Communication systems, methods, apparatuses, and storage media

Abstract

The application provides a communication system, method, device and storage medium, relates to the technical field of communication, and can realize redirection of a connected state terminal device between networks of multiple operators in the process of sharing a core network by the multiple operators. The method comprises the following steps: a target AMF receives a redirection request from a target access network device; the redirection request comprises a first globally unique temporary identity (GUTI) of the terminal device; the first GUTI is the GUTI of the terminal device in a first PLMN network; the target AMF determines the first GUTI of the terminal device according to the redirection request, and determines a source AMF according to the first GUTI; the target AMF sends a session information request message to the source AMF; and the target AMF receives session information of the terminal device from the source AMF. The embodiments of the application are used in the redirection process of the multiple operators sharing the core network.

Description

Technical Field

[0001] This application relates to the field of communication technology, and in particular to a communication system, method, apparatus and storage medium. Background Technology

[0002] In related technologies, when multiple operators share a network, they typically only share access network equipment, which is then connected to the core network equipment of each operator. Terminal devices access the core network equipment to which they belong through the shared access network equipment.

[0003] There is a current demand for multiple operators to share a core network, but there is a lack of solutions in the relevant technologies for redirecting connected terminal devices between the networks of multiple operators when multiple operators share a core network. Summary of the Invention

[0004] This application provides a communication system, method, apparatus, and storage medium that enables connected terminal devices to redirect between the networks of multiple operators during the process of sharing a core network.

[0005] To achieve the above objectives, this application adopts the following technical solution: In a first aspect, a communication system is provided, comprising: a terminal device, a source access network device, a source access and mobility management function (AMF), a target AMF, and a target access network device; the source access network device and the source AMF belong to a first public land mobile network (PLMN); the target AMF belongs to a second PLMN; the source AMF and the target AMF are connected via a communication interface; the source access network device is used to determine the frequency point information of the target access network device and send the frequency point information to the terminal device; the terminal device is used to determine the target access network device based on the frequency point information and initiate a redirection request to the target access network device; the redirection request includes a first globally unique temporary identifier (GUTI) of the terminal device; the first GUTI is the GUTI of the terminal device in the first PLMN; the target access network device is used to forward the redirection request to the target AMF; the target AMF is used to determine the first GUTI of the terminal device, determine the source AMF based on the first GUTI, and send a session information request message to the source AMF; the source AMF is used to respond to the session request message and send session information of the terminal device to the target AMF.

[0006] In conjunction with the first aspect above, in one possible implementation, the source access network device is specifically used to: determine the target PLMN identifier ID; the target PLMN ID is the PLMN ID that the terminal device needs to select when accessing the second PLMN network; and determine the frequency information of the PLMN network corresponding to the target PLMN ID as the frequency information of the target access network device.

[0007] In conjunction with the first aspect above, in one possible implementation, the target AMF is further configured to send a first request message to the source AMF; the first request message is configured to request the context information of the terminal device and the user permanent identifier SUPI; the source AMF is configured to send a first response message to the target AMF according to the first request message; the first response message includes the context information of the terminal device and the SUPI; the target AMF is further configured to determine the terminal device according to the SUPI and create a context for the terminal device according to the context information.

[0008] In conjunction with the first aspect above, in one possible implementation, the target AMF is specifically used for: parsing the first GUTI, determining the globally unique AMF identifier GUAMI in the first GUTI; and determining that the AMF represented by GUAMI is the source AMF.

[0009] In conjunction with the first aspect above, in one possible implementation, the source AMF is further configured to send a PLMN list to the source access network device; the PLMN list includes at least one of the following: the terminal device's HPLMN, the serving PLMN, the equivalent public land mobile network (EPLMN), and the previously selected PLMN; the source access network device is further configured to determine the target PLMN from the PLMN list.

[0010] In conjunction with the first aspect above, in one possible implementation, the source access network device is specifically used to: determine the current serving PLMN ID of the terminal device based on the PLMN list; determine the home network of the terminal device based on the serving PLMN ID of the terminal device; determine the PLMN ID of the home network of the terminal device in the second PLMN network as the first PLMN ID; and determine the first PLMN ID as the target PLMN ID.

[0011] In conjunction with the first aspect above, in one possible implementation, the source AMF is further configured to send a mobility restriction list to the source access network device; the mobility restriction list is used to indicate a first PLMN ID; the first PLMN ID is the PLMN ID of the terminal device's home network in the second PLMN network; the source access network device is configured to receive the mobility restriction list and determine that the first PLMN ID indicated by the mobility restriction list is the target PLMN ID.

[0012] In conjunction with the first aspect above, in one possible implementation, the source AMF is specifically used for: determining the location information of the terminal device; determining that the PLMN network adjacent to the first PLMN network at the location represented by the location information of the terminal device is the second PLMN network; determining the PLMN ID in the second PLMN network that allows the terminal device to access the network; and determining the PLMN ID that allows the terminal device to access the network as the first PLMN ID.

[0013] In conjunction with the first aspect above, in one possible implementation, the source access network device is further configured to: determine the access network device adjacent to the source access network device in the second PLMN network as the target access network device; and determine the frequency point information of the target access network device.

[0014] In conjunction with the first aspect above, in one possible implementation, the target access network device is further configured to: obtain the target PLMN ID, the location information of the terminal device, and the slice information requested by the terminal device; and determine the target AMF based on the target PLMN ID, the location information of the terminal device, and the slice information requested by the terminal device.

[0015] In conjunction with the first aspect mentioned above, in one possible implementation, the source AMF is further used to send first slice indication information to the target AMF; the first slice indication information is used to indicate first slice information, which is the slice information of the terminal device in its home network.

[0016] In conjunction with the first aspect mentioned above, in one possible implementation, the source AMF is specifically used for: determining the first slice information when the PLMN IDs of the source AMF and the target AMF are different; and generating a first slice indication message based on the first slice information. In conjunction with the first aspect above, in one possible implementation, the first indication information is specifically used to indicate at least one of the slice information of the terminal device in the first PLMN network and the slice information of the terminal device mapped in the first network in the home network; the target AMF is specifically used to: determine the slice information of the terminal device in the first PLMN network as the first slice information when the first PLMN network is the home network; and determine the slice information of the terminal device mapped in the first network in the home network as the first slice information when the first PLMN network is not the home network.

[0017] In conjunction with the first aspect above, in one possible implementation, the target AMF is further configured to: determine first slice information; determine second slice information mapped by the first slice information in the second PLMN network; determine the target session management function SMF based on at least one of the second slice information and the location information of the terminal device; the target SMF is the SMF in the second PLMN network.

[0018] In conjunction with the first aspect above, in one possible implementation, the target AMF is further configured to send a registration status update message to the source AMF; the registration status update message is configured to instruct the source AMF to release a preset session; the preset session is a session established by the source AMF for the terminal device that is not supported by the target AMF; the source AMF is further configured to release the preset session in response to the registration status update message.

[0019] In conjunction with the first aspect mentioned above, in one possible implementation, the system further includes: a Home Unified Data Management (UDM); a target AMF, which is also used to send a context request message to the home UDM; the context request message is used to request the terminal device's subscription data from the UDM; the UDM is used to respond to the context request message and send the terminal device's subscription data to the target AMF. The target AMF is also used to obtain the terminal device's subscription data from the source AMF through a communication interface.

[0020] In conjunction with the first aspect mentioned above, in one possible implementation, the system further includes: a target network slice selection function (NSSF); a target AMF, which is also used to query the target NSSF based on the first slice information to determine the second slice information, and a list of AMFs that support the second slice information.

[0021] In conjunction with the first aspect mentioned above, in one possible implementation, the target AMF is further configured to query the slice mapping relationship configured in the target AMF based on the first slice information, determine the second slice information, and the list of AMFs that support the second slice information.

[0022] In conjunction with the first aspect above, in one possible implementation, the system further includes: a first AMF; a target AMF, further configured to: determine whether the AMF list includes the target AMF; the first AMF is an AMF in the AMF list; if not included, determine the first AMF based on the AMF list.

[0023] In conjunction with the first aspect above, in one possible implementation, the target AMF is further configured to send first indication information to the target access network device. The first indication information includes at least one of the following: the identifier of the first AMF, a registration request message, and second slice information. The target access network device is configured to generate second indication information based on the first indication information and send the second indication information to the first AMF. The second indication information includes at least one of the following: the identifier of the first AMF, a registration request message, and second slice information. The first AMF is configured to determine at least one of the identifier of the first AMF, the registration request message, and the second slice information based on the second indication information.

[0024] In conjunction with the first aspect above, in one possible implementation, the target AMF is further configured to send third indication information to the first AMF; the third indication information includes at least one of the following: a registration request message, a SUPI of the terminal pole device, a context of the terminal device, and second slice information; the first AMF is configured to determine at least one of the registration request message, the SUPI of the terminal pole device, the context of the terminal device, and the second slice information based on the third indication information.

[0025] In conjunction with the first aspect mentioned above, in one possible implementation, the system further includes: a Home SMF and a Home Policy Control Function (PCF); the Home SMF is also used to send a fourth indication message to the Home PCF; the fourth indication message is used to instruct SM policy management to be performed; and the location information of the terminal device is indicated to the Home PCF.

[0026] In conjunction with the first aspect above, in one possible implementation, the target AMF is further configured to send a fifth indication message to the target access network device, the fifth indication message indicating at least one of the PLMN list and the mobility restriction list.

[0027] Secondly, a communication method is provided, applied in a communication system, the communication system including: a terminal device, a source access network device, a source access and mobility management function (AMF), a target AMF, and a target access network device; the source access network device and the source AMF belong to a first public land mobile network (PLMN); the target AMF belongs to a second PLMN; the source AMF and the target AMF are connected through a communication interface; the method includes: the target AMF receiving a redirection request from the target access network device; the redirection request includes a first globally unique temporary identifier (GUTI) of the terminal device; the first GUTI is the GUTI of the terminal device in the first PLMN; the target AMF determines the first GUTI of the terminal device according to the redirection request, and determines the source AMF according to the first GUTI; the target AMF sends a session information request message to the source AMF; the target AMF receives session information of the terminal device from the source AMF.

[0028] In conjunction with the second aspect above, in one possible implementation, obtaining the session information of the terminal device from the source AMF includes: the target AMF sending a first request message to the source AMF; the first request message is used to request the context information and user permanent identifier (SUPI) of the terminal device; the target AMF receiving a first response message from the source AMF; the first response message includes the context information and SUPI of the terminal device; the target AMF determining the terminal device based on the SUPI and creating a context for the terminal device based on the context information.

[0029] In conjunction with the second aspect above, in one possible implementation, determining the source AMF based on the first GUTI includes: the target AMF parsing the first GUTI to determine the globally unique AMF identifier GUAMI in the first GUTI; and the target AMF determining that the AMF represented by GUAMI is the source AMF.

[0030] In conjunction with the second aspect above, in one possible implementation, after determining the source AMF based on the first GUTI, the method further includes: the target AMF sending a registration status update message to the source AMF; the registration status update message is used to instruct the source AMF to release a preset session; the preset session is a session established by the source AMF for the terminal device that is not supported by the target AMF.

[0031] In conjunction with the second aspect above, in one possible implementation, after the target AMF sends a registration status update message to the source AMF, the method further includes: the target AMF sending a context request message to the home unified data management function (UDM); the context request message is used to request the terminal device's subscription data from the UDM; and the target AMF receives the terminal device's subscription data from the UDM.

[0032] In conjunction with the second aspect above, in one possible implementation, after the target AMF sends a registration status update message to the source AMF, the method further includes: the target AMF obtaining the subscription data of the terminal device from the source AMF through a communication interface.

[0033] In conjunction with the second aspect above, in one possible implementation, the method further includes: the target AMF initiating a query to the target network slice selection function NSSF based on the first slice information to determine the second slice information and the AMF list that supports the second slice information, wherein the first slice information is the slice information of the terminal device in its home network.

[0034] In conjunction with the second aspect above, in one possible implementation, after the target AMF initiates a query to the target network slice selection function NSSF based on the first slice information to determine the second slice information and the list of AMFs supporting the second slice information, the method further includes: the target AMF determining whether the AMF list includes the target AMF; the first AMF is the AMF in the AMF list; if not, the target AMF determines the first AMF based on the AMF list.

[0035] In conjunction with the second aspect above, in one possible implementation, after the target AMF determines the first AMF according to the AMF list, the method further includes: the target AMF sending first indication information to the target access network device, so that the target access network device forwards at least one of the following to the first AMF: the identifier of the first AMF, a registration request message, and second slice information.

[0036] In conjunction with the second aspect above, in one possible implementation, after the target AMF determines the first AMF based on the AMF list, the method further includes: the target AMF sending third indication information to the first AMF; the third indication information includes at least one of the following: a registration request message, a SUPI of the terminal pole device, the context of the terminal device, and second slice information.

[0037] In conjunction with the second aspect above, in one possible implementation, the method further includes: the target AMF sending a fifth indication message to the target access network device, the fifth indication message being used to indicate at least one of the PLMN list and the mobility restriction list.

[0038] Thirdly, a communication method is provided, applied in a communication system, the communication system including: a terminal device, a source access network device, a source access and mobility management function (AMF), a target AMF, and a target access network device; the source access network device and the source AMF belong to a first public land mobile network (PLMN); the target AMF belongs to a second PLMN network; the source AMF and the target AMF are connected through a communication interface; the method includes: the source access network device determining the frequency point information of the target access network device and sending the frequency point information to the terminal device; the frequency point information of the target access network device is used to instruct the terminal device to access the target access network device according to the frequency point information, and the target access network device sends a redirection request to the terminal device.

[0039] In conjunction with the third aspect above, in one possible implementation, the source access network device determines the frequency information of the target access network device, including: the source access network device determines the target PLMN identifier ID; the target PLMN ID is the PLMN ID that the terminal device needs to select when accessing the second PLMN network; the source access network device determines the frequency information of the PLMN network corresponding to the target PLMN ID as the frequency information of the target access network device.

[0040] In conjunction with the third aspect above, in one possible implementation, after the source access network device sends frequency point information to the terminal device, the method further includes: the source access network device receiving a PLMN list from the source AMF; the PLMN list includes at least one of the following: the terminal device's HPLMN, the serving PLMN, the equivalent public land mobile network (EPLMN), and the previously selected PLMN; the source access network device determines the target PLMN from the PLMN list.

[0041] In conjunction with the third aspect above, in one possible implementation, the source access network device determines the target PLMN from the PLMN list, including: the source access network device determining the current serving PLMN ID of the terminal device according to the PLMN list; the source access network device determining the home network of the terminal device according to the serving PLMN ID of the terminal device; the source access network device determining the PLMN ID of the home network of the terminal device in the second PLMN network as the first PLMN ID; and the source access network device determining the first PLMN ID as the target PLMN ID.

[0042] In conjunction with the third aspect above, in one possible implementation, after the source access network device sends frequency point information to the terminal device, the method further includes: the source access network device receiving a mobility restriction list from the source AMF; the mobility restriction list is used to indicate a first PLMN ID; the first PLMN ID is the PLMN ID of the terminal device's home network in the second PLMN network; the source access network device determines that the first PLMN ID indicated by the mobility restriction list is the target PLMN ID.

[0043] In conjunction with the third aspect above, in one possible implementation, the source access network device determines the frequency point information of the target access network device, including: the source access network device determines that the access network device adjacent to the source access network device in the second PLMN network is the target access network device; the source access network device determines the frequency point information of the target access network device.

[0044] Fourthly, a communication method is provided, applied in a communication system, the communication system including: a terminal device, a source access network device, a source access and mobility management function (AMF), a target AMF, and a target access network device; the source access network device and the source AMF belong to a first public land mobile network (PLMN); the target AMF belongs to a second PLMN; the source AMF and the target AMF are connected through a communication interface; the method includes: the source AMF receiving a session information request message from the target AMF; wherein the source AMF is the AMF determined by the target AMF based on a first GUTI of the terminal device; and the source AMF responding to the session request message by sending session information of the terminal device to the target AMF.

[0045] In conjunction with the fourth aspect above, in one possible implementation, the method further includes: the source AMF sending a PLMN list to the source access network device; the PLMN list includes at least one of the following: the terminal device's HPLMN, the serving PLMN, the equivalent public land mobile network (EPLMN), and the previously selected PLMN.

[0046] In conjunction with the fourth aspect above, in one possible implementation, the method further includes: the source AMF sending a mobility restriction list to the source access network device; the mobility restriction list is used to indicate a first PLMN ID; the first PLMN ID is the PLMN ID of the terminal device's home network in the second PLMN network.

