Communication method and apparatus

Abstract

Provided are a communication method and apparatus for solving the problem that a terminal device cannot perform normal communication on other accesses by means of operations performed on common parameters through several accesses of the terminal device. The method includes the following. When the terminal device on a first access is switched from a first PLMN to a second PLMN, if the state of the terminal device on a second access is that the terminal device is registered with or has been registered with the first PLMN, the terminal device determines not to delete the first mobility management parameters for the first access. If the state of the terminal device on the second access is that the terminal device has not been registered with the first PLMN, the terminal device determines to delete the first mobility management parameters for the first access. The first access and the second access belong to different access types. The registration status for the second access is considered when the first mobility management parameters are deleted, and thus the impact on communication on the second access can be reduced.

Description

Technical Field

[0001] Cross - reference to Related Applications This application claims priority to Chinese Patent Application No. 202210479701.2, filed with the China National Intellectual Property Administration on May 5, 2022, under the title "COMMUNICATION METHOD AND APPARATUS", the entire content of which is incorporated herein by reference.

[0002] This application relates to the field of communication technologies, and in particular, to communication methods and apparatuses.

Background Art

[0003] With the development of communication, currently, terminal devices are supported to communicate with a core network via multiple types of accesses. For example, a terminal device can communicate with a core network via access to 3rd generation partnership project (3GPP) wireless access technology and access to non - 3GPP access technology.

[0004] When a terminal device registers with the same public land mobile network (PLMN) via multiple accesses, some parameters can be shared across multiple accesses of the terminal device during communication. For example, non - access stratum (NAS) integrity protection algorithms, NAS encryption algorithms, globally unique temporary UE identity (GUTI), etc. are shared across multiple accesses of the terminal device.

[0005] Since several parameters are shared across multiple accesses of the terminal device, if an operation such as deletion or modification is performed on these parameters via one access of the terminal device, the communication on other accesses will be affected. For example, when NAS security context information is deleted via one access of the terminal device, integrity protection and encryption may not be performed in the uplink signaling for another access, and downlink signaling may not be received normally due to the failure of the integrity check. In another example, when the GUTI for one access of the terminal device is deleted, some messages for other accesses may not be able to carry the GUTI information. As a result, the PLMN may be unable to identify the terminal device, and the terminal device may be unable to receive paging from the PLMN, etc.

[0006] Therefore, a method for avoiding the impact on other accesses of an operation performed on common parameters via several accesses of the terminal device is an urgent problem to be solved. Summary of the Invention

[0007] This application provides a communication method and apparatus to solve the problem that the terminal device cannot perform normal communication on other accesses due to an operation performed on common parameters via several accesses of the terminal device.

[0008] According to a first aspect, the present application provides a communication method. This method may be implemented by a terminal device or may be a chip, circuit, or other component configured to implement the functions of a terminal device. The terminal device is used as an example. The method includes the following. When a terminal device on a first access is switched from a first PLMN to a second PLMN, if the state of the terminal device on a second access is that the terminal device is registered with the first PLMN or has already been registered with the first PLMN, the terminal device determines not to delete the first mobility management parameters for the first access. If the state of the terminal device on the second access is that the terminal device has not been registered with the first PLMN, the terminal device determines to delete the first mobility management parameters for the first access. The first access and the second access belong to different access types.

[0009] Whether the first PLMN (i.e., the PLMN registered via the first access) is registered via the second access can be used to determine whether the terminal device needs to use the first mobility management parameters for communication on the second access. In this embodiment of the present application, when the terminal device on the second access has not been registered with the first PLMN, the terminal device deletes the first mobility management parameters for the first access. Thus, the information maintenance cost of the terminal device can be reduced without affecting the communication performed by the terminal device on the second access, and the terminal device can be further prevented from using invalid parameters (i.e., the first mobility management parameters) for communication on the first access, thereby improving the communication performance of the terminal device on the first access.

[0010] When the terminal device on the second access has registered with or is registered with the first PLMN, the first mobility management parameters are not deleted, thus ensuring that the terminal device can perform normal communication on the second access.

[0011] In a possible design, if the PLMN registered via the first access is the same as the PLMN registered via the second access, the first mobility management parameter is shared on the first access and the second access.

[0012] In a possible design, before the terminal device on the first access is switched from the first PLMN to the second PLMN, the method further includes the following. The terminal device determines that the first PLMN is registered via the first access.

[0013] In a possible design, after it is determined that the first mobility management parameter is not deleted, the method further includes the following. If the switch is performed from the first PLMN to the third PLMN via the second access, the terminal device determines to delete the first mobility management parameter.

[0014] After the terminal device on the second access is switched from the first PLMN to another PLMN, the terminal device does not use the first mobility management parameter for communication on the second access. Therefore, after the terminal device on the second access is switched from the first PLMN to another PLMN, the first mobility management parameter is deleted in a timely manner. Thus, the parameter maintenance cost of the terminal device can be reduced, and it can be further avoided that the terminal device uses invalid parameters (i.e., the first mobility management parameter) for communication on the first access and / or the second access.

[0015] In a possible design, the first mobility management parameter includes at least one of a key set identifier or a globally unique temporary user equipment identifier, and the key set identifier identifies NAS security context information.

[0016] In a possible design, the NAS security context information includes a security encryption algorithm, and the security encryption algorithm is a null encryption algorithm.

[0017] Since the security of the NAS security context information is low when the security encryption algorithm is a null encryption algorithm, in the above manner, the first mobility management parameter is deleted when the security encryption algorithm in the NAS security context information identified by the key set identifier is a null encryption algorithm, thereby facilitating the communication security of the terminal device.

[0018] According to a second aspect, the present application provides a communication method. The method can be implemented by a terminal device or can be a chip, a circuit, or another component configured to implement the functions of the terminal device. The terminal device is used as an example. The method includes the following. The terminal device acquires first information through a first access of the terminal device, and determines whether to delete a first mobility management parameter for the first access based on the first information and information about a second access of the terminal device. The first information indicates a reason why the core network device rejects the request of the terminal device and that the first access and the second access belong to different access types.

[0019] In this embodiment of the present application, when the first mobility management parameter for the first access is deleted, considering the information for the second access, the first mobility management parameter may not be deleted when the first mobility management parameter is required on the second access. Thus, the terminal device can perform communication on the second access by using the first mobility management parameter. This avoids the problem that normal communication may not be performed on the second access because the first mobility management parameter for the first access is deleted in an inappropriate scenario (for example, in a case where the first mobility management parameter is required on the second access), and reduces the impact on communication on the second access.

[0020] Furthermore, the terminal device can determine whether to delete the first mobility management parameter for the first access, and thus, flexibility in processing the first mobility management parameter can be provided, and the accuracy can also be improved.

[0021] In a possible design, when the PLMN registered via the first access is the same as the PLMN registered via the second access, the first mobility management parameter is shared on the first access and the second access.

[0022] In a possible design, the first information is not applicable to the second access. The terminal device determining whether to delete the first mobility management parameter based on the first information and the information of the terminal device for the second access includes the following. The terminal device determines whether to delete the first mobility management parameter based on the first information and the registration information for the second access.

[0023] Registration information for the second access can be used to determine whether the terminal device needs to use the first mobility management parameter for communication on the second access. In this way, the terminal device can avoid deleting the first mobility management parameter when the terminal device uses the first mobility management parameter for communication on the second access, thereby ensuring that normal communication can be carried out by the terminal device on the second access.

[0024] In a possible design, for the terminal device to determine whether to delete the first mobility management parameter based on the first information and the registration information for the second access, it includes the following. The terminal device determines to delete the first mobility management parameter when the registration information for the second access satisfies one of the following conditions: the PLMN is not registered via the second access, or the PLMN registered via the second access is different from the PLMN registered via the first access.

[0025] If the registration is not carried out via the second access on the PLMN registered via the first access, it can be determined that the terminal device does not need to use the first mobility management parameter for communication on the second access. In the above manner, the terminal device deletes the first mobility management parameter when the terminal device does not need to use the first mobility management parameter for communication on the second access. Therefore, the information maintenance cost of the terminal device can be reduced without affecting the communication carried out by the terminal device on the second access, and the terminal device can further avoid using invalid parameters (i.e., the first mobility management parameter) for communication on the first access, thereby improving the communication performance of the terminal device on the first access.

[0026] In a possible design, for the terminal device to determine whether to delete the first mobility management parameter based on the first information and the registration information about the second access, it includes the following. When the registration information about the second access satisfies the following condition, i.e., the PLMN registered via the second access is the same as the PLMN registered via the first access, the terminal device determines not to delete the first mobility management parameter.

[0027] When the PLMN registered via the first access is registered via the second access, it may be determined that the terminal device needs to use the first mobility management parameter for communication on the second access. In the above manner, when the terminal device needs to use the first mobility management parameter for communication on the second access, the terminal device does not delete the first mobility management parameter, and thus, it can be guaranteed that normal communication is carried out by the terminal device on the second access.

[0028] In a possible design, the first information is applicable to the second access. For the terminal device to determine whether to delete the first mobility management parameter based on the first information and the information about the second access of the terminal device, it includes the following. The terminal device determines whether to delete the first mobility management parameter based on the first information, the registration information about the second access, and the service information about the second access, and the service information about the second access is information about whether an emergency service is being carried out on the second access.

[0029] In the above design, the degradation of communication quality caused by the deletion of the first mobility management parameter when there is an emergency service on the second access can be reduced, and thus, it can be guaranteed that the emergency service usually carried out via the second access is carried out normally, and the user experience is improved.

[0030] In a possible design, an emergency service is a service corresponding to a protocol data unit (PDU) session that carries a first identifier, and the first identifier identifies that the service implemented on the PDU session is an emergency service.

[0031] In a possible design, for a terminal device to process first mobility management parameters based on first information, registration information about a second access, and service information about the second access, the following is included. The terminal device determines to delete the first mobility management parameters when the registration information about the second access and the service information about the second access satisfy one of the following conditions: the public land mobile network (PLMN) is not registered via the second access; the PLMN registered via the second access is different from the PLMN registered via the first access; or the PLMN registered via the second access is the same as the PLMN registered via the first access and no emergency service is being implemented on the second access.

[0032] In the above design, the information maintenance cost of the terminal device can be reduced without affecting the communication performed by the terminal device on the second access or the emergency service being implemented on the second access, and the terminal device is further prevented from using invalid parameters (i.e., the first mobility management parameters) for communication on the first access, thereby improving the communication performance of the terminal device on the first access.

[0033] In a possible design, for the terminal device to process the first mobility management parameter based on the first information, the registration information about the second access, and the service information about the second access, the following is included. When the registration information about the second access and the service information about the second access meet the following conditions, that is, the PLMN registered via the second access is the same as the PLMN registered via the first access, and the emergency service is being carried out on the second access, the terminal device determines not to delete the first mobility management parameter.

[0034] Based on the above description, it is guaranteed that the emergency service on the second access is carried out normally, thereby improving the user experience.

[0035] In a possible design, the terminal device determines to delete the first mobility management parameter after the emergency service ends. In the above design, the information maintenance cost of the terminal device can be reduced, and the terminal device is further prevented from using invalid parameters (i.e., the first mobility management parameter) for communication on the first access, thereby improving the communication performance of the terminal device on the first access.

[0036] In a possible design, when it is determined that the first mobility management parameter is to be deleted, the method further includes the following. The terminal device deletes the second mobility management parameter, and the second mobility management parameter includes at least one of the last visited tracking area identifier for the second access or the tracking area identifier list for the second access. In the above design, the information maintenance cost of the terminal device can be reduced.

[0037] In a possible design, when it is determined that the first mobility management parameter is to be deleted, the method further includes the following. The terminal device stops the service being carried out on the second access. In the above design, communication resources can be saved.

[0038] In a possible design, when it is determined that the first mobility management parameter is to be deleted, the method further includes the following. The terminal device starts a first timer for a second access, where the first timer is used to trigger the terminal device to release the N1 NAS signaling connection, or the terminal device releases the N1 NAS signaling connection. In the above design, the N1 NAS signaling connection resources can be saved.

[0039] In a possible design, when it is determined that the first mobility management parameter is to be deleted, the method further includes the following. If a mobility management procedure is being performed on a second access, the terminal device stops the mobility management procedure. In the above design, communication resources can be saved.

[0040] In a possible design, the first mobility management parameter includes at least one of a key set identifier or a globally unique temporary user equipment identifier, and the key set identifier identifies NAS security context information.

[0041] According to a third aspect, the present application provides a communication method. The method can be implemented by a core network device or can be a chip, circuit, or another component configured to implement the functions of a core network device. The core network device is used as an example. The method includes the following. The core network device transmits first information to the terminal device via a first access of the terminal device, where the first information indicates the reason why the core network device rejects the request of the terminal device. The core network device determines whether to delete a first mobility management parameter for the first access based on the first information and information about a second access of the terminal device, and the first access and the second access belong to different access types.

