used to execute the action performed by the second session management network element, the transceiver module 1501 is used to receive a second request from the first session management network element of the first network; wherein the second request is used to request to obtain the context information of the terminal device, and the second network is the home network of the terminal device; the transceiver module 1501 is also used to send a fifth request to the third session management network element of the third network; wherein the third session management network element is the network element in the third network that establishes a session for the terminal device, and the fifth request is used to request to obtain the context information of the terminal device; the transceiver module 1501 is also used to receive a fifth response from the third session management network element; wherein the fifth response includes the context information of the terminal device stored in the third session management network element; the transceiver module 1501 is also used to send a second response to the first session management network element; wherein the second response includes the context information of the terminal device stored in the third session management network element.

[0443] In another example, when the communication device 150 is used to execute the action performed by the third mobility management network element, the transceiver module 1501 is used to receive a switching request from the terminal device; wherein the switching request includes the global identification information of the target access network device, and the switching request is used to request switching to the target access network device; the processing module 1502 is used to obtain the identification information of the second session management network element of the second network according to the switching request; wherein the second network is the home network of the terminal device; the transceiver module 1501 is also used to send a fourth request to the second mobility management network element of the second network; wherein the fourth request is used to request switching the terminal device from the third network to the first network, and the fourth request includes the identification information of the second session management network element.

[0444] In another example, when the communication device 150 is used to execute the action performed by the second user plane network element, the transceiver module 1501 is used to receive service data of the terminal device from the third user plane network element of the third network; wherein the second network is the home network of the terminal device; the transceiver module 1501 is also used to send the service data of the terminal device to the first user plane network element of the first network.

[0445] As another possible implementation, the transceiver module 1501 in FIG15 can be replaced by a transceiver, which can integrate the functions of the transceiver module 1501; the processing module 1502 can be replaced by a processor, which can integrate the functions of the processing module 1502. Furthermore, the communication device 150 shown in FIG15 can also include a memory.

[0446] Alternatively, when the processing module 1502 is replaced by a processor and the transceiver module 1501 is replaced by a transceiver, the communication device 150 involved in the embodiment of the present application may also be the communication device 160 shown in Figure 16, wherein the processor may be the logic circuit 1601 and the transceiver may be the interface circuit 1602. Furthermore, the communication device 160 shown in Figure 16 may also include a memory 1603.

[0447] The embodiments of the present application also provide a computer program product, which, when executed by a computer, can implement the functions of any of the above method embodiments.

[0448] The embodiments of the present application also provide a computer program, which, when executed by a computer, can implement the functions of any of the above method embodiments.

[0449] The embodiment of the present application also provides a computer-readable storage medium. All or part of the processes in the above-mentioned method embodiments can be completed by a computer program to instruct the relevant hardware, and the program can be stored in the above-mentioned computer-readable storage medium. When the program is executed, it can include the processes of the above-mentioned method embodiments. The computer-readable storage medium can be an internal storage unit of the terminal (including the data sending end and / or the data receiving end) of any of the above-mentioned embodiments, such as the hard disk or memory of the terminal. The above-mentioned computer-readable storage medium can also be an external storage device of the above-mentioned terminal, such as a plug-in hard disk equipped on the above-mentioned terminal, a smart memory card (smart media card, SMC), a secure digital (secure digital, SD) card, a flash card (flash card), etc. Further, the above-mentioned computer-readable storage medium can also include both the internal storage unit of the above-mentioned terminal and an external storage device. The above-mentioned computer-readable storage medium is used to store the above-mentioned computer program and other programs and data required by the above-mentioned terminal. The above-mentioned computer-readable storage medium can also be used to temporarily store data that has been output or is to be output.

[0450] It should be noted that the terms "first" and "second" in the specification, claims and drawings of this application are used to distinguish different objects, rather than to describe a specific order. "First" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of this embodiment, unless otherwise specified, "multiple" means two or more.

[0451] Furthermore, the terms "include," "comprise," and "have," and any variations thereof, are intended to cover non-exclusive inclusions. For example, a process, method, system, product, or apparatus comprising a series of steps or elements is not limited to the listed steps or elements, but may optionally include steps or elements not listed, or may optionally include other steps or elements inherent to the process, method, product, or apparatus.

