Communication method and apparatus

Abstract

A communication method and apparatus, which are applied to the technical field of communications. The method can be applied to a first network element, wherein the first network element is used for managing connection states of a terminal device in a plurality of networks, the plurality of networks comprise a first network and a second network, and the first network element is located in the first network. The method comprises: a first network element receiving a service request of a terminal device, and establishing a connection with the terminal device; and after receiving information of the terminal device and information of a second network, the first network element sending a first message to the terminal device, wherein the first message is used for instructing the terminal device to establish a connection with the second network. By means of the method, the first network element in the first network can notify the terminal device to establish a connection with the second network, so that communication between the terminal device and the second network can be implemented, thereby facilitating an improvement in the communication performance of a distributed network architecture.

Description

A communication method and apparatus

[0001] Cross-reference to related applications

[0002] This application claims priority to Chinese Patent Application No. 202411824940.2, filed on December 10, 2024, entitled "A Communication Method and Apparatus", the entire contents of which are incorporated herein by reference. Technical Field

[0003] This application relates to the field of communication technology, and in particular to a communication method and apparatus. Background Technology

[0004] With the development of communication technology, network architecture has gradually evolved from centralized network architecture to distributed network architecture. In a distributed network architecture, terminal devices can communicate with at least one sub-network through the access and mobility management function (AMF).

[0005] Further research is needed to improve the communication performance of distributed network architectures. Summary of the Invention

[0006] This application provides a communication method and apparatus for notifying a terminal device to establish a connection with a second network through a first network element in a first network, thereby enabling communication between the terminal device and the second network and improving the communication performance of the distributed network architecture.

[0007] In a first aspect, embodiments of this application provide a communication method, the execution subject of which may include a first network element. The first network element can be used to manage the connection status of a terminal device in multiple networks, including a first network and a second network, with the first network element located in the first network. Exemplarily, the first network element is a core network element (e.g., an AMF). For example, the first network element may be a network element in a central network that implements access and mobility management functions, and may be referred to as the central access and mobility management function (C-AMF).

[0008] Optionally, the first network element can be replaced by a module within the first network element. For example, the module within the first network element can be a communication module, a circuit or chip responsible for communication functions (such as a modem chip, also known as a baseband chip, or a system-on-chip (SoC) chip or system-in-package (SIP) chip containing a modem core), a chip system, or a processor; or it can be a logical node, logical module, or software capable of implementing all or part of the functions of the first network element.

[0009] The following explanation uses the example of the first network element as the subject of execution of this method.

[0010] The method includes: a first network element receiving a service request from a terminal device and establishing a connection with the terminal device; the first network element receiving information from the terminal device and information from a second network; and the first network element sending a first message to the terminal device, the first message being used to instruct the terminal device to establish a connection with the second network.

[0011] This method enables the first network element in the first network to notify the terminal device to establish a connection with the second network, thereby enabling communication between the terminal device and the second network and improving the communication performance of the distributed network architecture.

[0012] Furthermore, in this method, when the second network needs to establish a connection with the terminal device, the first network element can send a first message to the terminal device through the connection between the first network element and the terminal device, thereby notifying the terminal device to establish a connection with the second network. In this way, the first network element does not need to broadcast messages to notify the terminal device to establish a connection with the second network within its corresponding tracking area list, thus reducing signaling overhead.

[0013] In one possible design, the multiple networks also include a third network. The method further includes: a first network element acquiring the connection status of a terminal device in a second network and / or a third network; the first network element receiving a second message, the second message including information about the terminal device and information about the second network; if the first network and the terminal device have been updated to a disconnected state, and the second network and the terminal device are also in a disconnected state, the first network element, based on the second message, determines a third network that is in a connected state with the terminal device, wherein a second network element exists in the third network, and the second network element is used to manage the mobility of the terminal device in the third network; the first network element sending a third message to the second network element, the third message being used to request the second network element to notify the terminal device to establish a connection with the second network.

[0014] In this way, when the second network needs to establish a connection with the terminal device, the first network element can notify the terminal device to establish a connection with the second network through the second network element that is already connected to the terminal device. This eliminates the need for the first network element to broadcast messages to notify the terminal device to establish a connection with the second network within its corresponding tracking area list, thereby reducing signaling overhead.

[0015] Furthermore, in this approach, the first network element can be used to manage the connection status of terminal devices in multiple networks. For example, the first network element can be a network element in the central network that implements access and mobility management functions. The second network element is used to manage the mobility of terminal devices in a third network. For example, the second network element can be a network element in a sub-network that implements access and mobility management functions, thereby splitting access and mobility management functions to achieve distributed mobility management. In this way, signaling between the terminal device and network functions in the third network can be forwarded through the second network element, without having to go through the first network element. If the first network element fails, the terminal device can interact with network functions in the first network through the second network element, thereby ensuring service continuity and avoiding or reducing the impact of the first network element on services.

[0016] Furthermore, in this approach, the second network element in the third network manages the mobility of terminal devices within the third network. This allows signaling between the terminal device and network functions in the third network to be forwarded via the second network element, bypassing the first network element. Since the second network element is located within the third network, the transmission latency of signaling forwarded via the second network element is generally lower than that forwarded via the first network element, thus reducing signaling transmission latency. Additionally, the ability to forward signaling between the terminal device and network functions in the third network via the second network element enables signaling transmission within the third network, thereby improving service security and meeting the requirement for closed-loop service operation within the sub-network.

[0017] Furthermore, in this method, the first network element can know the connection status of the terminal device in the second network and / or the third network. For example, the first network element can know the connection status of the terminal device in the sub-network, thereby enabling effective management of the terminal device based on the connection status, which is beneficial to improving communication performance.

[0018] In one possible design, the first network element can obtain the connection status of the terminal device in the second network through the following steps: a third network element or a first access network element sends a fourth message; correspondingly, the first network element receives the fourth message from the third network element or the first access network element, wherein the third network element is a network element in the second network used to manage the mobility of the terminal device in the second network; the first access network element is the serving first access network element of the terminal device; the fourth message is used to indicate that the terminal device is in a disconnected state in the second network. The fourth message is sent by the third network element or the first access network element under the following circumstances: the second network and the terminal device are updated to a disconnected state.

[0019] Through this design, the first network element can accurately determine whether the second network and the terminal device have been updated to a disconnected state.

[0020] In one possible design, the first network element can obtain the connection status of the terminal device in the third network through the following steps: the first network element receives a fifth message, which indicates that the terminal device is in a connected state in the third network.

[0021] In some examples, when a terminal device accesses a third network through a first access network element, the first access network element may send a fifth message; correspondingly, the first network element may receive a fifth message from the first access network element, wherein the fifth message is sent by the first access network element when the terminal device accesses the third network through the first access network element.

[0022] In other examples, the second network element sends a fifth message to the first network element in at least one of the following situations: the terminal device accesses the third network, or, if the multiple networks include a fourth network, the terminal device switches from the fourth network to the third network; accordingly, the first network element receives a fifth message from the second network element, the fifth message being sent by the second network element in at least one of the following situations: the terminal device accesses the third network; or, if the multiple networks include a fourth network, the terminal device switches from the fourth network to the third network.

[0023] In some other examples, multiple networks also include a fourth network. When a terminal device switches from the fourth network to the third network, the fourth network element sends a fifth message to the first network element. Correspondingly, the first network element receives the fifth message from the fourth network element. The fifth message is sent by the fourth network element when multiple networks include a fourth network and the terminal device switches from the fourth network to the third network. Here, the fourth network element is a network element within the fourth network used to manage the mobility of the terminal device within the fourth network.

[0024] This design allows the first network element to accurately determine whether a terminal device is in a connected state within the third network. Furthermore, it provides multiple flexible methods for determining the connected state of a terminal device within the third network.

[0025] In one possible design, upon receiving a second message from a fifth network element (which manages user data and / or status), the second message further indicates which network among multiple networks has a connected state with the terminal device. With this design, the first network element can accurately determine the third network connected to the terminal device based on the network among multiple networks with a connected state. This allows the second network element in the third network to instruct the terminal device to establish a connection with the second network. Furthermore, in this approach, the second message can indicate which network among multiple networks has a connected state with the terminal device, eliminating the need for the first network element to perform additional procedures to determine the network with a connected state, thus saving time in selecting the third network.

[0026] In one possible design, the method further includes: when a handover occurs in the terminal device, the first access network element sends a first handover request according to reporting rules; correspondingly, the first network element receives the first handover request from the first access network element. The first handover request includes information related to the handover of the terminal device; the first handover request is sent by the first access network element according to reporting rules when the terminal device handover occurs, and the reporting rules are one of the following: when the access cell of the terminal device handover occurs, handover-related information is reported to the first network element, including the cell identifier of the target cell; when the access network element of the terminal device handover occurs, handover-related information is reported to the first network element, including the identifier of the target access network element; when the access network element of the terminal device handover occurs and the tracking area where the terminal device is located changes, handover-related information is reported to the first network element, including the tracking area identifier or tracking area code corresponding to the target access network element; or, when the access network element of the terminal device handover occurs and the tracking area list where the terminal device is located changes, handover-related information is reported to the first network element, including the tracking area list corresponding to the target access network element.

[0027] Optionally, the method further includes: the first network element recording information related to the handover of the terminal device into the first user equipment context, wherein the first user equipment context is the user equipment context of the terminal device managed by the first network element.

[0028] This design allows the first access network element to send a first handover request to the first network element according to reporting rules. If the conditions in the reporting rules are not met, the first access network element may not send a first handover request to the first network element, thereby reducing the signaling overhead between the first access network element and the first network element. For example, if the reporting rules include: reporting handover-related information to the first network element when the terminal device performs an access network element handover, then when the terminal device performs a handover between different cells corresponding to the first access network element, the first access network element may not send a first handover request to the first network element.

[0029] In one possible design, the method further includes: the first network element sending a sixth message to the first access network element, the sixth message being used to configure reporting rules; or, the reporting rules are pre-defined. With this design, the first access network element can accurately determine the reporting rules. Furthermore, if the reporting rules are configured by the sixth message from the first network element, the first network element can configure the reporting rules as needed, thereby improving the flexibility of the reporting rules.

[0030] In one possible design, the method further includes: when a terminal device switches from a fourth network to a third network, the fourth network element sends service information to the first network element; correspondingly, the first network element receives service information from the fourth network element. The fourth network element is a network element in the fourth network used to manage the mobility of the terminal device in the fourth network; the service information is the service information of the terminal device in the fourth network. The first network element sends service information to a second network element. The second network element is a network element in the third network, used to manage the mobility of the terminal device in the third network.

[0031] For example, the service information of a terminal device in a fourth network may include at least one of the following: session context or service context. The service context may include, for example, at least one of the following: perception service context, computation service context, or artificial intelligence (AI) service context.

[0032] This design allows the first network element to obtain the terminal device's service information from the source network when the terminal device switches from the source network to the target network. Based on this information, the first network element can provide services to the terminal device, ensuring service continuity. For example, the first network element sends the terminal device's service information from the source network to the AMF (Application Function) in the target network; the AMF in the target network then sends this information to the network functions in the target network. In this way, the network functions in the target network can provide services to the terminal device based on this information, ensuring service continuity.

[0033] Secondly, embodiments of this application provide a communication method, the execution subject of which may include a first network element. The first network element can be used to manage the connection status of a terminal device in multiple networks, including a first network, a second network, and a third network, and the first network element is located in the first network. Exemplarily, the first network element is a core network element (e.g., an AMF), for example, the first network element may be a C-AMF.

[0034] Optionally, the first network element can be replaced by a module within the first network element. For example, the module within the first network element can be a communication module, a circuit or chip responsible for communication functions (such as a modem chip, or a SoC chip or SIP chip containing a modem core), a chip system, or a processor within the first network element, or it can be a logical node, logical module, or software capable of implementing all or part of the functions of the first network element.

[0035] The following explanation uses the example of the first network element as the subject of execution of this method.

[0036] The method includes: a first network element acquiring the connection status of a terminal device in a second network and / or a third network; the first network element receiving a second message, the second message including information about the terminal device and information about the second network; if the first network and the terminal device have been updated to a disconnected state, and the second network and the terminal device are also in a disconnected state, the first network element, based on the second message, determines a third network that is in a connected state with the terminal device, wherein a second network element exists in the third network, and the second network element is used to manage the mobility of the terminal device in the third network; the first network element sending a third message to the second network element, the third message being used to request the second network element to notify the terminal device to establish a connection with the second network.

[0037] In one possible design, the first network element can obtain the connection status of the terminal device in the second network through the following steps: a third network element or a first access network element sends a fourth message; correspondingly, the first network element receives the fourth message from the third network element or the first access network element, wherein the third network element is a network element in the second network used to manage the mobility of the terminal device in the second network; the first access network element is the serving first access network element of the terminal device; the fourth message is used to indicate that the terminal device is in a disconnected state in the second network. The fourth message is sent by the third network element or the first access network element under the following circumstances: the second network and the terminal device are updated to a disconnected state.

[0038] In one possible design, the first network element can obtain the connection status of the terminal device in the third network through the following steps: the first network element receives a fifth message, which indicates that the terminal device is in a connected state in the third network.

[0039] In some examples, when a terminal device accesses a third network through a first access network element, the first access network element may send a fifth message; correspondingly, the first network element may receive a fifth message from the first access network element, wherein the fifth message is sent by the first access network element when the terminal device accesses the third network through the first access network element.

[0040] In other examples, the second network element sends a fifth message to the first network element in at least one of the following situations: the terminal device accesses the third network, or, if the multiple networks include a fourth network, the terminal device switches from the fourth network to the third network; accordingly, the first network element receives a fifth message from the second network element, the fifth message being sent by the second network element in at least one of the following situations: the terminal device accesses the third network; or, if the multiple networks include a fourth network, the terminal device switches from the fourth network to the third network.

[0041] In some other examples, multiple networks also include a fourth network. When a terminal device switches from the fourth network to the third network, the fourth network element sends a fifth message to the first network element. Correspondingly, the first network element receives the fifth message from the fourth network element. The fifth message is sent by the fourth network element when multiple networks include a fourth network and the terminal device switches from the fourth network to the third network. Here, the fourth network element is a network element within the fourth network used to manage the mobility of the terminal device within the fourth network.

[0042] In one possible design, upon receiving a second message from a fifth network element, where the fifth network element is a network element used to manage user data and / or status, the second message is also used to indicate: a network among multiple networks whose connection status with the terminal device is connected.

[0043] In one possible design, the method further includes: when a handover occurs in the terminal device, the first access network element sends a first handover request according to reporting rules; correspondingly, the first network element receives the first handover request from the first access network element. The first handover request includes information related to the handover of the terminal device; the first handover request is sent by the first access network element according to reporting rules when the terminal device handover occurs, and the reporting rules are one of the following: when the access cell of the terminal device handover occurs, handover-related information is reported to the first network element, including the cell identifier of the target cell; when the access network element of the terminal device handover occurs, handover-related information is reported to the first network element, including the identifier of the target access network element; when the access network element of the terminal device handover occurs and the tracking area where the terminal device is located changes, handover-related information is reported to the first network element, including the tracking area identifier or tracking area code corresponding to the target access network element; or, when the access network element of the terminal device handover occurs and the tracking area list where the terminal device is located changes, handover-related information is reported to the first network element, including the tracking area list corresponding to the target access network element.

[0044] Optionally, the method further includes: the first network element recording information related to the handover of the terminal device into the first user equipment context, wherein the first user equipment context is the user equipment context of the terminal device managed by the first network element.

[0045] In one possible design, the method further includes: the first network element sending a sixth message to the first access network element, the sixth message being used to configure the reporting rules; or, the reporting rules are pre-set.

[0046] In one possible design, the method further includes: when a terminal device switches from a fourth network to a third network, the fourth network element sends service information to the first network element; correspondingly, the first network element receives service information from the fourth network element. The fourth network element is a network element in the fourth network used to manage the mobility of the terminal device in the fourth network; the service information is the service information of the terminal device in the fourth network. The first network element sends service information to a second network element. The second network element is a network element in the third network, used to manage the mobility of the terminal device in the third network.

[0047] For example, the service information of the terminal device in the fourth network may include at least one of the following: session context, or service context. The service context may include, for example, at least one of the following: perception service context, computation service context, or AI service context.

[0048] Thirdly, embodiments of this application provide a communication method that can be applied to a third network element. For example, the method can be applied to a third network element or a module within a third network element. The third network element is a network element in a second network, used to manage the mobility of terminal devices in the second network. Exemplarily, the third network element is a core network element (e.g., an AMF). For example, the third network element can be a network element in a sub-network that implements access and mobility management functions, and can be referred to as a local access and mobility management function (L-AMF). Exemplarily, the module within the third network element can be a communication module, a circuit or chip responsible for communication functions (e.g., a modem chip, or a SoC chip or SIP chip containing a modem core), a chip system, or a processor, or can be a logical node, logical module, or software capable of implementing all or part of the functions of the third network element. The following description uses the application of this method to a third network element as an example.

[0049] The method includes: a third network element receiving a downlink service message, the downlink service message including information about a terminal device and information about a second network. When the second network and the terminal device are in a disconnected state, the third network element sends the terminal device information and the second network information to a first network element. The first network element manages the connection status of the terminal device in multiple networks, including the first network and the second network, and the first network element is located in the first network.

[0050] Using this method, when the second network and the terminal device are in a disconnected state, the third network element can notify the terminal device to establish a connection with the second network through the first network element, thereby enabling communication between the terminal device and the second network, which is beneficial to improving the communication performance of the distributed network architecture.

[0051] In one possible design, when the connection status between the terminal device and the second network is updated to a disconnected state, the third network element reports to the first network element that the terminal device is in a disconnected state in the second network.

[0052] Fourthly, embodiments of this application provide a communication method, the execution subject of which may include a first access network element. Optionally, the first access network element may be replaced by a module within the first access network element. Exemplarily, the module within the first access network element may be a communication module, a circuit or chip responsible for communication functions (such as a modem chip, or a SoC chip or SIP chip containing a modem core), a chip system, or a processor within the first access network element, or may be a logical node, logical module, or software capable of implementing all or part of the functions of the first access network element. The following description uses the example of the execution subject of the method including a first access network element.

[0053] The method includes: when a terminal device undergoes a handover, a first access network element sends a first handover request to the first network element according to a reporting rule. The first handover request includes information related to the handover of the terminal device. The reporting rule is one of the following: when the access cell of the terminal device undergoes a handover, handover-related information is reported to the first network element, including the cell identifier of the target cell; when the access network element of the terminal device undergoes a handover, handover-related information is reported to the first network element, including the identifier of the target access network element; when the access network element of the terminal device undergoes a handover and the tracking area where the terminal device is located changes, handover-related information is reported to the first network element, including the tracking area identifier or tracking area code corresponding to the target access network element; or, when the access network element of the terminal device undergoes a handover and the tracking area list where the terminal device is located changes, handover-related information is reported to the first network element, including the tracking area list corresponding to the target access network element.

[0054] In one possible design, the method further includes: the first access network element receiving a sixth message from the first network element, the sixth message being used to configure reporting rules; or, the reporting rules are pre-defined.

[0055] In one possible design, the method further includes: the first network element recording information related to the handover of the terminal device into the first user equipment context, wherein the first user equipment context is the user equipment context of the terminal device managed by the first network element.

[0056] In one possible design, the method further includes: when a terminal device undergoes a handover, the first access network element sends a second handover request to the fourth network element. The second handover request is used to indicate information related to the handover of the terminal device. The fourth network element is located in the fourth network and is used to manage the mobility of the terminal device in the fourth network.

[0057] In one possible design, the method further includes: the fourth network element recording information related to the handover of the terminal device into the second user equipment context, where the second user equipment context is the user equipment context of the terminal device managed by the fourth network element.

[0058] Fifthly, this application provides a communication device. In some examples, the communication device can be a first network element or a module within a first network element, and the communication device has the functions implemented by the first network element in the first or second aspect described above. In other examples, the communication device can be a third network element or a module within a third network element, and the communication device has the functions implemented by the third network element in the third aspect described above. In still other examples, the communication device can be a first access network element or a module within a first access network element, and the communication device has the functions implemented by the first access network element in the fourth aspect described above.

[0059] In one possible embodiment, the communication device includes modules, units, or means corresponding to the operations involved in any of the first to fourth aspects described above. These modules, units, or means can be implemented in software, hardware, or a combination of both. For example, the communication device includes an interface unit and a processing unit. The interface unit can be used to transmit and receive signals to enable communication between the communication device and other devices; the processing unit can be used to perform some internal operations of the communication device. The functions performed by the processing unit and the interface unit can correspond to the operations involved in any of the first to fourth aspects described above.

[0060] In one possible embodiment, the communication device includes a processor. The processor is capable of executing computer programs or instructions, for example, executing computer programs or instructions stored in memory. When the computer program or instructions are executed, the communication device causes it to perform any of the possible designs in any of the first to fourth aspects described above.