[0047] In conjunction with the fourth aspect above, in one possible implementation, before the source AMF sends the mobility restriction list to the source access network device, the method further includes: the source AMF determining the location information of the terminal device; the source AMF determining that the PLMN network adjacent to the first PLMN network at the location represented by the location information of the terminal device is the second PLMN network; the source AMF determining the PLMN ID in the second PLMN network that allows the terminal device to access the network; and the source AMF determining the PLMN ID that allows the terminal device to access the network as the first PLMN ID.

[0048] In conjunction with the fourth aspect above, in one possible implementation, the method further includes: the source AMF sending first slice indication information to the target AMF; the first slice indication information is used to indicate first slice information, which is the slice information of the terminal device in its home network.

[0049] In conjunction with the fourth aspect above, in one possible implementation, the method further includes: determining first slice information when the PLMN IDs of the source AMF and the target AMF are different; and generating a first slice indication message based on the first slice information. In conjunction with the fourth aspect above, in one possible implementation, the first indication information is specifically used to indicate at least one of the slice information of the terminal device in the first PLMN network and the slice information of the mapped terminal device in the home network in the first network.

[0050] In conjunction with the fourth aspect above, in one possible implementation, the method further includes: the source AMF receiving a registration status update message from the target AMF; the registration status update message instructing the source AMF to release a preset session; the preset session is a session established in the source AMF for the terminal device that is not supported by the target AMF; and the source AMF releasing the preset session in response to the registration status update message.

[0051] Fifthly, a communication apparatus is provided for use in a communication system, the communication system comprising: a terminal device, a source access network device, a source access and mobility management function (AMF), a target AMF, and a target access network device; the source access network device and the source AMF belong to a first public land mobile network (PLMN); the target AMF belongs to a second PLMN; the source AMF and the target AMF are connected via a communication interface; the apparatus comprises: a communication unit and a processing unit; the communication unit is used to receive a redirection request from the target access network device; the redirection request includes a first globally unique temporary identifier (GUTI) of the terminal device; the first GUTI is the GUTI of the terminal device in the first PLMN; the processing unit is used to determine the first GUTI of the terminal device according to the redirection request, and to determine the source AMF according to the first GUTI; the communication unit is further used to send a session information request message to the source AMF; the communication unit is further used to receive session information from the source AMF of the terminal device.

[0052] In conjunction with the fifth aspect above, in one possible implementation, the processing unit is specifically configured to: instruct the communication unit to send a first request message to the source AMF; the first request message is used to request the context information and user permanent identifier SUPI of the terminal device; instruct the communication unit to receive a first response message from the source AMF; the first response message includes the context information and SUPI of the terminal device; determine the terminal device based on the SUPI, and create a context for the terminal device based on the context information.

[0053] In conjunction with the fifth aspect above, in one possible implementation, the processing unit is specifically used to: parse the first GUTI, determine the globally unique AMF identifier GUAMI in the first GUTI, and determine that the AMF represented by GUAMI is the source AMF.

[0054] In conjunction with the fifth aspect above, in one possible implementation, the communication unit is further configured to send a registration status update message to the source AMF; the registration status update message is used to instruct the source AMF to release a preset session; the preset session is a session established by the source AMF for the terminal device that is not supported by the target AMF.

[0055] In conjunction with the fifth aspect above, in one possible implementation, the communication unit is further configured to send a context request message to the home unified data management function (UDM); the context request message is used to request subscription data of the terminal device from the UDM; and the target AMF receives the subscription data of the terminal device from the UDM.

[0056] In conjunction with the fifth aspect above, in one possible implementation, the processing unit is further configured to instruct the communication unit to obtain the subscription data of the terminal device from the source AMF through the communication interface.

[0057] In conjunction with the fifth aspect above, in one possible implementation, the processing unit is further configured to initiate a query to the target network slice selection function NSSF based on the first slice information to determine the second slice information and the AMF list supporting the second slice information, wherein the first slice information is the slice information of the terminal device in its home network.

[0058] In conjunction with the fifth aspect above, in one possible implementation, the processing unit is further configured to determine whether the AMF list includes the target AMF; the first AMF is the AMF in the AMF list; if it does not include the target AMF, then the first AMF is determined according to the AMF list.

[0059] In conjunction with the fifth aspect above, in one possible implementation, the communication unit is further configured to send first indication information to the target access network device, so that the target access network device forwards at least one of the first AMF's identifier, registration request message, and second slice information to the first AMF according to the first indication information.

[0060] In conjunction with the fifth aspect above, in one possible implementation, the communication unit is further configured to send third indication information to the first AMF; the third indication information includes at least one of the following: a registration request message, a SUPI of the terminal pole device, the context of the terminal device, and second slice information.

[0061] In conjunction with the fifth aspect above, in one possible implementation, the communication unit is further configured to send a fifth indication message to the target access network device, the fifth indication message being used to indicate at least one of the PLMN list and the mobility restriction list.

[0062] A sixth aspect provides a communication device applied in a communication system, the communication system comprising: a terminal device, a source access network device, a source access and mobility management function (AMF), a target AMF, and a target access network device; the source access network device and the source AMF belong to a first public land mobile network (PLMN); the target AMF belongs to a second PLMN network; the source AMF and the target AMF are connected via a communication interface; the device comprises: a communication unit and a processing unit; the processing unit is used to determine the frequency point information of the target access network device, and the communication unit is used to send the frequency point information to the terminal device; the frequency point information of the target access network device is used to instruct the terminal device to access the target access network device according to the frequency point information, and to send a redirection request to the terminal device through the target access network device.

[0063] In conjunction with the sixth aspect above, in one possible implementation, the processing unit is further configured to: determine the target PLMN identifier ID; the target PLMN ID is the PLMN ID that the terminal device needs to select when accessing the second PLMN network; and determine the frequency information of the PLMN network corresponding to the target PLMN ID as the frequency information of the target access network device.

[0064] In conjunction with the sixth aspect above, in one possible implementation, the communication unit is further configured to receive a list of PLMNs from the source AMF; the list of PLMNs includes at least one of the following: the HPLMN of the terminal device, the serving PLMN, the Equivalent Public Land Mobile Network (EPLMN), and the previously selected PLMN; the processing unit is further configured to determine the target PLMN from the list of PLMNs.

[0065] In conjunction with the sixth aspect above, in one possible implementation, the processing unit is further configured to: determine the current serving PLMN ID of the terminal device based on the PLMN list; determine the home network of the terminal device based on the serving PLMN ID of the terminal device; determine the PLMN ID of the home network of the terminal device in the second PLMN network as the first PLMN ID; and determine the first PLMN ID as the target PLMN ID.

[0066] In conjunction with the sixth aspect above, in one possible implementation, the communication unit is further configured to receive a mobility restriction list from the source AMF; the mobility restriction list is used to indicate a first PLMN ID; the first PLMN ID is the PLMN ID of the terminal device's home network in the second PLMN network; the processing unit is further configured to determine that the first PLMN ID indicated by the mobility restriction list is the target PLMN ID.

[0067] In conjunction with the sixth aspect above, in one possible implementation, the processing unit is further configured to: determine the access network device adjacent to the source access network device in the second PLMN network as the target access network device; and determine the frequency point information of the target access network device.

[0068] A seventh aspect provides a communication apparatus for use in a communication system, the communication system comprising: a terminal device, a source access network device, a source access and mobility management function (AMF), a target AMF, and a target access network device; the source access network device and the source AMF belong to a first public land mobile network (PLMN); the target AMF belongs to a second PLMN; the source AMF and the target AMF are connected via a communication interface; the apparatus comprises: a communication unit and a processing unit; the processing unit is configured to instruct the communication unit to receive a session information request message from the target AMF; wherein the source AMF is an AMF determined by the target AMF based on a first GUTI of the terminal device; the processing unit is further configured to instruct the communication unit to send session information of the terminal device to the target AMF in response to the session request message.

[0069] In conjunction with the seventh aspect above, in one possible implementation, the apparatus further includes: a processing unit, further configured to instruct the communication unit to send a PLMN list to the source access network equipment; the PLMN list includes at least one of the following: the HPLMN of the terminal equipment, the serving PLMN, the Equivalent Public Land Mobile Network (EPLMN), and the previously selected PLMN.

[0070] In conjunction with the seventh aspect above, in one possible implementation, the processing unit is further configured to instruct the communication unit to send a mobility restriction list to the source access network device; the mobility restriction list is used to indicate a first PLMN ID; the first PLMN ID is the PLMN ID of the terminal device's home network in the second PLMN network.

[0071] In conjunction with the seventh aspect above, in one possible implementation, the processing unit is further configured to: determine the location information of the terminal device; determine that the PLMN network adjacent to the first PLMN network at the location represented by the location information of the terminal device is the second PLMN network; determine the PLMN ID in the second PLMN network that allows the terminal device to access the network; and determine the PLMN ID that allows the terminal device to access the network as the first PLMN ID.

[0072] In conjunction with the seventh aspect above, in one possible implementation, the apparatus further includes: a processing unit, which is further configured to instruct the communication unit to send first slice indication information to the target AMF; the first slice indication information is used to indicate first slice information, which is the slice information of the terminal device in its home network.

[0073] In conjunction with the seventh aspect above, in one possible implementation, the processing unit is further configured to: determine the first slice information when the PLMN IDs of the source AMF and the target AMF are different; and generate a first slice indication message based on the first slice information. In conjunction with the seventh aspect above, in one possible implementation, the first indication information is specifically used to indicate at least one of the slice information of the terminal device in the first PLMN network and the slice information of the mapped terminal device in the home network in the first network.

[0074] In conjunction with the seventh aspect above, in one possible implementation, the processing unit is further configured to: instruct the communication unit to receive a registration status update message from the target AMF; the registration status update message is used to instruct the source AMF to release a preset session; the preset session is a session established in the source AMF for the terminal device that is not supported by the target AMF; and release the preset session in response to the registration status update message.

[0075] Eighthly, this application provides a communication device comprising: a processor and a communication interface; the communication interface and the processor are coupled, the processor being configured to execute computer programs or instructions to implement the communication method as described in the first aspect and any possible implementation thereof.

[0076] Ninthly, this application provides a communication device comprising: a processor and a communication interface; the communication interface and the processor are coupled, the processor being configured to execute computer programs or instructions to implement the communication method as described in the second aspect and any possible implementation thereof.

[0077] In a tenth aspect, this application provides a communication device comprising: a processor and a communication interface; the communication interface and the processor are coupled, the processor being configured to execute computer programs or instructions to implement the communication method as described in the third aspect and any possible implementation thereof.

[0078] Eleventhly, this application provides a computer-readable storage medium storing instructions that, when executed by a processor of a communication device, enable the communication device to perform the communication method as described in the first aspect and any possible implementation thereof.

[0079] In a twelfth aspect, this application provides a computer-readable storage medium storing instructions that, when executed by a processor of a communication device, enable the communication device to perform the communication method as described in the second aspect and any possible implementation thereof.

[0080] In a thirteenth aspect, this application provides a computer-readable storage medium storing instructions that, when executed by a processor of a communication device, enable the communication device to perform the communication method as described in the third aspect and any possible implementation thereof.

[0081] In this application, the names of the aforementioned communication devices do not limit the devices or functional modules themselves. In actual implementation, these devices or functional modules may appear under other names. As long as the functions of each device or functional module are similar to those of this invention, they fall within the scope of the claims of this invention and their equivalents.

[0082] These or other aspects of the invention will become more apparent from the following description.

[0083] The technical solution provided in this application brings at least the following beneficial effects: In the communication system provided in this application, source AMFs and target AMFs of different operators communicate through a communication interface (exemplarily, the communication interface can be an N14+ interface). When a terminal device redirects from a first PLMN network to a second PLMN network, the source access network device indicates the frequency point of the target access network device to the terminal device by discovering the frequency point of the target access network device, so that the terminal device can access the target access network device according to the frequency point information. The target AMF discovers the source AMF based on the terminal device's GUTI and obtains the terminal device's session information from the source AMF. In this way, the target AMF can create a session for the terminal device in the second PLMN network according to the terminal device's session information, thereby enabling the terminal device to redirect to the second PLMN network. This realizes the redirection of connected terminal devices between networks of multiple operators. Attached Figure Description

[0084] Figure 1 A system architecture diagram of an MOCN system provided in this application embodiment; Figure 2 A system architecture diagram of a communication system provided in this application embodiment; Figure 3 This application provides a schematic diagram illustrating a scenario where multiple operators share an access network and a core network. Figure 4 A system architecture diagram of another communication system provided in the embodiments of this application; Figure 5 A flowchart illustrating a communication method provided in an embodiment of this application; Figure 6 A flowchart illustrating a redirection method for a terminal device moving from a first region to a second region, provided in an embodiment of this application; Figure 7 A flowchart illustrating a redirection method for a terminal device moving from a second region to a first region, provided in an embodiment of this application; Figure 8 A flowchart illustrating a redirection method for a terminal device moving from a second region to a third region, provided in an embodiment of this application; Figure 9 This is a schematic diagram of the structure of a communication device provided in an embodiment of this application; Figure 10 This is a schematic diagram of the structure of another communication device provided in the embodiments of this application; Figure 11 This is a schematic diagram of another communication device provided in an embodiment of this application. Detailed Implementation

[0085] The communication system, method, apparatus, and storage medium provided in the embodiments of this application will now be described in detail with reference to the accompanying drawings.

[0086] In this article, the term "and / or" is merely a description of the relationship between related objects, indicating that there can be three relationships. For example, A and / or B can represent three situations: A exists alone, A and B exist simultaneously, and B exists alone.

[0087] The terms "first" and "second," etc., used in the specification and drawings of this application are used to distinguish different objects or to distinguish different treatments of the same object, rather than to describe a specific order of objects.

[0088] Furthermore, the terms "comprising" and "having," and any variations thereof, used in the description of this application are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or units is not limited to the steps or units listed, but may optionally include other steps or units not listed, or may optionally include other steps or units inherent to such process, method, product, or apparatus.

[0089] It should be noted that in the embodiments of this application, the words "exemplary" or "for example" are used to indicate examples, illustrations, or explanations. Any embodiment or design scheme described as "exemplary" or "for example" in the embodiments of this application should not be construed as being more preferred or advantageous than other embodiments or design schemes. Specifically, the use of the words "exemplary" or "for example" is intended to present the relevant concepts in a specific manner.

[0090] In the description of this application, unless otherwise stated, "a plurality of" means two or more.

[0091] The following explanations of the terms used in the embodiments of this application are provided to facilitate the reader's understanding.

[0092] 1. Shared network system of multi-operator core network (MOCN).

[0093] Currently, with the development of 5G networks, network coverage is becoming denser, the number of base stations is constantly increasing, and the network construction costs for operators are also rising. To reduce these costs, a network sharing method has been proposed, in which multiple operators share the same network, thereby reducing redundant construction of communication networks, saving overall network investment, and alleviating the enormous costs associated with network construction.

[0094] The 3GPP Release 16 specification defines a shared network architecture supporting 5G MOCN. This architecture allows terminal devices to share 5G access networks (RANs) from different operators. The MOCN network architecture is as follows: Figure 1 As shown.

[0095] like Figure 1 As shown, the MOCN system 10 includes core network equipment 101 of operator A, core network equipment 102 of operator B, core network equipment 103 of operator C, core network equipment 104 of operator X, and access network equipment 105 of operator X.

[0096] Among them, the access network equipment 105 of operator X is connected to the core network equipment 101 of operator A, the core network equipment 102 of operator B, and the core network equipment 103 of operator C through the N2 and N3 interfaces respectively.

[0097] The access network equipment 105 of operator X is used to access the terminal equipment of operator A, operator B and operator C, and forward the data of the terminal equipment to the core network equipment of the corresponding operator.

[0098] In the MOCN system 10, only operator X builds the access network. Terminal devices of other operators can access the corresponding core network devices by accessing operator X's access network device 105 within the coverage area of ​​operator X's access network device 105, thereby completing the communication service for the terminal devices.

[0099] 2. The method by which access network devices broadcast the public land mobile network (PLMN) identifier (ID) in the current MOCN shared network system.

[0100] In the current MOCN system, access network devices sharing a network will carry the PLMN ID of the core network of each operator sharing the access network device in the broadcast system message.

[0101] For example, when operators A and X share an access network using the MOCN (Multi-access Networking Network), the access network equipment in the shared network carries the PLMN IDs of operators A and X respectively in its broadcast system information. Each PLMN ID corresponds to an operator's core network.

[0102] After receiving the broadcast system message, the terminal device parses the message to determine the PLMN ID carried within. Based on the PLMN ID, the terminal device identifies the core network to which the access network device in the shared network connects and selects the PLMN ID of the network to which the terminal device belongs. The terminal device then notifies the access network device in the shared network of the selected PLMN ID. Upon receiving the PLMN ID selected by the terminal device, the access network device in the shared network routes the terminal device's service data to the core network selected by the terminal device.