[0042] In this embodiment of the present application, when the first mobility management parameter for the first access is deleted, considering the information for the second access, the first mobility management parameter may not be deleted when the first mobility management parameter is required on the second access. Thus, the terminal device may use the first mobility management parameter for communication on the second access. This avoids the problem that normal communication may not be performed on the second access because the first mobility management parameter for the first access is deleted, and reduces the impact on communication on the second access.

[0043] In a possible design, when the PLMN registered via the first access is the same as the PLMN registered via the second access, the first mobility management parameter is shared on the first access and the second access.

[0044] In a possible design, the first information is not applicable to the second access. The core network device determining whether to delete the first mobility management parameter based on the first information and the information about the second access includes the following. The core network device determines whether to delete the first mobility management parameter based on the first information and the registration information about the second access.

[0045] The registration information about the second access can be used to determine whether the core network device needs to use the first mobility management parameter for communication on the second access. In this way, the terminal device is prevented from deleting the first mobility management parameter when the terminal device uses the first mobility management parameter for communication on the second access, thereby ensuring that normal communication can be performed by the terminal device on the second access.

[0046] In a possible design, for a core network device to determine whether to delete the first mobility management parameter based on the first information and the registration information about the second access includes the following. The core network device determines to delete the first mobility management parameter when the registration information about the second access satisfies one of the following conditions, i.e., the PLMN is not registered via the second access.

[0047] If the registration is not performed via the second access on the PLMN registered via the first access, it can be determined that the terminal device does not need to use the first mobility management parameter for communication on the second access. In the above manner, the first mobility management parameter is deleted when the terminal device does not need to use the first mobility management parameter for communication on the second access, and thus, the information maintenance cost of the core network device can be reduced without affecting the communication performed by the terminal device on the second access.

[0048] In a possible design, for a core network device to determine whether to delete the first mobility management parameter based on the first information and the registration information about the second access includes the following. The core network device determines not to delete the first mobility management parameter when the registration information about the second access satisfies the following condition, i.e., the PLMN registered via the second access is the same as the PLMN registered via the first access.

[0049] If the PLMN registered via the first access is registered via the second access, it may be determined that the terminal device needs to use the first mobility management parameter for communication on the second access. In the above manner, the terminal device does not delete the first mobility management parameter when it is necessary for the terminal device to use the first mobility management parameter for communication on the second access, and thus, normal communication can be guaranteed to be performed by the terminal device on the second access.

[0050] In a possible design, the first information is applicable to the second access. For the core network device to determine whether to delete the first mobility management parameter based on the first information and the information about the second access includes the following. The core network device determines whether to delete the first mobility management parameter based on the first information, the registration information about the second access, and the service information about the second access, and the service information about the second access is information about whether an emergency service is being performed on the second access.

[0051] In the above design, the impact on the service for the second access can be reduced, and the user experience can be improved.

[0052] In a possible design, for the core network device to process the first mobility management parameter based on the first information, the registration information about the second access, and the service information about the second access includes the following. The core network device determines to delete the first mobility management parameter when the registration information about the second access and the service information about the second access satisfy one of the following conditions, that is, the PLMN is not registered via the second access, or the PLMN registered via the second access is the same as the PLMN registered via the first access and the emergency service is not being performed on the second access.

[0053] In the above design, the information maintenance cost of the core network device can be reduced without affecting the communication performed by the terminal device on the second access or the emergency service being performed on the second access.

[0054] In a possible design, for the core network device to process the first mobility management parameter based on the first information, the registration information about the second access, and the service information about the second access, it includes the following. The core network device determines not to delete the first mobility management parameter when the registration information about the second access and the service information about the second access meet the following conditions, that is, the PLMN registered via the second access is the same as the PLMN registered via the first access, and the emergency service is being performed on the second access.

[0055] Based on the above description, it is guaranteed that the emergency service on the second access is normally performed, thereby improving the user experience.

[0056] In a possible design, the core network device determines to delete the first mobility management parameter after the emergency service ends. In the above design, the information maintenance cost of the core network device can be reduced.

[0057] In a possible design, when it is determined that the first mobility management parameter is to be deleted, the method further includes the following. The core network device deletes the second mobility management parameter, and the second mobility management parameter includes at least one of the last visited tracking area identifier for the second access or the tracking area identifier list for the second access. In the above design, the information maintenance cost of the core network device can be reduced.

[0058] In a possible design, if it is determined that the first mobility management parameter is to be deleted, the method further includes the following. The core network device stops the service being carried out on the second access. In the above design, communication resources can be saved.

[0059] In a possible design, if it is determined that the first mobility management parameter is to be deleted, the method further includes the following. The core network device releases the N1 NAS signaling connection. In the above design, N1 NAS signaling connection resources can be saved.

[0060] In a possible design, if it is determined that the first mobility management parameter is to be deleted, the method further includes the following. If a mobility management procedure is being carried out on the second access, the core network device stops the mobility management procedure. In the above design, communication resources can be saved.

[0061] In a possible design, the first mobility management parameter includes at least one of a key set identifier or a globally unique temporary user equipment identifier, and the key set identifier identifies NAS security context information.

[0062] According to a fourth aspect, the present application provides a communication method. The method can be implemented by a terminal device or can be a chip, circuit, or another component configured to implement the functions of the terminal device. The terminal device is used as an example. The method includes the following. The terminal device receives first indication information via a first access of the terminal device, where the first indication information indicates whether to delete a first mobility management parameter for the first access, and based on the first indication information, determines whether to delete the first mobility management parameter for the first access, where the first access and the second access belong to different access types.

[0063] In this embodiment of the present application, the network device indicates to the terminal device whether to delete the first mobility management parameter, and thus, the complexity of the terminal device can be reduced.

[0064] In a possible design, when the PLMN registered via the first access is the same as the PLMN registered via the second access, the first mobility management parameter is shared on the first access and the second access.

[0065] In a possible design, the terminal device determining whether to delete the first mobility management parameter based on the first indication information includes the following. The terminal device determines whether to delete the first mobility management parameter based on the first indication information and the information about the second access.

[0066] In the above manner, when the first mobility management parameter for the first access is deleted, considering the information about the second access, the first mobility management parameter may not be deleted when the first mobility management parameter is required on the second access. Thus, the terminal device can use the first mobility management parameter for communication on the second access. This avoids the problem that normal communication may not be performed on the second access because the first mobility management parameter for the first access is deleted, and reduces the impact on communication on the second access.

[0067] In a possible design, the terminal device determining whether to delete the first mobility management parameter based on the first indication information and the information about the second access includes the following. The terminal device determines whether to delete the first mobility management parameter based on the first indication information and the registration information about the second access.

[0068] Registration information for the second access can be used to determine whether the terminal device needs to use the first mobility management parameter for communication on the second access. In this way, the terminal device can avoid deleting the first mobility management parameter when the terminal device uses the first mobility management parameter for communication on the second access, thereby ensuring that normal communication can be carried out by the terminal device on the second access.

[0069] In a possible design, for the terminal device to determine whether to delete the first mobility management parameter based on the first indication information and the registration information for the second access, the following is included. When the first indication information indicates deleting the first mobility management parameter, the terminal device determines to delete the first mobility management parameter when the registration information for the second access satisfies one of the following conditions: the PLMN is not registered via the second access, or the PLMN registered via the second access is different from the PLMN registered via the first access.

[0070] If the registration is not performed via the second access on the PLMN registered via the first access, it can be determined that the terminal device does not need to use the first mobility management parameter for communication on the second access. In this way, the terminal device deletes the first mobility management parameter when the terminal device does not need to use the first mobility management parameter for communication on the second access. Thus, the information maintenance cost of the terminal device can be reduced without affecting the communication carried out by the terminal device on the second access, and it can be further avoided that the terminal device uses an invalid parameter (i.e., the first mobility management parameter) for communication on the first access, thereby improving the communication performance of the terminal device on the first access.

[0071] In a possible design, for the terminal device to determine whether to delete the first mobility management parameter based on the first indication information and the registration information about the second access, it includes the following. If the first indication information indicates deleting the first mobility management parameter and the PLMN registered via the second access is the same as the PLMN for which registration is not performed via the first access, the terminal device determines whether to delete the first mobility management parameter based on the service information about the second access, and the service information about the second access is information about whether an emergency service is being performed on the second access.

[0072] In the above design, the impact on the service for the second access can be reduced, and the user experience can be improved.

[0073] In a possible design, for the terminal device to determine whether to delete the first mobility management parameter based on the service information about the second access, it includes the following. If an emergency service is being performed on the second access, the terminal device determines not to delete the first mobility management parameter, or if an emergency service is not being performed on the second access, the terminal device determines to delete the first mobility management parameter.

[0074] In the above design, it is guaranteed that the emergency service normally performed on the second access is normally performed, thereby improving the user experience.

[0075] In a possible design, when it is determined that the first mobility management parameter is to be deleted, the method further includes the following. The terminal device determines to delete the first mobility management parameter after the emergency service ends. In the above design, the information maintenance cost of the terminal device can be reduced, and the terminal device is further prevented from using parameters (i.e., the first mobility management parameter) that are invalid for communication in the first access, thereby improving the communication performance of the terminal device on the first access.

[0076] In a possible design, when it is determined that the first mobility management parameter is to be deleted, the method further includes the following. The terminal device deletes the second mobility management parameter, and the second mobility management parameter includes at least one of the last visited tracking area identifier for the second access or the tracking area identifier list for the second access. In the above design, the information maintenance cost of the terminal device can be reduced.

[0077] In a possible design, when it is determined that the first mobility management parameter is to be deleted, the method further includes the following. The terminal device stops the service being performed on the second access. In the above design, communication resources can be saved.

[0078] In a possible design, when it is determined that the first mobility management parameter is to be deleted, the method further includes the following. The terminal device starts a first timer for the second access, where the first timer is used to trigger the terminal device to release the N1 NAS signaling connection, or the terminal device releases the N1 NAS signaling connection. In the above design, the N1 NAS signaling connection resources can be saved.

[0079] In a possible design, when it is determined that the first mobility management parameter is to be deleted, the method further includes the following. If a mobility management procedure is being performed on a second access, the terminal device stops the mobility management procedure. In the above design, communication resources can be saved.

[0080] In a possible design, the first mobility management parameter includes at least one of a key set identifier or a globally unique temporary user equipment identifier, and the key set identifier identifies NAS security context information.

[0081] According to a fifth aspect, the present application provides a communication method. The method can be implemented by a core network device or can be a chip, circuit, or other component configured to implement the functions of a core network device. A core network device is used as an example. The method includes the following. The core network device determines first indication information and transmits the first indication information to the terminal device via a first access of the terminal device. The first indication information indicates whether to delete a first mobility management parameter for the first access. The first access and the second access belong to different access types.

[0082] In this embodiment of the present application, the network device indicates to the terminal device whether to delete the first mobility management parameter, and thus the complexity of the terminal device can be reduced.

[0083] In a possible design, if the PLMN registered via the first access is the same as the PLMN registered via the second access, the first mobility management parameter is shared on the first access and the second access.

[0084] In a possible design, for the core network device to determine the first indication information includes the following. The core network device determines the first indication information based on the second indication information and the information about the second access, and the second indication information indicates the reason why the core network device rejects the request of the terminal device.

[0085] In this embodiment of the present application, when the first mobility management parameter for the first access is deleted, considering the information about the second access, the first mobility management parameter may not be deleted when the first mobility management parameter is required on the second access. Therefore, the terminal device can use the first mobility management parameter for communication on the second access. This avoids the problem that normal communication may not be performed on the second access because the first mobility management parameter for the first access is deleted, and reduces the impact on communication on the second access.

[0086] In a possible design, the second indication information is not applicable to the second access. For the core network device to determine the first indication information based on the second indication information and the information about the second access includes the following. The core network device determines the first indication information based on the second indication information and the registration information about the second access.

[0087] The registration information about the second access can be used to determine whether the core network device needs to use the first mobility management parameter for communication on the second access. In this way, the terminal device is prevented from deleting the first mobility management parameter when the terminal device uses the first mobility management parameter for communication on the second access, thereby ensuring that normal communication can be performed by the terminal device on the second access.

[0088] In a possible design, for the core network device to determine the first indication information based on the second indication information and the registration information about the second access includes the following. When the registration information about the second access satisfies one of the following conditions, i.e., the PLMN is not registered via the second access, as indicated by the first indication information, the core network device indicates to delete the first mobility management parameter. Alternatively, when the registration information about the second access satisfies the following conditions, i.e., the PLMN is already registered or is being registered via the second access, as indicated by the first indication information, the core network device indicates not to delete the first mobility management parameter.

[0089] If the registration is not performed via the second access on the PLMN registered via the first access, it may be determined that the terminal device does not need to use the first mobility management parameter for communication on the second access. In the above manner, the first mobility management parameter is deleted when the terminal device does not need to use the first mobility management parameter for communication on the second access, and thus, the information maintenance cost of the core network device can be reduced without affecting the communication performed by the terminal device on the second access.

[0090] If the PLMN registered via the first access is registered via the second access, it may be determined that the terminal device needs to use the first mobility management parameter for communication on the second access. In the above manner, the terminal device does not delete the first mobility management parameter when the terminal device needs to use the first mobility management parameter for communication on the second access, and thus, normal communication can be guaranteed to be performed by the terminal device on the second access.