[0452] It should be understood that in this application, "at least one (item)" refers to one or more. "Multiple" refers to two or more. "At least two (items)" refers to two or three and more than three. "And / or" is used to describe the association relationship of associated objects, indicating that three relationships can exist. For example, "A and / or B" can mean: only A exists, only B exists, and A and B exist at the same time, where A and B can be singular or plural. The character " / " generally indicates that the previous and next associated objects are in an "or" relationship. "At least one of the following items" or similar expressions refers to any combination of these items, including any combination of single items or plural items. For example, at least one of a, b or c can mean: a, b, c, "a and b", "a and c", "b and c", or "a and b and c", where a, b, c can be single or multiple. “When” and “if” both mean that corresponding measures will be taken under certain objective circumstances. They do not limit the time, nor do they require any judgment action when they are implemented, nor do they mean that there are other limitations.

[0453] In the embodiments of this application, words such as "exemplary" or "for example" are used to indicate examples, illustrations, or descriptions. Any embodiment or design described as "exemplary" or "for example" in the embodiments of this application should not be construed as being preferred or advantageous over other embodiments or designs. Rather, the use of words such as "exemplary" or "for example" is intended to present the relevant concepts in a concrete manner to facilitate understanding.

[0454] In this application, "sending information to ... (a terminal device)" can be understood as the destination of the information being the terminal device. This can include sending information directly or indirectly to the terminal device. "Receiving information from ... (a terminal device)" can be understood as the source of the information being the terminal device. This can include receiving information directly or indirectly from the terminal device. The information may undergo necessary processing between the source and destination, such as formatting changes, but the destination can still understand the valid information from the source.

[0455] Through the description of the above implementation methods, technical personnel in the relevant field can clearly understand that for the convenience and simplicity of description, only the division of the above-mentioned functional modules is used as an example. In actual applications, the above-mentioned functions can be assigned to different functional modules as needed, that is, the internal structure of the device can be divided into different functional modules to complete all or part of the functions described above.

[0456] In the several embodiments provided in this application, it should be understood that the disclosed devices and methods can be implemented in other ways. For example, the device embodiments described above are merely schematic. For example, the division of the modules or units is merely a logical function division. In actual implementation, there may be other division methods, such as multiple units or components can be combined or integrated into another device, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of devices or units, which can be electrical, mechanical or other forms.

[0457] The units described as separate components may or may not be physically separate, and the components shown as units may be one physical unit or multiple physical units, that is, they may be located in one place or distributed in multiple places. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0458] In addition, the functional units in the various embodiments of the present application may be integrated into a single processing unit, or each unit may exist physically separately, or two or more units may be integrated into a single unit. The aforementioned integrated units may be implemented in the form of hardware or software functional units.

[0459] If the integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a readable storage medium. Based on this understanding, the technical solution of the embodiment of the present application or all or part of the technical solution can be embodied in the form of a software product, which is stored in a storage medium and includes several instructions for enabling a device (which can be a single-chip microcomputer, chip, etc.) or a processor to execute all or part of the steps of the method described in each embodiment of the present application. The aforementioned storage medium includes various media that can store program codes, such as a USB flash drive, a mobile hard disk, a ROM, a RAM, a magnetic disk, or an optical disk.

Claims

1. A network switching method, characterized in that: The method is applied to a first session management network element of a first network, and the method includes: Receiving a first request from a first mobility management network element of the first network; wherein the first request is used to request to establish a session for a terminal device, and the first request includes identification information of a second session management network element of a second network, and the second network is a home network of the terminal device; Sending a second request to the second session management network element; wherein the second request is used to request to obtain context information of the terminal device; receiving a second response from the second session management network element; wherein the second response includes context information of the terminal device stored in a third session management network element, and the third session management network element is a network element in a third network that establishes a session for the terminal device; A session is established for the terminal device according to the second response.

2. The method according to claim 1, characterized in that The first request also includes one or more of the following: identification information of the session established by the third network for the terminal device, and identification information of the third session management network element.