[0061] Optionally, the processor is coupled to the memory via an interface, which is either a memory built into the communication device or an external memory connected to the communication device.

[0062] In one possible embodiment, the communication device includes a processor and an interface circuit, wherein the processor is configured to communicate with other devices via the interface circuit and to perform the methods in any of the possible designs in any of the first to fourth aspects described above.

[0063] Sixthly, this application provides a communication system that may include at least two of a first device, a second device, and a third device. The first device may be a first network element or a module within a first network element, used to perform the operations of the first network element as described in the first or second aspect; the second device may be a third network element or a module within a third network element, used to perform the operations of the third network element as described in the third aspect; and the third device may be a first access network element or a module within a first access network element, used to perform the operations of the first access network element as described in the fourth aspect.

[0064] In some possible designs, the communication system includes a first network element and a third network element.

[0065] In other possible designs, the communication system includes a first network element, a third network element, and a first access network element.

[0066] In some other possible designs, the communication system includes a first network element and a first access network element.

[0067] In some other possible designs, the communication system includes a third network element and a first access network element.

[0068] In a seventh aspect, this application provides a computer-readable storage medium storing a computer program or instructions, wherein when the computer program or instructions are executed, a method in any possible design of any of the first to fourth aspects described above is implemented.

[0069] Eighthly, this application provides a computer program product comprising computer program code, wherein when the computer program code is run, a method in any possible design of any of the first to fourth aspects described above is implemented.

[0070] Ninthly, this application provides a chip that may include at least one processor for executing computer programs or instructions in memory to implement the methods in any possible design of any of the first to fourth aspects described above.

[0071] The technical effects that can be achieved by any of the second to ninth aspects mentioned above can be described with reference to the technical effects that can be achieved by any possible design in the first aspect mentioned above. Where there is overlap, no further discussion will be given. Attached Figure Description

[0072] Figure 1 is an architecture diagram of a communication system provided in an embodiment of this application;

[0073] Figures 2A to 2C are schematic diagrams of several application scenarios provided in the embodiments of this application;

[0074] Figures 3 to 9 are flowcharts of several communication methods provided in the embodiments of this application;

[0075] Figure 10 is a structural diagram of a communication device provided in an embodiment of this application;

[0076] Figure 11 is a structural diagram of another communication device provided in an embodiment of this application. Detailed Implementation

[0077] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the embodiments of this application will be further described in detail below with reference to the accompanying drawings.

[0078] The relevant terms used in the embodiments of this application will be explained below. It should be noted that these explanations are for the purpose of making the embodiments of this application easier to understand, and should not be regarded as a limitation on the scope of protection claimed by this application.

[0079] 1. Terminal equipment, also known as user equipment (UE), terminal, access terminal, subscriber unit, user station, mobile station, mobile station (MS), remote station, remote terminal, mobile device, user terminal, wireless communication equipment, user agent, or user device.

[0080] A terminal device can be a device that provides wireless communication capabilities, such as a handheld device or an in-vehicle device with wireless connectivity. Currently, examples of terminal devices include: mobile phones, satellite mobile terminals, cellular phones, smartphones, tablets, laptops, PDAs, mobile internet devices (MIDs), wearable devices (such as smartwatches, smart bracelets, pedometers, smart glasses, etc.), in-vehicle equipment (such as cars, bicycles, electric vehicles, airplanes, ships, trains, high-speed trains, etc.), satellite terminals, virtual reality (VR) devices, augmented reality (AR) devices, smart point-of-sale (POS) machines, customer-premises equipment (CPE), wireless terminals in industrial control, wireless terminals in self-driving cars, wireless terminals in remote medical surgery, wireless terminals in smart grids, wireless terminals in transportation safety, wireless terminals in smart cities, and wireless terminals in smart homes. Wireless terminals in the home (e.g., refrigerators, televisions, air conditioners, electricity meters, etc.), intelligent robots, robotic arms, cellular phones, cordless phones, session initiation protocol (SIP) phones, wireless local loop (WLL) stations, personal digital assistants (PDAs), handheld devices with wireless communication capabilities, computing devices or other processing devices connected to a wireless modem, flying devices (e.g., intelligent robots, hot air balloons, drones, airplanes), terminals in 5th generation (5G) networks, or terminal devices in future evolved public land mobile networks (PLMNs), etc., are not limited to these in this application embodiment. As an example and not a limitation, in this application embodiment, the terminal device can also be a mobile termination (MT) in an integrated access and backhaul (IAB) node.When an IAB node faces its parent node, it can be considered an endpoint, in which case the IAB node acts as the MT (Mediator).

[0081] 2. An access network element is a network-side device with wireless transceiver capabilities. For example, it's a device in a radio access network (RAN) that provides wireless communication functionality to terminal devices. It can also be called an access network device, RAN device, or RAN node. As an example, the RAN can be an access network within the 3rd Generation Partnership Project (3GPP), such as a 4G network, a 5G network (e.g., a new radio (NR) network), or a future-oriented network. Another example is that the RAN can be an open RAN (O-RAN or ORAN), a cloud radio access network (CRAN), or a communication network combining two or more of these.

[0082] Optionally, the access network element can be a base station, an evolved NodeB (eNodeB), a transmission reception point (TRP), a next-generation NodeB (gNB) in a 5G mobile communication system, a base station in a future mobile communication system, an access node in a wireless fidelity (Wi-Fi or WiFi) system, a wireless relay node, or a wireless backhaul node, etc. Optionally, the base station can be a terrestrial base station or a non-terrestrial base station, such as a satellite or a temporarily deployed drone base station, etc.

[0083] Optionally, the access network element can also be a module or unit that performs some of the functions of the base station, such as a CU, a DU, or a radio unit (RU). A CU can be associated with one or more DUs. CUs and DUs can be set up separately or can be included in the same network element, such as in a baseband unit (BBU). RUs can be included in radio frequency equipment or radio frequency units, such as in a remote radio unit (RRU), an active antenna unit (AAU), or a remote radio head (RRH).

[0084] In some implementations, access network elements may include CU and DU. Access network elements including CU and DU separate the protocol layers of the gNB in ​​the NR system. Some protocol layer functions are centrally controlled by the CU, while the remaining partial or complete protocol layer functions are distributed in the DU, which is centrally controlled by the CU. In a typical protocol stack partitioning scheme, the CU includes radio resource control (RRC) and the corresponding packet data convergence protocol (PDCP), while the DU includes the radio link control (RLC) layer, the medium access control (MAC) layer, and the physical (PHY) layer.

[0085] Optionally, the CU can be further divided into CP and UP. CU-CP is responsible for control plane functions, mainly including RRC and the corresponding PDCP (i.e., PDCP-control plane, PDCP-C) for the control plane. PDCP-C is mainly responsible for control plane data encryption / decryption, integrity protection, and data transmission. CU-UP is responsible for user plane functions, mainly including the Service Data Adaptation Protocol (SDAP) and the corresponding PDCP (i.e., PDCP-user plane, PDCP-U) for the user plane. SDAP is mainly responsible for processing core network data and mapping flows to bearers. PDCP-U is mainly responsible for data plane encryption / decryption, integrity protection, header compression, sequence number maintenance, and data transmission. CU-CP and CU-UP can be connected via the E1 interface. CU-CP represents the gNB connecting to the core network via the NG interface and connecting to the DU via the F1 interface control plane (i.e., F1-C). CU-UP connects to the DU via the F1 interface user plane (i.e., F1-U). Of course, another possible implementation is that PDCP-C is also in CU-UP.

[0086] In different systems, CU (or CU-CP and CU-UP), DU, or RU may have different names, but those skilled in the art will understand their meaning. For example, in an open access network (open RAN, O-RAN, or ORAN) system, CU can also be called open CU (open CU, O-CU), DU can also be called open DU (open DU, O-DU), CU-CP can also be called open CU-CP (open CU-CP, O-CU-CP), CU-UP can also be called open CU-UP (open CU-UP, O-CU-UP), and RU can also be called open RU (open RU, O-RU). For ease of description, this application uses CU, CU-CP, CU-UP, DU, and RU as examples. Any of the units among CU (or CU-CP, CU-UP), DU, and RU in this application can be implemented through software modules, hardware modules, or a combination of software modules and hardware modules.

[0087] When applied to O-RAN, access network elements can also possess AI capabilities. For example, O-RAN includes an intelligent controller. This intelligent controller can be a non-real-time RAN intelligent controller (RIC / non-RT RIC / NRT RIC) or a near-real-time RAN intelligent controller (RIC / near-RT RIC / nRT RIC). A non-real-time RIC can be used to implement non-real-time intelligent management of RAN functions, enabling workflows including model training and updates, and guiding applications / functions in the NRT RIC based on policies. A near-real-time RIC can be used to implement near-real-time intelligent management of the RAN. Through data collection and related operations on the E2 interface, near-real-time control and optimization of O-RAN modules and resources are achieved.

[0088] 3. Core network elements can include control plane network elements and user plane network elements. Control plane network elements include, for example, access management function network elements, unified data management network elements, session management function network elements, policy control function network elements, or network repository function network elements. User plane network elements include, for example, user plane function network elements. The following is an introduction to some network elements in the core network.

[0089] Access management function (AMF) network elements are responsible for access control and mobility management of terminal devices accessing the operator's network. This includes functions such as mobility state management, assigning temporary user identities, authentication, and authorization. In 5G communication systems, this AMF network element can be an AMF network element. In future communication systems, the AMF network element may have other names, without limitation.

[0090] The unified data management network element is responsible for generating authentication credentials, processing user identifiers (such as storing and managing permanent user identities), and managing subscription data. In 5G communication systems, this unified data management network element can be a unified data management (UDM) network element. In future communication systems, this unified data management network element may have other names, without limitation.

[0091] The session management function (SMF) network element is primarily responsible for session management in mobile networks, such as session establishment, modification, and release. It can also assign Internet Protocol (IP) addresses to users and select user plane function (MPF) network elements that provide packet forwarding capabilities. In 5G communication systems, this SMF network element may be a Session Management Function (SMF) network element. In future communication systems, the SMF network element may have other names without limitation.

[0092] The policy control function network element primarily provides policy rules and is also responsible for acquiring user subscription information related to policy decisions. In 4G communication systems, this policy control function network element can be a policy and charging rules function (PCRF) network element. In 5G communication systems, this policy control function network element can be a policy control function (PCF) network element. In future communication systems, the policy control function network element may have other names, without limitation.

[0093] The network repository function (NRF) element primarily provides registration and discovery services for network function services. In 5G communication systems, this NRF element can be a network repository function (NRF) element. In future communication systems, the NRF element may have other names, without limitation.

[0094] User plane function (UDP) network elements are responsible for receiving and forwarding user data. For example, they can receive user data from the DN (Digital Network Node) and transmit it to the terminal equipment via the access network element; UDP network elements can also receive user data from the terminal equipment via the access network element and forward it to the DN. In 5G communication systems, this UDP network element can be a user plane function (UPF) network element. In future communication systems, UDP network elements may have other names, without limitation.

[0095] The term "network element" as used in this application can be replaced with "equipment". For example, core network element and core network equipment have the same meaning. Optionally, the term "network element" can be omitted from the equipment name mentioned in this application. For example, AMF network element and AMF have the same meaning.

[0096] 4. Subnets can be logical subnets composed of network slices, or they can be non-public networks (NPNs).

[0097] Network slicing, also known as a slice, refers to the process of dividing a physical network into multiple network slices. Each network slice constitutes an end-to-end logical subnet, and different network slices are logically isolated from each other. Each network slice can flexibly provide one or more network services as needed, without affecting other network slices.

[0098] Different logical subnets can be identified and distinguished by single network slice selection assistance information (S-NSSAI). Each S-NSSAI may include at least one of the following: slice / service type (SST) and slice differentiator (SD). SST indicates specific characteristics and service types of the network slice; SD, as a supplement to SST, further distinguishes multiple network slice instances that satisfy the same SST, and SD is optional.

[0099] NPN, also known as a private network, refers to a network used for non-public purposes, such as internal networks built in factories, schools, or commercial areas. Non-public NPNs can be divided into two types: standalone non-public networks (SNPNs) and public network integrated NPNs (PNI-NPNs). SNPNs do not rely on public network functionality, while PNI-NPNs do.

[0100] 5. Connection state, also known as connection management (CM) state.

[0101] In a communication system, the connection states between a terminal device and the core network include three types: CM connected state (CM_connected, or simply connected state), CM idle state (CM_idle, or simply idle state), and RRC inactive state (CM_connected with RRC_inactive, or simply inactive state).

[0102] When the terminal device is in the CM idle state, the RRC connection between the terminal device and the access network element is released, the connection between the access network element and the core network element is disconnected, the access network element and the terminal device no longer save the context of the terminal device, and the terminal device can receive broadcast information (such as system information) and paging messages sent by the access network element.

[0103] When a terminal device is in the RRC inactive state, the RRC connection between the terminal device and the access network element is suspended. However, the access network element and the terminal device continue to save the terminal device's context, and the connection between the access network element and the core network element remains. When the terminal device transitions from the inactive state to the connected state, the access network element and the terminal device can quickly restore the RRC connection between the terminal device and the access network element based on the saved terminal device context, enabling the terminal device to quickly return to the connected state.

[0104] When the terminal device is in CM connection state, there is a signaling connection between the terminal device and the core network element, and the two can communicate based on the signaling connection.

[0105] 6. Tracking area (TA) is a concept established for the location management of terminal equipment. Both the terminal equipment and core network elements can obtain the TA of the terminal equipment. A TA can contain multiple cells on the access network side, and each TA can be indicated by a tracking area code (TAC) or a tracking area identity (TAI).

[0106] In this application, multiple cells may belong to one access network element; cells in multiple access network elements may belong to one TA; multiple TAs may belong to one tracking area list (TAL).

[0107] 7. In this application, "instruction" or "for instruction" may include explicit instruction (or direct instruction) and implicit instruction (or indirect instruction). When describing information for instructing A, it may include whether the information explicitly instructs A or implicitly instructs A, but does not necessarily mean that the information carries A.

[0108] The indication methods involved in the embodiments of this application should be understood to cover various methods that enable the party to be indicated to obtain the information to be indicated. The information to be indicated can be sent as a whole or divided into multiple sub-information and sent separately. Moreover, the sending period and / or sending time of these sub-information can be the same or different, without limitation.

[0109] In the embodiments of this application, "information" can be an explicit indication, that is, a direct indication through signaling, or obtained by combining other rules or parameters with parameters indicated by signaling, or by deduction. It can also be an implicit indication, that is, obtained based on rules or relationships, or based on other parameters, or by deduction. No limitation is imposed.

[0110] 8. In this application, communication between different devices can refer to direct communication between different devices (i.e., without the need for relaying or forwarding by other devices), or communication between different devices through other devices (i.e., requiring relaying or forwarding by other devices), or communication between a functional unit within a device and other devices through another functional unit. For example, "sending information to…(terminal)" can be understood as the destination of the information being the terminal, and may include sending information directly or indirectly to the terminal. "Receiving information from…(terminal)" can be understood as the source of the information being the terminal, and may include receiving information directly or indirectly from the terminal. Information may undergo necessary processing between the source and destination ends, such as format changes, digital-to-analog conversion, amplification, filtering, etc., but the destination end can understand the valid information from the source end. Similar expressions in this application can be understood in a similar way, and will not be elaborated further here.

[0111] 9. In this application, the words "exemplarily," "for example," "for instance," and "example" are used to indicate examples, illustrations, or explanations, and are not intended to limit the scope of protection of this application. It should be understood that the examples in this application may also be implemented in other ways. In this application, "of," "corresponding, relevant," and "corresponding" may sometimes be used interchangeably, and it should be noted that their intended meanings are consistent when the distinction is not emphasized.

[0112] 10. In this application, any two of the programs, instructions and code may be substituted for one another.

[0113] 11. In this application, “in the case of…”, “when…”, “if…”, and “if…” can have the same meaning and can be used interchangeably.

[0114] The technical solutions in this application embodiment can be applied to various communication systems. For example, Universal Mobile Telecommunications System (UMTS), Wireless Local Area Network (WLAN), Short-Range Wireless Communication Systems (such as Sidelink, WiFi, Bluetooth, etc.), Wired Networks, Integrated Sensing and Communication (ISAC), Vehicle-to-Everything (V2X) Communication Systems, Device-to-Device (D2D) Communication Systems, Vehicle-to-Everything (V2X) Communication Systems, Machine-to-Machine (M2M) Communication, Machine-Type Communication (MTC), Internet of Things (IoT), 4th Generation (4G) Mobile Communication Systems (such as Long Term Evolution (LTE)), LTE Frequency Division Duplex (FDD) Systems, LTE Time Division Duplex (TDD) Systems, Worldwide Interoperability for Microwave Access (WiMAX) Communication Systems, and 5G Mobile Communication Systems (such as New Radio). No restrictions are imposed on radio (NR) systems, future evolution communication systems, or other similar communication systems.

[0115] This application will present various aspects, embodiments, or features relating to systems that may include multiple devices, components, modules, etc. It should be understood that individual systems may include additional devices, components, modules, etc., and / or may not include all devices, components, modules, etc. discussed in conjunction with the accompanying drawings. Furthermore, combinations of these approaches are also possible.

[0116] Figure 1 illustrates a schematic diagram of a possible communication system. It should be understood that the communication system described in this application is merely an example and should not be construed as limiting the scope of this application. The communication system may include a central network and one or more subnetworks, with one subnetwork shown as an example in the figure. The central network can be used to manage (or maintain) one or more subnetworks; in other words, network elements in the central network can be used to manage (or maintain) network elements in one or more subnetworks; or, network elements in the central network can be used to manage (or maintain) one or more subnetworks.

[0117] The central network may include at least one core network element. For example, the central network may include at least one of the following: access management function network element, unified data management network element, session management function network element, policy control function network element, network repository function network element, or unified data storage network element, etc.

[0118] Access management function network elements in the central network, such as C-AMF, are responsible for access control of terminal devices, maintenance and management of sub-network access information, and paging functions.

[0119] The unified data management network element in the central network, such as the central unified data management (C-UDM), is responsible for generating authentication credentials, processing user identifiers (such as storing and managing permanent user identities), and managing subscription data.

[0120] The subnetwork may include at least one core network element. For example, the subnetwork may include at least one of the following: an access management function network element, or a network function (NF) network element, etc. The NF network elements in the subnetwork may be deployed using a common bus.

[0121] Access management function network elements in subnetworks, also known as access management function network elements in local networks, such as L-AMF, are responsible for access control of terminal devices accessing the subnetwork, as well as mobility management (such as handover) and other functions.

[0122] The NF network elements in the subnetwork include, for example, at least one of the following: a session management function network element in the subnetwork, responsible for session management in the subnetwork, such as session establishment, modification, or release; a sensing management function network element in the subnetwork, for example, a sensing function (SF), responsible for sensing management in the subnetwork; a policy control function network element in the subnetwork, for example, a local policy control function (L-PCF), responsible for providing policy rules in the subnetwork; a unified data storage network element in the subnetwork (for example, a local unified data repository (L-UDR)); or a network repository function network element in the subnetwork (for example, a local network repository function (L-NRF)), etc.

[0123] It should be understood that Figure 1 illustrates the example of L-AMF and SMF being aggregated in one network element; in other words, Figure 1 illustrates the example of aggregation connection functions including L-AMF and SMF, but it is not limited to this. For example, L-AMF and SMF can also be deployed in different network elements.

[0124] It should also be understood that the central network and sub-networks may have other names. For example, the central network may be called the management network, and the sub-network may be called the local network or the distributed sub-network. As long as they have the same function, they are all within the scope of protection of this application.

[0125] Currently, with the development of communication technology, network architecture is gradually evolving from centralized to distributed architecture. A distributed network architecture is illustrated in Figure 1. In a distributed network architecture, terminal devices need to communicate with at least one subnetwork via the AMF (Advanced Component Network).

[0126] Further research is needed on how to improve the communication performance of distributed network architectures, such as how to enable terminal devices to connect to sub-networks.

[0127] Furthermore, in current distributed network architectures, communication systems employ centralized access and mobility management. Regardless of the number of subnetworks a terminal device connects to, a single AMF (Access Management Function) handles unified access and mobility management. Specifically, all subnetwork information is recorded and maintained by a single AMF, and all messages exchanged between the terminal device and network functions within the subnetwork are forwarded by this AMF; in other words, for all subnetworks accessed by the terminal device, this AMF assumes the functions of service provision and proxy.

[0128] This method has at least one of the following problems:

[0129] 1. Poor disaster recovery: All information in the sub-networks is recorded and maintained by a single AMF (Advanced Management Function), and all messages exchanged between terminal devices and NFs (Network Functions) in the sub-networks are forwarded by this AMF. This results in a strong coupling between the AMF and the sub-networks. If the AMF fails, the connections between all sub-networks and the RAN (Radio Router) and the services of the terminal devices will be affected, which is detrimental to disaster recovery.