[0103] One example, combined Figure 1 When operators X, A, B, and C share the access network of operator X, the PLMN selection (or reselection) process for the terminal equipment of operators X, A, B, and C is shown in Table 1 below: Table 1. PLMN IDs carried in system messages broadcast by access network devices in the shared network under MOCN sharing mode, along with the PLMN selection and message routing for terminal devices from various operators:

[0104] It should be noted that in practical applications, in addition to carrying the core network identifiers PLMN-ID (A), PLMN-ID (B), and PLMN-ID (C) of Operator A and Operator C in their broadcast system messages, Operator X's access network equipment also carries the core network identifier PLMN-ID (X) of Operator X. Since Operator X's access network equipment carrying PLMN-ID (X) in its broadcast system messages is a conventional broadcast method, rather than a shared network broadcast method, therefore... Figure 1 The cases where network sharing is performed by terminal equipment of operator X are not shown in Table 1.

[0105] In one example, when operators A and X share a network using the MOCN method, the access network built by operator A carries operator B's PLMN ID in the broadcast system messages, enabling operator B's terminal equipment to access operator A's access network; at the same time, the system messages also carry operator A's PLMN ID so that operator A's terminal equipment can also access operator A's access network.

[0106] Similarly, the access network built by operator X carries operator A's PLMN ID in the broadcast system messages, enabling operator A's terminal equipment to access operator X's access network; at the same time, the system messages also carry operator X's PLMN ID so that operator X's terminal equipment can also access operator X's access network.

[0107] In MOCN sharing mode, terminal devices need to select the core network based on the PLMN ID broadcast by the access network equipment of the shared network. Therefore, the number of PLMN IDs broadcast by the access network equipment of the shared network needs to be the same as the number of 5G core network devices sharing the access network. Thus, the access network equipment of the shared network must broadcast multiple PLMN IDs to ensure that all terminal devices can access the access network.

[0108] When N operators share access, the maximum number of shared operators carried in the system messages broadcast by the access network equipment of the shared access network is N-1. N is a positive integer.

[0109] Furthermore, in MOCN sharing mode, the PLMN ID broadcast by the shared access network is the same as the PLMN ID of each sharing operator. This minimizes the latency for terminal devices when selecting a PLMN (the specific latency is determined by the selection order of the terminal device's PLMN ID) and the terminal device's network selection and camping time. This method is particularly effective during terminal device power-on, cell selection after recovery from a non-covered cell, and cell reselection by idle terminal devices, where the latency required for PLMN selection and network camping is minimized.

[0110] The advantages of using the MOCN shared access network include at least the following: Under the MOCN shared access network architecture, the core networks of different operators are set up completely independently, providing better support for 5G special services such as network slicing and edge computing.

[0111] The terms used in the embodiments of this application have been explained above.

[0112] Figure 2 The communication system 20 provided in the embodiments of this application, such as Figure 2 As shown, the communication system provided in this application embodiment includes: a first access network device 201, a first core network device 202, at least one second core network device 203, and a terminal device 204.

[0113] The first access network device 201 is used to implement the functions of a wireless access network and provide wireless access services to terminal devices. The first access network device 201 is the access network equipment of the contractor operator. For example, it could be the access network equipment of operator X.

[0114] The first core network equipment 202 is the core network equipment of the contractor operator. For example, the core network equipment of operator X.

[0115] For the terminal equipment of the contractor operator, the first core network equipment 202 is used to implement core network-related functions and provide core network-related business services.

[0116] For terminal equipment of shared operators, the first core network device 202 provides data routing functions, routing the terminal equipment's service data to the terminal equipment's home core network. At this time, the first core network device 202 can also perform access control, policy control, network selection, and billing settlement for the terminal equipment.

[0117] The second core network device 203 is the core network device of the sharing operator, used by the sharing operator's terminal equipment to implement core network-related functions. For example, it provides data processing or forwarding functions.

[0118] exist Figure 2 The following example illustrates the concept of a second core network device 203 that includes core network device 2031 of operator A, core network device 2032 of operator B, and core network device 2033 of operator C.

[0119] Among them, the core network equipment 2031 of operator A is used to provide core network-related service to the terminal equipment of operator A; the core network equipment 2032 of operator B is used to provide core network-related service to the terminal equipment of operator B; and the core network equipment 2033 of operator C is used to provide core network-related service to the terminal equipment of operator C.

[0120] Terminal device 204 is a device that needs to provide communication services, and may belong to the same operator as the first access network device 201 and the first core network device 202. Terminal device 204 may also belong to the same operator as any one of the at least one second core network device 203. This application mainly uses the example of a terminal device belonging to the same operator as any one of the at least one second core network device 203 for illustration.

[0121] It should be noted that the core network equipment in this application embodiment mainly refers to 5G core network equipment.

[0122] The above is about Figure 2 The various devices in the communication system 20 shown are briefly described.

[0123] Figure 3 This is a schematic diagram illustrating a scenario where multiple operators share an access network and a core network, as provided in an embodiment of this application. Figure 3As shown, the coverage scenario includes core network equipment 301 of operator A, core network equipment 302 of operator X, core network equipment 303 of operator Y, access network equipment 304 of operator A, access network equipment 305 of operator X, access network equipment 306 of operator Y, and terminal equipment 307.

[0124] In this embodiment of the application, the terminal device is mainly described as belonging to operator A.

[0125] Among them, operators A, X, and Y can share access networks and core networks. In this way, when terminal devices can move within the coverage area of ​​access network equipment 304 of operator A, access network equipment 305 of operator X, and access network equipment 306 of operator Y, they can access the corresponding operator's access network equipment and core network equipment to provide network communication services.

[0126] Among them, the access network equipment 304 of operator A is connected to the core network equipment 301 of operator A through the N1 / N2 / N3 interface.

[0127] The access network equipment 305 of operator X is connected to the core network equipment 302 of operator X through the N1 / N2 / N3 interface; the core network equipment 302 of operator X is connected to the core network equipment 301 of operator A through the N9 / N16 / N8 / N12 / N24 / N32 / N14+ interface.

[0128] Operator Y's access network equipment 306 is connected to Operator Y's core network equipment 303 through the N1 / N2 / N3 interfaces; Operator Y's core network equipment 303 is connected to Operator A's core network equipment 301 through the N9 / N16 / N8 / N12 / N24 / N32 / N14+ interfaces.

[0129] The coverage area of ​​access network equipment 304 of operator A is designated as the first area; the coverage area of ​​access network equipment 305 of operator X is designated as the second area; and the coverage area of ​​access network equipment 306 of operator Y is designated as the third area.

[0130] When the terminal device 307 moves to the first area, it can access the access network device 304 of operator A and access the core network device 301 of operator A through the access network device 304 of operator A.

[0131] When the terminal device moves to the second area, it can access the access network device 305 of operator X, access the core network device 302 of operator X through the access network device 305 of operator X, and access the core network device 301 of operator A through the core network device 302 of operator X.

[0132] When the terminal device moves to the third area, it can access the access network device 306 of operator Y, access the core network device 303 of operator Y through the access network device 306 of operator Y, and access the core network device 301 of operator A through the core network device 303 of operator Y.

[0133] The application scenarios of the embodiments of this application have been described above.

[0134] It should be pointed out that, in Figure 2 and Figure 3 In the communication system shown, terminal equipment, access network equipment, and core network equipment all need to perform corresponding actions and implement corresponding functions to enable the connected terminal equipment to redirect between the networks of multiple operators.

[0135] Specifically, this includes: Scenario 1, the process of access network equipment broadcasting PLMN ID; Scenario 2, the process of access network equipment selecting target PLMN ID and the frequency of target access network equipment; Scenario 3, the interconnection and interaction between access network equipment and core network equipment of different operators.

[0136] The following sections will explain scenarios 1 through 3 respectively: Scenario 1: The process of an access network device broadcasting its PLMN ID.

[0137] In order to notify terminal devices of the PLMN network supported by the access network device, the access network device needs to broadcast the PLMN ID to the terminal devices. The access network device can use any one of the following schemes (1 to 3) to broadcast the PLMN ID. Schemes 1, 2, and 3 are explained below: Option 1: The access network device broadcasts the original PLMN ID of each core network connected to it. The PLMN ID of each core network is the same as the PLMN ID broadcast for that core network within its own operator's network. In other words, in Option 1, the access network device broadcasts the PLMN ID of each core network using the MOCN broadcasting method in related technologies.

[0138] One example, combined Figure 2 When the access network equipment of operator X broadcasts the PLMN ID, it broadcasts the PLMN ID (A) of the core network of operator A, the PLMN ID (B) of the core network of operator B, and the PLMN ID (C) of the core network of operator C.

[0139] Using Scheme 1 to broadcast the PLMN ID offers at least the following advantages: When a terminal device obtains the PLMN ID, the latency required to select a PLMN (e.g., during power-on or when disconnecting from the network after recovery from a coverage area) is minimized. Furthermore, in Scheme 1, the access network device broadcasts the PLMN ID of each core network using the MOCN broadcasting method found in related technologies, eliminating the need to create new network numbers and preventing waste of network number resources.

[0140] In Scheme 1, the maximum number of shared operator core network PLMN IDs that the access network device can broadcast is N-1. N is the maximum number of broadcast PLMN IDs that the access network device can support, and N is a positive integer.

[0141] Option 2: The access network device broadcasts a new PLMN ID for each core network connected to it. The new PLMN ID for each core network is different from the PLMN ID broadcast for that core network within its own operator's network. For example, the access network device can merge the PLMN ID of the contractor operator with the PLMN ID of the sharing operator to obtain the PLMN ID for each core network.

[0142] One example, combined Figure 2 When the access network equipment of operator X broadcasts the PLMN ID, it broadcasts the PLMN ID (XA) of the core network of operator A, the PLMN ID (XB) of the core network of operator B, and the PLMN ID (XC) of the core network of operator C.

[0143] Adopting Scheme 2 to broadcast the PLMN ID offers at least the following benefits: Access network devices can customize the broadcast of new PLMN IDs. Upon receiving this new PLMN ID, the terminal device can determine that the access network is a shared access network built by Operator X. Furthermore, the terminal device can simultaneously display the network identifiers of both the building operator and the sharing operator on its display interface based on the new PLMN ID.

[0144] In Scheme 2, the maximum number of shared operator core network PLMN IDs that the access network device can broadcast is N-1.

[0145] Option 3: The access network device broadcasts the same PLMN ID to each core network connected to the access network device.

[0146] One example, combined Figure 2 The access network device only broadcasts the PLMN ID of operator X's core network. Alternatively, the access network device only broadcasts the new PLMN ID (XY) of operator X's core network.

[0147] Adopting Scheme 3, which broadcasts the PLMN ID, offers at least the following advantages: Access network devices only need to broadcast one PLMN ID, reducing signaling overhead. When the access network device only broadcasts the PLMN ID of operator X's core network, there is no waste of network number resources. In Scheme 3, since the access network device does not broadcast the PLMN IDs of various operators, it is necessary to add the function of allowing the first core network device to determine the home network of the terminal device without relying on the PLMN ID selected by the terminal device. For example, this could be extended to allow the first core network device to identify the terminal device's Subscription Permanent Identifier (SUPI) or HPLMN. Correspondingly, the terminal device also needs to have the function of reporting the SUPI or HPLMN.

[0148] One example is combining the above-mentioned schemes 1, 2, and 3, and... Figure 2 The method by which operator X's access network equipment broadcasts the PLMN ID is shown in Table 2 below: Table 2. Methods by which operator X's access network equipment broadcasts the PLMN ID

[0149] In one possible implementation, the access network device broadcasts the PLMN ID by broadcasting a first system message, which carries the PLMN ID that the terminal device needs to broadcast.

[0150] The above provides a detailed explanation of how access network devices broadcast PLMN IDs in Scenario 1.

[0151] The following describes the process of selecting the target PLMN ID and the frequency of the target access network device in scenario 2.

[0152] Scenario 2: The process of the source access network device selecting the target PLMN ID and the frequency of the target access network device.

[0153] In scenario 2, the source access network device can determine the frequency of the target access network device using method 1; and determine the target PLMN ID using either method 2 or method 5. These are explained below: Method 1: The source access network device configures the frequency of the target access network device based on the PLMN ID.

[0154] Specifically, let's take the access network equipment of operator A as an example to illustrate this.

[0155] Method 1.1: For the source access network equipment of operator A, when the source access network equipment is a base station at the boundary between the first and second areas: The source access network equipment determines the PLMN ID used by the terminal equipment to access operator X as PLMN-ID(XA) in scheme 2 (or it can be the PLMN ID in other schemes). The source access network equipment determines the frequency (or frequency point) F2 of the access network equipment of its neighboring operator X. At this time, the source access network equipment determines the target PLMN ID as PLMN-ID(XA) and the frequency of the target access network equipment as F2.

[0156] When the source access network device is a base station at the boundary between the first and third areas, the source access network device determines the PLMN ID used by the terminal device to access operator Y as PLMN-ID(YA) in scheme 2 (or it could be a PLMN ID from another scheme). The source access network device determines the frequency (or frequency point) F3 of the access network device of its neighboring operator Y. At this time, the source access network device determines the target PLMN ID as PLMN-ID(YA) and the frequency of the target access network device as F3.

[0157] Method 1.2: For the source access network equipment of operator X, when the source access network equipment is a base station at the boundary between the second area and the first area: The source access network equipment determines the PLMN ID used by the terminal equipment to access operator A as PLMN-ID(A). The source access network equipment determines the frequency (or frequency point) F1 of the adjacent operator A access network equipment. At this time, the source access network equipment determines the target PLMN ID as PLMN-ID(A), and the frequency of the target access network equipment as F1.

[0158] When the source access network device is a base station at the boundary between the second and third areas, the source access network device determines the PLMN ID used by the terminal device to access operator Y as PLMN-ID(YA) in scheme 2 (or it could be a PLMN ID from another scheme). The source access network device determines the frequency (or frequency point) F3 of the access network device of its neighboring operator Y. At this time, the source access network device determines the target PLMN ID as PLMN-ID(YA) and the frequency of the target access network device as F3.

[0159] Method 1.3: For the source access network equipment of operator Y, when the source access network equipment is a base station at the boundary between the third region and the first region: The source access network equipment determines the PLMN ID used by the terminal equipment to access operator A as PLMN-ID(A). The source access network equipment determines the frequency (or frequency point) F1 of the access network equipment of its neighboring operator A. At this time, the source access network equipment determines the target PLMN ID as PLMN-ID(A) and the frequency of the target access network equipment as F1.

[0160] When the source access network device is a base station at the boundary between the third and second regions, the source access network device determines the PLMN ID used by the terminal device to access operator X as PLMN-ID(XA) in scheme 2 (or it could be a PLMN ID from another scheme). The source access network device determines the frequency (or frequency point) F2 of the access network device of operator X adjacent to it. At this time, the source access network device determines the target PLMN ID as PLMN-ID(XA) and the frequency of the target access network device as F2.

[0161] Method 2: During the terminal device redirection process, the source access network device can select the target PLMN ID based on the PLMN ID currently served by the terminal device and indicate it to the Access and Mobility Management Function (AMF).

[0162] The source access network device can indicate the selected target PLMN ID and the cell under the target PLMN ID to the source AMF.

[0163] The source AMF can select the target AMF / Mobility Management Entity (MME) based on the TAI information provided by the source access network device (this application mainly uses the target AMF as an example for illustration). Then, the source AMF sends the selected target PLMN ID to the target AMF / MME.

[0164] Specifically, the source access network device can determine the current serving PLMN ID of the terminal device, and determine the home network of the terminal device based on the serving PLMN ID of the terminal device; the terminal device determines the PLMN ID of the home network of the terminal device in the second PLMN network as the first PLMN ID, and the terminal device determines the first PLMN ID as the target PLMN ID.

[0165] In one example, when a terminal device of operator A moves from a second area to a first area, it determines that the currently serving PLMN ID is PLMN ID(XA) (i.e., the access network device broadcasts the PLMN ID using scheme 2). At this time, the source access network device determines that the terminal device's home network is operator A's network based on the currently serving PLMN ID (XA). Within operator A's network, operator A's PLMN ID is PLMN ID(A). The source access network device then determines PLMN ID(A) as the target PLMN ID.

[0166] In another example, operator X's access network equipment broadcasts a PLMN ID (XA) to operator A's terminal equipment. When operator A's terminal equipment moves from a second area to a first area, operator X's access network equipment can determine the terminal equipment's home network as PLMN ID (A) based on the terminal equipment's current serving PLMN ID (XA). At this time, operator X's access network equipment determines the target PLMN ID as PLMN ID (A) based on the current serving PLMN ID (XA). Operator X's access network equipment then indicates the target PLMN ID as PLMN ID (A) to operator X's AMF.

