Communication method and device

Abstract

The present application relates to a communication method and a device. The method comprises: when a terminal sends a first merged registration request to a core network by means of an access network device corresponding to a second RAT to complete merged registration of a first RAT and the second RAT, the terminal sends a first request to a first core network device by means of an access network device corresponding to the first RAT, wherein the first request is used for requesting to establish a connection with the first core network device by means of the access network device corresponding to the first RAT.

Description

Communication methods and devices Technical Field

[0001] This application relates to the field of communications, and more specifically, to a communication method and apparatus. Background Technology

[0002] With technological advancements, multi-network or multi-system interworking is increasingly involved in communication processes. Taking the interworking of two networks or systems as an example, in related technologies, whether in single or dual registration modes, the terminal needs to perform a registration process in each of the two networks or systems to access them. However, this approach increases the terminal's signaling overhead and fails to improve communication efficiency. Summary of the Invention

[0003] This application provides a communication method and device.

[0004] This application provides a communication method, including:

[0005] After the terminal sends a first merge registration request to the core network through the access network device corresponding to the second RAT (Radio Access Technology) to complete the merge registration of the first RAT and the second RAT, the terminal sends a first request to the first core network device through the access network device corresponding to the first RAT. The first request is used to request to establish a connection with the first core network device through the access network device corresponding to the first RAT.

[0006] This application provides a communication method, including:

[0007] After the terminal sends a first merge registration request to the core network through the access network device corresponding to the second RAT to complete the merge registration of the first RAT and the second RAT, the first core network device receives a first request sent by the terminal through the access network device corresponding to the first RAT, wherein the first request is used to request to establish a connection with the first core network device through the access network device corresponding to the first RAT.

[0008] This application provides a terminal, including:

[0009] The first communication unit is configured to send a first request to the first core network device through the access network device corresponding to the first RAT after the terminal completes the merged registration of the first RAT and the second RAT by sending a first merged registration request to the core network through the access network device corresponding to the second RAT. The first request is used to request to establish a connection with the first core network device through the access network device corresponding to the first RAT.

[0010] This application provides a first core network device, including:

[0011] The second communication unit is configured to receive a first request sent by the terminal through the access network device corresponding to the first RAT after the terminal sends a first merge registration request to the core network through the access network device corresponding to the second RAT to complete the merge registration of the first RAT and the second RAT. The first request is used to request to establish a connection with the first core network device through the access network device corresponding to the first RAT.

[0012] This application provides a terminal, including a transceiver, a processor, and a memory. The memory stores a computer program, the transceiver communicates with other devices, and the processor calls and runs the computer program stored in the memory to enable the terminal to perform the methods described above.

[0013] This application provides a first core network device, including a transceiver, a processor, and a memory. The memory stores a computer program, the transceiver communicates with other devices, and the processor calls and runs the computer program stored in the memory to cause the first core network device to perform the aforementioned method.

[0014] This application provides a chip for implementing the above method.

[0015] Specifically, the chip includes a processor for retrieving and running a computer program from memory, causing a device equipped with the chip to perform the methods described above.

[0016] This application provides a computer-readable storage medium for storing a computer program, which, when run by a device, causes the device to perform the above-described method.

[0017] This application provides a computer program product, including computer program instructions that cause a computer to perform the above-described method.

[0018] By adopting the above scheme, the terminal can achieve merged registration with the core network under multiple RATs through a single merged registration request. The terminal can then directly initiate a first request to the core network device through the access network device corresponding to the first RAT to establish a connection between the terminal and the core network device. This allows the terminal to achieve merged registration under multiple RATs with only one registration request. Furthermore, the terminal can access the core network by initiating a connection establishment request from any of the access network devices corresponding to any of the RATs, thus avoiding the signaling overhead caused by repeatedly executing the mobility registration process. This is particularly beneficial in scenarios involving the collaborative operation of multiple systems or networks, improving the communication efficiency between the terminal and various networks or systems. Attached Figure Description

[0019] Figure 1 is a schematic diagram of an application scenario according to an embodiment of this application.

[0020] Figure 2 is a schematic flowchart of a communication method according to an embodiment of this application.

[0021] Figure 3 is a schematic flowchart of a communication method according to another embodiment of this application.

[0022] Figure 4 is a schematic flowchart of a merged registration scenario in which mobility management network elements on the core network side of two communication systems are co-located, according to an embodiment of this application.

[0023] Figures 5 to 9 are various schematic flowcharts illustrating the process of a UE establishing a NAS connection on a 5G-RAN in a scenario where the core network-side mobility management network elements of two communication systems are co-located, according to an embodiment of this application.

[0024] Figure 10 is a schematic flowchart illustrating a merged registration scenario in which the core network-side mobility management network elements of two communication systems are different, according to an embodiment of this application.

[0025] Figures 11 to 14 are various schematic flowcharts illustrating the process of a UE initiating the establishment of a NAS connection with an AMF on a 5G-RAN in a scenario where the core network-side mobility management network elements of the two communication systems are different, according to an embodiment of this application.

[0026] Figure 15 is a schematic block diagram of a terminal according to an embodiment of this application.

[0027] Figure 16 is a schematic block diagram of a first core network device according to an embodiment of the present application.

[0028] Figure 17 is a schematic block diagram of a communication device according to an embodiment of this application.

[0029] Figure 18 is a schematic block diagram of a chip according to an embodiment of this application. Detailed Implementation

[0030] The technical solutions of this application embodiment can be applied to various communication systems, such as: LTE (Long Term Evolution), LTE-A (Long Term Evolution-Advanced), NR (New Radio), evolution of NR, WLAN (Wireless Local Area Network), WiFi (Wireless Fidelity), or other communication systems.

[0031] This application describes various embodiments in conjunction with network devices and terminals. The terminal can be mobile or fixed, and may also be referred to as a mobile station, user unit, etc. The terminal can be a station in a WLAN, or a smart terminal, wireless modem, laptop, tablet, etc. In this application embodiment, the terminal can be a VR (Virtual Reality) terminal / AR (Augmented Reality) terminal, industrial control terminal, autonomous driving terminal, telemedicine terminal, smart grid terminal, transportation safety terminal, smart city terminal, or smart home wireless terminal, etc. By way of example and not limitation, in this application embodiment, the terminal can also be a wearable device.

[0032] In this embodiment, the network device can be a device for communicating with a terminal. The network device can be an access point in a WLAN, an evolved base station in LTE, a relay station, a vehicle-mounted device, a wearable device, a network device in an NR network (gNB, the next generation Node B), a network device in a future PLMN network, or a network device in a non-terrestrial network, etc. By way of example and not limitation, in this embodiment, the network device can have mobility characteristics; for example, the network device can be a mobile device.

[0033] To facilitate understanding of the technical solutions of the embodiments of this application, the relevant technologies of the embodiments of this application are described below. The following relevant technologies are optional solutions and can be combined with the technical solutions of the embodiments of this application in any way, and they all fall within the protection scope of the embodiments of this application.

[0034] Figure 1 exemplarily illustrates a communication system 100. The communication system includes network devices 110 and terminals 120. In one possible implementation, the communication system 100 may include multiple network devices 110, and the coverage area of ​​each network device 110 may include one or more terminals 120; this embodiment does not limit this. In another possible implementation, the communication system 100 may also include other network entities such as mobility management entities and access and mobility management functions; this embodiment does not limit this. The network devices may further include access network devices and core network devices. That is, the communication system may also include multiple core networks for communicating with the access network devices. The access network devices may be base stations of LTE, LTE-A, or NR systems. Taking the communication system shown in Figure 1 as an example, the communication devices may include network devices and terminals with communication functions. The communication devices may also include other devices in the communication system, such as network controllers, mobility management entities, and other network entities; this embodiment does not limit this.

[0035] To facilitate understanding of this application, the basic concepts involved in the embodiments of this application are briefly explained below. It should be understood that the basic concepts described below do not limit the embodiments of this application.

[0036] In related technologies, connection management includes the function of establishing and releasing N1 NAS (Non-access stratum) signaling connections (or NAS connections) between a UE (User Equipment) and an AMF (Access and Mobility Management Function). The N1 NAS signaling connection enables signaling interaction between the UE and the core network. This N1 NAS signaling connection may include connections between the UE and access network equipment, and N2 connections between the access network equipment and the AMF for the UE.

[0037] The N1 NAS signaling connection between the UE and the AMF includes the following two states: CM (Connection Management) - IDLE (idle or idle state) and CM - CONNECTED (connected or connected state).

[0038] When the UE is in CM-IDLE, there are no corresponding N1, AN (Access Network) signaling, N2, or N3 connections. If the UE is simultaneously in CM-IDLE and RM (Registration Management)-REGISTERED states, the UE needs to initiate a service request procedure to respond to paging, unless the UE is in MICO (Mobile Initiated Connection Only) mode; or, if the UE is simultaneously in CM-IDLE and RM (Registration Management)-REGISTERED states, it initiates a service request procedure when it has uplink signaling or data to send. Correspondingly, when the UE state on the AMF side is RM-REGISTERED, the information required for network-to-UE communication is stored in the AMF, which can obtain this information through the 5G-GUTI (5G Globally Unique Temporary Identifier). The UE will provide AN parameters such as 5G-S-TMSI during the AN signaling connection establishment process. Additionally, when the UE is in CM-IDLE state, it can enter MICO mode to reduce power consumption and signaling overhead.

[0039] The state transitions between CM-IDLE (idle state) and CM-CONNECTED (connected state) in the N1 NAS signaling connection between the UE and AMF are explained below:

[0040] When the UE is in CM-IDLE state, it should enter CM-CONNECTED state whenever an AN signaling connection is established. Specifically, when the UE is in CM-IDLE state, it sends an initial NAS signaling message (e.g., any one of Registration Request, Service Request, or Deregistration Request) to initiate the transition from CM-IDLE state to CM-CONNECTED state on the UE side.

[0041] When a UE is in CM-CONNECTED state, an N1 NAS signaling connection exists between the UE and the AMF. This N1 NAS signaling connection utilizes the RRC (Radio Resource Control) connection between the UE and the NG-RAN, and the NGAP (Next Generation Application Protocol) UE association between the AN and the AMF. A UE can be in CM-CONNECTED state without the NGAP being bound to any transport network layer. After the NAS signaling process is completed, the AMF can decide to release the NAS signaling connection with the UE. For example, when the UE is in CM-CONNECTED, the UE enters the CM-IDLE state whenever the AN signaling connection is released; and / or the logical NGAP signaling connection and the UE's N3 user plane connection enter the CM-IDLE state after the AN is released.

[0042] When the UE state stored in the AMF is CM-IDLE or RM-REGISTRATION, the AMF needs to initiate a paging process to the UE and receive a response when it needs to send signaling or data to the UE, thus executing the service request procedure initiated by the network side. On the AMF side, whenever an N2 connection is established and / or an N2 context is established for a UE, the UE's state in the AMF will enter the CM-CONNECTED state. That is, the initial reception of an N2 message will initiate the transition of the UE state stored in the AMF from CM-IDLE to CM-CONNECTED. The AMF can maintain the UE connection state in CM-CONNECTED until the UE deregisters from the network, i.e., when the N2 context is released, the UE state stored in the AMF will transition from CM-CONNECTED to CM-IDLE.

[0043] In addition, a UE in CM-CONNECTED state can also be in RRC_INACTIVE state. In this state, the RAN releases the AN connection with the UE, and the UE moves within the area configured by the RAN. The N2 connection remains, and the UE's reachability is managed by the RAN based on auxiliary information provided by the network side. UE paging is managed by the RAN, and the UE listens for paging messages containing its corresponding network identifier (5G S-TMSI) and the RAN identifier. When the UE leaves the area configured by the RAN, it needs to notify the RAN. UE reachability management is responsible for detecting whether the UE is reachable and providing the network with the UE's location (i.e., access node) so that information sent by the network can reach the UE. This process is accomplished through paging the UE and UE location tracking. UE location tracking includes UE registration area tracking (i.e., UE registration area update) and UE reachability tracking (i.e., UE periodic registration area update). This function can be configured in 5GC (in CM-IDLE state) or NG-RAN (in CM-CONNECTED state). The UE and AMF negotiate the UE reachability characteristics in the CM-IDLE state during the registration process.

[0044] Whenever a UE in RM-REGISTERED state enters CM-IDLE state, the UE starts a periodic registration timer based on the periodic registration timer allocated by the AMF during the registration process. The UE needs to perform periodic registration upon the expiration of the periodic registration timer. If the UE moves out of network coverage when its periodic registration timer expires, the UE should perform the registration process upon its next return to coverage.

[0045] The AMF runs a mobile reachability timer for the UE. Whenever a UE in the RM-REGISTERED state changes its CM state to CM-IDLE, the timer starts with a value longer than the UE's periodic registration timer. If the AMF receives an elapsed time from the RAN when the RAN initiates a UE context release indicating the UE is unreachable, the AMF should derive the mobile reachability timer value based on the elapsed time received from the RAN and the normal mobile reachability timer value. If the UE's CM state in the AMF moves to the CM-CONNECTED state, the AMF stops the mobile reachability timer. If the mobile reachability timer expires, the AMF determines the UE is unreachable. When the mobile reachability timer expires, the AMF cannot know whether the UE is only temporarily unreachable, and therefore will not immediately register the UE. The AMF clears the paging processing indicator bit and starts the implicit deregistration timer only after the mobile reachability timer expires. If the UE becomes CM-CONNECTED before the timer expires, the AMF should stop the implicit registration timer and set the PPF. Otherwise, after the implicit registration timer expires, the AMF initiates the UE's privacy deregistration.

[0046] If the UE indicates the duration of the unavailability period, the AMF will consider the UE unreachable and will not trigger a paging procedure until the UE re-registers for normal service. Once the event causing the UE to become unavailable is completed or canceled within the UE, the UE will initiate a registration procedure to restore normal service. If the UE's CM state in the AMF is CM-IDLE, the AMF considers a UE in RM-REGISTERED to be reachable via CN paging, unless the UE applies MICO mode or the UE has indicated the duration of the unavailability period.

[0047] Figure 2 is a schematic flowchart of a communication method according to an embodiment of this application. The method includes at least a portion of the following.

[0048] S210. After the terminal sends a first merge registration request to the core network through the access network device corresponding to the second RAT to complete the merge registration of the first RAT and the second RAT, the terminal sends a first request to the first core network device through the access network device corresponding to the first RAT, wherein the first request is used to request to establish a connection with the first core network device through the access network device corresponding to the first RAT.

[0049] Figure 3 is a schematic flowchart of a communication method according to an embodiment of this application. The method includes at least a portion of the following.

[0050] S310. After the terminal sends a first merge registration request to the core network through the access network device corresponding to the second RAT to complete the merge registration of the first RAT and the second RAT, the first core network device receives the first request sent by the terminal through the access network device corresponding to the first RAT, wherein the first request is used to request to establish a connection with the first core network device through the access network device corresponding to the first RAT.

[0051] The type of RAT can be any of the following: E-UTRA (Evolved Universal Terrestrial Radio Access), NR terrestrial access, NR satellite access, 6G access, etc. NR terrestrial access can also be referred to as the transmission technology corresponding to the TN (Terrestrial Network) access network; NR satellite access can also be referred to as the transmission technology corresponding to the NTN access network. NR satellite access can include at least one of NR(LEO), NR(GEO), NR(LEO), etc.

[0052] The first RAT and the second RAT are RATs under different communication systems. That is, the first RAT can be a RAT under a first communication system, and the second RAT can be a RAT under a second communication system. The first and second communication systems are different. The first RAT corresponds to the first communication system or the core network of the first communication system, and the second RAT corresponds to the second communication system or the core network of the second communication system. For example, the first communication system can be a 5G system (5GS), that is, the first RAT can be a RAT under 5GS (such as NR terrestrial access or NR satellite access), and the second communication system can be a 6G system (6GS), that is, the second RAT can be a RAT under 6GS, or vice versa.

[0053] The process of the terminal sending a first merge registration request to the core network through the access network device corresponding to the second RAT to complete the merge registration of the first RAT and the second RAT may include: the terminal sending a first merge registration request to the core network through the access network device corresponding to the second RAT, wherein the first merge registration request is used to request the establishment of the terminal context for the terminal in the first RAT and the second RAT; the terminal receiving a first merge registration acceptance message from the core network through the access network device corresponding to the second RAT, wherein the first merge registration acceptance message is used for the terminal to determine that the merge registration of the first RAT and the second RAT is complete.

[0054] Optionally, the control plane network elements of the core networks of the first and second communication systems can be shared. For example, the first and second communication systems are 5GS and 6GS respectively, and 5GS and 6GS share the control plane network elements on the core network side.

[0055] In this scenario, the first core network device is a control plane network element shared by the core networks of both the first and second communication systems. The first core network device can be any one of the following: an MM (Mobility Management) network element, an AMF (Access and Mobility Management Function), etc.

[0056] Optionally, the control plane network elements on the core network side of the first communication system and the second communication system are set separately. The control plane network element on the core network side of the first communication system is the first core network equipment, and the control plane network element on the core network side of the second communication system is the second core network equipment. For example, if the first communication system and the second communication system are 5GS and 6GS respectively, the first core network equipment can be the AMF on the core network side of 5GS (i.e., 5GC), and the second core network equipment can be the MM network element (or simply 6G-MM or MM) on the core network side of 6GS (i.e., 6GC).

[0057] In some possible implementations, the control plane network elements of the core networks of the first and second communication systems are co-located.

[0058] In some embodiments, the device that processes the merged registration of terminals on the core network side is a first core network device.

[0059] The terminal sending the first merged registration request to the core network through the access network device corresponding to the second RAT is as follows: the terminal sending the first merged registration request to the first core network device through the access network device corresponding to the second RAT. The terminal receiving the first merged registration acceptance message from the core network through the access network device corresponding to the second RAT specifically involves the terminal receiving the first merged registration acceptance message from the first core network device through the access network device corresponding to the second RAT.

[0060] Accordingly, the processing of the first core network device may include: the first core network device receiving a first merge registration request sent by the terminal through the access network device corresponding to the second RAT, wherein the first merge registration request is used to request the establishment of the terminal context for the terminal under the first RAT and the second RAT; the first core network device sending a first merge registration acceptance message to the terminal through the access network device corresponding to the second RAT, wherein the first merge registration acceptance message is used for the terminal to determine that the merge registration of the first RAT and the second RAT has been completed.

[0061] Before the terminal sends the first merge registration request to the first core network device through the access network device corresponding to the second RAT, the process may further include: the terminal establishing a connection with the access network device corresponding to the second RAT. The connection established between the terminal and the access network device corresponding to the second RAT may be an RRC (Radio Resource Control) connection.

[0062] The terminal sends a first merged registration request to the first core network device through the access network device corresponding to the second RAT, which may include: the terminal sending the first merged registration request to the access network device corresponding to the second RAT, and the access network device corresponding to the second RAT forwarding the first merged registration request to the first core network device.

[0063] The first merged registration request may carry at least one of the following: the identifier of the terminal, the registration type, the type of the first RAT, the identifier of the access network device corresponding to the first RAT, the tracking area information corresponding to the first RAT, and the identifier of the cell corresponding to the access network device corresponding to the first RAT.

[0064] The terminal identifier can be of at least one of the following types: SUPI (Subscription Permanent Identifier), SUCI (Subscription Concealed Identifier), or GUTI (Globally Unique Temporary Identifier). The terminal's GUTI can be a GUTI currently stored by the terminal, such as the GUTI assigned to the terminal by the network side (e.g., the core network) during its last network access.