[0091] In a possible design, the second indication information is applicable to the second access. For the core network device to determine the first indication information based on the second indication information and the information about the second access includes the following. The core network device determines the first indication information based on the second indication information, the registration information about the second access, and the service information about the second access, where the service information about the second access is information about whether an emergency service is being performed on the second access.

[0092] In the above design, the impact on the service for the second access can be reduced, and the user experience can be improved.

[0093] In a possible design, for the core network device to determine the first indication information based on the second indication information, the registration information about the second access, and the service information about the second access includes the following. The core network device indicates, by the first indication information, to delete the first mobility management parameter when the registration information about the second access and the service information about the second access satisfy one of the following conditions: the PLMN is not registered via the second access, or the PLMN is registered or registered via the second access and no emergency service is being performed on the second access.

[0094] In the above design, the information maintenance cost of the core network device can be reduced without affecting the communication performed by the terminal device on the second access or the emergency service being performed on the second access.

[0095] In a possible design, for the core network device to determine the first indication information based on the second indication information, the registration information for the second access, and the service information for the second access, the following is included. The core network device indicates, by the first indication information, that it does not delete the first mobility management parameter when the registration information for the second access and the service information for the second access meet the following conditions, that is, the PLMN is registered or registered via the second access, and the emergency service is not being carried out on the second access.

[0096] Based on the above description, it is guaranteed that the emergency service on the second access is carried out normally, thereby improving the user experience.

[0097] In a possible design, the first mobility management parameter includes at least one of a key set identifier or a globally unique temporary user equipment identifier, and the key set identifier identifies the NAS security context information.

[0098] According to the sixth aspect, the present application further provides a communication device, which has the function of implementing any method provided in the first aspect, the second aspect, or the fourth aspect. The communication device can be realized by hardware or by hardware that executes the corresponding software. The hardware or software includes one or more units or modules corresponding to the above functions.

[0099] In a possible design, the communication device includes a processor. The processor is configured to support the communication device in implementing the corresponding functions of the terminal device in the above method. The communication device may further include a memory. The memory may be coupled to the processor, and the memory stores program instructions and data necessary for the communication device. Optionally, the communication device further includes an interface circuit, and the interface circuit is configured to support communication between the communication device and another device.

[0100] In a possible design, the communication device includes corresponding function modules respectively configured to implement the steps in the above method. The functions may be realized by hardware or by hardware executing corresponding software. The hardware or software includes one or more modules corresponding to the above functions.

[0101] In a possible design, the structure of the communication device includes a processing module and a communication module. The modules may implement the corresponding functions in the above method examples. For details, refer to the description of the method provided in the first aspect, the second aspect, or the fourth aspect. Here, the details will not be described again.

[0102] According to a seventh aspect, the present application further provides a communication device, and the communication device has a function of implementing any method provided in the third aspect or the fifth aspect. The communication device may be realized by hardware or by hardware executing corresponding software. The hardware or software includes one or more units or modules corresponding to the above functions.

[0103] In a possible design, the communication device includes a processor. The processor is configured to support the communication device in performing the corresponding functions of the network device in the above method. The communication device may further include a memory. The memory may be coupled to the processor, and the memory stores program instructions and data necessary for the communication device. Optionally, the communication device further includes an interface circuit, and the interface circuit is configured to support communication between the communication device and another device.

[0104] In a possible design, the communication device includes corresponding functional modules respectively configured to perform the steps in the above method. This function may be realized by hardware or may be realized by hardware that executes the corresponding software. The hardware or software includes one or more modules corresponding to the above functions.

[0105] In a possible design, the structure of the communication device includes a processing module and a communication module. The module may perform the corresponding functions in the above method example. For details, refer to the description of the method provided in the third aspect or the fifth aspect. Here, the details will not be described again.

[0106] According to the eighth aspect, a communication device is provided, which includes a processor and an interface circuit. The interface circuit is configured to receive a signal from a communication device other than the communication device and transmit the signal to the processor, or transmit a signal from the processor to a communication device other than the communication device. The processor is configured to perform the method and possible design in any one of the first aspect, the second aspect, or the fourth aspect by using logic circuits or by executing code instructions.

[0107] According to a ninth aspect, a communication device is provided, including a processor and an interface circuit. The interface circuit is configured to receive a signal from a communication device other than the communication device and transmit the signal to the processor, or transmit a signal from the processor to a communication device other than the communication device. The processor is configured to implement the method and possible design in any one of the third aspect or the fifth aspect by using a logic circuit or by executing code instructions.

[0108] According to a tenth aspect, a computer-readable storage medium is provided. The computer-readable storage medium stores a computer program or instructions. When the computer program or instructions are executed by a processor, one of the methods and possible designs in any one of the first aspect to the fifth aspect is implemented.

[0109] According to an eleventh aspect, a computer program product storing instructions is provided. When the instructions are executed by a processor, one of the methods and possible designs in any one of the first aspect to the fifth aspect is implemented.

[0110] According to a twelfth aspect, a chip system is provided. The chip system includes a processor and further includes a memory, and can implement one of the methods and possible designs in any one of the first aspect to the fifth aspect. The chip system may include a chip or may include a chip and another separate device.

[0111] According to a thirteenth aspect, a communication system is provided. The system includes a device according to the first aspect (for example, a terminal device) and may further include a core network device.

[0112] According to a fourteenth aspect, a communication system is provided. The system includes a device according to the second aspect (for example, a terminal device) and a device according to the third aspect (for example, a core network device).

[0113] According to the 15th aspect, a communication system is provided. The system includes an apparatus according to the 4th aspect (e.g., a terminal device) and an apparatus according to the 5th aspect (e.g., a core network device).

Brief Description of the Drawings

[0114]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Modes for Carrying Out the Invention

[0115] To make the objectives, technical solutions, and advantages of the embodiments of the present application clearer, the following further describes the embodiments of the present application in more detail with reference to the accompanying drawings.

[0116] The following describes the architecture of the network system to which the method provided in the present application is applied.

[0117] Figure 1 is a diagram of a 5G network architecture based on a service-based architecture. The 5G network architecture shown in Figure 1 may include three parts: a terminal device, a data network (DN), and a carrier network. The following briefly describes the functions of some network elements.

[0118] The carrier network may include one or more of the following network elements: an authentication server function (AUSF) network element, a network exposure function (NEF) network element, a policy control function (PCF) network element, a unified data management (UDM) network element, a unified data repository (UDR), a network repository function (NRF) network element, an access and mobility management function (AMF) network element, a session management function (SMF) network element, an access network, and a user plane function (UPF) network element. In the carrier network, the part other than the radio access network part may be called the core network part. In a possible implementation, the carrier network may further include an Application Function (AF) network element. Alternatively, the AF network element may not belong to the carrier network and may belong to a third party.

[0119] A terminal device is a device with a wireless transceiver function, which can be deployed on land, including indoor or outdoor devices, handheld devices, or in-vehicle devices, or can be deployed on the water surface (e.g., on a ship), or in the air (e.g., on an airplane, a balloon, or a satellite). The terminal device can be a mobile phone, a tablet computer, a computer with a wireless transceiver function, a virtual reality (VR) terminal, an augmented reality (AR) terminal, a wireless terminal in industrial control, a wireless terminal in self-driving, a wireless terminal in remote medical, a wireless terminal in smart grid, a wireless terminal in transportation safety, a wireless terminal in smart city, a wireless terminal in smart home, a UE, etc.

[0120] The terminal device can establish a connection to the carrier network through an interface (e.g., N1) provided by the carrier network and use services such as data services and / or voice services provided by the carrier network. The terminal device can further access the DN through the carrier network and use carrier services deployed on the DN and / or services provided by a third party. The third party can be a service party other than the carrier network and the terminal device and can provide services such as data services and / or voice services for the terminal device. The specific form of expression of the third party can be specifically determined based on the actual application scenario and is not limited here.

[0121] The core network part includes a user plane function and a control plane function.

[0122] The user plane function includes a UPF network element. As an interface to the data network, the UPF network element completes functions such as the transfer of user plane data (e.g., data packets), quality of service (QoS) control, collection of session / flow level charging statistics, and bandwidth limitation.

[0123] The control plane function is mainly for user registration and authentication, mobility management, and delivery of data packet transfer policies and QoS control policies to the user plane function. The control plane function can be further classified and includes other network elements besides the UPF network element, such as the AMF network element and the SMF network element.

[0124] The AMF network element mainly implements functions such as registration procedures during user access and location management and access authentication / authorization during user movement. Furthermore, the AMF network element is further responsible for transferring user policies between the UE and the PCF.

[0125] The SMF network element is mainly configured to establish a corresponding session connection when the user starts a service, provide specific services to the user, and deliver data packet transfer policies and QoS policies to the UPF based on the NG4 interface between the SMF and the UPF.

[0126] The AUSF network element is mainly responsible for authenticating the user, determining the validity of the user equipment, and deciding whether to allow the user or the equipment to access the network.

[0127] The UDM network element is mainly responsible for functions such as storing subscription data for user equipment and user access authentication.

[0128] The UDR is mainly responsible for the functions of storing and accessing subscription data, policy data, application data, and other types of data.

[0129] The PCF network element is mainly responsible for delivering service-related policies to the AMF or SMF.

[0130] The NEF network element is mainly configured to support the exposure of capabilities and events.

[0131] The AF network element mainly transfers application-side requirements for the network side to the PCF, and thus the PCF generates corresponding policies. The AF can be a third-party functional entity or a carrier-deployed application service, such as an Internet Protocol (IP) Multimedia Subsystem (IMS) voice call service.

[0132] The NRF network element provides a network element discovery function and can be configured to provide network element information corresponding to the network element type based on the request of another network element. The NRF further provides network element management services, such as registration, update, and deregistration of network elements and subscriptions, and push of the status of network elements.

[0133] The DN is a network outside the carrier network. The carrier network can access multiple DNs, and multiple services can be deployed on the DNs to provide services such as data services and / or voice services to terminal devices. For example, the DN is the private network of a smart factory, and the sensors installed in the workshop of the smart factory can be terminal devices, and the control server of the sensors is deployed in the DN, and the control server can provide services to the sensors. The sensors can communicate with the control server to obtain the commands of the control server, and transmit the sensor data collected by the control server to the control server based on the commands. In another example, the DN is the internal office network of a company, and the mobile phones or computers of the company's employees can be terminal devices, and the mobile phones or computers of the employees can access information, data resources, etc. on the company's internal office network.

[0134] In Figure 1, Nausf, Nnef, Npcf, Nudm, Naf, Namf, Nsmf, N1, N2, N3, N4, and N6 are the sequence numbers of the interfaces. For the meanings of these interface sequence numbers, please refer to the meanings defined in the 3rd generation partnership project (3GPP) standard protocol. This is not limited here.

[0135] The access network is a sub-network of the carrier network and is an implementation system between the service nodes in the carrier network and the terminal devices. To access the carrier network, the terminal device first passes through the access network and can then be connected to the service nodes in the carrier network through the access network.

[0136] The access network may include a 3GPP access network and / or a non-3GPP access network. That is, the terminal device may access the core network by using a 3GPP access network (or 3GPP access technology) and / or a non-3GPP access network (or non-3GPP access technology). The non-3GPP access network is an access network other than 3GPP, such as a wireless local area network (WLAN), a wireless fidelity (Wi-Fi) network, worldwide interoperability for microwave access (WiMAX), and a fixed network. The non-3GPP access network may include a reliable non-3GPP access network, an unreliable non-3GPP access network, a wired network, etc. The unreliable non-3GPP access network may include, for example, an unreliable WLAN, an unreliable Wi-Fi network, and an unreliable WiMAX. The reliable non-3GPP access network may include, for example, a reliable WLAN, a reliable Wi-Fi network, and a reliable WiMAX, and the wired network may include, for example, a fixed network.

[0137] The access of the terminal device to the 3GPP access network may be called 3GPP access, and the access of the terminal device to the non-3GPP access network may be called non-3GPP access.

[0138] An access device in a 3GPP access network can be a device that provides a wireless communication function to a terminal device, and an access device in a 3GPP access network may also be referred to as an access network device. The access devices in a 3GPP access network include, but are not limited to, the next-generation Node B (gNodeB, gNB) of 5G, evolved Node B (eNB), radio network controller (RNC), Node B (NB), base station controller (BSC), base transceiver station (BTS), home base station (e.g., home evolved Node B or home Node B, HNB), baseband unit (BBU), transmission reception point (TRP), transmitting point (TP), mobile switching center, etc.

[0139] An access device in a non-trusted non-3GPP access network may be referred to as a non-3GPP interworking function (N3IWF) device or a next generation packet data gateway (ngPDG). The N3IWF network element is similar to the evolved packet data gateway (ePDG) in Long Term Evolution (LTE) and is used in 5G to establish an Internet Protocol Security (IPsec) tunnel with a terminal device when the terminal device accesses the core network through a non-3GPP access network. In the future definition of 5G, the name of the N3IWF may be changed. In this application, only an example where the non-3GPP network access gateway is an N3IWF device is used for explanation.