[0167] The above is merely an illustrative example; the various implementation methods for the process of a terminal device moving between other areas will not be elaborated upon further.

[0168] Method 3: The source access network device determines the target PLMN ID based on the PLMN list issued by the source AMF (referred to as Method 3.1), or determines the target PLMN ID based on the mobility restriction list issued by the source AMF (referred to as Method 3.2). Methods 3.1 and 3.2 are explained below: Method 3.1: The source access network device determines the target PLMN ID based on the PLMN list issued by the source AMF.

[0169] Specifically, the source AMF determines the PLMN auxiliary information of the terminal device; the PLMN auxiliary information includes at least one of the following: the serving PLMN ID of the terminal device, the SUPI number range of the terminal device, and the location information of the terminal device; the source AMF determines the first PLMN ID based on the PLMN auxiliary information of the terminal device, and generates the PLMN list based on the first PLMN ID. The source AMF sends the PLMN list to the source access network device. The source access network device determines the target PLMN ID based on the PLMN list.

[0170] Alternatively, the source AMF can determine the PLMN list of the terminal device based on information such as the terminal device's HPLMN, serving PLMN, EPLMN, and last PLMN.

[0171] The PLMN list includes a first PLMN ID; the first PLMN ID is the PLMN ID of the terminal device's home network in the second PLMN network.

[0172] In one example, when a terminal device of operator A moves from a second area to a first area, it determines that the currently serving PLMN ID is PLMN ID(XX) (i.e., the access network device broadcasts the PLMN ID using scheme 3). At this time, the source access network device determines the home network information of the terminal device as operator A's network based on the terminal device's SUPI number segment. In operator A's network, operator A's PLMN ID is PLMN ID(A), and the source AMF determines the first PLMN ID as PLMN ID(A). The PLMN list includes PLMN ID(A). The source AMF sends the PLMN list to the source access network device. The source access network device determines the target PLMN ID as PLMN ID(A) based on the PLMN list.

[0173] In another example, after a terminal device from operator A connects to the access network equipment and AMF of operator X, operator X's AMF will send a PLMN list to the terminal device based on at least one of the following: the terminal device's serving PLMN ID, the terminal device's number range, and the terminal device's location information. When the terminal device is located at the boundary between the first and second regions, operator X's AMF sends an EPLMN list containing the PLMN ID (A). When the terminal device is located at the boundary between the second and third regions, operator X's AMF sends an EPLMN list containing the PLMN ID (YA).

[0174] The above is merely an illustrative example; the various implementation methods for the process of a terminal device moving between other areas will not be elaborated upon further.

[0175] Method 3.2: The source AMF determines the target PLMN ID based on the mobility restriction list issued by the source AMF.

[0176] The location information of the terminal device is determined, and the PLMN network adjacent to the first PLMN network at the location represented by the location information of the terminal device is determined to be the second PLMN network. The source AMF determines the PLMN ID in the second PLMN network that allows the terminal device to access the network; the source AMF determines the PLMN ID that allows the terminal device to access the network as the first PLMN ID. The source AMF sends a mobility restriction list to the source access network device; the source access network device determines that the first PLMN ID indicated by the mobility restriction list is the target PLMN ID.

[0177] The mobility restriction list is used to indicate a first PLMN ID; the first PLMN ID is the PLMN ID of the terminal device's home network in the second PLMN network; In one example, as a terminal device of operator A moves from a second area to a first area, the source AMF determines that the neighboring network of operator X at the current location is operator A's network. The PLMN ID allowed for the terminal device's access in operator A's network is PLMN ID(A). The source AMF determines PLMN ID(A) as the first PLMN ID and indicates PLMN ID(A) to the source access network device via a mobility restriction list. The source access network device determines PLMN ID(A) as the target PLMN ID. In another example, operator X's AMF issues a mobility restriction list to operator A's terminal device, instructing the terminal device to preferentially select the 5G NR access technology of PLMN ID(A) and PLMN ID(YA). The AMF can issue the mobility restriction list based on the TA. When the terminal device is at the boundary between the first and second areas, it is instructed to preferentially select the 5G NR access technology of PLMN ID(A). At the boundary between the second and third areas, it is instructed to preferentially select the 5G NR access technology of PLMN ID(YA).

[0178] The above is merely an illustrative example; the various implementation methods for the process of a terminal device moving between other areas will not be elaborated upon further.

[0179] Method 4: The source access network device selects the target PLMN ID based on the current service PLMN ID of the terminal device and the EPLMN issued by the source AMF.

[0180] For example, when the access network equipment of operator X broadcasts the same PLMN ID as PLMNID(XX) to the terminal equipment of operator A (e.g., the above scheme 3), when the terminal equipment of operator A moves from the second area to the first area, the access network equipment of operator X can indicate the target PLMN ID as PLMNID(A) to the AMF of operator X based on the current service PLMN ID(XX) of the terminal equipment and the PLMN list issued by the source AMF.

[0181] The specific implementation of method 4 can be referred to method 3.1 above, and will not be repeated here.

[0182] The above is merely an illustrative example; the various implementation methods for the process of a terminal device moving between other areas will not be elaborated upon further.

[0183] Method 5: The source access network device selects the target PLMN ID based on the terminal device's current serving PLMN ID and the mobility restriction list issued by the source AMF.

[0184] In one example, when operator X's shared access network equipment broadcasts the same PLMN ID as PLMN ID (XX) to operator A's terminal equipment, and operator A's terminal equipment moves from the second area to the first area, operator X's access network equipment can indicate to operator X's AMF that the target PLMN's PLMN ID is PLMN ID (A) based on the terminal equipment's current serving PLMN ID (XA) and the mobility restriction list issued by the serving AMF.

[0185] The specific implementation of method 5 can be referred to method 3.2 above, and will not be repeated here.

[0186] The above is merely an illustrative example; the various implementation methods for the process of a terminal device moving between other areas will not be elaborated upon further.

[0187] Scenario 3: Interconnection and interaction between access network equipment and core network equipment of different operators.

[0188] In scenario 3, the interconnection and interaction between access network equipment and core network equipment of different operators includes the following situations 1-3.

[0189] Scenario 1: Access network equipment and core network equipment from different operators support redirection parameters in connection state.

[0190] Specifically, this includes: Case 1.1, where the target access network device can select the target AMF based on the target PLMN ID selected by the terminal device when it accesses the network, the location information of the terminal device (e.g., TAI in the source access network device), and the NSSAI requested by the terminal device.

[0191] Scenario 1.2: The target AMF can discover the source AMF based on the source PLMN ID of the terminal device and the GUTI (specifically 5G-GUTI) assigned to the terminal device by the source PLMN network. The signaling during the target AMF's discovery of the source AMF can be forwarded through a secure signaling gateway.

[0192] Scenario 2: AMF quality inspection from different operators supports interfaces and parameters for connection-state redirection.

[0193] Specifically, this includes: Case 2.1, where operators sharing the core network support the interconnection interface N14+, which can be isolated through a security signaling gateway.

[0194] Scenario 2.2: The target AMF can obtain the terminal device's SUPI and terminal device context from the source AMF via the N14+ interface. The target AMF can create a context for the terminal device based on the obtained SUPI and terminal device context, and then notify the source AMF of the result.

[0195] Scenario 2.3: The target AMF obtains access and mobility data, context information, and SMF information of the terminal devices from the source AMF via the N14+ interface across the PLMN. This eliminates the need for the target AMF to obtain the terminal devices' subscription data from the UDM, ensuring the continuity of the terminal devices' IP addresses and services, optimizing the process, and reducing the burden on the UDM.

[0196] Scenario 2.4: Access network equipment can use 5G-GUTI to indicate changes in the PLMN ID of the serving PLMN to terminal equipment.

[0197] Case 3: The source access network device, source AMF, source SMF, source UPF, target access network device, target AMF, target SMF, target UPF and other network elements can support the redirection signaling process under the core network shared architecture in the connection state.

[0198] The above, in conjunction with scenarios 1 and 3, provides a detailed description of the corresponding actions and functions that the terminal equipment, access network equipment, and core network equipment need to perform in the communication system of this application.

[0199] Figure 4 This is a schematic diagram of the structure of another communication system 40 provided in an embodiment of this application. For example... Figure 4 As shown, the communication system provided in this application embodiment includes: a terminal device 401, a source access network device 402, a source access and mobility management function (AMF) 403, a target AMF 404, and a target access network device 405; the source access network device 402 and the source AMF 403 belong to a first public land mobile network (PLMN); the target AMF 404 belongs to a second PLMN network; the source AMF 403 and the target AMF 404 are connected through a communication interface; the source access network device 402 is used to determine the frequency point information of the target access network device 405 and send the frequency point information to the terminal device 401; the terminal device 401 is used to determine the target access network based on the frequency point information. Device 405 initiates a redirection request to target access network device 405; the redirection request includes the first globally unique temporary identifier (GUTI) of terminal device 401; the first GUTI is the GUTI of terminal device 401 in the first PLMN network; target access network device 405 is used to forward the redirection request to target AMF 404; target AMF 404 is used to determine the first GUTI of terminal device 401, determine the source AMF 403 based on the first GUTI, and send a session information request message to the source AMF 403; source AMF 403 is used to respond to the session request message and send the session information of terminal device 401 to target AMF 404.

[0200] The above technical solution brings at least the following beneficial effects: In the communication system provided in this application, source AMFs and target AMFs of different operators communicate through a communication interface (exemplarily, the communication interface can be an N14+ interface). When a terminal device redirects from a first PLMN network to a second PLMN network, the source access network device indicates the frequency point of the target access network device to the terminal device by discovering the frequency point of the target access network device, so that the terminal device can access the target access network device according to the frequency point information. The target AMF discovers the source AMF based on the terminal device's GUTI and obtains the terminal device's session information from the source AMF. In this way, the target AMF can create a session for the terminal device in the second PLMN network according to the terminal device's session information, thereby enabling the terminal device to redirect to the second PLMN network. This realizes the redirection of connected terminal devices between networks of multiple operators.

[0201] In one possible implementation, the source access network device 402 is specifically used to: determine the target PLMN identifier ID; the target PLMN ID is the PLMN ID that the terminal device 401 needs to select when accessing the second PLMN network; and determine the frequency information of the PLMN network corresponding to the target PLMN ID as the frequency information of the target access network device 405.

[0202] In one possible implementation, the target AMF404 is further configured to send a first request message to the source AMF403; the first request message is configured to request the context information and user permanent identifier SUPI of the terminal device 401; the source AMF403 is configured to send a first response message to the target AMF404 according to the first request message; the first response message includes the context information and SUPI of the terminal device 401; the target AMF404 is further configured to determine the terminal device 401 according to the SUPI, and create a context for the terminal device 401 according to the context information.

[0203] In one possible implementation, the target AMF404 is specifically used to: parse the first GUTI, determine the globally unique AMF identifier GUAMI in the first GUTI, and determine that the AMF represented by GUAMI is the source AMF403.

[0204] In one possible implementation, the source AMF 403 is further configured to send a PLMN list to the source access network device 402; the PLMN list includes at least one of the following: the HPLMN of the terminal device 401, the serving PLMN, the Equivalent Public Land Mobile Network (EPLMN), and the previously selected PLMN; the source access network device 402 is further configured to determine the target PLMN from the PLMN list.

[0205] In one possible implementation, the source access network device 402 is specifically configured to: determine the current serving PLMN ID of the terminal device 401 based on the PLMN list; determine the home network of the terminal device 401 based on the serving PLMN ID of the terminal device 401; determine the PLMN ID of the home network of the terminal device 401 in the second PLMN network as the first PLMN ID; and determine the first PLMN ID as the target PLMN ID.

[0206] In one possible implementation, the source AMF403 is further configured to send a mobility restriction list to the source access network device 402; the mobility restriction list is used to indicate a first PLMN ID; the first PLMN ID is the PLMN ID of the home network of the terminal device 401 in the second PLMN network; the source access network device 402 is configured to receive the mobility restriction list and determine that the first PLMN ID indicated by the mobility restriction list is the target PLMN ID.

[0207] In one possible implementation, the source AMF403 is specifically used for: determining the location information of the terminal device 401; determining that the PLMN network adjacent to the first PLMN network at the location represented by the location information of the terminal device 401 is the second PLMN network; determining the PLMN ID in the second PLMN network that allows the terminal device 401 to access the network; and determining the PLMN ID that allows the terminal device 401 to access the network as the first PLMN ID.

[0208] In one possible implementation, the source access network device 402 is further configured to: determine the access network device adjacent to the source access network device 402 in the second PLMN network as the target access network device 405; and determine the frequency point information of the target access network device 405.

[0209] In one possible implementation, the target access network device 405 is further configured to: obtain the target PLMN ID, the location information of the terminal device 401, and the slice information requested by the terminal device 401; and determine the target AMF 404 based on the target PLMN ID, the location information of the terminal device 401, and the slice information requested by the terminal device 401.

[0210] In one possible implementation, the source AMF403 is also used to send first slice indication information to the target AMF404; the first slice indication information is used to indicate first slice information, which is the slice information of the terminal device 401 in the home network.

[0211] In one possible implementation, the source AMF403 is specifically used to: determine the first slice information when the PLMNID of the source AMF403 and the target AMF404 are different; and generate a first slice indication message based on the first slice information. In one possible implementation, the first indication information is specifically used to indicate at least one of the slice information of terminal device 401 in the first PLMN network and the slice information of terminal device 401 mapped in the first network in the home network; the target AMF404 is specifically used to: determine the slice information of terminal device 401 in the first PLMN network as the first slice information when the first PLMN network is the home network; and determine the slice information of terminal device 401 mapped in the first network in the home network as the first slice information when the first PLMN network is not the home network.

[0212] In one possible implementation, the target AMF404 is further configured to: determine first slice information; determine second slice information mapped by the first slice information in the second PLMN network; and determine a target session management function (SMF) based on at least one of the second slice information and the location information of the terminal device 401; the target SMF is the SMF in the second PLMN network.

[0213] In one possible implementation, the target AMF404 is further configured to send a registration status update message to the source AMF403; the registration status update message is used to instruct the source AMF403 to release a preset session; the preset session is a session established in the source AMF403 for the terminal device 401 that is not supported by the target AMF404; the source AMF403 is further configured to release the preset session in response to the registration status update message.

[0214] In one possible implementation, the system further includes: a home unified data management function UDM406; a target AMF404, which is also used to send a context request message to the home UDM406; the context request message is used to request the subscription data of the terminal device 401 from the UDM406; the UDM406 is used to respond to the context request message and send the subscription data of the terminal device 401 to the target AMF404. The target AMF404 is also used to obtain the subscription data of the terminal device 401 from the source AMF403 through a communication interface.

[0215] In one possible implementation, the system further includes: a target network slice selection function NSSF408; and a target AMF404, which is also used to query the target NSSF408 based on the first slice information to determine the second slice information and the AMF list that supports the second slice information.

[0216] In one possible implementation, the target AMF404 is further configured to query the slice mapping relationship configured in the target AMF404 based on the first slice information, determine the second slice information, and the AMF list that supports the second slice information.

[0217] In one possible implementation, the system further includes: a first AMF; a target AMF404, which is further configured to: determine whether the target AMF404 is included in the AMF list; the first AMF is an AMF in the AMF list; if not included, the first AMF is determined based on the AMF list.

[0218] In one possible implementation, the target AMF 404 is further configured to send first indication information to the target access network device 405, the first indication information including at least one of the following: the identifier of the first AMF, a registration request message, and second slice information; the target access network device 405 is configured to generate second indication information based on the first indication information and send the second indication information to the first AMF; the second indication information includes at least one of the following: the identifier of the first AMF, a registration request message, and second slice information; the first AMF is configured to determine at least one of the identifier of the first AMF, the registration request message, and the second slice information based on the second indication information.

[0219] In one possible implementation, the target AMF404 is further configured to send third indication information to the first AMF; the third indication information includes at least one of the following: a registration request message, a SUPI of the terminal pole device, a context of the terminal device 401, and second slice information; the first AMF is configured to determine at least one of the registration request message, the SUPI of the terminal pole device, the context of the terminal device 401, and the second slice information based on the third indication information.

[0220] In one possible implementation, the system further includes: a home SMF407 and a home policy control function PCF408; the home SMF407 is also used to send a fourth indication information to the home PCF408; the fourth indication information is used to indicate SM policy management; and to indicate the location information of the terminal device 401 to the home PCF408.