3. The method according to claim 2, characterized in that The second request includes one or more of the following: identification information of the session established by the third network for the terminal device, and identification information of the third session management network element.

4. The method according to any one of claims 1 to 3, characterized in that: The establishing a session for the terminal device according to the second response includes: Obtaining first tunnel information and second tunnel information; wherein the second response includes the first tunnel information and the second tunnel information, and the first tunnel information is used to establish a data forwarding tunnel between a first user plane network element of the first network and a second user plane network element of the second network; Sending the first tunnel information to the first user plane network element; Send a first response to the first mobility management network element; wherein the first response includes the second tunnel information.

5. The method according to claim 4, characterized in that The second tunnel information is used for establishing an uplink data forwarding tunnel between the source access network device of the third network and the third user plane network element of the third network.

6. A network switching method, characterized in that: The method is applied to a first mobility management network element of a first network, and the method includes: Receiving a third request from a second mobility management network element of a second network; wherein the third request is used to request switching of a terminal device from a third network to a first network, and the second network is a home network of the terminal device; Acquire identification information of a second session management network element of the second network; Send a first request to a first session management network element of the first network; wherein the first request is used to request to establish a session for the terminal device, and the first request includes identification information of the second session management network element.

7. The method according to claim 6, characterized in that The acquiring identification information of the second session management network element of the second network includes: determining the identification information of the second session management network element according to the third request; wherein the third request includes the identification information of the second session management network element; or The third request includes network slice information, and the identification information of the second session management network element is determined according to the network slice information; or; According to a preset configuration, the identification information of the second session management network element is randomly determined.

8. The method according to claim 6 or 7, characterized in that: The third request includes global identification information of the target access network device, and before sending the first request to the first session management network element of the first network, the method further includes: determining the first session management network element according to the global identification information of the target access network device; or The third request includes network slice information; before sending the first request to the first session management network element of the first network, the method also includes: determining the first session management network element based on the network slice information.

9. The method according to any one of claims 6 to 8, characterized in that: The third request also includes one or more of the following: identification information of the session established by the third network for the terminal device, Identification information of a third session management network element of the third network.

10. The method according to claim 9, characterized in that The first request also includes one or more of the following: identification information of the session established by the third network for the terminal device, and identification information of a third session management network element of the third network.

11. The method according to any one of claims 6 to 10, characterized in that: The method further comprises: receiving a first response from the first session management network element; wherein the first response includes second tunnel information; Send a third response to the second mobility management network element; wherein the third response is used to indicate that the first network allows the terminal device to switch from the third network to the first network, and the third response includes identification information of the first mobility management network element and the second tunnel information.

12. The method according to claim 11, characterized in that The second tunnel information is used for establishing an uplink data forwarding tunnel between the source access network device of the third network and the third user plane network element of the third network.

13. A network switching method, characterized in that: The method is applied to a second mobility management network element of a second network, where the second network is a home network of the terminal device, and the method includes: Receiving a fourth request from a third mobility management network element of a third network; wherein the fourth request is used to request switching of a terminal device from the third network to the first network; Acquire identification information of a second session management network element of the second network; Send a third request to the first mobility management network element of the first network; wherein the third request is used to request to switch the terminal device from the third network to the first network, and the third request includes identification information of the second session management network element.

14. The method according to claim 13, characterized in that The acquiring identification information of the second session management network element of the second network includes: determining the identification information of the second session management network element according to the fourth request; wherein the fourth request includes the identification information of the second session management network element; or The fourth request includes identification information of a session established by the third network for the terminal device, and according to the identification information of the session, the identification information of the second session management network element is determined from an association relationship between the pre-stored identification information of the session and the identification information of the second session management network element; or Sending identification information of a session established by the third network for the terminal device to a third session management network element of the third network, and receiving identification information of the second session management network element corresponding to the session from the third session management network element; or Sending identification information of the session established by the third network for the terminal device to the second unified data management network element of the second network, and receiving identification information of the second session management network element corresponding to the session from the second unified data management network element; or According to a preset configuration, the identification information of the second session management network element is randomly determined.