[0065] The registration type carried in the first merged registration request can be merged registration. By carrying the registration type of merged registration in the first merged registration request, it can indicate at least one of the following: the first merged registration request is for merged registration of the terminal under multiple RATs, the first merged registration request is for merged registration of the terminal in multiple communication systems, and the first merged registration request is for merged registration of the terminal in the core networks corresponding to multiple communication systems.

[0066] The type of the first RAT can be used to indicate other access types that are merged and registered with the second RAT. For example, if the current second RAT is a 6G access type, the type of the first RAT can be a 4G access type (such as E-UTRAN) or a 5G access type (such as NR), etc. Or, if the current second RAT is a 5G access type, the type of the first RAT can be a 4G access type or a 6G access type, etc.

[0067] The identifier of the access network device corresponding to the first RAT can be obtained by the terminal through broadcast information (such as broadcast information sent by the access network device corresponding to the first RAT). The specific method of obtaining it is not limited in this embodiment.

[0068] The tracking area information corresponding to the first RAT can refer to the tracking area information corresponding to the access network device corresponding to the first RAT. This tracking area information can be a list of tracking areas. The terminal obtains this tracking area information from the TAC (Tracking Area Code) in broadcast information (such as broadcast information sent by the access network device corresponding to the first RAT).

[0069] The identifier of the cell corresponding to the access network device of the first RAT can also be obtained by the terminal through broadcast information (such as broadcast information sent by the access network device corresponding to the first RAT), and there is no limitation on the specific method of obtaining it.

[0070] This is merely an illustrative example of the content that the first merged registration request may carry. In actual processing, the first merged registration request may also carry other content, such as the terminal's capability information, which can be used to indicate whether the terminal supports multi-access capability (or whether the terminal supports multi-access).

[0071] Multi-access capability can include the ability to access the core network through multiple RATs. Multi-access can also be called dual access, dual radio, or multiple connections, etc. Among them, dual radio can refer to the terminal simultaneously exchanging data or signaling with the network through two access network devices (or the access network devices corresponding to two RATs).

[0072] Specifically, the ability to access the core network through multiple RATs can be defined as the ability to access the core network through the access network devices corresponding to each of the multiple RATs. For terminals with multi-access capabilities, the terminal can connect to the core network through multiple access network devices of multiple RATs. On the core network side, control plane network elements and different access network devices can each have a connection corresponding to the terminal. Furthermore, the signaling transmission of the terminal on multiple access network devices is independent of each other. The connection between any access network device corresponding to the terminal and the control plane network element can be an NGAP (Next Generation Application Protocol) connection.

[0073] Multiple access or multiple connections refer to a single terminal having multiple connections to one or more core networks. Each connection connects to the core network through different access network devices (or access network devices corresponding to different RATs) and registers with the same or different networks. The connection primarily refers to the NAS connection between the terminal and the core network.

[0074] Furthermore, multiple access terminals can communicate with the core network simultaneously via multiple access network devices. On each access network device, the terminal can connect to the core network through different access network devices (or access network devices corresponding to different RATs). That is, the RRC connection, NGAP connection, and NAS connection of the terminal and the core network on each access network device are unique to that device and different from the other access network devices. In addition, the terminal can also establish different sessions on different access network devices to receive or send service data. In other words, the terminal can establish multiple sessions simultaneously through multiple access network devices (or access network devices corresponding to multiple RATs).

[0075] In this embodiment of the application, the terminal may or may not support multiple access capabilities, and no limitation is made here.

[0076] After the first core network device receives the first merged registration request, the terminal and the network side can perform two-way authentication. The network side participating in the two-way authentication of the terminal may include at least one of the first core network device, UDM (Unified Data Management), AUSF (Authentication Server Function), etc. This embodiment does not limit the network elements of the network side participating in the two-way authentication of the terminal, nor the processing of the two-way authentication between the terminal and the network side.

[0077] After two-way authentication is completed between the terminal and the network side, the first core network device and the terminal can establish a NAS security context through the NAS (Non-Access Stratum) SMC (Security Mode Command) procedure. For example, the first core network device can send the NAS security context to the terminal through the NAS SMC, and the first core network device receives a NAS Security Mode Complete message from the terminal; correspondingly, the terminal receives the NAS security context sent by the first core network device through the NAS SMC, and the terminal sends a NAS Security Mode Complete message to the first core network device.

[0078] This NAS security context is used to protect NAS signaling transmitted between the terminal and the first core network device. This protection includes encryption and / or integrity protection. Specifically, the NAS security context may include at least one of the following: a NAS layer integrity protection (hereinafter referred to as integrity protection) key, a NAS layer encryption key, a NAS layer integrity protection algorithm, a NAS layer encryption algorithm, etc.

[0079] In this embodiment, the first core network device is a control plane network element in the core network shared by the first communication system and the second communication system. Therefore, the NAS security context can be used to protect the NAS signaling transmitted between the terminal under the second RAT and the first core network device, and also to protect the NAS signaling transmitted between the terminal under the first RAT and the first core network device.

[0080] After the first core network device and the terminal establish a NAS security context through the NAS SMC procedure, and before the first core network device sends a first merge registration acceptance message to the terminal through the access network device corresponding to the second RAT, the method further includes: the first core network device sending a registration message to the UDM, wherein the registration message is used to record at least one of the following in the UDM: the first core network device serves the terminal, and merges the associated first RAT and second RAT.

[0081] Specifically, the process of the first core network device sending a registration message to the UDM may include: the first core network device establishing a terminal context (UE Context) under the first RAT and the second RAT, sending a registration request to the UDM, and the registration message being used to record at least one of the following in the terminal context stored in the UDM: the first core network device serving the terminal, merging the registration associated first RAT and second RAT.

[0082] The terminal contexts established on the first core network equipment side under the first RAT and the second RAT may include: the terminal context under the first RAT, the terminal context under the second RAT; or, the context of a terminal shared by the first RAT and the second RAT.

[0083] The first core network device serving the terminal can refer to the first core network device being a mobility management network element serving the terminal; or the first core network device being a mobility management network element serving the terminal and establishing a terminal context under the first RAT and the second RAT.

[0084] The first RAT and the second RAT associated with the merged registration can also be referred to as the associated access type. Specifically, it can refer to the access type associated with the terminal merged registration being the first RAT and the second RAT.

[0085] The registration message may carry at least one of the following: terminal identifier, registration type, identification information of the first core network device, first RAT, and second RAT. The registration type may include merged registration. The identification information of the first core network device may include at least one of the following: the ID of the first core network device, the name of the first core network device, the IP (Internet Protocol) address of the first core network device, the MAC (Media Access Control) address of the first core network device, the FQDN (Fully Qualified Domain Name) of the first core network device, etc.

[0086] For example, when the registration message carries the identification information of the first core network device, it can be used to associate the identification information of the first core network device with the terminal in the UDM, and record the first core network device as a mobility management network element (or control plane network element) serving the terminal in the terminal context stored in the UDM.

[0087] For example, when the registration message carries a first RAT and a second RAT, it can be used to associate the terminal, the first RAT, and the second RAT in the UDM, and record in the terminal context stored in the UDM that the RAT type associated with the terminal in this merge registration is the first RAT and the second RAT.

[0088] Optionally, after the first core network device and the terminal establish a NAS security context through the NAS SMC process, the first core network device can determine whether merged registration is supported. If merged registration is supported, the device can send a registration message to the UDM. Then, the first core network device sends a first merged registration acceptance message to the terminal through the access network device corresponding to the second RAT.

[0089] The process by which the first core network device determines whether merged registration is supported can include: the first core network device determining whether merged registration is supported based on at least one of the following: local configuration, terminal subscription data, network capabilities, and operator configuration. The terminal's subscription information can be obtained from the UDM; local configuration can include whether the first core network device itself can provide relevant configurations for merged registration; network capabilities can include the capabilities of the network where the first core network device is located (e.g., the core network side), which can include whether merged registration is supported, etc. The network capabilities are not limited or exhaustively listed here. This embodiment does not limit the specific processing method by which the first core network device determines whether merged registration is supported based on at least one of the following: local configuration, terminal subscription data, network capabilities, and operator configuration.

[0090] Optionally, after sending a registration message to the UDM, the first core network device may determine whether merged registration is supported. If merged registration is supported, the device may execute the process of sending a first merged registration acceptance message to the terminal through the access network device corresponding to the second RAT.

[0091] The first merged registration acceptance message carries at least one of the following: registration type, NAS identifier for paging corresponding to the second RAT, NAS identifier for paging corresponding to the first RAT, NAS identifiers for paging corresponding to the first RAT and the second RAT, registration area corresponding to the second RAT, registration area corresponding to the first RAT, registration areas corresponding to the first RAT and the second RAT, and the registration status of the terminal in the first RAT.

[0092] That is, the parameters or information types that the first merged registration acceptance message may carry may include at least one of the following: registration type, NAS identifier for paging, registration area, and the terminal's registration status in the first RAT.

[0093] The registration type carried in the first merge registration acceptance message can be merge registration.

[0094] The NAS identifier used for paging can be a NAS identifier assigned to the terminal by the first core network device for paging the terminal. The type of the NAS identifier used for paging can be GUTI or TMSI (Temporary Mobile Subscription Identifier). The TMSI can be obtained by truncating the GUTI. The specific truncating method is not limited in this embodiment.

[0095] Preferably, the NAS identifier assigned by the first core network device to the terminal for paging can be the paging NAS identifier corresponding to the first RAT and the second RAT. That is, the first core network device can assign the same paging NAS identifier to the terminal under both the first and second RATs. In this way, the first core network device associates the terminal's context (terminal context) under the first and second RATs with the same paging NAS identifier across different communication systems or networks. This avoids redundancy caused by the first core network device storing different paging NAS identifiers in different communication systems or networks, and also avoids the waste of computing power caused by mapping the paging NAS identifier when the terminal switches between different systems.

[0096] Optionally, the NAS identifier assigned by the first core network device to the terminal for paging may include the NAS identifier for paging corresponding to the second RAT and the NAS identifier for paging corresponding to the first RAT. That is, the first core network device may assign different NAS identifiers for paging the terminal under the first RAT and the second RAT respectively.

[0097] The registered area may include a list of TAIs (Tracking Area Identity), which may include one or more TAIs.

[0098] Preferably, the registration area allocated by the first core network device to the terminal can be the registration area corresponding to the first RAT and the second RAT. That is, the first core network device can allocate a registration area for the terminal under both the first RAT and the second RAT.

[0099] Optionally, the registration area allocated by the first core network device to the terminal may include the registration area corresponding to the second RAT and the registration area corresponding to the first RAT. That is, the first core network device may allocate registration areas to the terminal under the first RAT and the second RAT respectively. The registration areas corresponding to the first RAT and the registration areas corresponding to the second RAT may be partially different, partially the same, or completely different, and this embodiment does not impose any limitations.

[0100] The terminal's registration status in the first RAT can be used to indicate whether the terminal is allowed to register with the first RAT via the second RAT. For example, the terminal's registration status in the first RAT may include a "registered" status, indicating that the first core network device accepts the terminal's registration with the first RAT via the second RAT and that the registration on the first RAT was successful. Conversely, if the terminal's registration status in the first RAT is "de-registering," it indicates that the first core network device does not accept the terminal's registration with the first RAT via the second RAT and / or that the registration on the first RAT failed.

[0101] It should be noted that the above is only an illustrative example. In actual processing, the first merged registration acceptance message may also carry other content. For example, the first merged registration acceptance message may also carry a network capability indication, which is used to indicate whether the network supports the terminal to perform multiple access (or dual radio). Here, we will not limit or exhaust all the contents that the first merged registration acceptance message may carry.

[0102] In this embodiment, after the first core network device accepts the merged registration of the terminal, it can maintain a connection state for the terminal, that is, the terminal and the first core network device are in a connected state, and it does not distinguish whether the connection state corresponds to the first RAT or the second RAT; or, after the first core network device accepts the merged registration of the terminal, it can maintain different connection states for the terminal on different RATs, for example, the terminal is in a connected state on the second RAT and in an idle state on the first RAT.

[0103] In other words, since the access network devices corresponding to different RATs are managed by the same control plane network element (such as the MM network element), i.e., the first core network device, one of the following two situations can exist:

[0104] Scenario 1: The terminal maintains a single connection state with the first core network device across multiple RATs (e.g., the first RAT and the second RAT). For example, in 6G and 5G, there is only one connection state. In this case, the terminal is considered to be in a connected state as long as there is at least one NAS connection between it and the first core network device.

[0105] Scenario 2: The terminal maintains multiple connection states with the first core network equipment across multiple RATs. For example, there is one connection state in 6G and another in 5G. The terminal operates independently in each of the different RAT connection states.

[0106] In addition, depending on whether the terminal and / or the first core network device support multiple access, the terminal can be in one of the following two modes: Dual radio: The terminal can connect to the core network through two access network devices at the same time and interact with the core network for data and / or signaling; Single radio: The terminal can only connect to the core network through one access network device at the same time and interact with the core network for data and / or signaling.

[0107] Furthermore, after the access network device corresponding to the second RAT forwards the first merged registration acceptance message to the terminal, the access network device corresponding to the second RAT can also negotiate access layer security parameters with the terminal through the AS (Access Layer) SMC procedure. The access layer security parameters may include at least one of the following: RRC encryption key, RRC integrity key, RRC encryption algorithm, RRC integrity algorithm, user plane encryption key, user plane integrity key, user plane encryption algorithm, and user plane integrity algorithm.

[0108] Additionally, if the first core network device determines that merged registration is not supported, the method may further include: the first core network device sending a first merged registration rejection message to the terminal. This first merged registration rejection message may carry at least one of the following: the terminal's identifier, a reason for rejection, etc. This first merged registration rejection message is used by the terminal to determine that the first core network device does not support merged registration. The reason for rejection can be configured according to actual circumstances and is not limited here.

[0109] It should also be noted that the above is mainly an exemplary description of the terminal connecting to the first core network device through two RATs for merged registration. In actual processing, the UE can also connect to the first core network device through more RATs for merged registration. For example, the UE can also request the establishment of the terminal context for the terminal in the first RAT, the second RAT, and the third RAT through the first merged registration request. After the merged registration is completed, the UE can also be in an idle state on the third RAT. The relevant processing for the third RAT can also be the same as that for the first RAT. It will not be exhaustively listed or elaborated here, and will not be repeated below.

[0110] Referring to Figure 4, taking the example of two communication systems sharing a single mobility management network element in their core networks, the process of terminal merging registration is illustrated as follows:

[0111] Step 400: The UE (i.e., the terminal) establishes a connection with the 6G-RAN (Radio Access Network) (the access network device corresponding to the second RAT in the aforementioned embodiment), for example, an RRC connection. The establishment of an RRC connection between the UE and the 6G access network device can be achieved through an RRC connection establishment procedure; this example does not limit the specific processing of this procedure.

[0112] Step 401: The UE initiates a first combined registration request through the 6G-RAN to the mobility management network element (simply illustrated as MM in Figure 4) (i.e., the first core network device in the aforementioned embodiment). The combined registration request includes the following information:

[0113] UE identification information, such as SUPI, SUCI, GUTI, etc.;

[0114] The registration type, in this example, can specifically be combined registration. When the registration type is combined registration, it can be used to indicate at least one of the following: the registration request is used to perform combined registration of the UE under multiple access (RAT); the registration request is used to perform combined registration of the UE in a communication system, such as combined registration in 5GS and 6GS; the registration request is used to perform combined registration of the UE in multiple core networks, such as combined registration in 5GC and 6GC.

[0115] Information used to indicate other access types (RAT types) that are merged and registered with the current access type (i.e., the type information of the first RAT in the aforementioned embodiments), such as 4G access type E-UTRA(N), 5G access type NR, or 6G access type;

[0116] The target TAI (i.e., the tracking area information corresponding to the first RAT in the aforementioned embodiments) is used to indicate the TAI corresponding to another access network 5G-RAN (i.e., the access network device corresponding to the first RAT), and can be obtained through the TAC in the broadcast message;

[0117] The target cell ID (i.e., the identifier of the cell corresponding to the access network device corresponding to the first RAT in the aforementioned embodiment) is used to indicate the cell ID broadcast by another access network 5G-RAN;

[0118] The 5G-RAN ID can be obtained from the 5G-RAN broadcast information;

[0119] The UE's capability information can indicate whether the UE supports multiple access or whether the UE supports dual radio.

[0120] Step 402: The UE performs two-way authentication with the network.

[0121] Step 403: Establish a NAS security context between the MM and the UE through the NAS SMC procedure for encryption and / or integrity protection of signaling messages between the UE and the MM.

[0122] Step 404: The MM is registered with the UDM. The MM ID and associated access type are recorded in the UE context on the UDM. Recording the MM ID in the UDM's UE context allows the MM to be registered as a mobility management element serving the UE. Recording the associated access type in the UDM's UE context allows for the merging of associated access types in the registration record. In this example, the associated access types include 5G access (i.e., the first RAT) and 6G access (i.e., the second RAT).

[0123] It should be noted that the MM may perform the registration to the UDM process upon determining that the UE's first merge registration request has been accepted.

[0124] Step 405, the MM sends a first merge registration acceptance message to the UE, which may carry at least one of the following:

[0125] The NAS identifier used for paging, such as GUTI, can also be called the NAS identifier used for paging the UE. In this example, the NAS identifier used for paging can be the same in both communication systems.

[0126] The registration area can include the TAI list corresponding to 5G access and / or the TAI list corresponding to 6G access;

[0127] The UE's registration status on the 5G access (i.e., the first RAT) is used to indicate whether the network side accepts the UE's registration on one access to another access through one access. If the registration status is "registered", the UE is considered to have successfully registered on the 5G access (i.e., the first RAT). If the registration status is "failed to register", the UE is considered to have failed to register on the 5G access (i.e., the first RAT).

[0128] Network capability indication is used to indicate whether the network supports multiple access for the UE or whether the network supports dual radio for the UE (i.e., whether the UE can simultaneously interact with the network through two access network devices for data or signaling).

[0129] Specifically, the MM can determine whether merged registration is supported based on at least one of the following: local configuration, UE subscription data, and network capabilities. If supported, step 405 is executed. If not supported, the MM sends a first merged registration rejection message to the UE. The rejection message includes the UE identifier and a rejection cause, which can be used to indicate that the MM does not support merged registration.

[0130] Step 406: The 6G-RAN negotiates with the UE, through the AS SMC procedure, the algorithms and keys for encryption and / or integrity protection of RRC and user plane.

[0131] It should be noted that if the MM maintains a connection state for the UE, then after step 405, the UE and the UE on the MM are in a connected state; if the MM maintains different connection states for the UE on different access points, then after step 405, the UE is in a connected state on the 6G access point (i.e., the second RAT in the aforementioned embodiment) and in an idle state on the 5G access point (i.e., the first RAT in the aforementioned embodiment). The UE listens for paging messages of the 5G-RAN in the registered area, or the UE listens for paging messages under the TAI list corresponding to the 5G access point in the registered area.

[0132] In addition, after a period of time, the UE can enter an idle state on both legs (i.e., the first RAT and the second RAT) and listen for paging messages throughout the registered area.

[0133] Optionally, when the UE is in an idle state on both legs (i.e., the first RAT and the second RAT), the UE can prioritize listening for paging messages in the registration area (or the TAI list included in that registration area) corresponding to the highest priority access (RAT) between the first RAT and the second RAT (e.g., 5G access and 6G access). The priority of the first RAT and the second RAT can be determined according to the actual configuration. For example, the UE can choose the RAT that was most recently camped between the first RAT and the second RAT as the highest priority access; another example is that the UE pre-configures the priorities of multiple RATs, and determines the highest priority RAT between the first RAT and the second RAT based on the priorities of these multiple RATs, and so on. This approach is particularly suitable for scenarios where the UE can only camp on one cell at a time.