[0221] In one possible implementation, the target AMF404 is also used to send a fifth indication message to the target access network device 405, the fifth indication message being used to indicate at least one of the PLMN list and the mobility restriction list.

[0222] The above describes the interaction process of various network elements in a communication system provided by the embodiments of this application. Furthermore, the embodiments of this application also provide a communication method for implementing redirection of a connected terminal device between networks of multiple operators.

[0223] like Figure 5 As shown in the illustration, this application also provides a communication method that can be applied to... Figures 2-4 In any communication system. For example... Figure 5 As shown, the method includes: S501, The source access network device determines the frequency point information of the target access network device.

[0224] In one possible implementation, the source access network device determines the target PLMN identifier ID; the target PLMN ID is the PLMN ID that the terminal device needs to select when accessing the second PLMN network; the source access network device determines the frequency information of the PLMN network corresponding to the target PLMN ID as the frequency information of the target access network device.

[0225] It should be noted that the process by which the source access network device determines the frequency information of the target access network device can be understood by referring to the process by which the source access network device selects the target PLMN ID and the frequency of the target access network device in Scenario 2 above, and will not be repeated here.

[0226] S502. The source access network device sends frequency point information to the terminal device. Correspondingly, the terminal device receives the frequency point information from the source access network device.

[0227] S503: The terminal equipment determines the target access network equipment based on the frequency point information.

[0228] In one possible implementation, the terminal device searches for signals sent by various access network devices and selects the access network device whose signal frequency information is the same as the aforementioned frequency information as the target access network device.

[0229] S504. The terminal device initiates a redirection request to the target access network device. Correspondingly, the target access network device receives the redirection request from the terminal device.

[0230] The redirection request includes the terminal device's first GUTI; the first GUTI is the terminal device's GUTI in the first PLMN network.

[0231] Optionally, the redirection request is a Mobility Registration Update (Registration Request) sent by the terminal device to the target access network device. The Registration Request carries the 5G-GUTI assigned to the terminal device by the first PLMN network, the TAI of the terminal device in the first PLMN network, the list of PDU sessions that the terminal device needs to activate, and the NSSAI requested by the terminal device.

[0232] S505. The target access network device forwards the redirection request to the target AMF. Correspondingly, the target AMF receives the redirection request from the target access network device.

[0233] In one possible implementation, the target access network device selects a target AMF based on the PLMN ID (i.e., the aforementioned target PLMN ID) selected by the terminal device when accessing the target access network device, the TAI (Target Access Identity) of the terminal device in the first PLMN network, and the NSSAI (Non-Standard Access Identity) requested by the terminal device. After selecting the target AMF, the aforementioned redirection request is forwarded to the target AMF.

[0234] S506. The target AMF determines the source AMF based on the redirection request.

[0235] In one possible implementation, the target AMF parses the redirection request and determines the first GUTI carried in the redirection request. The target AMF parses the first GUTI and determines a globally unique AMF identifier GUAMI in the first GUTI; the target AMF determines that the AMF represented by the GUAMI is the source AMF.

[0236] S507. The target AMF sends a session information request message to the source AMF. Correspondingly, the source AMF receives the session information request message from the target AMF.

[0237] Optionally, the above session request message is: Namf_Communication_UEContextTransferRequest. This message carries the NAS message "complete Registration Request".

[0238] The session request message is used to request the SUPI (i.e., IMSI) and context information of the terminal device from the source AMF. The context information of the terminal device includes: the AUSF, PCF, and UDM information of the terminal device in the home network, the access and mobility context of the terminal device, the context of each PDU session of the terminal device, the AllowedNSSAI of the terminal device in the HPLMMN, and the corresponding HPLMMN.

[0239] S508, the source AMF sends the terminal device's session information to the target AMF.

[0240] Optionally, the above session request message is: Namf_Communication_UEContextTransferResponse. This message carries SUPI, UE Context, SMF information, DNN(s), source NSSAI(s), and PDU Session ID(s).

[0241] After receiving the session information, the target AMF creates a context for the terminal device in the second PLMN network based on the session information.

[0242] It should be noted that in the above process, the source AMF needs to indicate the terminal device's slice information in its home network (denoted as the first slice information) to the target AMF, so that the target AMF can map the terminal device's slice information in the second PLMN network (denoted as the second slice information) based on the first slice information. The source AMF and the target AMF can indicate the first slice information and determine the second slice information in the following detailed manner: Method 1: The source AMF adds a new information cell message to the session request message to indicate the first slice information.

[0243] When the source AMF sends a Namf_Communication_CreateUEContext message to the target AMF, it determines whether the PLMN IDs of the source AMF and the target AMF are the same. If they are different, a first cell message (e.g., allowedHomeNssai) is added to the Namf_Communication_CreateUEContext to indicate the first slice information. After receiving the Namf_Communication_CreateUEContext, the target AMF parses and obtains the first cell message, and determines the first slice information based on the first cell message.

[0244] For example, the first information cell message is carried in UeContex target > MmContext -> allowedHomeNssai.

[0245] Method 2: The source AMF indicates the first slice information based on the original information cells in the session request message, and the target AMF determines the first slice information by parsing different information cells from the session request message according to the different mobile scenarios of the terminal device.

[0246] Specifically, the session request message is used to indicate at least one of the following: the slice information of the terminal device in the first PLMN network, and the slice information of the terminal device mapped in the first network in its home network.

[0247] The target AMF parses the session request message to determine the first slice information based on the different mobile scenarios of the terminal device.

[0248] When the target AMF is the home network of the first PLMN network, it determines the slice information of the terminal device in the first PLMN network as the first slice information.

[0249] In one example, the source AMF passes the slice information to the target AMF via UeContextTransferRspData->UeContex target>MmContex target>allowedNssai in Namf_Communication_CreateUEContext, and the target AMF treats allowedNssai as the first slice information.

[0250] If the first PLMN network is not the home network, the target AMF determines the slice information of the terminal device mapped in the first network in the home network as the first slice information.

[0251] In one example, the source AMF passes the slice information to the target AMF via UeContextTransferRspData->UeContex target>MmContex target>nssaiMappingLis target>hNssai in Namf_Communication_CreateUEContext, and the target AMF regards hNssai as the first slice information.

[0252] The above technical solution brings at least the following beneficial effects: In the communication system provided in this application, source AMFs and target AMFs of different operators communicate through a communication interface (exemplarily, the communication interface can be an N14+ interface). When a terminal device redirects from a first PLMN network to a second PLMN network, the source access network device indicates the frequency point of the target access network device to the terminal device by discovering the frequency point of the target access network device, so that the terminal device can access the target access network device according to the frequency point information. The target AMF discovers the source AMF based on the terminal device's GUTI and obtains the terminal device's session information from the source AMF. In this way, the target AMF can create a session for the terminal device in the second PLMN network according to the terminal device's session information, thereby enabling the terminal device to redirect to the second PLMN network. This realizes the redirection of connected terminal devices between networks of multiple operators.

[0253] The communication method provided in the embodiments of this application has been described in detail above.

[0254] It should be noted that the communication method provided in this application has different redirection procedures in different scenarios. For example, in conjunction with the above... Figure 3 The mobile scenarios of the terminal device in this application include the following scenarios 4-6. Scenario 4: The terminal device moves from the first area to the second area; Scenario 5: The terminal device moves from the second area to the first area; Scenario 6: The terminal device moves from the second area to the third area.

[0255] The redirection process in the communication method provided in this application embodiment will be described below with reference to scenarios 4-6 above: Scenario 4: The terminal device moves from the first area to the second area. like Figure 6 As shown, when a terminal device moves from the first area to the second area, the redirection process for the terminal device includes the following steps: S601, The source access network device sends a context release request to the source AMF.

[0256] Optionally, UE Context Release Request, cause=redirection, instructs the source AMF of operator A to release the terminal device context because a redirection has occurred, carrying a list of PDU sessions activated by the terminal device.

[0257] While initiating the terminal device context release process to the source AMF, the source access network device sends an AN Connectiong Release message to the terminal device, indicating the redirection frequency point to the terminal, namely the NR frequency F2 of operator X (the NG-RAN and 5GC selection function for target PLMN-ID and frequency described in Part 1 above).

[0258] S602, The source access network device performs context release.

[0259] Specifically, this includes: S602a, the source AMF from operator A being sent to the source access network equipment: UE Context ReleaseCommand S602b, Source access network device replies to source AMF: UE Context Release Complete. S603. The terminal device sends a mobility registration update request to the target access network device.

[0260] Optionally, the mobility registration update request is a Registration Request. The Mobility Registration Update Request carries the 5G-GUTI assigned to the terminal device by operator A, the TAI of operator A, the list of PDU sessions to be activated, and the requested NSSAI (this NSSAI is the NSSAI of the terminal device in the source PLMN network and cannot be used for AMF selection and SMF selection in the target network).

[0261] S604. Select the target AMF for the target access network equipment.

[0262] In one specific implementation, the target access network device selects the target AMF based on the PLMN-ID, TAI, and requested NSSAI selected by the terminal device.

[0263] S605. The target access network device forwards the mobility registration update request to the target AMF.

[0264] S606, Target AMF discovers source AMF.

[0265] In one possible implementation, the target AMF discovers the source AMF based on the 5G-GUTI assigned by operator A to the terminal device. The 5G-GUTI includes the source AMF's GUAMI. The target AMF then discovers the source AMF based on the GUAMI.

[0266] Specifically, this includes S606a, where the target AMF sends a Namf_Communication_UEContextTransferRequest to the source AMF.

[0267] The Namf_Communication_UEContextTransfer Request carries the NAS message `completeRegistration Request`. The target AMF obtains the terminal device's SUPI (i.e., IMSI) and context from the source AMF. The context includes the terminal device's AUSF, PCF, and UDM information in its home network, its access and mobility context, the context of each PDU session, and the Allowed NSSAI and corresponding HPLMN in the HPLMN. It should be noted that the Namf_Communication_UEContextTransfer Request carries the PLMN ID selected by the terminal device when accessing the target access network device (i.e., the requested PLMN). The target PLMN is the PLMN ID carried in the terminal device's GUAMI.

[0268] S606b: The source AMF sends Namf_Communication_UEContextTransferResponse to the target AMF.

[0269] The Namf_Communication_UEContextTransfer Response carries SUPI, UE Context, SMF information, DNN(s), source NSSAI(s), and PDU Session ID(s).

[0270] After receiving the context of the terminal device from the source AMF, the target AMF creates a context for the terminal device.

[0271] It should be noted that in S603, the target AMF needs to map slice resources in the target network for the terminal device based on the slice resources of the terminal device in the home network. Specific methods can be found in Methods 1 and 2 of S508 above, and will not be elaborated here.

[0272] S607, a security process is performed between the terminal equipment and the home AUSF.

[0273] S608, The target AMF sends a registration status update message to the source AMF.

[0274] Optionally, the registration status update message is: Namf_Communication_RegistrationStatusUpdate. This message carries the PDU Session ID(s). The target AMF uses this message to notify the source AMF that the terminal device's registration with the target AMF is complete. For slices and sessions that the target AMF cannot support (depending on network capabilities and network sharing protocols), the target AMF notifies the source AMF in this message, and the source AMF initiates the release process for the unsupported sessions. The message's transferStatus is set to "Transferred" and carries a list of PDU Session IDs transferred to the target AMF.

[0275] S609, Target AMF discovers and assigns to UDM.

[0276] Optionally, the target AMF discovers the home UDM through an inter-network security signaling gateway based on SUPI.

[0277] S610, the target AMF obtains the context information of the terminal device.

[0278] Specifically, this includes: S610a, the target AMF sending a context registration message to the home UDM.

[0279] Optionally, the context registration message is: Nudm_UECM_Registration. The target AMF uses this procedure to register itself with the home UDM, and the home UDM sends a response.

[0280] S610b: The target AMF sends Nudm_SDM_Get to the home UDM. Through this message, the target AMF obtains the terminal device's subscription data from the home UDM, including access and mobility data, SMF selection migration data, and the terminal device's context data within the SMF. The UDM then replies with a response message.

[0281] The target AMF obtains the terminal device's access and mobility data, terminal device context information, SMF information, etc. from the source AMF through the N14+ interface across the PLMN, without needing to obtain the terminal device's subscription data from the UDM.

[0282] On the one hand, it provides continuity of IP addresses and services; on the other hand, it optimizes processes and reduces the pressure on UDM.

[0283] S610c, The target AMF sends the following to the home UDM: Nudm_UECM_Subscribe. The vAMF uses this procedure to subscribe to the home UDM's notifications, and the home UDM replies with a response.

[0284] S610d, the home UDM sends a Nudm_UECM_DeregistrationNotification to the source AMF. According to step 10a), the target AMF has registered with the home UDM, and the home UDM notifies the source AMF to deregister. The source AMF sets a relevant timer, and after the timer expires, deletes the terminal device's context information.

[0285] S610e, the source AMF sends the following to the home UDM: Nudm_SDM_unsubscribe, to unsubscribe from the home UDM notification message.

[0286] S611, Target AMF detects Target SMF.

[0287] Optionally, the target AMF initiates the target SMF (shared SMF) discovery process. The target AMF can discover the target SMF using the location information and slice information of the terminal device.

[0288] Specifically, this includes: S611a, obtaining the slice information of the target AMF mapping.

[0289] Specifically, this includes situations A and B, which will be explained in detail below.

[0290] Scenario A: The target AMF determines the mapped slice information by querying the target NSSF.

[0291] Specifically, the target AMF queries the target NSSF based on the allowedHomeNssai obtained from S606, and obtains the mapped NSSAI, including Allowed NSSAI, Configed NSSAI, mapped Allowed NSSAI, Mapped Configed NSSAI, etc., as well as the AMF SET that supports the above mapped NSSAI.

[0292] Scenario B: The target AMF determines the mapped slice information by querying the local configuration.

[0293] Specifically, the target AMF obtains the mapped slice and the AMFSET that supports the mapped slice based on the target AMF's local configuration.

[0294] S611b If the current target AMF cannot support the mapped slice, reselect the target AMF.

[0295] Specifically, if the target AMF is not a NF in the AMF SET returned by NSSF, or if the target AMF's local configuration cannot support the mapped slice, the target AMF determines that AMF reselection is required, and sends the slice information to the reselected AMF after reselection.

[0296] The methods for a target AMF to send slice information to a reselected target AMF include the following cases C and D, which are described in detail below.

[0297] Scenario C: The target AMF sends slice information to the reselected target AMF through the target access network device.

[0298] Specifically, this includes: (1) The initial target AMF forwards NAS messages to the target target AMF through the RAN. The initial target AMF sends a Reroute NAS message to the target access network device. The message contains the target AMF, Registration Request message, Allowed NSSAI, Configured NSSAI, mapped Allowed NSSAI, Mapped Configured NSSAI, and other slice information.

[0299] (2) The target access network device sends an Initial UE message to the target AMF, which contains slice information obtained from the initial target AMF.

[0300] Case D: The target AMF directly sends slice information to the reselected target AMF.

[0301] Specifically, this includes: the initial target AMF forwarding NAS messages directly to the target target AMF; the initial target AMF sending Namf_Communication_N1MessageNotify messages directly to the target target AMF, carrying Registration Request messages, the terminal device's SUPI, the terminal device's MM Context, slice mapping information, etc.

[0302] S612. The target AMF sends a PDU session context creation request to the target SMF.

[0303] Optionally, the PDU session context creation request is: Nsmf_PDUSession_CreateSMContextRequest.

[0304] The PDU session context creation request includes at least one of the following: PDU Session ID and SMContext ID obtained from S606, UE location info, Access Type, RAT Type, and Operation Type, where the SMContext ID points to the source SMF and the target AMF sets the Operation Type to "UP activate", indicating that an N3 tunnel for the user plane is established for PDU Session(s).

[0305] S613. The target SMF determines the PDU session context.

[0306] Specifically, this includes: S613a, the target SMF sends the following to the source SMF: Nsmf_PDUSession_Context Request (SMcontext type, SM Context ID). The target SMF uses the SM Context ID received from the target AMF in this step to obtain all the SM Contexts from the source SMF, including the PDN Connection Context and the 5G SM context.

[0307] S613b: The source SMF determines the PDU session context information of the terminal device based on the SM Context ID and replies to the target SMF.

[0308] S614, Target SMF selects target UPF.

[0309] S615. The target SMF initiates the N4 session establishment process from the target UPF.

[0310] S616. The target SMF sends a PDU session creation request to the source SMF.

[0311] Optionally, the PDU session creation request is: Nsmf_PDUSession_Create Request. The PDU session context creation request includes at least one of the following: target UPF DL tunnel information, target SMF's SM ContextID, Access Type, and RAT type.