[0130] 2. It is not conducive to efficient signaling transmission: The messages exchanged between the terminal device and all NFs in the sub-network are forwarded by the same AMF. This AMF is generally located in the central network, while the sub-networks are generally located at the network edge, which results in a long signaling transmission delay and is not conducive to efficient signaling transmission.

[0131] 3. It is not conducive to the closed loop of services within the sub-network (in other words, it is not conducive to the localized closed loop of services): The messages exchanged between the terminal device and all NFs in the sub-network are forwarded by the same AMF, and the AMF is located outside the sub-network. This causes services to be transmitted outside the sub-network, which is not conducive to the closed loop of services within the sub-network and affects service security.

[0132] To address the aforementioned issues, the inventors proposed deploying network elements for implementing access and mobility management functions in both the central network and sub-networks, effectively splitting the access and mobility management functions between the central network and sub-networks. The resulting network structure is shown in Figure 1.

[0133] There is still no reasonable solution for separating access and mobility management functions.

[0134] Based on this, embodiments of this application provide a communication method and apparatus for notifying a terminal device to establish a connection with a second network through a first network element in a first network, thereby enabling communication between the terminal device and the second network and improving the communication performance of the distributed network architecture. The method and apparatus described in this application are based on the same technical concept. Since the principles by which the method and apparatus solve problems are similar, the implementations of the apparatus and method can be mutually referred to, and repeated details will not be elaborated further.

[0135] The following section introduces the application scenarios applicable to the embodiments of this application.

[0136] Figure 2A illustrates an application scenario applicable to embodiments of this application. As shown in Figure 2A, the terminal device is in a disconnected state (e.g., idle state) in sub-network #1; in other words, the connection between the terminal device and L-AMF #1 in sub-network #1 is broken; or, the connection state between the terminal device and L-AMF #1 is disconnected (e.g., idle state). The terminal device is in a connected state in the central network; in other words, a connection has been established between the terminal device and C-AMF in the central network; or, the connection state between the terminal device and C-AMF is connected. L-AMF #1 can communicate with C-AMF.

[0137] Figure 2B illustrates another application scenario applicable to the embodiments of this application. As shown in Figure 2B, the terminal device is in a disconnected state (e.g., idle state) in sub-network #1; in other words, the connection between the terminal device and L-AMF #1 in sub-network #1 is broken; or, the connection between the terminal device and L-AMF #1 is disconnected (e.g., idle state). The terminal device is in a disconnected state (e.g., idle state) in the central network; in other words, the connection between the terminal device and C-AMF in the central network is broken; or, the connection between the terminal device and C-AMF is disconnected (e.g., idle state). The terminal device is in a connected state in sub-network #2; in other words, a connection has been established between the terminal device and L-AMF #2 in sub-network #2; or, the connection between the terminal device and L-AMF #2 is connected. Both L-AMF #1 and L-AMF #2 can communicate with C-AMF.

[0138] Figure 2C illustrates another application scenario applicable to the embodiments of this application. As shown in Figure 2C, the terminal device is in a disconnected state (e.g., idle state) in sub-network #1; in other words, the connection between the terminal device and L-AMF #1 in sub-network #1 is broken; or, the connection state between the terminal device and L-AMF #1 is disconnected (e.g., idle state). The terminal device is in a disconnected state (e.g., idle state) in the central network; in other words, the connection between the terminal device and C-AMF in the central network is broken; or, the connection state between the terminal device and C-AMF is disconnected (e.g., idle state). The terminal device switches from sub-network #3 to sub-network #2; thus, sub-network #3 is the source network of the terminal device, and sub-network #2 is the target network of the terminal device. After the switch, the terminal device is in a connected state in sub-network #2; in other words, a connection has been established between the terminal device and L-AMF #2 in sub-network #2; or, the connection state between the terminal device and L-AMF #2 is connected. Both L-AMF#1 and L-AMF#2 can communicate with C-AMF.

[0139] It should be understood that Figures 2A to 2C are illustrated using subnetworks including L-AMF, SMF, L-PCF, and L-UDR as examples, but are not limited to this. Subnetworks may include more or fewer network elements, without limitation.

[0140] It should also be understood that Figures 2A to 2C illustrate the aggregation of L-AMF and SMF in a single network element, in other words, they illustrate the aggregation connection function including L-AMF and SMF, but are not limited to this. For example, L-AMF and SMF can also be deployed in different network elements.

[0141] The various communication methods provided in the embodiments of this application will be described in detail below with reference to the accompanying drawings. These methods can be applied to the communication system shown in FIG1, but are not limited thereto. The execution subject of the embodiments of this application may include, but is not limited to, at least one of the following: a first network element, a second network element, a third network element, a fourth network element, a fifth network element, and a first access network element.

[0142] The first network element can be a network element in a first network; in other words, a first network element exists in the first network. The first network element can be used to manage (or maintain) the connection status of the terminal device in multiple networks. These multiple networks may include a first network and a second network. Optionally, the multiple networks may also include a third network. The first network is, for example, a central network, and the second and third networks are, for example, sub-networks. Exemplarily, the first network element can be the C-AMF shown in Figures 2A, 2B, or 2C. In this way, the first network element can perform network-level (e.g., sub-network-level) mobility management for the terminal device.

[0143] The second network element can be a network element in the third network; in other words, a second network element exists in the third network. The second network element is used to manage (or maintain) the mobility of the terminal equipment in the third network. For example, the third network can be sub-network #2 in Figure 2B or Figure 2C, and the second network element can be L-AMF #2 in Figure 2B or Figure 2C. In this way, the second network element can perform service-level mobility management for the terminal equipment, such as managing the handover between the terminal equipment and access network elements.

[0144] The third network element can be a network element in the second network; in other words, a third network element exists in the second network. The third network element is used to manage (or maintain) the mobility of the terminal device in the second network. For example, the second network can be sub-network #1 in Figure 2A, Figure 2B, or Figure 2C, and the third network element can be L-AMF #1 in Figure 2A, Figure 2B, or Figure 2C. In this way, the third network element can perform service-level mobility management for the terminal device, such as managing the handover between the terminal device and access network elements.

[0145] The fourth network element can be a network element within a fourth network; in other words, a fourth network element exists within the fourth network. This fourth network element is used to manage (or maintain) the mobility of terminal devices within the fourth network. For example, the fourth network can be a sub-network, such as sub-network #3 in Figure 2C, and the fourth network element can be L-AMF #3 in Figure 2C. Thus, the fourth network element can perform service-level mobility management for terminal devices, such as managing handover between the terminal device and access network elements.

[0146] The fifth network element can be a network element in the first network; in other words, a fifth network element exists in the first network. The fifth network element is used to manage user data and / or status. For example, the first network can be a central network, and the fifth network element can be a UDM or PCF in the central network.

[0147] Optionally, unless otherwise specified, "network element" in the following text can be replaced with a module within a network element. A module within a network element can be a communication module, a circuit or chip responsible for communication functions (such as a modem chip, or a SoC chip or SIP chip containing a modem core), a chip system, or a processor, or it can be a logical node, logical module, or software capable of implementing all or part of the network element's functions.

[0148] It is understood that in the embodiments of this application, at least one of the first network element, second network element, third network element, fourth network element, fifth network element, or first access network element may perform some or all of the steps in the embodiments of this application. These steps or operations are merely examples, and the embodiments of this application may also perform other operations or variations thereof. Furthermore, the various steps may be performed in different orders as presented in the embodiments of this application, and it is not necessarily necessary to perform all the operations in the embodiments of this application.

[0149] Figure 3 is a flowchart illustrating the first communication method provided in an embodiment of this application. This method can be applied to the scenarios shown in Figures 2A, 2B, or 2C. In this method, a first network element in the first network can notify the terminal device to establish a connection with the second network. As shown in Figure 3, the method may include:

[0150] S301: The terminal device sends a service request; correspondingly, the first network element receives the service request from the terminal device.

[0151] The service request can be used to request access to the first network for a terminal device. Optionally, the service request includes information about the first network. The information about the first network may include at least one of the following: the identity (ID) of the first network, or the ID of a first network element.

[0152] Optionally, the terminal device can send a service request to the first network element through the first access network element, which can be the service access network element of the terminal device. The first access network element can either transparently transmit the service request from the terminal device to the first network element, or it can process the service request from the terminal device, for example, by modifying the destination address of the message (i.e., changing it to the address of the first network element), and then send the processed service request to the first network element.

[0153] Service requests can be traditional messages (e.g., registration messages, service request messages, session establishment messages, awareness service establishment requests, or computing service requests) or new messages, without restriction. Optionally, the service request can be a Non-access stratum (NAS) message.

[0154] Service requests may also have other names, such as access message, access request, or request message, without restriction.

[0155] S302: The first network element establishes a connection with the terminal equipment.

[0156] The establishment of a connection between the first network element and the terminal device can be understood as the establishment of a connection between the first network and the terminal device.

[0157] This application does not restrict the way the first network element establishes a connection with the terminal device; for example, the method specified in the protocol can be used.

[0158] In some possible ways, during or after the establishment of a connection between the first network element and the terminal device, the first network element may create a first UE context for the terminal device. Optionally, the first network element may record the connection status of the terminal device in the first network within the first UE context. For example, the first network element may record in the first UE context that the connection status of the terminal device in the first network is "connected".

[0159] In some examples, for each of at least one CM state, the first UE context may include indication information of at least one network with which the terminal device is in that state. For example, for the connected state, the first UE context may include indication information of a first network. This indication information may include, for example, the ID of the first network and / or the ID of a first network element in the first network. As another example, if the terminal device's connected state in a second network is idle, then for the idle state, the first UE context may include indication information of a second network. This indication information may include, for example, the ID of the second network and / or the ID of a third network element in the second network. The third network element can be used to manage (or maintain) the mobility of the terminal device in the second network. Table 1 shows one possible example of the first UE context. It should be understood that Table 1 uses the first and second networks as examples, but is not limited thereto; the first UE context may include indication information of more or fewer networks without limitation.

[0160] Table 1: Example of the first UE context

[0161] In other examples, the first UE context may include: indication information of one or more networks, and indication information of the connection status of the terminal device in each of the one or more networks. For example, the first UE context may include: indication information of a first network, and indication information of the connection status. The indication information of the first network may include, for example, the ID of the first network and / or the ID of a first network element in the first network. As another example, if the connection status of the terminal device in a second network is idle, the first UE context may include: indication information of the second network, and indication information of the idle status. The indication information of the second network may include, for example, the ID of the second network and / or the ID of a third network element in the second network. Table 2 shows another possible example of the first UE context. It should be understood that Table 2 uses the first and second networks as examples, but is not limited thereto; the first UE context may include indication information of more or fewer networks, without limitation.

[0162] Table 2: Example of First UE Context

[0163] In this way, the first UE context can record information about the network (e.g., central network and / or sub-network) currently accessed by the terminal device, as well as the connection status of the terminal device in that network; the first network element can perform mobility management based on the granularity of the network (e.g., central network and / or sub-network).

[0164] S303: The first network element receives information from the terminal equipment and information from the second network.

[0165] Information about the terminal device, such as the terminal device ID, is not restricted.

[0166] The information of the second network includes, for example, at least one of the following: the ID of the second network, or the ID of the third network element. The third network element can be a network element in the second network; in other words, a third network element exists in the second network. The third network element can be used to manage (or maintain) the mobility of terminal devices in the second network.

[0167] In some possible approaches, the fifth network element may send terminal device information and second network information to the first network element; correspondingly, the first network element receives the terminal device information and second network information from the fifth network element, as shown in S303a. The fifth network element can be used to manage user data and / or status. For example, the fifth network element is a C-UDM or PCF in the first network. For instance, when the C-UDM determines that it needs to send data to the terminal device through the second network, the C-UDM may send the terminal device information and second network information to the first network element. Also, for example, when the PCF needs to update the terminal device's policy in the second network (e.g., the terminal device's access management policy (AM policy) and / or terminal policy (UE policy, etc.) in the second network, the PCF may send the terminal device information and second network information to the first network element. Optionally, in this approach, the terminal device information and second network information may be carried in a downlink service message.

[0168] In other possible approaches, the third network element may send terminal device information and second network information to the first network element; correspondingly, the first network element receives terminal device information and second network information from the third network element, as shown in S303b. Optionally, in this approach, the terminal device information and second network information may be carried in a downlink service message or in other messages, without limitation.

[0169] For example, in this approach, when the third network element receives a downlink service message, such as when it receives a downlink service message from the fifth network element, if the second network and the terminal device are in a disconnected state, the third network element can send information about the terminal device and information about the second network to the first network element. The downlink service message includes information about the terminal device and information about the second network.

[0170] Optionally, the downlink service request may be a request message for requesting the sending of downlink messages or data to the terminal device, or a request message for requesting the establishment of a signaling or data transmission connection to the terminal device. The downlink service message may also have other names, such as service message, service request message, request message, or paging request, etc., without limitation.

[0171] In some implementations, the terminal device is in a disconnected state (e.g., idle state) in the second network; in other words, the connection between the terminal device and the third network element in the second network is disconnected; or, the connection between the terminal device and the third network element is in a disconnected state (e.g., idle state). For example, the second network may be subnetwork #1 in Figure 2A, and the third network element may be L-AMF #1 in Figure 2A. The terminal device is in a disconnected state (e.g., idle state) in subnetwork #1; in other words, the connection between the terminal device and L-AMF #1 in subnetwork #1 is disconnected; or, the connection between the terminal device and L-AMF #1 is in a disconnected state (e.g., idle state).

[0172] Optionally, before the first network element receives information from the terminal device and the second network, the terminal device may establish a connection with the second network. After the connection is established, if there is no information exchange between the terminal device and the second network for a long period of time, for example, if the time of no information exchange exceeds a time threshold, the terminal device and the second network may be updated to a disconnected state (e.g., an idle state). The method of obtaining this time threshold is not limited; for example, it may be specified by a protocol.

[0173] Optionally, the process of establishing a connection between the terminal device and the second network may include steps A1 to A4:

[0174] Step A1: The terminal device sends a service request #1 to the first access network element; correspondingly, the first access network element receives the service request #1 from the terminal device.

[0175] Service request #1 is used to request access to the second network for the terminal device. For example, service request #1 may include information about the network to be accessed. This information may include at least one of the following: the type of the network to be accessed, or the ID of the network to be accessed. For instance, if the second network is a logical subnet comprised of network slice #1, the information about the network to be accessed may include at least one of the following: the type of network slice #1, or the ID of network slice #1. Or, for example, if the second network is NPN #1, the information about the network to be accessed may include at least one of the following: the type of NPN #1, or the ID of NPN #1.

[0176] Optionally, the service request #1 can be a traditional message (e.g., a registration message, service request message, session establishment message, awareness service establishment request, or computing service request) or a new message, without limitation. The service request #1 can be a Non-access stratum (NAS) message.

[0177] Service request #1 may also have other names, such as access request, request message, or access message, without restriction.

[0178] Step A2: The first access network element sends service request #2 to the first network element; correspondingly, the first network element receives service request #2 from the first access network element.

[0179] Service request #2 is used to request that the terminal device connect to the second network. For example, service request #2 may include information about the network to be accessed. The specific content of the network information can be found in the description of the network information in step A1, and will not be repeated here.

[0180] Service request #2 may be the same as or different from service request #1. In some examples, after receiving service request #1, the first access network element may directly forward or transparently transmit service request #1 to itself; in this case, service request #2 may be the same as service request #1. In other examples, after receiving service request #1, the first access network element may process service request #1, for example, by modifying the destination address of the message (i.e., modifying it to the address of the first network element), obtaining service request #2, and sending service request #2 to itself; in this case, service request #2 may be different from service request #1.

[0181] Optionally, the service request #2 can be a traditional message (e.g., a registration message, service request message, session establishment message, awareness service establishment request, or computing service request) or a new message, without limitation. The service request #2 can be a NAS message.

[0182] Service request #2 may also have other names, such as access request, request message, or access request, without restriction.

[0183] Optionally, before sending service request #2, the first access network element may determine whether there is a connection between the first access network element and the second network. If there is no connection between the first access network element and the second network, the first access network element may send service request #2 to the first network element; if there is a connection between the first access network element and the second network, the first access network element may send service request #2 to the third network element in the second network.

[0184] Step A3: The first network element sends service request #3 to the third network element based on the network information requested in service request #2; correspondingly, the third network element receives service request #3 from the first network element.

[0185] Service request #3 is used to request that the terminal device be connected to the second network.

[0186] Service request #3 may be the same as or different from service request #2. In some examples, after receiving service request #2, the first network element can directly forward or transparently transmit service request #2 to the third network element. In this case, service request #3 may be the same as service request #2. In other examples, after receiving service request #2, the first network element can process service request #2, for example, modify the destination address of the message (i.e., modify it to the address of the third network element), obtain service request #3, and send service request #3 to the third network element. In this case, service request #3 may be different from service request #2.

[0187] Optionally, before sending service request #3, the first network element may select a second network based on the information of the network to be accessed in service request #2. In some examples, the information of the network to be accessed in service request #2 includes the type of the network to be accessed; the first network element may select a network of that type from among the multiple networks managed by the first network element as the second network. For example, the type of the network to be accessed in service request #2 is network type #1; the multiple networks managed by the first network element include networks #1 to #4. If the type of networks #1 to #3 is network type #1, and the type of network #4 is network type #2, then the first network element may select one of networks #1 to #3 as the second network. In other examples, the information of the second network in service request #2 includes the ID of the network to be accessed; the first network element may select the network corresponding to that ID from among the multiple networks managed by the first network element as the second network.

[0188] In some implementations, before sending service request #3, the first network element may authenticate the terminal device to determine whether to allow the terminal device to access the second network. This application does not restrict the authentication process. If the first network element determines that the terminal device is allowed to access the second network, then the first network element may send service request #3 to the third network element.

[0189] Optionally, the service request #3 can be a traditional message (e.g., a registration message, service request message, session establishment message, awareness service establishment request, or computing service request) or a new message, without limitation. The service request #3 can be a NAS message.

[0190] Service request #3 may also have other names, such as access request, request message, etc., without restriction.

[0191] Step A4: The third network element establishes a connection with the first access network element, thereby providing the terminal equipment with the services of the second network.

[0192] The connection between the third network element and the first access network element can be understood as the connection between the second network and the first access network element.

[0193] Optionally, before establishing a connection with the first access network element, the third network element may determine whether it can provide the service corresponding to service request #3 to the terminal device. If the third network element determines that it can provide the service corresponding to service request #3 to the terminal device, then the third network element may establish a connection with the first access network element. For example, if service request #3 is a service request message, the third network element may determine whether it can provide network services (e.g., subnetwork services) to the terminal device. If the third network element determines that it can provide network services to the terminal device, then the third network element may establish a connection with the first access network element. As another example, if service request #3 is a session establishment request message, the third network element may determine whether it can provide session establishment and other services to the terminal device. If the third network element determines that it can provide session establishment and other services to the terminal device, then the third network element may establish a connection with the first access network element.

[0194] In some implementations, there is a connection between the first access network element and the terminal device. Thus, after the third network element establishes a connection with the first access network element, the third network element and the terminal device are in a connected state, and the terminal device establishes a connection with the second network.

[0195] S304: The first network element sends a first message to the terminal device; correspondingly, the terminal device receives the first message from the first network element.

[0196] The first message is used to instruct the terminal device to establish a connection with the second network. Optionally, the first message may include information about the second network. This information may include, for example, the ID of the second network and / or the ID of a third network element within the second network.

[0197] Optionally, after receiving the first message, the terminal device may establish a connection with the second network, for example, the terminal device may establish a connection with a third network element in the second network.

[0198] In some implementations, the first network element is a network element in a first network (e.g., a central network). When the first network and the terminal device are in a connected state, the first network element can send a first message to the terminal device. The connection between the first network and the terminal device can be replaced by any of the following: the terminal device is in a connected state within the first network; a connection has been established between the terminal device and the first network element; or the connection state between the terminal device and the first network element is a connected state. For example, in the scenario shown in Figure 2A, the first network is a central network, the first network element is C-AMF, and the second network is subnetwork #1. The central network and the terminal device are in a connected state. C-AMF can send a first message to the terminal device, instructing the terminal device to establish a connection with subnetwork #1.

[0199] The first message may also have other names, such as downlink business message, business message, business request message, request message, or paging request, without restriction.

[0200] Using the method shown in Figure 3, the first network element in the first network can notify the terminal device to establish a connection with the second network, thereby enabling communication between the terminal device and the second network, which is beneficial to improving the communication performance of the distributed network architecture.

[0201] Furthermore, in this method, when the second network needs to establish a connection with the terminal device, the first network element can send a first message to the terminal device through the connection between the first network element and the terminal device, thereby notifying the terminal device to establish a connection with the second network. In this way, the first network element does not need to broadcast a message to notify the terminal device to establish a connection with the second network within its corresponding TAL range, thus reducing signaling overhead.