[0140] For example, the N3IWF device may include a router or the like.

[0141] An access device in a trusted non-3GPP access network may include a trusted non-3GPP access point (TNAP) and / or a trusted non-3GPP gateway function (TNGF). The TNAP is configured to communicate with the terminal device, and the TNGF is configured to communicate with the core network device. The TNAP may include, but is not limited to, a WLAN access point (AP), a fixed access network (FAN), a switch, a router, or the like.

[0142] In a possible example, it can be shown in Figure 2 that a terminal device accesses a core network through a 3GPP access network and a non-3GPP access network that cannot be trusted. For example, the interface between the UPF and the 3GPP access network element may be called the N3 interface, the interface between the UPF and the N3IWF device may be called the N3 interface, the interface between the 3GPP access network element and the AMF may be called the N2 interface, and the interface between the N3IWF device and the AMF may be called the N2 interface. Other interfaces are shown in Figure 2 and will not be described again here.

[0143] In another possible example, it can be shown in Figure 3 that a terminal device accesses a core network through a 3GPP access network and a trusted non-3GPP access network. For example, the interface between the UPF and the 3GPP access network element may be called the N3 interface, and the interface between the UPF and the TNGF network element may be called the N3 interface. The interface between the 3GPP access network element and the AMF may be called the N2 interface, the interface between the TNGF network element and the AMF may be called the N2 interface, and the interface between the TNGF network element and the TNAP may be called the Ta interface. Other interfaces are shown in Figure 3 and will not be described again here.

[0144] Figures 2 and 3 are merely diagrams of the architectures of non-trusted non-3GPP access networks and trusted non-3GPP access networks, and it should be understood that the type and quantity of access networks through which the terminal device accesses the core network are not limited. In a specific implementation, the terminal device may access the core network through two or more access networks. The access networks through which the terminal device accesses the core network are not limited, but may be one or more of the types of 3GPP access networks, non-trusted non-3GPP access networks, or trusted non-3GPP access networks, or may be another type of access network that emerges in future communication development. For the types of networks included in non-trusted non-3GPP access networks and trusted non-3GPP access networks, please refer to the above descriptions of non-trusted non-3GPP access networks and trusted non-3GPP access networks. Here, the details will not be described again.

[0145] The access of the terminal device in the 3GPP access network may be called 3GPP access, and the access of the terminal device in the non-3GPP access network may be called non-3GPP access.

[0146] 3GPP access and non-3GPP access are merely examples of names, and it should be understood that 3GPP access may also be described as a 3GPP access link, a 3GPP transmission channel, a 3GPP transmission path, a 3GPP transmission link, a 3GPP communication link, etc. It can be understood that the 3GPP access described in this application is used on the condition that the communication link is based on 3GPP access technology.

[0147] Non-3GPP access may also be described as a non-3GPP access link, non-3GPP transmission channel, non-3GPP transmission path, non-3GPP transmission link, etc. It can be understood that the non-3GPP access described in this application is used on the condition that the communication link is based on non-3GPP access technology.

[0148] It can be understood that in the following of this application, the first access may also be referred to as a first access link, first transmission channel, first transmission path, first transmission link, first communication link, etc.

[0149] In the following, the second access may also be referred to as a second access link, second transmission channel, second transmission path, second transmission link, second communication link, etc.

[0150] It can be understood that the above network elements or functions can be network elements in a hardware device, software functions executed on dedicated hardware, or virtual functions instantiated on a platform (e.g., a cloud platform). One or more services can be obtained through the division of the above network elements or functions. Furthermore, services that exist independently of network functions can occur. In this application, an instance of a function, an instance of a service included in a function, or an instance of a service that exists independently of network functions may sometimes be referred to as a service instance.

[0151] Furthermore, network element a may sometimes be abbreviated as a. For example, the AF network element may sometimes be abbreviated as AF, the NEF network element may sometimes be abbreviated as NEF, and the AMF network element may sometimes be abbreviated as AMF.

[0152] Figures 1 to 3 are merely examples of applicable network architectures, and it should be understood that the actually applied network architecture may include more or fewer network elements than the network elements in Figures 1 to 3. In the embodiments of the present application, the names of the network elements used above may be changed, but the functions of the network elements may remain the same in future communication systems.

[0153] The above describes the network architecture in the embodiments of the present application. The following explains and describes some terms in the embodiments of the present application to facilitate the understanding of those skilled in the art.

[0154] Mobility management parameter: Mobility management parameters may include parameters such as, but not limited to, a key set identifier (ngKSI or eKSI), a globally unique temporary UE identity (GUTI), or a tracking area identity (TAI) of the last visited tracking area.

[0155] Key set identifier: The key set identifier identifies NAS security context information. The NAS security context information may include information such as, but not limited to, an NAS integrity protection algorithm, an NAS encryption algorithm, a key of the AMF in the serving network (KAMF), and security capability information of a user equipment (UE).

[0156] The NAS integrity protection algorithm may also be called a 5G integrity protection algorithm, an integrity protection algorithm, etc., and is used to perform integrity verification on NAS messages.

[0157] The NAS encryption algorithm may also be called a 5G encryption algorithm, a security encryption algorithm, etc., and is used to encrypt NAS messages.

[0158] GUTI: A temporary identifier assigned by the core network to the UE.

[0159] In the embodiments of the present application, "at least one" means one or more, and "a plurality of" means two or more. "And / or" represents an association relationship between related objects, indicating that three relationships may exist. For example, A and / or B may represent the following cases: A exists alone, both A and B exist, B exists alone, where A and B may be singular or plural. The character " / " usually indicates an "or" relationship between related objects. "At least one of the following items (parts)" or a similar expression thereof indicates any combination of these items, including a single item (part) or any combination of multiple items (parts). For example, at least one item (part) of a, b, or c may indicate a, b, c, a and b, a and c, b and c, or a, b, and c, where a, b, and c may be singular or plural.

[0160] Unless otherwise specified, ordinal terms such as "first" and "second" described in the embodiments of the present application are used to distinguish between multiple objects and do not limit the size, content, sequence, time sequence, priority, importance, etc. of the multiple objects. For example, the first access and the second access are only used to distinguish between different accesses and do not indicate different priorities, importance, etc. of the two accesses.

[0161] The following describes the technical features in the embodiments of the present application.

[0162] As shown in FIG. 2 or FIG. 3, the terminal device can communicate with the core network via multiple accesses. For example, the terminal device can communicate with the core network via 3GPP access and non-3GPP access. When the terminal device on multiple accesses registers with the same PLMN, some parameters can be shared across multiple accesses of the terminal device during communication, that is, the terminal device and the core network device maintain a set of parameters. For example, to achieve password separation and replay protection, the NAS security context information and the GUTI are shared across multiple accesses of the terminal device.

[0163] Since some parameters are shared across multiple accesses of the terminal device, if an operation is performed on these parameters via one access of the terminal device, the communication on other accesses will be affected. For example, the terminal device receives a rejection message via access A, and the rejection message carries a cause value. The terminal device can delete the key set identifier and / or the GUTI for access A based on the cause value.

[0164] For example, the cause value carried in the rejection message is #3 or #6, and the cause value indicates an illegal UE. Currently, after receiving the cause value, the terminal device can update the 5GS state to 5U3 ROAMING NOT ALLOWED, delete one or more of the GUTI, the TAI of the last visited tracking area, the TAI list, and the key set identifier, and in the case of a PLMN, at least one of the following processes: the universal integrated circuit card (UICC) including the universal subscriber identity module (USIM) is invalidated or deleted, or the USIM is considered invalid for 5GS services until the timer T3245 expires.

[0165] In another example, the cause value carried in the rejection message is #7, and the cause value indicates that 5GS services are not allowed. Currently, after receiving the cause value, the terminal device may perform at least one of the following processes: updating the 5GS state to 5U3 roaming not allowed, deleting one or more of the GUTI, the TAI of the last visited tracking area, the TAI list, and the key set identifier, and in the case of a PLMN, invalidating or deleting the UICC including the USIM or considering the USIM invalid for 5GS services until timer T3245 expires.

[0166] In another example, the cause value carried in the rejection message is #11, and the cause value indicates that the PLMN is not allowed. Currently, after receiving the cause value, the terminal device may perform at least one of the following processes: updating the 5GS state to 5U3 roaming not allowed, and deleting one or more of the GUTI, the TAI of the last visited tracking area, the TAI list, and the key set identifier.

[0167] In another example, the cause value carried in the rejection message is #72, and the cause value indicates that non-3GPP access to the 5G Core Network (5GCN) is not allowed. Currently, after receiving the cause value, if the core network is accessed via non-3GPP access, the terminal device may perform at least one of the following processes: updating the 5GS state to 5U3 roaming not allowed, and deleting one or more of the GUTI, the TAI of the last visited tracking area, the TAI list, and the key set identifier.

[0168] In another example, the cause value carried in the rejection message is #12, and the cause value indicates that the tracking area is not allowed. Currently, after receiving the cause value, the terminal device may perform at least one of the following processes: updating the 5GS state to 5U3 roaming not allowed, deleting one or more of the GUTI, the TAI of the last visited tracking area, the TAI list, and the key set identifier, and resetting the registration attempt counter.

[0169] In another example, the cause value carried in the rejection message is #78, and the cause value indicates that the PLMN is not allowed to operate at the present UE location. Currently, after receiving the cause value, the terminal device may perform at least one of the following processes: updating the 5GS state to 5U3 roaming not allowed, deleting one or more of the GUTI, the TAI of the last visited tracking area, the TAI list, and the key set identifier.

[0170] Since the terminal device maintains a set of NAS security context information and GUTI for access A and access B, when the key set identifier for access A is deleted, the NAS security context information for access A and access B is deleted. Therefore, integrity protection and encryption may not be performed on the uplink signaling on access B, and the downlink signaling may not be received normally due to a failure in the integrity check. When the GUTI on access A is deleted, some messages on access B may not be able to carry GUTI information. Therefore, the PLMN may not be able to identify the terminal device, and the terminal device may not be able to receive paging from the PLMN.

[0171] Based on this, embodiments of the present application provide a communication method and apparatus to solve the problem that a terminal device cannot perform normal communication on other accesses due to operations performed on common parameters through some accesses of the terminal device. The present method and apparatus are based on the same concept. The present method and apparatus have the same principle of problem-solving. Therefore, for the implementation of the present apparatus and method, reference may be made to each other. The repeated content will not be described again.

[0172] The communication method provided in the present application can be applied to various communication systems, such as the internet of things (IoT), narrowband internet of things (NB-IoT), long term evolution (LTE), fifth generation (5G) communication system, hybrid architecture of LTE and 5G, 5G new radio (NR) system, and 6G system or new communication system that appears in the future development of communication. The communication system in the present application can alternatively be a machine-to-machine (M2M) network, non-terrestrial network (NTN) network or another network.

[0173] The network architecture and service scenario described in the embodiments of the present application are for more clearly explaining the technical solutions in the embodiments of the present application, and do not constitute a limitation on the technical solutions provided in the embodiments of the present application. Those skilled in the art can know the following. With the development of network architecture and the emergence of new service scenarios, the technical solutions provided in the embodiments of the present application are also applicable to similar technical problems.

[0174] In the embodiments of the present application, "in the case of ~" can be alternatively described as "in the example of ~", "assuming ~", "when ~", etc. For example, "in the case where the state of the terminal device on the second access is that the terminal device is registered with or has been registered with the first PLMN" can be alternatively described as "assuming that the state of the terminal device on the second access is that the terminal device is registered with or has been registered with the first PLMN", "in the example where the state of the terminal device on the second access is that the terminal device is registered with or has been registered with the first PLMN", "when the state of the terminal device on the second access is that the terminal device is registered with or has been registered with the first PLMN", etc.

[0175] In the embodiments of the present application, "switching from... to..." can be alternatively described as "handover from... (or from)... to...", "reselection from... (or from)... to...", "selection from... (or from)... to...", "change from... (or from)... to...", "conversion from... (or from)... to...", "move from... (or from)... to...".

[0176] For example, the following "the terminal device on the first access is switched from the first PLMN to the second PLMN" can be described as "the terminal device on the first access is handed over from the first PLMN (or from) to the second PLMN", "the terminal device on the first access is reselected from the first PLMN (or from) to the second PLMN", "the terminal device on the first access is selected from the first PLMN (or from) to the second PLMN", "the terminal device on the first access is changed from the first PLMN (or from) to the second PLMN", "the terminal device on the first access is converted from the first PLMN (or from) to the second PLMN", "the terminal device on the first access is moved from the first PLMN (or from) to the second PLMN", etc.

[0177] For ease of explanation, the following uses an example where a terminal device accesses a core network via a first access and a second access. The first access and the second access may belong to different access types, or it may be described that the first access and the second access use different access technologies. For example, the first access is a 3GPP access, and the second access is a trusted non-3GPP access or an untrusted non-3GPP access. Alternatively, the first access is a trusted non-3GPP access or an untrusted non-3GPP access, and the second access is a 3GPP access.