[0312] Specifically, the target SMF initiates a session establishment process to the source SMF, carrying the N9 tunnel information allocated by the target UPF.

[0313] S617, Source SMF performs N4 session modification.

[0314] Specifically, this includes: S617a, the SM policy management process initiated by the source SMF to the PCF, which notifies the PCF of the location information of the terminal device.

[0315] S617b: The source SMF initiates an N4 session modification process to the source UPF. The source SMF provides the target UPF with N9 tunnel information, and the source UPF allocates N9 tunnel resources.

[0316] S618. The source SMF sends a PDU session creation response to the target SMF.

[0317] Optionally, the PDU session creation response is: Nsmf_PDUSession_Create Response. The PDU session creation response includes the N9 tunnel information of the source UPF received from S617.

[0318] A downlink data channel is established from the source UPF to the target UPF.

[0319] S619. The target SMF sends a PDU session context creation response to the target AMF.

[0320] Optionally, the PDU session creation response is: Nsmf_PDUSession_CreateSMContext Response. The PDU session creation response includes at least one of the following: N2 SM information (PDU Session ID, QFI(s), QoSprofile(s), CN N3 Tunnel Info, Source NSSAI), N1 SM Container, Cause).

[0321] Among them, CN N3 Tunnel Info refers to the uplink tunnel information of the target UPF.

[0322] S620, the target AMF sends an initial context request to the target access network device.

[0323] Optionally, the initial context request is: Initial Context Request. The initial context request includes at least one of the following: NAS message Registration Accept, N2 SMinformation received from the target SMF in S619, and the mobility restriction list, frequency priority, and equivalent PLMN list for assisting the terminal device in selecting PLMN-ID.

[0324] The target access network device allocates RAN tunnels and QoS resources for PDU sessions.

[0325] Uplink data channels are established from the terminal device to the target UPF and then to the source UPF.

[0326] It should be noted that in S620, the target AMF sends mapped slice information to the terminal device and sends a PLMN list or mobility restriction list to both the terminal device and the target access network device. The mapped slice information includes: mappedAllowed NSSAI and MappedConfiged NSSAI.

[0327] S621, The terminal device sends a registration completion message to the target AMF.

[0328] Optionally, the registration completion message is: Registration Complete. Registration Complete is a NAS message.

[0329] Specifically, the terminal device replies with a NAS message RegistrationComplete to the target AMF through the target access network device.

[0330] S622, The target AMF sends a PDU session context update request to the target SMF.

[0331] Optionally, the PDU session context update request is: Nsmf_PDUSession_UpdateSMContextRequest. The PDU session context update request includes at least one of the following: N2 SM information, RAT type, Access type, and N2 SM information received by the target AMF from step 17.

[0332] S623, Target SMF performs N4 session modification.

[0333] Specifically, the target SMF initiates an N4 session modification procedure to the target UPF. In this session modification procedure, the target SMF sends AN Tunnel information to the target UPF, and a downlink channel is established from the target UPF to the target access network device to the terminal device.

[0334] S624. The target SMF performs a PDU session context update.

[0335] Specifically, this includes: S624a, the target SMF sends an Nsmf_PDUSession_Update request (RATtype, Access type) to the source SMF, and the source SMF updates the PDU Session.

[0336] S624b, Source SMF responds to target SMF: Nsmf_PDUSession_Update Response.

[0337] The target SMF replies to the target AMF: Nsmf_PDUSession_UpdateSMContext Response.

[0338] S625. The target SMF sends a PDU session context update response to the target AMF.

[0339] Optionally, the PDU session context update response is: Nsmf_PDUSession_UpdateSMContextResponse.

[0340] The above provides a detailed explanation of the redirection process for terminal devices in scenario 4, when the terminal device moves from the first area to the second area.

[0341] It should be noted that the scenario described above, in which the terminal device moves from the first area to the second area, is merely an illustrative example. The above process is applicable to various scenarios where the terminal device moves from its home network to a shared network (e.g., from the first area to the third area), and the implementation process is similar in other scenarios. This application does not limit the scope of the application.

[0342] The following is a detailed explanation of the redirection process of the terminal device when it moves from the second area to the first area in scenario 5.

[0343] Scenario 5: The terminal device moves from the second area to the first area.

[0344] like Figure 7 As shown, when a terminal device moves from the second area to the first area, the redirection process for the terminal device includes the following steps: S701. The source access network device sends a context release request to the source AMF and performs context release.

[0345] Specifically, this includes: S701a, the source access network device sending a context release request to the source AMF.

[0346] Optionally, UE Context Release Request, cause=redirection, instructs the source AMF of operator A to release the terminal device context because a redirection has occurred, carrying a list of PDU sessions activated by the terminal device.

[0347] When the source access network device initiates the terminal device context release process to the source AMF, it sends an AN Connectiong Release message to the terminal device, indicating the redirection frequency point to the terminal, namely the NR frequency F1 of operator A.

[0348] S701b, Source AMF sends UE Context Release Command to source access network equipment.

[0349] S701c, Source Access Network Equipment replies to Source AMF: UE Context Release Complete.

[0350] S702, The terminal device sends a mobility registration update request to the target access network device.

[0351] Optionally, the mobility registration update request is a Registration Request. The Mobility Registration Update Request carries the 5G-GUTI assigned to the terminal device by the source AMF of operator X (or operator Y), the TAI of operator X (or Y), the list of PDU sessions to be activated, and the requested NSSAI.

[0352] The target access network device forwards the terminal device's mobility registration update request to the target AMF.

[0353] S703, Select the target AMF for the target access network equipment.

[0354] S704. The target access network device forwards the mobility registration update request to the target AMF.

[0355] In S704, the mobility registration update request carries Registration Type: mobilityregistration updating, 5G-GUTI, UE security capability, NAS message container, N2message (Location Information (tai tac), Cell Identity and Establishment cause).

[0356] S705, Target AMF discovers source AMF.

[0357] In one possible implementation, the target AMF discovers the source AMF based on the 5G-GUTI assigned to the terminal device by the source AMF of operator X (or Y). The 5G-GUTI includes the GUAMI of the source AMF. The target AMF then discovers the source AMF based on the GUAMI.

[0358] S706, The target AMF obtains the context information of the terminal device.

[0359] Specifically, this includes: S706a, the target AMF sending a context request message to the source AMF.

[0360] Optionally, the context request message is: Namf_Communication_UEContextTransfer Request. The context request message carries the NAS message "complete Registration Request". The target AMF obtains the terminal device's SUPI (i.e., IMSI) and the terminal device's context from the source AMF. For cross-PLMN mobility procedures, the UE context includes the Allowed NSSAI in the HPLMN and the corresponding HPLMN.

[0361] S706b: The source AMF sends a context response message to the target AMF.

[0362] Optionally, the context response message is: Namf_Communication_UEContextTransferResponse. The context response message carries SUPI, UE Context, SMF information, DNN(s), source NSSAI(s), and PDUSSession ID(s).

[0363] After receiving the context of the terminal device from the source AMF, the target AMF creates a context for the terminal device.

[0364] S707, terminal equipment and home AUSF conduct security procedures. S708, The target AMF sends a registration status update message to the source AMF.

[0365] Optionally, the registration status update message is: Namf_Communication_RegistrationStatusUpdate. This message carries the PDU Session ID(s). The target AMF uses this message to notify the source AMF that the terminal device's registration with the target AMF is complete. For slices and sessions that the target AMF cannot support (depending on network capabilities and network source protocols), the target AMF notifies the source AMF in this message, and the source AMF initiates the release process for the unsupported sessions. The message contains `transferStatus: "Transferred"`, carrying a list of PDU Session IDs transferred to the target AMF. The target AMF determines that the terminal device has returned to its home network and instructs the removal of the source SMF and UPF in the message.

[0366] S709, Target AMF discovers and assigns to UDM.

[0367] Optionally, the target AMF discovers the home UDM through an inter-network security signaling gateway based on SUPI.

[0368] S710, the target AMF obtains the context information of the terminal device.

[0369] Specifically, this includes: S710a, the target AMF sending a context registration message to the home UDM.

[0370] Optionally, the context registration message is: Nudm_UECM_Registration. The target AMF uses this procedure to register itself with the home UDM, and the home UDM sends a response.

[0371] S710b, the target AMF obtains the contract data via Nudm_SDM_Get (optional step).

[0372] Through this message, v-AMF obtains the terminal device's subscription data from hUDM, including access and mobility data, SMF migration selection data, and the terminal device's context data in the SMF, etc., and UDM replies with a response message.

[0373] The target AMF obtains the terminal device's access and mobility data, terminal device context information, SMF information, etc. from the source AMF through the N14 interface across the PLMN, without needing to obtain the terminal device's subscription data from the UDM.

[0374] On the one hand, it provides continuity of IP addresses and services; on the other hand, it optimizes processes and reduces the pressure on UDM.

[0375] S710c, the target AMF subscribes to the data change notification service via Nudm_SDM_Subscribe.

[0376] S710d: The home UDM sends Nudm_UECM_DeregistrationNotify to the source AMF. According to S710a: The target AMF has registered with the home UDM, and the home UDM notifies the source AMF to deregister. The source AMF sets a relevant timer, and after the timer expires, deletes the terminal device's context information.

[0377] S711, The target AMF sends a PDU session creation request to the target SMF.

[0378] Optionally, the session creation request is: Nsmf_PDUSession_CreateSMContext. The session creation request includes: SUPI, DNN, source NSSAI(s), Request Type, PDU Session ID, AMF ID, SM Context ID, and User location information.

[0379] The specific implementation steps of S711 can be referred to S611 above, and will not be repeated here.

[0380] S712, Home SMF request session context.

[0381] Specifically, this includes S712a, where the home SMF sends a session context request to the source SMF.

[0382] Optionally, the session context request is: Nsmf_PDUSession_Context Request. The session context request includes: SM context type (SM Context ID received in this step), and obtaining the SMContext from the source SMF.

[0383] S712b: The target SMF initiates the SM policy management process to the PCF, notifying the PCF of the location information of the terminal device.

[0384] S712c: The source SMF sends a session context reply response message to the target SMF.

[0385] Optionally, the session context response message is: Nsmf_PDUSession_Context Response. The session context response message is used to return the SM Context (PDU Session ID, DNN, sNssai, session AMBR, QoS Flow list, home UPF PSA tunnel info).

[0386] S713. The target SMF sends an N4 session modification request to the home UPF.

[0387] Optionally, the N4 Session Modification Request is an N4 Session Modification Request. The N4 Session Modification Request includes forwarding parameters. The Home UPF replies to the Home SMF with an N4 Session Modification Response, creating a CN TunnelInfo, the UP's TEID, and IP address.

[0388] S714. The target SMF sends a PDU session creation response to the target AMF.

[0389] Optionally, the session creation response is: Nsmf_PDUSession_CreateSMContext Response. The session creation response includes: PDU Session ID and N2 SM Information. Among them, N2 SM Information includes the N3 UP address, the uplink CN Tunnel ID and QoS parameters of the UPF, and the activation of the user plane connection of the PDU Session belonging to the SMF.

[0390] Downlink user plane establishment from the home UPF to the target access network device.

[0391] S715, the target AMF sends a registration acceptance message to the terminal device.

[0392] Optionally, the registration acceptance message is: Registration Accept. The registration acceptance message is used to notify the terminal device that its registration request has been accepted. The registration acceptance message includes the assigned 5G-GUTI, a mobility restriction list for assisted terminal device PLMN-ID selection, frequency priority, equivalent PLMN list, TAI list, Allowed NSSAI, Configured NSSAI, PDU Session status, etc. The EPLMN list sets PLMN-ID-A, PLMN-ID-XA, and PLMN-ID-YA as equivalent PLMNs.

[0393] The uplink user plane is established from the terminal device to the target access network device to the home UPF.

[0394] S716, The terminal device sends a registration completion message to the target AMF.

[0395] Optionally, the registration completion message is: Registration Complete.

[0396] S717, Source AMF initiates PDU session release process to source SMF.

[0397] Specifically, this includes: S717a, the source AMF sends Nsmf_PDUSession_ReleaseSMContextRequest to the source SMF, indicating that only the session resources of the source SMF are released.

[0398] S717b, Source SMF Response: Nsmf_PDUSession_ReleaseSMContext Response.

[0399] S718. The target AMF sends a PDU session context update request message to the target SMF.

[0400] Optionally, the PDU session context update request message is: Nsmf_PDUSession_UpdateSMContextRequest. The session update request message includes: PDU Session ID, N2 SM information, N2 SM information type, and UE Location.

[0401] S719, Target SMF initiates SM policy management process to PCF.

[0402] The SM policy management process is used to notify the PCF of the location information of the terminal device. The home SMF initiates an N4 Session modification request to the home UPF, updating the home network's RAN SM N3 forwarding Informationlist to the home UPF. The home UPF then replies to the home SMF with an N4 Session Modification Response. S720: The target SMF sends a PDU session context update response message to the target AMF.

[0403] Optionally, the PDU session context update response message is: Nsmf_PDUSession_UpdateSMContextResponse. The PDU session context update response includes: upCnxState: ACTIVATED, activating the user plane resources of the PDU Session.

[0404] S721. After the timer expires, the source SMF releases the resources of the source UPF.

[0405] The above provides a detailed explanation of the redirection process for terminal devices when they move from the second area to the first area in scenario 5.

[0406] It should be noted that the movement of the terminal device from the second area to the first area in scenario 5 above is merely an illustrative example. The above process is applicable to various scenarios where the terminal device moves from its home network to a shared network (e.g., the terminal device moves from the third area to the first area), and the implementation process is similar in other scenarios. This application does not limit the scope of the application.

[0407] The following is a detailed explanation of the redirection process of the terminal device when it moves from the second area to the third area in scenario 6.

[0408] Scenario 6: The terminal device moves from the second area to the third area.

[0409] like Figure 8 As shown, when a terminal device moves from the second area to the third area, the redirection process for the terminal device includes the following steps: S801, The source access network device sends a context release request to the source AMF.

[0410] Optionally, UE Context Release Request, cause=redirection, instructs the source AMF of operator A to release the terminal device context because a redirection has occurred, carrying a list of PDU sessions activated by the terminal device.

[0411] While initiating the terminal device context release process to the source AMF, the source access network device will send an AN Connectiong Release message to the terminal device, indicating the redirection frequency point to the terminal, namely the NR frequency F3 of operator Y.

[0412] S802, the source access network device performs context release.

[0413] Specifically, this includes: S802a, source AMF sending to source access network equipment: UE Context Release Command S802b, Source access network device replies to source AMF: UE Context Release Complete.

[0414] S803, The terminal device sends a mobility registration update request to the target access network device.

[0415] Optionally, the mobility registration update request is a Registration Request. The Mobility Registration Update Request carries the 5G-GUTI assigned to the terminal device by operator X, the terminal device's TAI at operator X, a list of PDU sessions to be activated, and the requested NSSAI.

[0416] S804, Select the target AMF for the target access network equipment.

[0417] In one specific implementation, the target access network device selects the target AMF based on the PLMN-ID, TAI, and requested NSSAI selected by the terminal device.

[0418] S805. The target access network device forwards the mobility registration update request to the target AMF.

[0419] S806, Target AMF discovers source AMF.

[0420] In one possible implementation, the target AMF discovers the source AMF based on the 5G-GUTI assigned by operator A to the terminal device. The 5G-GUTI includes the source AMF's GUAMI. The target AMF then discovers the source AMF based on the GUAMI.

[0421] Specifically, this includes S806a, where the target AMF sends a `Namf_Communication_UEContextTransferRequest` to the source AMF. The `Namf_Communication_UEContextTransferRequest` carries the NAS message `completeRegistration Request`. The target AMF obtains the terminal device's SUPI (i.e., IMSI) and context from the source AMF. The UE context includes the terminal device's AUSF, PCF, and UDM information in its home network, the terminal device's access and mobility context, the context of each PDU session, the Allowed NSSAI in the HPLMN, and the corresponding HPLMN.

[0422] S806b, Source AMF replies to Target AMF: Namf_Communication_UEContextTransferResponse. This message carries SUPI, UE Context, SMF information, DNN(s), Source NSSAI(s), and PDU Session ID(s).

[0423] After receiving the context of the terminal device from the source AMF, the target AMF creates a context for the terminal device.

[0424] S807, a security process is performed between the terminal equipment and the home AUSF.

[0425] S808, the target AMF sends a registration status update message to the source AMF.

[0426] Optionally, the registration status update message is: Namf_Communication_RegistrationStatusUpdate. This message carries the PDU Session ID(s). The target AMF notifies the source AMF via this message that the terminal device's registration with the target AMF is complete, carrying a list of PDU Session IDs transferred to the target AMF. For policies, slices, and sessions that the target AMF cannot support (depending on network capabilities and network sharing protocols), the target AMF notifies the source AMF in this message, and the source AMF initiates the release process for the unsupported sessions.