[0202] In some possible approaches, where the multiple networks also include a third network, the method shown in Figure 3 further includes steps S305 to S308:

[0203] S305: The first network element obtains the connection status of the terminal device in the second network and / or the third network.

[0204] The following describes how the first network element obtains the connection status of the terminal device in the second network.

[0205] In some possible scenarios, when the connection between the second network and the terminal device is updated to a disconnected state, a third network element (e.g., L-AMF#1) or a first access network element in the second network sends a fourth message to the first network element. Correspondingly, the first network element receives the fourth message from the third network element or the first access network element, which is sent by the third network element or the first access network element when the connection between the second network and the terminal device is updated to a disconnected state. In other words, when the connection status between the terminal device and the second network is updated to a disconnected state, the third network element or the first access network element can report to the first network element that the terminal device is in a disconnected state in the second network.

[0206] The fourth message can indicate that the terminal device is in a disconnected state in the second network; for example, the fourth message can indicate that the terminal device is in an idle state in the second network. Exemplarily, the fourth message may include: information about the second network, and indication information of the disconnected state. The information about the second network may include, for example, the ID of the second network and / or the ID of a third network element in the first network. For example, if the fourth message includes: the ID of the second network, and indication information of the idle state, then the fourth message can indicate that the terminal device's connection state in the second network is idle.

[0207] Optionally, the terminal device being in a disconnected state in the second network can be replaced by the terminal device being in a disconnected state in the second network and the third network element. For example, the fourth message could indicate that the terminal device and the third network element are in a disconnected state.

[0208] Optionally, after the terminal device and the second network establish a connection, if there is no information exchange between the terminal device and the second network for a long period of time, for example, if the time during which the terminal device and the second network do not exchange information exceeds a time threshold, the terminal device and the second network can be updated to a disconnected state (e.g., an idle state). At this time, the third network element or the first access network element can send a fourth message to the first network element.

[0209] In some implementations, after receiving the fourth message, the first network element can record the connection status of the terminal device in the second network in the first UE context according to the fourth message. For example, the first network element can record in the first UE context that the connection status of the terminal device in the second network is idle, and the recording method is as shown in Table 1 or Table 2 above.

[0210] The following describes how the first network element obtains the connection status of the terminal device in the third network.

[0211] There are multiple ways for the first network element to obtain the connection status of the terminal device in the third network, such as at least one of methods a1 to a3.

[0212] Method a1: The first network element receives the fifth message.

[0213] The fifth message is used to indicate that the terminal device is in a connected state in the third network; in other words, the fifth message can indicate that the terminal device and the third network are in a connected state; or, the fifth message can indicate that the terminal device is in a connected state in the third network.

[0214] For example, the fifth message may include: indication information of the third network, and information on the connection status of the terminal device in the third network. The indication information of the third network may include, for example, the ID of the third network or the ID of the second network element in the third network. For instance, if the fifth message includes: the ID of the third network, and indication information of the CM connection state, then the fifth message may indicate that the connection status of the terminal device in the third network is the CM connection state.

[0215] Optionally, the connection status of the terminal device in the third network can be replaced by the connection status of the terminal device and the second network element in the third network. For example, the fifth message can indicate that the terminal device and the second network element are in a connected state.

[0216] There are several ways to implement the first network element receiving the fifth message, such as mode b1 and / or mode b2.

[0217] Method b1: When a connection is established between the terminal device and the third network, the first network element can receive the fifth message.

[0218] For example, after the terminal device establishes a connection with the first network, or during the process of establishing a connection between the terminal device and the first network, the first network element can receive the fifth message. The process of establishing a connection between the terminal device and the third network can refer to steps A1 to A4 above, except that the second network is replaced by the third network, and the third network element is replaced by the second network element; this will not be repeated here. In some possible ways, when the terminal device accesses the third network, the second network element in the third network (e.g., L-AMF#2) can send the fifth message to the first network element; correspondingly, the first network element receives the fifth message from the second network element, which is sent by the second network element when the terminal device accesses the third network. Optionally, after the second network element establishes a connection with the first access network element, or after the second network element creates or updates the third UE context for the terminal device, the second network element can send the fifth message to the first network element. The third UE context is the UE context of the terminal device managed (or maintained) by the second network element. Optionally, after the second network element establishes a connection with the first access network element, the second network element can create or update the third UE context.

[0219] In other possible implementations, when the terminal device accesses the third network through the first access network element, the first access network element may send a fifth message to the first network element; correspondingly, the first network element receives the fifth message from the first access network element, the fifth message being sent by the first access network element when the terminal device accesses the third network through the first access network element. Optionally, after the second network element establishes a connection with the first access network element, the first access network element may send a fifth message to the first network element.

[0220] Optionally, when the first access network element sends a fifth message to the first network element, the fifth message may also include information related to the first access network element. For example, the information related to the first access network element may include at least one of the following: the ID of the first access network element, the cell ID corresponding to the first access network element, the TAI or TAC corresponding to the first access network element, or the TAL corresponding to the first access network element. This information related to the first access network element may be configured by the operator's network management system (or, in other words, the operation and maintenance management system). For example, when the first access network element is deployed for network access, the operator's network management system (or, in other words, the operation and maintenance management system) may configure information related to the first access network element. Furthermore, during the maintenance of the first access network element, the operator's network management system (or, in other words, the operation and maintenance management system) may modify (or adjust) the information related to the first access network element.

[0221] In method b1, the fifth message may have other names, such as attachment feedback, registration feedback, connection feedback, notification message, or connection status message, without restriction.

[0222] In some possible approaches, in approach b1, the first network element may update or create the first UE context of the terminal device according to the fifth message. Optionally, the first network element may record in the first UE context, according to the fifth message, that the connection state of the terminal device in the third network is connected.

[0223] In some examples, for each of at least one CM state, the first UE context may include indication information of at least one network to which the terminal device is in that state. For example, a fifth message indicates that the terminal device is in a connected state in a third network; for the connected state, the first UE context may include indication information of the third network. This indication information may include, for example, the ID of the third network and / or the ID of a second network element in the third network. Alternatively, if the terminal device's connected state in the second network is an idle state, then for the idle state, the first UE context may include indication information of the second network. This indication information may include, for example, the ID of the second network and / or the ID of a third network element in the second network. The third network element can be used to manage (or maintain) the mobility of the terminal device in the second network. Table 3 shows another possible example of the first UE context. It should be understood that Table 3 is illustrated using the second and third networks as examples, but is not limited thereto; the first UE context may include indication information of more or fewer networks without limitation.

[0224] Table 3: Example of First UE Context

[0225] In other examples, the first UE context may include: indication information of one or more networks, and indication information of the connection status of the terminal device in each of the one or more networks. For example, a fifth message indicates that the terminal device is in a connected state in a third network; the first UE context may include: information about the third network, and indication information of the connected state. The indication information of the third network may include, for example, the ID of the third network or the ID of a second network element in the third network. Alternatively, if the terminal device is in an idle state in a second network, the first UE context may include: indication information of the second network, and indication information of the idle state. The indication information of the second network may include, for example, the ID of the second network and / or the ID of a third network element in the second network. Table 4 shows another possible example of the first UE context. It should be understood that Table 4 uses the second and third networks as examples, but is not limited thereto; the first UE context may include indication information of more or fewer networks, without limitation.

[0226] Table 4: Example of First UE Context

[0227] In this way, the first UE context can record information about the sub-network currently accessed by the terminal device, as well as the connection status of the terminal device in that sub-network; the first network element can perform mobility management based on the granularity of the sub-network.

[0228] Method b2: The multiple networks also include a fourth network (e.g., sub-network #3 in Figure 2C). When the terminal device switches from the fourth network to the third network (e.g., sub-network #2 in Figure 2C), the first network element can receive the fifth message.

[0229] Among them, the third and fourth networks can be sub-networks; in other words, the terminal device switches between sub-networks.

[0230] In some possible ways, when a terminal device switches from a fourth network to a third network, a fourth network element in the fourth network (e.g., L-AMF#3 in Figure 2C) can send a fifth message to a first network element; correspondingly, the first network element receives the fifth message from the fourth network element, which is sent by the fourth network element when the terminal device switches from the fourth network to the third network.

[0231] Optionally, the fourth network element can be determined through the following steps B1 to B3: the terminal device switches from the fourth network to the third network.

[0232] Step B1: The terminal device sends a measurement report to the first access network element; correspondingly, the first access network element receives the measurement report from the terminal device.

[0233] The first access network element can be the service access network element of the terminal device.

[0234] Optionally, the terminal device may periodically or aperiodically send a measurement report to the first access network element. This measurement report may be used to indicate at least one of the following: signal quality (or channel quality) between the terminal device and the serving cell; or, signal quality (or channel quality) between the terminal device and a neighboring cell.

[0235] This measurement report may also have other names, such as air quality monitoring report, etc., without restriction.

[0236] Step B2: The first access network element sends a second handover request to the fourth network element; correspondingly, the fourth network element receives the second handover request from the first access network element.

[0237] The second handover request is used to request the terminal device to be handed over from the source cell to the target cell. The source cell and the target cell can both be cells belonging to the first access network element, meaning the terminal device is performing a cell handover; or, the source cell is a cell belonging to the first access network element, and the target cell is a cell belonging to the second access network element, meaning the terminal device is performing an access network element handover.

[0238] Optionally, before sending the second handover request to the fourth network element, the first access network element may determine, based on the measurement report, whether to hand over the terminal device from the source cell to the target cell. The specific method of determination is not limited, for example, it may be determined in a way specified in the protocol.

[0239] Step B3: The fourth network element determines that the terminal device is switching from the fourth network to the third network.

[0240] For example, if the target cell is a cell managed (or maintained) by a third network, the fourth network element can determine that the terminal device is switching from the fourth network to the third network.

[0241] In some other possible ways, when the terminal device switches from the fourth network to the third network, the second network element in the third network (e.g., L-AMF#2 in Figure 2C) can send a fifth message to the first network element; accordingly, the first network element receives the fifth message from the second network element, which is sent by the second network element when the terminal device switches from the fourth network to the third network.

[0242] Optionally, the second network element can be determined through the following steps C1 to C3: the terminal device switches from the fourth network to the third network.

[0243] Step C1: The terminal device sends a measurement report to the first access network element; correspondingly, the first access network element receives the measurement report from the terminal device.

[0244] Step C2: The first access network element sends a second handover request to the fourth network element; correspondingly, the fourth network element receives the second handover request from the first access network element.

[0245] The specific content of steps C1 to C2 can be referred to steps B1 to B2, and is not limited thereto.

[0246] Step C3: The fourth network element sends a third handover request to the second network element; correspondingly, the second network element receives the third handover request from the fourth network element.

[0247] The third handover request is used to request the terminal device to be handed over from the source cell to the target cell. The fourth network element can send the third handover request directly to the second network element, or the fourth network element can send the third handover request to the second network element through the first network element, without restriction.

[0248] Step C4: The second network element determines that the terminal device is switching from the fourth network to the third network.

[0249] For example, if the source cell is a cell managed (or maintained) by the fourth network and the target cell is a cell managed (or maintained) by the third network, the second network element can determine that the terminal device is switching from the fourth network to the third network.

[0250] Optionally, in method b2, the third network may be selected by the first network element for the terminal device. For example, the first network element may select a third network for the terminal device based on its current location; for instance, it may select a network capable of serving that area as the third network. The current location of the terminal device may be indicated by a handover request from a fourth network element (e.g., the third handover request in step C3), or it may be requested by the first network element from the fourth network element, or it may be indicated by the first access network element from the first network element; there is no limitation on this.

[0251] Optionally, in mode b2, the first network element may record in the first UE context, according to the fifth message, that the connection status of the terminal device in the third network is connected. For details, please refer to the explanation of "the first network element may record in the first UE context, according to the fifth message, that the connection status of the terminal device in the third network is connected" in mode b1, and will not be repeated here.

[0252] Optionally, in method b2, the fifth message is also used to update the connection status between the terminal device and the fourth network element; or, in other words, the fifth message is also used to update the connection status between the terminal device and the fourth network element. The fifth message being used to update the connection status between the terminal device and the fourth network element can be understood as follows: the fifth message can be used to update the connection status between the terminal device and the fourth network element to an idle state; correspondingly, after receiving the fifth message, the first network element can update the connection status between the terminal device and the fourth network element to an idle state; or, the fifth message can be used to update the connection status between the terminal device and the fourth network to an idle state; correspondingly, after receiving the fifth message, the first network element can update the connection status between the terminal device and the fourth network element to an idle state.

[0253] In some examples, if for each of at least one CM state, the first UE context includes indication information of at least one network with which the terminal device is in that state, then in mode b2, the first network element can adjust the first UE context. For example, the ID of the fourth network and the ID of the fourth network element can be deleted from the connected state entry in the first UE context, and the ID of the fourth network and the ID of the fourth network element can be added to the idle state entry.

[0254] In other examples, if the first UE context includes indication information of one or more networks and indication information of the connection status of the terminal device in each of the one or more networks, then in mode b2, the first network element can adjust the first UE context, for example, the CM state corresponding to the fourth network can be changed to the idle state.

[0255] In method b2, the fifth message may have other names, such as switch request message, without restriction.

[0256] Method a2:

[0257] Method a2 includes steps D1 to D2:

[0258] Step D1: The first network element selects the second network element in the third network for the terminal device.

[0259] Optionally, the first network element may receive service request #a2 from the first access network element, and select a third network based on the information of the network requested in service request #a2, thereby selecting a second network element in the third network for managing (or maintaining) the mobility of the terminal device in the third network. The specific content of the service request #a2 received by the first network element from the first access network element can be found in step A2 above; the specific content of the first network element selecting the third network based on the information of the network requested in service request #a2 can be found in step A3 above, which explains that "the first network element may select a second network based on the information of the network requested in service request #2," except that the second network is replaced with the third network, the third network element with the second network element, and service request #2 with service request #a2, and will not be elaborated further.

[0260] In some possible approaches, the first network element may select a second network element from the third network for the terminal device during the connection establishment process between the terminal device and the third network. Optionally, the connection establishment process between the terminal device and the third network can refer to steps A1 to A4 above, except that the second network is replaced by the third network, which will not be described again.

[0261] Step D2: The first network element determines the connection status of the terminal device in the third network.

[0262] For example, after determining the second network element, the first network element can determine that the terminal device and the third network are in a connected state; in other words, after determining the second network element, the first network element can determine that the terminal device is in a connected state in the third network.

[0263] Optionally, the connection status of the terminal device in the third network can be replaced by the connection status of the terminal device and the second network element in the third network. For example, after determining the second network element, the first network element can determine that the terminal device and the second network element are in a connected state.

[0264] Method a3:

[0265] Method a3 includes steps E1 to E4:

[0266] Step E1: The first network element selects the second network element in the first network for the terminal device.

[0267] For details on step E1, please refer to step D1, and will not be repeated here.

[0268] Step E2: The first network element sends an instruction message to the second network element; correspondingly, the second network element receives the instruction message from the first network element.

[0269] The instruction message is used to instruct the second network element and the terminal device to establish a connection; or, the instruction message is used to request the terminal device to access the third network. For example, the specific content of the instruction message can be referred to as service request #3 in step A3, except that the second network is replaced with the third network, and will not be repeated here.

[0270] Indication messages can be traditional or new types of messages, without restriction. Indication messages can also have other names, such as access messages or service requests, without restriction.

[0271] Step E3: The second network element sends an acknowledgment message to the first network element; correspondingly, the first network element receives the acknowledgment message from the second network element.

[0272] The confirmation message is used to confirm the establishment of a connection between the second network element and the terminal device; or, the confirmation message is used to indicate that the second network element agrees to allow the terminal device to access the third network.

[0273] Confirmation messages can be traditional messages (e.g., attachment feedback, registration feedback, or connection feedback) or new messages; there are no restrictions. Confirmation messages can also have other names, such as response messages; there are no restrictions.

[0274] Step E4: The first network element determines the connection status of the terminal device in the third network based on the confirmation message.

[0275] For example, after receiving the confirmation message, the first network element determines that the terminal device and the third network are in a connected state; in other words, after receiving the confirmation message, the first network element can determine that the terminal device is in a connected state in the third network.

[0276] Optionally, the connection status of the terminal device in the third network can be replaced by the connection status of the terminal device and the second network element in the third network. For example, after receiving an acknowledgment message, the first network element can determine that the terminal device and the second network element are in a connected state.

[0277] In some possible scenarios, when the terminal device and the third network are connected, the network elements in the third network that are connected to the terminal device may change. Optionally, when the terminal device and the third network are connected, the terminal device may switch from a sixth network element in the third network to a second network element in the third network. The sixth network element can be used to manage (or maintain) the mobility of the terminal device in the third network. For example, the third network may be a subnetwork, and the sixth network element may be an L-AMF.

[0278] In some examples, if the sixth network element fails, the second network element serves as a backup. In this case, terminal devices connected to the sixth network element can switch from the sixth network element to the second network element.

[0279] In other examples, the load on the sixth network element is high; for example, the load on the sixth network element exceeds a load threshold. In this case, the terminal device connected to the sixth network element can switch from the sixth network element to the second network element. The load threshold can be pre-set, such as as specified in the protocol; or it can be determined by the sixth network element; or it can be notified to the sixth network element by other network elements (e.g., the first network element), and is not limited thereto.

[0280] Optionally, when the terminal device can switch from the sixth network element to the second network element, the sixth network element can notify the first network element to change the network element connected to the terminal device from the sixth network element to the second network element. In this case, the connection state of the terminal device in the third network remains connected; only the network element connected to the terminal device changes from the sixth network element to the second network element. Accordingly, the first network element can change the network element connected to the terminal device from the sixth network element to the second network element. For example, the first network element can change the network element ID connected to the terminal device in the first UE context from the ID of the sixth network element to the ID of the second network element.

[0281] S306: The first network element receives the second message, which includes information about the terminal device and information about the second network.

[0282] The specific content of the terminal device information and the second network information can be found in the description of the terminal device information and the second network information in S303, and will not be repeated here.

[0283] In some possible implementations, the fifth network element may send a second message to the first network element; correspondingly, the first network element receives the second message from the fifth network element, as shown in S306a. The fifth network element can be used to manage user data and / or status. For example, the fifth network element is a C-UDM or PCF in the first network. For instance, when the C-UDM determines that it needs to send data to the terminal device through the second network, the C-UDM may send a second message to the first network element. Also, for example, when the PCF needs to update the terminal device's policy in the second network (e.g., the terminal device's AM policy and / or UE policy in the second network), the PCF may send a second message to the first network element. Optionally, in this implementation, the second message may be a downlink service message. The first network is, for example, a central network, and the second network is, for example, a sub-network; thus, a network element in the central network may trigger the second message.

[0284] Optionally, when the first network element receives a second message from the fifth network element, the second message further indicates that the network among the multiple networks whose connection status with the terminal device is connected. Then, the first network element selects a third network based on the network among the multiple networks whose connection status with the terminal device is connected, thereby selecting a second network element in the third network.

[0285] The second message can indicate in various ways that the connection status between the terminal device and the network among multiple networks is connected. An example is provided below.

[0286] In some examples, the second message may include indication information of networks among multiple networks where the connection status with the terminal device is connected. For example, if the networks among multiple networks where the connection status with the terminal device is connected include networks #1 to #2, the second message may include the ID of network #1 and the ID of network #2. As another example, if the networks among multiple networks where the connection status with the terminal device is connected include networks #1 to #2, network #1 includes AMF#1, and network #2 includes AMF#2, the second message may include the ID of AMF#1 and the ID of AMF#2.

[0287] In other examples, the second message may include: indication information of some or all of the plurality of networks, and indication information of the connection status between each of the plurality of networks and the terminal device. For example, if the plurality of networks includes networks #1 to #3, the second message may include: the ID of network #1, and indication information of the connection status between network #1 and the terminal device; the ID of network #2, and indication information of the connection status between network #2 and the terminal device; and the ID of network #3, and indication information of the connection status between network #3 and the terminal device. As another example, if the plurality of networks includes networks #1 to #3, network #1 includes AMF#1, network #2 includes AMF#2, and network #3 includes AMF#3, the second message may include: the ID of AMF#1, and indication information of the connection status between AMF#1 and the terminal device; the ID of AMF#2, and indication information of the connection status between AMF#2 and the terminal device; and the ID of AMF#3, and indication information of the connection status between AMF#3 and the terminal device.

[0288] In other possible approaches, a third network element (e.g., L-AMF#1) may send a second message to a first network element; correspondingly, the first network element receives the second message from the third network element, as shown in S306b. Optionally, in this approach, the second message may be a downlink service message or other messages, without limitation. The second network may be, for example, a subnetwork, in which network elements within the subnetwork may trigger the second message.

[0289] For example, in this approach, when the third network element receives a downlink service message, such as when it receives a downlink service message from the fifth network element, if the second network and the terminal device are in a disconnected state, the third network element can send information about the terminal device and information about the second network to the first network element. The downlink service message includes information about the terminal device and information about the second network.