[0178] In another example, the first access is a trusted non-3GPP access, and the second access is an untrusted non-3GPP access. Alternatively, the first access is an untrusted non-3GPP access, and the second access is a trusted non-3GPP access.

[0179] It should be understood that in the embodiments of the present application, the case where the terminal device has only two types of access is not limited. In a specific implementation, the terminal device may further access the core network via a first access, a second access, and other accesses (such as a third access and a fourth access). All of the other access, the first access, and the second access belong to different access types, that is, they correspond to (or apply) different access technologies.

[0180] In the embodiments of the present application, the terminal device may communicate with a core network device via an access device of an access network. For example, in a 3GPP access network, the terminal device may communicate with a core network device via an access network device. In another example, in a non-3GPP access network, the terminal device may communicate with a core network device via an N3IWF device.

[0181] The technical solutions of the embodiments of the present application will be described below with reference to the accompanying drawings in the embodiments of the present application.

[0182] The embodiments of the present application can be applied to a scenario where the first mobility management parameter for the first access of the terminal device needs to be deleted. When the PLMN registered via the first access is the same as the PLMN registered via the second access, the first mobility management parameter is shared on the first access and the second access.

[0183] For example, the first mobility management parameter may include at least one of a key set identifier or a GUTI. The first mobility management parameter may further include other parameters shared on the first access and the second access, and they are not enumerated one by one here.

[0184] The following describes three cases where the first mobility management parameter for the first access needs to be deleted. It should be understood that the present application is not limited to the following three cases where the first mobility management parameter for the first access needs to be deleted. On the condition that the first mobility management parameter for the first access needs to be deleted in a specific case, the first mobility management parameter for the first access can be regarded as needing to be deleted in the embodiments of the present application. The way the terminal device processes the first mobility management parameter for the first access in another scenario is the same as the way the terminal device processes the first mobility management parameter for the first access in the following three cases of the present application.

[0185] Case 1: The terminal device on the first access is switched from the first PLMN to the second PLMN.

[0186] The second PLMN is other than the registered PLMN (RPLMN) registered via the first access and the equivalent PLMN (EPLMN) via the first access.

[0187] Scenario 2: The terminal device obtains first information via the first access, and the first information indicates why the core network device rejects the request of the terminal device. In this example, the terminal device may determine, based on the first information, that the first mobility management parameters for the first access need to be deleted.

[0188] In a possible implementation, the terminal device may receive a registration rejection message via the first access, and the registration rejection message may carry a reason value. Alternatively, the terminal device may receive a service rejection message via the first access, and the service rejection message carries a reason value. Alternatively, the terminal device may receive a deregistration request message via the first access, and the deregistration request message carries a reason value. In this example, the reason value may be understood as the above first information.

[0189] For example, if the reason value received by the terminal device on the first access is #3 or #6, #7, #11, #72, #12, or #78, the terminal device may determine that the first mobility management parameters for the first access need to be deleted.

[0190] Here, only seven reason values are shown as an example, and it should be understood that the case determined based only on the seven reason values for which the first mobility management parameters for the first access are deleted is not limited.

[0191] Scenario 3: As an alternative, the scenario where the first mobility management parameter for the first access needs to be deleted could be as follows. The terminal device receives a first message via the first access. In this example, after receiving the first message, the terminal device could determine that the first mobility management parameter for the first access needs to be deleted. The first message does not carry the first information.

[0192] In this example, the first message could be a rejection message or another message received by the terminal device on the first access.

[0193] An example where the first message is a rejection message is used. After the terminal device receives the rejection message via the first access, if the NAS integrity check of the rejection message is successful, it could be determined that the first mobility management parameter for the first access needs to be deleted.

[0194] The following describes the communication method provided in the embodiments of the present application with respect to the above three scenarios.

[0195] Regarding Scenario 1 above, FIG. 4 is a schematic flowchart of a communication method according to an embodiment of the present application.

[0196] S401: The terminal device determines that the terminal device on the first access is to be switched from the first PLMN to the second PLMN.

[0197] After S401, S402 or S403 may be implemented.

[0198] Optionally, before S401, the first PLMN is registered via the first access.

[0199] The following describes the implementation of S401 for 3GPP access and non-3GPP access.

[0200] When the first access is a 3GPP access, the terminal device may determine, in the following manner, that the terminal device on the first access is to be switched from the first PLMN to the second PLMN. The terminal device on the first access is switched from the first cell to the second cell, and the PLMN corresponding to the first cell is the first PLMN. The terminal device receives, via the first access, the system information broadcast by the second cell, and the system information may carry the PLMN information of the second cell. The terminal device may determine, based on the PLMN information carried in the system information and the PLMN information stored locally for the first access, that the terminal device on the first access is to be switched from the first PLMN to the second PLMN.

[0201] When the first access is a non-3GPP access, the terminal device may determine, in the following manner, that the terminal device on the first access is to be switched from the first PLMN to the second PLMN. The terminal device determines that the connection to the first access device is interrupted, and the PLMN corresponding to the first access device is the first PLMN. The terminal device transmits a request message to the second access device, and the request message is for requesting to establish a communication connection to the second access device, and the PLMN corresponding to the second access device is the second PLMN. The terminal device receives the response message of the second access device, and the response message indicates to the terminal device that it can access the second access device. The terminal device determines, based on the PLMN corresponding to the second access device, that the terminal device on the first access is to be switched from the first PLMN to the second PLMN.

[0202] Regarding the first access device and the second access device, please refer to the relevant description of the access device of the non-3GPP access network in the above description of the network architecture.

[0203] S402: If the state for the second access is that the terminal device is registering with or has already registered with the first PLMN, the terminal device decides not to delete the first mobility management parameters for the first access.

[0204] Optionally, after S402, if deregistration is performed on the first PLMN via the second access (or deregistration or detachment is performed on the first PLMN), the terminal device may decide to delete the first mobility management parameters for the first access.

[0205] For example, an implementation scenario where deregistration of the first PLMN is performed via the second access is that the handover is performed from the first PLMN to the third PLMN on the second access. The third PLMN is different from the first PLMN, and the third PLMN may or may not be the same as the second PLMN.

[0206] S403: If the state for the second access is that the terminal device has not registered with the first PLMN, the terminal device decides to delete the first mobility management parameters for the first access.

[0207] In a possible implementation, assuming that the first mobility management parameters include a key set identifier, the NAS security context information identified by the key set identifier includes a security encryption algorithm, and the security encryption algorithm may be a null encryption algorithm, such as the 5G-EA0 algorithm or another algorithm that appears with the development of future communications.

[0208] Therefore, before deciding to delete the first mobility management parameters for the first access, the terminal device may decide that the security encryption algorithm is a null encryption algorithm.

[0209] When the security encryption algorithm is the null encryption algorithm, the NAS air interface message is not encrypted, so the security of the NAS air interface message is reduced. In the above method, the first mobility management parameter is deleted when the security encryption algorithm in the NAS security context information identified by the key set identifier is the null encryption algorithm, thereby facilitating the communication security of the terminal device.

[0210] Optionally, after determining not to delete the first mobility management parameter, the terminal device (or core network device) may perform the corresponding action. For example, the first mobility management parameter is not deleted, or the first mobility management parameter is reserved, or the first mobility management parameter is not processed.

[0211] Optionally, after determining to delete the first mobility management parameter, the terminal device (or core network device) may perform the corresponding action. For example, the first mobility management parameter is deleted.

[0212] The key set identifier in the first mobility management parameter is used as an example. Deleting the key set identifier can be achieved by at least one of the following methods, namely, setting the value of the key set identifier to "no available key" (ngKSI as its value), and determining that one or more of the keys KAMF, K'AMF, NAS encryption key, and NAS integrity key are invalid, can be realized by at least one of them.

[0213] "One or more of the keys KAMF, K'AMF, NAS encryption key, and NAS integrity key are invalid" can also be explained as the NAS security context information related to the key set identifier being invalid or no longer valid.

[0214] The GUTI in the first mobility management parameter is used as an example. Deleting the GUTI can be achieved by setting it to be invalid.

[0215] Whether the first PLMN (i.e., the PLMN registered via the first access) is registered via the second access can be used to determine whether the terminal device needs to use the first mobility management parameter for communication on the second access. In this embodiment of the present application, when the terminal device on the second access is not registered with the first PLMN, the terminal device deletes the first mobility management parameter for the first access. Thus, the information maintenance cost of the terminal device can be reduced without affecting the communication performed by the terminal device on the second access, and it can be further avoided that the terminal device uses invalid parameters (i.e., the first mobility management parameter) for communication on the first access, thereby improving the communication performance of the terminal device on the first access.

[0216] When the terminal device on the second access is already registered with the first PLMN or is registering with the first PLMN, the first mobility management parameter is not deleted, so that it can be guaranteed that the terminal device performs normal communication on the second access.

[0217] Regarding the above Case 2, FIG. 5 is a schematic flowchart of a communication method according to an embodiment of the present application.

[0218] S501: The core network device transmits the first information to the terminal device via the first access. Correspondingly, the terminal device acquires the first information via the first access.

[0219] The first information can be carried in a message such as a registration rejection message, a service rejection message, or a deregistration message. Only some examples are provided here for the sake of explanation, but it should be understood that the specific messages carrying the first information are not limited.

[0220] Regarding the first information, please refer to the relevant explanation in Case 2 above. Details will not be explained again here.

[0221] For example, the core network device can be a core network device accessed by the first access.

[0222] S502: The terminal device determines whether to delete the first mobility management parameter for the first access based on the first information and the information about the second access.

[0223] For example, the information about the second access can include at least one of the registration information for the second access or the service information for the second access, or the information about the second access can further include other information. This is not particularly limited here.

[0224] The registration information can represent the PLMN registration status for the second access, and the service information for the second access is information about whether an emergency service is being carried out on the second access.

[0225] In a possible implementation, the terminal device can determine that the first mobility management parameter for the first access needs to be deleted based on the first information. The terminal device determines whether to delete the first mobility management parameter for the first access based on the information about the second access. For the implementation where the terminal device determines that the first mobility management parameter for the first access needs to be deleted based on the first information, please refer to the relevant explanation in Case 2 above.

[0226] In an exemplary description, the first information is applicable to the first access but not applicable to the second access. Alternatively, the first information is applicable to both the first access and the second access. The following explains whether the first information is applicable to both the first access and the second access with respect to specific reason values.

[0227] For example, when the first information is the above reason value #3 or reason value #6, the reason value indicates an illegal terminal, that is, the terminal device is not permitted. Therefore, neither the first access nor the second access of the terminal device is permitted, that is, the first information is applicable to both the first access and the second access.

[0228] In another example, when the first information is the above reason value #7, the reason value indicates that the 5GS service is not permitted, that is, the 5GS service of the terminal device is not permitted. Therefore, neither the first access nor the second access of the terminal device is permitted, that is, the first information is applicable to both the first access and the second access.

[0229] In another example, when the first information is the above reason value #11, the reason value indicates that the PLMN is not permitted, that is, the first access is not permitted on the PLMN. The PLMN registered via (or being registered) the second access is the same as the PLMN registered via the first access, and the first information is also applicable to the second access. The PLMN registered via (or being registered) the second access is different from the PLMN registered via the first access, and the first information is not applicable to the second access.

[0230] In another example, when the first information is the above reason value #72, the reason value indicates that non-3GPP access is not permitted for the 5GCN.

[0231] It can be understood that the terminal device receives the cause value #72 via the first access. It can be known that the first access is a non-3GPP access and the first information is applicable to the first access. When the second access is a 3GPP access, the first information is not applicable to the second access.

[0232] In another example, when the first information is the above-mentioned cause value #12, the cause value indicates that the tracking area is not permitted, and the cause value is applicable to 3GPP access.

[0233] It can be understood that the terminal device receives the cause value #12 via the first access. The first information is applicable to the first access, that is, it can be known that the first access is a 3GPP access. When the second access is a non-3GPP access, the first information is not applicable to the second access.

[0234] In another example, when the first information is the above-mentioned cause value #78, the cause value indicates that the PLMN is not permitted to operate in the current location of the terminal device. The cause value is applicable to 3GPP access.

[0235] It can be understood that the terminal device receives the cause value #78 via the first access. The first information is applicable to the first access, that is, it can be known that the first access is a 3GPP access. Therefore, when the second access is a non-3GPP access, the first information is not applicable to the second access.

[0236] Referring to the scenario where the first information is applicable to the first access but not applicable to the second access, the implementation of how the terminal device determines whether to delete the first mobility management parameter for the first access based on the information about the second access will be described below.

[0237] It is assumed that the first information is not applicable to the second access. In one implementation, the terminal device may determine whether to delete the first mobility management parameter for the first access based on the registration information for the second access.

[0238] Optionally, the terminal device may determine to delete the first mobility management parameter for the first access when the registration information for the second access satisfies one of the following conditions: namely, the PLMN is not registered via the second access, or the PLMN registered via the second access is different from the PLMN registered via the first access.

[0239] The terminal device may determine not to delete the first mobility management parameter for the first access when the registration information for the second access satisfies the condition that the PLMN registered via the second access is the same as the PLMN registered via the first access.