[0427] S809, Target AMF discovers and assigns to UDM.

[0428] Optionally, the target AMF discovers the home UDM through an inter-network security signaling gateway based on SUPI.

[0429] S810, the target AMF obtains the context information of the terminal device.

[0430] Optionally, the context registration message is: Nudm_UECM_Registration. The target AMF uses this procedure to register itself with the home UDM, and the home UDM sends a response.

[0431] S810b: The target AMF sends Nudm_SDM_Get to the home UDM. Through this message, the target AMF obtains the terminal device's subscription data from the home UDM, including access and mobility data, SMF selection migration data, and the terminal device's context data within the SMF. The UDM then replies with a response message.

[0432] The target AMF obtains the terminal device's access and mobility data, terminal device context information, SMF information, etc. from the source AMF through the N14+ interface across the PLMN, without needing to obtain the terminal device's subscription data from the UDM.

[0433] On the one hand, it provides continuity of IP addresses and services; on the other hand, it optimizes processes and reduces the pressure on UDM.

[0434] S810c, the target AMF sends the following to the home UDM: Nudm_UECM_Subscribe. The vAMF uses this procedure to subscribe to the home UDM's notifications, and the home UDM replies with a response.

[0435] S810d, the home UDM sends a Nudm_UECM_DeregistrationNotification to the source AMF. According to step 10a), the target AMF has registered with the home UDM, and the home UDM notifies the source AMF to deregister. The source AMF sets a relevant timer, and after the timer expires, deletes the terminal device's context information.

[0436] S810e, the source AMF sends the following to the home UDM: Nudm_SDM_unsubscribe, to unsubscribe from the home UDM notification message.

[0437] S811, Target AMF detects Target SMF.

[0438] Optionally, the target AMF initiates the target SMF (shared SMF) discovery process. The target AMF can discover the target SMF using the location information and slice information of the terminal device.

[0439] It should be noted that the specific implementation process of S811 can be referred to S611 above, and will not be repeated here.

[0440] S812, The target AMF sends a PDU session context creation request to the target SMF.

[0441] Optionally, the PDU session context creation request is: Nsmf_PDUSession_CreateSMContextRequest. The PDU session context creation request includes at least one of the following: PDU Session ID and SMContext ID obtained from S806, UE location info, Access Type, RAT Type, and Operation Type. The SMContext ID points to the home SMF, and the target AMF sets the Operation Type to "UP activate," indicating the establishment of an N3 tunnel for the user plane of the PDU Session(s).

[0442] S813, The target AMF determines the PDU session context.

[0443] Specifically, this includes: S813a, the target SMF sends to the source SMF: Nsmf_PDUSession_Context Request (SMcontext type, SM Context ID). The target SMF uses the SM Context ID received from the target AMF in this step to obtain all the SM contexts from the source SMF, including the PDN Connection Context and the 5G SM context.

[0444] S813b: The home SMF determines the PDU session context information of the terminal device based on the SM Context ID and replies to the sharing SMF.

[0445] S814, Target SMF selects target UPF S815, The target SMF initiates the N4 session establishment process from the target UPF.

[0446] S816, The target SMF creates a PDU session.

[0447] Specifically, this includes: S816a, the target SMF sending a PDU session creation request to the source SMF.

[0448] Optionally, the PDU session creation request is: Nsmf_PDUSession_Create Request. The PDU session context creation request includes at least one of the following: the SM Context ID obtained from the target AMF and the tunnel endpoints (f) for the downlink cached data that needs to be cached.

[0449] S816b: The source SMF sends N4 session modification information to the source UPF, transmitting the tunnel information for the downlink cached data allocated by the target SMF to the source UPF. This establishes a forwarding channel for the downlink cached data from the source UPF to the target UPF.

[0450] S816c, Source SMF responds to Target SMF: Nsmf_PDUSession_Update Response.

[0451] S817, The target SMF performs a PDU session update.

[0452] Specifically, this includes: S817a, the target SMF sends an Nsmf_PDUSession_Update Request (SMContext ID, downlink tunnel information of the target UPF, SM Context ID of the target SMF, Access Type, RATtype) to the home SMF, initiating a session establishment process from the shared SMF to the home SMF, carrying the N9 tunnel information allocated by the shared UPF. The SMContext ID is obtained from the source SMF in step 13.

[0453] S817b: The home SMF initiates an SM policy management process to the PCF to notify the PCF of the location information of the terminal device.

[0454] S817c: The home SMF initiates an N4 session modification to the home UPF, carrying downlink tunnel information of the target UPF, and the home UPF allocates CN N9 tunnel information.

[0455] S817d, The home SMF sends the following to the target SMF: Nsmf_PDUSession_Update Response.

[0456] Once the downlink data channel from the home UPF to the target UPF is established, the home UPF stops sending downlink buffered data to the source UPF and generates an END-MARKER to be sent to the source UPF and then sends it to the target UPF. Upon receiving the END-MARKER, the target UPF starts a timer; upon the timer expires, it releases the indirect forwarding channel.

[0457] S818, The target SMF sends a PDU session context creation response to the target AMF.

[0458] Optionally, the PDU session context creation response is: Nsmf_PDUSession_CreateSMContextResponse. The PDU session context creation response includes at least one of the following: N2 SM information (PDU SessionID, QFI(s), QoS profile(s), CN N3 Tunnel Info, source NSSAI), N1 SM Container, Cause). Among them, CN N3 Tunnel Info refers to the uplink tunnel information of the target UPF.

[0459] The target SMF sets a timer, and when the timer expires, it releases the indirect forwarding channel for downlink buffered data.

[0460] S819, The target AMF sends an initial context request to the target access network device.

[0461] Optionally, the initial context request is: Initial Context Request. The initial context request includes at least one of the following: carrying the NAS message Registration Accept, carrying the N2 SMinformation received from the target SMF in S818, and carrying the mobility restriction list, frequency priority, and equivalent PLMN list for the auxiliary terminal device to select PLMN-ID.

[0462] The wireless network allocates RAN tunnels and QoS resources to PDU sessions.

[0463] Uplink data channels are established from the terminal device to the target UPF and then to the home UPF.

[0464] S820, the terminal device sends a registration completion message to the target AMF.

[0465] Optionally, the registration completion message is: Registration Complete.

[0466] S821, Source AMF releases PDU session context.

[0467] Specifically, this includes: S821a, the source AMF sends a PDU session context release request to the source SMF.

[0468] Optionally, the PDU session context release request is: Nsmf_PDUSession_ReleaseSMContextRequest. The PDU session context release request is used to indicate that only the PDU session context of the source SMF should be released, and the PDU session context of the home SMF should not be released.

[0469] When the source AMF's timer expires, the terminal device context is deleted and session resources are released. The source SMF sets a timer, and upon expiration, the indirect forwarding channel resources of the source UPF are released.

[0470] S821b: The source SMF sends a PDU session context release response to the source AMF.

[0471] Optionally, the PDU session context release response is: Nsmf_PDUSession_ReleaseSMContextresponse S822, The target AMF sends a PDU session context update request to the target SMF.

[0472] Optionally, the PDU session context update request is: Nsmf_PDUSession_UpdateSMContextRequest. The PDU session context update request includes: N2 SM information, RAT type, Access type, and carries the N2 SM information received by the target AMF from the S820.

[0473] S823, Target SMF performs N4 session modification.

[0474] Specifically, the target SMF initiates an N4 session modification procedure to the target UPF. In this session modification procedure, the target SMF sends AN Tunnel information to the target UPF, and a downlink channel is established from the target UPF to the target access network device to the terminal device.

[0475] S824, The target SMF performs a PDU session context update.

[0476] Specifically, this includes: S824a, the target SMF sends an Nsmf_PDUSession_Update request (RAT type, Access type) to the home SMF, and the home SMF updates the PDU Session.

[0477] S824b, SMF response to V-SMF: Nsmf_PDUSession_Update Response.

[0478] S825, the shared SMF sends a PDU session context update response to the target AMF.

[0479] Optionally, the PDU session context update response is: Nsmf_PDUSession_UpdateSMContextResponse.

[0480] S826, Target SMF and Source SMF release indirect forwarding channels.

[0481] Specifically, this includes: S826a, after the timer in S817 expires, the target SMF initiates the N4 session modification process to the target UPF to release the indirect forwarding channel.

[0482] S826b: After the timer in S821 expires, the source SMF initiates the N4 session modification procedure to the source UPF to release the indirect forwarding channel.

[0483] The above provides a detailed explanation of the redirection process for terminal devices when they move from the second area to the third area in scenario 6.

[0484] It should be noted that the scenario described above, in which the terminal device moves from the second area to the third area, is merely illustrative. The above process is applicable to various scenarios where the terminal device moves from one shared network to another (e.g., from the third area to the second area), and the implementation process is similar in other scenarios. This application does not limit the scope of the application.

[0485] It should be noted that in scenarios 5 and 6, there are steps that are the same or similar to those in scenario 4. The understanding of the above-mentioned same or similar steps can be referred to the description in scenario 4 above, and this application will not repeat them.

[0486] As can be seen, the above mainly describes the technical solutions provided by the embodiments of this application from a methodological perspective. To achieve the above functions, it includes hardware structures and / or software modules corresponding to the execution of each function. Those skilled in the art should readily recognize that, in conjunction with the modules and algorithm steps of the various examples described in the embodiments disclosed herein, the embodiments of this application can be implemented in hardware or a combination of hardware and computer software. Whether a function is executed in hardware or by computer software driving hardware depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this invention.

[0487] This application embodiment can divide the communication device into functional modules according to the above method example. For example, each function can be divided into its own functional module, or two or more functions can be integrated into one processing module. The integrated module can be implemented in hardware or as a software functional module. Optionally, the module division in this application embodiment is illustrative and only represents one logical functional division; other division methods may be used in actual implementation.

[0488] like Figure 9The diagram shown is a structural schematic of a communication device provided in an embodiment of this application. The device includes a communication unit 901 and a processing unit 902.

[0489] The communication unit 901 and the processing unit 902 are configured to receive a redirection request from a target access network device; the redirection request includes a first globally unique temporary identifier (GUTI) of the terminal device; the first GUTI is the GUTI of the terminal device in the first PLMN network; the processing unit 902 is configured to determine the first GUTI of the terminal device according to the redirection request, and determine the source AMF according to the first GUTI; the communication unit 901 is also configured to send a session information request message to the source AMF; the communication unit 901 is also configured to receive session information of the terminal device from the source AMF.

[0490] Optionally, the processing unit 902 is specifically configured to: instruct the communication unit 901 to send a first request message to the source AMF; the first request message is used to request the context information and user permanent identifier SUPI of the terminal device; instruct the communication unit 901 to receive a first response message from the source AMF; the first response message includes the context information and SUPI of the terminal device; determine the terminal device according to the SUPI, and create a context for the terminal device according to the context information.

[0491] Optionally, the processing unit 902 is specifically used to: parse the first GUTI, determine the globally unique AMF identifier GUAMI in the first GUTI, and determine that the AMF represented by GUAMI is the source AMF.

[0492] Optionally, the communication unit 901 is also used to send a registration status update message to the source AMF; the registration status update message is used to instruct the source AMF to release the preset session; the preset session is a session established by the source AMF for the terminal device that is not supported by the target AMF.

[0493] Optionally, the communication unit 901 is also used to send a context request message to the home unified data management function (UDM); the context request message is used to request the subscription data of the terminal device from the UDM; the target AMF receives the subscription data of the terminal device from the UDM.

[0494] Optionally, the processing unit 902 is also configured to instruct the communication unit 901 to obtain the subscription data of the terminal device from the source AMF through the communication interface.

[0495] Optionally, the processing unit 902 is further configured to initiate a query to the target network slice selection function NSSF based on the first slice information to determine the second slice information and the AMF list that supports the second slice information, wherein the first slice information is the slice information of the terminal device in its home network.

[0496] Optionally, the processing unit 902 is further configured to determine whether the AMF list includes the target AMF; the first AMF is the AMF in the AMF list; if it does not include the target AMF, the first AMF is determined according to the AMF list.

[0497] Optionally, the communication unit 901 is further configured to send first indication information to the target access network device, so that the target access network device forwards at least one of the first AMF's identifier, registration request message, and second slice information to the first AMF according to the first indication information.

[0498] Optionally, the communication unit 901 is also configured to send third indication information to the first AMF; the third indication information includes at least one of the following: a registration request message, a SUPI of the terminal pole device, the context of the terminal device, and second slice information.

[0499] Optionally, the communication unit 901 is further configured to send a fifth indication message to the target access network device, the fifth indication message being used to indicate at least one of the PLMN list and the mobility restriction list.

[0500] like Figure 10 The diagram shown is a structural schematic of another communication device provided in an embodiment of this application. The device includes a communication unit 1001 and a processing unit 1002.

[0501] The processing unit 1002 is used to determine the frequency point information of the target access network device, and the communication unit 1001 is used to send the frequency point information to the terminal device. The frequency point information of the target access network device is used to instruct the terminal device to access the target access network device according to the frequency point information, and to send a redirection request to the terminal device through the target access network device.

[0502] Optionally, the processing unit 1002 is further configured to: determine the target PLMN identifier ID; the target PLMN ID is the PLMN ID that the terminal device needs to select when accessing the second PLMN network; and determine the frequency information of the PLMN network corresponding to the target PLMN ID as the frequency information of the target access network device.

[0503] The optional communication unit 1001 is further configured to receive a list of PLMNs from the source AMF; the list of PLMNs includes at least one of the following: the HPLMN of the terminal device, the serving PLMN, the Equivalent Public Land Mobile Network (EPLMN), and the previously selected PLMN; the processing unit 1002 is further configured to determine the target PLMN from the list of PLMNs.

[0504] Optionally, the processing unit 1002 is further configured to: determine the current serving PLMN ID of the terminal device according to the PLMN list; determine the home network of the terminal device according to the serving PLMN ID of the terminal device; determine the PLMN ID of the home network of the terminal device in the second PLMN network as the first PLMN ID; and determine the first PLMN ID as the target PLMN ID.

[0505] Optionally, the communication unit 1001 is further configured to receive a mobility restriction list from the source AMF; the mobility restriction list is used to indicate a first PLMN ID; the first PLMN ID is the PLMN ID of the terminal device's home network in the second PLMN network; the processing unit 1002 is further configured to determine that the first PLMN ID indicated by the mobility restriction list is the target PLMN ID.

[0506] Optionally, the processing unit 1002 is further configured to: determine the access network device adjacent to the source access network device in the second PLMN network as the target access network device; and determine the frequency point information of the target access network device.

[0507] like Figure 11 The diagram shown is a structural schematic of another communication device provided in an embodiment of this application. The device includes a communication unit 1101 and a processing unit 1102.

[0508] The processing unit 1102 is configured to instruct the communication unit 1101 to receive a session information request message from the target AMF; wherein the source AMF is the AMF determined by the target AMF based on the first GUTI of the terminal device; the processing unit 1102 is also configured to instruct the communication unit 1101 to send the session information of the terminal device to the target AMF in response to the session request message.

[0509] Optionally, the device further includes a processing unit 1102, which is also configured to instruct the communication unit 1101 to send a PLMN list to the source access network device; the PLMN list includes at least one of the following: the HPLMN of the terminal device, the serving PLMN, the Equivalent Public Land Mobile Network (EPLMN), and the previously selected PLMN.

[0510] Optionally, the processing unit 1102 is further configured to instruct the communication unit 1101 to send a mobility restriction list to the source access network device; the mobility restriction list is used to indicate a first PLMN ID; the first PLMN ID is the PLMN ID of the terminal device's home network in the second PLMN network.

[0511] Optionally, the processing unit 1102 is further configured to: determine the location information of the terminal device; determine that the PLMN network adjacent to the first PLMN network at the location represented by the location information of the terminal device is the second PLMN network; determine the PLMN ID in the second PLMN network that allows the terminal device to access the network; and determine the PLMN ID that allows the terminal device to access the network as the first PLMN ID.

[0512] Optionally, the device further includes: a processing unit 1102, which is further configured to instruct the communication unit 1101 to send first slice indication information to the target AMF; the first slice indication information is used to indicate first slice information, which is the slice information of the terminal device in the home network.

[0513] Optionally, the processing unit 1102 is further configured to: determine the first slice information when the PLMN IDs of the source AMF and the target AMF are different; and generate a first slice indication message based on the first slice information. Optionally, the first indication information is specifically used to indicate at least one of the slice information of the terminal device in the first PLMN network and the slice information of the mapped terminal device in the home network.