15. The method according to claim 13 or 14, characterized in that The fourth request also includes first identification information and global identification information of the target access network device; wherein the first identification information is identification information allocated by the third network to the terminal device of the second network for accessing the third network, and the global identification information of the target access network device includes second identification information, and the second identification information is identification information allocated by the first network to the terminal device of the first network for accessing the first network.

16. The method according to claim 15, characterized in that The sending a third request to the first mobility management network element of the first network includes: When the first identification information and the second identification information indicate that the terminal device switches from the third network to the first network, the third request is sent to the first mobility management network element.

17. The method according to claim 15 or 16, characterized in that Before sending the third request to the first mobility management network element of the first network, the method further includes: determining the first mobility management network element according to the second identification information; or Send a service discovery request to the second topology management network element of the second network, receive a service discovery response from the second topology management network element, and determine the first mobility management network element based on the service discovery response; wherein the service discovery request includes the global identification information of the target access network device, the service discovery request is used to request the discovery of the mobility management network element associated with the target access network device, and the service discovery response includes the identification information of the first mobility management network element.

18. The method according to any one of claims 13 to 17, characterized in that: The third request includes third identification information, where the third identification information is identification information allocated by the first network to the terminal device of the second network for accessing the first network.

19. The method according to any one of claims 13 to 18, characterized in that: The fourth request also includes one or more of the following: network slice information, global identification information of the target access network device, and identification information of the third session management network element of the third network.

20. The method according to claim 19, characterized in that The third request also includes one or more of the following: the network slice information, the global identification information of the target access network device, and the identification information of the third session management network element of the third network.

21. The method according to any one of claims 13 to 20, characterized in that: The method further comprises: receiving a third response from the first mobility management network element; wherein the third response is used to indicate that the first network allows the terminal device to switch from the third network to the first network, and the third response includes identification information of the first mobility management network element and second tunnel information; Send a fourth response to the third mobility management network element; wherein the fourth response is used to indicate that the first network allows the terminal device to switch from the third network to the first network, and the fourth response includes identification information of the first mobility management network element and the second tunnel information.

22. The method according to claim 21, characterized in that The second tunnel information is used for establishing an uplink data forwarding tunnel between the source access network device of the third network and the third user plane network element of the third network.

23. A network switching method, characterized in that: The method is applied to a second session management network element of a second network, and the method includes: Receiving a second request from a first session management network element of a first network; wherein the second request is used to request to obtain context information of a terminal device, and the second network is a home network of the terminal device; Sending a fifth request to a third session management network element of the third network; wherein the third session management network element is a network element in the third network that establishes a session for the terminal device, and the fifth request is used to request to obtain context information of the terminal device; receiving a fifth response from the third session management network element; wherein the fifth response includes context information of the terminal device stored in the third session management network element; Sending a second response to the first session management network element; wherein the second response includes the context information of the terminal device stored in the third session management network element.

24. The method according to claim 23, characterized in that The second request includes one or more of the following: identification information of the session established by the third network for the terminal device, and identification information of the third session management network element.

25. The method according to claim 23 or 24, characterized in that The method further comprises: Acquire the second tunnel information and the third tunnel information; wherein the fifth response includes the second tunnel information and the third tunnel information; Receive first tunnel information and fourth tunnel information from a second user plane network element of the second network; wherein the first tunnel information is used for the first user plane network element of the first network to establish a data forwarding tunnel with the second user plane network element of the second network, and the third tunnel information and the fourth tunnel information are used for the second user plane network element to establish a data forwarding tunnel with the third user plane network element; Sending the first tunnel information and the second tunnel information to the first session management network element; Sending the third tunnel information to the second user plane network element; The fourth tunnel information is sent to a third session management network element of the third network.

26. The method according to claim 25, characterized in that The second tunnel information is used for establishing an uplink data forwarding tunnel between the source access network device of the third network and the third user plane network element of the third network.

27. A network switching method, characterized in that: The method is applied to a third mobility management network element of a third network, and the method includes: Receiving a handover request from a terminal device; wherein the handover request includes global identification information of a target access network device, and the handover request is used to request handover to the target access network device; According to the switching request, obtaining identification information of a second session management network element of a second network; wherein the second network is a home network of the terminal device; Send a fourth request to the second mobility management network element of the second network; wherein the fourth request is used to request to switch the terminal device from the third network to the first network, and the fourth request includes identification information of the second session management network element.