[0240] The fact that the PLMN registered via the second access is different from the PLMN registered via the first access may be understood as meaning that the PLMN registered via the second access is different from the PLMN currently registered via the first access, the PLMN registered via the second access is not the PLMN via the first access, and the second PLMN is not the EPLMN via the first access. Correspondingly, the fact that the PLMN registered via the second access is the same as the PLMN registered via the first access may be understood as meaning that the PLMN registered via the second access is the same as the PLMN currently registered via the first access, or the PLMN registered via the second access is the PLMN via the first access, or the second PLMN is the EPLMN via the first access.

[0241] The understanding of the PLMN registered via the second access and the PLMN registered via the first access is different below. It should be understood that the understanding of the PLMN registered via the second access and the PLMN registered via the first access is the same as that described here. Details will not be explained one by one again below.

[0242] Assume that the first information is applicable to the second access. In one implementation, the terminal device may determine whether to delete the first mobility management parameter for the first access based on the registration information for the second access and the service information for the second access.

[0243] Optionally, the terminal device may determine to delete the first mobility management parameter for the first access when the registration information for the second access satisfies one of the following conditions: that is, the PLMN is not registered via the second access, or the PLMN registered via the second access is different from the PLMN registered via the first access.

[0244] The terminal device may determine to delete the first mobility management parameter for the first access when the registration information for the second access and the service information for the second access satisfy one of the following conditions: that is, the PLMN registered via the second access is the same as the PLMN registered via the first access and the emergency service is not being carried out on the second access.

[0245] The terminal device may determine not to delete the first mobility management parameter for the first access when the registration information for the second access and the service information for the second access satisfy the following condition: that is, the PLMN registered via the second access is the same as the PLMN registered via the first access and the emergency service is being carried out on the second access.

[0246] In an optional solution, after the emergency service on the second access ends, the terminal device may determine whether to delete the first mobility management parameters for the first access.

[0247] The following describes an implementation in which the terminal device determines whether to delete the first mobility management parameters for the first access based on information about the second access.

[0248] Optionally, for the actions performed after the core network device sends the first information, the core network device may alternatively determine whether to delete the first mobility management parameters for the first access based on the first information and the information about the second access.

[0249] The implementation in which the core network device determines whether to delete the first mobility management parameters for the first access based on the first information and the information about the second access is similar to the implementation in which the terminal device determines whether to delete the first mobility management parameters for the first access based on the first information and the information about the second access. The differences are as follows. The terminal device may determine to delete the first mobility management parameters for the first access when the registration information about the second access satisfies one of the following conditions: the PLMN is not registered via the second access, or the PLMN registered via the second access is different from the PLMN registered via the first access. The core network device may determine to delete the first mobility management parameters for the first access when the registration information about the second access satisfies one of the following conditions: the PLMN is not registered via the second access. For details, refer to the implementation in which the terminal device determines whether to delete the first mobility management parameters for the first access based on the first information and the information about the second access.

[0250] Optionally, the terminal device and / or the core network device may further implement one or more of the following four solutions.

[0251] Solution 1: When it is determined that the first mobility management parameter is to be deleted on the first access, the second mobility management parameter and / or the third mobility management parameter may be deleted. The second mobility management parameter includes at least one of the last visited tracking area TAI for the second access or the TAI list for the second access. The third mobility management parameter includes at least one of the last visited tracking area TAI for the first access or the TAI list for the first access.

[0252] For example, the "last visited tracking area TAI for the second access" may also be described as the last visited tracking area TAI corresponding to the second access, the last visited tracking area TAI of the terminal device in the access network corresponding to the second access, etc. The "last visited tracking area TAI for the first access" may also be described as the last visited tracking area TAI corresponding to the first access, the last visited tracking area TAI of the terminal device in the access network corresponding to the first access, etc.

[0253] It should be understood that the second mobility management parameter and the third mobility management parameter may alternatively include other parameters. This is not particularly limited here.

[0254] Solution 2: When it is determined that the first mobility management parameter is to be deleted, the service being implemented on the second access may be stopped.

[0255] Note that "stop" in this embodiment of the present application may also be described as "end", "cancel", "interrupt", "intervene", etc.

[0256] Solution 3: If it is determined to delete the first mobility management parameter, the terminal device may start a first timer for the second access or release the N1 NAS signaling connection for the second access. The core network device may release the N1 NAS signaling connection for the second access.

[0257] The first timer is used to trigger the terminal device to release the N1 NAS signaling connection for the second access. In an exemplary description, the first timer is used to enable the core network device to release the N1 NAS signaling connection for the second access.

[0258] In an optional solution, the terminal device may release the N1 NAS signaling connection for the second access when the first timer expires.

[0259] Optionally, if the core network device releases the N1 NAS signaling connection for the second access before the first timer expires, the terminal device may stop the first timer.

[0260] Solution 4: If it is determined that the first mobility management parameter is deleted and the mobility management procedure is being performed on the second access, the mobility management procedure may be stopped.

[0261] For example, the mobility management procedure may include one or more of procedures such as common procedures (5GMM common procedures), specific procedures (5GMM specific procedures), connection management procedures (5GMM connection management procedures).

[0262] The common procedures may include, but are not limited to, identification authentication procedures, authentication procedures, security mode control procedures, UE configuration update procedures, uplink transmission procedures, downlink transmission procedures, slice authentication procedures, etc.

[0263] Specific procedures may include, but are not limited to, registration procedures, deregistration procedures, etc.

[0264] The connection management procedures may include, but are not limited to, service request procedures, paging procedures, etc.

[0265] It should be understood that the mobility management procedures may further include other procedures, and those will not be enumerated one by one here again.

[0266] It should be noted that in the above four optional solutions, the terminal device may decide to delete the first mobility management parameter based on the information about the second access, or may decide to delete the first mobility management parameter after the emergency service on the second access ends.

[0267] Optionally, after deciding not to delete the first mobility management parameter, the terminal device (or core network device) may perform corresponding actions. For example, the first mobility management parameter is not deleted, or the first mobility management parameter is reserved, or the first mobility management parameter is not processed.

[0268] Optionally, after deciding to delete the first mobility management parameter, the terminal device (or core network device) may perform corresponding actions. For example, the first mobility management parameter is deleted.

[0269] For the implementation of deleting the first mobility management parameter, refer to the relevant description of the method in Figure 4.

[0270] In this embodiment of the present application, when the first mobility management parameter for the first access is deleted, considering the information about the second access, the first mobility management parameter may not be deleted when it is required on the second access. Therefore, the terminal device can use the first mobility management parameter for communication on the second access. This avoids the problem that normal communication may not be carried out on the second access because the first mobility management parameter for the first access is deleted, and reduces the impact on communication on the second access.

[0271] Furthermore, the terminal device determines whether to delete the first mobility management parameter, so the flexibility is higher and the accuracy is better.

[0272] Regarding the above Case 3, FIG. 6 is a schematic flowchart of a communication method according to an embodiment of the present application.

[0273] S601: The core network device transmits a first message to the terminal device via the first access. Correspondingly, the terminal device receives the first message via the first access.

[0274] For the first message, refer to the relevant description in Case 3 above. Here, the details will not be described again.

[0275] S602: The terminal device determines whether to delete the first mobility management parameter for the first access based on the first message and the information about the second access.

[0276] In a possible implementation, the terminal device may determine that the first mobility management parameter for the first access needs to be deleted based on the first message. The terminal device determines whether to delete the first mobility management parameter for the first access based on the information about the second access.

[0277] For an implementation where the terminal device determines that the first mobility management parameter for the first access needs to be deleted based on the first message, refer to the related description in Case 3 above.

[0278] For an implementation where the terminal device determines whether to delete the first mobility management parameter for the first access based on the information about the second access, refer to the implementation in the method of FIG. 5 where the terminal device determines whether to delete the first mobility management parameter for the first access based on the information about the second access. Here, the details will not be described again.

[0279] Optionally, for the actions performed after the core network device sends the first information, the core network device may alternatively determine whether to delete the first mobility management parameter for the first access based on the first information and the information about the second access.

[0280] For an implementation where the core network device determines whether to delete the first mobility management parameter for the first access based on the first information and the information about the second access, refer to the implementation in the method of FIG. 5 where the core network device determines whether to delete the first mobility management parameter for the first access based on the first information and the information about the second access. Here, the details will not be described again.

[0281] Optionally, the terminal device and / or the core network device may further perform one or more of the following four solutions: deleting the second mobility management parameter and / or the third mobility management parameter, stopping the service being performed on the second access, starting the first timer for the second access, or releasing the N1 NAS signaling connection, or stopping the mobility management procedure being performed on the second access.

[0282] For the implementation of deleting the second mobility management parameter and / or the third mobility management parameter, stopping the service being performed via the second access, starting the first timer for the second access, or releasing the N1 NAS signaling connection, and stopping the mobility management procedure being performed on the second access, please refer to the relevant description of the method in FIG. 5.

[0283] Optionally, after determining not to delete the first mobility management parameter, the terminal device (or the core network device) may perform the corresponding action. For example, the first mobility management parameter is not deleted, or the first mobility management parameter is reserved, or the first mobility management parameter is not processed.

[0284] Optionally, after determining to delete the first mobility management parameter, the terminal device (or the core network device) may perform the corresponding action. For example, the first mobility management parameter is deleted.

[0285] For the implementation of deleting the first mobility management parameter, please refer to the relevant description of the method in FIG. 4.

[0286] In this embodiment of the present application, when the first mobility management parameter for the first access is deleted, considering the information about the second access, the first mobility management parameter may not be deleted when the first mobility management parameter is required on the second access. Therefore, the terminal device can use the first mobility management parameter for communication on the second access. This avoids the problem that normal communication may not be performed on the second access because the first mobility management parameter for the first access is deleted, and reduces the impact on communication on the second access.

[0287] Furthermore, the terminal device determines whether to delete the first mobility management parameter, so the flexibility is higher and the accuracy is better.

[0288] The above describes a method for the terminal device to determine whether to delete the first mobility management parameter. Regarding the above Case 2 and Case 3, the following describes a method for the core network device to indicate to the terminal device whether to delete the first mobility management parameter.

[0289] FIG. 7 is a schematic flowchart of a communication method according to an embodiment of the present application.

[0290] S701: The core network device determines the first indication information.

[0291] The terminal device can access the core network device via the first access.

[0292] In a possible implementation, the core network device may determine whether to delete the first mobility management parameter for the first access based on the second indication information and the information about the second access. The second indication information indicates the reason why the core network device rejects the request of the terminal device.

[0293] The second indication information may be the first information in the above Example 2.

[0294] Regarding the implementation in which the core network device determines whether to delete the first mobility management parameter for the first access based on the second indication information and the information about the second access, refer to the implementation in which the core network device in the method of FIG. 5 determines whether to delete the first mobility management parameter for the first access based on the first information and the information about the second access.

[0295] In another possible implementation, the core network device may determine whether to delete the first mobility management parameter for the first access based on the first message and the information about the second access. For the first message, refer to the relevant description in the above Example 3.

[0296] Regarding the implementation in which the core network device determines whether to delete the first mobility management parameter for the first access based on the first message and the information about the second access, refer to the implementation in which the core network device in the method of FIG. 6 determines whether to delete the first mobility management parameter for the first access based on the first message and the information about the second access.

[0297] S702: The core network device transmits the first indication information to the terminal device via the first access. Correspondingly, the terminal device receives the first indication information via the first access.

[0298] The first indication information indicates whether to delete the first mobility management parameter for the first access.

[0299] The first indication information may indicate whether to delete the first mobility management parameter for the first access in an explicit indication method. For example, the first indication information may indicate whether to delete the first mobility management parameter for the first access by using different values of one or more bits. For example, the first indication information may indicate to delete the first mobility management parameter for the first access by using a first value of one or more bits, and may indicate not to delete the first mobility management parameter for the first access by using a second value.

[0300] Alternatively, the first indication information may indicate to delete the first mobility management parameter for the first access in an implicit indication method. For example, if the first indication information carries a specific field, the first indication information may indicate not to delete the first mobility management parameter for the first access, or if the first indication information does not carry a specific field, the first indication information may indicate to delete the first mobility management parameter for the first access.

[0301] Alternatively, the first indication information may indicate not to delete the first mobility management parameter for the first access in an implicit indication method. For example, if the first indication information carries a specific field, the first indication information may indicate to delete the first mobility management parameter for the first access, or if the first indication information does not carry a specific field, the first indication information may indicate not to delete the first mobility management parameter for the first access.

[0302] S703: The terminal device determines whether to delete the first mobility management parameter for the first access based on the first indication information.

[0303] In a possible implementation, the terminal device may determine whether to delete the first mobility management parameter for the first access based on the first indication information and the information about the second access.

[0304] In a specific implementation, the terminal device may determine whether to delete the first mobility management parameter for the first access based on the first indication information and the registration information about the second access.