[0134] By adopting the above embodiments, the first core network device uses the same NAS identifier for paging to associate the terminal's context (terminal context) under the first RAT and the second RAT in different communication systems or networks. This avoids the redundancy caused by the first core network device storing different NAS identifiers for paging in different communication systems or networks, and also avoids the problem of wasted computing power caused by mapping the NAS identifier for paging when the terminal switches between different systems. Assigning the terminal the registration area corresponding to the RAT under different communication systems also avoids mobility registration caused by the terminal switching RATs, reducing the signaling load on the air interface. Finally, after the terminal is merged and registered, it is in an idle state in the core network (corresponding RAT) without a NAS connection to the terminal. Once the core network has downlink signaling messages / data, it can directly page the terminal without waiting for the terminal to register with the core network first before sending downlink signaling / data. This facilitates the management of the terminal by the core network side of multiple communication systems or networks, and also allows the application server to quickly switch the required core network to provide downlink service data to the terminal.

[0135] In one embodiment, after the terminal sends a first merge registration request to the core network through the access network device corresponding to the second RAT to complete the merge registration of the first RAT and the second RAT, the terminal can directly send a first request to the first core network device through the access network device corresponding to the first RAT when the first RAT is in an idle state and the terminal has uplink data or uplink signaling (messages) that need to be sent to the core network through the access network device corresponding to the first RAT.

[0136] In this embodiment, the terminal and the first core network device can support dual access (or dual radio), that is, the terminal can connect to the core network through two access network devices at the same time and interact with the core network for data and / or signaling. Therefore, the terminal does not need to disconnect the connection between the access network device corresponding to the second RAT and the first core network device. Instead, the terminal directly sends a first request to the first core network device through the access network device corresponding to the first RAT to establish a connection with the first core network device through the access network device corresponding to the first RAT.

[0137] The first request can be a service request message, or it can be other types of messages such as redirection request messages. The specific message type of the first request is not limited here.

[0138] The first request may carry at least one of the following: a NAS identifier for paging corresponding to the first RAT; NAS identifiers for paging corresponding to the first RAT and the second RAT; an identifier of a first session, wherein the first session is a session that the terminal requests to activate on the first RAT, or the first session is a session that switches from the second RAT to the first RAT.

[0139] Here, if the first merged registration acceptance message carries the NAS identifier for paging corresponding to the first RAT and the NAS identifier for paging corresponding to the second RAT, then the first request carries the NAS identifier for paging corresponding to the first RAT.

[0140] The first session can be determined by the terminal based on the actual situation. For example, if the terminal has uplink data that needs to be transmitted through a session under the first RAT, then the session needs to be activated in the first RAT, and this session can be the first session. The methods by which the terminal determines the first session are not limited or exhaustively listed here.

[0141] Optionally, if the first request only carries the NAS identifier for paging corresponding to the first RAT or the NAS identifier for paging corresponding to both the first RAT and the second RAT, then the first request can be used to request the establishment of a NAS connection between the access network device corresponding to the first RAT and the first core network device.

[0142] After receiving the first request, the first core network device can establish a NAS connection with the terminal through the access network device corresponding to the first RAT. Then, the terminal can transmit uplink NAS signaling to the first core network device and / or receive downlink NAS signaling through this NAS connection. This embodiment does not limit the specific method by which the first core network device establishes a NAS connection with the terminal through the access network device corresponding to the first RAT.

[0143] Optionally, if the first request carries only the NAS identifier for paging corresponding to the first RAT or the NAS identifiers for paging corresponding to the first RAT and the second RAT, and the first request carries the identifier of the first session; then the first request can be used to request the establishment of a NAS connection between the access network device corresponding to the first RAT and the first core network device, and to request the establishment of user plane resources corresponding to the first RAT for transmitting the data to be transmitted in the first session.

[0144] After receiving the first request, the first core network device can establish a NAS connection with the terminal through the access network device corresponding to the first RAT, and control the establishment of user plane resources through the access network device corresponding to the first RAT. Then, the terminal can transmit uplink data and / or receive downlink data of the first session through the user plane resources. This embodiment does not limit the specific method by which the first core network device establishes a NAS connection with the terminal through the access network device corresponding to the first RAT, and controls the establishment of user plane resources.

[0145] In one embodiment, after the terminal sends a first merge registration request to the core network through the access network device corresponding to the second RAT to complete the merge registration of the first RAT and the second RAT, the terminal can be in an idle state when the first RAT is idle. If the terminal has uplink data or uplink signaling (messages) that need to be sent to the core network through the access network device corresponding to the first RAT, the terminal first disconnects the connection between the access network device corresponding to the second RAT and the first core network device, and then sends a first request to the first core network device through the access network device corresponding to the first RAT to establish a connection with the first core network device through the access network device corresponding to the first RAT.

[0146] This embodiment can be applied to scenarios where the terminal and the first core network device do not support dual access, i.e., the terminal connects to the core network through an access network device at the same time, or it can be applied to scenarios where the UE is interworking between systems (such as the first communication system and the second communication system).

[0147] Before the terminal sends a first request to the first core network device through the access network device corresponding to the first RAT, the method further includes: when the terminal is in a connected state with the second RAT, the terminal receives an RRC release message from the access network device corresponding to the second RAT, wherein the RRC release message is used to indicate the release of the RRC connection between the terminal and the access network device corresponding to the second RAT. Furthermore, before the terminal receives the RRC release message from the access network device corresponding to the second RAT, the method further includes: the terminal sending first indication information, wherein the first indication information is used to indicate the release of the connection between the terminal and the core network through the access network device corresponding to the second RAT.

[0148] The first indication information can be used to indicate the release of the connection between the terminal and the first core network device through the access network device corresponding to the second RAT. Specifically, the first indication information can indicate at least one of the following: the reason for the terminal leaving the connected state (or switching from the connected state to the idle state) under the second RAT is to switch to a new core network, or the terminal connecting to the core network (i.e., the first core network device) through the access network device corresponding to the new RAT (such as the first RAT).

[0149] Before the first core network device receives the first request sent by the terminal through the access network device corresponding to the first RAT, the method further includes: when the terminal is in a connected state with the second RAT, the first core network device sends a release command to the access network device corresponding to the second RAT, wherein the release command is used to instruct the access network device corresponding to the second RAT to release the terminal-related resources. Before the first core network device sends the release command to the access network device corresponding to the second RAT, the method further includes: the first core network device receiving first indication information from the terminal, wherein the first indication information is used to instruct the release of the connection between the terminal and the first core network device through the access network device corresponding to the second RAT.

[0150] That is, when the second RAT is in the connected state, the terminal first sends a first indication message, then receives an RRC release message from the access network device corresponding to the second RAT, and then sends a first request to the first core network device through the access network device corresponding to the first RAT.

[0151] Optionally, the terminal sending the first indication information can specifically involve: the terminal sending an Access Layer AS message to the access network device corresponding to the second RAT, the AS message carrying the first indication information. The processing by the access network device corresponding to the second RAT can be: the access network device receiving the first indication information from the terminal, and the access network device forwarding the first indication information to the first core network device. The first core network device receiving the first indication information from the terminal includes: the first core network device receiving the first indication information forwarded by the access network device corresponding to the second RAT.

[0152] In addition to carrying the first instruction information, the AS message may also carry the terminal's identifier.

[0153] Specifically, the AS message can be an RRC message, and the first indication information and the terminal identifier can be carried by the IE (Information Element) in the RRC signaling message. For example, the RRC message can be UE Assistance Information, and the first indication information and the terminal identifier are carried in the preference to transition out of RRC_CONNECTED IE in the UE Assistance Information.

[0154] The first indication information (and the terminal identifier) ​​forwarded by the access network device corresponding to the second RAT to the first core network device can be carried by the UE Context Release Request.

[0155] The UE context release request can be used to request the first core network device to release the second connection between the access network device corresponding to the second RAT and the first core network device for transmitting NAS messages (or signaling) corresponding to the terminal. This second connection is the logical NG (next-generation) connection associated with the terminal.

[0156] Specifically, in addition to carrying the first indication information, the UE context release request may also carry at least one of the following: the NGAP ID of the terminal corresponding to the first core network device, the NGAP ID of the terminal corresponding to the access network device corresponding to the second RAT, the release reason, and a list of sessions carried on the access network device corresponding to the second RAT that need to be released. The NGAP ID of the terminal corresponding to the first core network device can also be referred to as the identifier of the core network side (or the first core network device side) corresponding to the second connection, and the NGAP ID of the terminal corresponding to the access network device corresponding to the second RAT can also be referred to as the identifier of the access network device side corresponding to the second RAT corresponding to the second connection.

[0157] The release reason can be configured according to the actual situation, such as a reason value or reason description information.

[0158] After receiving the first indication information, the first core network device can send a release command to the access network device corresponding to the second RAT. The release command can be UE CONTEXT RELEASE COMMAND (UE context release command) or other command types. Here, we will not limit or exhaust all possible names of the release command.

[0159] After the first core network device sends a release command to the access network device corresponding to the second RAT, the terminal on the first core network device side can be in an idle state in the second RAT (or the access network device corresponding to the second RAT).

[0160] Correspondingly, after receiving the release command, the access network device corresponding to the second RAT can release the resources related to the terminal, such as releasing signaling and user data transmission resources (or user plane resources); then the access network device corresponding to the second RAT sends an RRC release message to the terminal.

[0161] The RRC release message may carry at least one of the following: a core network type parameter, wherein the core network type parameter is used to indicate the core network type to which the terminal switches; and second indication information, wherein the second indication information is used to indicate that the terminal switches to connecting to the core network through the access network device corresponding to the first RAT.

[0162] The core network type parameter can be represented as cnType. For example, this core network type parameter can be the core network of the first communication system corresponding to the first RAT. In other words, the core network type parameter allows the terminal to determine that the reason for this RRC release is a switch from accessing the shared core network through the second RAT under the second communication system to accessing the shared core network through the first RAT under the first communication system. For instance, if the core network of the second communication system corresponding to the second RAT is 6GC, then this core network type parameter can be the core network of the first communication system (such as EPC, 5GC, or any one of them).

[0163] The second indication information is used to instruct the terminal to switch to connect to the core network through the access network device corresponding to the first RAT. This can mean that the second indication information is used to indicate at least one of the following: the reason for the terminal switching from the connected state under the second RAT to the idle state is that the terminal is switching to a new core network; or the reason for the terminal switching from the connected state under the second RAT to the idle state is that the terminal accesses the core network (i.e., the first core network device) through the access network device corresponding to the first RAT.

[0164] Optionally, the terminal sending the first indication information can specifically involve: the terminal sending a NAS message to the first core network device through the access network device corresponding to the second RAT, the NAS message carrying the first indication information. The first core network device receiving the first indication information from the terminal includes: the first core network device receiving the NAS message carrying the first indication information from the terminal through the access network device corresponding to the second RAT.

[0165] In addition to carrying initial instructions, the NAS message can also carry the terminal's identifier.

[0166] After receiving the NAS message carrying the first indication information, the first core network device can send a release command to the access network device corresponding to the second RAT. Correspondingly, after receiving the release command, the access network device corresponding to the second RAT can release the resources related to the terminal, such as releasing signaling and user data transmission resources (or user plane resources); then, the access network device corresponding to the second RAT sends an RRC release message to the terminal.

[0167] The descriptions of the release command and RRC release message are the same as those in the previous embodiments and will not be repeated.

[0168] After the terminal receives the RRC release message from the access network device corresponding to the second RAT, it can send a first request to the first core network device through the access network device corresponding to the first RAT.

[0169] The content carried in the first request is the same as in the aforementioned embodiments, and will not be repeated. The processing of the first core network device after receiving the first request is also the same as in the aforementioned embodiments, and will not be described again.

[0170] Based on Figure 4, and in conjunction with Figure 5, we will exemplify how, after the UE performs merged registration through 6G-RAN (i.e., the access network device corresponding to the second RAT), if there is uplink data or signaling message that needs to be sent to the core network through 5G-RAN (i.e., the access network device corresponding to the first RAT), the UE can establish a NAS connection with the MM on 5G-RAN through a service request procedure.

[0171] In step 500, the UE performs merged registration through 6G-RAN and successfully registers in both 5GC and 6GC. The MM successfully establishes a UE context for the UE (i.e., the MM establishes a UE context for the UE under both 5G RAT (i.e., the first RAT) and 6G RAT (i.e., the second RAT)). The specific processing of step 500 includes steps 400 to 406 as shown in Figure 4 above, which will not be elaborated here.

[0172] If the UE is in a connected state in the 6G system, the UE notifies the network to release its connection on the 6G-RAN. For example, multiple access UEs can only access one access network at a time, or when the UE is interworking between systems, it needs to release the connection with the old network before establishing a NAS connection with the target network. The UE can notify the network to switch from the connected state (CM-CONNECTED) to the idle state (CM-IDLE) in the 6G RAT (i.e., the second RAT in the aforementioned embodiment) in the following two ways:

[0173] Method 1: Notify the network through the AS layer, specifically by executing the following steps 501 to 502:

[0174] Step 501: The UE notifies the 6G-RAN via an RRC message that it has switched to the access network device corresponding to another RAT and needs to leave the RRC-CONNECTED state. The RRC message may be UE Assistance Information.

[0175] The RRC message may carry at least one of the following: UE identification information and first indication information; wherein, the first indication information is used to indicate that the UE needs to leave the connected state of 6G RAT (or switch from the connected state to the idle state) because it has switched to a new core network, such as switching from 6GS to 5GS, or from 5GS to 6GS; or the first indication information is used to indicate that the UE needs to connect to the core network through a new access network device, such as switching from 6G-RAN to core network 6GC to 5G-RAN to core network 6GC. The first indication information may be an IE carried in the RRC signaling message, such as preference to transition out of RRC_CONNECTED in UE Assistance Information.

[0176] Step 502: The 6G-RAN sends a UE context release request to the MM to request the release of the connection corresponding to the UE (such as the UE-associated logical NG-connection corresponding to the UE), and then executes step 503.

[0177] The UE context release request includes at least one of the following parameters:

[0178] MM UE NGAP ID (i.e., the NGAP ID of the terminal corresponding to the first core network device in the aforementioned embodiments);

[0179] RAN UE NGAP ID (i.e., the NGAP ID of the terminal corresponding to the access network device corresponding to the second RAT in the aforementioned embodiment);

[0180] The PDU Session Resource List is used to indicate a list of sessions carried on the 6G-RAN that need to be released.

[0181] The cause (i.e., the release cause in the aforementioned embodiments) can be an existing cause value. For example, the release cause may include TXnRELOCOverall Expiry or redirection as specified in the relevant protocol, or the release cause may be a newly defined cause value, such as interworking, etc. The release causes are not limited or exhaustively listed here.

[0182] Method 2: Notify the network via NAS layer message. Specifically, the UE sends a NAS message to the MM via 6G-RAN, and then executes step 503. The UE sending the NAS message to the MM via 6G-RAN can be done by the UE sending the NAS message to the 6G-RAN, and the 6G-RAN forwarding the received NAS message to the MM.

[0183] Here, the NAS message can be used to notify or instruct the MM that the UE needs to leave its current connected state (CM-CONNECTED) and switch to the access network device corresponding to another RAT under the 6G RAT. The NAS message can carry at least one of the following: UE identification information, and first indication information; the first indication information can be an IE carried in the NAS message, such as the Release Request Indication in a service request or registration request.

[0184] Step 503: The MM sends a UE context release command (i.e., the release command in the aforementioned embodiment) to the 6G-RAN. The 6G-RAN releases all signaling and user data transmission resources. The UE on the MM enters an idle state under the 6G RAT.

[0185] Step 504: The 6G-RAN sends an RRC release message to the UE to release the RRC connection between the UE and the UE. The UE then enters or switches from the connected state to the idle state under the 6G RAT.

[0186] Step 505: The UE sends a service request message (i.e., the first request in the aforementioned embodiment) to the MM via the 5G-RAN, establishing a NAS connection with the MM on the 5G-RAN for sending NAS messages to or receiving NAS messages from the MM. Subsequently, the UE can send a session establishment message to the Session Management Element (SMF) on the 5G-RAN to establish user plane resources for user data transmission. The service request process includes at least one of the following parameters: UE identification information, and the PDU session identifier to be activated (i.e., the identifier of the first session in the aforementioned embodiment).

[0187] Specifically, if the MM assigns the same NAS identifier for paging to the UE under both 5G RAT and 6G RAT during the merged registration, then the UE identification information is the NAS identifier for paging corresponding to the 5G RAT and 6G RAT. If the MM assigns different NAS identifiers for paging to the UE under both 5G RAT and 6G RAT during the merged registration, then the UE identification information is the NAS identifier for paging corresponding to the 5GS (i.e., the NAS identifier for paging corresponding to the 5G RAT).

[0188] The PDU session to be activated can be a session that the UE requests to be activated on the 5G-RAN, or a session that has been switched over from the 6GS (the session identifier can be mapped from the 6G session identifier, or the corresponding PDU session ID in the 5GS can be assigned to its user plane connection during the 6G session establishment process).

[0189] It should be noted that if the UE and the network support multiple access or dual radio, steps 501-504 can be skipped and step 505 can be executed directly.

[0190] The above embodiments enable rapid switching of terminals between different RATs without requiring a registration process during interoperability between different RATs, thus simplifying the complexity of interoperability between terminals. The terminal's proactive request to release the connection between the previous access network and the core network (first core network device) helps simplify the terminal's behavior logic and reduce deployment costs.

[0191] In one embodiment, after the terminal sends a first merge registration request to the core network through the access network device corresponding to the second RAT to complete the merge registration of the first RAT and the second RAT, the terminal can be in an idle state when the first RAT is idle. If the terminal has uplink data or uplink signaling (messages) that need to be sent to the core network through the access network device corresponding to the first RAT, the terminal first sends a first request to the first core network device through the access network device corresponding to the first RAT to establish a connection with the first core network device through the access network device corresponding to the first RAT. Then, the first core network device triggers the disconnection of the connection between the access network device corresponding to the second RAT and the first core network device.

[0192] In this embodiment, the content carried by the first request is the same as in the previous embodiments, and will not be described again. The processing of the first core network device after receiving the first request is also the same as in the previous embodiments, and will not be described again.

[0193] Unlike the previous embodiments, in this embodiment, after the first core network device establishes a NAS connection with the terminal through the access network device corresponding to the first RAT and / or controls the establishment of user plane resources through the access network device corresponding to the first RAT, the first core network device can also initiate the process of releasing the connection corresponding to the second RAT.

[0194] Specifically, if the first core network device determines that it does not support multiple access or does not support the terminal connecting to the core network simultaneously through access network devices under two RATs, and the terminal is in a connected state under the second RAT, then after receiving the first request sent by the terminal through the access network device corresponding to the first RAT, the first core network device further includes: when the terminal is in a connected state under the second RAT, the first core network device sends a release command to the access network device corresponding to the second RAT, wherein the release command is used to instruct the access network device corresponding to the second RAT to release the terminal-related resources.

[0195] The specific method by which the first core network device determines whether it supports a terminal to connect to the first core network device simultaneously through the access network devices corresponding to the first RAT and the second RAT (i.e., supports multiple terminal access) can be as follows: The first core network device determines whether it supports a terminal to connect to the first core network device simultaneously through the access network devices corresponding to the first RAT and the second RAT based on at least one of the terminal's capabilities, local configuration, terminal's subscription data, and network capabilities.

