Communication method and communication apparatus

Abstract

Provided in the embodiments of the present application are a communication method and a communication apparatus, which can solve the problem of disordered connection states of a terminal when the terminal establishes connections with two networks respectively and the connection states of the terminal change. Taking the method applied to a first network function of a first network as an example, the method comprises: acquiring connection information between a terminal and a second network, wherein the connection information indicates whether the terminal is connected to the second network, and the first network and the second network serve the terminal; when the first network expects to establish a connection with the terminal, if the terminal is not connected to the second network, paging the terminal; and if the terminal is connected to the second network, establishing, with a first access network device, a connection corresponding to the terminal, and the terminal establishing a connection with the second network by means of the first access network device.

Description

Communication methods and communication devices

[0001] This application claims priority to Chinese Patent Application No. 202411607127.X, filed on November 11, 2024, entitled "Communication Method and Communication Device", the entire contents of which are incorporated herein by reference. Technical Field

[0002] This application relates to the field of communications, and more particularly to communication methods and communication devices. Background Technology

[0003] Currently, the distributed subnetwork concept has been proposed. The architecture of a distributed subnetwork includes two types of core networks (CNs): a main network and subnetworks. The main network is the central network deployed by the operator, possessing complete core network functions and providing comprehensive management services to terminals. Multiple subnetworks can exist, and a single terminal can access services from multiple subnetworks simultaneously. Network functions (NFs) within a subnetwork are configured on demand; network functions not configured in a subnetwork can be obtained from the main network. In other words, some network functions in the main network can be shared and used by subnetworks.

[0004] Terminals expect to establish connections with both the main network and subnets (e.g., non-access-stratum (NAS) connections). However, changes in the terminal's connection status can lead to inconsistencies in the terminal's connection state. Summary of the Invention

[0005] The communication method and communication device provided in this application can solve the problem of disordered connection status of the terminal when the terminal establishes connections with two networks respectively and the connection status of the terminal changes.

[0006] To achieve the above objectives, the embodiments of this application adopt the following technical solutions:

[0007] In a first aspect, a communication method is provided, which is applied to a first network side, such as a first network function of the first network, a device for implementing the first network function, or a logical node, logical module, or software capable of implementing all or part of the first network function. Taking the application of this method to a first network function as an example, the method includes: obtaining connection information between a terminal and a second network, the connection information indicating whether a connection exists between the terminal and the second network, and the first network and the second network serving the terminal; if the first network desires to establish a connection with the terminal, and if the terminal does not have a connection with the second network, then paging the terminal; if the terminal has a connection with the second network, then establishing a connection corresponding to the terminal with a first access network device, and the terminal establishing a connection with the second network through the first access network device.

[0008] In this embodiment, in the scenario of a first network and a second network serving a terminal, the first network function can obtain the connection information between the terminal and the second network. Therefore, when the first network expects to establish a connection with the terminal, the first network function first determines whether a paging terminal or a connection corresponding to the terminal is established with the first access network device based on whether a connection exists between the terminal and the second network. This allows the first and second networks to synchronize the terminal's connection status, resolving the problem of disordered terminal connection status. Disordered terminal connection status can occur, for example, when the terminal has established a connection with the second network and the first network expects to establish a connection with the terminal, but the first network is unaware that the terminal has established a connection with the second network through the first access network device. The first network will send paging messages to all access network devices under the trace area identity (TAI) registered by the terminal. If the terminal detects this paging message from an access network device other than the first access network device, the terminal may switch its serving access network device from the first access network device to another access network device, resulting in no connection between the terminal and the second network, i.e., disordered terminal connection status.

[0009] Furthermore, if the terminal is connected to the second network, the first network function establishes a connection corresponding to the terminal with the first access network device. Consequently, the first network will not page the terminal, avoiding the problem of the terminal not responding to paging from the first network when a connection is established between the terminal and the second network via the first access network device, thus preventing the first network from establishing a connection with the terminal. Issues such as the terminal not responding to paging from the first network include: since the terminal is connected to the second network via the first access network device, a connection has been established, and the terminal may no longer check for paging messages broadcast on the air interface; or, the terminal may not check for paging messages from access network devices other than the first access network device; or, assuming the terminal receives a paging message broadcast from the first access network device, the terminal may not be able to correctly decode the paging message from the first network; or, even if the terminal correctly decodes the paging message from the first network, the terminal may ignore the paging message or consider it erroneous.

[0010] It is understood that the first network and the second network can refer to networks located in different domains. For example, the first network and the second network can be different public land mobile networks (PLMNs). Another example is that the first network and the second network belong to different operators. Yet another example is that the first network and the second network are networks in different domains under the same operator. Furthermore, the first network and the second network may or may not share network functions; this is not limited.

[0011] It should be understood that "first network" and "second network" serving the terminal means either that the terminal registers with both the first and second networks, or that the terminal accesses both networks separately. Furthermore, "first network" and "second network" serving the terminal can mean that the first and second networks serve the terminal separately, or that both networks serve the terminal simultaneously; there is no limitation on this.

[0012] It can be understood that whether a terminal has a connection to the second network refers to whether the terminal is in a connected state on the second network. For example, if the terminal has no connection to the second network, it means the terminal is in an idle state on the second network. If the terminal is in an idle state on the second network, then it is in a connection management (CM) idle state on the second network. Alternatively, being in a CM idle state on the second network can also be understood as being in a radio resource control (RRC) idle state. As another example, if the terminal has a connection to the second network, it means the terminal is in a connected state on the second network, which is also a CM connected state on the second network. Furthermore, being in a CM idle state on the second network can also be understood as the terminal being in an RRC connected state.

[0013] Additionally, the scenario where the first network expects to establish a connection with the terminal can refer to a situation where the terminal is not connected to the first network (or the terminal is in an idle or disconnected state in the first network), and the first network has data and / or signaling to transmit to the terminal. The terminal not being connected to the first network includes situations where the terminal registers with both the first and second networks through a second access network device, but the terminal releases its RRC connection with the second access network device, and the terminal is in an RRC idle state.

[0014] It is understandable that, when the first network expects to establish a connection with the terminal, the first network function determines the paging terminal based on the fact that the terminal does not have a connection with the second network, and then executes the paging procedure. Conversely, when the first network expects to establish a connection with the terminal, the first network function determines to establish a connection with the terminal through the terminal's current serving access network device (i.e., the first access network device) based on the fact that the terminal has a connection with the first access network device; that is, the first network function establishes a connection corresponding to the terminal with the first access network device.

[0015] It should be understood that the above-mentioned situation where the first network expects to establish a connection with the terminal can also be understood as: the situation where the first network expects to page the terminal. In this case, the first network function determines to execute the paging process based on the fact that the terminal does not have a connection with the second network; the first network function determines to establish a connection corresponding to the terminal with the first access network device based on the fact that the terminal has a connection with the second network.

[0016] In addition, the first access network device and the second access network device mentioned above are only logically distinguished as the access network device before the terminal is in the idle state and the access network device after the terminal re-enters the RRC connection state. The two can be the same or different, which will not be elaborated here.

[0017] In one possible implementation, the connection information may include an identifier for identifying the terminal, and indication information indicating that the terminal is in a connected state.

[0018] Optionally, the first network function can obtain connection information from the first access network device. This connection information includes a first temporary identifier and indication information indicating that the terminal is in a connected state. The first temporary identifier is a temporary identifier assigned to the terminal by the second network. This first temporary identifier is associated with the terminal's context stored in the first network function, allowing the first network function to identify which terminal it is based on the first temporary identifier. Furthermore, since the first temporary identifier is assigned to the terminal by the second network, the first network function can determine that the terminal indicated by the connection information is in a connected state, which could mean that the terminal is in a connected state in the second network (or the terminal is in a CM connected state). Moreover, since the first network function obtains the connection information from the first access network device, the first network function determines that the terminal has established a connection with the second network through the first access network device (or the terminal is in an RRC connected state), meaning that the terminal's serving access network device is the first access network device.

[0019] Alternatively, the first network function may obtain connection information from a second network function of the second network. This connection information includes the terminal's subscription permanent identifier (SUPI) and indication information indicating that the terminal is in a connected state. Since the first and second network functions are typically located within a trusted domain, the second network function can send the terminal's SUPI and an identifier of the terminal to the first network function. Furthermore, the first network function can also obtain information about the terminal's serving access network device (i.e., the first access network device), such as the identifier of the first access network device, from the second network function or other network functions of the second network besides the second network function.

[0020] In one possible implementation, the method provided by the first aspect further includes: obtaining a first temporary identifier from a second access network device. The first temporary identifier is a temporary identifier assigned to the terminal by the second network when the terminal establishes a connection with the second network through the second access network device. The first temporary identifier is associated with the terminal's context stored in the first network function. The second access network device is the access network device that served the terminal before the terminal established a connection with the first access network device. It is understood that the first temporary identifier may be, for example, a globally unique temporary identifier (GUTI) assigned to the terminal by the second network when the terminal establishes a connection with the second network through the second access network device before the terminal establishes a connection with the second network through the first access network device, or a 5G-GUTI, and is not limited thereto. In addition, in order for the first network function to identify the terminal in the connection information obtained through the access network device, by reusing the first temporary identifier and associating the first temporary identifier with the terminal's context by the first network function, the first network function can identify that the connection information is for the terminal and determine that the connection information is associated with the second network based on the first temporary identifier, thereby facilitating deployment, while exposing the terminal's SUPI as little as possible. In other words, the first network function can obtain the first temporary identifier assigned to the terminal by the second network through the second access network device, and associate the temporary identifier with the terminal context stored in the first network function. Thus, the first network function can identify that the message is for the terminal and the second network based on the first temporary identifier included in the message, which is easy to deploy and reduces implementation complexity.

[0021] In one possible implementation, obtaining the first temporary identifier from the second access network device includes: obtaining the first temporary identifier from the second access network device when the terminal establishes a connection with the first network through the second access network device, or when the second access network device and the first network function update the terminal's context. That is, the first network function can obtain the first temporary identifier during the process of the terminal establishing a connection with the first network through the second access network device, or it can obtain the first temporary identifier after the terminal has established a connection with the first network through a context update process, thus improving the flexibility of the first network function in obtaining the first temporary identifier.

[0022] In one possible implementation, obtaining connection information between the terminal and the second network includes: obtaining connection information from a first access network device. This connection information includes a first temporary identifier and indication information indicating that the terminal is in a connected state. In other words, considering that the terminal has already established a connection with the first access network device, by having the first access network device send the first temporary identifier and the indication information indicating that the terminal is in a connected state to the first network function, the first access network device can determine that the terminal has transitioned from an idle state to a connected state, and that the terminal's current serving access network device is the first access network device. Consequently, the first network function will not page the terminal (e.g., send paging messages to all access devices in the terminal's registered TAI list). This solves the problem of connection state disorder caused by the terminal detecting paging messages from multiple access network devices, releasing its connection with the first access network device, and establishing connections with other access network devices.

[0023] In one possible implementation, the method provided by the first aspect further includes: obtaining a second temporary identifier from a first access network device. The second temporary identifier is a temporary identifier assigned to the terminal by the second network when the terminal establishes a connection with the second network through the first access network device. It can be understood that the second temporary identifier, relative to the first temporary identifier, is a new temporary identifier assigned to the terminal by the second network, for example, a GUTI newly assigned to the terminal by the second network when the terminal establishes a connection with the second network through the first access network device. It should be understood that the first temporary identifier and the second temporary identifier are only logically distinct; they can be the same or different, and this is not limited. That is, the first network function can also obtain the second temporary identifier newly assigned to the terminal by the second network, thereby ensuring that the first network function can continue to identify the connection information between the terminal and the second network, and realize the synchronization of the terminal's connection status between the first network and the second network.

[0024] In one possible implementation, the method provided by the first aspect further includes: obtaining first identification information or second identification information from a first access network device. The first identification information is identification information assigned by the first access network device to the terminal on a first interface, where the first interface is an interface for interaction between the first access network device and a first network function. The second identification information is identification information assigned on a second interface, where the second interface is an interface for interaction between the first access network device and a second network function of a second network. It can be understood that the first identification information is assigned by the first access network device and used to identify the terminal on the interface (i.e., the first interface) for interaction between the first access network device and the first network function. For example, assuming the first interface uses the Next Generation Application Protocol (NGAP), the first identification information could be RAN NGAP UE ID#1. Additionally, the second identification information could be, for example, an identification pair identifying the terminal on the interface (i.e., the second interface) for interaction between the first access network device and the second network function. Taking the second interface using NGAP as an example, the second identification information could be an NGAP UE pair ID, which includes RAN NGAP UE ID#2 and CN NGAP UE ID#2. In other words, after the first network function obtains the first identification information or the second identification information from the first access network device, it can use the first identification information or the second identification information to instruct the terminal in the message sent to the first access network device. As a result, the first access network device does not need to broadcast the terminal's paging message on the air interface, thereby avoiding the problem that the terminal may not respond to the paging of the subnet.

[0025] In one possible implementation, the first identification information is a transaction identifier, which is used to identify the terminal or to indicate data and / or signaling to be transmitted to the terminal. In other words, by sending the transaction identifier to the first access network device, the first access network device can be informed that the terminal has data or signaling to be transmitted, without needing to page the terminal over the air interface, thus improving indication efficiency.

[0026] In one possible implementation, obtaining connection information between the terminal and the second network includes: obtaining connection information from the second network function of the second network. The connection information includes the terminal's permanent identifier and indication information indicating that the terminal is in a connected state. That is, based on the connection information, the first network function determines that the terminal has established a connection with the second network. Therefore, the first network function will not page the terminal (e.g., send paging messages to all access devices registered in the terminal's TAI list). This solves the problem of the terminal releasing its connection with the first access network device and establishing connections with other access network devices after detecting paging messages from multiple access network devices, thus causing disorder in the terminal's connection state.

[0027] Optionally, the method provided in the first aspect further includes: obtaining the identifier of the terminal's serving access network device from the second network function, wherein the terminal's serving access network device is the first access network device. The identifier of the access network device may be, for example, a new radio (NR) cell global identifier (NCGI), or an identifier used to identify access network devices (e.g., gNBs) within the same domain (e.g., PLMN) (or gNB ID), or an identifier used to globally identify access network devices, or any other identification information that may be used by the core network side to identify access network devices; this is not limited. In other words, the first network function can also directly obtain the identifier of the first access network device from the second network function, thereby determining that the terminal's serving access network device is the first access network device, to improve the efficiency of obtaining the identifier of the terminal's serving access network device.

[0028] In one possible implementation, the method provided by the first aspect further includes: obtaining second identification information from a second network function. The second identification information is identification information used to identify the terminal on a second interface, whereby the second interface is the interface through which the first access network device interacts with the second network function. In other words, the second network function can reuse the second identification information used between the first access network device and the second network, so that the first access network device can determine that the message sent by the first network function is for the subnet. Consequently, the first access network device does not need to broadcast the terminal's paging message on the air interface, thus avoiding the problem that the terminal may not respond to the subnet's paging.

[0029] In one possible implementation, when the first network intends to establish a connection with the terminal, if the terminal is already connected to the second network, then establishing a connection with the first access network device includes: sending a first message to the first access network device. The first message includes first identification information or second identification information, which is used by the first access network device to determine that the first message is for the terminal. In other words, when the first network intends to establish a connection with the terminal, the first network function, by carrying the first identification information or second identification information in the first message, enables the first access network device to identify the terminal, thereby preventing the first access network device from paged the terminal over the air interface.

[0030] In one possible implementation, the first message instructs the first access network device to send first indication information to the terminal, wherein the first indication information instructs the terminal to initiate a connection establishment procedure with the first network; or, the first message includes first identification information, identification information assigned by the first network to the terminal on the first interface, and data and / or signaling to be transmitted to the terminal, wherein the first message instructs the first access network device to send the data and / or signaling to be transmitted to the terminal. It is understood that for the first message instructing the first access network device to send the first indication information to the terminal, the first message includes the first indication information. For the first message instructing the first access network device to send the data and / or signaling to be transmitted to the terminal, the first message may include the data and / or signaling. Additionally, the first indication information may be the terminal's paging indication information and / or temporary mobile subscriber identity (TMSI), which is determined based on a temporary identifier assigned to the terminal by the first network. In other words, the first message can be used to instruct the first access network device to send the first instruction information to instruct the terminal to initiate a connection establishment process with the first network, or it can be used to instruct the first access network device to send data and / or signaling to simplify the connection establishment process between the first network and the terminal, save signaling overhead, and improve efficiency.

[0031] It is understood that the first message includes first identification information (e.g., RAN NGAP UE ID#1) and identification information (e.g., CN NGAP UE ID#1) assigned by the first network to identify the terminal on the first interface. This is equivalent to the first access network device and the first network function establishing the terminal's context on the first interface in advance. In the subsequent connection establishment process between the first network and the terminal, it is not necessary to establish the terminal's context on the first interface again, saving signaling overhead and improving efficiency.

[0032] In one possible implementation, the method provided by the first aspect further includes: obtaining a third temporary identifier and a fourth temporary identifier, wherein the third temporary identifier is a temporary identifier assigned to the terminal by the first network when the terminal establishes a connection with the first network through the second access network device, and the fourth temporary identifier is a temporary identifier assigned to the terminal by the first network when the terminal establishes a connection with the first network through the first access network device; and sending the third temporary identifier and the fourth temporary identifier to the first access network device. It can be understood that the third temporary identifier and the fourth temporary identifier are similar, except that the third temporary identifier is assigned by the first network. Similarly, the fourth temporary identifier is similar to the third temporary identifier, except that the fourth temporary identifier is assigned by the network. That is, the first network function can send the third temporary identifier and the fourth temporary identifier to the second network function through the first access network device, so as to inform the second network function of the newly assigned temporary identifier on the first network side, thereby ensuring that the second network function can subsequently identify the connection information between the terminal and the first network, and realize the synchronization of the terminal's connection status between the first network and the second network.

[0033] In one possible implementation, the method provided by the first aspect further includes: sending indication information to the first access network device to instruct the first access network device to send a third temporary identifier and a fourth temporary identifier to a second network function of the second network. That is, the first network function can directly instruct the first access network device to send the third temporary identifier and the fourth temporary identifier to the second network function, ensuring that the first access network device can determine which network to send the third temporary identifier and the fourth temporary identifier to.

[0034] In one possible implementation, the method provided by the first aspect further includes: sending an identifier of a second network function of the second network to the first access network device. The identifier of the second network function is used for communication between the first access network device and the second network function. That is, the first network function can also send an identifier of the second network function to the first access network device, so that the first access network device can send a third temporary identifier and a fourth temporary identifier to the second network function based on the identifier of the second network function, ensuring that the first access network device can communicate with the second network function to send the third temporary identifier and the fourth temporary identifier to the second network function.

[0035] In one possible implementation, the method provided by the first aspect further includes updating the terminal's serving access network device from a second access network device to a first access network device. That is, after the first network obtains the connection information between the terminal and the second network, it can update the terminal's serving access network device from the second access network device to the first access network device to facilitate subsequent communication with the terminal through the first access network device. It is understood that the first network function can update the terminal's context. For example, if the first network function obtains a first temporary identifier and a second temporary identifier, it updates the first temporary identifier to the second temporary identifier. As another example, if the first network function obtains a third temporary identifier and a fourth temporary identifier, it updates the third temporary identifier to the fourth temporary identifier.

[0036] In one possible implementation, the method provided by the first aspect further includes: receiving second indication information, the second indication information being used to indicate that the context established for the terminal by the first network function should not be released. It is understood that the aforementioned second indication information indicating that the terminal's N2 context should not be released can be replaced by any of the following: the second indication information indicating that the terminal should not enter an idle state; or, the second indication information indicating that the connection of the terminal should not be disconnected. Furthermore, the terminal's N2 context is merely an exemplary name, and as the network evolves, the terminal's N2 context can be replaced by any other context that might be used to represent the terminal on the first interface. It should be understood that the idle state could, for example, refer to the CM idle state, or any other name that might indicate the connection state between the terminal and the network. It should also be understood that the second indication information indicating that the connection of the terminal should not be disconnected can, for example, mean maintaining a non-access-stratum (NAS) signaling connection between the terminal and the first network function, or not releasing the terminal's NAS context, etc., without limitation.

[0037] In other words, by instructing not to release the context established by the first network function for the terminal, unnecessary signaling overhead can be avoided when the first network enters an idle state due to the lack of data and / or signaling from the terminal and then tries to establish a connection with the terminal again.

[0038] Secondly, a communication method is provided. This method is applied to the access network side and can be implemented by a first access network device, or a module (e.g., circuit, chip, or chip system) in the first access network device, or a logical node, logical module, or software that can implement all or part of the functions of the access network device. Taking the execution of the first access network device as an example, the method includes: obtaining the identifier of a first network function of the first network; sending connection information between the terminal and the second network to the first network function according to the identifier of the first network function, wherein the connection information indicates whether there is a connection between the terminal and the second network, and the first network and the second network serve the terminal.

[0039] In one possible implementation, the method provided by the second aspect further includes: obtaining third indication information, which instructs the first network function to send connection information.

[0040] In one possible implementation, sending connection information between the terminal and the second network to the first network function based on the identifier of the first network function includes: when the second network establishes a connection with the terminal through the first access network device, sending connection information to the first network function based on the identifier of the first network function, wherein the connection information indicates that the terminal has a connection with the second network.

[0041] In one possible implementation, the method provided by the second aspect further includes: receiving a first temporary identifier from a second network, the first temporary identifier being a temporary identifier assigned to the terminal by the second network before the terminal establishes a connection with the second network through the first access network device.

[0042] In one possible implementation, the connection information includes a first temporary identifier and indication information for indicating that the terminal is in a connected state.

[0043] In one possible implementation, the method provided by the second aspect further includes: receiving a second temporary identifier from a second network, the second temporary identifier being a temporary identifier assigned to the terminal by the second network when the terminal establishes a connection with the second network through the first access network device; and sending the second temporary identifier to the first network function.

[0044] In one possible implementation, the method provided by the second aspect further includes: sending first identification information or second identification information to a first network function, wherein the first identification information is identification information assigned by the first access network device to the terminal on a first interface to identify the terminal, the first interface is an interface for interaction between the first access network device and the first network function, and the second identification information is identification information for identifying the terminal on a second interface, the second interface is an interface for interaction between the first access network device and the second network function of the second network.

[0045] In one possible implementation, the first identification information is a transaction identifier, which is used to identify the terminal or to indicate the data and / or signaling to be transmitted to the terminal.

[0046] In one possible implementation, after sending connection information to the first network, the method provided by the second aspect further includes: receiving a first message from a function of the first network, the first message including first identification information or second identification information, the first identification information or second identification information being used by the first access network device to determine that the first message is a message for a terminal.

[0047] In one possible implementation, the method provided by the second aspect further includes: sending first instruction information to the terminal according to the first message, the first instruction information being used to instruct the terminal to initiate a connection establishment process to the first network; or, the first message includes first identification information, an identifier assigned by the first network to the terminal on the first interface to identify the terminal, and data and / or signaling to be transmitted to the terminal; the method provided by the second aspect further includes: sending data and / or signaling to be transmitted to the terminal according to the first message.

[0048] In one possible implementation, the method provided by the second aspect further includes: receiving a third temporary identifier and a fourth temporary identifier from a first network function, wherein the third temporary identifier is a temporary identifier assigned to the terminal by the first network before the terminal establishes a connection with the first network through the first access network device, and the fourth temporary identifier is a temporary identifier assigned to the terminal by the first network when the terminal establishes a connection with the first network through the first access network device; and sending the third temporary identifier and the fourth temporary identifier to a second network function of the second network.

[0049] In one possible implementation, the method provided by the second aspect further includes: receiving instruction information from the first network for instructing the first access network device to send a third temporary identifier and a fourth temporary identifier to the second network function.

[0050] In one possible implementation, the method provided by the second aspect further includes: receiving an identifier of a second network function from a first network; wherein the identifier of the second network function is used for communication between the first access network device and the second network function.

[0051] In one possible implementation, the method provided by the second aspect further includes: sending a second indication message to the first network function, the second indication message being used to indicate that the context established by the first network function for the terminal should not be released.

[0052] It should be understood that the beneficial effects of the second aspect and any of its implementations can be found in the first aspect, and will not be repeated here.

[0053] Thirdly, a communication method is provided, which is applied to a second network side, such as a second network function of the second network, a device for implementing the second network function, or a logical node, logical module, or software capable of implementing all or part of the second network function. Taking the application of this method to a second network function as an example, the method includes: obtaining an identifier of a first network function of a first network, and a service terminal of the first network and the second network; based on the identifier of the first network function, sending connection information between the terminal and the second network to the first network function, wherein the connection information indicates whether a connection exists between the terminal and the second network.

[0054] In one possible implementation, sending connection information between the terminal and the second network to the first network function based on the identifier of the first network function includes: when the second network establishes a connection with the terminal through the first access network device, sending connection information to the first network function based on the identifier of the first network function, wherein the connection information indicates that the terminal has a connection with the second network.

[0055] In one possible implementation, obtaining the identifier of the first network function of the first network includes: obtaining a third temporary identifier, wherein the third temporary identifier is a temporary identifier assigned to the terminal by the first network when the terminal establishes a connection with the first network through the second access network device, and the second access network device is the access network device that serves the terminal before the terminal establishes a connection with the first access network device; and determining the identifier of the first network function based on the third temporary identifier.

[0056] In one possible implementation, obtaining the third temporary identifier includes: obtaining the third temporary identifier from the second access network device when the terminal establishes a connection with the second network through the second access network device, or when the second access network device and the second network update the context of the terminal; or, when the terminal establishes a connection with the second network through the first access network device, receiving a registration request from the terminal, the registration request including the third temporary identifier.

[0057] In one possible implementation, obtaining the identifier of the first network function includes: obtaining the identifier of the first network function from the second access network device when the terminal establishes a connection with the second network through the second access network device, or when the second access network device updates the context of the terminal with the second network function.

[0058] In one possible implementation, the connection information includes a permanent identifier for the terminal, as well as indication information indicating that the terminal is in a connected state.

[0059] In one possible implementation, the method provided by the third aspect further includes: sending second identification information to the first network function, the second identification information being identification information for identifying the terminal on the second interface, the second interface being the interface through which the first access network device interacts with the second network function.

[0060] In one possible implementation, the method provided by the third aspect further includes: sending a second indication message to the first network function, the second indication message being used to indicate that the context established by the first network function for the terminal should not be released.

[0061] It should be understood that the beneficial effects of the third aspect and any of its implementations can be found in the first aspect, and will not be repeated here.

[0062] Fourthly, a communication method is provided, which is applied to the terminal side, such as a terminal or a communication module in the terminal, or a circuit or chip in the terminal 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). Taking the application of this method to a terminal as an example, the terminal is registered to a first network and a second network respectively. The method includes: receiving a paging message from the second network; responding to the paging message from the second network; and, if the terminal establishes a connection with the second network through a first access network device, initiating a connection establishment process to the first network through the first access network device.

[0063] In this embodiment of the application, when the terminal registers with the first network and the second network respectively, if the terminal responds to the paging message of the second network and establishes a connection with the second network through the first access network device, then the terminal also initiates a connection establishment process to the first network through the first access network device. This allows the terminal to avoid switching its current serving access network device, thereby solving the problem that the terminal's connection state becomes disordered due to receiving paging messages from multiple access network devices from the first network and switching its current serving access network device (i.e., the first access network device) to other access network devices (e.g., the terminal's connection state in the second network changes from connected to idle).

[0064] In one possible implementation, the connection establishment process is initiated to the first network through the first access network device. This includes: when the terminal receives a paging message from the first network, the connection establishment process is initiated to the first network through the first access network device. In other words, after the terminal establishes a connection with the second network, the terminal does not actively establish a connection with the second network. Instead, when the terminal receives paging messages from the first network from multiple access network devices, the terminal initiates a connection establishment process to the first network through its current serving access network device (i.e., the first access network device). This resolves the problem of connection status disorder caused by the terminal switching serving access network devices.