[0290] For details regarding the specific content of downlink service requests, please refer to the description of downlink service requests in S303, which will not be repeated here.

[0291] Optionally, before the first network element receives the second message, the terminal device and the second network may be updated to a disconnected state. For example, before the first network element receives the second message, the terminal device may establish a connection with the second network; after the connection is established, if there is no information exchange between the terminal device and the second network for a long period of time—for example, if the time of no information exchange exceeds a time threshold—then the terminal device and the second network may be updated to a disconnected state (e.g., an idle state).

[0292] This application does not restrict the order of S305 and S306.

[0293] S307: When the first network and the terminal device have been updated to a disconnected state, and the second network and the terminal device are in a disconnected state, the first network element determines the third network that is in a connected state with the terminal device based on the second message.

[0294] Wherein, after the first network element in the first network establishes a connection with the terminal device, if there is no information exchange between the terminal device and the first network for a long period of time, for example, if the time during which the terminal device and the first network do not exchange information exceeds a time threshold, the first network element can determine that the terminal device and the first network can be updated to a disconnected state (e.g., an idle state).

[0295] Specifically, the first network element can determine whether the second network and the terminal device are in a disconnected state based on the connection status of the terminal device in the second network obtained in S305. For example, if the connection status of the terminal device in the second network obtained by the first network element in S305 is a disconnected state (e.g., idle state), then the first network can determine that the second network and the terminal device are in a disconnected state (e.g., idle state).

[0296] Optionally, in S307, when the first network and the terminal device have been updated to a disconnected state, and the second network and the terminal device are in a disconnected state, the first network element can determine the terminal device based on the terminal device information in the second message; and determine the third network that is in a connected state with the terminal device based on the connection status of the terminal device in the third network obtained in S305.

[0297] S308: The first network element sends a third message to the second network element (e.g., L-AMF#2) in the third network; correspondingly, the second network element receives the third message from the first network element.

[0298] The third message is used to request the second network element to notify the terminal device to establish a connection with the second network.

[0299] Optionally, the third message may include information about the terminal device and information about the second network. The specific content of the terminal device information and the second network information can be found in the descriptions of the terminal device information and the second network information in S303, and will not be repeated here.

[0300] The second and third messages may be the same or different. In some examples, after receiving the second message, the first network element may forward or transparently transmit the second message to the second network element. In this case, the second and third messages may be the same. In other examples, after receiving the second message, the first network element may process the second message, for example, modify the destination address (i.e., modify it to the address of the second network element), obtain the third message, and send the third message to the second network element. In this case, the second and third messages may be different.

[0301] For example, in the scenario shown in Figure 2B or Figure 2C, the first network is the central network, the first network element is C-AMF, the second network is sub-network #1, the third network is sub-network #2, and the second network element is L-AMF #2. The central network and the terminal device have been updated to a disconnected state, and sub-network #1 and the terminal device are in a disconnected state, while sub-network #2 and the terminal device are in a connected state. C-AMF can send a third message to L-AMF #2 in sub-network #2, which requests L-AMF #2 to notify the terminal device to establish a connection with sub-network #1.

[0302] Optionally, after receiving the third message, the second network element sends message #1 to the terminal device; correspondingly, the terminal device receives message #1 from the second network element.

[0303] Message #1 instructs the terminal device to establish a connection with the second network. Optionally, message #1 may include information about the second network. The specific content of the second network information can be found in the description of the second network information in S303, and will not be repeated here.

[0304] Optionally, after receiving message #1, the terminal device may establish a connection with the second network, for example, the terminal device may establish a connection with a third network element in the second network.

[0305] Among them, message #1 can be a downlink business message or other messages, without limitation.

[0306] In this method, the first network element can be used to manage the connection status of terminal devices in multiple networks. For example, the first network element can be a network element in the central network that implements access and mobility management functions. The second network element is used to manage the mobility of terminal devices in a third network. For example, the second network element can be a network element in a sub-network that implements access and mobility management functions, thereby splitting access and mobility management functions to achieve distributed mobility management. In this way, signaling between the terminal device and network functions in the third network can be forwarded through the second network element, without having to go through the first network element. If the first network element fails, the terminal device can interact with network functions in the third network through the second network element, thereby ensuring service continuity and avoiding or reducing the impact of the first network element on services.

[0307] Furthermore, in this method, the second network element in the third network is used to manage the mobility of terminal devices within the third network. Thus, signaling between the terminal device and network functions in the third network can be forwarded through the second network element, bypassing the first network element. Since the second network element is located in the third network, the transmission latency of signaling forwarded through the second network element is generally less than that forwarded through the first network element, thereby reducing signaling transmission latency. In addition, the forwarding of signaling between the terminal device and network functions in the third network through the second network element allows signaling to be transmitted within the third network, thereby improving service security and meeting the requirement of closed-loop service within the sub-network.

[0308] Furthermore, in this method, the first network element can know the connection status of the terminal device in the second network and / or the third network. For example, the first network element can know the connection status of the terminal device in the sub-network, so that the terminal device can be effectively managed according to the connection status, which is beneficial to improving communication performance.

[0309] Furthermore, using this method, when the second network needs to establish a connection with the terminal device, the first network element can notify the terminal device to establish a connection with the second network through the second network element that is already connected to the terminal device. In this way, the first network element does not need to broadcast messages to notify the terminal device to establish a connection with the second network within its corresponding TAL range, thereby reducing signaling overhead.

[0310] Among some possible approaches, the method shown in Figure 3 further includes step F1:

[0311] Step F1: When a terminal device is switched, the first access network element sends a first switch request to the first network element according to the reporting rules; correspondingly, the first network element receives the first switch request from the first access network element. The first switch request is sent by the first access network element according to the reporting rules when the terminal device is switched.

[0312] The first access network element can be the current serving access network element of the terminal device; or, the first access network element can be the source access network element of the terminal device.

[0313] Optionally, before sending the first handover request to the first network element, the first access network element may determine, based on the measurement report, whether to hand over the terminal device from the source cell to the target cell. The specific method of determination is not limited; for example, it may be determined using a method specified in the protocol. This measurement report may be the measurement report from step B1, the specific content of which can be found in step B1 and will not be repeated here.

[0314] The first handover request can be used to indicate handover-related information for the terminal device; the reporting rules are as follows: 1. When the access cell of the terminal device is handed over, the handover-related information is reported to the first network element, including the cell identifier of the target cell; 2. When the access network element of the terminal device is handed over, the handover-related information is reported to the first network element, including the identifier of the target access network element; 3. When the access network element of the terminal device is handed over and the TA of the terminal device changes, the handover-related information is reported to the first network element, including the TAC or TAI corresponding to the target access network element; or, 4. When the access network element of the terminal device is handed over and the TAL of the terminal device changes, the handover-related information is reported to the first network element, including the TAL corresponding to the target access network element.

[0315] The following explanation of step F1 will be based on the specific content of the reporting rules.

[0316] 1. The reporting rule is as follows: When a handover occurs in the access cell of a terminal device, the handover-related information is reported to the first network element. The handover-related information includes the cell identifier of the target cell.

[0317] When a terminal device hands over from a source cell to a target cell, the first access network element can send a first handover request to the first network element to report handover-related information. In other words, whenever a terminal device hands over, the first access network element can send a first handover request to the first network element to report handover-related information. For example, when a terminal device hands over from cell #1 to cell #2, the first access network element can send a first handover request to the first network element to report handover-related information.

[0318] For example, if the reporting rule is: when the access cell of the terminal device is switched, the switching-related information reported to the first network element includes the cell identifier of the target cell, and the terminal device switches from cell #1 to cell #2, then the first access network element can send a first switching request to the first network element. The first switching request may include: the cell identifier of cell #2.

[0319] 2. The reporting rule is as follows: When a handover occurs in the access network element of a terminal device, the handover-related information is reported to the first network element. The handover-related information includes the identifier of the target access network element.

[0320] When a terminal device switches from a source access network element to a target access network element, the first access network element can send a first handover request to the first network element to report handover-related information. In other words, whenever a terminal device switches access network elements, the first access network element can send a first handover request to the first network element to report handover-related information. For example, if the terminal device switches from cell #1 to cell #2, where cell #1 is the cell of access network element #1 and cell #2 is the cell of access network element #2, then access network element #1 can send a first handover request to the first network element to report handover-related information.

[0321] When a terminal device hands over from a source cell to a target cell, and both the source and target cells belong to the first access network element, the first access network element may not send a first handover request to the first network element, i.e., it may not report handover-related information to the first network element. For example, if the terminal device hands over from cell #1 to cell #2, and both cell #1 and cell #2 belong to access network element #1, then access network element #1 may not send a first handover request to the first network element, i.e., it may not report handover-related information to the first network element.

[0322] For example, if the reporting rule is: when a handover occurs in the access network element of the terminal device, the handover-related information is reported to the first network element, and the handover-related information includes the identifier of the target access network element, and the terminal device is handover from cell #1 to cell #2, where cell #1 is the cell of access network element #1 and cell #2 is the cell of access network element #2, then access network element #1 can send a first handover request to the first network element, and the first handover request may include: the identifier of access network element #2.

[0323] 3. The reporting rule is as follows: When the access network element of the terminal device changes and the TA where the terminal device is located changes, the relevant information of the handover shall be reported to the first network element. The relevant information of the handover includes the TAC or TAI corresponding to the target access network element.

[0324] When a terminal device switches from a source access network element to a target access network element, and the source cell of the source access network element and the target cell of the target access network element belong to different TAs, the first access network element (i.e., the source access network element) can send a first handover request to the first network element in order to report handover-related information to the first network element. For example, if the terminal device switches from cell #1 to cell #2, where cell #1 is the cell of access network element #1 and cell #2 is the cell of access network element #2, and cell #1 belongs to TA #1 and cell #2 belongs to TA #2, then access network element #1 can send a first handover request to the first network element in order to report handover-related information to the first network element.

[0325] When a terminal device hands over from a source cell to a target cell, and both the source and target cells belong to the first access network element, the first access network element may not send a first handover request to the first network element, i.e., it may not report handover-related information to the first network element. For example, if the terminal device hands over from cell #1 to cell #2, and both cell #1 and cell #2 belong to access network element #1, then access network element #1 may not send a first handover request to the first network element, i.e., it may not report handover-related information to the first network element.

[0326] When a terminal device hands over from a source access network element to a target access network element, and the source cell of the source access network element and the target cell of the target access network element belong to the same TA, the first access network element may not send a first handover request to the first network element, that is, it may not report handover-related information to the first network element. For example, if the terminal device hands over from cell #1 to cell #2, where cell #1 is a cell of access network element #1 and cell #2 is a cell of access network element #2, and both cell #1 and cell #2 belong to TA #1, then access network element #1 may not send a first handover request to the first network element, that is, it may not report handover-related information to the first network element.

[0327] For example, if the reporting rule is: when the access network element of the terminal device changes and the TA where the terminal device is located changes, the handover-related information is reported to the first network element. The handover-related information includes the TAC or TAI corresponding to the target access network element. The terminal device is handover from cell #1 to cell #2. Cell #1 is the cell of access network element #1 and cell #2 is the cell of access network element #2. Cell #1 belongs to TA #1 and cell #2 belongs to TA #2. Then access network element #1 can send a first handover request to the first network element. The first handover request may include: the TAI or TAC of TA #2.

[0328] 4. The reporting rule is as follows: When the access network element of the terminal device is switched and the TAL of the terminal device changes, the switching-related information shall be reported to the first network element. The switching-related information includes the TAL corresponding to the target access network element.

[0329] When a terminal device switches from a source access network element to a target access network element, and the source cell of the source access network element and the target cell of the target access network element belong to different TALs, the first access network element (i.e., the source access network element) can send a first handover request to the first network element in order to report handover-related information to the first network element. For example, if the terminal device switches from cell #1 to cell #2, where cell #1 is the cell of access network element #1 and cell #2 is the cell of access network element #2, cell #1 belongs to TA#1 and TA#1 belongs to TAL#1, and cell #2 belongs to TA#2 and TA#2 belongs to TAL#2, then access network element #1 can send a first handover request to the first network element in order to report handover-related information to the first network element.

[0330] When a terminal device hands over from a source cell to a target cell, and both the source and target cells belong to the first access network element, the first access network element may not send a first handover request to the first network element, i.e., it may not report handover-related information to the first network element. For example, if the terminal device hands over from cell #1 to cell #2, and both cell #1 and cell #2 belong to access network element #1, then access network element #1 may not send a first handover request to the first network element, i.e., it may not report handover-related information to the first network element.

[0331] When a terminal device hands over from a source access network element to a target access network element, and the source cell of the source access network element and the target cell of the target access network element belong to the same TA, the first access network element may not send a first handover request to the first network element, that is, it may not report handover-related information to the first network element. For example, if the terminal device hands over from cell #1 to cell #2, where cell #1 is a cell of access network element #1 and cell #2 is a cell of access network element #2, and both cell #1 and cell #2 belong to TA #1, then access network element #1 may not send a first handover request to the first network element, that is, it may not report handover-related information to the first network element.

[0332] When a terminal device hands over from a source access network element to a target access network element, and the source cell of the source access network element and the target cell of the target access network element belong to different TAs but to the same TAL, the first access network element may not send a first handover request to the first network element, i.e., it may not report handover-related information to the first network element. For example, if the terminal device hands over from cell #1 to cell #2, cell #1 is the cell of access network element #1, cell #2 is the cell of access network element #2, cell #1 belongs to TA #1, cell #2 belongs to TA #2, and both TA #1 and TA #2 belong to TAL #1, then access network element #1 may not send a first handover request to the first network element, i.e., it may not report handover-related information to the first network element.

[0333] For example, if the reporting rule is: when the access network element of the terminal device is switched and the TAL of the terminal device changes, the switching-related information is reported to the first network element. The switching-related information includes the TAL corresponding to the target access network element, the terminal device switches from cell #1 to cell #2, cell #1 is the cell of access network element #1, cell #2 is the cell of access network element #2, cell #1 belongs to TA#1, TA#1 belongs to TAL#1, cell #2 belongs to TA#2, TA#2 belongs to TAL#2, then access network element #1 can send a first switching request to the first network element. The first switching request may include: TAL#2.

[0334] Optionally, before sending the first handover request to the first network element according to the reporting rules, the first access network element may determine the reporting rules. There may be multiple ways to determine the rules, such as method c1 or method c2.

[0335] Method c1: The first network element sends a sixth message to the first access network element; correspondingly, the first access network element receives the sixth message from the first network element.

[0336] The sixth message is used to configure (or indicate) the reporting rules. This application does not restrict the specific method by which the sixth message configures or indicates the reporting rules; for example, it can indicate them directly or indirectly. In this way, the first access network element can accurately determine the reporting rules based on the sixth message.

[0337] In some implementations, the first network element may send a sixth message to the first access network element after receiving the fifth message. The specific content of the fifth message can be found in the description of the fifth message in method a1, and will not be repeated here. For example, during the process of a terminal device accessing the first network, the first network element may send a sixth message to the first access network element after receiving the fifth message.

[0338] In other implementations, the first network element may send a sixth message to the first access network element upon request. For example, after determining that a handover from the source cell to the target cell is to be performed, the first access network element may request the first network to report rules.

[0339] The sixth message can be a traditional message or a new message, without restriction.

[0340] Using method c1, the first access network element can accurately determine the reporting rules. Furthermore, in this method, the reporting rules are configured by the sixth message from the first network element; therefore, the first network element can configure the reporting rules as needed, thereby improving the flexibility of the reporting rules.

[0341] Method c2: The reporting rules are pre-defined, such as those specified in the protocol. In this way, the first access network element can accurately determine the reporting rules.

[0342] Reporting rules may have other names, such as reporting strategy, switching reporting rules, or location information reporting granularity, without restriction.

[0343] Optionally, after step F1, the method shown in Figure 3 further includes step F2:

[0344] Step F2: The first network element can record information related to the handover of the terminal device into the first UE context.

[0345] Optionally, the first network element may record handover-related information with the terminal device in the first UE context. This can be understood as the first network element updating the information related to the access network element accessed by the terminal device in the first UE context based on the handover-related information. For example, the access network element-related information includes at least one of the following: the ID of the access network element, the cell ID corresponding to the access network element, the TAI or TAC corresponding to the access network element, or the TAL corresponding to the access network element. The information related to the access network element accessed by the terminal device can be understood as the location information of the terminal device.

[0346] In some examples, if the first handover request includes the cell identifier of the target cell, the first network element can update the information related to the access network element accessed by the terminal device in the first UE context to the cell identifier of the target cell. For example, if the first handover request includes the cell identifier of cell #2, the first network element can update the information related to the access network element accessed by the terminal device in the first UE context to the cell identifier of cell #2.

[0347] In other examples, if the first handover request includes the identifier of the target access network element, the first network element can update the information related to the access network element accessed by the terminal device in the first UE context to the identifier of the target access network element. For example, if the first handover request includes the identifier of access network element #2, the first network element can update the information related to the access network element accessed by the terminal device in the first UE context to the identifier of access network element #2.

[0348] In other examples, if the first handover request includes the TAI or TAC corresponding to the target access network element, the first network element can update the information related to the access network element accessed by the terminal device in the first UE context to the TAI or TAC corresponding to the target access network element. For example, if the first handover request includes the TAI or TAC of TA#2, the first network element can update the information related to the access network element accessed by the terminal device in the first UE context to the TAI or TAC of TA#2.

[0349] In other examples, if the first handover request includes the TAL corresponding to the target access network element, the first network element can update the information related to the access network element accessed by the terminal device in the first UE context to: the TAL corresponding to the target access network element. For example, if the first handover request includes: TAL#2, the first network element can update the information related to the access network element accessed by the terminal device in the first UE context to: TAL#2.

[0350] In this way, the first access network element can send a first handover request to the first network element according to the reporting rules. If the conditions in the reporting rules are not met, the first access network element may not send a first handover request to the first network element, thereby reducing the signaling overhead between the first access network element and the first network element. For example, if the reporting rules include: reporting handover-related information to the first network element when the terminal device performs an access network element handover, then when the terminal device performs a handover between different cells corresponding to the first access network element, the first access network element may not send a first handover request to the first network element.

[0351] Among some possible approaches, the method shown in Figure 3 further includes step G1:

[0352] Step G1: The first access network element sends a second handover request to the fourth network element; correspondingly, the fourth network element receives the second handover request from the first access network element.

[0353] The second handover request is used to indicate information related to the handover of the terminal device. The specific content of the information related to the handover of the terminal device can be found in the explanation of the handover-related information in step F1, and will not be repeated here.

[0354] The details of step G1 can be found in step B2, and will not be repeated here.

[0355] Optionally, after step G1, the method shown in Figure 3 further includes step G2:

[0356] Step G2: The fourth network element records the handover-related information with the terminal device into the second UE context. The second UE context is the UE context of the terminal device managed (or maintained) by the fourth network element.

[0357] The details of step G2 can be found in step F2, except that the first network element is replaced with the fourth network element and the first handover request is replaced with the second handover request.

[0358] Optionally, upon receiving the second handover request, the second network element may trigger a handover process, such as triggering an Xn handover or an N2 handover, thereby ensuring service continuity of the terminal device in different networks (e.g., different sub-networks). This application does not limit the specific handover method; for example, it may be performed using a method specified in the protocol.

[0359] In some possible approaches, the method shown in Figure 3 further includes steps H1 to H2:

[0360] Step H1: When a terminal device switches from a fourth network (e.g., sub-network #3) to a third network (e.g., sub-network #2), the fourth network element (e.g., L-AMF #3) sends service information (hereinafter referred to as first service information) to the first network element; correspondingly, the first network element receives the first service information from the fourth network element.

[0361] The first service information refers to the service information of the terminal device in the fourth network. For example, the service information of the terminal device in the fourth network may include at least one of the following: session context, or service context. The service context may include, for example, at least one of the following: perception service context, computation service context, or AI service context.

[0362] Optionally, before sending the terminal device's service information in the fourth network to the first network element, the fourth network element may obtain the terminal device's service information in the fourth network. For example, the fourth network element may obtain the terminal device's service information in the fourth network through steps I1 to I2.

[0363] Step I1: The fourth network element sends a first request to the seventh network element in the fourth network; correspondingly, the seventh network element receives the first request from the fourth network element.

[0364] The seventh network element can be an NF in the fourth network. For example, the seventh network element can be an SMF or SF in the fourth network.

[0365] The first request is used to request the acquisition of service information of the terminal device in the fourth network. For example, if the seventh network element is an SMF in the fourth network, the first request can be used to request the acquisition of the session service context of the terminal device in the fourth network. As another example, if the seventh network element is an SF in the fourth network, the first request can be used to request the acquisition of the awareness service context of the terminal device in the fourth network.

[0366] The first request may have other names, such as subnet switch notification message, subnet switch request message, or context retrieval message, without restriction.