[0305] For example, when the first indication information indicates to delete the first mobility management parameter for the first access, if the registration information about the second access satisfies one of the following conditions, that is, the PLMN is not registered via the second access, or the PLMN registered via the second access is different from the PLMN registered via the first access, the first mobility management parameter for the first access is determined to be deleted.

[0306] In another example, when the first indication information indicates to delete the first mobility management parameter for the first access and the PLMN registered via the second access is the same as the PLMN registered via the first access, whether to delete the first mobility management parameter for the first access is determined based on the service information about the second access. The service information about the second access is information about whether an emergency service is being performed on the second access.

[0307] For example, when an emergency service is being performed on the second access, it is determined that the first mobility management parameter for the first access is not deleted. Alternatively, when an emergency service is being performed on the second access, it is determined that the first mobility management parameter is deleted on the first access.

[0308] Optionally, the terminal device may further perform one or more of the following four solutions: deleting the second mobility management parameter and / or the third mobility management parameter, stopping the service being performed on the second access, starting the first timer for the second access, or releasing the N1 NAS signaling connection, or stopping the mobility management procedure being performed on the second access.

[0309] For the implementation of deleting the second mobility management parameter and / or the third mobility management parameter, stopping the service being performed via the second access, starting the first timer for the second access, or releasing the N1 NAS signaling connection, and stopping the mobility management procedure being performed on the second access, please refer to the relevant description of the method in FIG. 5.

[0310] Optionally, after determining not to delete the first mobility management parameter, the terminal device (or core network device) may perform the corresponding action. For example, the first mobility management parameter is not deleted, or the first mobility management parameter is reserved, or the first mobility management parameter is not processed.

[0311] Optionally, after determining to delete the first mobility management parameter, the terminal device (or core network device) may perform the corresponding action. For example, the first mobility management parameter is deleted.

[0312] For the implementation of deleting the first mobility management parameter, please refer to the relevant description of the method in FIG. 4.

[0313] In this embodiment of the present application, the network device indicates to the terminal device whether to delete the first mobility management parameter for the first access, thus reducing the complexity of the terminal device.

[0314] Furthermore, when the first mobility management parameter for the first access is deleted, considering the information for the second access, the first mobility management parameter may not be deleted when the first mobility management parameter is required on the second access, and thus, the terminal device may use the first mobility management parameter for communication on the second access. This avoids the problem that normal communication may not be performed on the second access because the first mobility management parameter for the first access is deleted, and reduces the impact on communication on the second access.

[0315] Based on the same concept as the method embodiment, an embodiment of the present application provides a communication device. The structure of the communication device is shown in FIG. 8 and includes a processing module 801. Optionally, the device may further include a communication module 802.

[0316] In one implementation, the communication device may be configured to implement, in particular, the method implemented by the terminal device in the embodiment of FIG. 4. The device may be a terminal device, or may be a chip or a chip group or a part of a chip in the terminal device configured to implement the related method function. The processing module 801 is configured to determine that the terminal device on the first access is to be switched from the first PLMN to the second PLMN, and not to delete the first mobility management parameter for the first access when the state of the terminal device on the second access is that the terminal device is registered with the first PLMN or has been registered with the first PLMN, and to determine to delete the first mobility management parameter when the state on the second access is that the terminal device is not registered with the first PLMN, where the first access and the second access belong to different access types.

[0317] Optionally, the processing module 801 is further configured to determine that the first access is registered with the first PLMN before the terminal device determines to switch from the first PLMN to the second PLMN upon a switch of the first access on the terminal device.

[0318] After the processing module 801 determines not to delete the first mobility management parameter, the processing module 801 may be further configured to determine to delete the first mobility management parameter if the switch is performed from the first PLMN to the third PLMN on the second access.

[0319] For example, the first mobility management parameter includes at least one of a key set identifier or a globally unique temporary user equipment identifier, and the key set identifier identifies NAS security context information.

[0320] Optionally, the NAS security context information includes a security encryption algorithm, and the security encryption algorithm is a null encryption algorithm.

[0321] In one implementation, the communication device may be configured to implement, in particular, the method implemented by the terminal device in the embodiment of FIG. 5. The device may be a terminal device, or a chip or chip group or part of a chip in the terminal device configured to implement the related method functions. The communication module 802 is configured to obtain first information via a first access of the terminal device. The processing module 801 is configured to determine whether to delete the first mobility management parameter for the first access based on the first information and information about a second access of the terminal device. The first information indicates a reason for the core network device to reject a request of the terminal device and that the first access and the second access belong to different access types.

[0322] Optionally, the first information is not applicable to the second access. When determining whether to delete the first mobility management parameter based on the first information and the information about the second access of the terminal device, the processing module 801 is configured to determine whether to delete the first mobility management parameter based on, in particular, the first information and the registration information about the second access.

[0323] When determining whether to delete the first mobility management parameter based on the first information and the registration information about the second access, the processing module 801 is configured to determine to delete the first mobility management parameter when, in particular, the registration information about the second access satisfies one of the following conditions: that is, the PLMN is not registered via the second access, or the PLMN registered via the second access is different from the PLMN registered via the first access.

[0324] When determining whether to delete the first mobility management parameter based on the first information and the registration information about the second access, the processing module 801 is configured to determine not to delete the first mobility management parameter when, in particular, the registration information about the second access satisfies the following condition: that is, the PLMN registered via the second access is the same as the PLMN registered via the first access.

[0325] Optionally, the first information is applicable to the second access. When determining whether to delete the first mobility management parameter based on the first information and the information about the second access of the terminal device, the processing module 801 is configured to determine whether to delete the first mobility management parameter based on, in particular, the first information, the registration information about the second access, and the service information about the second access, where the service information about the second access is information about whether an emergency service is being performed on the second access.

[0326] When processing the first mobility management parameter based on the first information, the registration information about the second access, and the service information about the second access, the processing module 801 is configured to determine to delete the first mobility management parameter, particularly when the registration information about the second access and the service information about the second access satisfy one of the following conditions: the PLMN is not registered via the second access; the PLMN registered via the second access is different from the PLMN registered via the first access; or the PLMN registered via the second access is the same as the PLMN registered via the first access and the emergency service is not being performed on the second access.

[0327] When processing the first mobility management parameter based on the first information, the registration information about the second access, and the service information about the second access, the processing module 801 is configured to determine not to delete the first mobility management parameter, particularly when the registration information about the second access and the service information about the second access satisfy the following condition: the PLMN registered via the second access is the same as the PLMN registered via the first access and the emergency service is being performed on the second access.

[0328] Optionally, the processing module 801 is further configured to determine to delete the first mobility management parameter after the emergency service ends.

[0329] Optionally, when the processing module 801 determines to delete the first mobility management parameter, it is further configured to delete the second mobility management parameter, where the second mobility management parameter includes at least one of the last visited tracking area identifier for the second access or the tracking area identifier list for the second access.

[0330] Optionally, when the processing module 801 determines to delete the first mobility management parameter, it is further configured to stop the service being performed on the second access.

[0331] Optionally, when the processing module 801 determines to delete the first mobility management parameter, it is to start a first timer for the second access, where the first timer is used to trigger the terminal device to release the N1 NAS signaling connection, or it is further configured to release the N1 NAS signaling connection.

[0332] Optionally, when the processing module 801 determines that the first mobility management parameter is to be deleted and the mobility management procedure is being performed on the second access, it is further configured to stop the mobility management procedure.

[0333] For example, the first mobility management parameter includes at least one of a key set identifier or a globally unique temporary user equipment identifier, and the key set identifier identifies NAS security context information.

[0334] In one implementation, the communication device may be further configured to implement the method implemented by the core network device in the embodiment of FIG. 5. For details, refer to the above related description. Here, the details will not be described again. The device may be a core network device, or a chip or a chip group or a part of a chip in the core network device configured to implement the related method functions. The communication module 802 is configured to transmit first information to the terminal device via a first access of the terminal device, where the first information indicates the reason why the core network device rejects the request of the terminal device. The processing module 801 is configured to determine whether to delete the first mobility management parameter for the first access based on the first information and the information about the second access of the terminal device, where the first access and the second access belong to different access types.

[0335] Optionally, the first information is not applicable to the second access. When determining whether to delete the first mobility management parameter based on the first information and the information about the second access, the processing module 801 is configured to determine whether to delete the first mobility management parameter based on, in particular, the first information and the registration information about the second access.

[0336] When determining whether to delete the first mobility management parameter based on the first information and the registration information about the second access, the processing module 801 is configured to determine to delete the first mobility management parameter when, in particular, the registration information about the second access satisfies one of the following conditions, i.e., the PLMN is not registered via the second access.

[0337] When determining whether to delete the first mobility management parameter based on the first information and the registration information about the second access, the processing module 801 is configured to, in particular, not delete the first mobility management parameter when the registration information about the second access satisfies the following condition, that is, the PLMN registered via the second access is the same as the PLMN registered via the first access.

[0338] Optionally, the first information is applicable to the second access. When determining whether to delete the first mobility management parameter based on the first information and the information about the second access, the processing module 801 is configured to, in particular, determine whether to delete the first mobility management parameter based on the first information, the registration information about the second access, and the service information about the second access, where the service information about the second access is information about whether an emergency service is being performed on the second access.

[0339] When processing the first mobility management parameter based on the first information, the registration information about the second access, and the service information about the second access, the processing module 801 is configured to, in particular, determine to delete the first mobility management parameter when the registration information about the second access and the service information about the second access satisfy one of the following conditions: that is, the PLMN is not registered via the second access, or the PLMN registered via the second access is the same as the PLMN registered via the first access and an emergency service is not being performed on the second access.

[0340] When processing the first mobility management parameter based on the first information, the registration information about the second access, and the service information about the second access, the processing module 801 is configured to, in particular, determine not to delete the first mobility management parameter when the registration information about the second access and the service information about the second access satisfy the following conditions: the PLMN registered via the second access is the same as the PLMN registered via the first access, and the emergency service is being carried out on the second access.

[0341] Optionally, the processing module 801 is further configured to determine to delete the first mobility management parameter after the emergency service ends.

[0342] Optionally, when the processing module 801 determines to delete the first mobility management parameter, it is further configured to delete the second mobility management parameter, where the second mobility management parameter includes at least one of the last visited tracking area identifier for the second access or the tracking area identifier list for the second access.

[0343] Optionally, when the processing module 801 determines to delete the first mobility management parameter, it is further configured to stop the service being carried out on the second access.

[0344] Optionally, when the processing module 801 determines to delete the first mobility management parameter, it is further configured to release the N1 NAS signaling connection.

[0345] Optionally, when the processing module 801 determines that the first mobility management parameter is to be deleted and the mobility management procedure is being carried out on the second access, it is further configured to stop the mobility management procedure.

[0346] For example, the first mobility management parameter includes at least one of a key set identifier or a globally unique temporary user equipment identifier, and the key set identifier identifies NAS security context information.

[0347] In one implementation, the communication device may be configured to implement, in particular, the method implemented by the terminal device in the embodiment of FIG. 7. The device may be a terminal device, or may be a chip or a chip group or a part of a chip in the terminal device configured to implement the related method functions. The communication module 802 is configured to receive first indication information via a first access of the terminal device, where the first indication information indicates whether to delete the first mobility management parameter for the first access. The processing module 801 is configured to determine whether to delete the first mobility management parameter for the first access based on the first indication information, where the first access and the second access belong to different access types.

[0348] When determining whether to delete the first mobility management parameter based on the first indication information, the processing module 801 may be configured to determine whether to delete the first mobility management parameter based on, in particular, the first indication information and the information about the second access.

[0349] When determining whether to delete the first mobility management parameter based on the first indication information and the information about the second access, the processing module 801 may be configured to determine whether to delete the first mobility management parameter based on, in particular, the first indication information and the registration information about the second access.

[0350] When determining whether to delete the first mobility management parameter based on the first indication information and the registration information about the second access, the processing module 801 is configured to, in particular, when the first indication information indicates deleting the first mobility management parameter, determine to delete the first mobility management parameter when the registration information about the second access satisfies one of the following conditions: that is, the PLMN is not registered via the second access, or the PLMN registered via the second access is different from the PLMN registered via the first access.

[0351] When determining whether to delete the first mobility management parameter based on the first indication information and the registration information about the second access, the processing module 801 is configured to, in particular, when the first indication information indicates deleting the first mobility management parameter and the PLMN registered via the second access is the same as the PLMN for which registration is not performed via the first access, determine whether to delete the first mobility management parameter based on the service information about the second access, where the service information about the second access is information about whether an emergency service is being performed on the second access.

[0352] When determining whether to delete the first mobility management parameter based on the service information about the second access, the processing module 801 is configured to, in particular, determine not to delete the first mobility management parameter when an emergency service is being performed on the second access, or determine to delete the first mobility management parameter when an emergency service is not being performed on the second access.

[0353] Optionally, when the processing module 801 determines to delete the first mobility management parameter, it is further configured to determine to delete the first mobility management parameter after the emergency service ends.

[0354] Optionally, when the processing module 801 determines to delete the first mobility management parameter, it is further configured to delete the second mobility management parameter, where the second mobility management parameter includes at least one of the last visited tracking area identifier for the second access or the tracking area identifier list for the second access.