[0065] Fifthly, a communication apparatus is provided for implementing the various methods described above. This communication apparatus can be a first network function, a first access network device, a second network function, or a terminal as described in any of the above aspects or implementations, or an apparatus containing the aforementioned first network function, first access network device, second network function, or terminal, or an apparatus included in the aforementioned first network function, first access network device, second network function, or terminal, such as a chip. The communication apparatus includes modules, units, or means corresponding to the above methods, which can be implemented in hardware, software, or by hardware executing corresponding software. The hardware or software includes one or more modules or units corresponding to the above functions.

[0066] In some possible designs, the communication device may include a processing module and a transceiver module. The transceiver module, also referred to as a transceiver unit, is used to implement the transmission and / or reception functions in any of the above aspects and their possible implementations. The transceiver module may consist of transceiver circuits, transceivers, transceivers, or communication interfaces. The processing module can be used to implement the processing functions in any of the above aspects and their possible implementations.

[0067] In some possible designs, the transceiver module includes a sending module and a receiving module, which are used to implement the sending and receiving functions in any of the above aspects and any possible implementation methods.

[0068] A sixth aspect provides a communication device, comprising: at least one processor; the processor being configured to execute a computer program or instructions to cause the communication device to perform the methods of any of the above aspects.

[0069] In one possible implementation, the communication device further includes the memory. Optionally, the memory is coupled to the processor; the memory may be integrated with the processor, or it may be independent of the processor. Optionally, the processor is used to execute computer programs or instructions stored in the memory.

[0070] In one possible implementation, the memory is independent of the communication device.

[0071] In one possible implementation, the communication device further includes a communication interface for communicating with modules outside the communication device.

[0072] The communication device can be a first network function, a first access network device, a second network function, or a terminal in any of the above aspects or any implementation thereof, or a device that includes the first network function, the first access network device, the second network function, or the terminal, or a device included in the first network function, the first access network device, the second network function, or the terminal, such as a chip.

[0073] In a seventh aspect, a computer-readable storage medium is provided, which stores a computer program or instructions that, when executed on a communication device, enable the communication device to perform the methods of any of the above aspects or any implementation thereof.

[0074] Eighthly, a computer program product containing instructions is provided, which, when run on a communication device, enables the communication device to execute any of the above aspects or any implementation thereof.

[0075] Ninthly, a communication device (e.g., a chip or chip system) is provided, the communication device including a processor for implementing the functions involved in any of the above aspects or any implementation thereof.

[0076] In some possible designs, the communication device includes a memory for storing necessary program instructions and data.

[0077] In some possible designs, when the device is a chip system, it can be composed of chips or contain chips and other discrete components.

[0078] It is understood that when the communication device provided by any of the fifth to ninth aspects is a chip, the aforementioned sending action / function can be understood as an output, and the aforementioned receiving action / function can be understood as an input.

[0079] The technical effects of any of the design methods in aspects five through nine can be found in the technical effects of the different design methods in aspects one through four above, and will not be repeated here.

[0080] In a tenth aspect, a communication system is provided, the communication system comprising: a first network function of the first aspect and any implementation thereof described above.

[0081] In some possible designs, the communication system further includes: a first access network device of the second aspect and any implementation thereof, and / or a second network function of the third aspect and any implementation thereof.

[0082] Eleventhly, a communication system is provided, comprising: a terminal of the fourth aspect above and any implementation thereof. Attached Figure Description

[0083] Figure 1 is a schematic diagram of the architecture of a new radio interface (NR) system provided in an embodiment of this application;

[0084] Figure 2 is a schematic diagram of a terminal registration process defined by the 3GPP Third Generation Partnership Project (3GPP) according to an embodiment of this application.

[0085] Figure 3 is a schematic diagram of the transition between the connection management CM connected state and the CM idle state on the terminal side according to an embodiment of this application;

[0086] Figure 4 is a schematic diagram of the transition between the CM connected state and the CM idle state on the core network CN side according to an embodiment of this application;

[0087] Figure 5 is a schematic diagram of the process by which a user equipment (UE) determines the transition between Radio Resource Control (RRC) state and CM state according to an embodiment of this application.

[0088] Figure 6 is a schematic diagram of a process for a UE to recover from the RRC inactive state to the RRC connected state according to an embodiment of this application;

[0089] Figure 7 is a schematic diagram of a process provided in an embodiment of this application to trigger a UE to recover from the RRC inactive state to the RRC connected state from the network side;

[0090] Figure 8 is a schematic diagram of a non-limiting distributed subnet architecture provided in an embodiment of this application;

[0091] Figure 9 is a schematic diagram of a UE connection state disorder or UE failure to respond to network paging provided in an embodiment of this application;

[0092] Figures 10 and 11 are schematic diagrams illustrating the process of a terminal establishing connections with a first network and a second network respectively through an access network device according to an embodiment of this application.

[0093] Figures 12-16 are schematic flowcharts of a communication method provided in an embodiment of this application;

[0094] Figures 17 and 18 are schematic diagrams of the structure of a communication device provided in an embodiment of this application. Detailed Implementation

[0095] To facilitate understanding of the embodiments of this application, the following points will be explained before introducing the embodiments of this application.

[0096] 1. In the embodiments of this application, for ease of description, when it comes to numbering or indexing, the numbering can start from 1 continuously, or it can start from 0 continuously, or it can start from any parameter, without any specific limitation.

[0097] 2. In the embodiments of this application, "including" and "including but not limited to" have the same meaning. For example, A including B means that A also includes other contents besides B. In addition, unless explicitly stated that A does not include C, A may also include C. This is stated uniformly here and will not be repeated below.

[0098] 3. The terms "predefined", "pre-defined", "pre-configured (or pre-configured)", and "protocol agreement" can be used interchangeably. Pre-definition can be achieved by pre-storing corresponding codes, tables, or other means of indicating relevant information in the device (e.g., a terminal or access network device). This application does not limit the implementation method. "Storing" can refer to storing in one or more memories.

[0099] 4. The “protocol” involved in the embodiments of this application may refer to standard protocols in the field of communication, such as Long Term Evolution (LTE) protocol, New Radio (NR) protocol, Wireless Fidelity (Wi-Fi) protocol, and related protocols applied to future communication systems. The embodiments of this application do not limit this.

[0100] 5. In the embodiments of this application, descriptions such as "when," "under the circumstances," "if," and "if" all refer to the fact that the device (e.g., a terminal or access network device) will take corresponding actions under certain objective circumstances. They are not time-limited, nor do they require the device to perform a judgment action during implementation, nor do they imply any other limitations. Furthermore, the descriptions of conditions such as "when," "if," "under the circumstances," and "if" can be understood as necessary conditions, without limiting whether the condition is a sufficient condition or a necessary and sufficient condition. For example, "in the case of A, execute B" can be understood as "if at least A is satisfied, execute B."

[0101] 6. In the embodiments of this application, "sending information" can be understood as one device (or apparatus) sending information to another device (or apparatus), or it can also be understood as one logical module within a device sending information to another logical module. For example, "access network device sending information" can be understood as the access network device sending information to another device (such as a terminal or network function), or it can be understood as logical module 1 in the access network device sending information to logical module 2 in the access network device.

[0102] Furthermore, in the embodiments of this application, "receiving information" can be understood as one device (or apparatus) receiving information from another device (or apparatus), or it can also be understood as a logical module within a device receiving information from another logical module. For example, "access network device receiving information" can be understood as the access network device receiving information from another device or function (such as a network function), or it can be understood as logical module 1 in the access network device receiving information from logical module 2 in the access network device.

[0103] Furthermore, "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...(access network device)" or "receiving information from...(access network device)" can be understood as the source of the information being the access network device, and may include receiving information directly or indirectly from the access network device. Information may undergo necessary processing between the source and destination, such as format changes, but the destination can understand the valid information from the source. Similar expressions in this application can be understood in a similar way, and will not be elaborated further here.

[0104] 7. In the description of the embodiments of this application, unless otherwise stated, "and / or" in the embodiments of this application indicates that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. A and B can be singular or plural. Furthermore, "at least one of the following" or similar expressions refer to any combination of these items, including any combination of singular or plural items. In addition, to facilitate a clear description of the technical solutions of the embodiments of this application, the terms "first" and "second" are used in the embodiments of this application to distinguish identical or similar items with substantially the same function and effect. Those skilled in the art will understand that the terms "first" and "second" do not limit the quantity or execution order, and the terms "first" and "second" are not necessarily different. Meanwhile, in the embodiments of this application, words such as "exemplary" or "for example" are used to indicate examples, illustrations, or explanations.

[0105] The embodiments of this application can be applied to LTE systems or NR systems, LTE and NR hybrid networking systems, vehicle-to-everything (V2X) systems, device-to-device (D2D) systems, machine-to-machine (M2M) communication systems, Internet of Things (IoT) systems (such as narrowband Internet of Things (NB-IoT) systems), Wi-Fi systems, non-terrestrial networks (NTN) systems, and future communication systems, etc. Alternatively, the communication system can also be an open radio access network (O-RAN or ORAN) or a cloud radio access network (CRAN), without limitation.

[0106] To facilitate understanding, we will first use the NR system as an example to introduce the relevant technical terms in this application, and then introduce the distributed subnetwork.

[0107] First, the NR system architecture

[0108] The NR system can also be called the 5th generation (5G) system. As shown in Figure 1, the NR system includes a terminal, an access network (AN), and a core network (CN). The terminal can send a registration request to the CN through the AN to initiate the registration process, enabling the terminal to register or access the CN, and thus establish a connection with the CN (e.g., a non-access-stratum (NAS) connection), that is, the terminal and the CN can transmit control signaling.

[0109] The following sections will introduce the terminal, AN, and CN respectively.

[0110] A terminal can be a terminal with transceiver capabilities, or a chip or chip system that can be installed on the terminal. A terminal can also be referred to as user equipment (UE), access terminal, subscriber unit, user station, mobile station (MS), mobile station, remote station, remote terminal, mobile device, user terminal, wireless communication equipment, user agent, or user apparatus. The terminals in the embodiments of this application may be mobile phones, cellular phones, smartphones, tablets, wireless data cards, personal digital assistants (PDAs), wireless modems, handsets, laptop computers, machine-type communication (MTC) terminals, computers with wireless transceiver capabilities, virtual reality (VR) terminals, augmented reality (AR) terminals, wireless terminals in industrial control, wireless terminals in self-driving, wireless terminals in remote medical care, wireless terminals in smart grids, wireless terminals in transportation safety, wireless terminals in smart cities, wireless terminals in smart homes, vehicle-mounted terminals, roadside units (RSUs) with terminal functions, etc. The terminal of this application may also be an on-board module, on-board unit, on-board component, on-board chip or on-board unit that is built into a vehicle as one or more components or units.

[0111] The aforementioned AN is used to implement access-related functions, providing network access capabilities for authorized users and determining transmission links of different quality levels to transmit user data based on user level, service requirements, etc. The AN forwards control signaling and user data between the terminal and the CN. The AN may include: access network equipment or access network apparatus, also known as radio access network (RAN) apparatus or RAN equipment.

[0112] For example, the RAN may include: access network equipment or base station in a future communication network; or in a future communication network, the RAN may have other naming methods, all of which are covered within the protection scope of the embodiments of this application, and this application does not limit them in any way. Alternatively, the RAN can include 5G (such as a gNB in ​​an NR network), or one or a group of antenna panels (including multiple antenna panels) of a 5G base station, or network nodes constituting a gNB, transmission and reception point (TRP) or transmission point (TP), or transmission measurement function (TMF), such as a building base band unit (BBU), or a centralized unit (CU) or distributed unit (DU), an RSU with base station functionality, or a wired access gateway, or the 5G core network. Alternatively, the RAN can also include access points (APs) in a wireless fidelity (Wi-Fi) system, wireless relay nodes, wireless backhaul nodes, various forms of macro base stations, micro base stations (also known as small cells), relay stations, access points, wearable devices, or vehicle-mounted equipment, etc.

[0113] The Network Controller (CN) is primarily responsible for maintaining the subscription information of the mobile network and providing terminals with functions such as session management, mobility management, policy management, and security authentication. The CN mainly includes all or some of the following functions (or network functions, NFs):

[0114] User plane function (UPF), authentication server function (AUSF), access and mobility management function (AMF), session management function (SMF), network slice selection function (NSSF), network exposure function (NEF), network repository function (NRF), policy control function (PCF), unified data management (UDM), unified data repository (UDR), or application function (AF).

[0115] It is understood that the functions involved in the embodiments of this application can also be described as entities, network elements, or functional entities, etc. For example, AMF can be described as AMF network element, AMF function, AMF entity, or AMF functional entity, etc. Other NFs can use similar alternative expressions, and the embodiments of this application do not limit this.

[0116] It is understood that the embodiments of this application can be applied to a variety of different services, such as enhanced mobile broadband (eMBB), URLLC, massive machine-type communication (mMTC), immersive communication, massive communication, ubiquitous connections, integrated artificial intelligence and communication, or integrated sensing and communication. To meet the further requirements of the above-mentioned different services for transmission latency, reliability, and coverage, higher resource utilization is required.

[0117] Second, the terminal registration process

[0118] Currently, the terminal registration process defined by the 3rd generation partnership project (3GPP) is shown in Figure 2. Figure 2 mainly involves the interaction between the terminal (taking UE as an example), RAN, AMF, AUSF, and UDM. This registration process includes steps S201 to S208.

[0119] S201. The UE sends a registration request message to the RAN. Correspondingly, the RAN receives the registration request message from the UE.

[0120] The registration request message carries the registration type and the UE's identification information. The UE's identification information may include, for example, a subscription concealed identifier (SUCI), a 5G-globally unique temporary identifier (5G-GUTI), or a permanent equipment identifier (PEI). The 5G-GUTI is a temporary identifier assigned to the UE by the AMF. If the UE has never registered in the network before, it does not have a 5G-GUTI; in this case, the UE registers using the SUCI. The SUCI, after encryption, becomes the subscription permanent identifier (SUPI). Using the 5G-GUTI as much as possible is to minimize the UE's exposure of its SUPI, thus avoiding security issues.

[0121] In addition, the registration types are as follows:

[0122] 1) Initial registration: The registration process initiated when the UE is in the deregistration state;

[0123] 2) Mobility registration update: A registration process initiated by the UE when it needs to move;

[0124] 3) Periodic registration update: A registration process initiated when the UE is in the registration state and the periodic registration update timer expires;

[0125] 4) Emergency registration: A registration process initiated when the UE is in a service-restricted state.

[0126] It should be understood that for UE identification information, when the UE has a valid 5G-GUTI, the 5G-GUTI is carried in the registration request message; if the UE does not have a valid 5G-GUTI, then SUCI is carried. Additionally, in emergency registration, if the UE does not have a valid 5G-GUTI and also does not have SUPI, then PEI is carried in the registration request message.

[0127] It is understandable that the registration request message may also carry the data network name (DNN) requested by the UE, or single network slice selection assistance information (S-NSSAI), etc., and there are no restrictions on this.

[0128] S202, RAN Select the appropriate AMF.

[0129] It should be understood that the RAN can attempt to select an AMF based on its local configuration. If the RAN cannot select an AMF through local configuration, then the RAN can select an AMF based on a policy. The basis for the RAN to select an AMF based on a policy may be, for example, the DNN and / or S-NSSAI included in the registration request, or operator policies, and is not limited thereto.

[0130] S203. The RAN forwards the registration request message to the AMF. Accordingly, the AMF receives the registration request message from the RAN.

[0131] Choose the appropriate AUSF for S204 and AMF.

[0132] For example, the AMF can discover one or more AUSFs through the NRF and then select the appropriate AUSF. Furthermore, the relevant implementations for the AMF's selection of AUSFs can be found in the relevant descriptions of the 3GPP protocols, which will not be elaborated upon here.

[0133] It is understandable that AMF chooses a suitable AUSF that can perform security processes such as authentication.

[0134] The system interacts with S205, UE, AMF, AUSF, and UDM to complete mutual authentication between the UE and the network side.

[0135] For example, the ASF stores the authentication result of the UE, and the UE and AMF store the UE's context (e.g., NAS security context) generated during the authentication process.

[0136] S206. After the UE and the network side successfully authenticate each other, the AMF and UDM interact to obtain the UE's subscription data.

[0137] S207, AMF sends an N2 message to RAN. Correspondingly, RAN receives the N2 message from AMF.

[0138] It is understandable that the N2 message includes a NAS message that the RAN needs to forward to the UE. This NAS message includes a registration acceptance message sent by the AMF to the UE. For example, in the case of initial UE registration, the registration acceptance message may include the 5G-GUTI assigned to the UE by the AMF.

[0139] S208, the RAN sends a registration acceptance message to the UE. Correspondingly, the UE receives the registration acceptance message from the RAN.

[0140] It's understandable that after receiving the registration acceptance message, the UE can store its current registration state for later use when initiating service requests or session establishment requests (e.g., protocol data unit (PDU) session establishment requests). For example, when the UE needs to initiate a service request, it first determines its current registration state. If the UE is currently in the register management (RM) deregistration state (RM-DEREGISTERED), it needs to re-register for network selection. After completing network selection registration according to the network selection list, the UE enters the RM registration state (RM-REGISTERED). If the UE is currently in the RM registration state, it can determine the corresponding request message according to the UE route selection policy (URSP) rules and send the request message.

[0141] In addition, the above terminal registration process can be understood as the terminal registering with the network or the terminal accessing the network. This will be explained uniformly here and will not be repeated below.

[0142] It should be understood that the UE connection with the network (e.g., the core network CN) involved in the embodiments of this application may refer to the UE establishing a NAS connection (or non-access stratum (AS) connection) with the CN, or establishing a data connection, thereby the UE and the network side are in a connected state.

[0143] Third, terminal status management

[0144] Terminal state management primarily refers to managing the connection status between the terminal and the network side. As mentioned earlier regarding the NR system architecture shown in Figure 1, the network side can include the AN side and the CN side. Therefore, the connection status between the terminal and the network side can be divided into: the connection status between the terminal and the AN side, and the connection status between the terminal and the CN side. The connection status between the terminal and the AN side can be managed through radio resource control (RRC) status. The connection status between the terminal and the CN side can be managed through connection management (CM) status.

[0145] RRC states can include: RRC connected state (RRC_CONNECTED), RRC idle state (RRC_IDLE), and RRC inactive state (RRC inactive or RRC_INACTIVE).

[0146] RRC connection state: This means that the terminal has established an air interface connection (or AN signal connection established) with the RAN on the AN side, and the terminal and RAN can communicate through this air interface connection. In addition, the establishment of an air interface connection between the terminal and the RAN also means that the RAN has established the terminal's context. The terminal and the RAN can save the terminal's context for subsequent communication between the terminal and the RAN.

[0147] It should be understood that in the embodiments of this application, the establishment of an air interface connection between the terminal and the RAN can be replaced by: establishing an AN connection between the terminal and the RAN, or establishing an AN signal connection between the terminal and the RAN, or establishing an RRC connection between the terminal and the RAN, etc. This will be uniformly explained here and will not be repeated below.

[0148] RRC Idle State: This refers to the disconnection of the air interface connection between the terminal and the RAN (also known as releasing the RRC connection or releasing the AN signal connection), and the terminal simultaneously releases its context (e.g., access-stratum (AS) context), thus determining that the terminal is in the RRC Idle State. In the RRC Idle State, the terminal only receives limited downlink information and does not send uplink information. Uplink information refers to information sent by the terminal to the RAN, and downlink information refers to information sent by the RAN to the terminal. Limited downlink information includes, for example, the contents of the common search space, i.e., paging information, or broadcast information (e.g., downlink synchronization information, information contained in the master information block (MIB), or information contained in system information block (SIB) 1, etc.).

[0149] RRC Inactive State: The RRC inactive state is similar to the RRC idle state. For example, in both the RRC inactive and RRC idle states, the terminal receives the content of the paging common search space, or the terminal can perform cell reselection, and the principle of cell reselection is the same as in the RRC idle state. The main difference between the RRC inactive state and the RRC idle state is that in the RRC inactive state, the UE context is preserved on both the terminal side and the CN side. That is, the RRC connection between the terminal and the RAN is inactive, but the connection is still maintained on the CN side.

[0150] Furthermore, when paging a terminal within the RAN, the difference between the RRC idle state and the RRC inactive state lies in the scope of the paging RAN. For example, during the terminal registration process, the CN allocates an area (e.g., the UE registration area) to the terminal. This area includes a list of trace area identities (TAIs), which can include one or more cells. When the terminal moves outside of all cells included in the TAI list, the terminal executes a NAS registration update procedure so that the CN can update the terminal's registration area, i.e., update the TAI list for the terminal.

[0151] When a terminal is in RRC idle state, in order to locate the terminal, the CN will send a paging message to every cell (or the RAN corresponding to each cell) in the TAI list. It is understandable that, since the terminal is located in only one cell among all the cells included in the TAI list, sending a paging message to every cell in the TAI list would incur high signaling overhead.

[0152] To save signaling overhead, the cell range of the paging terminal should be reduced, meaning the granularity of the registration area (TA) should be decreased on the network side. For terminals in the RRC inactive state, a RAN-based notification area (RNA), which is smaller than the TA range, is introduced. The RNA is managed by the RAN, and the RAN can page the UE based on the RNA.

[0153] The CM state is primarily used to manage the connection status between the terminal and the CN. Similar to the RRC state, the CM state includes a connected state and an idle state, and the transition between these two states is related to the RRC state.

[0154] The following sections describe the CM state transitions on the terminal side and the CM state transitions on the CN side.

[0155] Figure 3 is a schematic diagram of the transition between CM connected state and CM idle state on the terminal side according to an embodiment of this application. As shown in Figure 3, on the terminal side (taking UE as an example), when an RRC connection is established between UE and RAN, the terminal enters the RRC connected state. At this time, UE can send an initial NAS message to AMF through RAN (for example, the relevant steps S201 to S203 of UE initiating registration in Figure 2), and then UE can determine that UE is in CM connected state.

[0156] As shown in Figure 3, when the UE releases the RRC connection with the RAN and releases the UE's context with the RAN, the UE determines that it is transitioning from the CM connected state to the CM idle state, i.e., the UE is in the CM idle state. It can be understood that when the UE is in the RRC idle state, the UE is in the CM idle state.

[0157] It should be understood that releasing a context can mean deleting the context or no longer saving the context. This will be explained uniformly here and will not be repeated below.

[0158] Figure 4 is a schematic diagram of the transition between CM connected state and CM idle state on the CN side according to an embodiment of this application. As shown in Figure 4, on the CN side (taking AMF as an example), when the UE sends a registration request message to the AMF through the RAN (i.e., step S203 in Figure 2), the AMF can establish the UE's N2 context with the RAN through a security authentication process. At this time, the AMF determines that the UE is in the CM connected state.

[0159] It should be understood that the UE's N2 context mainly involves the communication status, configuration, and signaling between the Access Network Equipment (RAN) and the AMF, used to support related terminal services, such as UE registration with the CN or establishing UE sessions (e.g., protocol data unit (PDU) sessions). It can be understood that the N2 interface between the RAN and AMF uses the Next Generation Application Protocol (NGAP), and the UE's N2 context includes an identifier pair (e.g., NGAP UE pair ID) that uniquely identifies the UE on the network side (or on the N2 interface). The NGAP UE pair ID includes: the N2 interface identifier assigned to the UE by the RAN (or RAN NGAP UE ID), and the N2 interface identifier assigned to the UE by the AMF on the CN side (or CN NGAP UE ID). The NGAP UE pair ID, composed of the RAN NGAP UE ID and the CN NGAP UE ID, can uniquely identify the UE on the N2 interface.

[0160] In addition, the CN NGAP UE ID can also be named AMF NGAP UE ID, or any other possible name. The identifier assigned by the core network CN for identifying the terminal on the N2 interface can be considered as the CN NGAP UE ID. This application embodiment does not limit this.

[0161] Similarly, the RAN NGAP UE ID can also be named by other names. Any temporary identifier assigned by the access network equipment to identify the terminal on the N2 interface can be considered as the RAN NGAP UE ID. This application embodiment does not limit this.

[0162] It should be understood that the embodiments in this application are illustrated using RAN NGAP UE ID and CN NGAP UE ID as examples, and will not be repeated below.

[0163] Additionally, the RAN sends a RAN NGAP UE ID to the AMF, and the AMF stores this RAN NGAP UE ID during the connection between the UE and the AMF. Similarly, the AMF sends a CN NGAP UE ID to the RAN, and the RAN stores this CN NGAP UE ID during the connection between the UE and the AMF.

[0164] In other words, on the RAN side, the RAN stores the UE's NGAP UE pair ID and the UE's identifier on the air interface (e.g., radio network temporary identity (RNTI)). The RAN can then accurately forward information exchanged between the UE and the AMF based on the UE's NGAP UE pair ID and RNTI. On the AMF side, the AMF stores the UE's NGAP UE pair ID, SUPI, and GUTI. The AMF can then determine which information is relevant to the UE and how to send information to the UE based on the UE's NGAP UE pair ID, SUPI, and GUTI.

[0165] As shown in Figure 4, when the UE's N2 context is released between the RAN and AMF (e.g., the UE is in RRC idle state), the AMF determines that the UE has entered the CM idle state from the CM connected state.

[0166] It should be understood that when releasing the N2 context of a UE, the RAN and AMF mainly delete the NGAP UE pair ID of the UE. The AMF may not delete the SUPI and GUTI (e.g., 5G-GUTI) of the UE. This is explained in a unified manner and will not be repeated below.

[0167] In other words, the AMF's determination that the UE is in the CM idle state can include: the AMF determining that the UE has entered the CM idle state when it receives information that the UE's AN signal connection has timed out or released the AN signal connection. Additionally, the AMF determines that the UE has entered the CM idle state when it determines that the connection between the UE's serving RAN and the AMF (or NGAP connection) and / or the UE's user plane connection has been released (assuming the network side established the UE's user plane connection).

[0168] As can be understood, based on the above explanations regarding RRC and CM states, after the terminal establishes an AN signal connection with the RAN, the terminal determines that it is in the RRC connection state, and the RAN also determines that it is in the RRC connection state. Additionally, on the terminal side, after sending the initial NAS message, the terminal determines that it is in the CM connection state, as explained below with reference to Figure 5.

[0169] Figure 5 is a schematic diagram of a UE determining the transition between RRC state and CM state according to an embodiment of this application. As shown in Figure 5, which uses the UE as the terminal and the gNB as the RAN as an example, the process includes steps S501 to S504.

[0170] S501, the UE sends an RRC establishment request message to the gNB. Correspondingly, the gNB receives the RRC establishment request message from the UE.

[0171] It should be understood that before step S501, since the UE has not yet established an RRC connection, the UE is in the RRC idle state and CM idle state.

[0172] S502, the gNB sends an RRC establishment message to the UE. Correspondingly, the UE receives the RRC establishment message from the gNB.

[0173] It should be understood that after step S502, an RRC connection is established between the UE and the gNB, and the UE is in the RRC connected state. However, the UE has not yet sent an initial NAS message to the AMF, so the UE is still in the CM idle state.

[0174] S503, the UE sends an RRC establishment complete message to the gNB. Correspondingly, the gNB receives the RRC establishment complete message from the UE.

[0175] Optionally, the UE sends a NAS message via the RRC establishment completion message. That is, the UE can send an initial NAS message to the AMF via the RRC establishment completion message, thereby determining whether the UE is in the RRC connected state or the CM connected state.

[0176] S504 and gNB send an initial NAS message to AMF. Correspondingly, AMF receives the initial NAS message from gNB.

[0177] It should be understood that on the AMF side, when an N2 context about the UE is established between the AMF and the gNB, the AMF determines that the UE is in the CM connected state.

[0178] Additionally, when the RRC connection between the UE and gNB is released, and the UE releases its context, the UE can transition from the RRC connected state to the RRC idle state, and the UE can transition from the CM connected state to the CM idle state.

[0179] As is understandable, the above uses the UE as an example to introduce the transition between the RRC connected state and the RRC idle state of the terminal. The following describes the transition between the RRC connected state and the RRC inactive state of the terminal.