[0367] Step I2: The seventh network element sends a first response to the fourth network element; correspondingly, the fourth network element receives the first response from the seventh network element.

[0368] The first response includes the terminal device's service information in the fourth network. The specific content of the terminal device's service information in the fourth network can be found in the description of "terminal device's service information in the fourth network" in step I1, and will not be repeated here.

[0369] The first response may have other names, such as subnet switch notification response message, subnet switch response message, or context retrieval response message, without restriction.

[0370] It should be understood that the fourth network may include multiple NFs; the fourth network element interacts with some or all of the multiple NFs through steps I1 to I2 to obtain the service information of the terminal device in the fourth network. Optionally, in step H1, the first service information may be carried in the handover request or in other messages, without limitation.

[0371] Step H2: The first network element sends the first service information to the second network element (e.g., L-AMF#2); correspondingly, the second network element receives the first service information from the first network element.

[0372] Optionally, before sending the first service information to the second network element, the first network element may select the second network element. For example, the first network element may select the second network element based on the current location of the terminal device, and the service area of ​​the second network element may include the current location of the terminal device. There are several ways for the first network element to determine the current location of the terminal device. For example, a fourth network element sends a handover request #1 to the first network element, which may indicate the current location of the terminal device; the first network element can determine the current location of the terminal device based on the handover message #1. Another example is that a first access network element sends a first handover request to the first network element, which requests a handover from the source cell to the target cell; the first handover request may indicate the current location of the terminal device; the first network element can determine the current location of the terminal device based on the first handover request. Yet another example is that the first network element may request the current location of the terminal device from the first access network element.

[0373] The first service information can be carried in the context transmission message, or the UE context transmission message, or it can be carried in other messages without restriction.

[0374] Optionally, after step H2, the method shown in Figure 3 further includes step H3:

[0375] Step H3: The second network element in the third network sends the second service information to the eighth network element in the third network; correspondingly, the eighth network element receives the second service information from the second network element.

[0376] The eighth network element can be an NF in the third network. For example, the eighth network element can be an SMF or SF in the third network.

[0377] The second type of service information may include the service information of the terminal device in the fourth network. The specific content of the service information of the terminal device in the fourth network can be found in the description above, and will not be repeated here.

[0378] The first service information and the second service information may be the same or different. In some examples, after receiving the first service information, the second network element may forward or transparently transmit the first service information to the eighth network element. In this case, the first service information and the second service information are the same. In other examples, after receiving the first service information, the second network element may process the first service information, for example, by splitting and / or encapsulating it, to obtain the second service information, and then send the second service information to the eighth network element. For example, the first service information includes: the session context of the terminal device in the fourth network, and the perceived service context of the terminal device in the fourth network. The second network element may obtain service information #1 and service information #2 based on the first service information. Service information #1 includes: the session context of the terminal device in the fourth network, and service information #2 includes: the perceived service context of the terminal device in the fourth network. The second network element may send service information #1 to the SMF in the third network and service information #2 to the SF in the third network.

[0379] Optionally, after receiving the second service information, the eighth network element can provide services to the terminal device based on the service information of the terminal device in the fourth network. For example, if the eighth network element is an SMF in the third network, and the second service information includes the session context of the terminal device in the fourth network, then the eighth network element can provide session services to the terminal device based on the session context of the terminal device in the fourth network. As another example, if the eighth network element is an SF in the third network, and the second service information includes the perception service context of the terminal device in the fourth network, then the eighth network element can provide perception services to the terminal device based on the perception service context of the terminal device in the fourth network.

[0380] It should be understood that the third network may include at least one NF; the first network element interacts with some or all of the at least one NF through steps H2 to H3, thereby sending the terminal device's service information in the fourth network to some or all of the at least one NF.

[0381] In this way, if a terminal device switches, for example, from the fourth network to the third network, the first network element can obtain the terminal device's service information in the fourth network, and thus provide services to the terminal device based on the terminal device's service information in the fourth network, ensuring service continuity.

[0382] Figure 4 is a flowchart illustrating the second communication method provided in this application embodiment. This method can be applied to the scenarios shown in Figure 2B or Figure 2C. In this method, the first network element can notify the terminal device to establish a connection with the second network through a second network element that is connected to the terminal device. As shown in Figure 4, the method may include:

[0383] S401: The first network element obtains the connection status of the terminal device in the second network and / or the third network.

[0384] S402: The first network element receives the second message, which includes information about the terminal device and information about the second network.

[0385] In some possible implementations, the fifth network element may send a second message to the first network element; correspondingly, the first network element receives the second message from the fifth network element, as shown in S402a. The fifth network element can be used to manage user data and / or status. For example, the fifth network element is a C-UDM or PCF in the first network. For instance, when the C-UDM determines that it needs to send data to the terminal device through the second network, the C-UDM may send a second message to the first network element. Also, for example, when the PCF needs to update the terminal device's policy in the second network (e.g., the terminal device's AM policy and / or UE policy in the second network), the PCF may send a second message to the first network element. Optionally, in this implementation, the second message may be a downlink service message. The first network is, for example, a central network, and the second network is, for example, a sub-network; thus, a network element in the central network may trigger the second message.

[0386] In other possible approaches, a third network element (e.g., L-AMF#1) may send a second message to a first network element; correspondingly, the first network element receives the second message from the third network element, as shown in S402b. Optionally, in this approach, the second message may be a downlink service message or other messages, without limitation. The second network may be, for example, a subnetwork, in which network elements within the subnetwork may trigger the second message.

[0387] S403: When the first network and the terminal device have been updated to a disconnected state, and the second network and the terminal device are in a disconnected state, the first network element determines the third network that is in a connected state with the terminal device based on the second message.

[0388] S404: The first network element sends a third message to the second network element (e.g., L-AMF#2) in the third network; correspondingly, the second network element receives the third message from the first network element.

[0389] For details on S401 to S404, please refer to S305 to S308, which will not be repeated here.

[0390] Using the method shown in Figure 4, when the second network needs to establish a connection with the terminal device, the first network element can notify the terminal device to establish a connection with the second network through the second network element, which is already connected to the terminal device. In this way, the first network element does not need to broadcast a message to notify the terminal device to establish a connection with the second network within its corresponding TAL range, thereby reducing signaling overhead.

[0391] Furthermore, in this method, the first network element can be used to manage the connection status of terminal devices in multiple networks. For example, the first network element can be a network element in the central network that implements access and mobility management functions. The second network element is used to manage the mobility of terminal devices in the third network. For example, the second network element can be a network element in a sub-network that implements access and mobility management functions, thereby splitting access and mobility management functions to achieve distributed mobility management. In this way, signaling between the terminal device and network functions in the third network can be forwarded through the second network element, without having to go through the first network element. If the first network element fails, the terminal device can interact with network functions in the third network through the second network element, thereby ensuring service continuity and avoiding or reducing the impact of the first network element on services.

[0392] Furthermore, in this method, the second network element in the third network is used to manage the mobility of terminal devices within the third network. Thus, signaling between the terminal device and network functions in the third network can be forwarded through the second network element, bypassing the first network element. Since the second network element is located in the third network, the transmission latency of signaling forwarded through the second network element is generally less than that forwarded through the first network element, thereby reducing signaling transmission latency. Moreover, the forwarding of signaling between the terminal device and network functions in the third network through the second network element allows signaling to be transmitted within the third network, thereby improving service security and meeting the requirement of closed-loop service within the sub-network.

[0393] Furthermore, in this method, the first network element can know the connection status of the terminal device in the second network and / or the third network. For example, the first network element can know the connection status of the terminal device in the sub-network, so that the terminal device can be effectively managed according to the connection status, which is beneficial to improving communication performance.

[0394] In some possible embodiments, the method shown in Figure 4 further includes step F1 of the method shown in Figure 3. Optionally, after step F1, the method shown in Figure 4 further includes step F2 of the method shown in Figure 3. The specific contents of steps F1 to F2 can be found in the description of steps F1 to F2 in the method shown in Figure 3, and will not be repeated here.

[0395] In some possible embodiments, the method shown in Figure 4 further includes step G1 of the method shown in Figure 3. Optionally, after step G1, the method shown in Figure 4 further includes step G2 of the method shown in Figure 3. The specific contents of steps G1 to G2 can be found in the description of steps G1 to G2 in the method shown in Figure 3, and will not be repeated here.

[0396] In some possible embodiments, the method shown in Figure 4 further includes steps H1 to H2 of the method shown in Figure 3. Optionally, after step H2, the method shown in Figure 4 further includes step H3 of the method shown in Figure 3. The specific contents of steps H1 to H3 can be found in the description of steps H1 to H3 in the method shown in Figure 3, and will not be repeated here.

[0397] Figure 5 is a flowchart illustrating the third communication method provided in this application embodiment. This method can be applied to the scenario shown in Figure 2C. In this method, when a terminal device switches, the first access network element can send a first switching request to the first network element according to the reporting rules. As shown in Figure 5, the method may include:

[0398] S501: When a terminal device undergoes a handover, the first access network element sends a first handover request to the first network element (e.g., C-AMF) according to the reporting rules; correspondingly, the first network element receives the first handover request from the first access network element, and the first handover request is sent according to the reporting rules.

[0399] The first handover request includes information related to the handover of the terminal device. The reporting rules are as follows: 1. When a handover occurs in the access cell of the terminal device, the handover-related information is reported to the first network element, including the cell identifier of the target cell; 2. When a handover occurs in the access network element of the terminal device, the handover-related information is reported to the first network element, including the identifier of the target access network element; 3. When a handover occurs in the access network element of the terminal device and the TA (Transmission Address) of the terminal device changes, the handover-related information is reported to the first network element, including the TAC (Transmission Address) or TAI (Transmission Address) corresponding to the target access network element; or, 4. When a handover occurs in the access network element of the terminal device and the TAL (Transmission Address) of the terminal device changes, the handover-related information is reported to the first network element, including the TAL (Transmission Address) corresponding to the target access network element.

[0400] For details of S501, please refer to step F1 in the method shown in Figure 3, which will not be repeated here.

[0401] Using the method shown in Figure 5, the first access network element can send a first handover request to the first network element according to the reporting rules. If the conditions in the reporting rules are not met, the first access network element may not send a first handover request to the first network element, thereby reducing the signaling overhead between the first access network element and the first network element. For example, if the reporting rules include: reporting handover-related information to the first network element when the terminal device performs an access network element handover, then when the terminal device performs a handover between different cells corresponding to the first access network element, the first access network element may not send a first handover request to the first network element.

[0402] Optionally, the method shown in Figure 5 further includes S502:

[0403] S502: The first network element records the handover information related to the terminal device into the first UE context.

[0404] For details of S502, please refer to step F2 in the method shown in Figure 3, which will not be repeated here.

[0405] In some possible embodiments, the method shown in Figure 5 further includes step G1 of the method shown in Figure 3. Optionally, after step G1, the method shown in Figure 5 further includes step G2 of the method shown in Figure 3. The specific contents of steps G1 to G2 can be found in the description of steps G1 to G2 in the method shown in Figure 3, and will not be repeated here.

[0406] In some possible embodiments, the method shown in Figure 5 further includes steps H1 to H2 of the method shown in Figure 3. Optionally, after step H2, the method shown in Figure 5 further includes step H3 of the method shown in Figure 3. The specific contents of steps H1 to H3 can be found in the description of steps H1 to H3 in the method shown in Figure 3, and will not be repeated here.

[0407] The methods shown in Figures 3 to 5 will be described exemplarily below with reference to Figures 6 to 9.

[0408] In the method shown in Figure 6, the first network is taken as the central network, the first network element is C-AMF, the first access network element is access network element #1, and the terminal device is UE. This method illustrates an example of establishing a connection between the UE and the central network.

[0409] In the method shown in Figure 7, taking the first network as the central network, the first network element as C-AMF, the first access network element as access network element #1, and the terminal device as UE as an example, this method illustrates a possible example of how C-AMF obtains the connection status of the UE in the sub-network during the process of establishing a connection between the UE and sub-network #1. In this method, the sub-network can be sub-network #1, and L-AMF can be L-AMF#1 in sub-network #1; or, the sub-network can be sub-network #2, and L-AMF can be L-AMF#2 in sub-network #2; or, the sub-network can be sub-network #3, and L-AMF can be L-AMF#3 in sub-network #3.

[0410] In the method shown in Figure 8, the first network is the central network, the fourth network (also called the source network) is sub-network #3, the third network is sub-network #2 (also called the target network), the first network element is C-AMF, the fourth network element in the fourth network is L-AMF#3 (also called the source L-AMF or the old L-AMF), the seventh network element in the fourth network is L-NF#1 (also called the source L-NF or the old L-NF), the second network element in the third network is L-AMF#2 (also called the target L-AMF or the new L-AMF), the eighth network element in the third network is L-NF#2 (also called the target L-NF or the new L-NF), the first access network element is access network element #1, and the terminal device is UE as an example. This method illustrates a possible example of how C-AMF obtains the connection status of the UE in the sub-network during the UE handover process.

[0411] In the method shown in Figure 9, the first network is the central network, the second network is sub-network #1, the third network is sub-network #2, the first network element is C-AMF, the fifth network element is C-UDM, the third network element in the second network is L-AMF#1, the second network element in the third network is L-AMF#2, the first access network element is access network element #1, and the terminal device is UE. This method illustrates a possible example of C-AMF notifying the UE to connect to sub-network #1 based on the UE's connection status in the sub-network.

[0412] Figure 6 is a flowchart illustrating the fourth communication method provided in this application embodiment. As shown in Figure 6, the method may include:

[0413] S601: The UE sends a service request; correspondingly, the C-AMF receives the UE's service request.

[0414] This service request can be used to request that the UE access the central network.

[0415] For details of S601, please refer to S301 in the method shown in Figure 3, which will not be repeated here.

[0416] S602: The C-AMF can authenticate the UE and determine whether to allow the UE to access the central network. If the C-AMF determines that the UE is allowed to access the central network, then S603 is executed.

[0417] S603: C-AMF establishes a connection with UE.

[0418] For details of S603, please refer to S302 in the method shown in Figure 3, which will not be repeated here.

[0419] Optionally, after the C-AMF establishes a connection with the UE, the UE is in a connected state in the central network, and the C-AMF and the UE can exchange information, such as transmitting signaling and / or data between the C-AMF and the UE.

[0420] Optionally, after the C-AMF establishes a connection with the UE, the central network and the UE can be updated to a disconnected state (e.g., idle state). For example, if the time during which the central network and the UE do not exchange information exceeds a time threshold, the central network and the UE can be updated to a disconnected state (e.g., idle state). The method of obtaining this time threshold is not limited; for example, it can be specified by the protocol.

[0421] S604: C-AMF can create the first UE context for a UE.

[0422] For details on S604, please refer to the explanation of "the first network element can create the first UE context of the terminal device" in S302, which will not be repeated here.

[0423] S604 is an optional step.

[0424] Using the method shown in Figure 6, the UE can establish a connection with the central network, so that the C-AMF in the central network can provide services to the UE.

[0425] Figure 7 is a flowchart illustrating the fifth communication method provided in this application embodiment. As shown in Figure 7, the method may include:

[0426] S701: The UE sends a service request #a1 to the access network element #1; correspondingly, the access network element #1 receives the service request #a1 from the UE.

[0427] The service request #a1 is used to request that the UE be connected to the sub-network.

[0428] For details of S701, please refer to step A1 in the method shown in Figure 3, except that service request #1 is replaced with service request #a1 and the second network is replaced with the sub-network. Further details will not be provided.

[0429] S702: Access network element #1 sends service request #a2 to C-AMF; correspondingly, C-AMF receives service request #a2 from access network element #1.

[0430] The service request #a2 is used to request that the UE be connected to the sub-network.

[0431] For details of S702, please refer to step A2 in the method shown in Figure 3, except that service request #2 is replaced with service request #a2 and the second network is replaced with the sub-network. Further details will not be provided here.

[0432] Optionally, prior to S702, the UE can establish a connection with the C-AMF, and the UE and C-AMF can be in a connected state. For example, the UE can establish a connection with the C-AMF using the method shown in Figure 6.

[0433] S703: The C-AMF can authenticate the UE and determine whether to allow the UE to access the subnetwork. If the C-AMF determines that the UE is allowed to access the subnetwork, then S704 is executed.

[0434] S704: C-AMF sends service request #a3 to L-AMF; correspondingly, L-AMF receives service request #a3 from C-AMF.

[0435] The service request #a3 is used to request that the UE be connected to the sub-network.

[0436] For details of S704, please refer to step A3 in the method shown in Figure 3, except that service request #3 is replaced with service request #a3 and the second network is replaced with the sub-network. Further details will not be provided.

[0437] S705: The L-AMF establishes a connection with access network element #1, thereby providing sub-network services to the UE.

[0438] For details of S705, please refer to step A4 in the method shown in Figure 3, except that the second network is replaced by a sub-network, which will not be repeated here.

[0439] S706: L-AMF can create (or establish) a fourth UE context for the UE.

[0440] The fourth UE context is the UE context managed (or maintained) by the L-AMF. For example, the fourth UE context includes at least one of the following: the UE's identifier, the connection information of access network element #1, or the UE's location information. The connection information of access network element #1 includes, for example, at least one of the following: the ID of access network element #1, the cell ID of access network element #1, or the port number of access network element #1. The cell ID of access network element #1 may include the ID of the cell where the UE resides.

[0441] Optionally, L-AMF can perform UE mobility management at the cell level. As shown above, the fourth UE context managed by L-AMF includes the ID of the cell where the UE resides and / or the ID of the access network element to which the UE is connected. Thus, when an access network element initiates a cell handover to L-AMF, L-AMF can establish a new connection with the target cell and update the ID of the cell where the UE resides in the fourth UE context, thereby achieving UE mobility management at the cell level. When an access network element initiates an access network element handover to L-AMF, L-AMF can establish a new connection with the target cell in the target access network element and update the ID of the cell where the UE resides and / or the ID of the access network element to which the UE is connected in the fourth UE context, thereby achieving UE mobility management at the cell level.

[0442] The order of S705 and S706 is not limited. For example, S705 can be before or after S706. Or, for example, S706 can be during the process of establishing a connection between the L-AMF and access network element #1.

[0443] S707: L-AMF can send fifth message #1 to C-AMF; correspondingly, C-AMF receives fifth message #1 from L-AMF2.

[0444] The fifth message #1 is used to indicate that the UE is in a connected state in the sub-network.

[0445] For details of S707, please refer to the description of "the second network element in the third network (e.g., L-AMF#2) can send the fifth message to the first network element" in method b1 of the method shown in Figure 3. The only difference is that the second network element is replaced with L-AMF, the fifth message is replaced with the fifth message #1, and the third network is replaced with the sub-network. It will not be described again.

[0446] S708: Access network element #1 sends fifth message #2 to C-AMF; correspondingly, C-AMF receives fifth message #2 from access network element #1.

[0447] Among them, the fifth message #2 is used to indicate that the UE is in a connected state in the sub-network.

[0448] For details of S708, please refer to the description of "the first access network element can send the fifth message to the first network element" in mode b1 of the method shown in Figure 3, except that the fifth message is replaced with the fifth message #2 and the third network is replaced with the sub-network, which will not be repeated here.

[0449] S708 can come after S705, and the order of S708 with any of the steps in S706 to S707 is not limited.

[0450] The method shown in Figure 7 may include at least one step in S707 or S708.

[0451] S709: C-AMF updates or creates the first UE context for the UE.

[0452] For details on S709, please refer to the explanation of "the first network element can update or create the first UE context of the terminal device according to the fifth message" in method b1 of the method shown in Figure 3, which will not be repeated here.

[0453] S710: C-AMF sends the sixth message to access network element #1; correspondingly, access network element #1 receives the sixth message from C-AMF.

[0454] The sixth message is used to configure (or instruct) the reporting rules. For details on the reporting rules, please refer to step F1 of the method shown in Figure 3, which will not be repeated here.

[0455] For details of S710, please refer to the description of method c1 in Figure 3. Repeated parts will not be repeated.

[0456] Optionally, access network element #1 can create or update the fifth UE context of the UE. For example, after receiving the sixth message, access network element #1 can create or update the fifth UE context of the UE. Exemplarily, the fifth UE context may include at least one of the following: information about at least one network to which the UE is connected; information about the network element used to manage the mobility of the UE in each of the at least one network; indication information of the connection status of the UE in each of the at least one network; TAI or TAC corresponding to access network element #1; TAL corresponding to access network element #1; and reporting rules.

[0457] The UE may connect to at least one network, including a central network and / or a sub-network (e.g., sub-network #2). Exemplarily, the information of the at least one network may include at least one of the following: the ID of the central network, and the ID of sub-network #2.

[0458] In each of the at least one network, the information of the network element used to manage the mobility of the UE may include: C-AMF information and / or L-AMF information. For example, the C-AMF information is the C-AMF ID or address; the L-AMF information is, for example, the L-AMF ID or address.