[0196] Terminal capabilities (or terminal capability information) can be used to indicate, for example, whether the terminal supports two NAS connections to the network simultaneously, or whether the terminal supports connection to the core network through two access network devices.

[0197] Network capabilities can be used to indicate whether a network supports a terminal connecting to the core network simultaneously through two access network devices (or multiple access network devices corresponding to RATs).

[0198] This embodiment does not limit the content that the terminal's contract information and local configuration may contain.

[0199] For example, the first core network device may determine whether to support a terminal simultaneously connecting to the first core network device through the access network devices corresponding to the first RAT and the second RAT based on at least one of the terminal's capabilities, local configuration, terminal's subscription data, and network capabilities. This determination may include: if the first core network device determines that the first core network device supports multiple access based on its local configuration (or operator configuration) and / or network capabilities, and determines that the terminal supports multiple access based on the terminal's subscription data and / or terminal capabilities, then the device determines that the terminal supports multiple access simultaneously (i.e., multiple access is supported); or if the first core network device determines that the first core network device does not support multiple access based on its local configuration and / or network capabilities, and / or determines that the terminal does not support multiple access based on the terminal's subscription data and / or terminal capabilities, then the device determines that the terminal does not support multiple access simultaneously (i.e., multiple access is not supported).

[0200] The processing of the access network device corresponding to the second RAT may include: receiving a release command from the first core network device; and sending an RRC release message to the terminal.

[0201] After the terminal sends a first request to the first core network device through the access network device corresponding to the first RAT, the method further includes: when the terminal is in a connected state with the second RAT, the terminal receives an RRC release message from the access network device corresponding to the second RAT, wherein the RRC release message is used to indicate the release of the RRC connection between the terminal and the access network device corresponding to the second RAT.

[0202] The release command may carry at least one of the following: the NGAP identifier (ID) of the terminal corresponding to the first core network device, the NGAP identifier of the terminal corresponding to the access network device corresponding to the second RAT, and the release reason. The explanation regarding the NGAP ID is the same as in the previous example and will not be repeated here.

[0203] The release reason may include at least one of the following: the terminal is connected to the core network through the access network device corresponding to another RAT (i.e., the first RAT); the connection between the terminal and the core network on the current access network (i.e., the access network device corresponding to the second RAT) needs to be released; the terminal's service is switched to a new network; or the connection between the terminal and the core network is switched to a new RAT (such as the first RAT).

[0204] The second RAT-corresponding access network device releases terminal-related resources after receiving the release command. The content that the RRC release message can carry is the same as that in the aforementioned embodiments, and will not be repeated here.

[0205] Based on Figure 4, and in conjunction with Figure 6, after the UE performs merged registration through 6G-RAN (i.e., the access network device corresponding to the second RAT), if there is uplink data or signaling message that needs to be sent to the core network through 5G-RAN (i.e., the access network device corresponding to the first RAT), the UE can directly establish a NAS connection with the MM (i.e., the first core network device) on 5G-RAN through a service request procedure. Subsequently, the network side can release the UE's connection on 6G-RAN based on the UE's capabilities and / or network configuration.

[0206] The relevant explanations for steps 600 and 500 are the same, and will not be repeated here.

[0207] Step 601 is the same as step 505, and will not be described again.

[0208] After completing step 601, the MM, based on at least one of the following: UE capabilities (e.g., whether the UE supports two simultaneous NAS connections to the network, or whether the UE supports connecting to the core network through two access network devices), network capabilities (whether the network supports the UE connecting to the core network through two access network devices simultaneously), UE subscription messages, and operator configuration, if it does not support multiple access for the UE, then proceeds to step 602, whereby the MM sends a UE context release command (i.e., the release command in the aforementioned embodiment) to the 6G-RAN. The 6G-RAN releases all signaling and user data transmission resources. The UE on the MM enters an idle state under the 6G RAT. The UE context release command includes at least one of the following parameters: MM UE NGAP ID; RAN UE NGAP ID; Cause (release reason). The release reason can include at least one of the following: service switching to a new network, or connection to the core network switching to a new RAT.

[0209] Step 603: The 6G-RAN sends an RRC release message to the UE, and the UE enters or switches from the connected state to the idle state under the 6G RAT. The RRC release message contains at least one of the parameters indicating the reason for releasing the RRC connection: cnType, which indicates the core network to which the UE has switched, which can be EPC, 5GC, 6GC, etc. In this embodiment, it is 5GC, that is, it indicates that the UE has switched from 6GC to 5GC; the second indication information, which indicates that the reason for the UE leaving the connected state (or switching from the connected state to the idle state) is because it has switched to a new core network, or indicates that the UE has connected to the core network through a new access network device.

[0210] It should be noted that if the UE is in an idle state on the 6G-RAN (i.e., in an idle state on the 6G RAT) after completing step 601, or supports simultaneous access to two access network devices (or supports multiple UE access), then steps 602 to 603 do not need to be executed.

[0211] Through the above embodiments, the terminal can first establish a connection with the core network under a RAT, and then the network side can disconnect the terminal's connection on another access network, i.e., another RAT, which helps to ensure service continuity. Furthermore, controlling the release of the terminal's connection on the access network corresponding to the old RAT by the network side helps to ensure compatibility with legacy UEs. That is, even if the legacy UE does not recognize the second indication information carried in the RRC Release, the NAS connection of the terminal on the access network corresponding to the old RAT can be released, preventing the legacy UE from being connected to the core network simultaneously by two access network devices (or two access network devices corresponding to two RATs).

[0212] In some possible embodiments, after the terminal sends a first merge registration request to the core network through the access network device corresponding to the second RAT to complete the merge registration of the first RAT and the second RAT, the terminal can be in an idle state in the first RAT. If the first core network device determines that there is downlink data (e.g., downlink data in the application server (AF)) or downlink signaling (e.g., NAS messages or signaling) that needs to be sent to the terminal through the access network device corresponding to the first RAT, the first core network device will trigger the terminal to establish a connection with the first core network device through the access network device corresponding to the first RAT.

[0213] In one embodiment, before the first core network device receives the first request sent by the terminal under the first RAT, the method further includes: when the terminal is in a connected state under the second RAT, the first core network device sends a first notification message to the terminal through the access network device corresponding to the second RAT, wherein the first notification message carries third indication information, the third indication information being used to instruct the terminal to establish a connection with the first core network device through the access network device corresponding to the first RAT.

[0214] Accordingly, before the terminal sends a first request to the first core network device through the access network device corresponding to the first RAT, the method further includes: when the terminal is in a connected state in the second RAT, the terminal receives a first notification message from the core network through the access network device corresponding to the second RAT, wherein the first notification message carries third indication information, the third indication information being used to instruct the terminal to establish a connection with the first core network device through the access network device corresponding to the first RAT.

[0215] In this embodiment, the terminal receiving the first notification message from the core network through the access network device corresponding to the second RAT specifically means that the terminal receives the first notification message from the first core network device through the access network device corresponding to the second RAT.

[0216] Specifically, the first core network device can determine whether it supports a terminal connecting to the core network (such as the first core network device) simultaneously through the access network devices corresponding to the first RAT and the second RAT respectively. If it is determined that the terminal supports connecting to the first core network device simultaneously through the access network devices corresponding to the first RAT and the second RAT respectively (i.e., supporting multiple access for the terminal), and the terminal is in the connected state in the second RAT and the terminal is in the idle state in the first RAT, the first core network device sends a first notification message to the terminal through the access network device corresponding to the second RAT.

[0217] The specific method by which the first core network device determines whether it supports the terminal to connect to the first core network device simultaneously through the access network devices corresponding to the first RAT and the second RAT is the same as in the aforementioned embodiments and will not be repeated here.

[0218] The third instruction information may include the type information of the first RAT, that is, the type information of the first RAT contained in the third instruction information is used to instruct the terminal to establish a connection with the first core network device through the access network device corresponding to the first RAT.

[0219] In addition to carrying third instruction information, the first notification message may also carry the terminal's identifier. This document does not limit or exhaustively list all possible contents that the first notification message may carry.

[0220] After the terminal receives the first notification message, it can execute the process of sending a first request to the first core network device through the access network device corresponding to the first RAT. In this embodiment, the content carried by the first request and the processing of the first core network device after receiving the first request are the same as in the previous embodiments, and will not be described again.

[0221] In this embodiment, after the terminal establishes a connection with the first core network device through the access network device corresponding to the first RAT, it can simultaneously maintain the connection between the terminal and the first core network device through the access network device corresponding to the second RAT. That is, the terminal can access the core network simultaneously through the first RAT and the second RAT.

[0222] In one embodiment, before the first core network device receives the first request sent by the terminal through the access network device corresponding to the first RAT, the method further includes: when the terminal is in a connected state in the second RAT, the first core network device sends a release command to the access network device corresponding to the second RAT, wherein the release command is used to instruct the access network device corresponding to the second RAT to release the terminal-related resources.

[0223] Specifically, the first core network device can determine whether it supports the terminal to connect to the core network (such as the first core network device) simultaneously through the access network devices corresponding to the first RAT and the second RAT respectively. If it is determined that the terminal does not support the terminal to connect to the first core network device simultaneously through the access network devices corresponding to the first RAT and the second RAT respectively, and the terminal is in the connected state in the second RAT and the terminal is in the idle state in the first RAT, the first core network device sends a release command to the access network device corresponding to the second RAT.

[0224] The processing of the access network device corresponding to the second RAT may include: receiving a release command from the first core network device; and sending an RRC release message to the terminal.

[0225] Before the terminal sends a first request to the first core network device through the access network device corresponding to the first RAT, the method further includes: when the terminal is in a connected state with the second RAT, the terminal receives an RRC release message from the access network device corresponding to the second RAT, wherein the RRC release message is used to indicate the release of the RRC connection between the terminal and the access network device corresponding to the second RAT.

[0226] The descriptions of the release command, the processing of the terminal-related resources by the access network device corresponding to the second RAT after receiving the release command, and the content that the RRC release message can carry are all the same as in the previous embodiments and will not be repeated.

[0227] After the terminal receives the RRC release message, it can execute the process of sending a first request to the first core network device through the access network device corresponding to the first RAT. In this embodiment, the content carried by the first request and the processing of the first core network device after receiving the first request are the same as in the previous embodiments, and will not be described again.

[0228] In this embodiment, after the terminal releases the connection between the access network device corresponding to the second RAT and the first core network device, it establishes a connection with the first core network device through the access network device corresponding to the first RAT.

[0229] Based on Figure 4, and in conjunction with Figure 7, after the UE performs merged registration through 6G-RAN (i.e., the access network device corresponding to the second RAT), if downlink data or signaling messages need to be sent to the UE through 5G-RAN (i.e., the access network device corresponding to the first RAT), the MM can send a DL NAS message to the UE through 6G-RAN to notify it to establish a connection with the core network on 5G-RAN. Subsequently, the network side can release the UE's connection on 6G-RAN based on the UE's capabilities and / or network configuration.

[0230] The relevant descriptions for steps 700 and 500 are the same, and will not be repeated here.

[0231] When downlink data or signaling needs to be transmitted to the UE via 5G-RAN, the MM can classify the following two cases based on whether the UE and / or the network support the UE connecting to the core network simultaneously through two access network devices:

[0232] If multiple access for UEs is not supported, then steps 701 to 702 are executed. These steps 701 to 702 are the same as steps 602 to 603 in the previous example, and will not be described again.

[0233] If multiple access for UEs is supported, the MM sends a downlink NAS notification message (i.e., the first notification message in the aforementioned embodiment) to the UE, and then executes step 703. The downlink NAS message contains at least one of the following parameters: UE identification information, such as GUTI, SUPI, etc.; third indication information: used to instruct the UE to establish a connection with the core network on another access network device (e.g., 5G-RAN) corresponding to another RAT.

[0234] Step 703 is the same as step 505. Specifically, based on the third indication information in the received DL NAS message or the cnType or second indication information in the RRC Release message, the UE determines that it needs to access the core network via 5G-RAN (e.g., the core network indicated in cnType, or the core network currently accessed via 6G-RAN). The UE then initiates a service request to the MM on the 5G-RAN, establishing a NAS connection with the MM to send NAS messages to or receive NAS messages from the MM. Subsequently, the UE can send a session establishment message to the Session Management Element (SMF) on the 5G-RAN to establish user plane resources for user data transmission.

[0235] In this embodiment, when the terminal is in a connected state on an old RAT (such as the second RAT) and in an idle state on a new RAT (such as the first RAT), when the network needs to switch to a new access network device (the access network device corresponding to the new RAT) to interact with the terminal, it can actively release the connection with the terminal on the access network corresponding to the old RAT, and indicate in the connection release message that the terminal network side has switched to the new access network device. This avoids the situation where the terminal is briefly connected to two access network devices of different RATs at the same time, and can release the resources of the access network corresponding to the old RAT in advance for other terminals to use.

[0236] In some possible embodiments, after the terminal sends a first merge registration request to the core network through the access network device corresponding to the second RAT to complete the merge registration of the first RAT and the second RAT, the terminal can be in an idle state in the first RAT. If the first core network device determines that there is downlink data or downlink signaling (such as NAS messages or signaling) that needs to be sent to the terminal through the access network device corresponding to the first RAT, the first core network device can trigger the terminal to initiate the establishment of a connection with the first core network device through the access network device corresponding to the first RAT by paging.

[0237] Before the first core network device receives the first request sent by the terminal through the access network device corresponding to the first RAT, the method further includes: the first core network device sending a third paging message to the access network device corresponding to the first RAT, wherein the third paging message carries one of the following: a NAS identifier for paging corresponding to the first RAT, or a NAS identifier for paging corresponding to the first RAT and the second RAT.

[0238] Optionally, the access network device corresponding to the first RAT can be a uniquely identified access network device, such as being referred to as the first access network device. The first core network device sending a third paging message to the access network device corresponding to the first RAT can be: the first core network device sending a third paging message to the first access network device corresponding to the first RAT.

[0239] The method by which the first core network device determines the first access network device may include: determining the first access network device corresponding to the first RAT based on the location information of the terminal; or, using the access network device in the registration area (i.e., TAI) last accessed by the terminal within the first RAT as the first access network device. The location information of the terminal may include any one of the following: the cell where the terminal is located, the tracking area where the terminal is located, or the geographical location of the terminal.

[0240] This is merely an exemplary description of how the first core network device determines the first access network device, and does not limit or exhaust all possible ways in which the first core network device determines the first access network device.

[0241] Optionally, the access network device corresponding to the first RAT can be all access network devices within the registration area corresponding to the first RAT. The first core network device sending a third paging message to the access network device corresponding to the first RAT can be: the first core network device sending the third paging message to all access network devices within the registration area corresponding to the first RAT.

[0242] If, during the terminal merging registration process, the first core network device assigns a NAS identifier for paging corresponding to the first RAT and the second RAT to the terminal, then the third paging message can carry the NAS identifier for paging corresponding to the first RAT and the second RAT. If, during the terminal merging registration process, the first core network device assigns a NAS identifier for paging corresponding to the second RAT and a NAS identifier for paging corresponding to the first RAT to the terminal, then the third paging message carries the identifier for paging corresponding to the first RAT.

[0243] Optionally, the third paging message may also carry fourth indication information, wherein the fourth indication information is used to instruct the terminal to establish a connection with the first core network device through the access network device corresponding to the first RAT. Specifically, the fourth indication information may be used to indicate that downlink data or downlink signaling (such as NAS signaling) needs to be sent to the terminal through the access network device corresponding to the first RAT, and / or to instruct the terminal to establish a connection with the first core network device through the access network device corresponding to the first RAT.

[0244] The fourth indication information can be a newly defined paging reason value or a newly defined paging reason description.

[0245] The third paging message can also carry other content, such as a registration area, which can be the registration area corresponding to the first RAT. This document does not limit or exhaustively list all the possible contents that the third paging message can carry.

[0246] After receiving the third paging message, the access network device corresponding to the first RAT can also send a first paging message to the terminal. Before the terminal sends a first request to the first core network device through the access network device corresponding to the first RAT, the method further includes: the terminal receiving a first paging message from the access network device corresponding to the first RAT, wherein the first paging message carries one of the following: a NAS identifier for paging corresponding to the first RAT, or a NAS identifier for paging corresponding to both the first RAT and the second RAT.

[0247] The access network device corresponding to the first RAT can be any one of the aforementioned first access network device or any one of all access network devices corresponding to the first RAT.

[0248] The NAS identifier used for paging carried in the first paging message is the same as that in the third paging message, and will not be described again.

[0249] Optionally, if the third paging message carries fourth indication information, the first paging message also carries fourth indication information, wherein the fourth indication information is used to instruct the terminal to establish a connection with the first core network device through the access network device corresponding to the first RAT. The relevant description of this fourth indication information is the same as in the foregoing embodiments and will not be repeated.

[0250] In one embodiment, after the terminal receives the first paging message, it can first send a first indication message when the second RAT is in a connected state, and then the terminal receives an RRC release message from the access network device corresponding to the second RAT.

[0251] Accordingly, the first core network device receives the first indication information from the terminal, and then the first core network device sends a release command to the access network device corresponding to the second RAT.

[0252] The processing by the access network device corresponding to the second RAT includes: after receiving the release command, the access network device corresponding to the second RAT releases the resources related to the terminal; then the access network device corresponding to the second RAT sends an RRC release message to the terminal.

[0253] After the terminal receives the RRC release message from the access network device corresponding to the second RAT, it can perform the process of sending a first request to the first core network device through the access network device corresponding to the first RAT.

[0254] The first instruction information, RRC release message, release command, the content carried by the first request, and the processing of the first core network device after receiving the first request are the same as in the previous embodiments, and will not be described again.

[0255] Based on Figure 4, and in conjunction with Figure 8, after the UE performs merged registration through 6G-RAN (i.e., the access network device corresponding to the second RAT), if downlink data or signaling messages need to be sent to the UE through 5G-RAN (i.e., the access network device corresponding to the first RAT), the MM can page the UE on 5G-RAN, triggering the UE to initiate a service request process on 5G-RAN and establish a NAS connection with the MM.

[0256] The relevant descriptions for steps 800 and 500 are the same, and will not be repeated here.

[0257] Step 801: The MM sends a paging message (i.e., the third paging message in the aforementioned embodiment) to the 5G-RAN to page the UE.

[0258] Specifically, when downlink data or signaling needs to be sent to the UE via the 5G-RAN, the MM pages the UE on the 5G-RAN. The 5G-RAN can be determined based on the UE's location information, such as the TAI the UE last visited, or by paging the UE on the Tracking Area (TA) corresponding to the 5G network within the entire registered area. The paging message carries at least one of the following information:

[0259] The UE's identification information, GUTI (for example, it could be the NAS identifier for paging corresponding to 5G RAT, or the NAS identifier for paging corresponding to 5G RAT and 6GRAT);

[0260] The UE's registered area, or the TAI list corresponding to 5G-RAT in the registered area, is used to assist 5G-RAN in determining the paging area;

[0261] The fourth indication information is used to indicate that there is downlink data or signaling message that needs to be sent to the UE through the 5G-RAN. The UE needs to establish a connection with the MM on the 5G-RAN. This fourth indication information can be a new paging cause. For example, the fourth indication information can be a newly defined paging cause value or paging cause description information, such as paging cause for interworking or paging cause for multi-access.

[0262] Step 802: The 5G-RAN sends a paging message to the UE (i.e., the first paging message in the aforementioned embodiment). The paging message carries the UE identification information GUTI and the fourth indication information.