[0180] Figure 6 is a schematic diagram of a process for a UE to recover from an RRC inactive state to an RRC connected state according to an embodiment of this application. As shown in Figure 6, the process includes steps S601 to S609.

[0181] S601, the UE sends an RRC recovery request message to the gNB. Correspondingly, the gNB receives the RRC recovery request message from the UE.

[0182] It is understandable that the RRC inactive state differs from the RRC idle state. When the UE is in the RRC inactive state, both the UE side and the AMF side still maintain the UE's context. That is, while the UE is in the RRC inactive state, it can still be in the CM connected state. Furthermore, the source (or previous service) gNB providing services to the UE maintains the UE's context. The AMF can page the UE through the previous service gNB.

[0183] Furthermore, since the UE is in an RRC inactive state, the air interface connection between the UE and the previous serving gNB is disconnected. Therefore, in step S601, the UE can send an RRC recovery request message to the gNB that has moved to the new area to request the restoration of the RRC connection. The RRC recovery request message may include an inactive RNTI (I-RNTI) provided by the previous serving gNB. The I-RNTI is used by the gNB to determine the identifier of the previous serving gNB so as to request the UE's context from the previous serving gNB.

[0184] It should be understood that, for the sake of brevity, gNB refers to the gNB that the UE needs to access during the process of recovering from the RRC inactive state to the RRC connected state. This will be explained uniformly here and will not be repeated below.

[0185] In addition, the source gNB and the previous service gNB have the same meaning. For the sake of brevity, they are collectively referred to as the previous service gNB. This will be explained in a unified manner here and will not be repeated below.

[0186] S602, gNB sends a retrieve UE context request message to the source serving gNB. Correspondingly, the serving gNB receives the retrieve UE context request message from gNB.

[0187] It is understandable that in the RRC inactive state, the previous serving gNB did not delete the UE's context, so the gNB can send a request message to the previous serving gNB to obtain the UE's context.

[0188] S603. The previous serving gNB sends a context response message to the gNB requesting the UE's context. Correspondingly, the gNB receives the context response message from the previous serving gNB.

[0189] It is understandable that the UE's context response message includes the UE's context for communication between the UE and the CN.

[0190] S604, the gNB sends an RRC recovery message to the UE. Correspondingly, the UE receives the RRC recovery message from the gNB.

[0191] It should be understood that after the gNB sends an RRC recovery message to the UE, the RRC connection between the UE and the gNB is restored, the UE enters the RRC connected state from the RRC idle state, and the UE is in the CM connected state.

[0192] S605, the UE sends an RRC recovery complete message to the gNB. Correspondingly, the gNB receives the RRC recovery complete message from the UE.

[0193] S606, the gNB sends an Xn-U address indication to the previous serving gNB. Correspondingly, the previous serving gNB receives the Xn-U address indication from the gNB.

[0194] It should be understood that, to prevent the loss of data cached by the last gNB for the UE, the gNB provides a user plane address to the next serving gNB so that the previous serving gNB can forward the data cached by the UE to that user plane address. It is understood that the Xn-U address indicates the user plane address provided by the aforementioned gNB, such as an Internet Protocol (IP) address or a port number, etc., and this application embodiment does not specifically limit this.

[0195] Additionally, step S606 is an optional step, and the Xn-U address indication can be carried by other messages or signaling (such as path switch request messages).

[0196] S607, gNB sends a path switching request message to AMF. Correspondingly, AMF receives the path switching request message from gNB.

[0197] It should be understood that the AMF in step S607 is the serving AMF, that is, the AMF that provides services to the UE in the network where the UE is registered. Additionally, the gNB can obtain the serving AMF information through the UE context response message in step S603.

[0198] S608, the AMF sends a path switch response message to the gNB. Correspondingly, the gNB receives the path switch response message from the AMF.

[0199] It is understandable that, according to steps S607 and S608, a connection regarding the UE is established between the gNB and the AMF, and the gNB can then notify the previous serving gNB to release the UE's context.

[0200] S609, the gNB sends a context message to the previous serving gNB to release the UE. Correspondingly, the previous serving gNB receives the context message from the gNB to release the UE.

[0201] It should be understood that the network side can also trigger the UE to recover from the RRC inactive state to the RRC connected state. For example, if the CN side discovers downlink data and / or downlink signaling related to the UE, the CN side can notify the RAN side, thereby triggering the RAN to page the UE, so that the UE recovers from the RRC inactive state to the RRC connected state. The process is explained below with reference to Figure 7.

[0202] Figure 7 is a schematic diagram of a process for triggering a UE to recover from an RRC inactive state to an RRC connected state on the network side, according to an embodiment of this application. As shown in Figure 7, the process includes steps S701 to S704.

[0203] S701, the previous service gNB determined that it triggered RAN paging UE.

[0204] As can be understood from the relevant description of step S601 in Figure 6, when the UE is in the RRC inactive state and CM connected state, the AMF still saves the UE's context (e.g., including the UE's N2 context) with the previous serving gNB, so the AMF can page the UE through the previous serving gNB.

[0205] In addition, the previous serving gNB determines whether to trigger RAN paging of the UE. For example, it could be that the previous serving gNB received downlink data or downlink signaling from the AMF sent by the UE. There are no restrictions on this.

[0206] It should be understood that the previous serving gNB can page within the cell controlled by that gNB; or, the previous serving gNB can also page through other gNBs, such as the gNB in ​​the area where the UE moves (i.e., the gNB in ​​Figure 6).

[0207] S702, The previous serving gNB sends a paging message to the gNB. Accordingly, the gNB receives the paging message from the previous serving gNB.

[0208] It is understandable that paging messages may include inactive RNTIs (I-RATIs). An I-RNTI is an RNTI assigned to the UE by the previous serving gNB, for example, when the UE enters the RRC inactive state, it is assigned to the UE by the previous serving gNB.

[0209] S703, gNB paging UE.

[0210] It is understandable that the gNB can page the UE via I-RNTI.

[0211] S704, the UE recovers from the RRC inactive state to the RRC connected state.

[0212] It is understood that the implementation of step S704 can be found in steps S601 to S609 shown in Figure 6, and will not be repeated here.

[0213] Fourth, distributed subnetwork

[0214] The existing standards define non-public networks (NPNs). An NPN is a network that provides services to specific users, distinct from public networks. In the 3GPP protocol definition, based on whether the CN is independent, non-public networks are divided into two types: stand-alone non-public networks (SNPNs) and public network integrated non-public networks (PNI-NPNs).

[0215] SNPN requires the deployment of independent core network equipment, resulting in high operational and maintenance costs, which are difficult for small and medium-sized enterprises to bear. PNI-NPN does not require additional core network deployment. It uses the operator's public network core network, employing methods such as slicing / data network name (DNN) to isolate specific resources and configure them for PNI-NPN use. Because this deployment method relies on the operator's core network, enterprises cannot achieve autonomous management of PNI-NPN and can only rely on the main network core network to provide corresponding functions. PNI-NPN cannot achieve agile deployment for enterprise needs. Therefore, in future network evolution, a distributed subnet deployment method needs to be proposed.

[0216] Figure 8 is a schematic diagram of a non-limiting distributed subnet architecture provided in an embodiment of this application. As shown in Figure 8, in this distributed subnet architecture, the core network can be divided into two parts: a first network and a second network.

[0217] It should be understood that, unless it is emphasized that the first network or the second network also includes the access network, the first network or the second network mentioned below refers to the core network. This will be stated uniformly here and will not be repeated below.

[0218] For example, the first network can be a public network (or a large network, or a central network), and the second network can be a subnetwork. Alternatively, the first network can be a subnetwork, and the second network can be a public network (or a large network, or a central network). In other words, the first network can be an SNPN, and the second network can be a PNI-NPN; or, the first network can be a PNI-NPN, and the second network can be an SNPN.

[0219] The public network (also known as the main network or central network) is a network deployed by the operator, possessing full CN (Network Component) functionality and providing all CN services to the terminal. Multiple subnets can exist, and a single terminal can access services from multiple subnets simultaneously. Network Functions (NFs) within a subnet are configured on demand; missing NFs can utilize the corresponding network within the main network to obtain services. In other words, some network functions within the central network can be shared by subnet users, meaning that the first network and the second network can jointly serve a single user (i.e., the terminal).

[0220] Optionally, the first network and the second network may share network functions (NF).

[0221] For example, in the architecture shown in Figure 8, a first network can be configured with a first network function, and a second network can be configured with a second network function. Both the first and second network functions can manage the connection state of the UE. The first and second network functions can implement some of the functions of the AMF in the CN. For example, the first network function can manage the CM state, perform NAS message routing, or provide N2 routing to the RAN side. As another example, the first network function can assign temporary identifiers to the terminal (e.g., 5G-GUTI in step S208 of Figure 2).

[0222] It is understood that the first network function provides N2 routing to the RAN side, including sending a CN NGAP UE ID bound to the RAN NGAP UE ID provided by the RAN side, and storing the RAN NGAP UE ID and CN NGAP UE ID, i.e., the NGAP UE pair ID. For details on the NGAP UE pair ID, please refer to the relevant explanation in Figure 4, which will not be elaborated upon here.

[0223] Alternatively, in the architecture shown in Figure 8, the AMF can be split into access management function (AM) and mobility management function (MM).

[0224] It is understandable that a large network can deploy a complete set of Network Functions (NFs), while a subnet can selectively deploy only some NFs. For example, suppose the first network in Figure 8 is the large network, and the second network is the subnet. As shown in Figure 8, the first network can be configured with network functions such as First Network Function, AM, MM, SMF (SM for short), AUSF, or UDM. The second network can be configured with some NFs as needed, such as Second Network Function, AM, MM, or SM.

[0225] As can be seen, the distributed subnet only configures a portion of the NFs as needed, thus eliminating the need for a complete set of NFs like SNPN, thereby saving on the operation and maintenance costs of the CN. Since the subnet only configures a portion of the NFs as required, the remaining unconfigured NFs still need to be provided by the main network to provide complete services to the terminals. Because the CN of the distributed subnet is deployed locally, it can be autonomously managed by the local area network or campus, enabling agile deployment of subnet NFs.

[0226] It should be understood that the aforementioned public network, main network, central network, or subnet are merely exemplary names, and other names may be used as the network evolves, without limitation. Similarly, the aforementioned AM, MM, first network function, or second network function are also merely exemplary names. For example, the first network function may also be called the first N2 proxy, and the second network function may be called the second N2 proxy. This application embodiment does not limit this.

[0227] Furthermore, the aforementioned first and second networks are not limited to large networks or subnets; they can also refer to networks located in different domains. For example, the first and second networks can be different public land mobile networks (PLMNs). Another example is that the first and second networks belong to different operators. Yet another example is that the first and second networks are networks in different domains under the same operator. Yet another example is that the first and second networks can be different non-public networks (e.g., SNPN or PNI-NPN).

[0228] Furthermore, the first network and the second network may not share network functions; this will be explained uniformly here and will not be repeated below.

[0229] As shown in Figure 8, a UE can establish connections with the first network and the second network through a RAN, which facilitates the independent transmission of control signaling between the UE and the first network, as well as between the UE and the second network. This avoids the transmission delay caused by the UE only establishing a connection with the first network, which would otherwise require the control signaling between the UE and the second network to be transmitted back to the first network (and vice versa).

[0230] However, when the UE establishes connections with the first network and the second network through a RAN, the connection status of the UE is managed independently by the first network and the second network. Changes in the connection status of the UE may cause the connection status of the UE to become disordered, or the UE may not respond to paging from the network side.

[0231] The following example, using Figure 9 as a reference, illustrates the disruption of the UE's connection status or the UE's failure to respond to paging from the network side.

[0232] Figure 9 is a schematic diagram illustrating a UE connection state disorder or UE failure to respond to network paging provided in an embodiment of this application. As shown in Figure 9(a), after the UE establishes connections with the main network and subnet through a RAN (e.g., RAN#1), the UE and RAN#1 are in an RRC connection state, while the main network and subnet are in a CM connection state. According to the aforementioned description of the UE registration process and the N2 context in Figure 2, the main network will decrypt the SUCI provided to the UE to obtain the SUPI, assign a temporary identifier (e.g., GUTI#1) to the UE, and establish a UE context with RAN#1. The UE context can be the UE's N2 context, such as including NGAP UE pair ID#1.

[0233] In other words, the UE context stored in the main network includes the following UE identifiers: SUPI, GUTI#1, and NGAP UE pair ID#1. Similarly, the UE context stored in the subnet may include the following UE identifiers: SUPI, GUTI#2, and NGAP UE pair ID#2. The N2 context of the UE stored in RAN#1 includes: the main network identifier (e.g., PLMN ID), NGAP UE pair ID#1, the subnet identifier, and NGAP UE pair ID#2.

[0234] As shown in Figure 9(b), after the UE disconnects from RAN#1 and enters the RRC idle state, RAN#1 releases the UE's N2 context with the network side, and the network side then enters the CM idle state. At this time, RAN#1 releases the UE's N2 context, the main network releases NGAP UE pair ID#1, and the subnet releases NGAP UE pair ID#2. That is, the main network can save SUPI and GUTI#1, and the subnet can save SUPI and GUTI#2.

[0235] Additionally, assuming the network has downlink data and / or downlink signaling from the UE, triggering paging of the UE, the network can paging the UE to all cells included in the UE's registered trace area identity (TAI) list. For example, it can send paging messages to the RANs corresponding to all cells included in the TAI list.

[0236] As shown in Figure 9(c), assuming the UE responds to a paging request from the network and establishes a connection with the network (or transitions from the CM idle state to the CM connected state), the UE first establishes an RRC connection with RAN#2. It should be understood that due to the UE's mobility, the UE may be in a different RAN-covered cell when paging, and therefore RAN#2 may or may not be RAN#1; this is not a limitation.

[0237] Additionally, RAN#2 establishes an N2 context for the UE with the main network. This N2 context may include NGAP UE pair ID#3. At this time, the UE identifiers stored in the main network's UE context include: SUPI, GUTI#3, and NGAP UE pair ID#3. It should be understood that since the UE re-registers with the main network, the main network will assign a temporary identifier GUTI#3 to the UE again. GUTI#3 may be the same as or different from GUTI#1, which is not limited to this.

[0238] It is understandable that, since the subnet and the main network independently manage the UE's connection status, the subnet is unaware of the UE's current connection status with the RAN (or the main network) (e.g., whether a connection has been re-established). Subsequently, when the subnet receives downlink data and / or downlink signaling from the UE, it will page the UE. Considering that the UE has already established an RRC connection with the new RAN (i.e., RAN#2), the UE may no longer detect the paging message broadcast on the air interface. That is, the UE does not respond to the paging on the network side, meaning the subnet has not successfully paged the UE, resulting in the inability to transmit downlink data and / or downlink signaling between the UE and the subnet. For example, the UE may not detect paging messages other than those from RAN#2. Another example is that, assuming RAN#2 broadcasts a paging message in the RRC idle state, the UE may not be able to correctly decode the RRC idle state paging message. Yet another example is that even if the UE correctly decodes the RRC idle state paging message, the UE may ignore the paging message or consider it erroneous, meaning the UE does not respond to the subnet's paging.

[0239] Furthermore, assuming the UE detects a paging message from RAN#3 indicating that it is being paged by the subnet, the UE is unsure whether it should release its RRC connection with RAN#2 to establish an RRC connection with another RAN (e.g., RAN#3), thereby establishing a connection with the subnet. For example, if the UE disconnects its RRC connection with RAN#2 and establishes an RRC connection with RAN#3, the connection between the UE and the main network will be lost, preventing data transmission and causing a disruption in the UE's connection status on the main network side.

[0240] In other words, when the main network pages the UE and enables the UE to re-establish a connection with the main network, the subnet is unaware of the current connection status between the UE and the RAN (or the main network). Therefore, when the subnet pages the UE, it may cause the UE's connection status to become disordered.

[0241] It should be understood that the network architecture and business scenarios described in Figures 8 and 9 above are for the purpose of more clearly illustrating the technical solutions of the embodiments of this application, and do not constitute a limitation on the technical solutions provided by the embodiments of this application. As those skilled in the art will know, with the evolution of network architecture and the emergence of new business scenarios, the technical solutions provided by the embodiments of this application are also applicable to similar technical problems.

[0242] To address the above problems, this application provides the following technical solutions: Solution 1 and Solution 2.

[0243] Option 1: In scenarios where the terminal registers with both a first network and a second network, the first network function of the first network can obtain the connection information between the terminal and the second network. Then, when the first network desires to establish a connection with the terminal, the first network function determines whether to paging the terminal or establish a connection corresponding to the terminal with the first access network device, depending on whether a connection exists between the terminal and the second network. Specifically, the terminal establishes a connection with the second network through the first access network device. For example, if the terminal does not have a connection with the second network (e.g., the terminal is in a CM idle state on the second network), the first network function paging the terminal; if the terminal has a connection with the second network (e.g., the terminal has established a connection with the second network through the first access network device), the first network function establishes a connection corresponding to the terminal with the first access network device.

[0244] It is understandable that the second network function of the second network can also obtain the connection information between the terminal and the first network. Then, when the second network expects to establish a connection with the terminal, the second network function determines the paging terminal or establishes a connection with the first access network device based on whether the terminal has a connection with the first network.

[0245] In other words, in scenarios where terminals register with the first network and the second network respectively, the first network function can obtain the connection information between the terminal and the second network. Then, when the first network expects to establish a connection with the terminal, the first network function determines whether to establish a paging terminal or establish a connection with the first access network device based on whether the terminal has a connection with the second network. Thus, the first network can synchronize the connection status of the terminal with the second network, solving the problem of disordered connection status of the terminal shown in Figure 9(c).

[0246] In addition, since the first network function will not page the terminal when the terminal is connected to the second network, but will establish a connection with the first access network device corresponding to the terminal, the problem shown in Figure 9(c) of not responding to the first network paging will not occur, resulting in the first network and the terminal being unable to establish a connection.

[0247] Option 2: In scenarios where the terminal registers with the first network and the second network respectively, the terminal responds to the paging message of the second network. If the terminal establishes a connection with the second network through the first access network device, the terminal initiates a connection establishment process to the first network through the first access network device.

[0248] It is understandable that the terminal can also respond to the paging message of the first network. When the terminal establishes a connection with the first network through the first access network device, the terminal can initiate a connection establishment process to the second network through the first access network device.

[0249] In other words, in scenarios where the terminal registers with the first network and the second network respectively, if the terminal responds to the paging message of the second network and establishes a connection with the second network through the first access network device, then the terminal also initiates a connection establishment process to the first network through the first access network device. This allows the terminal to avoid switching its current service access network device, thereby solving the problem of the terminal's connection status becoming disordered due to switching service access network devices.

[0250] The above scheme will be described in detail below with reference to the accompanying drawings.

[0251] It should be understood that the names of parameters or information carried in messages, signaling, or signals between various devices or functions in the following embodiments of this application are just examples, and other names may be used in actual implementations. This application does not specifically limit these names.

[0252] Furthermore, the executing entity in the following method embodiments can be a device or function, a device or function comprising that device or function, or a device or function comprising that device or function. For example, the executing entity can be a first network function of a first network, a second network function of a second network, a first access network device, or a terminal; it can also be a device comprising a first network function, a second network function, a first access network device, or a terminal; or it can be a module or device within a first network function, a second network function, a first access network device, or a terminal. For ease of description, the following method embodiments use a first network function, a second network function, an access network device, and a terminal as examples of executing entities for illustration.

[0253] To facilitate understanding of Scheme 1 and Scheme 2 above, the process of the terminal registering to the first network and the second network respectively will be explained first.

[0254] It is understood that in the embodiments of this application, the terminal registers to the first network and the second network respectively, which can be implemented in various ways, such as implementation method 1 and implementation method 2, which will be described below.

[0255] Implementation Method 1

[0256] In implementation method 1, the terminal registers with the first network and the second network respectively through an access network device, similar to the initial registration process of the terminal shown in Figure 2. The following is an illustrative description with reference to Figure 10.

[0257] Figure 10 is a schematic diagram illustrating a process by which a terminal establishes connections with a first network and a second network through an access network device, according to an embodiment of this application. As shown in Figure 10, the terminal is a UE, the access network device is a RAN, the first network is a main network, and the second network is a subnet. The main network includes the first network function (taking N2 Proxy #1 as an example), AM#1, MM#1, and AUSF (or UDM). The second network includes the second network function (taking N2 Proxy #2 as an example), AM#2, and MM#2. The process shown in Figure 10 includes steps S1001 to S1016.

[0258] S1001, the UE sends AN message #1 to the RAN. Correspondingly, the RAN receives AN message #1 from the UE.

[0259] AN message #1 includes registration request #1. It can be understood that registration request #1 may include the UE's SUCI and registration type. The registration type could be, for example, initial registration. Registration request #1 can be found in the relevant explanation of step S201 in Figure 2, and will not be repeated here.

[0260] Optionally, AN message #1 includes AN parameter #1. AN parameter #1 is used by the RAN to select the network to access. For example, the RAN can select whether to access the main network or the subnet based on AN parameter #1. As another example, the RAN determines whether to select N2 proxy #1 of the main network or N2 proxy #2 of the subnet based on AN parameter #1.

[0261] For example, AN parameter #1 can include the identifier of the network to be accessed. The identifier of the network to be accessed can be the identifier of the main network or the identifier of the subnet. It can be understood that if AN parameter #1 includes the identifier of the main network, the RAN determines the main network for the UE to register with based on the identifier of the main network, and then the RAN can select N2 proxy #1. Similarly, if AN parameter #1 includes the identifier of the subnet, the RAN selects N2 proxy #2 based on the identifier of the subnet.

[0262] It should be understood that the identifier of the main network or the identifier of the subnet can be a PLMN ID or any other possible identifier used to identify the network, and this application embodiment does not specifically limit this.

[0263] In addition, the UE can pre-configure relevant information about the main network and subnets, allowing it to determine the network it wants to access based on either the main network or subnet information. For example, the pre-configured subnet information may include: service information (or business information) provided by the subnet, or the subnet's identifier. The UE can determine whether to establish a connection with the subnet based on whether the service provided by the subnet is the service it wants, and thus AN parameter #1 may include the subnet's identifier.

[0264] It should be understood that when the UE has pre-configured relevant information about the main network and relevant information about the subnet, the UE can determine whether to access the main network or the subnet respectively. The UE can access the subnet first and then access the main network; or, the UE can access the main network first and then access the subnet. This application embodiment does not specifically limit this.

[0265] For example, AN parameter #1 may include the identifier of the main network, the identifier of the subnet, and priority indication information for indicating the network the UE should preferentially access. The priority indication information can be used to indicate whether the UE should preferentially access the main network or the subnet. For example, the priority indication information may directly indicate the main network or the subnet, or it may include the priority of the main network and the priority of the subnet. If the priority of the main network is higher than the priority of the subnet, the UE preferentially accesses the main network, and the RAN selects N2 proxy #1; if the priority of the main network is lower than the priority of the subnet, the UE preferentially accesses the subnet, and the RAN selects N2 proxy #2. It is understood that this application embodiment does not specifically limit the specific indication method of the priority indication information.

[0266] It is understood that AN parameter #1 may also include the identifier of the main network and the identifier of the subnet. Whether the UE prioritizes accessing the main network or the subnet depends on the local configuration of the RAN, and this application embodiment does not limit this.

[0267] It should be understood that if the UE has not pre-configured relevant information about the main network, the UE can first access the main network (i.e., the identifier of the network to be accessed in AN parameter #1 is the identifier of the main network), and then obtain relevant information about the subnet from the main network (for example, the registration acceptance message sent through the main network carries relevant information about the subnet). After obtaining the relevant information about the subnet, the UE can determine whether to access the subnet based on that information. If the UE determines to access the subnet, it can initiate a registration process with the subnet.

[0268] In addition, the RAN can also choose to access the main network or the subnet according to the local configuration, which is not limited in this embodiment of the application.

[0269] For ease of understanding, the following steps are illustrated using the example of the UE first accessing the main network (i.e., the RAN selects N2 agent #1 and sends registration request #1 to N2 agent #1), and then accessing the subnet.

[0270] S1002, RAN sends registration request #1 to N2 agent #1. Accordingly, N2 agent #1 receives registration request #1 from RAN.

[0271] It is understandable that the RAN transmits the registration request #1, which can be seen in step S203 in Figure 2, and will not be repeated here.

[0272] Optionally, the RAN also sends the RAN-side N2 interface #1 identifier (e.g., RAN NGAP UE ID #1) assigned to the UE by the RAN to the N2 agent #1. Accordingly, the N2 agent #1 receives the RAN NGAP UE ID #1 from the RAN.

[0273] It should be understood that the N2 interface #1 mentioned above refers to the interface between the RAN and the main network (or N2 agent #1).

[0274] In addition, RAN NGAP UE ID#1 and registration request#1 can be sent together or separately, without limitation.

[0275] S1003, N2 agent #1 sends registration request #1 to AM #1. Accordingly, AM #1 receives registration request #1 from N2 agent #1.

[0276] Optionally, N2 Agent #1 also sends GUTI #1 to AM #1. GUTI #1 is assigned by N2 Agent #1. GUTI #1 can reuse an existing GUTI (e.g., 5G-GUTI) or it can be a newly defined temporary identifier, which is not limited.

[0277] In addition, GUTI#1 and registration request#1 can be sent together or separately, without limitation.

[0278] S1004, AM#1 sends an authentication request to AUSF. Correspondingly, AUSF receives the authentication request from AM.

[0279] It is understandable that authentication requests may include the UE's SUCI.

[0280] The authentication process is performed between S1005, AUSF, MM#1, AM#1, N2 proxy#1, and UE.

[0281] It is understandable that the AUSF interacts with the subscription database (e.g., UDM) based on the authentication request to obtain the UE's authentication parameters. The AUSF, MM#1, AM#1, N2 agent#1, and the UE interact to execute the authentication process and establish a security context.

[0282] Optionally, during the authentication process, N2 Agent #1 can send the N2 interface #1 identifier (e.g., CN NGAP UE ID #1) assigned to the UE by N2 Agent #1 on the CN side to the RAN. For example, during the authentication process, N2 Agent #1 can carry CN NGAP UE ID #1 when sending information from the CN to the RAN.

[0283] Additionally, if the RAN does not send the RAN NGAP UE ID#1 to the N2 agent#1 in step S1002, then the RAN can send the RAN NGAP UE ID#1 to the N2 agent#1 during the authentication process. In other words, during the authentication process, the RAN and the N2 agent#1 exchange the RAN NGAP UE ID#1 and the CN NGAP UE ID#1.

[0284] S1006, AM#1 obtains the UE's subscription data.

[0285] For example, AM#1 can obtain the UE's subscription data from UDM.

[0286] It is understandable that, according to the relevant description of AN parameter #1 in the aforementioned step S1001, the main network can also obtain the relevant information of the subnet and then send it to the UE, so that the UE can obtain the relevant information of the subnet and thus the UE initiates the registration process with the subnet.

[0287] Optionally, the UE's subscription data may also include subnet-related information. This subnet-related information includes the subnet's identifier and the services provided by the subnet.

[0288] Alternatively, step S1006 can be replaced by AM#1 obtaining indication information #1. Indication information #1 is used to indicate that the UE can obtain service information provided by the subnet through the subnet.

[0289] S1007, AM#1 sends the UE's identification information #1 and registration acceptance message #1 to N2 agent #1. Correspondingly, N2 agent #1 receives the UE's identification information #1 and registration acceptance message #1 from AM#1.

[0290] The UE's identification information #1 may include GUTI#1 and SUPI. GUTI#1 may be assigned by AM#1 or by N2 agent #1 in step S1003. For example, if N2 agent #1 did not assign GUTI in step S1003 (or N2 agent #1 did not send GUTI#1 to AM#1), AM#1 will assign GUTI#1 to the UE. Alternatively, if N2 agent #1 sends GUTI#1 to AM#1, then AM#1 may not assign a temporary identifier GUTI to the UE.

[0291] Registration Acceptance Message #1 includes NAS Registration Acceptance Message #1. NAS Registration Acceptance Message #1 includes the UE's temporary identifier (i.e., GUTI#1). NAS Registration Acceptance Message #1 can be found in the registration acceptance message of step S207 in Figure 2, and will not be described again.