[0459] S711: Access network element #1 sends NAS messages received from C-AMF and / or L-AMF to the UE.

[0460] For example, the NAS message may be a NAS message received by access network element #1 from L-AMF during the connection establishment process between L-AMF and access network element #1.

[0461] S711 can come after S705. The order of S711 with any of the steps from S706 to S710 is not limited.

[0462] S712: C-AMF sends UE status information #1 to C-UDM.

[0463] The status information #1 may indicate the connection status of the UE with at least one sub-network. The at least one sub-network may be sub-network #2; or, the at least one sub-network may include all sub-networks currently connected to the UE. For example, status information #1 may include indication information for each of the at least one sub-networks, and indication information for the connection status of the terminal device in each sub-network. For instance, if status information #1 includes: the ID of sub-network #1 and indication information for an idle state; and the ID of sub-network #2 and indication information for a connected state, then status information #1 may indicate that the UE's connection status in sub-network #1 is idle, and the UE's connection status in sub-network #2 is connected.

[0464] Optionally, status information #1 may also indicate the connection status between the UE and the central network. For example, if the field in status information #1 corresponding to the central network includes connection status indication information, then status information #1 may indicate that the UE's connection status in the central network #1 is connected.

[0465] Status information #1 can be carried in a traditional message or in a new message, without restriction. Status information #1 can also have other names, such as connection status information, without restriction.

[0466] S712 may follow S707 or S708. The order of S712 with any of the steps S709 to S711 is not limited.

[0467] S713: L-AMF sends UE status information #2 to C-UDM.

[0468] Specifically, status information #2 can indicate the connection status or availability status of the UE with subnetwork #2. For example, status information #2 may include indication information of subnetwork #2, and indication information of the connection status or availability status of the terminal device within subnetwork #2. For instance, if status information #2 includes the ID of subnetwork #2, and indication information of connection status or availability status (i.e., available), then status information #2 can indicate that the UE's connection status in subnetwork #2 is connected or available.

[0469] Status information #2 can be carried in a traditional message or in a new message, without restriction. Status information #2 can also have other names, such as connection status information, without restriction.

[0470] S713 may follow S705. Alternatively, S713 may follow S706. The order of S713 with any of the steps S707 through S712 is not limited.

[0471] Steps S706 to S713 are optional.

[0472] The effect of the method shown in Figure 7 can be referred to the methods shown in Figures 3 to 5, and will not be repeated here.

[0473] Figure 8 is a flowchart illustrating the sixth communication method provided in this application embodiment. As shown in Figure 8, the method may include:

[0474] S801: The UE sends a measurement report to the access network element #1; correspondingly, the access network element #1 receives the measurement report from the UE.

[0475] For details of S801, please refer to step B1 in the method shown in Figure 3, which will not be repeated here.

[0476] S802: When a UE undergoes handover, access network element #1 sends a first handover request to C-AMF according to the reporting rules; correspondingly, C-AMF receives the first handover request from access network element #1, which is sent by access network element #1 according to the reporting rules when a UE undergoes handover.

[0477] S803: C-AMF records information related to UE handover in the first UE context. The first UE context is the UE context of the UE managed (or maintained) by C-AMF.

[0478] For details of S802 to S803, please refer to steps F1 to F2 in the method shown in Figure 3. Repeated steps will not be repeated.

[0479] Optionally, the first handover request may include information about the target access network element, such as the ID of the target access network element. After receiving the first handover request, the C-AMF may establish an N2 connection with the target access network element.

[0480] Optionally, prior to S803, the UE can establish a connection with the C-AMF, and the UE and C-AMF can be in a connected state. For example, the UE can establish a connection with the C-AMF using the method shown in Figure 6.

[0481] S804: Access network element #1 sends a second handover request to L-AMF #3 in sub-network #3; correspondingly, L-AMF #3 receives the second handover request from access network element #1.

[0482] The second handover request is used to request the UE to be handed over from the source cell to the target cell.

[0483] For details of S804, please refer to step B2 in the method shown in Figure 3. Repeated steps will not be repeated here.

[0484] Optionally, the second handover request may include information about the target access network element, such as the ID of the target access network element.

[0485] S805: L-AMF#3 records information related to the handover of terminal devices into the second UE context. The second UE context is the UE context of the UE managed (or maintained) by L-AMF#3.

[0486] For details of S805, please refer to step G2 in the method shown in Figure 3. Repeated steps will not be repeated here.

[0487] Optionally, upon receiving the second handover request, L-AMF#3 may trigger a handover procedure, such as triggering an Xn handover or an N2 handover, thereby ensuring service continuity for the UE in different networks (e.g., different sub-networks). This application does not limit the specific handover method; for example, it may employ the method specified in the protocol. The order of triggering the handover procedure and updating the second UE context is not limited.

[0488] S806: L-AMF#3 obtains the UE's service information in sub-network #3 from L-NF#1.

[0489] The method by which L-AMF#1 obtains the UE's service information in sub-network #3 from L-NF#1 can be referred to steps I1 to I2 in the method shown in Figure 3, and will not be repeated here.

[0490] S807: If there is no connection between L-AMF#3 and L-AMF#2 in sub-network #2, and L-AMF#2 is the LMF serving the UE after the handover, then L-AMF#3 can send a fifth message to C-AMF; accordingly, C-AMF receives the fifth message from L-AMF#3.

[0491] The fifth message is used to indicate that the UE is in a connected state in subnetwork #2.

[0492] For details of S807, please refer to the explanation in method b2 shown in Figure 3, which states that "when the terminal device switches from the fourth network to the third network, the fourth network element in the fourth network (e.g., L-AMF#3 in Figure 2C) can send a fifth message to the first network element". Repeated parts will not be repeated.

[0493] Optionally, the fifth message is also used to update the connection status between the terminal device and L-AMF#3. For details, please refer to the method b2 shown in Figure 3, which states that "the fifth message is also used to update the connection status between the terminal device and the fourth network element". Repeated parts will not be described again.

[0494] Optionally, the fifth message may include a second UE context, which is used to update the connection status between the UE and L-AMF#3.

[0495] Optionally, the fifth message may also include the UE's service information in subnetwork #3.

[0496] In some implementations, L-AMF#2 can be selected by C-AMF based on a handover request from L-AMF#3 and the UE's current area. For example, after receiving a handover request from L-AMF#3, C-AMF can obtain the UE's current area and select the L-AMF that can serve that area as L-AMF#2. The UE's current area can be indicated by the handover request from L-AMF#3, or it can be requested by C-AMF from L-AMF#3, or it can be requested by C-AMF from access network element #1.

[0497] Optionally, after selecting L-AMF#2, C-AMF may send the indication information of L-AMF#2 (e.g., the ID of L-AMF#2) to L-AMF#3. In this way, after receiving the indication information of L-AMF#2, L-AMF#3 may send a fifth message to C-AMF. Alternatively, after selecting L-AMF#2, if C-AMF determines that there is no connection between L-AMF#3 and L-AMF#2, C-AMF may request (or instruct) L-AMF#3 to send a fifth message to C-AMF.

[0498] S808: C-AMF sends service information (hereinafter referred to as first service information) to L-AMF#2; correspondingly, L-AMF#2 receives the first service information from C-AMF.

[0499] The first service information may include the UE's service information in subnetwork #3.

[0500] S809: L-AMF#2 sends the second service information to L-NF#2; correspondingly, L-NF#2 receives the second service information from L-AMF#2.

[0501] The second service information may include the UE's service information in subnetwork #3.

[0502] For details of S808 to S809, please refer to steps H2 to H3 in the method shown in Figure 3. Repeated steps will not be repeated.

[0503] Optionally, C-AMF can also send a second UE context to L-AMF#2, that is, send the UE context of the UE managed (or maintained) by L-AMF#3. L-AMF#2 can establish a connection between the target access network element and L-AMF#2 for the UE based on the second UE context.

[0504] The second UE context and the UE's service information in subnetwork #1 can be included in the same message or in different messages, without restriction.

[0505] The order of S805 and S806 is not limited.

[0506] Steps S802 to S803 and S805 to S809 are optional.

[0507] The effect of the method shown in Figure 8 can be referred to the methods shown in Figures 3 to 5, and will not be repeated here.

[0508] Figure 9 is a flowchart illustrating the seventh communication method provided in an embodiment of this application. As shown in Figure 9, the method may include:

[0509] S901: C-AMF receives information from the UE and information from sub-network #1.

[0510] For details of S901, please refer to S303 in the method shown in Figure 3. Repeated parts will not be repeated.

[0511] In some implementations, the C-UDM can send UE information and sub-network #1 information to the C-AMF; correspondingly, the C-AMF can receive UE information and sub-network #1 information from the C-UDM, as shown in S901a. For details, please refer to the explanation of "the fifth network element can send terminal device information and second network information to the first network element" in the method shown in Figure 3, which will not be repeated here.

[0512] In other implementations, L-AMF#1 in sub-network #1 can send UE information and sub-network #1 information to C-AMF; correspondingly, C-AMF can receive UE information and sub-network #1 information from L-AMF#1, as shown in S901b. For details, please refer to the explanation in Figure 3 regarding "the third network element can send terminal device information and second network information to the first network element," which will not be repeated here.

[0513] Optionally, after S901, the method shown in FIG9 may include at least one of branch one, branch two, or branch three.

[0514] Branch 1: If the UE is in a disconnected state (e.g., idle state) in both the central network and the sub-network, then the method shown in Figure 9 may include S902:

[0515] S902: The C-AMF sends a paging request #1 to the UE; correspondingly, the UE receives the paging request #1 from the C-AMF. The paging request #1 may instruct the UE to establish a connection with subnetwork #1.

[0516] C-AMF can broadcast paging request #1 within the range of the TAL corresponding to the UE.

[0517] Branch 2: If the UE is in a disconnected state (e.g., idle state) in the central network and in a connected state in at least one sub-network (e.g., sub-network #2), then the method shown in Figure 9 may include S903 to S906. Specifically, after the UE establishes a connection with the C-AMF using the method shown in Figure 6, if the time during which the central network and the UE do not exchange information exceeds a time threshold, the connection between the central network and the UE may be updated to a disconnected state (e.g., idle state). The UE may connect to at least one sub-network (e.g., sub-network #2) using the method shown in Figure 7, thus placing the UE in a connected state in at least one sub-network.

[0518] S903: C-AMF sends a third message to L-AMF#2 in sub-network #2; correspondingly, L-AMF#2 receives the third message from C-AMF.

[0519] The third message is used to request L-AMF#2 to notify the terminal device to establish a connection with sub-network #1. Specifically, sub-network #1 and the UE are in a connected state; in other words, the UE is in a connected state within sub-network #1; or, the UE and L-AMF#2 are in a connected state; or, the connection between the UE and L-AMF#2 is in a connected state.

[0520] For details on S903, please refer to S308 in the method shown in Figure 3, which will not be repeated here.

[0521] S904: L-AMF#2 sends message #1 to the UE; correspondingly, the UE receives message #1 from L-AMF#2.

[0522] Message #1 instructs the UE to establish a connection with subnetwork #1.

[0523] For details on S904, please refer to the description of "the second network element sends message #1 to the terminal device" in S308, which will not be repeated here.

[0524] S905: The UE sends a service request message #1 to L-AMF#1.

[0525] The service request message #1 is used to request the establishment of a connection (e.g., a service connection) between the UE and subnetwork #1. Then, L-AMF #1 can execute S705 to S706 to establish the connection between the UE and subnetwork #1.

[0526] Optionally, after receiving the service request message #1, the method shown in FIG9 may further include S707 and S709; or, the method shown in FIG9 may further include S708 and S709.

[0527] S906: The UE sends feedback message #1 to L-AMF#2; correspondingly, L-AMF#2 receives feedback message #1 from the UE.

[0528] Feedback message #1 is used to provide feedback (or indicate) whether the connection between the UE and subnetwork #1 has been successfully established.

[0529] Branch 3: If the UE is in a connected state in the central network, the method shown in Figure 9 may include S907 to S909. Specifically, the UE can establish a connection with the C-AMF using the method shown in Figure 6, thus placing the UE in a connected state in the central network.

[0530] S907: C-AMF sends the first message to UE; correspondingly, UE receives the first message from C-AMF.

[0531] The first message instructs the UE to establish a connection with sub-network #1.

[0532] For details on S907, please refer to S304 in the method shown in Figure 3, which will not be repeated here.

[0533] S908: The UE sends a service request message #2 to L-AMF#1.

[0534] For details on S908, please refer to S905, except that service request message #1 is replaced with service request message #2, which will not be repeated here.

[0535] S909: The UE sends feedback message #2 to the C-AMF; correspondingly, the C-AMF receives feedback message #2 from the UE.

[0536] Feedback message #2 is used to provide feedback (or indicate) whether the connection between the UE and subnetwork #1 has been successfully established.

[0537] S902 to S909 are optional steps.

[0538] The effect of the method shown in Figure 9 can be referred to the methods shown in Figures 3 to 5, and will not be repeated here.

[0539] Based on the same technical concept as the above-described method embodiments, this application provides a corresponding communication device that can be used to perform the functions of the relevant steps in the above-described method embodiments. This function can be implemented in hardware, software, or by hardware executing corresponding software. The hardware or software includes one or more modules corresponding to the above functions. The communication device can be a core network element or an access network element, or it can be a device within a core network element or access network element (e.g., a module, communication module, circuit or chip responsible for communication functions (such as a modem chip, or a SoC chip or SIP chip containing a modem core), chip system, or processor), or it can be a logical node, logical module, or software capable of implementing all or part of the functions of a core network element or access network element.

[0540] In one possible implementation, the communication device provided in this application embodiment has the structure shown in FIG10, including a processing unit 1002. Optionally, the communication device further includes an interface unit 1001. The functions of each unit in the communication device 1000 are described below.

[0541] Interface unit 1001 is used for inputting and / or outputting information. Input information can be replaced by received information, and output information can be replaced by transmitted information. When outputting information, interface unit 1001 can output information to other devices outside of communication device 1000, or to other units within communication device 1000. In some embodiments, interface unit 1001 can be implemented using at least one of a physical interface, a communication module, a communication interface, and an input / output interface. In other embodiments, interface unit 1001 can be implemented using an interface circuit, such as a mobile communication module. The mobile communication module may include one or more of at least one antenna, at least one filter, a switch, a power amplifier, a low-noise amplifier (LNA), etc. Interface unit 1001 is used to perform the receiving and transmitting operations in the above method embodiments.

[0542] In this application, the interface unit 1001 may also have other names, such as a transceiver unit or a communication unit. Optionally, the interface unit 1001 may include a receiving unit and / or a sending unit, used for inputting information and outputting information, respectively. The receiving unit is used to perform the receiving operation in the above method embodiments. The sending unit is used to perform the sending operation in the above method embodiments.

[0543] The processing unit 1002 can be used to support the communication device 1000 in performing the processing actions in the above method embodiments. The processing unit 1002 can be implemented by one or more processors. For example, the processor can be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), microprocessors (MCUs), or other programmable logic devices, transistor logic devices, hardware components, or any combination thereof. A general-purpose processor can be a microprocessor or any conventional processor. The processing unit 1002 is used to perform processing-related operations in the above method embodiments, for example, to instruct operations other than receiving and sending operations in the above method embodiments.

[0544] In one embodiment, the communication device 1000 is applied to a first network element in the embodiment of this application shown in FIG3. The first network element is used to manage the connection status of terminal devices in multiple networks, including a first network and a second network, and the first network element is located in the first network. The specific functions of the processing unit 1002 in this embodiment will be described below.

[0545] The processing unit 1002 is configured to: receive a service request from a terminal device through the interface unit 1001 and establish a connection with the terminal device; receive information from the terminal device and information from the second network through the interface unit 1001; and send a first message to the terminal device through the interface unit 1001, wherein the first message is used to instruct the terminal device to establish a connection with the second network.

[0546] In some possible configurations, the multiple networks also include a third network. The processing unit 1002 is further configured to: obtain the connection status of the terminal device in the second network and / or the third network; receive a second message through the interface unit 1001, the second message including information about the terminal device and information about the second network; if the first network and the terminal device have been updated to a disconnected state, and the second network and the terminal device are also in a disconnected state, determine, based on the second message, a third network that is in a connected state with the terminal device, wherein a second network element exists in the third network, and the second network element is used to manage the mobility of the terminal device in the third network; and send a third message to the second network element through the interface unit 1001, the third message being used to request the second network element to notify the terminal device to establish a connection with the second network.

[0547] Optionally, the processing unit 1002 is specifically configured to: receive a fourth message from a third network element or a first access network element through the interface unit 1001, wherein the third network element is a network element in the second network used to manage the mobility of the terminal device in the second network, the first access network element is the serving first access network element of the terminal device, and the fourth message is used to indicate that the terminal device is in a disconnected state in the second network; wherein the fourth message is sent by the third network element or the first access network element under the following circumstances: the second network and the terminal device are updated to a disconnected state.

[0548] Optionally, the processing unit 1002 is specifically configured to: receive a fifth message through the interface unit 1001, the fifth message indicating that the terminal device is in a connected state in the third network. The fifth message is sent by the first access network element when the terminal device accesses the third network through the first access network element. Alternatively, the fifth message is sent by the second network element when the terminal device accesses the third network; or, if the multiple networks include a fourth network, the terminal device switches from the fourth network to the third network. Alternatively, the fifth message is sent by the fourth network element when the multiple networks include a fourth network, and the terminal device switches from the fourth network to the third network; wherein the fourth network element is a network element in the fourth network used to manage the mobility of the terminal device in the fourth network.

[0549] In some possible embodiments, the processing unit 1002 is further configured to: receive a first handover request from a first access network element via an interface unit 1001, the first handover request including information related to the handover of the terminal device; wherein the first handover request is sent by the first access network element according to a reporting rule when the terminal device undergoes a handover, the reporting rule being one of the following: when the access cell of the terminal device undergoes a handover, handover-related information is reported to the first network element, the handover-related information including the cell identifier of the target cell; when the access network element of the terminal device undergoes a handover, handover-related information is reported to the first network element, the handover-related information including the identifier of the target access network element; when the access network element of the terminal device undergoes a handover and the tracking area where the terminal device is located changes, handover-related information is reported to the first network element, the handover-related information including the tracking area identifier or tracking area code corresponding to the target access network element; or, when the access network element of the terminal device undergoes a handover and the tracking area list where the terminal device is located changes, handover-related information is reported to the first network element, the handover-related information including the tracking area list corresponding to the target access network element.

[0550] Optionally, the processing unit 1002 is further configured to: send a sixth message to the first access network element through the interface unit 1001, the sixth message being used to configure the reporting rules.

[0551] Optionally, the processing unit 1002 is further configured to: record information related to the handover of the terminal device into the first user equipment context, wherein the first user equipment context is the user equipment context of the terminal device managed by the first network element.

[0552] In some possible configurations, the processing unit 1002 is further configured to: receive service information from a fourth network element via the interface unit 1001 when the terminal device switches from a fourth network to a third network, wherein the fourth network element is a network element in the fourth network used to manage the mobility of the terminal device in the fourth network, and the service information is the service information of the terminal device in the fourth network; and send service information to a second network element via the interface unit 1001, wherein the second network element is a network element in the third network used to manage the mobility of the terminal device in the third network.

[0553] In another embodiment, the communication device 1000 is applied to the first network element in the embodiment of this application shown in FIG4. The first network element is used to manage the connection status of the terminal device in multiple networks, including a first network, a second network, and a third network, and the first network element is located in the first network. The specific functions of the processing unit 1002 in this embodiment will be described below.

[0554] Processing unit 1002 is configured to: acquire the connection status of the terminal device in a second network and / or a third network; receive a second message through interface unit 1001, the second message including information about the terminal device and information about the second network; if the first network and the terminal device have been updated to a disconnected state, and the second network and the terminal device are also in a disconnected state, determine, based on the second message, a third network that is in a connected state with the terminal device, wherein a second network element exists in the third network and is used to manage the mobility of the terminal device in the third network; and send a third message to the second network element through interface unit 1001, the third message being used to request the second network element to notify the terminal device to establish a connection with the second network.

[0555] Optionally, the processing unit 1002 is specifically configured to: receive a fourth message from a third network element or a first access network element through the interface unit 1001, wherein the third network element is a network element in the second network used to manage the mobility of the terminal device in the second network, the first access network element is the serving first access network element of the terminal device, and the fourth message is used to indicate that the terminal device is in a disconnected state in the second network; wherein the fourth message is sent by the third network element or the first access network element under the following circumstances: the second network and the terminal device are updated to a disconnected state.

[0556] Optionally, the processing unit 1002 is specifically configured to: receive a fifth message through the interface unit 1001, the fifth message indicating that the terminal device is in a connected state in the third network. The fifth message is sent by the first access network element when the terminal device accesses the third network through the first access network element. Alternatively, the fifth message is sent by the second network element when the terminal device accesses the third network; or, if the multiple networks include a fourth network, the terminal device switches from the fourth network to the third network. Alternatively, the fifth message is sent by the fourth network element when the multiple networks include a fourth network, and the terminal device switches from the fourth network to the third network; wherein the fourth network element is a network element in the fourth network used to manage the mobility of the terminal device in the fourth network.