[0355] Optionally, when the processing module 801 determines to delete the first mobility management parameter, it is further configured to stop the service being performed on the second access.

[0356] Optionally, when the processing module 801 determines to delete the first mobility management parameter, it is further configured to start a first timer for the second access, where the first timer is used to trigger the terminal device to release the N1 NAS signaling connection, or it is further configured to release the N1 NAS signaling connection.

[0357] Optionally, when the processing module 801 determines that the first mobility management parameter is to be deleted and the mobility management procedure is being performed on the second access, it is further configured to stop the mobility management procedure.

[0358] For example, the first mobility management parameter includes at least one of a key set identifier or a globally unique temporary user equipment identifier, and the key set identifier identifies NAS security context information.

[0359] In one implementation, the communication device may be further configured to implement the method implemented by the core network device in the embodiment of FIG. 7. For details, refer to the above related description. Here, the details will not be described again. The device can be a core network device, or a chip or chip group or a part of a chip in the core network device configured to implement the related method functions. The processing module 801 is configured to determine first indication information. The communication module 802 is configured to transmit the first indication information to the terminal device via a first access to the terminal device, where the first indication information indicates whether to delete the first mobility management parameter for the first access, and the first access and the second access belong to different access types.

[0360] In particular, the processing module 801 may be configured to determine the first indication information based on the second indication information and the information about the second access, where the second indication information indicates the reason why the core network device rejects the request of the terminal device.

[0361] The second indication information is not applicable to the second access. In particular, the processing module 801 may be configured to determine the first indication information based on the second indication information and the registration information about the second access.

[0362] The processing module 801 is configured to, in particular, indicate to delete the first mobility management parameter by the first indication information when the registration information for the second access satisfies one of the following conditions, i.e., the PLMN is not registered via the second access, or to indicate not to delete the first mobility management parameter by the first indication information by the core network device when the registration information for the second access satisfies the following conditions, i.e., the PLMN is registered or is registered via the second access.

[0363] The second indication information is applicable to the second access. The processing module 801 is configured to, in particular, determine the first indication information by the core network device based on the second indication information, the registration information for the second access, and the service information for the second access, where the service information for the second access is information on whether an emergency service is being performed on the second access.

[0364] The processing module 801 is configured to, in particular, indicate to delete the first mobility management parameter by the first indication information when the registration information for the second access and the service information for the second access satisfy one of the following conditions, i.e., the PLMN is not registered via the second access, or the PLMN is registered or is registered via the second access and the emergency service is not being performed on the second access.

[0365] In particular, the processing module 801 can be configured such that, according to the first indication information, the registration information about the second access and the service information about the second access satisfy the following conditions, that is, the PLMN is registered or registered via the second access, and the emergency service is not implemented on the second access, and the first mobility management parameter is not deleted.

[0366] For example, the first mobility management parameter may include at least one of a key set identifier or a globally unique temporary user equipment identifier, and the key set identifier identifies NAS security context information.

[0367] Furthermore, the communication device can be further configured to implement the method implemented by the communication device (for example, a terminal device or a core network device) in the embodiment of FIG. 6. The device can be a communication device, or a chip or a chip group or a part of a chip in a communication device configured to implement related method functions.

[0368] In the embodiments of the present application, the division into modules is an example and is only a division of logical functions, and other divisions during actual implementation are possible. Furthermore, the functional modules in the embodiments of the present application can be integrated into one processor, can physically exist alone, or two or more modules can be integrated into one module. The integrated module can be implemented in the form of hardware or in the form of a software function module. For the functions or implementations of the modules in this embodiment of the present application, it can be understood that reference should be further made to the related descriptions in the method embodiments.

[0369] In a possible manner, the communication device can be as shown in FIG. 9. This device can be a communication device or a chip in a communication device. The communication device can be the terminal device in the above embodiments or the network device in the above embodiments. This device includes a processor 901 and a communication interface 902, and may further include a memory 903. The processor module 801 can be the processor 901. The communication module 802 can be the communication interface 902.

[0370] The processor 901 can be a CPU, a digital processing unit, etc. The communication interface 902 can be an interface circuit such as a transceiver, a transceiver circuit, a transceiver chip, etc. This device further includes a memory 903 configured to store a program executed by the processor 901. The memory 903 can be a non-volatile memory, for example, a hard disk drive (HDD) or a solid-state drive (SSD), or a volatile memory, for example, a random-access memory (RAM). The memory 903 can be used to carry and store program code expected in the form of instructions or data structures, and can be any other medium accessible by a computer, but is not limited thereto.

[0371] The processor 901 is configured to execute the program code stored in the memory 903, and in particular, is configured to perform the actions of the processing module 801. Details are not described again here in this application. The communication interface 902 is particularly configured to perform the actions of the communication module 802. Details are not described here in this application.

[0372] In this embodiment of the present application, the specific connection medium between the communication interface 902, the processor 901, and the memory 903 is not limited. In this embodiment of the present application, the memory 903, the processor 901, and the communication interface 902 are connected through the bus 904 in FIG. 9. The bus is represented by using the thick line in FIG. 9. The above is only an example for explanation. The connection methods of other components are not limited thereto. The bus can be classified into an address bus, a data bus, a control bus, etc. For the sake of simplicity of expression, only one thick line is used to represent the bus in FIG. 9, but this does not mean that there is only one bus or only one type of bus.

[0373] The embodiment of the present application further provides a computer-readable storage medium configured to store computer software instructions that need to be executed by the above-mentioned processor. The computer software instructions include a program that needs to be executed by the above-mentioned processor.

[0374] The embodiment of the present application further provides a communication system including a communication device configured to realize the functions of the terminal device in the embodiment of FIG. 4 and a communication device configured to realize the functions of the network device in the embodiment of FIG. 4.

[0375] The embodiment of the present application further provides a communication system including a communication device configured to realize the functions of the terminal device in the embodiment of FIG. 5 and a communication device configured to realize the functions of the network device in the embodiment of FIG. 5.

[0376] The embodiment of the present application further provides a communication system including a communication device configured to realize the functions of the terminal device in the embodiment of FIG. 6 and a communication device configured to realize the functions of the network device in the embodiment of FIG. 6.

[0377] Embodiments of the present application further provide a communication system including a communication device configured to implement the functions of the terminal device in the embodiment of FIG. 7 and a communication device configured to implement the functions of the network device in the embodiment of FIG. 7.

[0378] Those skilled in the art should understand that embodiments of the present application can be provided as a method, a system, or a computer program product. Therefore, the present application can use forms of embodiments that use only hardware embodiments, only software embodiments, or embodiments that use a combination of software and hardware. Further, the present application can use forms of a computer program product implemented on one or more computer-usable storage media including computer-usable program code (including, but not limited to, disk memory, CD-ROM, optical memory, etc.).

[0379] The present application will be described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the present application. It should be understood that computer program instructions can be used to implement each step and / or each block in the flowchart and / or block diagram, as well as combinations of steps and / or blocks in the flowchart and / or block diagram. These computer program instructions can be provided for the processor of a general-purpose computer, a dedicated computer, an embedded processor, or any other programmable data processing device to generate a machine, and thus, the instructions executed by the processor of a computer or any other programmable data processing device generate an apparatus for realizing specific functions in one or more steps in the flowchart and / or one or more blocks in the block diagram.

[0380] These computer program instructions may alternatively be stored in a computer-readable memory which can direct a computer or any other programmable data processing device to operate in a particular manner, and thus, the instructions stored in the computer-readable memory produce an article of manufacture including instruction means. The instruction means implements the particular functions embodied in one or more steps in the flowchart and / or one or more blocks in the block diagram.

[0381] Alternatively, the computer program instructions may be loaded onto a computer or another programmable data processing device, and thus, a series of operations and steps are executed on the computer or another programmable device to produce a computer implemented process. Accordingly, the instructions executed on the computer or another programmable device provide steps for implementing the particular functions embodied in one or more steps in the flowchart and / or one or more blocks in the block diagram.

[0382] Obviously, it is obvious that those skilled in the art can make various modifications and changes to this application without departing from the spirit and scope of this application. In this way, when these modifications and changes to this application fall within the scope of the claims of this application and their equivalent technologies, this application is intended to cover these modifications and changes as well.

Claims

1. A communication method, which is applied to a terminal device, and the method includes: registering, by the terminal device, with a first public land mobile network (PLMN) via a first access; determining that the terminal device on the first access is to be switched from the first PLMN to a second PLMN other than the first PLMN and a PLMN equivalent to the first PLMN; determining to delete first mobility management parameters when the state of the terminal device on a second access indicates that the terminal device is not registered with the first PLMN or has not been registered with the first PLMN; wherein the first access and the second access belong to different access types; a method.

2. The method further includes: determining not to delete the first mobility management parameters; and determining to delete the first mobility management parameters when the switching is performed from the first PLMN to a third PLMN via the second access. The method according to claim 1.

3. The first mobility management parameters include at least one of a key set identifier or a globally unique temporary user equipment identifier, and the key set identifier identifies non-access stratum (NAS) security context information. The method according to claim 1 or 2.

4. The NAS security context information includes a security encryption algorithm, and the security encryption algorithm is a null encryption algorithm. The method according to claim 3.

5. A communication method, which is applied to a terminal device, and the method includes: obtaining first information via a first access of the terminal device, where the first information indicates a reason for a core network device to reject a request of the terminal device; and determining whether to delete first parameters based on the first information and information about a second access of the terminal device. wherein the first access and the second access belong to different access types; a method.

6. The first information is not applicable to the second access. ​ The step of determining whether to delete the first parameter based on the first information and information about a second access of the terminal device is including a step of determining whether to delete the first parameter based on the first information and registration information about the second access The method according to claim 5.

7. The step of determining whether to delete the first parameter based on the first information and registration information about the second access is including a step of determining to delete the first parameter when the registration information about the second access satisfies one of the following conditions: that is, the public land mobile network PLMN is not registered via the second access, or the PLMN registered via the second access is different from the PLMN registered via the first access The method according to claim 6.

8. The step of determining whether to delete the first parameter based on the first information and registration information about the second access is including a step of determining not to delete the first parameter when the registration information about the second access satisfies the following condition: that is, the PLMN registered via the second access is the same as the PLMN registered via the first access The method according to claim 6 or 7.

9. The first information is applicable to the second access The step of determining whether to delete the first parameter based on the first information and information about a second access of the terminal device is a step of determining whether to delete the first parameter based on the first information, the registration information about the second access, and service information about the second access, wherein the service information about the second access is information about whether an emergency service is being performed on the second access The method according to claim 5.

10. The step of processing the first parameter based on the first information, the registration information about the second access, and the service information about the second access is The step of determining to delete the first parameter includes that the registration information about the second access and the service information about the second access satisfy the following conditions, that is, the PLMN is not registered via the second access, the PLMN registered via the second access is different from the PLMN registered via the first access, or the PLMN registered via the second access is the same as the PLMN registered via the first access, and the emergency service is not being carried out on the second access, when one of the above is satisfied. The method according to claim 9.

11. The step of determining whether to delete the first parameter based on the first information, the registration information about the second access, and the service information about the second access includes the step of determining not to delete the first parameter when the registration information about the second access and the service information about the second access satisfy the following conditions, that is, the PLMN registered via the second access is the same as the PLMN registered via the first access, and the emergency service is being carried out on the second access. The method according to claim 9 or 10.

12. The method further includes the step of determining to delete the first parameter after the emergency service ends. The method according to claim 11.

13. When it is determined that the first parameter is to be deleted, the method further includes the step of deleting a second parameter, where the second parameter includes at least one of the last visited tracking area identifier for the second access or the tracking area identifier list for the second access. The method according to any one of claims 5 to 12.

14. When it is determined that the first parameter is to be deleted, the method further includes the step of stopping the service being carried out on the second access. The method according to any one of claims 5 to 13.

15. When it is determined that the first parameter is to be deleted, the method A step of starting a first timer for the second access, wherein the first timer is used to trigger the terminal device to release an N1 non-access stratum signaling connection, or A step of releasing an N1 non-access stratum signaling connection further comprising The method according to any one of claims 5 to 14.

16. When it is determined that the first parameter is deleted, the method further comprises When a mobility management procedure is being performed on the second access, a step of stopping the mobility management procedure. The method according to any one of claims 5 to 15.

17. The first parameter includes at least one of a key set identifier or a globally unique temporary user equipment identifier, and the key set identifier identifies security context information. The method according to any one of claims 5 to 16.

18. A communication device including a unit or module configured to perform the method according to any one of claims 1 to 4, or including a unit or module configured to perform the method according to any one of claims 5 to 17.

19. A communication device, the device including a processor and a memory, the processor being coupled to the memory, the memory being configured to store a program or instructions, the processor being configured to call the program or the instructions to enable the communication device to perform the method according to any one of claims 1 to 4 or to perform the method according to any one of claims 5 to 17. Communication device.

20. A computer-readable storage medium, the computer-readable storage medium being configured to store computer instructions, and when the computer instructions are executed on a computer, the computer is enabled to execute the method according to any one of claims 1 to 17.

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