[0292] As can be understood from the description of step S207 in Figure 2, the GUTI#1 in the NAS registration acceptance message #1 is sent to the UE so that the UE can subsequently use GUTI#1 to initiate service requests. AM#1 sends the UE's GUTI#1 and SUPI to N2 agent #1, and N2 agent #1 can then store the UE's GUTI#1 and SUPI. Based on the UE's GUTI#1 and SUPI, N2 agent #1 determines which messages are sent to or from the UE, that is, performs NAS routing and N2 routing on the main network side.

[0293] Optionally, if the UE's subscription data includes subnet-related information, or if AM#1 obtains instruction information #1, the registration acceptance message #1 also includes subnet-related information. The registration acceptance message #1 also includes subnet-related information for the UE to subsequently initiate the registration process with the subnet.

[0294] Optionally, registration acceptance message #1 also includes registration acceptance. Registration acceptance is used to notify N2 agent #1 that the network accepts the UE's registration request.

[0295] It is understandable that, according to the aforementioned explanation in Figure 4 regarding the AMF on the CN side determining that the UE is in the CM connected state, when N2 agent #1 establishes the UE's N2 context or when an NGAP pair UE ID#1 exists, N2 agent #1 determines that the UE is in the CM connected state. In other words, if in step S1005, N2 agent #1 assigns CN NGAP UE ID#1 to the UE, and N2 agent #1 exchanges RAN NGAP UE ID#1 and CN NGAP UE ID#1 with the RAN, N2 agent #1 can determine that the UE is in the CM connected state, or in other words, N2 agent #1 determines that the UE is in the CM connected state on the main network side.

[0296] Additionally, if N2 Agent #1 does not assign CN NGAP UE ID #1 in step S1005, N2 Agent #1 may assign CN NGAP UE ID #1 to the UE in response to receiving the registration acceptance message #1.

[0297] S1008, N2 Agent #1 sends NGAP pair UE ID #1 and NAS registration acceptance message #1 to RAN. Correspondingly, RAN receives NGAP pair UE ID #1 and NAS registration acceptance message #1 from N2 Agent #1.

[0298] It is understood that NGAP pair UE ID#1 includes RAN NGAP UE ID#1 and CN NGAP UE ID#1. For example, RAN NGAP UE ID#1 may be sent by RAN to N2 agent#1 in step S1002, and CN NGAP UE ID#1 may be allocated by N2 agent#1 in step S1005. Alternatively, RAN NGAP UE ID#1 and CN NGAP UE ID#1 may be allocated in step S1005. Yet another example is that CN NGAP UE ID#1 may also be allocated by N2 agent#1 in step S1008; this embodiment does not specifically limit this.

[0299] Additionally, NAS registration acceptance message #1 can be found in step S1007, and will not be repeated here.

[0300] It should be understood that the RAN should determine the identifier of N2 Agent #1 to associate (or bind) the identifier of N2 Agent #1 with NGAP pair UE ID #1 so that the RAN can subsequently send messages about the UE to N2 Agent #1.

[0301] Furthermore, the RAN can determine the identifier of N2 Agent #1 in various ways. For example, the RAN can obtain the identifier information of N2 Agent #1 based on the source of the message received in step S1008. The identifier information of N2 Agent #1 is used to determine the identifier of N2 Agent #1. The identifier information of N2 Agent #1 can be, for example, the identifier of N2 Agent #1 itself, or the identifier information of N2 Agent #1 can be composed of the identifier of N2 Agent #1 and other identifiers, or the identifier information of N2 Agent #1 can be any other identifier information that can identify N2 Agent #1. This application embodiment does not specifically limit this.

[0302] For example, N2 agent #1 sends GUTI #1 to the RAN. Correspondingly, the RAN receives GUTI #1 from N2 agent #1. The protocol can predefine how GUTI #1 can derive the identifier of N2 agent #1. For instance, GUTI #1 can contain the identification information of N2 agent #1.

[0303] For example, N2 Agent #1 sends its identification information to the RAN. Correspondingly, the RAN receives the identification information from N2 Agent #1 and then determines the identifier of N2 Agent #1 based on this information. It can be understood that if GUTI #1 cannot derive the identifier of N2 Agent #1 (e.g., the protocol does not specify that GUTI can derive the identifier of N2 Agent), N2 Agent #1 can send its identification information to the RAN.

[0304] S1009, the RAN sends a NAS registration acceptance message #1 to the UE. Correspondingly, the UE receives the NAS registration acceptance message #1 from the RAN.

[0305] It is understandable that the RAN transmits NAS registration acceptance message #1 to the UE.

[0306] Additionally, the UE receives NAS registration acceptance message #1 from the RAN, indicating that the UE has established a connection with the RAN. The UE can save the registration status between the UE and the RAN as RM registration status in order to initiate service requests to the RAN.

[0307] It should be understood that the aforementioned RM registration status refers to the registration status between the UE and the main network. The UE can save the registration status corresponding to different networks. Even if the UE has already stored the registration status between the UE and the main network, the UE can still initiate registration with the subnet.

[0308] S1010, the UE sends AN message #2 to the RAN. Correspondingly, the RAN receives AN message #2 from the UE.

[0309] AN message #2 includes the subnet identifier and registration request #2. Registration request #2 is similar to registration request #2, and may include the UE's SUCI and registration type, which will not be elaborated here.

[0310] Optionally, AN message #2 may also include AN parameter #2, which may include parameters for the RAN to select an N2 agent within the subnet, and is not limited thereto.

[0311] Alternatively, AN message #2 may include AN parameter #2, which includes the identifier of the subnet.

[0312] S1011, RAN sends registration request #2 to N2 agent #2. Accordingly, N2 agent #2 receives registration request #2 from RAN.

[0313] It is understandable that the RAN transmits the registration request #2, which can be found in step S1002 and will not be repeated here.

[0314] Optionally, the RAN also sends the RAN-side N2 interface #2 identifier (RAN NGAP UE ID #2) assigned to the UE by the RAN to the N2 agent #2. Accordingly, the N2 agent #2 receives the RAN NGAP UE ID #2 from the RAN.

[0315] It should be understood that the N2 interface #2 mentioned above refers to the interface between the RAN and the subnet (or N2 agent #2).

[0316] In addition, RAN NGAP UE ID#2 and registration request#2 can be sent together or separately, without limitation.

[0317] S1012, N2 agent #2 sends registration request #2 to AM #2. Accordingly, AM #2 receives registration request #2 from N2 agent #2.

[0318] Optionally, N2 Agent #2 also sends GUTI #2 to AM #2. GUTI #2 is assigned by N2 Agent #2. GUTI #2 can reuse an existing GUTI (e.g., 5G-GUTI) or it can be a newly defined GUTI; there is no limitation on this.

[0319] In addition, GUTI#2 and registration request#2 can be sent together or separately, without limitation.

[0320] The authentication process is performed between S1013, AM#2, MM#2, N2 agent#2, N2 agent#1, AM#1, and AUSF.

[0321] As explained in steps S1004 and S1005 above, a subnet can share the ASUF of the main network, thus executing step S1013. For example, there is an interface between the subnet and the main network, which can be used by AM#2 to access ASUF.

[0322] Additionally, in step S1013, N2 agent #2 can assign the N2 interface #2 identifier (e.g., CN NGAP UE ID #2) on the CN side to the UE. Optionally, during the authentication process, N2 agent #1 can send the CN NGAP UE ID #2 to the RAN. For example, during the authentication process, N2 agent #2 can carry the CN NGAP UE ID #2 when sending information from the CN to the RAN.

[0323] Furthermore, if the RAN does not send RAN NGAP UE ID#2 to N2 Agent #2 in step S1011, then the RAN can send RAN NGAP UE ID#2 to N2 Agent #2 during the authentication process. In other words, if the RAN and N2 Agent #2 exchange RAN NGAP UE ID#2 and CN NGAP UE ID#2 during the authentication process, then the RAN and N2 Agent #2 establish the UE's N2 context, and thus N2 Agent #2 can determine that the UE is in CM connected state, or in other words, N2 Agent #2 determines that the UE is in CM connected state on the subnet side.

[0324] S1014, AM#2 sends the UE's identification information#2 and registration acceptance message#2 to N2 agent#2. Correspondingly, N2 agent#2 receives the UE's identification information#2 and registration acceptance message#2 from AM#2.

[0325] It is understandable that step S1014 is similar to step S1007. The difference between UE identification information #2 and UE identification information #1 is that UE identification information #1 can include GUTI#2 and SUPI. GUTI#2 can be allocated by AM#2 or by N2 agent #2 in the aforementioned step S1012. For example, if N2 agent #2 does not send GUTI#2 to AM#2 in the aforementioned step S1012, AM#2 allocates GUTI#2 for the UE. Alternatively, if N2 agent #2 sends GUTI#2 to AM#2, then AM#2 may not allocate a temporary identifier GUTI for the UE.

[0326] Registration Acceptance Message #2 includes NAS Registration Acceptance Message #2. NAS Registration Acceptance Message #2 includes the UE's temporary identifier (i.e., GUTI#2). GUTI#2 is sent to the UE so that the UE can subsequently use GUTI#2 to initiate service requests. Additionally, AM#2 sends the UE's GUTI#2 and SUPI to N2 Agent #2, allowing N2 Agent #2 to store the UE's GUTI#2 and SUPI. Based on the UE's GUTI#2 and SUPI, N2 Agent #2 determines which messages are sent to or originate from the UE, i.e., performs NAS routing and N2 routing on the subnet side.

[0327] It is understood that, similar to registration acceptance message #1, registration acceptance message #2 may also include registration acceptance, which is used to notify the N2 agent #2 subnet to accept the UE's registration request. According to the relevant description in step S1013 above, if the N2 agent #2 does not allocate CN NGAP UE ID #2 in step S1013, the N2 agent #1 may, in response to receiving the registration acceptance in registration acceptance message #2, allocate CN NGAP UE ID #2 for the UE.

[0328] S1015, N2 Agent #2 sends NGAP pair UE ID #2 and NAS registration acceptance message #2 to RAN. Correspondingly, RAN receives NGAP pair UE ID #2 and NAS registration acceptance message #2 from N2 Agent #2.

[0329] It is understood that NGAP pair UE ID#2 includes RAN NGAP UE ID#2 and CN NGAP UE ID#2. For example, RAN NGAP UE ID#2 may be sent by RAN to N2 agent#2 in step S1011, and CN NGAP UE ID#1 may be allocated by N2 agent#2 in step S1013. Alternatively, RAN NGAP UE ID#1 and CN NGAP UE ID#1 may be allocated in step S1013. Furthermore, CN NGAP UE ID#1 may also be allocated by N2 agent#2 in step S1015; this embodiment does not specifically limit this.

[0330] Additionally, NAS registration acceptance message #2 can be found in step S1014, and will not be repeated here.

[0331] It should be understood that the RAN should determine the identifier of N2 Agent #2 in order to associate (or bind) the identifier of N2 Agent #2 with NGAP pair UE ID #2 so that the RAN can subsequently send messages about the UE to N2 Agent #2.

[0332] Furthermore, the RAN determines the identifier of N2 Agent #2 in a similar manner to determine the identifier of N2 Agent #1 in step S1008. For example, the RAN can obtain the identifier information of N2 Agent #2 based on the source of the message received in step S1015. The identifier information of N2 Agent #2 is used to determine the identifier of N2 Agent #12. The identifier information of N2 Agent #2 is similar to that of N2 Agent #1; please refer to the description of the identifier information of N2 Agent #1 in step S1008, which will not be repeated here.

[0333] For example, N2 agent #2 sends GUTI #2 to the RAN. Correspondingly, the RAN receives GUTI #2 from N2 agent #2. The protocol can predefine that GUTI #2 can derive the identifier of N2 agent #2.

[0334] For example, N2 Agent #2 sends its identification information to the RAN. Correspondingly, the RAN receives the identification information from N2 Agent #2 and then determines the identifier of N2 Agent #2 based on this information. It can be understood that if GUTI #2 cannot derive the identifier of N2 Agent #2, N2 Agent #2 can send its identification information to the RAN.

[0335] S1016, RAN sends NAS registration acceptance message #2 to UE. Correspondingly, UE receives NAS registration acceptance message #1 from RAN.

[0336] It is understandable that the RAN transmits the NAS registration acceptance message #2 to the UE.

[0337] Additionally, the UE receives NAS registration acceptance message #2 from the RAN, indicating that the UE has established a connection with the subnet. The UE can save the registration status between the UE and the subnet as RM registration status in order to initiate service requests to the subnet.

[0338] As per the embodiments of this application, the UE can establish connections with the main network and the sub-network through a RAN, thereby enabling the UE to independently transmit data and / or signaling with the first network and with the second network. This avoids the need for the data and / or signaling transmitted between the UE and the other network to be transmitted back to the network with which the UE is connected due to the UE establishing a connection with one of the networks in the main network or the sub-network, thus reducing transmission latency.

[0339] It should be understood that, through steps S1001 to S1016, the UE establishes connections with both the main network and the subnet. Specifically, the RAN stores the N2 context established by the RAN and the main network for the UE (e.g., identification information used to identify the UE on the interface between the RAN and the main network (i.e., NGAP pair UE ID#1)), and the N2 context established by the RAN and the subnet for the UE (e.g., identification information used to identify the UE on the interface between the RAN and the subnet (i.e., NGAP pair UE ID#2)). The main network's N2 proxy #1 stores the UE's identification information #1 (including the UE's GUTI#1 and SUPI), and the NGAP pair UE ID#1. The subnet's N2 proxy #2 stores the UE's identification information #2 (including the UE's GUTI#2 and SUPI), and the NGAP pair UE ID#2.

[0340] Implementation Method 2

[0341] The difference between Implementation Method 2 and Implementation Method 1 lies in the following: During the UE registration process with the main network, the RAN can obtain the UE's identification information #1 (e.g., GUTI#1) from the N2 agent #1 of the main network, and during the UE registration process with the subnet, the RAN sends this GUTI#1 to the N2 agent #2 of the subnet. Similarly, during the UE registration process with the subnet, the RAN obtains the UE's identification information #2 (e.g., GUTI#2) from the N2 agent #2 of the subnet and sends this GUTI#2 to the N2 agent #2 of the main network. Through this method, if the main network receives information about the UE in the subnet, the main network can retrieve the UE's context based on the UE's GUTI#2 in the subnet and obtain the UE's SUPI to identify the UE. Similarly, the subnet can also obtain the UE's SUPI based on the UE's GUTI#1 in the main network, and thus identify the UE.

[0342] In addition, in implementation method 2, assuming the UE first registers with the main network, during the UE registration process, the main network or RAN can determine that the UE expects to register with a subnet (or that the UE expects to establish a connection with the subnet). The RAN can then obtain the UE's GUTI#1 and send GUTI#1 and NGAP pair UE ID#1 to the N2 agent #2 of the subnet. For example, in step S1001 of Figure 10, the RAN can determine that the UE expects to register with both the main network and the subnet based on the AN parameter #2. The RAN can then instruct the main network to send the UE's GUTI#1 to the RAN, allowing the RAN to send GUTI#1 and NGAP pair UE ID#1 to the N2 agent #2 of the subnet. For example, in step S1006, AM#1 obtains the UE's subscription data, which includes information about the UE registering with a subnet (e.g., indication information #1). AM#1 can then send the UE's identification information #1 and the subnet's identifier to N2 agent #1. N2 agent #1 then sends the UE's identification information #1 and the subnet's identifier to the RAN. The RAN, based on the subnet's identifier, can send GUTI#1 and NGAP pair UE ID#1 to the subnet's N2 agent #2 during the UE subnet registration process. Similarly, assuming the UE registers with a subnet first, during the UE subnet registration process, the subnet or RAN can determine that the UE expects to register with the main network (or that the UE expects to establish a connection with the main network). The RAN can then obtain GUTI#2 and send GUTI#2 and NGAP pair UE ID#2 to the main network's N2 agent #1.

[0343] The following example, with reference to Figure 11, illustrates implementation method 2.

[0344] Figure 11 is a schematic diagram of a terminal registering to a first network and a second network respectively through an access network device, according to an embodiment of this application. As shown in Figure 11, similar to Figure 10, Figure 11 mainly describes the interaction between the UE, RAN, main network, and subnet. Furthermore, Figure 11 illustrates the example of the UE first accessing the main network and then the subnet. It can be understood that the UE can also first access the subnet and then the main network; the implementation method is similar to the process shown in Figure 11, and will not be repeated here.

[0345] The process shown in Figure 11 includes steps S1101 to S1117.

[0346] Steps S1101 to S1106 are similar to steps S1001 to S1006, and S1101 to S1106 can be found under S1001 to S1006. Steps S1109 to S1110 are similar to steps S1009 to S1010, and S1109 to S1110 can be found under S1009 to S1010. Steps S1113, S1114, and S1116 are similar to steps S1013, S1014, and S1016, and will not be described again.

[0347] The following describes steps S1107, S1108, S1111, S1112, S1115, and S1117.

[0348] S1107, AM#1 sends the UE's identification information #1, the subnet's identifier, and the registration acceptance message #1 to N2 Agent #1. Correspondingly, N2 Agent #1 receives the UE's identification information #1, the subnet's identifier, and the registration acceptance message #1 from AM#1.

[0349] It is understandable that the difference between step S1107 and step S1007 is that AM#1 also sends the subnet identifier to N2 agent#1. Based on the subnet identifier, N2 agent#1 can determine that the UE may register in the subnet later. Therefore, N2 agent#1 sends GUTI#1 and the subnet identifier to RAN based on the subnet identifier, so that RAN can subsequently send the UE's relevant subnet information (such as GUTI#1 and NGAP pair UE ID#2) to N2 agent#1.

[0350] S1108, N2 Agent #1 sends NGAP pair UE ID #1, GUTI #1, subnet identifier, and NAS registration acceptance message #1 to RAN. Correspondingly, RAN receives NGAP pair UE ID #1, GUTI #1, subnet identifier, and NAS registration acceptance message #1 from N2 Agent #1.

[0351] It is understandable that the difference between step S1108 and step S1008 is that N2 agent #1 also sends GUTI#1 and the subnet identifier to the RAN. The subnet identifier can be used by the RAN to send GUTI#1 to the N2 agent #2 of the subnet during the subsequent UE registration subnet process. GUTI#1 is used by the subnet to obtain the UE's SUPI to identify the UE. For example, after receiving GUTI#1, the N2 agent #2 of the subnet binds GUTI#1 with the UE's SUPI (or associates, corresponds, etc.), or binds GUTI#1 with the UE's context, so that N2 agent #2 can retrieve the UE's SUPI based on GUTI#1.

[0352] It should be understood that since the RAN usually transmits the NAS registration accept message #1, the RAN will not obtain the GUTI#1 and subnet identifiers from the NAS registration accept message #1. Therefore, by carrying the GUTI#1 and subnet identifiers outside the NAS registration accept message #1, the RAN can obtain the GUTI#1 and subnet identifiers. This is explained here and will not be repeated below.

[0353] S1111, the RAN sends GUTI#1 and registration request#2 (e.g., registration request#2 from the UE) to N2 agent#2. Accordingly, N2 agent#2 receives GUTI#1 and registration request#2 (e.g., registration request#2 from the UE) from the RAN.

[0354] It should be understood that the RAN transmits the registration request #2 from the UE to N2 agent #2. In addition, GUTI #1 is sent to the RAN by the network's N2 agent #1 in the aforementioned step S1108, and thus the RAN can send GUTI #1 to N2 agent #2.

[0355] It is understandable that the difference between step S1111 and step S1011 is that the RAN also sends GUTI#1 to N2 agent #2. According to the relevant explanation of step S1008 above, GUTI#1 can deduce the identifier of the N2 agent #1 of the main network, and then the N2 agent #1 of the subnet can interact with N2 agent #1 based on the identifier of the N2 agent #1 of the main network.

[0356] Additionally, the RAN can send the identification information of N2 Agent #1 to N2 Agent #2, so that if GUTI #1 cannot derive the identification of N2 Agent #1 (for example, if the protocol does not stipulate that GUTI can derive the identification of N2 Agent), N2 Agent #2 can determine the identification of N2 Agent #1 based on the identification information of N2 Agent #1.

[0357] In addition, the identification information of N2 agent #1 can be found in the relevant description in step S1008, and will not be repeated here.

[0358] It should be understood that N2 agent #2 stores GUTI #1.

[0359] S1112, N2 agent #2 sends GUTI #1 and registration request #2 to AM #2. Accordingly, AM #2 receives GUTI #1 and registration request #2 from N2 agent #2.

[0360] It is understandable that the difference between step S1112 and step S1012 is that N2 agent #2 also sends GUTI#1 to AM#2.

[0361] Optionally, the RAN can send the identification information of N2 Agent #1 to N2 Agent #2, so that if GUTI #1 cannot derive the identification of N2 Agent #1 (for example, the protocol does not stipulate that GUTI can derive the identification of N2 Agent), N2 Agent #2 can determine the identification of N2 Agent #1 based on the identification information of N2 Agent #1.

[0362] It is understandable that AM#2 can interact with the main network based on the identification information of GUTI#1 and / or N2 agent #1. In this way, AM#2 can send authentication requests to AUSF through N2 agent #2, N2 agent #1, and AM#1.

[0363] S1115, N2 Agent #2 sends NGAP pair UE ID #2, GUTI #2, and NAS registration acceptance message #2 to the RAN. Correspondingly, the RAN receives NGAP pair UE ID #2, GUTI #2, and NAS registration acceptance message #2 from N2 Agent #2.

[0364] It is understandable that the difference between step S1115 and step S1015 is that N2 agent #2 also sends GUTI#2 to RAN. According to the aforementioned explanation in step S1108 regarding RAN transparently transmitting NAS registration acceptance message #1, RAN cannot obtain GUTI#2 through NAS registration acceptance message #2; therefore, N2 agent #2 sends GUTI#2 to RAN. The function of GUTI#2 is similar to that of GUTI#1 in step S1108; GUTI#2 is used by the network to obtain the UE's SUPI to identify the UE, which will not be elaborated further here.

[0365] S1117, RAN sends a UE context update message to N2 agent #1. Correspondingly, N2 agent #1 receives the UE context update message from RAN. The UE context update message includes: NGAP pair UE ID#1 and GUTI#2.

[0366] It is understood that N2 Agent #1 can determine the UE based on NGAP pair UE ID #1 (e.g., determine the UE's SUPI), and then N2 Agent #1 can associate GUTI #2 with the UE. For example, N2 Agent #1 can associate GUTI #2 with the UE's SUPI, or associate GUTI #2 with the UE's context, without limitation.

[0367] Additionally, according to step S1115, the RAN receives GUTI#2 from N2 agent #2, and the RAN can send GUTI#2 to N2 agent #1 before step S1106. Furthermore, N2 agent #1 stores GUTI#2.

[0368] Optionally, the RAN can send the identification information of N2 Agent #2 to N2 Agent #1, so that if GUTI #2 cannot derive the identification of N2 Agent #2 (for example, the protocol does not stipulate that GUTI can derive the identification of N2 Agent), N2 Agent #1 can determine N2 Agent #2 based on the identification information of N2 Agent #2.

[0369] Additionally, the identification information for N2 agent #2 can be found in the relevant description in step S1015, and will not be repeated here.

[0370] It should be understood that, after the above steps S1101 to S1117, the UE establishes connections with the main network and the subnet, respectively. The difference between N2 Proxy #1 in Figure 11 and N2 Proxy #1 in Figure 10 is that N2 Proxy #1 in Figure 11 also stores GUTI#2, meaning that N2 Proxy #1 in Figure 11 stores the following UE identifiers: SUPI, GUTI#1, GUTI#2, and NGAP pair UE ID#1. Similarly, the difference between N2 Proxy #2 in Figure 11 and N2 Proxy #2 in Figure 10 is that N2 Proxy #2 in Figure 11 also stores GUTI#1, meaning that N2 Proxy #2 in Figure 11 stores the following UE identifiers: SUPI, GUTI#2, GUTI#1, and NGAP pair UE ID#2.

[0371] In addition, N2 agent #1 in Figure 11 also stores the identification information of N2 agent #2, and N2 agent #2 in Figure 11 also stores the identification information of N2 agent #1. Thus, if the identification of N2 agent cannot be derived from GUTI, N2 agent #1 determines N2 agent #2 based on the identification information of N2 agent #2, and N2 agent #2 determines N2 agent #1 based on the identification information of N2 agent #1.

[0372] In this embodiment, the UE can establish connections with both the main network and the subnet via RAN#1, thus avoiding the need for data and / or signaling transmitted between the UE and the other network to be transmitted back to the network with which the UE is connected due to the UE establishing a connection with one of the networks in the main network or subnet, thereby reducing transmission latency. Furthermore, since the RAN can also send the temporary identifier (GUTI#2) assigned to the UE by the subnet during the connection establishment process between the subnet and the UE to the main network, and send the temporary identifier (GUTI#1) assigned to the UE by the main network during the connection establishment process between the main network and the UE to the subnet, the main network or subnet can know that the UE has established a connection with either the main network or the subnet. Additionally, by associating the temporary identifier assigned to the UE by their respective counterpart networks with the UE's context (or the UE's SUPI), when the main network and subnet exchange UE connection information via the RAN, the main network or subnet can send the temporary identifier assigned to the UE on its side to the RAN. The counterpart network can then retrieve the UE's context (e.g., the UE's SUPI) based on this temporary identifier, thereby identifying the UE.

[0373] As you can understand, the above describes the process of the terminal establishing connections with the first network and the second network respectively. Scheme 1 will be introduced below.

[0374] Option 1

[0375] In Scheme 1, the first network can obtain the terminal's connection information from the second network or from the terminal's current serving access network device. Conversely, the second network can obtain the terminal's connection information from the first network or from the terminal's current serving access network device. In this way, the first and second networks can synchronize the terminal's connection information, collaboratively manage the terminal's connection status, and resolve the connection status disorder issue shown in Figure 9(c), as well as the problem of the terminal failing to respond to the first network's paging, thus preventing the terminal from establishing a connection with the first network.

[0376] The following section first introduces Scheme 1-1 (i.e., the first network obtains the terminal's connection information from the terminal's current service access network device), and then introduces Scheme 1-2 (i.e., the first network obtains the terminal's connection information from the second network).

[0377] Option 1-1

[0378] Figure 12 is a schematic flowchart of a communication method provided in an embodiment of this application. As shown in Figure 12, the flowchart is based on the first network storing identification information (e.g., GUTI#2) assigned to the terminal by the second network, and the second network storing identification information (e.g., GUTI#1) assigned to the terminal by the first network. Furthermore, the first network storing identification information assigned to the terminal by the second network, and the second network storing identification information assigned to the terminal by the first network, can be implemented as shown in Figure 11, or in other ways. For example, the terminal can send identification information assigned to the terminal by the second network to the first network, and send identification information assigned to the terminal by the first network to the second network. This embodiment of the application does not specifically limit this.

[0379] As shown in Figure 12, the process illustrated here uses the first network as a subnet and the second network as the main network as an example. It involves interactions between the UE, RAN#1, RAN#2, N2 proxy#1, AM#1, MM#1, AUSF, N2 proxy#2, AM#2, and MM#2. Furthermore, the process shown in Figure 12 is illustrated using connection information indicating a connection between the UE and the main network. For example, the connection information may include GUTI#1 and indication information indicating that the UE is in a connected state (e.g., RRC connected state or CM connected state).

[0380] It is understandable that when there is no connection between the UE and the main network, and RAN#1 determines that RAN#1 and the UE are disconnected, and RAN#1 releases the UE's N2 context with the main network, RAN#1 can send connection information to the subnet to indicate that the UE and the main network are not connected, or that the connection has been released. When the UE re-establishes a connection with the main network, the UE's current serving RAN (e.g., RAN#2) can send connection information to the subnet to indicate that the UE and the main network are connected (or a connection has been established). In other words, when the UE's connection state changes, the UE's serving RAN can send connection information to the subnet to indicate whether a connection exists between the UE and the main network.