[0557] In some possible embodiments, the processing unit 1002 is further configured to: receive a first handover request from a first access network element via an interface unit 1001, the first handover request including information related to the handover of the terminal device; wherein the first handover request is sent by the first access network element according to a reporting rule when the terminal device undergoes a handover, the reporting rule being one of the following: when the access cell of the terminal device undergoes a handover, handover-related information is reported to the first network element, the handover-related information including the cell identifier of the target cell; when the access network element of the terminal device undergoes a handover, handover-related information is reported to the first network element, the handover-related information including the identifier of the target access network element; when the access network element of the terminal device undergoes a handover and the tracking area where the terminal device is located changes, handover-related information is reported to the first network element, the handover-related information including the tracking area identifier or tracking area code corresponding to the target access network element; or, when the access network element of the terminal device undergoes a handover and the tracking area list where the terminal device is located changes, handover-related information is reported to the first network element, the handover-related information including the tracking area list corresponding to the target access network element.

[0558] Optionally, the processing unit 1002 is further configured to: send a sixth message to the first access network element through the interface unit 1001, the sixth message being used to configure the reporting rules.

[0559] Optionally, the processing unit 1002 is further configured to: record information related to the handover of the terminal device into the first user equipment context, wherein the first user equipment context is the user equipment context of the terminal device managed by the first network element.

[0560] In some possible configurations, the processing unit 1002 is further configured to: receive service information from a fourth network element via the interface unit 1001 when the terminal device switches from a fourth network to a third network, wherein the fourth network element is a network element in the fourth network used to manage the mobility of the terminal device in the fourth network, and the service information is the service information of the terminal device in the fourth network; and send service information to a second network element via the interface unit 1001, wherein the second network element is a network element in the third network used to manage the mobility of the terminal device in the third network.

[0561] In another embodiment, the communication device 1000 is applied to a third network element in the method shown in FIG3 or FIG4. The third network element is a network element in the second network and is used to manage the mobility of the terminal device in the second network. The specific functions of the processing unit 1002 in this embodiment will be described below.

[0562] The processing unit 1002 is configured to: receive downlink service messages through the interface unit 1001, the downlink service messages including information about the terminal device and information about the second network; when the second network and the terminal device are in a disconnected state, send the terminal device information and information about the second network to the first network element through the interface unit 1001, wherein the first network element is used to manage the connection status of the terminal device in multiple networks, the multiple networks including the first network and the second network, and the first network element is located in the first network.

[0563] Optionally, the processing unit 1002 is further configured to: when the connection status of the terminal device and the second network is updated to a disconnected state, report to the first network element through the interface unit 1001 that the terminal device is in a disconnected state in the second network.

[0564] In another embodiment, the communication device 1000 is applied to the first access network element in the method shown in FIG5. The specific functions of the processing unit 1002 in this embodiment will be described below.

[0565] Processing unit 1002 is configured to: when a handover occurs in the terminal device, send a first handover request to the first network element through interface unit 1001 according to reporting rules. The first handover request includes information related to the handover of the terminal device. The reporting rules include one of the following: when a handover occurs in the access cell of the terminal device, report handover-related information to the first network element, including the cell identifier of the target cell; when a handover occurs in the access network element of the terminal device, report handover-related information to the first network element, including the identifier of the target access network element; when a handover occurs in the access network element of the terminal device and the tracking area where the terminal device is located changes, report handover-related information to the first network element, including the tracking area identifier or tracking area code corresponding to the target access network element; or, when a handover occurs in the access network element of the terminal device and the tracking area list where the terminal device is located changes, report handover-related information to the first network element, including the tracking area list corresponding to the target access network element.

[0566] Optionally, the processing unit 1002 is further configured to: receive a sixth message from the first network element through the interface unit 1001, the sixth message being used to configure reporting rules.

[0567] Optionally, the processing unit 1002 is further configured to: when a terminal device undergoes a handover, send a second handover request to the fourth network element through the interface unit 1001. The second handover request is used to indicate information related to the handover of the terminal device. The fourth network element is located in the fourth network and is used to manage the mobility of the terminal device in the fourth network.

[0568] In one possible design, when the communication device 1000 is a communication equipment or a communication module within a communication equipment, the functionality of the processing unit 1002 can be implemented by one or more processors. For example, the processor may include a modem chip, or a system-on-a-chip (SoC) or SIP chip containing a modem core. The functionality of the interface unit 1001 can be implemented by transceiver circuitry.

[0569] In one possible design, when the communication device 1000 is a circuit or chip responsible for communication functions in a communication device, such as a modem chip or a system-on-a-chip (SoC) or SIP chip containing a modem core, the function of the processing unit 1002 can be implemented by a circuit system in the aforementioned chip that includes one or more processors or processor cores. The function of the interface unit 1001 can be implemented by the interface circuit or data transceiver circuit on the aforementioned chip.

[0570] The communication equipment can be an access network element or a core network element.

[0571] A more detailed description of the processing unit 1002 and the interface unit 1001 can be obtained directly from the relevant descriptions in the method embodiments shown in Figures 3 to 9, and will not be repeated here.

[0572] It should be noted that the module division in the above embodiments of this application is illustrative and only represents a logical functional division. In actual implementation, there may be other division methods. Furthermore, the functional units in the various embodiments of this application can be integrated into one processing unit, exist as separate physical units, or have two or more units integrated into one unit. The integrated units can be implemented in hardware, as software functional units, or in a combination of hardware and software. Whether a function is executed in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0573] For example, the functional unit in any of the above devices may be one or more integrated circuits configured to implement the above methods, such as one or more ASICs, one or more CPUs, one or more MCUs, one or more DSPs, or one or more FPGAs, or a combination of at least two of these integrated circuit forms.

[0574] If the integrated units described above are implemented as software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) or processor to execute all or part of the steps of the methods described in the various embodiments of this application. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0575] In one possible implementation, the communication device provided in this application embodiment is shown in FIG11. The communication device 1100 includes a processor 1102. Optionally, the communication device 1100 further includes an interface circuit 1101 and a memory 1103. Optionally, the communication device 1100 further includes an antenna (not shown in the figure). The interface circuit 1101, the processor 1102, and the memory 1103 are coupled to each other, and the interface circuit 1101 is connected to the antenna.

[0576] Optionally, the interface circuit 1101, processor 1102, and memory 1103 are coupled to each other via bus 1104. Bus 1104 can be a peripheral component interconnect (PCI) bus or an extended industry standard architecture (EISA) bus, etc. Buses can be divided into address buses, data buses, control buses, etc. For ease of illustration, only one thick line is used in Figure 11, but this does not mean that there is only one bus or one type of bus.

[0577] Interface circuit 1101 is used for inputting and / or outputting information. Input information can be replaced with received information, and output information can be replaced with transmitted information. When outputting information, interface circuit 1101 can output information to other devices outside of communication device 1100, or to other units within communication device 1100. Exemplarily, interface circuit 1101 can be implemented through at least one of a physical interface, a communication module, a communication interface, an input / output interface, and a mobile communication module. The mobile communication module may include one or more of at least one antenna, at least one filter, a switch, a power amplifier, an LNA, etc. Interface circuit 1101 is used to perform the receiving and transmitting operations in the above method embodiments.

[0578] Interface circuit 1101 may be one of the following: a transceiver, a transceiver circuit, a communication circuit, an interface, a communication interface, or an input / output interface (e.g., a chip's input / output interface). Interface circuit 1101 may include an input interface circuit and an output interface circuit, used for inputting information and outputting information, respectively. The input interface circuit is used to perform the receiving operation in the above method embodiments. The output interface circuit is used to perform the transmitting operation in the above method embodiments.

[0579] The transceiver can be used for communication with other communication devices. For example, if communication device 1100 is an access network element, the transceiver can be used to communicate with a core network element, another access network element, or a terminal device. Alternatively, if communication device 1100 is a core network element, the transceiver can be used to communicate with an access network element or another core network element.

[0580] Optionally, the transceiver may include a receiver and / or a transmitter. The receiver is used to perform the receiving operation in the above method embodiments. The transmitter is used to perform the sending operation in the above method embodiments.

[0581] Optionally, the transceiver can be integrated with the processor 1102 or exist independently and be coupled to the processor 1102 through the interface circuit of the communication device 1100. This application embodiment does not specifically limit this.

[0582] Processor 1102 can be used to support communication device 1100 in performing the processing actions in the above method embodiments. When communication device 1100 is used to implement the above method embodiments, processor 1102 can also be used to implement the functions of processing unit 1002. Processor 1102 can be a CPU, or other general-purpose processors, DSPs, ASICs, FPGAs, or other programmable logic devices, transistor logic devices, hardware components, or any combination thereof. General-purpose processors can be microprocessors or any conventional processor. Processor 1102 is used to perform processing-related operations in the above method embodiments, for example, to instruct operations other than receiving and sending operations in the above method embodiments.

[0583] In one embodiment, the communication device 1100 is applied to a first network element in the embodiment of this application shown in FIG3. The first network element is used to manage the connection status of the terminal device in multiple networks, including a first network and a second network, and the first network element is located in the first network. The specific functions of the processor 1102 in this embodiment are described below.

[0584] The processor 1102 is configured to: receive service requests from the terminal device via the interface circuit 1101 and establish a connection with the terminal device; receive information from the terminal device and information from the second network via the interface circuit 1101; and send a first message to the terminal device via the interface circuit 1101, the first message being used to instruct the terminal device to establish a connection with the second network.

[0585] In another embodiment, the communication device 1100 is applied to the first network element in the embodiment of this application shown in FIG4. The first network element is used to manage the connection status of the terminal device in multiple networks, including a first network, a second network, and a third network, and the first network element is located in the first network. The specific functions of the processor 1102 in this embodiment are described below.

[0586] The processor 1102 is configured to: acquire the connection status of the terminal device in a second network and / or a third network; receive a second message through the interface circuit 1101, the second message including information about the terminal device and information about the second network; if the first network and the terminal device have been updated to a disconnected state, and the second network and the terminal device are also in a disconnected state, determine, based on the second message, a third network that is in a connected state with the terminal device, wherein a second network element exists in the third network and is used to manage the mobility of the terminal device in the third network; and send a third message to the second network element through the interface circuit 1101, the third message being used to request the second network element to notify the terminal device to establish a connection with the second network.

[0587] In another embodiment, the communication device 1100 is applied to a third network element in the method shown in FIG3 or FIG4. The third network element is a network element in the second network and is used to manage the mobility of the terminal device in the second network. The specific functions of the processor 1102 in this embodiment are described below.

[0588] The processor 1102 is configured to: receive downlink service messages via interface circuit 1101, the downlink service messages including information about the terminal device and information about the second network; and, when the second network and the terminal device are in a disconnected state, send the terminal device information and information about the second network to a first network element via interface circuit 1101, wherein the first network element is used to manage the connection status of the terminal device in multiple networks, the multiple networks including the first network and the second network, and the first network element is located in the first network.

[0589] In another embodiment, the communication device 1100 is applied to the first access network element in the method shown in FIG5. The specific functions of the processor 1102 in this embodiment are described below.

[0590] Processor 1102 is configured to: when a handover occurs in a terminal device, send a first handover request to a first network element via interface circuit 1101 according to reporting rules. The first handover request includes information related to the handover of the terminal device. The reporting rules include one of the following: when a handover occurs in the access cell of the terminal device, report handover-related information to the first network element, including the cell identifier of the target cell; when a handover occurs in the access network element of the terminal device, report handover-related information to the first network element, including the identifier of the target access network element; when a handover occurs in the access network element of the terminal device and the tracking area where the terminal device is located changes, report handover-related information to the first network element, including the tracking area identifier or tracking area code corresponding to the target access network element; or, when a handover occurs in the access network element of the terminal device and the tracking area list where the terminal device is located changes, report handover-related information to the first network element, including the tracking area list corresponding to the target access network element.

[0591] The specific functions of processor 1102 can be found in the description of the communication methods provided in the above embodiments and examples of this application, as well as the specific functional description of communication device 1000 in the embodiment of this application shown in FIG10, which will not be repeated here.

[0592] Memory 1103 is used to store program instructions and / or data. Specifically, program instructions may include program code, which includes computer operation instructions. Memory 1103 may include RAM and may also include non-volatile memory, such as at least one disk storage device. Processor 1102 executes the program instructions stored in memory 1103 and uses the data stored in memory 1103 to implement the above-mentioned functions, thereby realizing the communication method provided in the embodiments of this application. Memory 1103 may be integrated with processor 1102 or may be a memory outside the communication device.

[0593] It is understood that the memory 1103 in Figure 11 of this application can be volatile memory or non-volatile memory, or may include both volatile and non-volatile memory. The non-volatile memory can be ROM, programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), or flash memory. The volatile memory can be RAM, which is used as an external cache. By way of example, but not limitation, many forms of RAM are available, such as static random access memory (SRAM), dynamic random access memory (DRAM), synchronous dynamic random access memory (SDRAM), double data rate synchronous dynamic random access memory (DDR SDRAM), enhanced synchronous dynamic random access memory (ESDRAM), synchronous linked dynamic random access memory (SLDRAM), and direct rambus RAM (DR RAM). It should be noted that the memory of the systems and methods described herein is intended to include, but is not limited to, these and any other suitable types of memory.

[0594] Based on the above embodiments, this application also provides a computer program product including computer-executable instructions, which, when run, causes the methods provided in the above embodiments to be executed.

[0595] Based on the above embodiments, this application also provides a computer-readable storage medium storing a computer program, which, when executed by a computer, causes the computer to perform the methods provided in the above embodiments.

[0596] The storage medium can be any available medium that a computer can access. For example, but not limited to, a computer-readable medium can include RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage media or other magnetic storage devices, or any other medium that can be used to carry or store desired program code in the form of instructions or data structures and that can be accessed by a computer.

[0597] Based on the above embodiments, this application also provides a chip for reading a computer program stored in a memory and implementing the method provided in the above embodiments.

[0598] Based on the above embodiments, this application provides a chip system including a processor for supporting a computer device in implementing the functions involved in the devices in the above embodiments. In one possible design, the chip system further includes a memory for storing necessary programs and data of the computer device. The chip system may be composed of chips or may include chips and other discrete components.

[0599] In the various embodiments of this application, unless otherwise specified or in case of logical conflict, the terminology and / or descriptions of different embodiments are consistent and can be referenced by each other. The technical features of different embodiments can be combined to form new embodiments according to their inherent logical relationship.

[0600] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to this application. It should be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in one or more blocks of the flowchart illustrations and / or one or more blocks of the block diagrams.

[0601] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means that implement the functions specified in one or more flowcharts and / or one or more block diagrams.

[0602] These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer-implemented process, such that the instructions, which execute on the computer or other programmable apparatus, provide steps for implementing the functions specified in one or more flowcharts and / or one or more block diagrams.

[0603] In this application, the terms "system" and "network" are used interchangeably. "At least one item" refers to one or more items, and "more than one item" refers to two or more items. "And / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A alone, A and B simultaneously, or B alone, where A and B can be singular or plural. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or plural items. In the textual description of this application, the character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0604] It is understood that the various numerical designations used in the embodiments of this application are merely for descriptive convenience and are not intended to limit the scope of the embodiments of this application. The order of the process numbers described above does not imply the order of execution; the execution order of each process should be determined by its function and internal logic.

[0605] Obviously, those skilled in the art can make various modifications and variations to this application without departing from the scope of this application. Therefore, if such modifications and variations fall within the scope of the claims of this application and their equivalents, this application also intends to include such modifications and variations.

Claims

1. A communication method, characterized in that, Applied to a first network element, the first network element is used to manage the connection status of terminal devices in multiple networks, the multiple networks including a first network and a second network, the first element being located in the first network, the method includes: Receive the service request from the terminal device and establish a connection with the terminal device; Receive information from the terminal device and information from the second network; A first message is sent to the terminal device, the first message being used to instruct the terminal device to establish a connection with the second network.

2. The method as described in claim 1, characterized in that, The plurality of networks also includes a third network, and the method further includes: Obtain the connection status of the terminal device in the second network and / or the third network; Receive a second message, the second message including information about the terminal device and information about the second network; When the first network and the terminal device have been updated to a disconnected state, and the second network and the terminal device are also in a disconnected state, the third network that is in a connected state with the terminal device is determined according to the second message. The third network contains a second network element, which is used to manage the mobility of the terminal device in the third network. A third message is sent to the second network element, the third message being used to request the second network element to notify the terminal device to establish a connection with the second network.

3. The method as described in claim 2, characterized in that, Obtaining the connection status of the terminal device in the second network includes: Receive a fourth message from a third network element or a first access network element, wherein the third network element is a network element in the second network and is used to manage the mobility of the terminal device in the second network, the first access network element is the serving first access network element of the terminal device, and the fourth message is used to indicate that the terminal device is in a disconnected state in the second network; The fourth message is sent by the third network element or the first access network element under the following circumstances: the second network and the terminal device are updated to a non-connected state.

4. The method as described in claim 2, characterized in that, Obtaining the connection status of the terminal device in the third network includes: Receive a fifth message, the fifth message being used to indicate that the terminal device is in a connected state in the third network; The fifth message is sent by the first access network element under the following circumstances: the terminal device accesses the third network through the first access network element; or, The fifth message is sent by the second network element under at least one of the following circumstances: the terminal device accesses the third network; or, the plurality of networks further includes a fourth network, and the terminal device switches from the fourth network to the third network; or... The fifth message is sent by the fourth network element under the following circumstances: the plurality of networks further includes a fourth network, and the terminal device switches from the fourth network to the third network; wherein, the fourth network element is a network element in the fourth network, used to manage the mobility of the terminal device in the fourth network.

5. The method according to any one of claims 2 to 4, characterized in that, Upon receiving the second message from a fifth network element, where the fifth network element is a network element used to manage user data and / or status, the second message is further used to indicate that the connection status between the terminal device and the network in the plurality of networks is a connected state.

6. The method according to any one of claims 1 to 5, characterized in that, Also includes: Receive a first handover request from a first access network element, the first handover request including information related to the handover of the terminal device; The first handover request is sent by the first access network element when the terminal device undergoes a handover, according to a reporting rule, which is one of the following: When the access cell of the terminal device is switched, the handover-related information reported to the first network element includes the cell identifier of the target cell; When a handover occurs in the access network element of the terminal device, the handover-related information is reported to the first network element, including the identifier of the target access network element. When the access network element of the terminal device changes and the tracking area where the terminal device is located changes, the terminal device reports handover-related information to the first network element. This handover-related information includes the tracking area identifier or tracking area code corresponding to the target access network element; or When the access network element of the terminal device is switched and the tracking area list where the terminal device is located changes, the switching-related information is reported to the first network element. The switching-related information includes the tracking area list corresponding to the target access network element.

7. The method as described in claim 6, characterized in that, Also includes: Send a sixth message to the first access network element, the sixth message being used to configure the reporting rules; or... The reporting rules are pre-set.

8. The method as described in claim 6 or 7, characterized in that, Also includes: Information related to the handover of the terminal device is recorded in the first user equipment context, which is the user equipment context of the terminal device managed by the first network element.

9. The method according to any one of claims 1 to 8, characterized in that, Also includes: When the terminal device switches from the fourth network to the third network, it receives service information from the fourth network element. The fourth network element is a network element in the fourth network used to manage the mobility of the terminal device in the fourth network. The service information is the service information of the terminal device in the fourth network. The service information is sent to a second network element, which is a network element in the third network. The second network element is used to manage the mobility of the terminal device in the third network.

10. The method as described in claim 9, characterized in that, The business information may include at least one of the following: session context, or business context.

11. A communication method, characterized in that, Applied to a third network element, which is a network element in the second network, and used to manage the mobility of terminal devices in the second network, the method includes: Receive downlink service messages, the downlink service messages including information about the terminal device and information about the second network; When the second network and the terminal device are in a disconnected state, the terminal device's information and the second network's information are sent to the first network element. The first network element is used to manage the terminal device's connection status in multiple networks, including the first network and the second network, and the first network element is located in the first network.

12. The method as described in claim 11, characterized in that, Also includes: When the connection status between the terminal device and the second network is updated to a disconnected state, the terminal device reports to the first network element that the terminal device is in a disconnected state in the second network.

13. A communication device, characterized in that, Includes a unit for performing the method as described in any one of claims 1-12.

14. A communication device, characterized in that, Includes a processor for executing computer programs or instructions that cause the apparatus to perform the method as described in any one of claims 1-12.

15. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program or instructions, which, when executed, implement the method as described in any one of claims 1-12.

16. A computer program product, characterized in that, The computer program product includes: computer program code, wherein when the computer program code is run, the method as described in any one of claims 1-12 is implemented.

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