[0263] The UE that performs merged registration can listen for paging messages in both 5G and / or 6G cells. After receiving a paging message in 5G-RAN, the UE can execute step 803, which involves sending a service request message (i.e., the first request in the aforementioned embodiment) to the MM through 5G-RAN and establishing a NAS connection with the MM on 5G-RAN.

[0264] Here, before the UE executes step 803, if the UE and MM have a NAS connection in a connected state on 6G-RAN, the UE can first notify the MM to release the connection with the UE on 6G-RAN, that is, execute steps 501 to 504 in the aforementioned example.

[0265] In this embodiment, the core network (the first core network device) can directly page the terminal on the access network device corresponding to the new RAT. This can be used when the terminal has no connection to the core network on either of the two RATs (or the terminal is idle on both RATs), or when the terminal has no connection to the core network on the new RAT (i.e., the terminal is idle on the new RAT, such as the first RAT). If the terminal still has a connection to the core network on the old RAT, it can actively request to release the connection to the core network on the previous access network (the access network device corresponding to the second RAT), which helps simplify the core network's behavior logic and reduce the deployment cost of the core network.

[0266] In one embodiment, after the terminal receives the first paging message, it can perform the process of sending a first request to the first core network device through the access network device corresponding to the first RAT. In this embodiment, the content carried by the first request and the processing of the first core network device after receiving the first request are the same as in the previous embodiments, and will not be described again.

[0267] After the first core network device establishes a NAS connection with the terminal through the access network device corresponding to the first RAT and / or controls the establishment of user plane resources through the access network device corresponding to the first RAT, the first core network device may also initiate the process of releasing the connection corresponding to the second RAT if it is determined that multiple access is not supported. The relevant description of the process of the first core network device releasing the connection corresponding to the second RAT is the same as that in the previous embodiment and will not be repeated.

[0268] Based on Figure 4, and in conjunction with Figure 9, after the UE performs merged registration through 6G-RAN (i.e., the access network device corresponding to the second RAT), if downlink data or signaling messages need to be sent to the UE through 5G-RAN (i.e., the access network device corresponding to the first RAT), the MM can page the UE on 5G-RAN, triggering the UE to initiate a service request process on 5G-RAN to establish a NAS connection with the MM. Subsequently, the MM releases the connection with the UE on 6G-RAN.

[0269] Steps 900 to 902 are the same as those steps 800 to 802 in the previous example, and will not be repeated here.

[0270] Steps 903 to 905 are the same as steps 601 to 603 in the previous example, and will not be described again.

[0271] This embodiment can also be used when the terminal is not connected to the core network on either of the two RATs, or when the terminal is not connected to the core network on a new RAT. In this embodiment, the network is connected to the terminal on at least one RAT at any given time, which facilitates the network side in maintaining continuous communication services for the terminal.

[0272] In some possible implementations, the control plane network elements of the core networks of the first and second communication systems are respectively set.

[0273] In some embodiments, the equipment that processes the merged registration of terminals on the core network side includes a first core network device of a first communication system and a second core network device of a second communication system.

[0274] The terminal sending the first merged registration request to the core network through the access network device corresponding to the second RAT is as follows: the terminal sends the first merged registration request to the second core network device through the access network device corresponding to the second RAT. The terminal receiving the first merged registration acceptance message from the core network through the access network device corresponding to the second RAT is specifically as follows: the terminal receives the first merged registration acceptance message from the second core network device through the access network device corresponding to the second RAT.

[0275] Accordingly, the processing of the second core network device may include: the second core network device receiving a first merge registration request sent by the terminal through the access network device corresponding to the second RAT, wherein the first merge registration request is used to request the establishment of the terminal context for the terminal under the first RAT and the second RAT; the second core network device sending a first merge registration acceptance message to the terminal through the access network device corresponding to the second RAT, wherein the first merge registration acceptance message is used for the terminal to determine that the merge registration of the first RAT and the second RAT has been completed.

[0276] Before the terminal sends the first merge registration request to the second core network device through the access network device corresponding to the second RAT, the process may further include: the terminal establishing an RRC connection with the access network device corresponding to the second RAT.

[0277] The terminal sends a first merged registration request to the second core network device through the access network device corresponding to the second RAT, which may include: the terminal sending the first merged registration request to the access network device corresponding to the second RAT, and the access network device corresponding to the second RAT forwarding the first merged registration request to the second core network device.

[0278] The content carried in the first merged registration request is the same as that in the previous embodiment, and will not be described again.

[0279] After the second core network device receives the first merged registration request, the terminal and the network side in the second communication system can perform two-way authentication. The network side in the second communication system participating in the two-way authentication of the terminal may include at least one of the second core network device, UDM, etc. This embodiment does not limit the network elements of the network side in the second communication system participating in the two-way authentication of the terminal, or the processing of the two-way authentication between the terminal and the network side in the second communication system.

[0280] After the two-way authentication between the terminal and the network side within the second communication system is completed, the second core network device can send a second merge registration request to the first core network device. Correspondingly, the processing of the first core network device may include: the first core network device receiving the second merge registration request from the second core network device, wherein the second merge registration request is used to request the first core network device to establish an association with the second core network device and to establish the terminal context for the terminal under the first RAT; the first core network device sending a second merge registration acceptance message to the second core network device, wherein the second merge registration acceptance message is used to indicate acceptance of the merge registration.

[0281] Optionally, before sending the second merge registration request to the first core network device, the second core network device may also perform at least one of the following: the second core network device determines the terminal request to perform merge registration based on the registration type carried in the first merge registration request; the second core network device determines the terminal request to register simultaneously in the first RAT and the second RAT based on the type information of the first RAT carried in the first merge registration request.

[0282] For example, the second core network device can determine whether the terminal requests merged registration based on the registration type carried in the first merged registration request. If the registration type is merged registration, it can be determined that the terminal requests merged registration.

[0283] For example, the second core network device can determine whether the terminal requests merged registration based on the registration type carried in the first merged registration request. If the registration type is merged registration, it can be determined that the terminal requests merged registration. Then, based on the type information of the first RAT carried in the first merged registration request, it can be determined that the terminal requests to register simultaneously in the first RAT and the second RAT and / or that the terminal needs to register simultaneously in the core network of the second communication system and the core network of the first communication system.

[0284] Optionally, the second core network device may also identify the first core network device before sending the second merge registration request to the first core network device.

[0285] In one scenario, the first merged registration request may carry the NAS identifier for paging corresponding to the first RAT. In this case, the second core network device can discover the first core network device based on the NAS identifier for paging corresponding to the first RAT.

[0286] In one scenario, the first merged registration request does not carry the NAS identifier for paging corresponding to the first RAT. In this case, the second core network device can identify the first core network device based on at least one of the terminal's location information and slice information.

[0287] For example, the location information of the terminal may include the TAI where the terminal is located. The second core network device may select the control plane network element on the core network side of the first communication system whose service area includes the TAI where the terminal is located as the first core network device.

[0288] For example, the second core network device can select the control plane network element on the core network side of the first communication system that supports the slice and whose service area includes the TAI where the terminal is located, based on the slice information and the TAI where the terminal is located.

[0289] The second merged registration request may carry at least one of the following: the NAS identifier for paging corresponding to the second RAT, the identification information of the second core network device, and the registration area corresponding to the second RAT, wherein the identification information of the second core network device is used by the first core network device to establish an association between the first core network device and the second core network device.

[0290] The NAS identifier for paging corresponding to the second RAT can be assigned to the terminal by the second core network device, and the specific assignment method is not limited in this embodiment.

[0291] The registration area corresponding to the second RAT can also be assigned to the terminal by the second core network device.

[0292] The identification information of the second core network device may contain the same content as in the aforementioned embodiments, and will not be described again.

[0293] It should be noted that the second merged registration request may also carry various contents of the first merged registration request. For example, the second merged registration request may also carry at least one of the following: the identifier of the terminal, the registration type, the type of the first RAT, the identifier of the access network device corresponding to the first RAT, the tracking area information corresponding to the first RAT, and the identifier of the cell corresponding to the access network device corresponding to the first RAT.

[0294] After receiving the second merge registration request, the first core network device can also determine whether to accept the merge registration. If it determines to accept the merge registration, it establishes the terminal context for the terminal under the first RAT and establishes the association between the first core network device and the second core network device.

[0295] The process by which the first core network device determines whether to accept merged registration may include: the first core network device determining whether to accept merged registration based on at least one of its local configuration, the terminal's subscription data, and network capabilities. This embodiment does not limit the specific method by which the first core network device determines whether to accept merged registration based on at least one of its local configuration, the terminal's subscription data, and network capabilities.

[0296] The first core network device establishes an association between itself and the second core network device by recording this association in the terminal context under the first RAT. For example, the first core network device can record the identification information of the second core network device in the terminal context under the first RAT and associate the second core network device as a mobility management network element (or control plane network element) associated with the first core network device in the second communication system. Alternatively, the first core network device can record the second core network device as a mobility control network element (or control plane network element) associated with the first core network device and serving the terminal in the second communication system.

[0297] After the first core network device completes the establishment of the association between the first core network device and the second core network device, and establishes the terminal context for the terminal under the first RAT, the first core network device sends a second merge registration acceptance message to the second core network device.

[0298] The second merged registration acceptance message carries at least one of the following: the NAS identifier for paging corresponding to the first RAT, the identification information of the first core network device, and the registration area corresponding to the first RAT. The identification information of the first core network device is used by the second core network device to establish an association between the first core network device and the second core network device.

[0299] Optionally, the second merged registration acceptance message may carry the NAS identifier for paging corresponding to the first RAT.

[0300] The NAS identifier for paging corresponding to the first RAT can be assigned by the first core network device. For example, the first core network device can map the NAS identifier for paging corresponding to the second RAT to the NAS identifier for paging corresponding to the first RAT. The specific mapping method is not limited in this embodiment.

[0301] Optionally, the second merged registration acceptance message may not carry the NAS identifier for paging corresponding to the first RAT. In this case, the first core network device can use the NAS identifier for paging corresponding to the second RAT as the same as the NAS identifier for paging corresponding to the first RAT, that is, the NAS identifier for paging corresponding to the second RAT is equal to the NAS identifier for paging corresponding to both the first and second RATs.

[0302] Optionally, the second merged registration acceptance message may carry the registration area corresponding to the first RAT. The registration area corresponding to the first RAT may be assigned by the first core network device; for example, the registration area corresponding to the first RAT may be different from the registration area corresponding to the second RAT.

[0303] Optionally, the second merged registration acceptance message may not carry the registration area corresponding to the first RAT. For example, if the registration area corresponding to the second RAT also includes the registration area corresponding to the first RAT, the first core network device may not further divide or allocate the registration area corresponding to the first RAT; that is, the registration area corresponding to the second RAT is equal to the registration areas corresponding to the first and second RATs.

[0304] The identification information of the first core network device may contain similar content to that of the second core network device, and will not be elaborated upon further.

[0305] The processing after the second core network device receives the second merged registration acceptance message from the first core network device may include: the second core network device establishing the terminal context of the terminal under the second RAT and establishing an association relationship with the first core network device.

[0306] The establishment of an association between the second core network device and the first core network device may refer to the association and storage of the identification information of the first core network device in the terminal context under the second RAT, so as to record that the control plane network element serving the terminal under the first communication system is the first core network device.

[0307] After the second core network device establishes the terminal context of the terminal under the second RAT and establishes the association relationship with the first core network device, the processes that can be performed may include: the second core network device sending a first merged registration acceptance message to the terminal through the access network device corresponding to the second RAT; and the terminal receiving the first merged registration acceptance message from the second core network device through the access network device corresponding to the second RAT.

[0308] The first merged registration acceptance message carries at least one of the following: registration type, NAS identifier for paging corresponding to the second RAT, NAS identifier for paging corresponding to the first RAT, NAS identifier for paging corresponding to both the first and second RATs, registration area corresponding to the second RAT, registration area corresponding to the first RAT, and registration area corresponding to both the first and second RATs.

[0309] Optionally, if the first core network device assigns a NAS identifier for paging corresponding to the first RAT to the terminal (notified to the second core network device via a second merged registration acceptance message), and the second core network device assigns a NAS identifier for paging corresponding to the second RAT to the terminal, then the first merged registration acceptance message may carry the NAS identifier for paging corresponding to the second RAT and the NAS identifier for paging corresponding to the first RAT.

[0310] Optionally, if the second merged registration acceptance message sent by the first core network device to the second core network device does not carry any NAS identifier for paging, and the second core network device has assigned a NAS identifier for paging corresponding to the second RAT to the terminal, then the second core network device can determine to use the NAS identifier for paging corresponding to the second RAT as the NAS identifier for paging corresponding to the first RAT and the second RAT. Accordingly, the first merged registration acceptance message can carry the NAS identifiers for paging corresponding to the first RAT and the second RAT.

[0311] Optionally, if the first core network device allocates a registration area for the terminal corresponding to the first RAT (notifying the second core network device via the second merged registration acceptance message), and the second core network device allocates a registration area for the terminal corresponding to the second RAT, then the first merged registration acceptance message may carry the registration area corresponding to the second RAT and the registration area corresponding to the first RAT.

[0312] Optionally, if the second merged registration acceptance message sent by the first core network device to the second core network device does not carry a registration area, and the second core network device has allocated a registration area corresponding to the second RAT for the terminal, then the second core network device can determine that the registration area corresponding to the second RAT is the registration area corresponding to the first RAT and the second RAT. Accordingly, the first merged registration acceptance message can carry the registration areas corresponding to the first RAT and the second RAT.

[0313] After receiving the first merged registration acceptance message, the terminal can be in a connected state under the second RAT and in an idle state under the first RAT. In this case, the terminal can listen for paging messages in the registration area corresponding to the first RAT. Furthermore, the terminal can determine, based on relevant configuration, to enter an idle state under both the first and second RATs, and then listen for paging messages in the registration areas corresponding to both the first and second RATs.

[0314] Additionally, if the second core network device and / or the first core network device determine that merged registration is not supported, the process may further include: the second core network device sending a first merged registration rejection message to the terminal. This first merged registration rejection message may carry at least one of the following: the terminal's identifier, a reason for rejection, etc. This first merged registration rejection message is used by the terminal to determine that the second core network device does not support merged registration. The reason for rejection can be configured according to actual circumstances and is not limited here.

[0315] Referring to Figure 10, taking a scenario where the mobility management network elements of the core networks of two communication systems are set up separately and independently, an exemplary description of the terminal merging registration process is provided, specifically including:

[0316] Step 1001: The UE initiates a first merged registration request to the 6G-MM (i.e., the second core network device in the aforementioned embodiment) through the 6G-RAN (the access network device corresponding to the second RAT in the aforementioned embodiment). The relevant description of the first merged registration request is the same as that in the aforementioned embodiment, and will not be repeated here.

[0317] Step 1002: The UE performs two-way authentication with the network.

[0318] Step 1003: 6G-MM sends a registration request message (i.e., the second merged registration request in the aforementioned embodiment) to AMF, the registration request message containing at least one of the following parameters:

[0319] 6G-GUTI, or 6G-MM, is the NAS identifier assigned to the UE for paging.

[0320] Identification information for 6G-MM, such as 6G-MM's FQDN, address, ID, etc.;

[0321] The registration area may contain a TAI list corresponding to the 5G RAT (i.e., the first RAT) and / or a TAI list corresponding to the 6G RAT (i.e., the second RAT), wherein the TAI list contains one or more TAIs;

[0322] The parameters included in the first merge registration request.

[0323] Specifically, step 1003 can be as follows: After receiving the first merged registration request, if the 6G-MM determines that the UE needs to register with the 5GC at the same time based on the first merged registration request, the 6G-MM sends a registration request message to the AMF.

[0324] If the first merged registration request carries a 5G-GUTI (i.e., the NAS identifier for paging corresponding to the first RAT), then 6G-MM can discover the AMF (i.e., the first core network device) based on the 5G-GUTI; if the first merged registration request does not carry a 5G-GUTI, then a suitable AMF can be selected to serve this UE based on the UE's current TAI and slice information. For example, an AMF that supports the UE's slice and whose service area includes the UE's TA can be selected.

[0325] Step 1004: The AMF determines whether to accept the registration request message based on at least one of the following: UE subscription message, network capabilities, operator configuration, etc. If accepted, the AMF establishes an association with the 6G-MM and creates a UE context for the UE. The AMF then sends a registration acceptance message (i.e., the second merged registration acceptance message in the aforementioned embodiment) to the 6G-MM. This message contains at least one of the following parameters:

[0326] 5G-GUTI is the UE identifier assigned by the AMF for paging. If the UE uses the same GUTI in 5GC and 6GC, this parameter can be omitted, and the 6G GUTI assigned by 6G MM can be used directly. Alternatively, this 5G-GUTI is a 5G-GUTI mapped from a 6G-GUTI.

[0327] The registration area is the TAI list corresponding to the 5G RAT allocated by the AMF to the UE. If the registration area allocated by the 6G MM includes the TAI list corresponding to the 5G RAT, this parameter can be omitted.

[0328] AMF identification information, such as AMF's FQDN, address, ID, etc.

[0329] Step 1005, the 6G-MM sends the first merged registration acceptance message to the UE via the 6G-RAN. The first merged registration acceptance message contains at least one of the following information:

[0330] The registration type is either a combined registration or, more specifically, a combined registration of 5GC and 6GC.

[0331] 6G-GUTI, or 6G-MM, is the identifier assigned to the UE for paging.

[0332] 5G-GUTI is the identifier assigned by the AMF to the UE for paging. This parameter may be omitted when the UE uses the same GUTI in 5GC and 6GC.

[0333] The registration area contains a TAI list corresponding to 5G RAT and / or a TAI list corresponding to 6G RAT, wherein the TAI list contains one or more TAIs.

[0334] Before executing step 1005, the 6G-MM establishes an association with the UE after receiving the registration acceptance request from the AMF. For example, it stores information related to the servicing AMF (FQDN, ID, address, etc.) in the UE context on the 6G-MM.

[0335] After completing step 1005, the UE is in connected state in 6GC and idle state in 5GC. The UE needs to listen for paging messages in the TAI list corresponding to the 5G RAT. Subsequently, the UE can enter idle state in both 5GC and 6GC, at which point the UE listens for paging messages throughout the entire registered area.

[0336] The above embodiments apply to situations where two core networks (e.g., 5GC and 6GC) of two communication systems each have two different MM network elements, and there is an interface between the two MMs that can interact. During the aforementioned merge registration process, the UE and the network can communicate via a single NAS message, carrying multiple NAS identifiers for paging assigned to the UE by different MMs, registration areas, etc. Using different NAS identifiers for paging facilitates the access network equipment in discovering and selecting the correct MM. That is, 5G-RAN can select the AMF containing the UE context through 5G-GUTI; similarly, 6G-RAN can discover the 6G-MM containing the UE context through 6G-GUTI. Establishing an association between 6G-MM and AMF facilitates communication between the UE and AMF via 6G-MM, or vice versa. This also helps the UE interact with the core network corresponding to a particular RAT even when there is no access network equipment covering that RAT.

[0337] It should also be noted that the above is only an exemplary description of the interaction processing between two communication systems. In actual processing, there may be more communication systems with different core networks setting up different mobility management network elements. In this case, the relevant processing for each other core network's mobility management network element and its corresponding RAT can be similar to the relevant processing of the first RAT (such as the 5G RAT in the example above), so it will not be described in detail.