[0381] The process includes steps S1201 to S1221.

[0382] S1201 and UE establish connections with the main network and subnet respectively.

[0383] It is understood that the implementation of step S1201 can be seen in the process shown in Figure 11.

[0384] In addition, for ease of distinction, the RAN connected during the initial registration of the UE is called RAN#1. After the UE disconnects from RAN#1, the RAN it reconnects to is called RAN#2. It can be understood that after the UE disconnects from RAN#1, the RAN#2 it reconnects to may be RAN#1, or it may be another RAN besides RAN#1. This application embodiment does not specifically limit this.

[0385] In other words, RAN#1 and RAN#2 are only logically distinguished by the RAN where the UE disconnects and the RAN where the UE reconnects after disconnection. This will be explained uniformly here and will not be repeated below.

[0386] S1202, Release the AN connection between UE and RAN#1.

[0387] It is understandable that when the UE releases the AN connection with RAN#1, the UE can enter the RRC idle state and CM idle state.

[0388] S1203, release the N2 context of the UE between RAN#1 and N2 agent #1.

[0389] As can be understood from the descriptions in Figures 3-5 and Figure 9 above, after the RAN and UE release the AN connection, it will trigger the RAN and CN to release the UE's N2 context. For example, RAN#1 releases NGAP pair UE ID#1, N2 agent#1 releases NGAP pair UE ID#1, but N2 agent#1 retains the UE's GUTI#1, GUTI#2, and SUPI.

[0390] S1204, Release the N2 context of the UE between RAN#1 and N2 agent #2.

[0391] It is understandable that step S1204 is similar to step S1203, where RAN#1 releases NGAP pair UE ID#2 and N2 agent#2 releases NGAP pair UE ID#2, but N2 agent#2 retains UE's GUTI#1, GUTI#2, and SUPI.

[0392] It should be understood that since the UE has released the AN connection with RAN#1, and both N2 Agent #1 and N2 Agent #2 have released the NGAP pair UE ID, the UE enters the CM idle state from the CM connected state. Assuming that the main network or subnet has downlink data and / or downlink signaling for the UE at this time, the main network or subnet should send paging information to all RANs located in the TAI list registered by the UE (see the relevant description in Figure 9(b)) so that the UE can detect the paging message about the UE from the air interface side. The following explanation uses the main network paging the UE as an example.

[0393] S1205, AM#1 sends NAS message transfer #1 to N2 agent #1. Correspondingly, N2 agent #1 receives NAS message transfer #1 from AM#1.

[0394] Among them, NAS message transmission #1 includes the UE's SUPI and downlink data and / or downlink signaling sent from the network side to the UE.

[0395] It should be understood that since the various functions on the CN side are located within the trusted domain, the interaction between these functions can be identified using SUPI to identify the UE.

[0396] S1206, N2 Agent #1 sends a paging message to RAN #2. RAN #2 receives the paging message from N2 Agent #1.

[0397] Paging messages are used to trigger a UE to initiate a service request to the network or to initiate a connection establishment process between the UE and the network. For example, a paging message can be used to indicate to the network that the UE has downlink data and / or downlink signaling to be transmitted (or to indicate to the network that it has downlink data and / or downlink signaling to be transmitted). Another example is that a paging message can be used to instruct the UE to establish a connection with the network (or to instruct the UE to access the network).

[0398] Additionally, the paging message includes the UE's temporary mobile subscriber identity (TMSI) #1.

[0399] It is understood that N2 agent #1 can detect the UE's context based on the UE's SUPI, and thus determine the UE's GUTI#1. N2 agent #1 can determine TMSI#1 based on GUTI#1. TMSI can be a part of GUTI#1 (for example, TMSI#1 can be a shortened form of GUTI#1), or it can be derived from GUTI#1. This application embodiment does not specifically limit this.

[0400] It should be understood that in step S1206, N2 agent #1 sends paging messages to all RANs under the TAI list registered by the UE. That is, N2 agent #1 may also send paging messages to RAN #1. This is explained here and will not be repeated below.

[0401] It should also be understood that the above-mentioned connection establishment process between the UE and the network includes: a process in which the UE initiates a service request to the network, or a registration process initiated by the UE to the network. When the UE is in the state of registering with the network, after receiving a paging, the UE will initiate a service request to the network, but the UE may also initiate a registration process, such as the mobility registration update or periodic registration update described in step S201 of Figure 2. This application embodiment does not specifically limit this.

[0402] In addition, the specific process of the UE initiating a service request to the network can be found in steps S1207 to S1211 below, which will not be repeated here.

[0403] It should be understood that steps S1205 and S1206 are optional steps. In addition to paging, the UE may also establish a connection with the subnet due to mobility registration.

[0404] S1207, RAN#2 broadcasts a paging message. Correspondingly, the UE receives the paging message from RAN#2.

[0405] S1208, UE sends Service Request Message #1 to RAN#2. Correspondingly, RAN#2 receives Service Request Message #1 from UE.

[0406] Among them, the service request message #1 includes the GUTI#1 corresponding to TMSI#1.

[0407] It is understandable that after receiving a paging message, the UE can choose to send a service request message #1 or a registration request #1 (e.g., a mobility update registration request #1) via RAN#2. The service request message #1 or the registration request #1 can be carried via an RRC message.

[0408] For the sake of brevity, the following example uses the UE sending a service request message #1 to RAN#2 as an example. This will be explained uniformly here and will not be repeated below.

[0409] S1209, RAN#2 sends RAN NGAP UE ID#3 and service request message#1 to N2 agent#1. Correspondingly, N2 agent#1 receives RAN NGAP UE ID#3 and service request message#1 from RAN#2.

[0410] It is understandable that RAN#2 transparently transmits service request message #1.

[0411] Additionally, RAN NGAP UE ID#3 is the N2 interface#3 identifier assigned to the UE by RAN#2 on the RAN side. N2 interface#3 refers to the interface between RAN#2 and the main network (or N2 proxy#1).

[0412] S1210, N2 Agent #1 sends the NGAP pair UE ID #3, the N2 Agent #2 identifier of the subnet, and the temporary identifier information assigned to the UE by the main network to RAN #2. Correspondingly, RAN #2 receives the NGAP pair UE ID #3, the N2 Agent #2 identifier of the subnet, and the temporary identifier information assigned to the UE by the main network from N2 Agent #1.

[0413] Optionally, the temporary identification information allocated by the main network to the UE includes GUTI#1 and GUTI#3. GUTI#1 is the GUTI previously allocated to the UE by the main network, and GUTI#3 is the GUTI newly allocated to the UE by N2 Agent #1. RAN#2 can send GUTI#1 and GUTI#3 to N2 Agent #2 of the subnet. N2 Agent #2 of the subnet can detect the UE's context based on GUTI#1 to determine the UE's SUPI, thereby identifying the UE. In addition, N2 Agent #2 of the subnet can update GUTI#1 to GUTI#3 to facilitate subsequent identification of information about the UE sent by the main network.

[0414] It is understandable that the identifier of N2 Agent #2 in the subnet can be used by RAN #2 to determine the interaction address of N2 Agent #2 in order to send the UE's connection information to N2 Agent #2.

[0415] Additionally, the identifier of N2 agent #2 in the subnet is also used to instruct RAN #2 to send the UE's connection information to N2 agent #2 in the subnet (see step S1212). This connection information indicates that the UE has a connection with the main network.

[0416] Optionally, N2 agent #1 sends indication information #2 to RAN #2, which instructs RAN #2 to send the UE's connection information to N2 agent #2 of the subnet.

[0417] It is understood that the protocol can predefine the identifier of N2 Agent #2 of the subnet to be sent by N2 Agent #1 to RAN #2, that is, instruct RAN #2 to send connection information to N2 Agent #2 of the subnet. Furthermore, the aforementioned sending of the identifier of N2 Agent #2 of the subnet by N2 Agent #1 to RAN #2 to instruct RAN #2 to send connection information to N2 Agent #2 of the subnet can also be pre-negotiated between N2 Agent #1 and RAN #2; this embodiment of the application does not specifically limit this.

[0418] It is understood that N2 Agent #1 obtains the identifier of N2 Agent #2 based on the stored GUTI #2. Alternatively, if GUTI #2 cannot determine the identifier of N2 Agent #2, N2 Agent #2 can also store the identifier information of N2 Agent #2 sent by RAN #1 to determine the identifier of N2 Agent #2. The relevant implementation methods can be found in the relevant description of step S1117 in Figure 11 above, and will not be repeated here.

[0419] In addition, NGAP pair UE ID#3 includes: RAN NGAP UE ID#3 and CN NGAP UE ID#3. CN NGAP UE ID#3 is the N2 interface#3 identifier on the CN side assigned to the UE by N2 agent#1. RAN NGAP UE ID#3 is sent by RAN to N2 agent#1 in step S1209.

[0420] It is understandable that NGAP pair UE ID#3 can be used to uniquely identify the UE on N2 interface #3, which will not be elaborated here.

[0421] The subsequent connection establishment process is completed between S1211, UE, RAN#2, N2 agent#1, AM#1, and MM#1.

[0422] It is understood that after step S1210, RAN#2 can send GUTI#1 and GUTI#3 to the UE. Accordingly, the UE receives GUTI#1 and GUTI#3 from RAN#2 to update the UE's context with GUTI#3. Alternatively, in step S1211, the UE can obtain GUTI#1 and GUTI#3 through the connection establishment procedure.

[0423] In addition, the UE establishes a session through interaction with RAN#2, N2 Proxy#1, AM#1, and MM#1. The UE session can be used by the UE to receive downlink data from the main network side. The UE session can be, for example, a PDU session or other sessions used for transmitting service data; this application embodiment does not specifically limit this.

[0424] S1212, RAN#2 sends connection information to N2 Agent #2. Correspondingly, N2 Agent #2 receives connection information (or UE connection information) from RAN#2.

[0425] The connection information is used to indicate that the UE enters the RRC connection state. The UE entering the RRC connection state can be replaced by: the UE being in the RRC connection state, or the UE establishing an air interface connection, or the UE establishing an AN signal connection, or the UE establishing an AN connection, or the UE establishing an RRC connection with RAN#2, or the UE establishing an AN signal connection with RAN#2, or the UE establishing a connection with a second network (the main network), or instructing the UE to establish a connection with the peer network (e.g., the main network), etc., without limitation.

[0426] It should be understood that when the N2 agent #2 of the subnet releases the UE's N2 context (e.g., NGAP pair UE ID #2), sending connection information to the N2 agent #2 via RAN #2 allows the N2 agent #2 to determine that the UE has entered the RRC connected state from the RRC idle state (i.e., the UE has established an RRC connection with RAN #2). Consequently, when the N2 agent #2 sends downlink data and / or downlink signaling to the UE, the N2 agent #2 can determine that it should send relevant information to RAN #2 so that the RAN can notify the UE that there is downlink data and / or downlink signaling to be sent to the UE, or instruct the UE to establish a connection with the subnet. This avoids the N2 agent #2 sending paging messages to all RANs under the UE's registered TAI list, thus preventing the N2 agent #2 from sending paging instructions to multiple RANs when the UE has already established an RRC connection with RAN #2. This would prevent the UE from detecting paging messages from multiple RANs, making the UE uncertain whether it should release the RRC connection with RAN #2 to establish an RRC connection with other RANs (i.e., causing disorder in the UE's connection state).

[0427] In one possible implementation, the connection information includes the UE's identification information and RRC connection state indication information. The RRC connection state indication information is used to indicate that the UE is in RRC connection state.

[0428] Optionally, the UE's identification information can be temporary identification information assigned to the UE by the main network. The temporary identification information assigned to the UE by the main network can include GUTI#1. It can be understood that, according to the description of steps S1205 to S1210 above, since the main network is paging the UE to enable the UE to establish a connection with the main network through RAN#2, the information obtained by RAN#2 to identify the UE at this time is the UE's GUTI#1 and GUTI#3 (see step S12010). That is, considering that the N2 agent #2 of the subnet stores the UE's temporary identifier GUTI#1 in the main network, sending GUTI#1 to the N2 agent #2 through RAN#2 allows the N2 agent #2 to retrieve the UE's SUPI based on the UE's context according to GUTI#1, thereby identifying the UE.

[0429] Optionally, the temporary identifier information assigned to the UE by the network also includes GUTI#3.

[0430] In other words, N2 Agent #2 updates the UE's context according to GUTI #3 so that when N2 Agent #2 subsequently receives relevant information about the UE from RAN #2 on the main network side (the main network will use the newly assigned GUTI #3 to identify the UE), it can identify the UE according to GUTI #3.

[0431] It is understandable that, considering that the connection information includes relevant information from the network, such as the temporary identifier information assigned to the UE by the network, and combined with the connection information indicating that the UE is in the RRC connection state, the connection information used to indicate that the UE enters the RRC connection state can be replaced with: the connection information used to indicate that the UE has established a connection with the network, or that the UE has a connection with the network.

[0432] It is understandable that, considering that no N2 context for the UE has been established between N2 Agent #2 and RAN #2, the UE's N2 context includes an identification pair (i.e., NGAP pair UE ID) used to identify the UE on N2 interface #4 (i.e., the interface between RAN #2 and N2 Agent #2). Since there is no identification pair between N2 Agent #2 and RAN #2 to identify the UE, when the subnet subsequently receives downlink data and / or downlink signaling from the UE, N2 Agent #2 cannot indicate to RAN #2 which UE has downlink data and / or downlink signaling, thus triggering RAN #2 to broadcast a paging message for the UE.

[0433] Optionally, RAN#2 also sends identification information to N2 agent #2 for RAN-side identification of the UE.

[0434] It is understood that the identification information used by the RAN side to identify the UE can be replaced with: the identification information used by RAN#2 to identify the UE on N2 interface #4 (i.e., the interface between RAN#2 and the N2 agent #2 of the subnet); or the identification information allocated by RAN#2 to identify the UE on N2 interface #4; or the identification information allocated by RAN#2 to the terminal device to identify the UE on N2 interface #4.

[0435] In other words, considering that the UE has already established an RRC connection with RAN#2, according to the relevant description in Figure 9(c) above, the UE may not respond to the paging of the subnet. Instead, it may send identification information for the RAN side to identify the UE to N2 Agent #2 through RAN#2. This allows N2 Agent #2 to send a message including the identification information to RAN#2 when the subnet has downlink data and / or downlink signaling for the UE. This enables RAN#2 to identify the UE based on the identification information and then send information to the UE through the RRC connection between RAN#2 and the UE. As a result, RAN#2 can avoid paging the UE on the air interface, thus preventing the problem of the UE not responding to the paging of the subnet.

[0436] It should be understood that the identification information used by the RAN side to identify the UE can be divided into two types: one is the transaction ID, and the other is the RAN NGAP UE ID#4, which will be introduced below.

[0437] Method a: The identification information used by the RAN side to identify the UE is the transaction ID. The transaction ID is used to identify the UE, or to indicate that there is data and / or signaling to be transmitted to the UE.

[0438] It is understandable that the transaction identifier allocated by RAN#2 can be bound to the UE's identifier on the air interface (or the RRC connection between the UE and RAN#2) (e.g., RNTI). In this way, RAN#2 can determine the UE's identifier on the air interface based on the transaction identifier, and then send information to the UE through the RRC connection between the UE and RAN#2.

[0439] In addition, after receiving the transaction identifier, N2 Agent #2 can also bind (or associate) the transaction identifier with the UE's identifier (e.g., N2 Agent #2 determines the UE's SUPI based on GUTI#1).

[0440] In other words, by binding a transaction identifier to the UE, it is possible to identify which UE has downlink data and / or downlink signaling to transmit based on the transaction identifier. For example, N2 agent #2 can send a transaction identifier to RAN #2, and RAN #2 can then determine that the UE has downlink data and / or downlink signaling to transmit. RAN #2 does not need to page the UE on the air interface (i.e., RAN #2 broadcasts a paging message), but can instead directly instruct the UE to have downlink data and / or downlink signaling to transmit through the RRC connection, or instruct the UE to establish a connection with the subnet, causing the UE to initiate a connection establishment procedure with the subnet (e.g., the UE sends a service request message to the subnet).

[0441] In one possible implementation, the transaction identifier can be replaced with other identifiers.

[0442] It is understood that any identifier that can identify different UEs on the N2 interface can be used as the RAN-side identifier for identifying UEs in this application, and this application does not limit this.

[0443] Method b: The identification information used for RAN-side UE identification is the N2 interface #4 identifier assigned to the UE by RAN#2 on the RAN side. N2 interface #4 refers to the interface between RAN#2 and the subnet (or N2 proxy #2). The N2 interface #4 identifier assigned to the UE by RAN#2 on the RAN side can be RAN NGAP UE ID #4.

[0444] It is understood that method b is similar to the implementation of the aforementioned step S1209, that is, a context of the UE's N2 interface #4 is established between RAN#2 and N2 agent #2. The context of the UE's N2 interface #4 includes, for example, NGAP pair UE ID#4, which includes RAN NGAP UE ID#4 and CN NGAP UE ID#4.

[0445] In other words, by sending RAN NGAP UE ID#4 to N2 Agent#2, RAN#2 can establish the context of UE's N2 interface#4 (including NGAP pair UE ID#4) between N2 Agent#2 and RAN#2 before N2 Agent#2 instructs UE to initiate the connection establishment procedure to the subnet. As a result, in the subsequent connection establishment procedure between UE and subnet, RAN#2 and N2 Agent#2 do not need to establish the context of UE's N2 interface#4 again.

[0446] Optionally, RAN#2 sends a second indication message to N2 agent #2. Accordingly, N2 agent #2 receives the second indication message from RAN#2.

[0447] The second indication information is used to indicate that the UE's context should not be released. For example, the second indication information indicates that the UE's N2 context should not be released. The UE's N2 context includes identification information (e.g., NGAP pair UE ID#4) used to identify the UE on N2 interface #4. Alternatively, not releasing the UE's context may include N2 agent #2 not actively releasing the UE's N2 context. For example, if N2 agent #2 detects that the UE's AN connection with N2 agent #2 has been released, N2 agent #2 will not release the UE's N2 context.

[0448] In other words, by instructing N2 agent #2 not to actively release the UE's context, it is possible to avoid the subnet from re-entering the CM idle state due to the lack of downlink data and / or downlink signaling for the UE, which would cause unnecessary signaling overhead when the subnet re-enters the CM connected state.

[0449] It is understood that the above-mentioned second indication information is used to indicate that the N2 context of the UE is not released, and can be replaced by any of the following: the second indication information is used to indicate that the UE is not entered into an idle state; or, the second indication information is used to indicate that the UE's connection is not disconnected.

[0450] In addition, the N2 context of the UE is only an exemplary name. As the network evolves, the N2 context of the UE can be replaced with any other context that may be used to represent the interface between the UE and the subnet. This application embodiment does not specifically limit this.

[0451] It should be understood that the idle state may refer to the CM idle state, or any other name that may indicate the connection state between the UE and the network. Please refer to Figures 3 and 4 for relevant descriptions of the CM idle state. This application embodiment does not specifically limit this.

[0452] It should also be understood that the second instruction information is used to indicate that the UE connection is not interrupted. For example, it may mean that the UE and the N2 agent maintain a NAS signaling connection or that the UE's NAS context is not released, etc., without specific limitations.

[0453] Alternatively, if RAN#2 and the UE have not released the RRC connection, RAN#2 will not release the N2 context of the UE between RAN#2 and the N2 agent #2 of the subnet.

[0454] In other words, when the RRC connection between RAN#2 and UE is not released, RAN#2 can avoid unnecessary signaling overhead caused by the subnet re-entering the CM idle state due to the lack of downlink data and / or downlink signaling for the UE between RAN#2 and the subnet by not releasing the N2 context of the UE.

[0455] It is understandable that due to the UE's mobility, the UE may move outside the cell controlled by RAN#2, thereby releasing the RRC connection between RAN#2 and the UE. In the case of releasing the RRC connection between RAN#2 and the UE, RAN#2 releases the UE's N2 context, and N2 proxy #1 and N2 proxy #2 also release the UE's N2 context. This allows the main network and subnet to synchronize the UE to a CM idle state, resolving the problem of disordered UE connection states.

[0456] Furthermore, the aforementioned second instruction information and connection information can be sent together or separately, and there is no limitation on this.

[0457] It should be understood that step S1212 can be performed before or after step S1211, and the embodiments of this application do not specifically limit this.

[0458] S1213, N2 Agent #2 updates the UE's context and the identifier of the UE's serving RAN.

[0459] It is understandable that N2 agent #2 can determine the UE's SUPI based on the UE's GUTI #1, and thus identify the UE. In addition, since the UE has released the RRC connection with RAN #1, N2 agent #2 can determine that the UE's serving RAN has been updated from RAN #1 to RAN #2 (i.e., RAN #2) based on the connection information sent by RAN #2.

[0460] Additionally, N2 Agent #2 updates the UE's context, including: N2 Agent #2 updates GUTI#1 to GUTI#3.

[0461] In addition, N2 Agent #2 updates the identifier of the UE's serving RAN, including: N2 Agent #2 updates the identifier of the UE's serving RAN from the identifier of RAN #1 to the identifier of RAN #2.

[0462] It is understood that the aforementioned RAN identifier is used by the network side (e.g., N2 proxy #2) to identify the UE's serving RAN. The RAN identifier may be, for example, the NR cell global identifier (NCGI), or an identifier (or gNB ID) used by a network (e.g., PLMN) within the same domain to identify the RAN, or an identifier used to identify the RAN globally, or any other identification information that may be used by the network side to identify the RAN. This application embodiment does not specifically limit this.

[0463] In addition, when RAN#2 sends the second indication information to N2 agent#2, and the second indication information uses mode a, that is, the identification information used by the RAN side to identify the UE is the transaction identifier allocated by RAN#2, N2 agent#2 also stores the transaction identifier.

[0464] When RAN#2 sends a second indication message to N2 agent #2, and the second indication message uses method b, i.e., the identification information used by the RAN side to identify the UE is the RAN NGAP UE ID#4 assigned by the RAN side, N2 agent #2 also establishes the UE's N2 context. The establishment of the UE's N2 context by N2 agent #2 includes: N2 agent #2 storing the RAN NGAP UE ID#4 and assigning the CN-side N2 interface #4 identifier to the UE, such as CN NGAP UE ID#4.

[0465] It is understood that N2 agent #2 can store NGAP pair UE ID #4, which includes RAN NGAP UE ID #4 and CN NGAP UE ID #4.

[0466] S1214, AM#2 sends NAS message transfer #2 to N2 agent #2. Correspondingly, N2 agent #2 receives NAS message transfer #2 from AM#2.

[0467] It is understood that NAS message transmission #2 includes the UE's SUPI and the downlink data and / or downlink signaling to be transmitted to the UE by the subnet.

[0468] It should be understood that step S1214 is an optional step. N2 agent #2 can trigger N2 agent #2 to send a first message to RAN #2 based on the NAS message sent by AM #2 to instruct the UE to initiate a connection establishment procedure to the subnet, and then transmit the UE's downlink data and / or downlink signaling.

[0469] In addition, if N2 agent #2 does not receive the NAS transmission sent by AM #2, N2 agent #2 may also actively send the first message to the UE. This application embodiment does not specifically limit this.

[0470] S1215, N2 Agent #2 sends the first message to RAN #2. Correspondingly, RAN #2 receives the first message from N2 Agent #2.

[0471] It should be understood that in the embodiments of this application, the first message may have two different uses. In a first possible implementation, the first message is used to trigger the UE to initiate a connection establishment procedure to the subnet. In a second possible implementation, the first message is used to transmit downlink data and / or downlink signaling of the UE.

[0472] The first and second possible implementation methods are described below.

[0473] In the first possible implementation, the first message is used to instruct RAN#2 to send a first indication message to the UE. The first indication message is used to instruct the UE to initiate a connection establishment procedure to the subnet.

[0474] For example, the first indication information is used to indicate downlink data and / or downlink signaling to be transmitted to the UE, so that the UE can send a service request message to the subnet. As another example, the first indication information is used to instruct the UE to establish a connection with the subnet (or to instruct the UE to access the subnet), so that the UE can send a service request message to the subnet.

[0475] It should be understood that the explanation of the first instruction information can be found in step S1206 below, and will not be repeated here.

[0476] In other words, since N2 agent #2 receives connection information from RAN #2 in step S1212 (i.e., the UE is in RRC connected state), and there is downlink data and / or downlink signaling of the UE to be transmitted in the subnet, N2 agent #2 can directly send the first message to RAN #2 instead of using the paging mechanism (i.e., N2 agent #2 sends paging messages to all RANs under the TAI list registered by the UE), thereby solving the problem of disordered connection state of the UE shown in (c) of Figure 9.

[0477] In one possible implementation, the first message includes identification information used by the RAN side to identify the UE.

[0478] It is understandable that the first message includes identification information used by the RAN side to identify the UE, which enables RAN#2 to determine which UE the first message is for.

[0479] Additionally, as described in the previous step S1212, RAN#2 may send identification information for RAN-side UE identification to N2 agent#2. This identification information can be divided into two types: one is the transaction identifier in method a, and the other is RAN NGAP UE ID#4 in method b. N2 agent#2 may send the first message based on one of the methods a and b. The contents of the first message are described below based on method a and method b.

[0480] For method a:

[0481] In one possible implementation, the identification information used by the RAN side to identify the UE is a transaction identifier.

[0482] It is understandable that when the RAN subsequently receives data and / or signaling related to the UE, the RAN can identify that the received data and / or signaling is related to the UE based on the transaction identifier.

[0483] In one possible implementation, the identification information used by the RAN side to identify the UE is a transaction identifier, which is used to indicate downlink data and / or downlink signaling to be transmitted to the UE.

[0484] As can be understood, as described in step S1212 regarding the transaction identifier, the transaction identifier is used to indicate downlink data and / or downlink signaling to be transmitted to the UE. After receiving the transaction identifier, RAN#2 sends the aforementioned first indication information to the UE to instruct the UE to initiate a connection establishment process to the subnet.

[0485] It should be understood that the protocol may predefine a transaction identifier to represent downlink data and / or downlink signaling to be transmitted to the UE, or RAN#2 and N2 agent #2 may negotiate in advance that the transaction identifier represents downlink data and / or downlink signaling to be transmitted to the UE, or RAN#2 may instruct the transaction identifier to represent downlink data and / or downlink signaling to be transmitted to the UE. The embodiments of this application do not specifically limit this.

[0486] It is understandable that the aforementioned transaction identifier may only be used by RAN#2 to identify the UE. In this case, the first message should also include information to instruct RAN#2 to send the first instruction information to the UE.

[0487] Optionally, the first message may also include information for instructing RAN#2 to send first indication information to the UE.

[0488] It is understood that, unlike the aforementioned transaction identifier which is used to indicate downlink data and / or downlink signaling to be transmitted to the UE, the transaction identifier is used by RAN#2 to identify the UE.

[0489] In other words, the first message includes a transaction identifier and information instructing RAN#2 to send a first indication message to the UE, enabling RAN#2 to identify the UE and determine that the first message is addressed to the UE. Furthermore, by sending information to RAN#2 instructing RAN#2 to send the first indication message to the UE, N2 Agent #2 enables RAN#2 to send the first indication message to the UE, thereby instructing the UE to initiate a connection establishment procedure with the subnet.

[0490] Optionally, the information used to instruct RAN#2 to send the first indication information to the UE includes paging indication information and / or TMSI#2. The paging indication information and / or TMSI#2 are used by the UE to determine whether to initiate a connection establishment procedure to the subnet.

[0491] It is understood that the aforementioned paging indication information and / or TMSI#2 can be the first indication information, meaning that RAN#2 can transparently transmit the paging indication information and / or TMSI#2. For example, TMSI#2 is also used by the UE side to identify which CN is being initiated into the connection establishment process.

[0492] In addition, TMSI#2 is determined based on GUTI#2 (i.e., the temporary identifier GUTI#2 assigned to the UE by N2 agent #2 in the UE registration subnet process), which can be found in the relevant explanation in step S1206, and will not be repeated here.