28. The method according to claim 27, characterized in that The acquiring identification information of the second session management network element of the second network includes: Determine, according to the identification information of the session established by the third network for the terminal device, the identification information of the second session management network element from an association relationship between the pre-stored identification information of the session and the identification information of the second session management network element; or Sending identification information of the session established by the third network for the terminal device to a third session management network element of the third network, and receiving identification information of the second session management network element from the third session management network element; or Send identification information of the session established by the third network for the terminal device to a unified data management network element, and receive identification information of the second session management network element from the unified data management network element; wherein the unified data management network element is the third unified data management network element of the third network, or the unified data management network element is the second unified data management network element of the second network.

29. The method according to claim 27 or 28, characterized in that The fourth request also includes first identification information and global identification information of the target access network device; wherein the first identification information is identification information allocated by the third network to the terminal device of the second network for accessing the third network, and the global identification information of the target access network device includes second identification information, and the second identification information is identification information allocated by the first network to the terminal device of the first network for accessing the first network.

30. The method according to any one of claims 27 to 29, characterized in that: The method further comprises: receiving a fourth response from the second mobility management network element; wherein the fourth response is used to indicate that the first network allows the terminal device to switch from the third network to the first network, and the fourth response includes identification information and second tunnel information of the first mobility management network element of the first network, and the second tunnel information is used for the source access network device of the third network to establish an uplink data forwarding tunnel with the third user plane network element of the third network; Send the second tunnel information to the source access network device of the terminal device.

31. A network switching method, characterized in that: The method is applied to a second user plane network element of a second network, and the method includes: Receiving service data of a terminal device from a third user plane network element of a third network; wherein the second network is a home network of the terminal device; Determine a first user plane network element of a first network according to the service data of the terminal device; Send the service data of the terminal device to the first user plane network element of the first network.

32. The method according to claim 31, characterized in that The receiving service data of a terminal device from a third user plane network element of a third network includes: Sending fourth tunnel information to the second session management network element of the second network; wherein the fourth tunnel information is used for the second user plane network element and the third user plane network element to establish an uplink data forwarding tunnel; Receive the service data of the terminal device sent by the third user plane network element according to the fourth tunnel information.

33. The method according to claim 31 or 32, characterized in that The sending the service data of the terminal device to the first user plane network element of the first network includes: receiving fifth tunnel information from a second session management network element of the second network; wherein the fifth tunnel information is used for the first user plane network element and the second user plane network element to establish an uplink data forwarding tunnel; According to the fifth tunnel information, the service data of the terminal device is sent to the first user plane network element.

34. A communication device, characterized in that: The communication device includes a processor; the processor is used to run a computer program or instructions so that the communication device executes the network switching method as described in any one of claims 1 to 5, or executes the network switching method as described in any one of claims 6 to 12, or executes the network switching method as described in any one of claims 13 to 22, or executes the network switching method as described in any one of claims 23 to 26, or executes the network switching method as described in any one of claims 27 to 30, or executes the network switching method as described in any one of claims 31 to 33.

35. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores computer instructions or programs, which, when executed on a computer, cause the network switching method described in any one of claims 1 to 5 to be executed, or the network switching method described in any one of claims 6 to 12 to be executed, or the network switching method described in any one of claims 13 to 22 to be executed, or the network switching method described in any one of claims 23 to 26 to be executed, or the network switching method described in any one of claims 27 to 30 to be executed, or the network switching method described in any one of claims 31 to 33 to be executed.

36. A computer program product, characterized in that The computer program product includes computer instructions; when part or all of the computer instructions are executed on a computer, the network switching method described in any one of claims 1 to 5 is executed, or the network switching method described in any one of claims 6 to 12 is executed, or the network switching method described in any one of claims 13 to 22 is executed, or the network switching method described in any one of claims 23 to 26 is executed, or the network switching method described in any one of claims 27 to 30 is executed, or the network switching method described in any one of claims 31 to 33 is executed.

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