[0338] In some embodiments, after the terminal sends a first merge registration request to the core network through the access network device corresponding to the second RAT to complete the merge registration of the first RAT and the second RAT, the terminal may, while the first RAT is in an idle state, determine that there is uplink data or uplink signaling (message) that needs to be sent to the core network through the access network device corresponding to the first RAT. In this case, the terminal first sends a first request to the first core network device through the access network device corresponding to the first RAT to establish a connection with the first core network device through the access network device corresponding to the first RAT.

[0339] The content carried in the first request is the same as that in the previous embodiments, and will not be repeated here.

[0340] Optionally, if the first request only carries the NAS identifier for paging corresponding to the first RAT or the NAS identifier for paging corresponding to both the first RAT and the second RAT, then the first request can be used to request the establishment of a NAS connection between the access network device corresponding to the first RAT and the first core network device.

[0341] After receiving the first request, the first core network device can establish a NAS connection with the terminal through the access network device corresponding to the first RAT. Then, the terminal can transmit uplink NAS signaling to the first core network device and / or receive downlink NAS signaling through this NAS connection. This embodiment does not limit the specific method by which the first core network device establishes a NAS connection with the terminal through the access network device corresponding to the first RAT.

[0342] Optionally, if the first request carries only the NAS identifier for paging corresponding to the first RAT or the NAS identifiers for paging corresponding to the first RAT and the second RAT, and the first request carries the identifier of the first session; then the first request can be used to request the establishment of a NAS connection between the access network device corresponding to the first RAT and the first core network device, and to request the establishment of user plane resources corresponding to the first RAT for transmitting the data to be transmitted in the first session.

[0343] After receiving the first request, the first core network device can establish a NAS connection with the terminal through the access network device corresponding to the first RAT, and control the establishment of user plane resources through the access network device corresponding to the first RAT. Then, the terminal can transmit uplink data and / or receive downlink data of the first session through the user plane resources. This embodiment does not limit the specific method by which the first core network device establishes a NAS connection with the terminal through the access network device corresponding to the first RAT, and controls the establishment of user plane resources.

[0344] After the first core network device receives the first request sent by the terminal under the first RAT, the method further includes: when the terminal is in a connected state under the first RAT, the first core network device sends a second notification message to the second core network device, wherein the second notification message carries network switching indication information, and the network switching indication information is used to indicate at least one of the following: the terminal establishes a connection with the first core network device through the access network device corresponding to the first RAT, the terminal is in a connected state under the first RAT, or the terminal switches from the second RAT to the first RAT.

[0345] The function of the second notification message can be to enable the terminal to enter a connected state on the core network side of the first communication system via the second core network device. The second core network device can be the control plane network element of the second communication system associated with the first core network device, as recorded on the first core network device side (or in the terminal context under the first RAT on the first core network device side).

[0346] The terminal establishes a connection with the first core network device through the access network device corresponding to the first RAT. Specifically, the terminal establishes a NAS connection with the first core network device through the access network device corresponding to the first RAT.

[0347] The terminal being in a connected state under the first RAT can mean that the terminal is in a connected state or has entered a connected state on the core network side corresponding to the first RAT.

[0348] The terminal switching from the second RAT to the first RAT can also refer to the terminal switching from the second communication system to the first communication message, where the second communication system corresponds to the second RAT and the first communication system corresponds to the first RAT.

[0349] Optionally, the network handover indication information can also be used to instruct the terminal to switch from the second communication system to the first communication system. For example, the terminal switching from the second communication system to the first communication system may refer to the terminal switching from the second RAT under the second communication system to the first RAT under the first communication system.

[0350] Optionally, the second notification message may also carry the terminal's identifier.

[0351] In one embodiment, after receiving a second notification message from the first core network device, the second core network device can determine whether it supports the terminal simultaneously connecting to the core network (i.e., the first core network device and the second core network device) through the access network devices corresponding to the first RAT and the second RAT respectively. If it is determined that the terminal can simultaneously connect to the core network through the access network devices corresponding to the first RAT and the second RAT respectively, and the terminal is in a connected state at the second RAT, the second core network device may not perform any processing. That is, the terminal can maintain a connected state at both the first RAT and the second RAT.

[0352] The specific method by which the second core network device determines whether it supports a terminal simultaneously connecting to the core network (the first core network device and the second core network device) through the access network devices corresponding to the first RAT and the second RAT can be as follows: The second core network device determines whether it supports a terminal simultaneously connecting to the core network through the access network devices corresponding to the first RAT and the second RAT based on at least one of the terminal's subscription data and network capabilities. The relevant descriptions of the terminal's subscription information and network capabilities are similar to those in the aforementioned embodiments and will not be repeated here. The second core network device determines whether to support multiple access based on at least one of the terminal's subscription data and network capabilities. This determination may include: if the second core network device determines, based on network capabilities, that the network side supports the terminal simultaneously connecting to the core network through access network devices under two RATs, and based on the terminal's subscription data, it determines that the terminal supports connecting to the core network through access network devices under two RATs, then the device supports the terminal simultaneously connecting to the core network through the access network devices corresponding to the first RAT and the second RAT, respectively; or if the second core network device determines, based on network capabilities, that the network side does not support the terminal simultaneously connecting to the core network through access network devices under two RATs, and / or based on the terminal's subscription data, it determines that the terminal does not support connecting to the core network simultaneously through the access network devices corresponding to the first RAT and the second RAT, respectively.

[0353] In one embodiment, after receiving a second notification message from the first core network device, the second core network device can determine whether it supports the terminal simultaneously connecting to the core network (i.e., the first core network device and the second core network device) through the access network devices corresponding to the first RAT and the second RAT, respectively. If it is determined that the terminal is not supported to simultaneously connect to the core network through the access network devices corresponding to the first RAT and the second RAT, and the terminal is in a connected state under the second RAT, the second core network device can send a release command to the access network device corresponding to the second RAT. The release command instructs the access network device corresponding to the second RAT to release the terminal's related resources. That is, if it is determined that the terminal is not supported to simultaneously connect to the core network through the access network devices corresponding to the first RAT and the second RAT, and the terminal is in a connected state under the second RAT, the second core network device can switch the terminal's connected state under the second RAT to an idle state.

[0354] After receiving the release command, the access network device corresponding to the second RAT can release the resources related to the terminal, such as releasing signaling and user data transmission resources (or user plane resources). Then, the access network device corresponding to the second RAT sends an RRC release message to the terminal. After the terminal receives the RRC release message from the access network device corresponding to the second RAT, an RRC connection is established between the terminal and the access network device corresponding to the second RAT. The content carried by the RRC release message is the same as in the previous embodiment and will not be described again.

[0355] Based on Figure 10, and in conjunction with Figure 11, after the UE performs combined registration of 5GC and 6GC (i.e., in 5G RAT and 6G RAT) through 6G-RAN (i.e., the access network device corresponding to the second RAT), and the UE is in an idle state on 5GC (i.e., in an idle state on the first RAT), if the UE has uplink data or signaling messages that need to be sent to AMF (i.e., the first core network device) through 5G-RAN (i.e., the access network device corresponding to the first RAT), the UE can establish a NAS connection with AMF in 5G-RAN through a service request procedure.

[0356] In step 1100, the UE performs merged registration through 6G-RAN and successfully registers in both 5GC and 6GC. The AMF and 6G-MM (second core network equipment) successfully establish a UE context for the UE. The specific processing of step 1100 includes steps 1001 to 1005 as shown in Figure 10 above, which will not be elaborated here.

[0357] Step 1101: The UE sends a service request (i.e., the first request in the aforementioned embodiment) to the AMF via the 5G-RAN, requesting to establish a connection with the AMF. Subsequently, the UE and the AMF enter the connected state. The service request includes at least one of the following information:

[0358] UE identification information, which includes the identification information assigned to the UE by the AMF in the registration acceptance message, such as 5G-GUTI, 5G-S-TMSI, etc.;

[0359] The identifier for the first session needs to be a PDU session identifier that is activated on 5GS, or a session identifier that is switched from 6GS to 5GS (the session identifier can be mapped from the 6G session identifier, or the corresponding PDU session ID in 5GS is assigned to its user plane connection during the 6G session establishment process).

[0360] Step 1102: After the UE enters the connected state on the AMF, the AMF sends a notification message (i.e., the second notification message in the aforementioned embodiment) to the 6G-MM (i.e., the second core network device in the aforementioned embodiment) indicating that it has entered the connected state in the 5GC. The 6G-MM is the mobility management network element associated with the AMF, and the notification message contains the following information:

[0361] UE identification information, such as SUPI, SUCI, GUTI (which can be 5G-GUTI or 6G-GUTI mapped from 5G-GUTI), etc.

[0362] Network handover indication information is used to indicate that the UE and AMF have established a NAS connection, or to indicate that the UE has entered the connected state in 5GC, or to indicate that the UE has switched from 6GS to 5GS.

[0363] Step 1103: The 6G-MM determines whether multi-access is supported for the UE based on at least one of the following: UE capabilities (e.g., whether the UE supports two simultaneous NAS connections to the network, or whether the UE supports connecting to the core network through two access network devices), network capabilities (whether the network supports the UE connecting to the core network through two access network devices simultaneously), UE subscription messages, and operator configuration. If not, and the UE is in a connected state on the 6GC, the 6G-MM sends a UE context release command (i.e., the release command in the aforementioned embodiment) to the 6G-RAN. The specific description of this UE context release command is the same as in the aforementioned embodiment and will not be repeated here.

[0364] Step 1104 is the same as step 603 in the aforementioned embodiment, and will not be described again. After completing step 1104, the UE enters the idle state from the connected state in 6G RAT (or UE and 6GC).

[0365] It should be noted that if, after completing step 1102, 6G-MM determines that it supports UE multi-access based on at least one of the following: UE capabilities, network capabilities, UE subscription messages, operator configuration, etc., then steps 1103 to 1104 need not be executed.

[0366] In the above embodiments, after a terminal in an idle state (i.e., the first RAT) switches to the 5GS and establishes a connection with the AMF (first core network device), the AMF can notify the 6G-MM (second core network device) associated with it and serving the same terminal to release the UE's NAS connection on the 6G access network (i.e., switch the second RAT from a connected state to an idle state). In this way, network-side interaction ensures that a legacy UE only accesses one access network at a time, reducing the impact of connection management on the terminal after merged registration and ensuring backward compatibility for legacy UEs.

[0367] In one embodiment, after the terminal sends a first merge registration request to the second core network device through the access network device corresponding to the second RAT to complete the merge registration of the first RAT and the second RAT, the terminal can be in an idle state. If the first core network device determines that there is downlink data or downlink signaling (such as NAS messages or signaling) that needs to be sent to the terminal through the access network device corresponding to the first RAT, the first core network device can trigger the terminal to initiate the establishment of a connection with the first core network device through the access network device corresponding to the first RAT by paging.

[0368] Before the first core network device receives the first request sent by the terminal through the access network device corresponding to the first RAT, the method further includes: the first core network device sending a third paging message to the access network device corresponding to the first RAT. After the access network device corresponding to the first RAT receives the third paging message, it may also send the first paging message to the terminal. Before the terminal sends the first request to the first core network device through the access network device corresponding to the first RAT, the method further includes: the terminal receiving the first paging message from the access network device corresponding to the first RAT.

[0369] The third paging message, the first paging message, and their related descriptions are the same as in the aforementioned embodiments, and will not be repeated here.

[0370] After the terminal receives the first paging message, it can perform the process of sending a first request to the first core network device through the access network device corresponding to the first RAT. In this embodiment, the content carried by the first request and the processing of the first core network device after receiving the first request are the same as in the previous embodiments, and will not be described again.

[0371] After the first core network device receives the first request sent by the terminal under the first RAT, the method further includes: when the terminal is in a connected state under the first RAT, the first core network device sends a second notification message to the second core network device. The related descriptions of the second notification message and the related processing by the second core network device after receiving the second notification message are the same as in the aforementioned embodiments and will not be repeated here.

[0372] Based on Figure 10, and in conjunction with Figure 12, after the UE performs 5GC and 6GC (i.e., in 5G RAT and 6G RAT) merged registration through 6G-RAN (i.e., the access network device corresponding to the second RAT), if there is downlink data or signaling message on 5GC (i.e., the core network side of the first communication system) that needs to be sent to the UE through 5G-RAN (the access network device corresponding to the first RAT), the AMF (i.e., the first core network device) can page the UE on 5G-RAN, triggering the UE to initiate a service request process on 5G-RAN and establish a NAS connection with the AMF.

[0373] The explanation of step 1200 is the same as that of step 1100, and will not be repeated here.

[0374] Step 1201: The AMF sends a paging message (i.e., the third paging message in the aforementioned embodiment) to the 5G-RAN, the paging message containing at least one of the following information:

[0375] If the same NAS identifier (e.g., GUTI) for paging is assigned to the UE in both 5G and 6G during the merged registration, then this GUTI (i.e., the NAS identifier for paging corresponding to the first RAT and the second RAT) (or TMSI (obtained by truncating the GUTI)) is used to page the UE; if different NAS identifiers for paging are assigned to the UE in 5G and 6G during the merged registration, then the 5G-GUTI (i.e., the NAS identifier for paging corresponding to the first RAT) is used to page the UE.

[0376] The TAI list corresponding to 5G RAT is used to assist 5G-RAN in determining the paging area.

[0377] The fourth indication information can be a new paging cause, such as a paging case for interworking or a paging cause for multi-access, which indicates that there is downlink data or signaling message that needs to be sent to the UE through the 5G-RAN, and the UE needs to establish a connection with the MM on the 5G-RAN.

[0378] Step 1202: The 5G-RAN sends a paging message to the UE (i.e., the first paging message in the aforementioned embodiment). The paging message carries at least one of the following information: the UE's identification information, which is the same as in step 1201 and will not be described again; and fourth indication information.

[0379] Step 1203: After receiving a paging message in 5G-RAN, if the UE does not support multiple access (does not support simultaneous access to multiple access network devices, or does not support simultaneous connection to the core network through multiple access network devices (access network devices corresponding to multiple RATs)), and the UE is currently in a connected state (for example, the UE is currently in a connected state with 6GC through 6G-RAN (access network device corresponding to the second RAT), the UE can perform one of the following two actions:

[0380] The first process involves executing steps 1203 to 1206, which are the same as steps 1101 to 1104 in the previous example and will not be repeated.

[0381] In the second process, the UE notifies the 6G-RAN via an RRC message that it has switched to the access network device corresponding to another RAT and needs to leave the RRC-CONNECTED state. The specific description of the RRC message is the same as in the aforementioned example step 501, and will not be repeated here. The 6G-RAN sends a UE context release request to the 6G-MM (second core network device) to request the release of the connection corresponding to the UE. This UE context release request is the same as in the aforementioned example step 502, and will not be repeated here. The 6G-MM sends a UE context release command (i.e., the release command in the aforementioned embodiment) to the 6G-RAN. The 6G-RAN sends an RRC release message to the UE to release the RRC connection between the UE and the UE. The UE enters or switches from the connected state to the idle state under the 6G RAT. The UE sends a service request message (i.e., the first request) to the AMF through the 5G-RAN to establish a connection (NAS connection) with the AMF. Subsequently, the AMF sends a notification message (i.e., the second notification message) to the 6G-MM to indicate that the UE has successfully switched to the 5GC.

[0382] The above embodiments are mainly used when the terminal has no NAS connection to the network under multiple RATs, or when the terminal is in a connected state on one RAT (such as the second RAT) and in an idle state on another (such as the first RAT). The first core network device can directly page the terminal without having directly communicated with it, which makes it convenient for the application server to directly switch to the new RAT (i.e., the first RAT) when sending data, without the need for an additional registration process. For example, if the AF detects congestion on the 6G access network, it can directly switch to the 5G access network to send data to the terminal, improving the user experience.

[0383] In one embodiment, after the terminal sends a first merge registration request to the second core network device through the access network device corresponding to the second RAT to complete the merge registration of the first RAT and the second RAT, and the terminal is in an idle state in the first RAT and also in an idle state in the second RAT, if the first core network device determines that there is downlink data or downlink signaling (such as NAS messages or signaling) that needs to be sent to the terminal through the access network device corresponding to the first RAT, the first core network device can trigger the terminal to initiate the establishment of a connection with the first core network device through the access network device corresponding to the first RAT through the second core network device.

[0384] Before the first core network device receives the first request sent by the terminal under the first RAT, the method further includes: the first core network device sending a fourth paging message to the second core network device, wherein the fourth paging message carries at least one of the following: the registration area corresponding to the first RAT, and fourth indication information, wherein the fourth indication information is used to instruct the terminal to establish a connection with the first core network device through the access network device corresponding to the first RAT.

[0385] The method by which the first core network device determines the second core network device is the same as in the aforementioned embodiments, and will not be repeated here.

[0386] The description of the fourth instruction information is the same as that in the aforementioned embodiments, and will not be repeated here.

[0387] The function of the registration area corresponding to the first RAT can be to help the second core network device determine the paging area.

[0388] It should be noted that the above is only an illustrative example. The fourth paging message may also carry other content, such as the terminal identifier, etc. This article does not limit or exhaust all the possible contents that the fourth paging message may carry.

[0389] After receiving the fourth paging message from the first core network device, the second core network device can perform the following processing: the second core network device sends a fifth paging message to the access network device corresponding to the second RAT, wherein the fifth paging message carries one of the following: the NAS identifier for paging corresponding to the second RAT, or the NAS identifier for paging corresponding to the first RAT and the second RAT.

[0390] Optionally, the access network device corresponding to the second RAT can be a uniquely identified access network device, such as being referred to as the second access network device. The second core network device sending a fifth paging message to the access network device corresponding to the second RAT can be: the second core network device sending a fifth paging message to the second access network device.

[0391] The second core network device may determine the second access network device by selecting the access network device located in the registration area (TAI) last accessed by the terminal within the second RAT as the second access network device. This is merely an illustrative example of how the second core network device determines the second access network device, and does not limit or exhaust all possible methods by which the second core network device determines the second access network device.

[0392] Optionally, the access network device corresponding to the second RAT can be all access network devices within the registration area corresponding to the second RAT. The second core network device sending a fifth paging message to the access network device corresponding to the second RAT can be: the second core network device sending the fifth paging message to all access network devices within the registration area corresponding to the second RAT.

[0393] If, during the terminal merging registration process, the second core network device and the first core network device assign NAS identifiers for paging corresponding to the first RAT and the second RAT to the terminal, then the fifth paging message can carry the NAS identifiers for paging corresponding to the first RAT and the second RAT. If, during the terminal merging registration process, the second core network device and the first core network device assign the terminal a NAS identifier for paging corresponding to the second RAT and a NAS identifier for paging corresponding to the first RAT, respectively, then the fifth paging message carries the identifier for paging corresponding to the second RAT.

[0394] Optionally, the fifth paging message may also carry a fourth instruction message.

[0395] The fifth paging message may also carry other content, such as a registration area. This registration area can be the registration area corresponding to the second RAT, or the registration area corresponding to both the second and first RATs. This registration area corresponding to the second RAT, or the registration area corresponding to both the second and first RATs, is used to assist the access network device corresponding to the second RAT in determining the paging area. This document does not limit or exhaustively list all the possible contents that the fifth paging message may carry.

[0396] After receiving the fifth paging message, the access network device corresponding to the second RAT can also send a second paging message to the terminal. Before the terminal sends the first request to the first core network device through the access network device corresponding to the first RAT, the method further includes: when the terminal is in an idle state with the second RAT, the terminal receives a second paging message from the access network device corresponding to the second RAT, wherein the second paging message carries one of the following: a NAS identifier for paging corresponding to the second RAT, or a NAS identifier for paging corresponding to both the first RAT and the second RAT.