[0493] In other words, N2 Proxy #2 can reuse the paging indication information and / or TMSI #2 in the CN-side paging RAN mechanism, so that the paging indication information and / or TMSI #2 are sent to the UE, enabling the UE to initiate a connection establishment process to the subnet, reducing implementation complexity and making it easier to deploy.

[0494] Method B:

[0495] It is understandable that, according to the relevant description in step S1212 regarding the identification pair for identifying the UE on N2 interface #4 (i.e., the interface between RAN #2 and N2 agent #2), this identification pair can be RAN NGAP UE ID #4. It should be understood that when RAN #2 sends RAN NGAP UE ID #4 to N2 agent #2, N2 agent #2 can assign CN NGAP UE ID #4 to the UE. This is equivalent to the UE's N2 interface #4 context being established in advance between RAN #2 and N2 agent #2 when the UE is in CM idle state on the subnet side and has not yet initiated a service request or connection establishment procedure to the subnet. In other words, the UE's N2 interface #4 context is established in advance during the process where the N2 agent #2 of the subnet triggers the UE to initiate a connection establishment procedure to the subnet through RAN #2.

[0496] In one possible implementation, the identification information used by the RAN side to identify the UE is an identification pair used to identify the UE on N2 interface #4 (i.e., the interface between RAN #2 and N2 agent #2).

[0497] In other words, the N2 agent #2 sends an identifier pair to RAN #2 to identify the UE on the N2 interface #4, enabling RAN #2 to determine the UE's context information and identify the UE.

[0498] It should be understood that, when the identification information used for RAN-side UE identification is an identification pair used to identify the UE on N2 interface #4, similar to method a, the first message may also include paging indication information and / or TMSI #2. Optionally, the second indication information includes paging indication information and / or TMSI #2.

[0499] In other words, when N2 Agent #2 sends an identification pair (i.e., NGAP pair UE ID#4) to RAN #2 to identify the UE on N2 interface #4, N2 Agent #2 can also send paging indication information and / or TMSI#2 to RAN #2, so that RAN #2 sends the first indication information to the UE, thereby instructing the UE to initiate a connection establishment procedure to the subnet.

[0500] In addition, since NGAP pair UE ID#4 has been established between N2 Agent #2 and RAN #2 in advance, NGAP pair UE ID#4 does not need to be established again between N2 Agent #2 and RAN #2 in the subsequent connection establishment process initiated by the UE to the subnet, thus saving signaling overhead.

[0501] It is understood that the above-mentioned N2 agent #2 sends NGAP pair UE ID#4, paging indication information and / or TMSI#2 to RAN#2, and the subsequent UE initiates the connection establishment process to the subnet. Please refer to steps S1315 to S1320 in Figure 13 below, which will not be elaborated here.

[0502] It should be understood that, considering that in method b, the UE's N2 interface #4 context is pre-established between RAN#2 and N2 agent #2, N2 agent #2 can directly send the UE's downlink data and / or downlink signaling to RAN#2, and RAN#2 can send the UE's downlink data and / or downlink signaling to the UE through the RRC connection between RAN#2 and the UE. In other words, the first message in step S1215 may include the UE's downlink data and / or downlink signaling.

[0503] In the second possible implementation, the first message includes an identifier pair that identifies the UE on the N2 interface #4, as well as the UE's downlink data and / or downlink signaling.

[0504] In other words, by sending the UE identifier pair on the N2 interface #4, along with the UE's downlink data and / or downlink signaling, to RAN #2, N2 proxy #2 enables RAN #2 to identify the UE using the UE identifier pair. Then, through the RRC connection (or radio bearer) between RAN #2 and the UE, RAN #2 can directly send the UE's downlink data and / or downlink signaling to the UE. This eliminates the need for the UE to initiate a connection establishment process with the subnet, thus simplifying the connection establishment process, saving signaling overhead, and improving efficiency.

[0505] It should be understood that in the second possible implementation, unlike the N2 agent #1 of the main network assigning a new temporary identifier GUTI#3 to the UE in step S1210, the N2 agent #2 may not need to assign a new temporary identifier GUTI to the UE, and may continue to use the GUTI#2 assigned by the subnet before the UE entered the idle state (i.e., GUTI#2 in step S1115). In other words, in the second possible implementation, the subnet and the UE can reuse the UE's context established when the connection was previously established, such as the UE's SUPI, GUTI#2, TMSI#2, or security context, to ensure the transmission of data and / or signaling between the UE and the subnet.

[0506] Alternatively, in the second possible implementation, after step S1215, RAN#2 sends downlink data and / or downlink signaling to the UE.

[0507] It is understood that RAN#2 can send downlink data and / or downlink signaling to be transmitted to the UE through the RRC connection between RAN#2 and the UE. For example, RAN#2 sends downlink data and / or downlink signaling to the UE, and indicates that the downlink data and / or downlink signaling comes from the subnet, or indicates that the UE has established a connection with the subnet, or that the UE is in CM connected state on the subnet side.

[0508] In addition, the indication that the downlink data and / or downlink signaling comes from the subnet can be indicated by the subnet's identifier and / or the identifier information (e.g., TMSI#2 or GUTI#2) assigned to the UE by the subnet. This application embodiment does not specifically limit this.

[0509] It is understood that the subnet identifier can be found in step S1001 of Figure 10 above, and will not be repeated here. In addition, the identifier information assigned to the UE by the subnet can be, for example, GUTI#2 or TMSI#2, etc., which is not limited.

[0510] Example 1: RAN#2 sends the subnet identifier, downlink data and / or downlink signaling to the UE.

[0511] Example 2: RAN#2 sends GUTI#2, along with downlink data and / or downlink signaling, to the UE.

[0512] Example 3: RAN#2 sends TMSI#2, along with downlink data and / or downlink signaling, to the UE.

[0513] It is understandable that if the subnet identifier cannot be derived from GUTI#2, or if GUTI#2 is the same as a temporary identifier assigned by other networks (e.g., GUTI#3 assigned by the main network), in order to avoid the UE being unable to identify which network the downlink data and / or downlink signaling sent by RAN#2 belongs to, Example 1, or a combination of Example 1 and Example 2 (or Example 3) can be used.

[0514] In addition, upon receiving the first indication information, the UE can determine that the UE and the subnet are in a connected state (or, in other words, that the UE is in a CM connected state on the subnet side).

[0515] It is understood that the subnet identifier and / or the identification information assigned to the UE by the subnet, as well as the downlink data and / or downlink signaling, can be sent separately or together, without limitation. For example, RAN#2 can first send the subnet identifier and / or the identification information assigned to the UE by the subnet, and then send the downlink data and / or downlink signaling to the UE; or, RAN#2 can first send the downlink data and / or downlink signaling to the UE, and then send the subnet identifier and / or the identification information assigned to the UE by the subnet.

[0516] The above describes the steps performed by RAN#2 after step S1215 in the second implementation method. The following describes the steps after step S1215 in the first implementation method.

[0517] S1216, RAN#2 sends a first indication message to the UE. Correspondingly, the UE receives the first indication message from RAN#2.

[0518] It is understood that, as described in step S1215, the first indication information is used to instruct the UE to initiate a connection establishment process to the subnet.

[0519] Optionally, the first instruction information instructs the UE to initiate a service request to the subnet, or instructs the UE to establish a connection with the subnet.

[0520] It is understood that the first indication information instructs the UE to establish a connection with the subnet, which can be replaced with: the first indication information instructs the UE to access the subnet, or the first indication information instructs the UE to connect to the subnet, etc., without limitation.

[0521] In addition, regarding the first instruction information instructing the UE to initiate a service request to the subnet, according to the relevant description of the UE sending a service request in S208 of Figure 2, after the UE completes registration, it will store the RM state of the UE's registered subnet. Therefore, after the UE receives the first instruction information, it can send a service request to RAN#2.

[0522] Furthermore, regarding the first indication information instructing the UE to establish a connection with the subnet, and referring to the relevant explanations of the CM connection state in Figures 3 and 4, the UE can send an initial NAS message to N2 agent #2 via RAN#2 to establish a connection between the UE and the subnet. The initial NAS message includes a service request.

[0523] In other words, RAN#2 can directly instruct the UE to send a service request message to the subnet or initiate a connection establishment process through the first indication information.

[0524] Optionally, the first indication information is TMSI#2, which is used to instruct the UE to send a service request message to the subnet or to initiate a connection establishment process.

[0525] As can be understood, as described in the aforementioned step S1215, N2 agent #2 sends TMSI #2 to RAN #2, and RAN #2 is then able to send TMSI #2 to UE to instruct UE to initiate a connection establishment procedure to the subnet.

[0526] Additionally, RAN#2 can send the first indication information via the RRC connection between RAN#2 and the UE. For example, RAN#2 sends an AS message to the UE, which includes the first indication information.

[0527] For ease of understanding, the following explanation will use the aforementioned step S1212 in mode a and the UE sending a service request message to the subnet as an example to illustrate the subsequent steps.

[0528] S1217, UE sends Service Request Message #2 to RAN#2. Correspondingly, RAN#2 receives Service Request Message #2 from UE.

[0529] It is understood that the service request message #2 may include GUTI#2, which is similar to the UE sending the service request message #1 to RAN#2 in the aforementioned step S1208, and will not be described again here.

[0530] S1218, RAN#2 sends RAN NGAP UE ID#4 and service request message#2 to N2 agent#2. Correspondingly, N2 agent#2 receives RAN NGAP UE ID#4 and service request message#2 from RAN#2.

[0531] It is understandable that, according to the relevant description of step S1212 above, when RAN#2 adopts mode a, RAN#2 should send a transaction identifier to N2 agent #2 instead of RAN NGAP UE ID#4. Therefore, in step S1218, RAN#2 sends RAN NGAP UE ID#4 to N2 agent #2 to establish the N2 interface #4 context of the UE.

[0532] In addition, RAN#2 transmits service request message #2.

[0533] S1219, N2 Agent #2 sends NGAP pair UE ID #4 and temporary identification information assigned to the UE by the subnet to RAN #2. Correspondingly, RAN #2 receives NGAP pair UE ID #4 and temporary identification information assigned to the UE by the subnet from N2 Agent #2.

[0534] Optionally, N2 Agent #2 sends the identifier of N2 Agent #1 of the main network to RAN #2. Correspondingly, RAN #2 receives the identifier of N2 Agent #1 of the main network from N2 Agent #2.

[0535] It is understood that NGAP pair UE ID#4 can be found in the aforementioned step S1212, and will not be repeated here.

[0536] Furthermore, unlike method b described above, step S1219 is triggered by the UE sending service request message #2. Therefore, N2 agent #2 receives the UE's service request message #2 and allocates a new temporary identifier GUTI#4 to the UE. This allows the UE to update its original GUTI#2 to GUTI#4 and use GUTI#4 to interact with the subnet. It should be understood that the purpose of N2 agent #2 sending the temporary identifier information allocated by the subnet to RAN#2 is to instruct the UE when RAN#2 sends UE information to N2 agent #1 of the main network.

[0537] Optionally, the temporary identification information allocated by the subnet to the UE includes GUTI#2 and GUTI#4. GUTI#2 is the GUTI previously allocated to the UE by the subnet. RAN#2 can send GUTI#2 and GUTI#4 to N1 agent #1 of the main network. N2 agent #1 of the main network can detect the UE's context based on GUTI#2 to determine the UE's SUPI and thus identify the UE. In addition, N2 agent #1 of the main network can update GUTI#2 to GUTI#4 to facilitate subsequent identification of information about the UE sent by the subnet.

[0538] It is understandable that the identifier of N2 Agent #1 in the large network is used by RAN #2 to determine the address for RAN #2 to interact with N2 Agent #1 in order to send UE information to N2 Agent #1.

[0539] In another implementation, the RAN stores information about the N2 agent of the main network to which the UE is connected, and determines the N2 agent #1 of the main network based on this information.

[0540] In addition, the identifier of the N2 agent #1 of the main network is also used to instruct RAN #2 to send the temporary identifier information allocated by the subnet to the UE and / or the connection information of the UE on the subnet side to the N2 agent #1 of the main network.

[0541] Optionally, N2 agent #2 sends instruction information #3 to RAN #2. Instruction information #3 is used to instruct RAN #2 to send the temporary identification information allocated by the subnet to the UE and / or the connection information of the UE on the subnet side to N2 agent #1 of the main network.

[0542] It is understood that the protocol can predefine that N2 agent #2 sends the identifier of the N2 agent #1 of the main network to RAN #2, that is, instructs RAN #2 to send UE information to the N2 agent #1 of the main network. In addition, the above-mentioned N2 agent #2 sending the identifier of the N2 agent #1 of the main network to RAN #2 to instruct RAN #2 to send UE information to the N2 agent #1 of the subnet can also be negotiated in advance between N2 agent #2 and RAN #2; or the protocol can predefine that when RAN receives UE information sent by the N2 agent #2 of the subnet, it will send the UE information to the N2 agent #1 of the main network corresponding to the UE. This application embodiment does not specifically limit this.

[0543] It is understood that N2 agent #2 obtains the identifier of N2 agent #1, which can be determined based on GUTI #3. Alternatively, if GUTI #3 cannot determine the identifier of N2 agent #1, N2 agent #2 can also store the identifier information of N2 agent #1 sent by RAN #1 to determine the identifier of N2 agent #1. The relevant implementation methods can be found in the relevant description of step S1111 in Figure 11 above, and will not be repeated here.

[0544] The subsequent connection establishment process is completed between S1220, UE, RAN#2, N2 agent#2, AM#2, and MM#2.

[0545] It is understood that in or after step S1219, N2 agent #2 should send a service response message to RAN #2, which includes GUTI#4. RAN #2 can pass the service response message through to the UE so that the UE can update GUTI#4 to the UE's context.

[0546] In addition, the UE establishes a session through interactions with RAN#2, N2 Agent #2, AM#2, and MM#2. The UE session can be used by the UE to receive downlink data to be transmitted to the UE from the subnet.

[0547] S1221, RAN#2 sends the temporary identification information allocated by the subnet to the UE to N2 Agent #1. Correspondingly, N2 Agent #1 receives the temporary identification information allocated by the subnet to the UE from RAN#2.

[0548] It is understood that the temporary identifiers assigned to the UE by the subnet include GUTI#2 and GUTI#4. N2 Agent #1 can retrieve the UE's SUPI based on GUTI#2 to obtain the UE's context and thus identify the UE. N2 Agent #1 can update the UE's context based on GUTI#4 to facilitate subsequent reception of information about the UE sent by the subnet.

[0549] It should be understood that step S1221 is illustrated by taking the example of RAN#2 sending the temporary identifier assigned to the UE by the subnet to N2 agent #1. RAN#2 can also send the connection status of the UE on the subnet side to N2 agent #2, which is not limited.

[0550] In addition, step S1221 can be executed before or after step S1220, and this application embodiment does not specifically limit this.

[0551] In this embodiment of the application, when the UE releases the RRC connection with RAN#1, causing RAN#1 to release the UE's N2 context with the main network, and RAN#2 to release the UE's N2 context with the subnet, if the UE responds to the paging of the main network and establishes a connection with the main network through RAN#2, then the main network can instruct RAN#2 to send the UE's connection information on the main network side to the N2 agent #2 of the subnet, such as the UE establishing an RRC connection with RAN#2. Then, when the subnet expects to establish a connection with the UE, the subnet establishes a connection with the UE through RAN#2, thereby solving the problem of disordered connection status of the UE.

[0552] For example, when the subnet carries downlink data and / or downlink signaling to be transmitted to the UE, N2 Agent #2, based on the UE's connection information on the main network side, can determine to send a first message to RAN #2 to trigger the UE to initiate a connection establishment procedure to the subnet through RAN #2, instead of using a paging mechanism (i.e., N2 Agent #2 sends paging messages to all RANs under the UE's registered TAI list), thereby resolving the problem of disordered UE connection state. The problem of disordered UE connection state can occur, for example, when the UE has already established an RRC connection with RAN #2, and N2 Agent #2 sends paging indications to multiple RANs, causing the UE to detect paging messages from the subnet paging message from multiple RANs. This causes the UE to release its RRC connection with RAN #2 and establish RRC connections with other RANs, thus changing the UE's connection state on the main network side from connected to idle.

[0553] In addition, RAN#2 sends identification information (such as transaction identifier or RAN NGAP UE ID#4) to N2 agent #2 of the subnet for RAN-side identification of the UE. The first message includes this identification information, so that RAN#2 recognizes that the first message is for the UE. RAN#2 can directly send the first indication information to the UE through the RRC connection to instruct the UE to initiate a connection establishment procedure to the subnet. This avoids RAN#2 paging the UE on the air interface, thus preventing the problem that the UE will not respond to the paging of the subnet after establishing a connection with the main network through RAN#2, which would otherwise lead to the UE establishing a connection with the subnet.

[0554] Furthermore, the identification information used by the RAN side to identify the UE includes RAN NGAP UE ID#4. This RAN NGAP UE ID#4 can trigger N2 agent #2 to allocate CN NGAP UE ID#4 to the UE. Then, when the subnet wants to establish a connection with the UE, the first message sent by N2 agent #2 to RAN #2 includes NGAP pair UE ID#4 composed of RAN NGAP UE ID#4 and CN NGAP UE ID#4. This is equivalent to establishing the context of the UE's N2 interface #4 (e.g., including NGAP pair UE ID#4) between N2 agent #2 and RAN #2 in advance.

[0555] Furthermore, the first message may not be used to instruct the UE to initiate a connection establishment procedure with the subnet. Instead, it may instruct RAN#2 to directly send the downlink data and / or downlink signaling to be transmitted to the UE. For example, the first message may include the NGAP pair UE ID#4 and the downlink data and / or downlink signaling to be transmitted to the UE. RAN#2 identifies the UE based on the NGAP pair UE ID#4 and, through the RRC connection (or radio bearer) between RAN#2 and the UE, directly sends the downlink data and / or downlink signaling to be transmitted from the subnet to the UE. This allows the UE to re-establish a connection with the subnet without triggering the connection establishment procedure initiated by the UE with the subnet, simplifying the connection establishment process between the UE and the subnet, saving signaling overhead, and improving efficiency.

[0556] Option 1-2

[0557] The difference between Scheme 1-1 and Scheme 1-2 is that there is an interactive interface between the first network and the second network, allowing the two networks to exchange terminal connection information without requiring the RAN (e.g., RAN#2 in Figure 12) to connect the terminals between them, thus overcoming the problem described in Figure 9. Furthermore, since the first network and the second network can interact directly, the UE can be identified through the terminal's SUPI. Therefore, Scheme 1-2 does not limit the first network to storing the identification information assigned to the terminal by the second network, nor does it limit the second network to storing the identification information assigned to the terminal by the first network.

[0558] Figure 13 is a schematic flowchart of a communication method provided in an embodiment of this application. As shown in Figure 13, the flowchart includes steps S1301 to S1320.

[0559] S1301 and UE establish connections with the main network and subnet respectively.

[0560] It is understood that the implementation of step S1301 can be referred to the process shown in Figure 11 or Figure 10, and will not be repeated here.

[0561] S1302, Release the AN connection between UE and RAN#1.

[0562] It is understood that the implementation of step S1302 can be referred to step S1202.

[0563] S1303, release the N2 context of the UE between RAN#1 and N2 agent #1.

[0564] It is understood that the implementation of step S1303 can be found in step S1203.

[0565] S1304, Release the N2 context of the UE between RAN#1 and N2 agent #2.

[0566] It is understood that the implementation of step S1304 can be found in step S1204.

[0567] S1305, AM#1 sends NAS message transmission #1 to N2 agent #1. Correspondingly, N2 agent #2 receives NAS message transmission #1 from AM#1.

[0568] It is understood that the implementation of step S1305 can refer to step S1205.

[0569] S1306, N2 Agent #1 sends a paging message to RAN #2. RAN #2 receives the paging message from N2 Agent #1.

[0570] It is understood that the implementation of step S1306 can refer to step S1206.

[0571] S1307, RAN#2 broadcasts a paging message. Correspondingly, the UE receives the paging message from RAN#2.

[0572] It is understood that the implementation of step S1307 can be found in step S1207.

[0573] S1308, UE sends Service Request Message #1 to RAN#2. Correspondingly, RAN#2 receives Service Request Message #1 from UE.

[0574] Among them, the service request message #1 includes the GUTI#1 corresponding to TMSI#1.

[0575] Furthermore, the difference between step S1308 and step S1208 is that the service request message #1 in step S1308 is forwarded by RAN#2 to N2 agent #1 (step S1309) so that N2 agent #1 sends the UE's connection information to N2 agent #2 of the subnet (see step S1312), instead of N2 agent #1 sending the identifier of N2 agent #2 and the temporary identifier information allocated by the main network to the UE to RAN#2 (see step S1210), so that RAN#2 can send the UE's connection information to N2 agent #2 (see step S1211).

[0576] Optionally, the business request message #1 may also include GUTI#2.

[0577] It is understandable that if N2 agent #1 does not store GUTI#2 (i.e., does not use the registration process shown in Figure 11), the GUTI#2 carried by the service request message #1 can enable N2 agent #1 of the main network to obtain GUTI#2, so as to send the UE's connection information to N2 agent #2 of the subnet in subsequent steps.

[0578] S1309, RAN#2 sends RAN NGAP UE ID#3 and service request message#1 to N2 agent#1. Correspondingly, N2 agent#1 receives RAN NGAP UE ID#3 and service request message#1 from RAN#2.

[0579] It is understood that RAN NGAP UE ID#3 can be found in step S1209, and will not be repeated here.

[0580] Additionally, N2 agent #1 can obtain the GUTI #2 allocated to the UE by the subnet. For example, according to the process shown in Figure 11, N2 agent #1 can store GUTI #2. As another example, in step S1308, the service request message #1 includes GUTI #2, thus enabling N2 agent #1 to obtain GUTI #2.

[0581] S1310, N2 Agent #1 sends NGAP pair UE ID #3 to RAN #2. Correspondingly, RAN #2 receives NGAP pair UE ID #3 from N2 Agent #1.

[0582] It is understandable that the difference between step S1310 and step S1210 is that, since there is an interface for interaction between the main network and the subnet, N2 agent #1 can send the UE's connection information to N2 agent #2. Therefore, in step S1310, N2 agent #1 only needs to send NGAP pair UE ID #3 to RAN #2 to complete the establishment of the UE's N2 interface #3 context. It is not necessary for N2 agent #1 to send indication information #2 to RAN #2 (i.e., RAN #2 sends the UE's connection information to N2 agent #2 in step S1211), as well as the temporary identifiers (such as GUTI #1 and GUTI #3) allocated by the main network to the UE.

[0583] Additionally, NGAP pair UE ID#3 can be found in step S1210, and will not be repeated here.

[0584] The subsequent connection establishment process is completed between S1311, UE, RAN#2, N2 agent#1, AM#1, and MM#1.

[0585] It is understood that step S1311 is the same as step S1211, and will not be repeated here.

[0586] S1312, N2 Agent #1 sends connection information and the UE's serving RAN information to N2 Agent #2. Correspondingly, N2 Agent #2 receives the connection information from N2 Agent #1.

[0587] It is understandable that the difference between step S1312 and step S1212 is that in step S1312, the connection information is used to indicate that the UE has established a connection with the main network through RAN#2. That is, relative to the connection information in S1212, in step S1312, N2 agent #1 also sends relevant information of the UE's current serving RAN (i.e. RAN#2) to N2 agent #2. In this way, N2 agent #2 can determine which RAN the UE established an RRC connection with after releasing the RRC connection with RAN#1.

[0588] Optionally, the connection information is used to indicate whether the UE enters the CM connection state or the RRC connection state. The UE entering the CM connection state can be replaced with: the UE is in the CM connection state, or the UE is in the CM connection state on the main network side, or the UE has established a connection with the main network, or the UE has established a connection with the main network, etc., without limitation.

[0589] It is understandable that, based on the connection information sent by N2 Agent #1, N2 Agent #2 can determine that the network where N2 Agent #1 is located is the large network, and thus determine that the UE enters the CM connection state on the large network side.

[0590] In addition, the UE entering the RRC connection state can be replaced by: the UE being in the RRC connection state, or the UE being in the RRC connection state on the main network side, or the UE establishing a connection with the RAN, or the UE establishing a connection with the main network through the RAN, etc., without any limitation.

[0591] It should be understood that the identifier of the UE's serving RAN can be found in step S1213, and will not be repeated here.

[0592] Alternatively, the connection information may be used to indicate that the UE is entering the RRC connection state. It is understood that the connection information is used to indicate that the UE is entering the RRC connection state; see the description of step S1212 for details, which will not be repeated here.

[0593] In other words, based on the connection information from N2 Agent #1 and the information of the UE's serving RAN, N2 Agent #2 can determine that an RRC connection has been established between the UE and RAN #2, or that the UE has established a connection with the main network through RAN #2. Thus, information can be transmitted between the UE and RAN #2 without sending paging messages to all RANs under the UE's registered TAI list, thereby solving the problem of disordered connection status of the UE shown in Figure 9(c).

[0594] Optionally, the connection information includes the UE's identification information, as well as CM connection state and / or RRC connection state indication information. The CM connection state indication information is used to indicate that the UE corresponding to the UE's identification information is in the CM connection state.

[0595] Optionally, the UE's identification information includes the UE's SUPI. It can be understood that, according to the registration process shown in Figure 10 or Figure 11 above, the UE's SUPI is stored on the CN side (e.g., the main network or subnet). Therefore, by sending the UE's SUPI to N2 Agent #1, N2 Agent #2 can identify the UE.

[0596] It is understandable that, considering that no N2 context of the UE is established between N2 Agent #2 and RAN #2, that is, there is no identification pair (i.e., NGAP pair UE ID) between N2 Agent #2 and RAN #2 to identify the UE on N2 interface #4 (i.e., the interface between RAN #2 and N2 Agent #2), there will be no identification information between N2 Agent #2 and RAN #2 to identify the UE. As a result, RAN #2 cannot identify which UE to send information to, and thus broadcasts a paging message for the UE.

[0597] In addition, considering that the difference between steps S1312 and S1212 is that N2 agent #2 receives connection information from N2 agent #1 instead of RAN #2, the identification information used to identify the UE on N2 interface #4 in step S1212 is replaced by reusing the NGAP pair UE ID between N2 agent #1 and RAN #2.

[0598] Optionally, the UE identification information also includes identification information used to identify the UE on N2 interface #3 (i.e., the interface between RAN #2 and N2 agent #1).

[0599] It is understood that the identification information used to identify the UE on the N2 interface #3 can be the NGAP pair UE ID#3 of the UE on the main network side. The NGAP pair UE ID#3 can be found in step S1210, and will not be described again here.

[0600] In other words, when N2 Agent #1 sends identification information to N2 Agent #2 to identify the UE on N2 Interface #3, N2 Agent #2 can reuse the context of N2 Interface #3 between N2 Agent #1 and RAN #2, so that RAN #2 can identify the UE, thereby avoiding RAN #2 paging the UE on the air interface and avoiding the problem that the UE will not respond to the paging of the subnet.

[0601] It should be understood that step S1312 can be performed before or after step S1311, and the embodiments of this application do not specifically limit this.

[0602] S1313, N2 Agent #2 updates the UE's context and the UE's serving RAN identifier.

[0603] It is understandable that the difference between step S1313 and step S1213 is that N2 agent #2 can identify the UE based on the UE's SUPI, and then update the UE's context and the identifier of the UE's serving RAN, which will not be elaborated here.

[0604] S1314, AM#2 sends NAS message transmission #2 to N2 agent #2. Correspondingly, N2 agent #2 receives NAS message transmission #2 from AM#2.

[0605] It is understood that steps S1314 are the same as steps S1214, and will not be repeated here.

[0606] S1315, N2 Agent #2 sends the first message to RAN #2. Correspondingly, RAN #2 receives the first message from N2 Agent #2.

[0607] It should be understood that the implementation of step S1315 is similar to that of step S1215, with the main difference being that: in the first possible implementation, the first message includes identification information for the RAN side to identify the UE, which is the identification information for identifying the UE on the N2 interface #3 in step S1312, namely NGAP pair UE ID#3.