[0397] The access network device corresponding to the second RAT can be any one of the aforementioned second access network devices or any one of all access network devices corresponding to the second RAT.

[0398] The NAS identifier used for paging carried in the second paging message is the same as that in the fifth paging message, and will not be described again.

[0399] Optionally, if the fifth paging message carries the fourth indication information, the second paging message also carries the fourth indication information, wherein the fourth indication information is used to instruct the terminal to establish a connection with the first core network device through the access network device corresponding to the first RAT. The relevant description of this fourth indication information is the same as in the aforementioned embodiments and will not be repeated.

[0400] After the terminal receives the first paging message, it can perform the process of sending a first request to the first core network device through the access network device corresponding to the first RAT. In this embodiment, the content carried by the first request and the processing of the first core network device after receiving the first request are the same as in the previous embodiments, and will not be described again.

[0401] Since the terminal is in an idle state under the second RAT in this embodiment, after the first core network device receives the first request sent by the terminal under the first RAT, it may not send a message to the second core network device; or it may execute the process of the first core network device sending a second notification message to the second core network device, but after the second core network device receives the second notification message, it may not execute the process of switching the terminal from the connected state to the idle state under the second RAT.

[0402] Based on Figure 10, and in conjunction with Figure 13, after the UE performs merged registration through 6G-RAN (i.e., the access network device corresponding to the second RAT), if the UE is idle on both 5GC and 6GC, the AMF (i.e., the first core network device) can send a paging message to 6G-MM (the second core network device). The 6G-MM can then page the UE on 6G-RAN (the access network device corresponding to the second RAT), triggering the UE to initiate a service request process on 5G-RAN (the access network device corresponding to the first RAT) and establish a NAS connection with the AMF. This is illustrated by example.

[0403] Step 1300 is the same as step 1100, so it will not be repeated here.

[0404] Step 1301: The AMF sends a paging message (i.e., the fourth paging message in the aforementioned embodiment) to the 6G-MM, where the 6G-MM is the MM associated with the AMF in the UE merge registration. The paging message carries at least one of the following: UE identification information, such as GUTI, SUPI, SUCI, etc.; registration area, used to assist the 6G-MM in determining the paging area; and fourth indication information.

[0405] Step 1302: The 6G-MM sends a paging message (i.e., the fifth paging message in the aforementioned embodiment) to the 6G-RAN. The 6G access network device can be any access network device within the UE's registration area, or it can be the access network device corresponding to the TAI last accessed by the UE. The paging message carries at least one of the following:

[0406] If the same NAS identifier (e.g., GUTI) for paging is assigned to the UE in both 5G and 6G during the merged registration, then this GUTI (i.e., the NAS identifier for paging corresponding to the first RAT and the second RAT) (or TMSI (obtained by truncating the GUTI)) is used to page the UE; if different NAS identifiers for paging are assigned to the UE in 5G and 6G during the merged registration, then the 6G-GUTI (i.e., the NAS identifier for paging corresponding to the second RAT) is used to page the UE.

[0407] The TAI list corresponding to 6G RAT is used to assist 6G-RAN in determining the paging area;

[0408] Fourth instruction information.

[0409] Step 1303: The 6G-RAN determines the paging area based on the UE's registration area and sends a paging message (i.e., the second paging message in the aforementioned embodiment) to the UE within the paging area. The paging message carries at least one of the following: the UE's identification information (same as in step 1302), and fourth indication information.

[0410] Steps 1304 to 1305 are the same as steps 1101 to 1102 in the previous example, and will not be repeated.

[0411] This embodiment is mainly used when the UE has no NAS connection to the network under multiple RATs and the AMF (first core network device) fails to page the UE. For example, the UE is not currently under the coverage of the 5G access network device or is not in the tracking area corresponding to the 5G RAT in the registration area. The AMF can forward the paging message to the 6G-MM (second core network device) and use the 6G-MM to page the UE through the 6G-RAN, so as to avoid the downlink data not being sent to the UE in time due to the AMF's inability to page the UE.

[0412] In some embodiments, after the terminal sends a first merge registration request to the second core network device through the access network device corresponding to the second RAT to complete the merge registration of the first RAT and the second RAT, the terminal can be in an idle state. If the first core network device determines that there is downlink data or downlink signaling (such as NAS messages or signaling) that needs to be sent to the terminal through the access network device corresponding to the first RAT, the first core network device can trigger the terminal to initiate the establishment of a connection with the first core network device through the access network device corresponding to the first RAT through the second core network device.

[0413] Before the first core network device receives the first request sent by the terminal under the first RAT, the process further includes: the first core network device sending a fourth paging message to the second core network device.

[0414] The method by which the first core network device determines the second core network device is the same as in the aforementioned embodiments, and the description of the fourth indication information is the same as in the aforementioned embodiments, so there will be no further repetition.

[0415] After receiving the fourth paging message from the first core network device, the second core network device can perform the following processing: the second core network device sends a fifth paging message to the access network device corresponding to the second RAT, wherein the fifth paging message carries one of the following: the NAS identifier for paging corresponding to the second RAT, or the NAS identifier for paging corresponding to the first RAT and the second RAT.

[0416] In one embodiment, after receiving a fourth paging message from the first core network device, the second core network device can determine whether it supports the terminal simultaneously connecting to the core network (e.g., the first core network device and the second core network device) through the access network devices corresponding to the first RAT and the second RAT, respectively. If it is determined that the terminal supports simultaneously connecting to the core network through the access network devices corresponding to the first RAT and the second RAT, and the terminal is in a connected state at the second RAT and in an idle state at the first RAT, the second core network device sends a first notification message to the terminal through the access network device corresponding to the second RAT. Accordingly, before the terminal sends a first request to the first core network device through the access network device corresponding to the first RAT, the method further includes: when the terminal is in a connected state at the second RAT, the terminal receives a first notification message from the core network through the access network device corresponding to the second RAT, wherein the first notification message carries third indication information, which is used to instruct the terminal to establish a connection with the first core network device through the access network device corresponding to the first RAT.

[0417] In this embodiment, the terminal receiving the first notification message from the core network through the access network device corresponding to the second RAT specifically means that the terminal receives the first notification message from the second core network device through the access network device corresponding to the second RAT.

[0418] The specific method by which the second core network device determines whether it supports the terminal to connect to the core network simultaneously through the access network devices corresponding to the first RAT and the second RAT is the same as in the aforementioned embodiments and will not be repeated here.

[0419] The description of the first notification message is the same as that in the aforementioned embodiments, and will not be repeated here.

[0420] After the terminal receives the first notification message, it can execute the process of sending a first request to the first core network device through the access network device corresponding to the first RAT. The content carried by the first request and the processing of the first core network device after receiving the first request are the same as in the previous embodiments, and will not be described again.

[0421] After receiving the first request sent by the terminal under the first RAT, the first core network device further includes: when the terminal is in a connected state under the first RAT, the first core network device sends a second notification message to the second core network device. The relevant description of the second notification message is the same as in the previous embodiment and will not be repeated. It should be noted that if the terminal supports multiple access, after receiving the second notification message, the second core network device may not control the terminal to switch from a connected state to an idle state under the second RAT, or it may control the terminal to switch from a connected state to an idle state under the second RAT; this embodiment does not impose any limitations.

[0422] In one embodiment, after receiving a fourth paging message from the first core network device, if the second core network device determines that it does not support the terminal simultaneously connecting to the core network through the access network devices corresponding to the first RAT and the second RAT respectively, and the terminal is in a connected state on the second RAT and in an idle state on the first RAT, the second core network device may send a release command to the access network device corresponding to the second RAT. This release command may specifically be a UE CONTEXT RELEASE COMMAND (UE context release command), or it may be other command types; not all possible names of this release command are limited or exhaustively listed here.

[0423] After the second core network device sends a release command to the access network device corresponding to the second RAT, the terminal on the second core network device side can be in an idle state in the second RAT (or the access network device corresponding to the second RAT).

[0424] Correspondingly, after receiving the release command, the access network device corresponding to the second RAT can release the resources related to the terminal, such as releasing signaling and user data transmission resources (or user plane resources); then the access network device corresponding to the second RAT sends an RRC release message to the terminal.

[0425] The description of the RRC release message is the same as that in the previous embodiments, and will not be repeated here.

[0426] Specifically, the terminal receives the first notification message from the core network through the access network device corresponding to the second RAT: the terminal receives the first notification message from the second core network device through the access network device corresponding to the second RAT.

[0427] The specific method by which the second core network device determines whether it supports the terminal to connect to the core network simultaneously through the access network devices corresponding to the first RAT and the second RAT is the same as in the aforementioned embodiments and will not be repeated here.

[0428] The description of the first notification message is the same as that in the aforementioned embodiments, and will not be repeated here.

[0429] After the terminal receives the RRC release message from the access network device corresponding to the second RAT, it can send a first request to the first core network device through the access network device corresponding to the first RAT. The content carried by the first request and the processing by the first core network device after receiving the first request are the same as in the previous embodiments, and will not be described again.

[0430] After receiving the first request sent by the terminal under the first RAT, the first core network device further includes: when the terminal is in a connected state under the first RAT, the first core network device sends a second notification message to the second core network device. It should be noted that in this embodiment, the terminal does not support multiple access. After receiving the second notification message, the second core network device can control the terminal to switch from a connected state to an idle state under the second RAT. The process of the second core network device switching the terminal from a connected state to an idle state under the second RAT is the same as in the previous embodiment and will not be described again.

[0431] Based on Figure 10, and in conjunction with Figure 14, after the UE performs merged registration through 6G-RAN (i.e., the access network device corresponding to the second RAT), if the UE is in an idle state in 5GC and in a connected state in 6GC, the AMF (i.e., the first core network device) can send a paging message to 6G-MM (the second core network device). The 6G-MM can then send a NAS notification message to the UE through 6G-RAN, triggering the UE to initiate a service request process on 5G-RAN (the access network device corresponding to the first RAT) and establish a NAS connection with the AMF. This process is illustrated as follows:

[0432] Steps 1400 to 1401 are the same as steps 1300 to 1301 in the previous example, and will not be described again.

[0433] 6G-MM, based on whether the UE and / or network support the UE simultaneously connecting to the core network through two access network devices, can be divided into the following two cases:

[0434] Scenario 1: If multiple UE access is supported, then 6G-MM sends a downlink NAS notification message (i.e., the first notification message in the aforementioned embodiment) to the UE. The downlink NAS message contains at least one of the following parameters: UE identification information, such as GUTI, SUPI, etc.; and third indication information, used to instruct the UE to establish a connection with the core network on another access network device (e.g., 5G-RAN) corresponding to another RAT.

[0435] Case 2: If UE multi-access is not supported, then steps 1402 to 1403 are executed. These steps 1402 to 1403 are the same as steps 1103 to 1104 in the previous example, and will not be repeated.

[0436] Steps 1404 to 1405 are the same as steps 1101 to 1102 in the previous example, and will not be repeated.

[0437] The above embodiments are mainly used when the UE is in a connected state on 6GC but in an idle state on 5GC, and the AMF fails to page the UE. For example, if the UE is not currently under the coverage of 5G-RAN or is not in the tracking area corresponding to the 5G RAT in the registered area, the AMF can forward the paging message to 6G-MM. The 6G-MM can directly send a NAS message through 6G-RAN to notify the UE to connect to the AMF through the 5G access network device, and can directly release the connection between the UE and 6G-MM. Thus, the UE can actively find or move to the coverage of the 5G access network device to establish a connection with the AMF, so that the AMF can switch the communication system serving the UE as needed, avoiding downlink data not arriving at the UE on time due to the AMF's inability to establish a connection with the UE for a long time.

[0438] The solution provided in this application allows a terminal to merge and register with the core network across multiple RATs using a single merge registration request. Then, when the terminal's first RAT is idle, the terminal can directly initiate a first request to the core network device via the access network device corresponding to that first RAT to establish a connection between the terminal and the core network device. This allows the terminal to achieve merged registration across multiple RATs with only one registration request. Furthermore, when any one RAT is idle, access to the core network can be achieved simply by initiating a connection establishment request through the access network device corresponding to that RAT. This avoids the signaling overhead caused by repeatedly executing the mobility registration process. Especially in scenarios involving the collaborative operation of multiple systems or networks, this improves the communication efficiency between the terminal and various networks or systems. It also provides a basis for the terminal to switch between different systems when multiple systems and systems corresponding to multiple RATs are working collaboratively, improving the efficiency of switching between different systems.

[0439] Finally, considering the relevant technologies, in existing interworking processes, whether in single-registration or dual-registration mode, the UE needs to perform a registration process in both networks. For example, in single-registration mode, when the UE registers in the 5GS through the initial registration process, and then moves from the 5GS to the EPS, in addition to the session management-related processes, the UE also needs to perform a TAU process in the EPS. Similarly, when the UE initially registers in the EPS through initial attach, and then moves from the EPS to the 5GS, in addition to the session management-related processes, it also needs to perform a Mobility Registration Update. In dual-registration mode, if the UE wants to move from the EPS to the 5GS, it needs to register on the 5GS, and if it wants to move from the 5GS to the EPS, it also needs to register on the EPS. Moreover, in the single-registration interworking process, the UE also needs to perform identification information mapping, i.e., the mapping between EPS-GUTI and 5G-GUTI, and the mapping between the MME and AMF also needs to perform UE context mapping, including the mapping of the security UE context. Furthermore, in dual-registration mode, two sets of UE contexts need to be maintained. To simplify the interworking process, reduce the amount of signaling interaction between the UE and the network, and avoid the UE performing multiple mobility registration updates or TAU procedures when switching between 4GS, 5GS, and 6GS systems, the solution provided in this application allows the UE to register multiple accesses to 5G and / or 6G networks simultaneously through a single NAS message. Subsequently, when the UE switches between different systems, it does not need to repeatedly initiate the mobility registration process, but can switch the UE's connection status under different accesses through service requests, redirections, and other processes.

[0440] Figure 15 is a schematic diagram of the composition structure of a terminal according to an embodiment of this application, including:

[0441] The first communication unit 1501 is configured to send a first request to the first core network device through the access network device corresponding to the first RAT after the terminal sends a first merge registration request to the core network through the access network device corresponding to the second RAT to complete the merge registration of the first RAT and the second RAT. The first request is used to request to establish a connection with the first core network device through the access network device corresponding to the first RAT.

[0442] The first communication unit is configured to receive an RRC release message from the access network device corresponding to the second RAT when the terminal is in a connected state, wherein the RRC release message is used to indicate the release of the RRC connection between the terminal and the access network device corresponding to the second RAT.

[0443] The first communication unit is configured to send first indication information, wherein the first indication information is configured to indicate the release of the connection between the terminal and the core network through the access network device corresponding to the second RAT.

[0444] The first communication unit is configured to receive an RRC release message from the access network device corresponding to the second RAT when the terminal is in a connected state, wherein the RRC release message is used to indicate the release of the RRC connection between the terminal and the access network device corresponding to the second RAT.

[0445] The first communication unit is configured to receive a first paging message from the access network device corresponding to the first RAT, wherein the first paging message carries one of the following: a NAS identifier for paging corresponding to the first RAT, or a NAS identifier for paging corresponding to the first RAT and the second RAT.

[0446] The first paging message also carries fourth indication information, wherein the fourth indication information is used to instruct the terminal to establish a connection with the first core network device through the access network device corresponding to the first RAT.

[0447] The first communication unit is configured to receive a first notification message from the core network through the access network device corresponding to the second RAT when the terminal is in a connected state of the second RAT, wherein the first notification message carries third indication information, the third indication information being used to instruct the terminal to establish a connection with the first core network device through the access network device corresponding to the first RAT.

[0448] The RRC release message carries at least one of the following: a core network type parameter, wherein the core network type parameter is used to indicate the core network type to which the terminal switches; and second indication information, wherein the second indication information is used to indicate that the terminal switches to connecting to the core network through the access network device corresponding to the first RAT.

[0449] The first communication unit is configured to receive a second paging message from the access network device corresponding to the second RAT when the terminal is in an idle state, wherein the second paging message carries one of the following: a NAS identifier for paging corresponding to the second RAT, the first RAT, and a NAS identifier for paging corresponding to the second RAT.

[0450] The second paging message also carries fourth indication information, which is used to instruct the terminal to establish a connection with the first core network device through the access network device corresponding to the first RAT.

[0451] The first request carries at least one of the following: a NAS identifier for paging corresponding to the first RAT; NAS identifiers for paging corresponding to the first RAT and the second RAT; an identifier of a first session, wherein the first session is a session that the terminal requests to activate on the first RAT, or the first session is a session that switches from the second RAT to the first RAT.

[0452] The first communication unit is configured to send a first merge registration request to the core network through the access network device corresponding to the second RAT, wherein the first merge registration request is used to request the establishment of the terminal context for the terminal in the first RAT and the second RAT; and to receive a first merge registration acceptance message from the core network through the access network device corresponding to the second RAT, wherein the first merge registration acceptance message is used for the terminal to determine that the merge registration of the first RAT and the second RAT has been completed.

[0453] The first merged registration request carries at least one of the following: the identifier of the terminal, the registration type, the type of the first RAT, the identifier of the access network device corresponding to the first RAT, the tracking area information corresponding to the first RAT, and the identifier of the cell corresponding to the access network device corresponding to the first RAT.

[0454] The first merged registration acceptance message carries at least one of the following: registration type, NAS identifier for paging corresponding to the second RAT, NAS identifier for paging corresponding to the first RAT, NAS identifiers for paging corresponding to the first RAT and the second RAT, registration area corresponding to the second RAT, registration area corresponding to the first RAT, registration areas corresponding to the first RAT and the second RAT, and the registration status of the terminal in the first RAT.

[0455] Figure 16 is a schematic diagram of the composition structure of a first core network device according to an embodiment of this application, including:

[0456] The second communication unit is configured to receive a first request sent by the terminal through the access network device corresponding to the first RAT after the terminal sends a first merge registration request to the core network through the access network device corresponding to the second RAT to complete the merge registration of the first RAT and the second RAT. The first request is used to request to establish a connection with the first core network device through the access network device corresponding to the first RAT.

[0457] The second communication unit is configured to send a release command to the access network device corresponding to the second RAT when the terminal is in a connected state, wherein the release command is used to instruct the access network device corresponding to the second RAT to release the terminal-related resources.

[0458] The second communication unit is configured to receive first indication information from the terminal, wherein the first indication information is configured to indicate the release of the connection between the terminal and the first core network device through the access network device corresponding to the second RAT.

[0459] The second communication unit is configured to send a release command to the access network device corresponding to the second RAT when the terminal is in a connected state, wherein the release command is used to instruct the access network device corresponding to the second RAT to release the terminal-related resources.

[0460] The second communication unit is configured to send a second notification message to a second core network device when the terminal is in a connected state under the first RAT. The second notification message carries network switching indication information, which indicates at least one of the following: the terminal establishes a connection with the first core network device through the access network device corresponding to the first RAT; or the terminal is in a connected state under the first RAT.

[0461] The second communication unit is configured to send a third paging message to the access network device corresponding to the first RAT, wherein the third paging message carries one of the following: a NAS identifier for paging corresponding to the first RAT, or a NAS identifier for paging corresponding to both the first RAT and the second RAT.

[0462] The third paging message also carries fourth indication information, wherein the fourth indication information is used to instruct the terminal to establish a connection with the first core network device through the access network device corresponding to the first RAT.

[0463] The second communication unit is configured to send a fourth paging message to the second core network device, wherein the fourth paging message carries at least one of the following: the registration area corresponding to the first RAT and fourth indication information, wherein the fourth indication information is used to instruct the terminal to establish a connection with the first core network device through the access network device corresponding to the first RAT.