[0608] For example, in step S1315, the first message includes NGAP pair UE ID#3, paging indication information and / or TMSI#2. NGAP pair UE ID#3 is used by RAN#2 to identify the UE, and paging indication information and / or TMSI#2 instruct RAN#2 to send the first indication information to the UE.

[0609] It is understandable that the implementation of step S1315 can be found in S1215, and will not be repeated here.

[0610] S1316, RAN#2 sends a first indication message to the UE. Correspondingly, the UE receives the first indication message from RAN#2.

[0611] It is understood that the implementation of step S1316 can be found in step S1216, and will not be repeated here.

[0612] S1317, UE sends Service Request Message #2 to RAN#2. Correspondingly, RAN#2 receives Service Request Message #2 from UE.

[0613] It should be understood that the implementation of step S1317 can be found in step S1217, and will not be repeated here.

[0614] S1318, RAN#2 sends RAN NGAP UE ID#4 and service request message#2 to N2 agent#2. Correspondingly, N2 agent#2 receives RAN NGAP UE ID#4 and service request message#2 from RAN#2.

[0615] It is understood that since the interaction between RAN#2 and N2 agent #2 in the aforementioned steps only reuses the NGAP pair UE ID#3 between RAN#2 and the main network, RAN#2 should send RAN NGAP UE ID#4 to N2 agent #2 in step S1318 in order to establish the NGAP pair UE ID#4 between RAN#2 and N2 agent #2. The relevant implementation can be found in step S1218, which will not be repeated here.

[0616] S1319, N2 Agent #2 sends NGAP pair UE ID #4 to RAN #2. Correspondingly, N2 Agent #2 receives NGAP pair UE ID #4 from N2 Agent #2.

[0617] It is understood that step S1319 is different from the aforementioned step S1219. The main difference is that since the main network and the sub-network do not need to interact through RAN#2, it is not necessary to send indication information #3 to RAN#2 and temporary identification information allocated by the sub-network to the UE.

[0618] Optionally, N2 agent #2 can assign a new temporary identifier (i.e., GUTI#4) to the UE so that the UE can update the original GUTI#2 to GUTI#4 and use GUTI#4 to interact with the subnet.

[0619] For example, in step S1320, the subnet can send a service request response message #2 to the UE via RAN#2, which includes GUTI#4.

[0620] It should be understood that in step S1319, N2 agent #2 may not allocate a new GUTI#4 to the UE, but instead it may be allocated by AM#2 in step S1320. This application embodiment does not specifically limit this.

[0621] The subsequent connection establishment process is completed between S1320, UE, RAN#2, N2 agent#2, AM#2, and MM#2.

[0622] It is understood that the implementation of step S1320 can be found in step S1220, and will not be repeated here.

[0623] In this embodiment of the application, when the UE releases the RRC connection with RAN#1, causing RAN#1 to release the UE's N2 context with the main network, and RAN#2 to release the UE's N2 context with the subnet, if the UE responds to the paging of the main network and establishes a connection with the main network through RAN#2, then the main network sends the UE's connection information on the main network side to the N2 agent #2 according to the GUTI#1 assigned to the UE by the subnet or the identifier of the N2 agent #2 of the subnet. For example, if the UE establishes a connection with the main network through RAN#2, then when the subnet paging the UE, the subnet establishes a connection with the UE through RAN#2, thereby solving the problem of disordered connection status of the UE.

[0624] For example, in the case of a UE being paged by a subnet, N2 Agent #2, based on the UE's connection information on the main network side, can determine to send a first message to RAN #2 to trigger the UE to initiate a connection establishment procedure to the subnet through RAN #2, instead of using the paging mechanism (i.e., N2 Agent #2 sends paging messages to all RANs under the UE's registered TAI list), thus resolving the problem of UE connection state disorder. UE connection state disorder can occur, for example, if the UE has already established an RRC connection with RAN #2, and N2 Agent #2 sends paging indications to multiple RANs, causing the UE to detect paging messages from the subnet in multiple RANs, leading the UE to release its RRC connection with RAN #2 to establish RRC connections with other RANs, thereby changing the UE's connection state on the main network side from connected to idle.

[0625] The following describes Scheme 1 provided in the embodiments of this application, in conjunction with Scheme 1-1 and Scheme 1-2 above.

[0626] Figure 14 is a schematic flowchart of a communication method provided in an embodiment of this application. As shown in Figure 14, the process involves the first network function of the first network, the first access network device, and the interaction between the second network, including steps S1401 to S1402.

[0627] S1401, The first network function obtains the connection information between the terminal and the second network.

[0628] The connection information indicates whether a connection exists between the terminal and the second network. The first network and the second network serve the terminal.

[0629] It should be understood that "first network" and "second network" serving the terminal means either that the terminal registers with both the first and second networks, or that the terminal accesses both networks separately. Furthermore, "first network" and "second network" serving the terminal can mean that the first and second networks serve the terminal separately, or that both networks serve the terminal simultaneously; there is no limitation on this.

[0630] Additionally, for information on the first and second networks, please refer to the relevant explanations in Figure 8, which will not be repeated here.

[0631] It can be understood that whether a terminal is connected to the second network refers to whether the terminal's connection status on the second network is connected. For example, if the terminal is not connected to the second network, it means the terminal is in an idle state on the second network. It can be understood that if the terminal is in an idle state on the second network, then the terminal is in a CM idle state on the second network. Furthermore, the terminal being in a CM idle state on the second network can also be understood as the terminal being in an RRC idle state.

[0632] For example, if the terminal is connected to the second network, meaning the terminal is in a connected state on the second network, or in other words, in a CM connected state on the second network. Alternatively, if the terminal is in a CM idle state on the second network, it can also be understood as the terminal being in an RRC connected state.

[0633] S1402. If the first network intends to establish a connection with the terminal, and the terminal does not have a connection with the second network, the first network function pages the terminal; if the terminal has a connection with the second network, the first network function establishes a connection corresponding to the terminal with the first access network device. The terminal establishes a connection with the second network through the first access network device.

[0634] It is understood that the first network function establishes a connection with the first access network device corresponding to the terminal. The connection corresponding to the terminal may refer to the aforementioned N2 connection, which will not be elaborated further.

[0635] Additionally, the scenario where the first network expects to establish a connection with the terminal can refer to a situation where the terminal is not connected to the first network (or the terminal is in an idle or disconnected state in the first network), and the first network has data and / or signaling to transmit to the terminal. For example, the terminal not being connected to the first network may include situations where the terminal has registered with both the first and second networks through a second access network device, but the terminal has released its RRC connection with the second access network device, and the terminal is in an RRC idle state.

[0636] It is understandable that, when the first network expects to establish a connection with the terminal, the first network function determines the paging terminal based on the fact that the terminal does not have a connection with the second network, and then executes the paging procedure. Conversely, when the first network expects to establish a connection with the terminal, the first network function determines to establish a connection with the terminal through the terminal's current serving access network device (i.e., the first access network device) based on the fact that the terminal has a connection with the first access network device; that is, the first network function establishes a connection corresponding to the terminal with the first access network device.

[0637] It should be understood that the above-mentioned situation where the first network expects to establish a connection with the terminal can also be understood as: the situation where the first network expects to page the terminal. In this case, the first network function determines to execute the paging process based on the fact that the terminal does not have a connection with the second network; the first network function determines to establish a connection corresponding to the terminal with the first access network device based on the fact that the terminal has a connection with the second network.

[0638] In addition, the first access network device and the second access network device mentioned above are only logically distinguished from the access network device before the terminal is in the idle state and the access network device when the terminal re-enters the RRC connection state. Please refer to the relevant explanations about RAN#1 and RAN#2 in the aforementioned step S1201, which will not be repeated here.

[0639] Steps S1401 and S1402 are described in detail below.

[0640] It should be understood that the first network function can obtain connection information from the first access network device or from the second network function of the second network.

[0641] The following sections first describe how the first network function obtains connection information from the first access network device, and then describe how the second network function obtains connection information.

[0642] A. The first network function obtains connection information from the first access network device.

[0643] It should be understood that the information acquisition or identification mentioned below in the embodiments of this application may refer to the other party actively sending information or identification, or it may refer to requesting the other party to send information or identification through a request message-response message mechanism. This will be explained uniformly here and will not be repeated below.

[0644] In addition, the terminal context mentioned below is only an exemplary name. As technology evolves, other names may be used, which is not limited here. This will be stated uniformly here and will not be repeated below.

[0645] In one possible implementation, the first access network device obtains an identifier for a first network function and, based on that identifier, sends connection information between the terminal and the second network to the first network function. Correspondingly, the first network function receives the connection information from the first access network device. This connection information indicates whether a connection exists between the terminal and the second network.

[0646] In other words, the first access network device obtains the identifier of the first network function, and then sends the connection information between the terminal and the second network to the first network function according to the identifier of the first network function, so that the first network function can obtain the connection status of the terminal in the second network. Thus, when the first network wants to establish a connection with the terminal, it determines the paging terminal or establishes a connection with the terminal corresponding to the first access network device according to the connection information, thereby realizing the collaborative management of the connection status of the terminal by the first network and the second network.

[0647] It is understandable that the first access network device can communicate with the first network function based on the identifier of the first network function.

[0648] Optionally, the identifier of the first network function can also be used to instruct the first access network device to send connection information to the first network function.

[0649] It is understood that the identifier of the first network function can be found in the relevant description in step S1210, and will not be repeated here.

[0650] Alternatively, the first access network device may acquire third indication information, which instructs the first network function to send connection information.

[0651] It is understood that the third instruction information may be sent from the second network to the first access network device during the process of the terminal establishing a connection with the second network through the first access network device, or it may be sent from the second network to the first access network device after the terminal has established a connection with the second network through the first access network device. For details, please refer to the relevant description in step S1210, which will not be repeated here.

[0652] In other words, by obtaining the third indication information, the first access network device can determine to send the connection information between the terminal and the second network to the first network function, so that the first network function can know the connection status between the terminal and the second network, so as to coordinate the management of the terminal's connection status and solve the problem of disordered terminal connection status.

[0653] In one possible implementation, the first access network device sends connection information between the terminal and the second network to the first network function based on the identifier of the first network function. This includes: if the second network establishes a connection with the terminal through the first access network device, the first access network device sends connection information to the first network function based on the identifier of the first network function. This connection information indicates that a connection exists between the terminal and the second network.

[0654] In other words, when the second network establishes a connection with the terminal through the first access network device, the first access network device sends connection information to the first network function indicating that the terminal is connected to the second network. This allows the first network function to determine that the terminal has re-entered the connection state. Consequently, when the first network expects to establish a connection with the terminal, the first network function does not page the terminal but instead establishes a connection corresponding to the terminal with the first access network device. This solves the problem of connection state disorder caused by the terminal switching its current serving access network device due to the first network sending paging messages to all access network devices in the terminal's registered TAI list.

[0655] It can be understood that establishing a connection between the second network and the terminal through the first access network device can refer to the second network paging the terminal, and the terminal sending a service request message to the second network through the first access network device, thereby establishing a connection. Furthermore, the first access network device can send connection information to the first network function during or after the connection is established between the second network and the terminal; see the relevant explanation of step S1212 above, which will not be repeated here.

[0656] Alternatively, the first access network device may also send connection information to the first network function when the terminal disconnects from the first access network device (or releases the RRC connection, or AN signal), indicating that the terminal has no connection with the second network. Or, the first access network device may also send connection information to the first network function when the second network indicates that the terminal is in a CM idle state (e.g., the second network has not had any data and / or signaling to be transmitted to the terminal for a long time, and enters the CM idle state for energy saving).

[0657] It should be understood that, considering how the first network function can identify whether the connection information is for the terminal and the second network, in conjunction with the process shown in Figure 11 above, the first network function can obtain the temporary identifier assigned to the terminal by the second network and associate the temporary identifier assigned to the terminal by the second network with the context of the terminal. The first access device can indicate that the connection information is for the terminal by sending the temporary identifier assigned to the terminal by the second network.

[0658] Optionally, the first network function obtains the first temporary identifier from the second access network device.

[0659] The first temporary identifier is a temporary identifier assigned to the terminal by the second network when the terminal establishes a connection with the second network through the second access network device. The first temporary identifier is associated with the terminal's context stored in the first network function, and the second access network device is the access network device that served the terminal before the terminal established a connection with the first access network device.

[0660] It should be understood that the temporary identifier (e.g., GUTI) assigned to the terminal by the CN is usually carried in the NAS message. The access network device transparently transmits the NAS message, and thus the access network device cannot obtain the temporary identifier assigned to the terminal by the CN. In the embodiments of this application, the first access network device or the second access network device can obtain the temporary identifier assigned to the terminal by the CN so as to send the temporary identifier to other core networks registered by the terminal.

[0661] In other words, the first network function can obtain the first temporary identifier assigned to the terminal by the second network through the second access network device, and associate the temporary identifier with the terminal context stored in the first network function. Thus, the first network function can identify that the message is for the terminal and the second network based on the first temporary identifier included in the message, which is easy to deploy and reduces implementation complexity.

[0662] In one possible implementation, the first network function obtains a first temporary identifier from the second access network device, including: obtaining the first temporary identifier from the second access network device when the terminal establishes a connection with the first network through the second access network device, or when the second access network device updates the context of the terminal with the first network function.

[0663] It is understood that the first network function obtains the first temporary identifier from the second access network device, as can be seen in steps S1111 and S1117 of Figure 11, which will not be repeated here.

[0664] In addition, according to the relevant description in Figure 12 regarding the first network function obtaining the temporary identifier assigned to the terminal by the second network, the first network can obtain the temporary identifier assigned to the terminal by the second network from the terminal. This application embodiment does not specifically limit this.

[0665] In other words, the first network function can obtain the first temporary identifier during the process of the terminal establishing a connection with the first network through the second access network device, or it can obtain the first temporary identifier by updating the terminal's context flow after the terminal has established a connection with the first network, thereby improving the flexibility of the first network function in obtaining the first temporary identifier.

[0666] In one possible implementation, the second network sends a first temporary identifier to the first access network device. Correspondingly, the first access network device receives the first temporary identifier from the second network. The first temporary identifier is a temporary identifier assigned to the terminal by the second network before the terminal establishes a connection with the second network through the first access network device.

[0667] It can be understood that the first temporary identifier is a temporary identifier assigned to the terminal by the second network before the terminal establishes a connection with the second network through the first access network device. This can mean that the first temporary identifier is a temporary identifier assigned to the terminal by the second network when the terminal establishes a connection with the second network through the second access network device.

[0668] In addition, the second network sends a first temporary identifier to the first access network device, which can be seen in step S1210 and will not be described again here.

[0669] In other words, the second network can directly send the first temporary identifier to the first access network device, thereby reducing the signaling requests from the first access network device to the second network and lowering signaling overhead.

[0670] In one possible implementation, the first network function obtains connection information between the terminal and the second network, including obtaining connection information from a first access network device. This connection information includes a first temporary identifier and indication information indicating that the terminal is in a connected state.

[0671] It is understandable that "the terminal is in a connected state" could mean either that the terminal is in RRC connected state or CM connected state. Additionally, considering that the first temporary identifier is assigned to the terminal by the second network, "the terminal is in a connected state" could also mean that the terminal is in CM connected state on the second network.

[0672] It is understood that the first network function obtains connection information from the first access network device, as can be seen in step S1212, which will not be repeated here.

[0673] In other words, considering that the terminal has already established a connection with the first access network device, by sending a first temporary identifier and an indication message indicating that the terminal is in a connected state to the first network function through the first access network device, the first access network device can determine that the terminal has entered the connected state from the idle state, and that the terminal's current serving access network device is the first access network device. As a result, the first network function will not page the terminal (e.g., send a paging message to all access devices under the terminal's registered TAI list). This solves the problem that the terminal releases its connection with the first access network device and establishes a connection with other access network devices after detecting paging messages from multiple access network devices, causing the terminal's connection state in the second network to change from the connected state to the idle state (i.e., causing the terminal's connection state to become disordered).

[0674] In one possible implementation, the method shown in Figure 14 further includes: a first network function obtaining a second temporary identifier from a first access network device. The second temporary identifier is a temporary identifier assigned to the terminal by the second network when the terminal establishes a connection with the second network through the first access network device.

[0675] It is understood that the first network function obtains the second temporary identifier, which can be referred to in step S1210, and will not be repeated here.

[0676] In other words, the first network function can also obtain the second temporary identifier newly assigned to the terminal by the second network, thereby ensuring that the first network function can continue to identify the connection information between the terminal and the second network in the future, and realize the synchronization of the connection status of the terminal between the first network and the second network.

[0677] Optionally, the first access network device receives a second temporary identifier from the second network and sends the second temporary identifier to the first network function.

[0678] In other words, the first access network device can directly receive the second temporary identifier from the second network, thereby reducing the signaling requests from the first access network device to the second network and reducing signaling overhead.

[0679] In one possible implementation, the method shown in Figure 14 further includes:

[0680] The first access network device sends first identification information or second identification information to the first network function. Correspondingly, the first network function obtains the first identification information or second identification information from the first access network device.

[0681] The first identification information is the identification information assigned to the terminal by the first access network device on the first interface to identify the terminal. The first interface is the interface through which the first access network device interacts with the first network function. The second identification information is the identification information assigned to the terminal on the second interface. The second interface is the interface through which the first access network device interacts with the second network function of the second network.

[0682] It is understood that the difference between the first identification information and the second identification information is that the first identification information refers to the first interface through which the first access device interacts with the first network function, while the second identification information refers to the second interface through which the first access network device interacts with the second network function. In other words, when the first access network device interacts with the first network function, it can reuse the identification information allocated by the first access network device for the terminal to identify the terminal on the second interface, such as NGAP pair UE ID#3 in step S1312.

[0683] In addition, the first identification information can be found in step S1212, and the second identification information can be found in step S1312, which will not be repeated here.

[0684] In other words, after the first network function obtains the first identification information or the second identification information from the first access network device, it can use the first identification information or the second identification information to instruct the terminal in the message sent to the first access network device. As a result, the first access network device does not need to broadcast the terminal's paging message on the air interface, thereby avoiding the problem that the terminal may not respond to the paging of the subnet.

[0685] Optionally, the first identification information is a transaction identifier, which is used to identify the terminal or to indicate the data and / or signaling to be transmitted to the terminal.

[0686] It is understood that the transaction identifier is different from the NGAP UE ID in step S1212. The transaction identifier can indicate that the terminal has data and / or signaling to be transmitted. Please refer to the transaction identifier in step S1212, which will not be repeated here.

[0687] In other words, the first network function sends a transaction identifier to the first access network device, enabling the first access network device to know that the terminal has data or signaling to be transmitted, without having to page the terminal on the air interface, thus improving the efficiency of instruction.

[0688] Alternatively, the first identification information may be the NGAP identifier assigned by the first access network device on the first interface.

[0689] It is understood that the NGAP identifier can be the NGAP UE ID#4 in step S1212. In addition, the first access network device sends the NGAP UE ID#4 to the first network function, which is equivalent to establishing the terminal's connection on the first interface in advance (or N2 connection), thus improving the efficiency of the terminal establishing a connection with the first network.

[0690] B. The first network function obtains connection information from the second network function of the second network.

[0691] In one possible implementation, the second network function obtains the identifier of the first network function and, based on the identifier, sends connection information between the terminal and the second network. Correspondingly, the first network function receives connection information from the second network function. This connection information indicates whether a connection exists between the terminal and the second network.

[0692] In other words, the second network function obtains the identifier of the first network function, and then sends the connection information between the terminal and the second network to the first network function according to the identifier of the first network function, so that the first network function can obtain the connection status of the terminal in the second network. Thus, when the first network wants to establish a connection with the terminal, it determines the paging terminal or establishes a connection with the first access network device corresponding to the terminal according to the connection information, thereby realizing the collaborative management of the connection status of the terminal by the first network and the second network.

[0693] It is understandable that the identifier of the first network function can also be used by the second network function to send connection information to the first network function.

[0694] Furthermore, similar to the connection information sent by the first access network device mentioned above, the second network function can send connection information to the first network function when the terminal's connection status changes. For example, if the terminal is not connected to the second network, the second network function sends connection information to the first network function to indicate that the terminal is not connected to the second network. As another example, if the terminal is connected to the second network, the second network function sends connection information to the first network function to indicate that the terminal is connected to the second network. The aforementioned explanation regarding the first access network device sending connection information will not be repeated here.

[0695] In one possible implementation, the second network function sends connection information to the first network function based on the identification information of the first network function. This includes: if the second network establishes a connection with the terminal through the first access network device, sending connection information to the first network function based on the identification of the first network function. Accordingly, the first network function obtains the connection information from the second network function. This connection information indicates that a connection exists between the terminal and the second network.

[0696] It is understood that when the second network establishes a connection through the first access network device, it may mean that the second network is in the process of establishing a connection through the first access network device, or that a connection has already been established. Please refer to the relevant explanation of step S1312, which will not be repeated here.

[0697] In other words, when the second network establishes a connection with the terminal through the first access network device, the second network function sends connection information that the terminal is connected to the second network to the first network function. This allows the first network function to determine that the terminal has re-entered the connected state. Consequently, when the first network wants to establish a connection with the terminal, the first network function does not page the terminal but instead establishes a connection corresponding to the terminal with the first access network device. This solves the problem that when the first network pages the terminal, the terminal switches its current serving access network device, causing the terminal's connection state in the second network to change from connected to idle (i.e., the terminal's connection state becomes disordered).

[0698] It should be understood that the second network function can obtain the identifier of the first network function in various ways, which will be introduced below.

[0699] Implementation Method 1

[0700] In one possible implementation, the second network function obtains the identifier of the first network function of the first network, including: the second network function obtains a third temporary identifier, and determines the identifier of the first network function based on the third temporary identifier.

[0701] The third temporary identifier is a temporary identifier assigned to the terminal by the first network when the terminal establishes a connection with the first network through the second access network device. The second access network device is the access network device that serves the terminal before the terminal establishes a connection with the first access network device.

[0702] It is understood that the identifier of the first network function is determined based on the temporary identifier (e.g., GUTI) assigned by the first network. Please refer to the relevant description of step S1111 in Figure 11, which will not be repeated here.

[0703] In other words, the second network function can determine the identifier of the first network function based on the temporary identifier assigned to the terminal by the first network, thereby improving the efficiency of determining the identifier of the first network function.

[0704] Optionally, the second network function obtains the third temporary identifier by: obtaining the third temporary identifier from the second access network device when the terminal establishes a connection with the second network through the second access network device, or when the second access network device and the second network function update the context of the terminal; or, when the terminal establishes a connection with the second network through the first access network device, receiving a registration request from the terminal, the registration request including the third temporary identifier.

[0705] In other words, the second network function can obtain the third temporary identifier during the process of the terminal establishing a connection with the second network through the second access network device, or during the process of updating the terminal's context, or through the registration request sent by the terminal, thereby improving the flexibility of the second network function in obtaining the third temporary identifier.

[0706] Method 2

[0707] In another possible implementation, the second network function obtains the identifier of the first network function by: obtaining the identifier of the first network function from the second access network device when the terminal establishes a connection with the second network through the second access network device, or when the second access network device and the second network function update the context of the terminal.

[0708] In other words, the second network function can directly obtain the identifier of the first network function during the process of the terminal establishing a connection with the second network through the second access network device, or during the process of the second access network device and the second network function updating the context of the terminal. Thus, if the second network function cannot determine the identifier of the first network function based on the third temporary identifier, it can ensure that the second network function obtains the identifier of the first network function.

[0709] In one possible implementation, the first network function obtains connection information between the terminal and the second network, including obtaining connection information from the second network function. This connection information includes a permanent identifier for the terminal and indication information indicating that the terminal is in a connected state.

[0710] It is understood that the permanent identifier of the terminal can be, for example, the terminal's SUPI, which is used to indicate that the terminal is in a connected state. Please refer to the relevant description of step S1312 above, which will not be repeated here.

[0711] In other words, the first network function determines that the terminal has established a connection with the second network based on the connection information. Therefore, the first network function will not page the terminal (e.g., send a paging message to all access devices under the terminal's registered TAI list). This solves the problem of the terminal releasing its connection with the first access network device and establishing a connection with other access network devices after detecting paging messages from multiple access network devices, which would cause the terminal's connection state in the second network to change from connected to idle (i.e., cause the terminal's connection state to become disordered).

[0712] In one possible implementation, the method shown in Figure 14 further includes:

[0713] The second network function sends second identification information to the first network function. Correspondingly, the first network function obtains the second identification information from the second network function. The second identification information is the identification information of the terminal on the second interface, which is the interface through which the first access network device and the second network function interact.

[0714] It is understood that the second network function is different from the aforementioned first access network device. The identification information used by the first access network device to identify the terminal is usually allocated by the first access network device. The identification information stored by the second network function to identify the terminal is the interface (i.e., the second information) used for interaction between the first access network device and the second network. Then the second network function sends the second identification information, which can be referred to in step S1310, and will not be repeated here.

[0715] In other words, the second network function can reuse the second identification information used between the first access network device and the second network, so that the first access network device can determine that the message sent by the first network function is for the middle unit. As a result, the first access network device does not need to broadcast the terminal's paging message on the air interface, thereby avoiding the problem that the terminal may not respond to the paging of the subnet.

[0716] In one possible implementation, if the first network intends to establish a connection with the terminal, and the terminal already has a connection with the second network, the first network function establishes a connection with the first access network device, including:

[0717] A first network function sends a first message to a first access network device. Correspondingly, the first access network device receives the first message from the first network function. The first message includes first identification information or second identification information, which is used by the first access network device to determine that the first message is a message addressed to a terminal.

[0718] It is understood that the first network function sends the first message to the first access network device, as can be seen in step S1215 or step S1315, which will not be repeated here.

[0719] In other words, when the first network wants to establish a connection with the terminal, the first network function can enable the first access network device to identify the terminal by carrying the first identification information or the second identification information in the first message, thereby avoiding the first access network device from paging the terminal on the air interface.

[0720] In one possible implementation, the first message is used to instruct the first access network device to send first instruction information to the terminal, and the first instruction information is used to instruct the terminal to initiate a connection establishment process to the first network; or, the first message includes first identification information, identification information allocated by the first network to the terminal on the first interface to identify the terminal, and data and / or signaling to be transmitted to the terminal, and the first message is used to instruct the second access network device to send the data and / or signaling to be transmitted to the terminal.

[0721] It is understood that the first access network device sends a first instruction message to the terminal based on the first message. Alternatively, the first access network device sends data and / or signaling to be transmitted to the terminal based on the first message.

[0722] Additionally, the first network assigns identification information to the terminal on the first interface, such as CN NGAP UE ID#4 in step S1215.

[0723] In other words, the first message can be used to instruct the first access network device to send the first instruction information to instruct the terminal to initiate a connection establishment process with the first network, or it can be used to instruct the first access network device to send data and / or signaling to simplify the connection establishment process between the first network and the terminal, save signaling overhead, and improve efficiency.

[0724] In one possible implementation, the method shown in Figure 14 further includes: a first network function acquiring a third temporary identifier and a fourth temporary identifier, and sending the third temporary identifier and the fourth temporary identifier to a first access network device. Correspondingly, the first access network device receives the third temporary identifier and the fourth temporary identifier from the first network function and sends the third temporary identifier and the fourth temporary identifier to a second network function.

[0725] The third temporary identifier is a temporary identifier assigned to the terminal by the first network when the terminal establishes a connection with the first network through the second access network device. The fourth temporary identifier is a temporary identifier assigned to the terminal by the first network when the terminal establishes a connection with the first network through the first access network device.

[0726] It is understood that the first network function sends the third temporary identifier and the fourth temporary identifier to the first access network device, as can be seen in step S1219. The first access network device sends the third temporary identifier and the fourth temporary identifier to the second network function, as can be seen in step S1221, which will not be repeated here.

[0727] In other words, the first network function can send the third temporary identifier and the fourth temporary identifier to the second network function through the first access network device, so as to inform the second network function terminal of the newly allocated temporary identifier on the first network side, thereby ensuring that the second network function can identify the connection information between the terminal and the first network and realize the synchronization of the terminal's connection status between the first network and the second network.