[0464] The second communication unit is configured to send a first notification message to the terminal via the access network device corresponding to the second RAT when the terminal is in a connected state via the second RAT. The first notification message carries third indication information, which is used to instruct the terminal to establish a connection with the first core network device via the access network device corresponding to the first RAT.

[0465] The release command carries at least one of the following: the Next Generation Application Protocol (NGAP) identifier of the terminal corresponding to the first core network device, the NGAP identifier of the terminal corresponding to the access network device corresponding to the second RAT, and the release reason.

[0466] The first request carries at least one of the following: a NAS identifier for paging corresponding to the first RAT; NAS identifiers for paging corresponding to the first RAT and the second RAT; an identifier of a first session, wherein the first session is a session that the terminal requests to activate on the first RAT, or the first session is a session that switches from the second RAT to the first RAT.

[0467] The second communication unit is configured to receive a first merge registration request sent by the terminal through the access network device corresponding to the second RAT, wherein the first merge registration request is used to request the establishment of the terminal context for the terminal under the first RAT and the second RAT; and to send a first merge registration acceptance message to the terminal through the access network device corresponding to the second RAT, wherein the first merge registration acceptance message is used for the terminal to determine that the merge registration of the first RAT and the second RAT has been completed.

[0468] The second communication unit is used to send a registration message to the Unified Data Management (UDM), wherein the registration message is used to record at least one of the following in the UDM: the first core network device serves the terminal, and the first RAT and the second RAT are merged and registered together.

[0469] The first merged registration request carries at least one of the following: the identifier of the terminal, the registration type, the type of the first RAT, the identifier of the access network device corresponding to the first RAT, the tracking area information corresponding to the first RAT, and the identifier of the cell corresponding to the access network device corresponding to the first RAT.

[0470] The first merged registration acceptance message carries at least one of the following: registration type, NAS identifier for paging corresponding to the second RAT, NAS identifier for paging corresponding to the first RAT, NAS identifiers for paging corresponding to the first RAT and the second RAT, registration area corresponding to the second RAT, registration area corresponding to the first RAT, registration areas corresponding to the first RAT and the second RAT, and the registration status of the terminal in the first RAT.

[0471] The second communication unit is configured to receive a second merge registration request from a second core network device, wherein the second merge registration request is configured to request the first core network device to establish an association with the second core network device and to establish the terminal context for the terminal under the first RAT; and to send a second merge registration acceptance message to the second core network device, wherein the second merge registration acceptance message is configured to indicate acceptance of merge registration.

[0472] The second merged registration request carries at least one of the following: the NAS identifier for paging corresponding to the second RAT, the identification information of the second core network device, and the registration area corresponding to the second RAT, wherein the identification information of the second core network device is used by the first core network device to establish an association between the first core network device and the second core network device.

[0473] The second merged registration acceptance message carries at least one of the following: the NAS identifier for paging corresponding to the first RAT, the identification information of the first core network device, and the registration area corresponding to the first RAT, wherein the identification information of the first core network device is used by the second core network device to establish an association between the first core network device and the second core network device.

[0474] The device in this application embodiment can realize the corresponding functions of the various devices in the foregoing communication method embodiments. The processes, functions, implementation methods, and beneficial effects of each module (sub-module, unit, or component, etc.) in this device can be found in the corresponding descriptions in the above method embodiments, and will not be repeated here. It should be noted that the functions described for each module (sub-module, unit, or component, etc.) in the device of this application embodiment can be implemented by different modules (sub-modules, units, or components, etc.) or by the same module (sub-module, unit, or component, etc.).

[0475] Figure 17 is a schematic structural diagram of a communication device 1700 according to an embodiment of this application. The communication device 1700 includes a processor 1710, which can call and run computer programs from a memory to enable the communication device 1700 to implement the methods in the embodiments of this application. In one possible implementation, the communication device 1700 may further include a memory 1720. The processor 1710 can call and run computer programs from the memory 1720 to enable the communication device 1700 to implement the methods in the embodiments of this application. The memory 1720 may be a separate device independent of the processor 1710, or it may be integrated into the processor 1710. In one possible implementation, the communication device 1700 may further include a transceiver 1730, which the processor 1710 can control to communicate with other devices. Specifically, it can send information or data to other devices, or receive information or data sent by other devices. The transceiver 1730 may include a transmitter and a receiver. The transceiver 1730 may further include antennas, and the number of antennas may be one or more.

[0476] In one possible implementation, the communication device 1700 may be a terminal or a first core network device in the embodiments of this application, and the communication device 1700 may implement the corresponding processes implemented by the terminal or the first core network device in the various methods of the embodiments of this application. For the sake of brevity, these will not be described in detail here.

[0477] Figure 18 is a schematic structural diagram of a chip 1800 according to an embodiment of this application. The chip 1800 includes a processor 1810, which can call and run computer programs from memory to implement the methods in the embodiments of this application. In one possible implementation, the chip 1800 may further include a memory 1820. The processor 1810 can call and run computer programs from the memory 1820 to implement the methods executed by a terminal, a first core network device, or a first access network device in the embodiments of this application. The memory 1820 may be a separate device independent of the processor 1810, or it may be integrated into the processor 1810. In one possible implementation, the chip 1800 may further include an input interface 1830. The processor 1810 can control the input interface 1830 to communicate with other devices or chips; specifically, it can acquire information or data sent by other devices or chips. In one possible implementation, the chip 1800 may further include an output interface 1840. The processor 1810 can control the output interface 1840 to communicate with other devices or chips, specifically, it can output information or data to other devices or chips.

[0478] In one possible implementation, the chip can be applied to the terminal or the first core network device in the embodiments of this application, and the chip can implement the corresponding processes implemented by the terminal or the first core network device in the various methods of the embodiments of this application. For simplicity, these will not be elaborated further here. It should be understood that the chip mentioned in the embodiments of this application can also be called a system-on-a-chip, system chip, chip system, or system-on-a-chip, etc. The processor mentioned above can be a general-purpose processor, a digital signal processor (DSP), a field-programmable gate array (FPGA), an application-specific integrated circuit (ASIC), or other programmable logic devices, transistor logic devices, discrete hardware components, etc. Among them, the general-purpose processor mentioned above can be a microprocessor or any conventional processor, etc. The memory mentioned above can be volatile memory or non-volatile memory, or can include both volatile and non-volatile memory. The non-volatile memory can be read-only memory (ROM), programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), or flash memory. The volatile memory can be random access memory (RAM). It should be understood that the above-described memory is exemplary but not limiting. For example, the memory in the embodiments of this application can also be static random access memory (SRAM), dynamic random access memory (DRAM), synchronous dynamic random access memory (SDRAM), double data rate synchronous dynamic random access memory (DDR SDRAM), enhanced synchronous dynamic random access memory (ESDRAM), synchronous link dynamic random access memory (SLDRAM), and direct memory bus RAM (DR RAM), etc. In other words, the memory in the embodiments of this application is intended to include, but is not limited to, these and any other suitable types of memory.

[0479] It should be understood that the sequence number of each process in the various embodiments of this application does not imply the order of execution; the execution order of each process should be determined by its function and internal logic. 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. The above descriptions are merely specific embodiments of this application, and the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A communication method, comprising: After the terminal sends a first merge registration request to the core network through the access network device corresponding to the second radio access technology (RAT) to complete the merge registration of the first RAT and the second RAT, the terminal sends a first request to the first core network device through the access network device corresponding to the first RAT. The first request is used to request to establish a connection with the first core network device through the access network device corresponding to the first RAT.

2. The method according to claim 1, wherein, Before the terminal sends the first request to the first core network device through the access network device corresponding to the first RAT, it also includes: When the terminal is in a connected state with the second RAT, the terminal receives a Radio Resource Control (RRC) release message from the access network device corresponding to the second RAT, wherein the RRC release message is used to indicate the release of the RRC connection between the terminal and the access network device corresponding to the second RAT.

3. The method according to claim 1 or 2, wherein, Before the terminal receives the RRC release message from the access network device corresponding to the second RAT, it also includes: The terminal sends a first indication message, wherein the first indication message is used to indicate the release of the connection between the terminal and the core network through the access network device corresponding to the second RAT.

4. The method according to claim 1, wherein, After the terminal sends a first request to the first core network device through the access network device corresponding to the first RAT, it further includes: When the terminal is in a connected state with the second RAT, the terminal receives an RRC release message from the access network device corresponding to the second RAT, wherein the RRC release message is used to indicate the release of the RRC connection between the terminal and the access network device corresponding to the second RAT.

5. The method according to any one of claims 1-4, wherein, Before the terminal sends the first request to the first core network device through the access network device corresponding to the first RAT, it also includes: The terminal receives a first paging message from the access network device corresponding to the first RAT, wherein the first paging message carries one of the following: a non-access stratum NAS identifier for paging corresponding to the first RAT, or a NAS identifier for paging corresponding to the first RAT and the second RAT.

6. The method according to claim 5, wherein, The first paging message also carries fourth indication information, wherein the fourth indication information is used to instruct the terminal to establish a connection with the first core network device through the access network device corresponding to the first RAT.

7. The method according to claim 1 or 4, wherein, Before the terminal sends the first request to the first core network device through the access network device corresponding to the first RAT, it also includes: When the terminal is in a connected state in the second RAT, the terminal receives a first notification message from the core network through the access network device corresponding to the second RAT. The first notification message carries third indication information, which is used to instruct the terminal to establish a connection with the first core network device through the access network device corresponding to the first RAT.

8. The method according to any one of claims 2-4, wherein, The RRC release message carries at least one of the following: Core network type parameter, wherein the core network type parameter is used to indicate the core network type to which the terminal switches; The second instruction information is used to instruct the terminal to switch to connecting to the core network through the access network device corresponding to the first RAT.

9. The method according to claim 1, wherein, Before the terminal sends the first request to the first core network device through the access network device corresponding to the first RAT, it also includes: When the terminal is in an idle state with the second RAT, the terminal receives a second paging message from the access network device corresponding to the second RAT, wherein the second paging message carries one of the following: a NAS identifier for paging corresponding to the second RAT, or a NAS identifier for paging corresponding to the first RAT and the second RAT.

10. The method according to claim 9, wherein, The second paging message also carries fourth indication information, which is used to instruct the terminal to establish a connection with the first core network device through the access network device corresponding to the first RAT.

11. The method according to any one of claims 1-10, wherein, The first request carries at least one of the following: The NAS identifier used for paging corresponds to the first RAT; The NAS identifiers used for paging correspond to the first RAT and the second RAT; The identifier of the first session, wherein the first session is a session in which the terminal requests activation on the first RAT, or the first session is a session switched from the second RAT to the first RAT.

12. The method according to any one of claims 1-11, further comprising: The terminal sends a first merge registration request to the core network through the access network device corresponding to the second RAT, wherein the first merge registration request is used to request the establishment of the terminal context for the terminal in the first RAT and the second RAT; The terminal receives a first merge registration acceptance message from the core network through the access network device corresponding to the second RAT, wherein the first merge registration acceptance message is used by the terminal to determine that the merge registration of the first RAT and the second RAT has been completed.

13. The method according to claim 12, wherein, The first merged registration request carries at least one of the following: the identifier of the terminal, the registration type, the type of the first RAT, the identifier of the access network device corresponding to the first RAT, the tracking area information corresponding to the first RAT, and the identifier of the cell corresponding to the access network device corresponding to the first RAT.

14. The method according to claim 12 or 13, wherein, The first merged registration acceptance message carries at least one of the following: registration type, NAS identifier for paging corresponding to the second RAT, NAS identifier for paging corresponding to the first RAT, NAS identifiers for paging corresponding to the first RAT and the second RAT, registration area corresponding to the second RAT, registration area corresponding to the first RAT, registration areas corresponding to the first RAT and the second RAT, and the registration status of the terminal in the first RAT.

15. A communication method, comprising: After the terminal sends a first merge registration request to the core network through the access network device corresponding to the second RAT to complete the merge registration of the first RAT and the second RAT, the first core network device receives a first request sent by the terminal through the access network device corresponding to the first RAT, wherein the first request is used to request to establish a connection with the first core network device through the access network device corresponding to the first RAT.

16. The method according to claim 15, wherein, Before the first core network device receives the first request sent by the terminal through the access network device corresponding to the first RAT, it also includes: When the terminal is in a connected state in the second RAT, the first core network device sends a release command to the access network device corresponding to the second RAT, wherein the release command is used to instruct the access network device corresponding to the second RAT to release the terminal-related resources.

17. The method according to claim 16, wherein, Before the first core network device sends a release command to the access network device corresponding to the second RAT, the process also includes: The first core network device receives a first indication information from the terminal, wherein the first indication information is used to indicate the release of the connection between the terminal and the first core network device through the access network device corresponding to the second RAT.

18. The method according to claim 15, wherein, After the first core network device receives the first request sent by the terminal through the access network device corresponding to the first RAT, it further includes: When the terminal is in a connected state in the second RAT, the first core network device sends a release command to the access network device corresponding to the second RAT, wherein the release command is used to instruct the access network device corresponding to the second RAT to release the terminal-related resources.

19. The method according to claim 15, wherein, After the first core network device receives the first request sent by the terminal under the first RAT, it also includes: When the terminal is in a connected state under the first RAT, the first core network device sends a second notification message to the second core network device. The second notification message carries network switching indication information, which indicates at least one of the following: the terminal establishes a connection with the first core network device through the access network device corresponding to the first RAT; or the terminal is in a connected state under the first RAT.

20. The method according to any one of claims 15, 17-19, wherein, Before the first core network device receives the first request sent by the terminal through the access network device corresponding to the first RAT, it also includes: The first core network device sends a third paging message to the access network device corresponding to the first RAT, wherein the third paging message carries one of the following: a NAS identifier for paging corresponding to the first RAT, or a NAS identifier for paging corresponding to the first RAT and the second RAT.

21. The method according to claim 20, wherein, The third paging message also carries fourth indication information, wherein the fourth indication information is used to instruct the terminal to establish a connection with the first core network device through the access network device corresponding to the first RAT.

22. The method according to claim 19, wherein, Before the first core network device receives the first request sent by the terminal under the first RAT, it also includes: The first core network device sends a fourth paging message to the second core network device, wherein the fourth paging message carries at least one of the following: the registration area corresponding to the first RAT and fourth indication information, wherein the fourth indication information is used to instruct the terminal to establish a connection with the first core network device through the access network device corresponding to the first RAT.

23. The method according to claim 15 or 18, wherein, Before the first core network device receives the first request sent by the terminal under the first RAT, it also includes: When the terminal is in a connected state with the second RAT, the first core network device sends a first notification message to the terminal through the access network device corresponding to the second RAT. The first notification message carries third indication information, which is used to instruct the terminal to establish a connection with the first core network device through the access network device corresponding to the first RAT.

24. The method according to any one of claims 16-18, wherein, The release command carries at least one of the following: the Next Generation Application Protocol (NGAP) identifier of the terminal corresponding to the first core network device, the NGAP identifier of the terminal corresponding to the access network device corresponding to the second RAT, and the release reason.

25. The method according to any one of claims 15-24, wherein, The first request carries at least one of the following: The NAS identifier used for paging corresponds to the first RAT; The NAS identifiers used for paging correspond to the first RAT and the second RAT; The identifier of the first session, wherein the first session is a session in which the terminal requests activation on the first RAT, or the first session is a session switched from the second RAT to the first RAT.

26. The method according to any one of claims 15-18, further comprising: The first core network device receives a first merged registration request sent by the terminal through the access network device corresponding to the second RAT, wherein the first merged registration request is used to request the establishment of the terminal context for the terminal under the first RAT and the second RAT; The first core network device sends a first merge registration acceptance message to the terminal through the access network device corresponding to the second RAT, wherein the first merge registration acceptance message is used by the terminal to determine that the merge registration of the first RAT and the second RAT has been completed.

27. The method according to claim 26, wherein, Before the first core network device sends the first merged registration acceptance message to the terminal through the access network device corresponding to the second RAT, it also includes: The first core network device sends a registration message to the Unified Data Management (UDM), wherein the registration message is used to record at least one of the following in the UDM: the first core network device serves the terminal, and merges the registration associated first RAT and second RAT.

28. The method according to claim 26 or 27, wherein, The first merged registration request carries at least one of the following: the identifier of the terminal, the registration type, the type of the first RAT, the identifier of the access network device corresponding to the first RAT, the tracking area information corresponding to the first RAT, and the identifier of the cell corresponding to the access network device corresponding to the first RAT.

29. The method according to any one of claims 26-28, wherein, The first merged registration acceptance message carries at least one of the following: registration type, NAS identifier for paging corresponding to the second RAT, NAS identifier for paging corresponding to the first RAT, NAS identifiers for paging corresponding to the first RAT and the second RAT, registration area corresponding to the second RAT, registration area corresponding to the first RAT, registration areas corresponding to the first RAT and the second RAT, and the registration status of the terminal in the first RAT.

30. The method according to claim 19 or 22, further comprising: The first core network device receives a second merge registration request from the second core network device, wherein the second merge registration request is used to request the first core network device to establish an association relationship with the second core network device and to establish the terminal context for the terminal under the first RAT; The first core network device sends a second merge registration acceptance message to the second core network device, wherein the second merge registration acceptance message is used to indicate acceptance of merge registration.

31. The method according to claim 30, wherein, The second merged registration request carries at least one of the following: the NAS identifier for paging corresponding to the second RAT, the identification information of the second core network device, and the registration area corresponding to the second RAT, wherein the identification information of the second core network device is used by the first core network device to establish an association between the first core network device and the second core network device.

32. The method according to claim 30 or 31, wherein, The second merged registration acceptance message carries at least one of the following: the NAS identifier for paging corresponding to the first RAT, the identification information of the first core network device, and the registration area corresponding to the first RAT, wherein the identification information of the first core network device is used by the second core network device to establish an association between the first core network device and the second core network device.

33. A terminal, comprising: The first communication unit is configured to send a first request to the first core network device through the access network device corresponding to the first RAT after the terminal completes the merged registration of the first RAT and the second RAT by sending a first merged registration request to the core network through the access network device corresponding to the second RAT. The first request is used to request to establish a connection with the first core network device through the access network device corresponding to the first RAT.

34. A first core network device, comprising: The second communication unit is configured to receive a first request sent by the terminal through the access network device corresponding to the first RAT after the terminal sends a first merge registration request to the core network through the access network device corresponding to the second RAT to complete the merge registration of the first RAT and the second RAT. The first request is used to request to establish a connection with the first core network device through the access network device corresponding to the first RAT.

35. A terminal, comprising: A transceiver, a processor, and a memory for storing a computer program, the transceiver for communicating with other devices, and the processor for calling and running the computer program stored in the memory to cause the terminal to perform the method as described in any one of claims 1 to 14.

36. A first core network device, comprising: A transceiver, a processor, and a memory for storing computer programs, the transceiver for communicating with other devices, and the processor for calling and running the computer programs stored in the memory to cause the first core network device to perform the method as described in any one of claims 15 to 32.

37. A chip, comprising: A processor for retrieving and running a computer program from memory, causing a device on which the chip is mounted to perform the method as claimed in any one of claims 1 to 14 or 15 to 32.

38. A computer-readable storage medium for storing a computer program that, when run by a device, causes the device to perform the method as claimed in any one of claims 1 to 14 or 15 to 32.

39. A computer program product comprising computer program instructions that cause a computer to perform the method as claimed in any one of claims 1 to 14 or 15 to 32.

40. A computer program that causes a computer to perform the method as claimed in any one of claims 1 to 14 or 15 to 32.

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