[0728] In one possible implementation, the method shown in FIG14 further includes: a first network function sending indication information to a first access network device, instructing the first access network device to send a third temporary identifier and a fourth temporary identifier to a second network function of a second network. Correspondingly, the first access network device receives the indication information from the first network function, instructing the first access network device to send the third temporary identifier and the fourth temporary identifier to the second network function of the second network.

[0729] In other words, the first network function can directly instruct the first access network device to send the third temporary identifier and the fourth temporary identifier to the second network function, so as to ensure that the first access network device can determine which network to send the third temporary identifier and the fourth temporary identifier to.

[0730] In one possible implementation, the method shown in Figure 14 further includes: the first network function sending an identifier of the second network function to the first access network device. The identifier of the second network function is used for communication between the first access network device and the second network function.

[0731] In other words, the first network function can also send the identifier of the second network function to the first access network device, so that the first access network device can send the third temporary identifier and the fourth temporary identifier to the second network function according to the identifier of the second network function, thereby ensuring that the first access network device can communicate with the second network function to send the third temporary identifier and the fourth temporary identifier to the second network function.

[0732] In one possible implementation, the method shown in Figure 14 further includes: a first network function updating the terminal's serving access network device from a second access network device to a first access network device.

[0733] It is understood that the service access network device of the first network function update terminal can be referred to in steps S1213 and S1313, which will not be repeated here.

[0734] In other words, after the first network obtains the connection information between the terminal and the second network, it can update the terminal's service access network device from the second access network device to the first access network device, so that it can communicate with the terminal through the first access network device in the future.

[0735] In one possible implementation, the method shown in Figure 14 further includes: a first access network device or a second network function sending second indication information to a first network function. Accordingly, the first network function receives the second indication information, which indicates that the context established by the first network function for the terminal should not be released.

[0736] It is understood that the second instruction information can be found in step S1212, and will not be repeated here.

[0737] In other words, by instructing not to release the context established by the first network function for the terminal, unnecessary signaling overhead can be avoided when the first network enters an idle state due to the lack of data and / or signaling from the terminal and then tries to establish a connection with the terminal again.

[0738] Option 2

[0739] The difference between Scheme 2 and Scheme 1 is that after the terminal responds to the paging of the second network and establishes a connection with the second network through the first access network device, the terminal can actively initiate a connection establishment process to the first network through the first access network device; or, after the terminal detects a paging from the first network from multiple access network devices, the terminal does not switch the serving access network device and initiates a connection establishment process to the first network through the current serving access network device.

[0740] The following example, using the UE detecting a paging message from the first network, illustrates Scheme 2.

[0741] Figure 15 is a schematic flowchart of a communication method provided in an embodiment of this application. As shown in Figure 15, the flowchart is illustrated using the interaction between UE, RAN#1, RAN#2, N2 agent#1, AM#1, MM#1, AUSF, N2 agent#2, AM#2, and MM#2 as an example. The flowchart includes steps S1501 to S1521.

[0742] S1501 and UE establish connections with the main network and subnet respectively.

[0743] It is understood that the implementation of step S1501 can be referred to the process shown in Figure 11 or Figure 10, and will not be repeated here.

[0744] S1502, Release the AN connection between UE and RAN#1.

[0745] It is understood that the implementation of step S1302 can be referred to step S1202.

[0746] S1503, release the N2 context of the UE between RAN#1 and N2 agent #1.

[0747] It is understood that the implementation of step S1303 can be found in step S1203.

[0748] S1504, Release the N2 context of the UE between RAN#1 and N2 agent #2.

[0749] It is understood that the implementation of step S1304 can be found in step S1204.

[0750] S1505, AM#1 sends NAS message transmission #1 to N2 agent #1. Correspondingly, N2 agent #1 receives NAS message transmission #1 from AM#1.

[0751] It is understood that the implementation of step S1305 can refer to step S1205.

[0752] S1506, N2 agent #1 sends paging message #1 to RAN #2. RAN #2 receives paging message #1 from N2 agent #1.

[0753] It is understood that the implementation of step S1306 can refer to step S1206.

[0754] S1507, RAN#2 broadcasts paging message #1. Correspondingly, the UE receives paging message #1 from RAN#2.

[0755] It is understood that the implementation of step S1307 can be found in step S1207.

[0756] S1508, UE sends Service Request Message #1 to RAN#2. Correspondingly, RAN#2 receives Service Request Message #1 from UE.

[0757] Among them, the service request message #1 includes the GUTI#1 corresponding to TMSI#1.

[0758] In addition, the difference between step S1508 and step S1308 is that the service request message #1 in step S1508 is forwarded by RAN#2 to N2 agent #1 (step S1509) so that RAN#2 and N2 agent #1 can establish an N2 interface #3 context, which includes, for example, NGAP pair UE ID #3, instead of N2 agent #1 sending UE connection information to N2 agent #2 of the subnet (see step S1312).

[0759] Additionally, in step S1508, the service request message #1 may not include GUTI#2.

[0760] S1509, RAN#2 sends RAN NGAP UE ID#3 and service request message#1 to N2 agent#1. Correspondingly, N2 agent#1 receives RAN NGAP UE ID#3 and service request message#1 from RAN#2.

[0761] It is understood that the implementation of step S1509 can be found in step S1309.

[0762] S1510, N2 Agent #1 sends NGAP pair UE ID #3 to RAN #2. Correspondingly, RAN #2 receives NGAP pair UE ID #3 from N2 Agent #1.

[0763] It is understood that the implementation of step S1510 can be found in step S1310.

[0764] The subsequent connection establishment process is completed between S1511, UE, RAN#2, N2 agent#1, AM#1, and MM#1.

[0765] It is understood that step S1511 is the same as step S1311, and will not be repeated here.

[0766] S1512, The UE determines to initiate a connection establishment process to the subnet.

[0767] It is understandable that in step S1512, after the UE executes step S1511 (that is, after the UE responds to the paging of the main network and the UE establishes a connection with the main network), the UE determines to actively initiate a connection establishment process to the subnet.

[0768] In addition, the connection establishment process includes the process of the UE sending a service request or registration request to the subnet, etc., and there are no restrictions on this.

[0769] In other words, after the UE establishes a connection with the main network, the UE initiates a connection establishment process to the subnet so that the UE actively establishes a connection with the subnet. Then, the UE and the subnet work together to enter the connected state on the main network side. This solves the problem shown in Figure 9 that the UE may not respond to the subnet's paging, and that the UE may switch the serving RAN from RAN#2 to another RAN other than RAN#2 because it responds to the subnet's paging, which causes the UE's connection state on the main network side to change from the connected state to the idle state (i.e., the problem of disorder in the UE's connection state).

[0770] Optionally, after the UE establishes a connection with the main network, and the UE receives a paging from the subnet through multiple RANs (e.g., including RANs other than RAN#2), the UE determines to initiate a connection establishment procedure to the subnet through RAN#2.

[0771] In other words, after the UE establishes a connection with the main network, the UE does not actively establish a connection with the subnet. Instead, when the UE receives a paging message from the subnet from multiple RANs, the UE initiates a connection establishment process with the subnet through the current serving RAN (i.e., RAN#2). This solves the problem that the connection state on the main network side changes from connected state to idle state due to the UE switching serving RAN (i.e., the problem of disordered connection state of the UE).

[0772] The following example illustrates the subsequent steps using the UE actively initiating a service request to the subnet.

[0773] S1513, UE sends Service Request Message #2 to RAN#2. Correspondingly, RAN#2 receives Service Request Message #2 from UE.

[0774] It is understood that the implementation of step S1513 can be found in step S1317.

[0775] S1514, RAN#2 sends to N2 Agent #2 an identifier (e.g., RAN NGAP UE ID#4) assigned by RAN#2 for the UE to identify the UE on N2 interface #4, and a service request message #2. Correspondingly, N2 Agent #2 receives the RAN NGAP UE ID#4 and the service request message #2 from RAN#2.

[0776] It is understood that the implementation of step S1514 can be found in step S1318.

[0777] S1515, N2 Agent #2 sends NGAP pair UE ID #4 to RAN #2. Correspondingly, RAN #2 receives NGAP pair UE ID #4 from N2 Agent #2.

[0778] It is understood that the implementation of step S1514 can be found in step S1319.

[0779] The subsequent connection establishment process is completed between S1516, UE, RAN#2, N2 agent#2, AM#2, and MM#2.

[0780] It is understood that the implementation of step S1516 can be found in step S1216, and will not be repeated here.

[0781] The following example illustrates the steps a UE takes to initiate a service request to a subnet, using the example of a UE receiving a paging message from a subnet via RAN#3.

[0782] S1517, AM#2 sends NAS message transmission #2 to N2 agent #2. Correspondingly, N2 agent #2 receives NAS message transmission #2 from AM#2.

[0783] It is understood that step S1517 can be referred to step S1214.

[0784] S1518, N2 agent #2 sends paging message #2 to RAN #3. Correspondingly, RAN #2 receives paging message #2 from N2 agent #2.

[0785] It is understandable that N2 agent #2 can send paging message #2 to all RANs under the TAI list. For example, N2 agent #2 may also send paging message #2 to RAN #3. Furthermore, the implementation of step S1518 is similar to the aforementioned step S1506, and will not be described again.

[0786] S1519, RAN#2 broadcasts paging message #2. Correspondingly, the UE receives paging message #2 from RAN#3.

[0787] It is understandable that step S1519 is similar to step S1507, and will not be described again here.

[0788] S1520, the UE determines the process of initiating a service request to the subnet through RAN#2.

[0789] It is understood that step S1520 can be referred to step S1512, and will not be repeated here.

[0790] In addition, the subsequent steps include S1521 to S1524, which are the same as steps S1513 to S1516, and will not be described again here.

[0791] In this embodiment of the application, when the UE registers to both the main network and the subnet, if the UE responds to the paging message from the main network and establishes a connection with the main network through RAN#2, it also initiates a connection establishment process to the subnet through RAN#2. This allows the terminal to avoid switching its current serving RAN (i.e., RAN#2), thus solving the problem of the terminal switching its current serving RAN (i.e., RAN#2) to other RANs due to receiving paging messages from the subnets from multiple RANs, which causes the UE's connection state to become disordered (e.g., the UE's connection state on the main network side changes from connected to idle).

[0792] The following describes Scheme 2 provided in the embodiments of this application in conjunction with the process shown in Figure 15 above.

[0793] Figure 16 is a schematic flowchart of a communication method provided in an embodiment of this application. As shown in Figure 16, the process includes steps S1601 to S1602.

[0794] S1601, The second network sends a paging message to the terminal. Accordingly, the terminal receives the paging message from the second network.

[0795] S1602. In response to a paging message from the second network, if the terminal has established a connection with the second network through the first access network device, the terminal initiates a connection establishment process to the first network through the first access network device.

[0796] In one possible implementation, the terminal initiates a connection establishment process to the first network through the first access network device, including:

[0797] When a terminal receives a paging message from the first network, the terminal initiates a connection establishment process with the first network through the first access network device.

[0798] In other words, after the terminal establishes a connection with the second network, the terminal does not actively establish a connection with the second network. Instead, when the terminal receives a paging message from the first network from multiple access network devices, the terminal initiates a connection establishment process with the first network through the current serving access network device (i.e., the first access network device), thereby solving the problem of the terminal's connection status becoming disordered due to the terminal switching serving access network devices.

[0799] It is understood that the implementation of the above steps S1601 to S1602 can be referred to the process shown in Figure 15, and will not be repeated here.

[0800] In this embodiment of the application, when the terminal registers with the first network and the second network respectively, if the terminal responds to the paging message of the second network and establishes a connection with the second network through the first access network device, then the terminal also initiates a connection establishment process to the first network through the first access network device. This allows the terminal to avoid switching its current serving access network device, thereby solving the problem that the terminal's connection state becomes disordered due to receiving paging messages from multiple access network devices from the first network and switching its current serving access network device (i.e., the first access network device) to other access network devices (e.g., the terminal's connection state in the second network changes from connected to idle).

[0801] The above mainly describes the solutions provided by the embodiments of this application from the perspective of interaction between various network elements. Correspondingly, the embodiments of this application also provide a communication device for implementing the various methods described above. This communication device can be a user plane entity, session management entity, policy management entity, network access entity, or application entity in the above method embodiments, or a device containing the aforementioned user plane entity, session management entity, policy management entity, network access entity, or application entity, or a component usable by a user plane entity, session management entity, policy management entity, network access entity, or application entity. It is understood that, in order to achieve the above functions, the communication device includes hardware structures and / or software modules corresponding to the execution of each function. Those skilled in the art should readily recognize that, in conjunction with the units and algorithm steps of the various examples described in the embodiments disclosed herein, this application can be implemented in hardware or a combination of hardware and computer software. Whether a function is executed in hardware or by computer software driving hardware 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.

[0802] This application embodiment can divide the communication device into functional modules according to the above method embodiment. For example, each function can be divided into a separate functional module, or two or more functions can be integrated into one processing module. The integrated module can be implemented in hardware or as a software functional module. It should be noted that the module division in this application embodiment is illustrative and only represents one logical functional division. In actual implementation, there may be other division methods.

[0803] Taking the communication device as an example of the first network function, second network function, first access network device, or terminal in the above method embodiments, Figure 17 is a schematic diagram of the structure of a communication device provided in an embodiment of this application. As shown in Figure 17, the communication device 1700 includes: a processing module 1701 and a transceiver module 1702. The processing module 1701 is used to execute the processing functions exemplified by the first network function, second network function, first access network device, or terminal in the above method embodiments. The transceiver module 1702 is used to execute the transceiver functions exemplified by the first network function, second network function, first access network device, or terminal in the above method embodiments.

[0804] All relevant content of each step involved in the above method embodiments can be referenced from the functional description of the corresponding functional module, and will not be repeated here.

[0805] Since the communication device 1700 provided in this embodiment can execute the above communication method, the technical effects it can achieve can be referred to the above method embodiment, and will not be repeated here.

[0806] In one possible design, the transceiver module 1702 may include a receiving module and a transmitting module (not shown in Figure 17). The transceiver module is used to implement the transmitting and receiving functions of the communication device 1700.

[0807] In one possible design, the communication device 1700 may further include a storage module (not shown in FIG. 17) that stores programs or instructions. When the processing module 1701 executes the program or instructions, the communication device 1700 may perform the first network function, the second network function, the first access network device, or the terminal as shown in any of the methods shown in FIG. 7 to FIG. 16.

[0808] It should be understood that the processing module 1701 involved in the communication device 1700 can be implemented by a processor or processor-related circuit components, and can be a processor or processing unit; the transceiver module 1702 can be implemented by a transceiver or transceiver-related circuit components, and can be a transceiver or transceiver unit.

[0809] For example, FIG18 is a schematic diagram of another communication device provided in an embodiment of this application. This communication device may be a first network function, a second network function, a first access network device, or a terminal, or it may be a chip (system) or other component or assembly that can be disposed in the first network function, second network function, first access network device, or terminal. As shown in FIG18, the communication device 1800 may include a processor 1801. In one possible design, the communication device 1800 may further include a memory 1802 and / or a transceiver 1803. The processor 1801 is coupled to the memory 1802 and the transceiver 1803, for example, they can be connected via a communication bus.

[0810] The following is a detailed description of each component of the communication device 1800, with reference to Figure 18:

[0811] The processor 1801 is the control center of the communication device 1800. It can be a single processor or a collective term for multiple processing elements. For example, the processor 1801 can be one or more central processing units (CPUs), application-specific integrated circuits (ASICs), or one or more integrated circuits configured to implement the embodiments of this application, such as one or more digital signal processors (DSPs), or one or more field-programmable gate arrays (FPGAs).

[0812] In one possible design, the processor 1801 can perform various functions of the communication device 1800 by running or executing software programs stored in the memory 1802 and calling data stored in the memory 1802.

[0813] In a specific implementation, as one example, processor 1801 may include one or more CPUs, such as CPU0 and CPU1 shown in FIG18.

[0814] In a specific implementation, as one embodiment, the communication device 1800 may also include multiple processors, such as processors 1801 and 1804 shown in FIG. 18. Each of these processors may be a single-core processor (single-CPU) or a multi-core processor (multi-CPU). Here, a processor may refer to one or more devices, circuits, and / or processing cores used for processing data (e.g., computer program instructions).

[0815] The memory 1802 is used to store the software program that executes the solution of this application, and is controlled by the processor 1801 to execute it. The specific implementation method can be referred to the above method embodiment, and will not be repeated here.

[0816] In one possible design, the memory 1802 can be a read-only memory (ROM) or other type of static storage device capable of storing static information and instructions, random access memory (RAM) or other type of dynamic storage device capable of storing information and instructions, or it can be an electrically erasable programmable read-only memory (EEPROM), a compact disc read-only memory (CD-ROM) or other optical disc storage, optical disc storage (including compressed optical discs, laser discs, optical discs, digital universal optical discs, Blu-ray discs, etc.), magnetic disk storage media or other magnetic storage devices, or any other medium capable of carrying or storing desired program code in the form of instructions or data structures and accessible by a computer, but is not limited thereto. The memory 1802 can be integrated with the processor 1801 or exist independently and coupled to the processor 1801; this application embodiment does not specifically limit this.

[0817] Transceiver 1803 is used for communication with other communication devices. For example, if communication device 1800 is a first network function, transceiver 1803 can be used to communicate with a second network function or a first access network device. As another example, if communication device 1800 is a terminal, transceiver 1803 can be used to communicate with a first access network device.

[0818] In one possible design, transceiver 1803 may include a receiver and a transmitter (not shown separately in Figure 18). The receiver is used to implement the receiving function, and the transmitter is used to implement the transmitting function.

[0819] In one possible design, the transceiver 1803 can be an input / output interface or interface circuit for inputting and / or outputting signals.

[0820] In one possible design, the transceiver 1803 can be integrated with the processor 1801, or it can exist independently and be coupled to the processor 1801. This application embodiment does not specifically limit this.

[0821] It should be noted that the structure of the communication device 1800 shown in Figure 18 does not constitute a limitation on the communication device. The actual communication device may include more or fewer components than shown, or combine certain components, or have different component arrangements.

[0822] Furthermore, the communication device 1800 can execute the above-described communication method, and therefore the technical effects it can achieve can be referred to the above-described method embodiments, which will not be repeated here.

[0823] In one possible implementation, this application also provides a computer-readable storage medium storing a computer program or instructions that, when executed by a computer, implement the functions of the above-described method embodiments.

[0824] In one possible implementation, this application also provides a computer program product that, when executed by a computer, implements the functions of the above-described method embodiments.

[0825] In one possible implementation, this application embodiment also provides a communication system that includes the first network function described in the above method embodiments.

[0826] Optionally, the communication system may also include a second access network device and / or a second network function.

[0827] In one possible implementation, this application embodiment also provides a communication system, which includes the terminal described in the above method embodiments.

[0828] Optionally, the communication system may further include the second access network device and / or the first network function described in the above method embodiments.

[0829] In one possible implementation, this application also provides a communication method, which includes the method described in any of the above-described method embodiments or any implementation thereof.

[0830] In the above embodiments, implementation can be achieved, in whole or in part, through software, hardware, firmware, or any combination thereof. When implemented using software programs, implementation can be, in whole or in part, in the form of a computer program product. This computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, all or part of the flow or function according to the embodiments of this application is generated. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions can be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another. For example, computer instructions can be transmitted from one website, computer, server, or data center to another website, computer, server, or data center via wired (e.g., coaxial cable, fiber optic, digital subscriber line (DSL)) or wireless (e.g., infrared, wireless, microwave, etc.) means. The computer-readable storage medium can be any available medium accessible to a computer or a data storage device including one or more servers, data centers, etc., that can be integrated with the medium. The available medium can be a magnetic medium (e.g., floppy disk, hard disk, magnetic tape), an optical medium, or a semiconductor medium (e.g., a solid-state drive (SSD)).

[0831] Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented 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.

[0832] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working processes of the systems, devices, and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here.

[0833] In the several embodiments provided in this application, it should be understood that the disclosed systems, apparatuses, and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between apparatuses or units may be electrical, mechanical, or other forms.

[0834] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0835] In addition, the functional units in the various embodiments of this application can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit.

[0836] If the aforementioned functions 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 a portion 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.) 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.

[0837] Although this application has been described herein in conjunction with various embodiments, those skilled in the art, by reviewing the accompanying drawings, the disclosure, and the appended claims, will understand and implement other variations of the disclosed embodiments in carrying out the claimed application. In the claims, the word "comprising" does not exclude other compone...

Claims

1. A communication method, characterized in that, The method, applied to a first network function of a first network, includes: The connection information between the terminal and the second network is obtained, and the connection information indicates whether there is a connection between the terminal and the second network. The first network and the second network serve the terminal. If the first network needs to establish a connection with the terminal, and the terminal does not have a connection with the second network, then the terminal is paged; if the terminal has a connection with the second network, then a connection corresponding to the terminal is established with the first access network device, and the terminal establishes a connection with the second network through the first access network device.

2. The method according to claim 1, characterized in that, The method further includes: A first temporary identifier is obtained from the second access network device. The first temporary identifier is a temporary identifier assigned to the terminal by the second network when the terminal establishes a connection with the second network through the second access network device. The first temporary identifier is associated with the context of the terminal stored in the first network function. The second access network device is the access network device that served the terminal before the terminal established a connection with the first access network device.

3. The method according to claim 2, characterized in that, The step of obtaining the first temporary identifier from the second access network device includes: When the terminal establishes a connection with the first network through the second access network device, or when the second access network device updates the context of the terminal with the first network function, the first temporary identifier is obtained from the second access network device.

4. The method according to claim 2 or 3, characterized in that, The step of obtaining the connection information between the terminal and the second network includes: The connection information is obtained from the first access network device. The connection information includes the first temporary identifier and indication information for indicating that the terminal is in a connected state.

5. The method according to claim 4, characterized in that, The method further includes: The second temporary identifier is obtained from the first access network device. The second temporary identifier is a temporary identifier assigned to the terminal by the second network when the terminal establishes a connection with the second network through the first access network device.

6. The method according to claim 4 or 5, characterized in that, The method further includes: Obtain first identification information or second identification information from the first access network device. The first identification information is the identification information assigned by the first access network device to the terminal on a first interface to identify the terminal. The first interface is the interface through which the first access network device interacts with the first network function. The second identification information is the identification information on a second interface to identify the terminal. The second interface is the interface through which the first access network device interacts with the second network function of the second network.

7. The method according to claim 6, characterized in that, The first identification information is a transaction identifier, which is used to identify the terminal or to indicate data and / or signaling to be transmitted to the terminal.

8. The method according to any one of claims 1-3, characterized in that, The step of obtaining the connection information between the terminal and the second network includes: The connection information is obtained from the second network function of the second network. The connection information includes a permanent identifier of the terminal and indication information for indicating that the terminal is in a connected state.

9. The method according to claim 8, characterized in that, The method further includes: The second identification information is obtained from the second network function. The second identification information is the identification information that identifies the terminal on the second interface. The second interface is the interface through which the first access network device interacts with the second network function.

10. The method according to claim 7 or 9, characterized in that, The step of establishing a connection with the first access network device when the first network needs to establish a connection with the terminal, if the terminal is already connected to the second network, includes: A first message is sent to the first access network device. The first message includes the first identification information or the second identification information. The first identification information or the second identification information is used by the first access network device to determine that the first message is a message for the terminal.

11. The method according to claim 10, characterized in that, The first message is used to instruct the first access network device to send first instruction information to the terminal, wherein the first instruction information is used to instruct the terminal to initiate a connection establishment process to the first network; Alternatively, the first message may include the first identification information, identification information assigned by the first network to the terminal on the first interface to identify the terminal, and data and / or signaling to be transmitted to the terminal. The first message is used to instruct the first access network device to send the data and / or signaling to be transmitted to the terminal to the terminal.

12. The method according to any one of claims 2-7, 10, and 11, characterized in that, The method further includes: Obtain a third temporary identifier and a fourth temporary identifier, wherein the third temporary identifier is a temporary identifier assigned to the terminal by the first network when the terminal establishes a connection with the first network through the second access network device, and the fourth temporary identifier is a temporary identifier assigned to the terminal by the first network when the terminal establishes a connection with the first network through the first access network device. Send the third temporary identifier and the fourth temporary identifier to the first access network device.

13. The method according to claim 12, characterized in that, The method further includes: Send an instruction message to the first access network device, instructing the first access network device to send the third temporary identifier and the fourth temporary identifier to the second network function of the second network.

14. The method according to claim 12 or 13, characterized in that, The method further includes: The identifier of the second network function of the second network is sent to the first access network device. The identifier of the second network function is used for communication between the first access network device and the second network function.

15. The method according to any one of claims 4-14, characterized in that, The method further includes: The terminal's service access network device is updated from the second access network device to the first access network device.

16. The method according to any one of claims 4-15, characterized in that, The method further includes: Receive a second indication message, which indicates that the context established by the first network function for the terminal should not be released.

17. A communication method, characterized in that, Applied to a first access network device, the method includes: Obtain the identifier of the first network function of the first network; Based on the identifier of the first network function, connection information between the terminal and the second network is sent to the first network function. The connection information indicates whether there is a connection between the terminal and the second network. The first network and the second network serve the terminal.

18. The method according to claim 17, characterized in that, The method further includes: Obtain third indication information, which instructs the first network function to send the connection information.

19. The method according to claim 17 or 18, characterized in that, The step of sending the connection information between the terminal and the second network to the first network function according to the identifier of the first network function includes: When the second network establishes a connection with the terminal through the first access network device, the connection information is sent to the first network function according to the identifier of the first network function, and the connection information indicates that the terminal has a connection with the second network.

20. The method according to claim 19, characterized in that, The method further includes: The terminal receives a first temporary identifier from the second network, which is a temporary identifier assigned to the terminal by the second network before the terminal establishes a connection with the second network through the first access network device.

21. The method according to claim 20, characterized in that, The connection information includes the first temporary identifier and indication information for indicating that the terminal is in a connected state.

22. The method according to any one of claims 19-21, characterized in that, The method further includes: Send a first identification information or a second identification information to the first network function. The first identification information is the identification information assigned by the first access network device to the terminal on a first interface to identify the terminal. The first interface is the interface through which the first access network device interacts with the first network function. The second identification information is the identification information on a second interface to identify the terminal. The second interface is the interface through which the first access network device interacts with the second network function of the second network.

23. The method according to claim 22, characterized in that, The first identification information is a transaction identifier, which is used to identify the terminal or to indicate data and / or signaling to be transmitted to the terminal.

24. A communication method, characterized in that, The method, which applies a second network function to a second network, includes: Obtain the identifier of the first network function of the first network, and the first network and the second network service terminal; Based on the identifier of the first network function, connection information between the terminal and the second network is sent to the first network function, and the connection information indicates whether there is a connection between the terminal and the second network.

25. The method according to claim 24, characterized in that, The step of sending the connection information between the terminal and the second network to the first network function according to the identifier of the first network function includes: When the second network establishes a connection with the terminal through the first access network device, the connection information is sent to the first network function according to the identifier of the first network function, and the connection information indicates that the terminal has a connection with the second network.

26. A communication method, characterized in that, Applied to terminals, which are respectively registered to a first network and a second network, the method includes: Receive paging messages from the second network; In response to a paging message from the second network, if the terminal establishes a connection with the second network through the first access network device, the terminal initiates a connection establishment process to the first network through the first access network device.

27. A communication device, characterized in that, The communication device includes a module or unit for performing the method according to any one of claims 1-25.

28. A communication device, characterized in that, The communication device includes a processor configured to cause the communication device to perform the method according to any one of claims 1-25 by means of logic circuits and / or executing instructions.

29. A computer-readable storage medium, characterized in that, The computer-readable storage medium includes instructions that, when executed by a processor, cause the method according to any one of claims 1-25 to be implemented.

30. A computer program product, characterized in that, The computer program product includes instructions that, when executed on a computer, cause the computer to perform the method according to any one of claims 1-25.

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