[0514] Optionally, the processing unit 1102 is further configured to: instruct the communication unit 1101 to receive a registration status update message from the target AMF; the registration status update message is used to instruct the source AMF to release a preset session; the preset session is a session established in the source AMF for the terminal device that is not supported by the target AMF; and release the preset session in response to the registration status update message.

[0515] The processing unit can be a processor or a controller. It can implement or execute various exemplary logic blocks, modules, and circuits described in conjunction with the disclosure of this application. The processor can also be a combination of functions, such as a combination of one or more microprocessors, a combination of a DSP and a microprocessor, etc. The communication unit can be a transceiver circuit or a communication interface, etc. The storage module can be a memory.

[0516] Through the above description of the implementation methods, those skilled in the art will clearly understand that, for the sake of convenience and brevity, only the division of the above functional modules is used as an example. In practical applications, the above functions can be assigned to different functional modules as needed, that is, the internal structure of the network node can be divided into different functional modules to complete all or part of the functions described above. The specific working process of the system, modules, and network nodes described above can be referred to the corresponding process in the foregoing method embodiments, and will not be repeated here.

[0517] This application also provides a computer-readable storage medium storing instructions. When a computer executes these instructions, the computer performs each step of the method flow shown in the above-described method embodiments.

[0518] Embodiments of this application provide a computer program product containing instructions that, when executed on a computer, cause the computer to perform the communication method described in the above method embodiments.

[0519] Embodiments of this application provide a chip, which includes a processor and a communication interface. The communication interface and the processor are coupled, and the processor is used to run computer programs or instructions to implement the communication method as described in the above method embodiments.

[0520] The computer-readable storage medium may be, for example, but not limited to, an electrical, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any combination thereof. More specific examples of computer-readable storage media (a non-exhaustive list) include: an electrical connection having one or more wires, a portable computer disk, a hard disk, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM), registers, hard disks, optical fibers, compact disc read-only memory (CD-ROM), optical storage devices, magnetic storage devices, or any suitable combination of the foregoing, or any other form of computer-readable storage medium in the art. An exemplary storage medium is coupled to a processor, enabling the processor to read information from and write information to the storage medium. Of course, the storage medium may also be a component of the processor. The processor and the storage medium may reside in an application-specific integrated circuit (ASIC). In embodiments of the present invention, a computer-readable storage medium may be any tangible medium that contains or stores a program that may be used by or in conjunction with an instruction execution system, apparatus, or device.

[0521] Since the apparatus, device, computer-readable storage medium, and computer program product in the embodiments of the present invention can be applied to the above methods, the technical effects that can be obtained can also be referred to the above method embodiments. The embodiments of this application will not be repeated here.

[0522] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any changes or substitutions within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A communication system, characterized in that, include: Terminal equipment, source access network equipment, source access and mobility management function (AMF), target AMF, and target access network equipment; The source access network device and the source AMF belong to the first public land mobile network (PLMN). The target AMF belongs to the second PLMN network; The source AMF and the target AMF are connected via a communication interface; The source access network device is used to determine the target PLMN identifier ID; The target PLMN ID is the PLMN ID that the terminal device needs to select when accessing the second PLMN network; The frequency point information of the PLMN network corresponding to the target PLMN ID is determined to be the frequency point information of the target access network device, and the frequency point information is sent to the terminal device; The terminal device is configured to determine the target access network device based on the frequency point information and initiate a redirection request to the target access network device; the redirection request includes the first globally unique temporary identifier (GUTI) of the terminal device; the first GUTI is the GUTI of the terminal device in the first PLMN network. The target access network device is used to forward the redirection request to the target AMF; The target AMF is used to determine the first GUTI of the terminal device, determine the source AMF based on the first GUTI, and send a session information request message to the source AMF. The source AMF is used to send the terminal device's session information to the target AMF in response to the session information request message; The source AMF is also used to send a PLMN list to the source access network device; the PLMN list includes at least one of the following: the HPLMN of the terminal device, the serving PLMN, the Equivalent Public Land Mobile Network (EPLMN), and the previously selected PLMN; The source access network device is further configured to determine the current serving PLMN ID of the terminal device based on the PLMN list; and determine the home network of the terminal device based on the serving PLMN ID of the terminal device. The PLMN ID of the terminal device's home network in the second PLMN network is determined to be the first PLMN ID; The first PLMN ID is determined to be the target PLMN ID.

2. The system according to claim 1, characterized in that, The target AMF is further configured to send a first request message to the source AMF; the first request message is configured to request the context information and user permanent identifier SUPI of the terminal device; The source AMF is configured to send a first response message to the target AMF according to the first request message; the first response message includes the context information and SUPI of the terminal device. The target AMF is also used to determine the terminal device based on the SUPI and to create a context for the terminal device based on the context information.

3. The system according to claim 1, characterized in that, The target AMF is specifically used for: Parse the first GUTI to determine the globally unique AMF identifier GUAMI in the first GUTI; The AMF characterized by the GUAMI is determined to be the source AMF.

4. The system according to any one of claims 2-3, characterized in that, The source AMF is further configured to send a mobility restriction list to the source access network device; the mobility restriction list is configured to indicate a first PLMN ID; the first PLMN ID is the PLMN ID of the terminal device's home network in the second PLMN network; The source access network device is configured to receive the mobility restriction list and determine that the first PLMN ID indicated by the mobility restriction list is the target PLMN ID.

5. The system according to claim 4, characterized in that, The source AMF is specifically used for: Determine the location information of the terminal device. The PLMN network adjacent to the first PLMN network at the location represented by the location information of the terminal device is determined to be the second PLMN network; Determine the PLMN ID in the second PLMN network that allows the terminal device to access the network; The PLMN ID that allows the terminal device to access the network is determined to be the first PLMN ID.

6. The system according to claim 5, characterized in that, The source access network device is also used for: The access network device adjacent to the source access network device in the second PLMN network is identified as the target access network device; Determine the frequency information of the target access network device.

7. The system according to claim 6, characterized in that, The target access network device is also used for: Obtain the target PLMN ID, the location information of the terminal device, and the slice information requested by the terminal device; The target AMF is determined based on the target PLMN ID, the location information of the terminal device, and the slice information requested by the terminal device.

8. The system according to claim 7, characterized in that, The source AMF is further configured to send first slice indication information to the target AMF; the first slice indication information is used to indicate first slice information, which is the slice information of the terminal device in its home network.

9. The system according to claim 8, characterized in that, The source AMF is specifically used for: If the PLMN IDs of the source AMF and the target AMF are different, the first slice information is determined; Based on the first slice information, generate the first slice indication information.

10. The system according to claim 8, characterized in that, The first slice indication information is specifically used to indicate at least one of the slice information of the terminal device in the first PLMN network and the slice information of the terminal device mapped in the first PLMN network in the home network; The target AMF is specifically used to: when the first PLMN network is the home network, determine the slice information of the terminal device in the first PLMN network as the first slice information; If the first PLMN network is not the home network, the slice information of the terminal device mapped in the first PLMN network in the home network is determined to be the first slice information.

11. The system according to claim 8, characterized in that, The target AMF is further used to: determine the first slice information; Determine the second slice information that the first slice information maps to in the second PLMN network; Based on at least one of the second slice information and the location information of the terminal device, a target session management function (SMF) is determined; the target SMF is the SMF in the second PLMN network.

12. The system according to claim 11, characterized in that, The target AMF is also used to send a registration status update message to the source AMF; the registration status update message is used to instruct the source AMF to release a preset session; the preset session is a session established by the source AMF for the terminal device that is not supported by the target AMF; The source AMF is also used to release the preset session in response to the registration status update message.

13. The system according to claim 12, characterized in that, The system also includes: Unified Data Management (UDM) function; The target AMF is also used to send a context request message to the home UDM; the context request message is used to request the subscription data of the terminal device from the UDM; The UDM is used to respond to the context request message and send the subscription data of the terminal device to the target AMF.

14. The system according to claim 12, characterized in that, The target AMF is also used to obtain the subscription data of the terminal device from the source AMF through the communication interface.

15. The system according to claim 14, characterized in that, The system also includes: Target Network Slice Selection Function (NSSF); The target AMF is further configured to initiate a query to the target NSSF based on the first slice information to determine the second slice information and the AMF list that supports the second slice information.

16. The system according to claim 14, characterized in that, The target AMF is further configured to query the slice mapping relationship configured in the target AMF based on the first slice information, determine the second slice information, and a list of AMFs that support the second slice information.

17. The system according to claim 15 or 16, characterized in that, The system further includes: a first AMF; the target AMF is also used for: Determine whether the target AMF is included in the AMF list; If not included, the first AMF is determined according to the AMF list.

18. The system according to claim 17, characterized in that, The target AMF is further configured to send first indication information to the target access network device, the first indication information including at least one of the following: the identifier of the first AMF, a registration request message, and the second slice information; The target access network device is configured to generate second indication information based on the first indication information and send the second indication information to the first AMF. The second indication information includes at least one of the following: the identifier of the first AMF, the registration request message, and the second slice information; The first AMF is used to determine, based on the second indication information, at least one of the following: the identifier of the first AMF, the registration request message, and the second slice information.

19. The system according to claim 17, characterized in that, The target AMF is further configured to send third indication information to the first AMF; the third indication information includes at least one of the following: a registration request message, the SUPI of the terminal device, the context of the terminal device, and the second slice information; The first AMF is used to determine, based on the third indication information, at least one of the following: the registration request message, the SUPI of the terminal device, the context of the terminal device, and the second slice information.

20. The system according to claim 18 or 19, characterized in that, The system also includes: Home SMF and Home Policy Control Function (PCF); The home SMF is also used to send a fourth indication message to the home PCF; the fourth indication message is used to indicate SM policy management; and to indicate the location information of the terminal device to the home PCF.

21. The system according to claim 20, characterized in that, The target AMF is further configured to send a fifth indication message to the target access network device, the fifth indication message being used to indicate at least one of the PLMN list and the mobility restriction list.

22. A communication method, characterized in that, Applied to a communication system, the communication system includes: terminal equipment, source access network equipment, source access and mobility management function (AMF), target AMF, and target access network equipment; The source access network device and the source AMF belong to a first public land mobile network (PLMN); the target AMF belongs to a second PLMN network; the source AMF and the target AMF are connected via a communication interface; the method includes: The source access network device determines the target PLMN identifier ID; the target PLMN ID is the PLMN ID that the terminal device needs to select when accessing the second PLMN network; the frequency point information of the PLMN network corresponding to the target PLMN ID is determined as the frequency point information of the target access network device; The target AMF receives a redirection request from the target access network device; the redirection request includes the terminal device's first globally unique temporary identifier (GUTI); the first GUTI is the terminal device's GUTI in the first PLMN network; The target AMF determines the first GUTI of the terminal device based on the redirection request, and determines the source AMF based on the first GUTI; The target AMF sends a session information request message to the source AMF; The target AMF receives session information from the terminal device of the source AMF; Specifically, the source access network device determines the target PLMN identifier ID, including: The source AMF sends a PLMN list to the source access network device; the PLMN list includes at least one of the following: the terminal device's HPLMN, serving PLMN, equivalent public land mobile network (EPLMN), and the previously selected PLMN. The source access network device determines the current serving PLMN ID of the terminal device based on the PLMN list; determines the home network of the terminal device based on the serving PLMN ID of the terminal device; determines the PLMN ID of the home network of the terminal device in the second PLMN network as the first PLMN ID; and determines the first PLMN ID as the target PLMN ID.

23. The method according to claim 22, characterized in that, The step of obtaining the session information of the terminal device from the source AMF includes: The target AMF sends a first request message to the source AMF; the first request message is used to request the context information and user permanent identifier (SUPI) of the terminal device. The target AMF receives a first response message from the source AMF; the first response message includes the context information and SUPI of the terminal device; The target AMF determines the terminal device based on the SUPI and creates a context for the terminal device based on the context information.

24. The method according to claim 22 or 23, characterized in that, Determining the source AMF based on the first GUTI includes: The target AMF parses the first GUTI and determines the globally unique AMF identifier GUAMI in the first GUTI; The target AMF determines that the AMF represented by the GUAMI is the source AMF.

25. The method according to claim 22 or 23, characterized in that, After determining the source AMF based on the first GUTI, the method further includes: The target AMF sends a registration status update message to the source AMF; the registration status update message is used to instruct the source AMF to release a preset session; the preset session is a session established by the source AMF for the terminal device that is not supported by the target AMF.

26. The method according to claim 25, characterized in that, After the target AMF sends a registration status update message to the source AMF, the method further includes: The target AMF sends a context request message to the home unified data management function UDM; the context request message is used to request the subscription data of the terminal device from the UDM; The target AMF receives subscription data from the terminal device of the UDM.

27. The method according to claim 25, characterized in that, After the target AMF sends a registration status update message to the source AMF, the method further includes: The target AMF obtains the subscription data of the terminal device from the source AMF through the communication interface.

28. The method according to claim 22 or 23, characterized in that, The method further includes: The target AMF initiates a query to the target network slice selection function NSSF based on the first slice information to determine the second slice information and the list of AMFs that support the second slice information. The first slice information is the slice information of the terminal device in its home network.

29. The method according to claim 28, characterized in that, After the target AMF initiates a query to the target network slice selection function NSSF based on the first slice information to determine the second slice information and the list of AMFs supporting the second slice information, the method further includes: The target AMF determines whether the target AMF is included in the AMF list; If not included, the first AMF is determined according to the AMF list.

30. The method according to claim 29, characterized in that, After the target AMF determines the first AMF based on the AMF list, the method further includes: The target AMF sends a first indication message to the target access network device, so that the target access network device forwards at least one of the following to the first AMF: the identifier of the first AMF, a registration request message, and the second slice information, according to the first indication message.

31. The method according to claim 29, characterized in that, After the target AMF determines the first AMF based on the AMF list, the method further includes: The target AMF sends a third indication message to the first AMF; the third indication message includes at least one of the following: a registration request message, the SUPI of the terminal device, the context of the terminal device, and the second slice information.

32. The method according to claim 30 or 31, characterized in that, The method further includes: The target AMF sends a fifth indication message to the target access network device, the fifth indication message being used to indicate at least one of the PLMN list and the mobility restriction list.

33. A communication method, characterized in that, Applied to a communication system, the communication system includes: terminal equipment, source access network equipment, source access and mobility management function (AMF), target AMF, and target access network equipment; The source access network device and the source AMF belong to a first public land mobile network (PLMN); the target AMF belongs to a second PLMN network; the source AMF and the target AMF are connected via a communication interface; the method includes: The source access network device determines the target PLMN identifier ID; the target PLMN ID is the PLMN ID that the terminal device needs to select when accessing the second PLMN network; The source access network device determines the frequency information of the PLMN network corresponding to the target PLMN ID as the frequency information of the target access network device, and sends the frequency information to the terminal device; the frequency information of the target access network device is used to instruct the terminal device to access the target access network device according to the frequency information, and sends a redirection request to the terminal device through the target access network device; The source access network device determines the target PLMN identifier ID by including: The source access network device receives a list of PLMNs from the source AMF; the list of PLMNs includes at least one of the following: the HPLMN of the terminal device, the serving PLMN, the Equivalent Public Land Mobile Network (EPLMN), and the previously selected PLMN; The source access network device determines the current service PLMN ID of the terminal device based on the PLMN list; The source access network device determines the home network of the terminal device based on the serving PLMN ID of the terminal device; The source access network device determines that the PLMN ID of the home network of the terminal device in the second PLMN network is the first PLMN ID; The source access network device determines that the first PLMN ID is the target PLMN ID; or, The source access network device receives a mobility restriction list from the source AMF; the mobility restriction list is used to indicate a first PLMN ID; the first PLMN ID is the PLMN ID of the terminal device's home network in the second PLMN network; the source access network device determines that the first PLMN ID indicated by the mobility restriction list is the target PLMN ID.

34. The method according to claim 33, characterized in that, The source access network device determines the frequency point information of the target access network device, including: The source access network device determines the access network device adjacent to the source access network device in the second PLMN network as the target access network device; The source access network device determines the frequency point information of the target access network device.

35. A communication method, characterized in that, Applied to a communication system, the communication system includes: terminal equipment, source access network equipment, source access and mobility management function (AMF), target AMF, and target access network equipment; The source access network device and the source AMF belong to a first public land mobile network (PLMN); the target AMF belongs to a second PLMN network; the source AMF and the target AMF are connected via a communication interface; the method includes: The terminal device determines the target access network device based on the frequency information of the PLMN network corresponding to the target PLMN ID; wherein, the method for obtaining the target PLMN ID includes: the source AMF sending a PLMN list to the source access network device, the PLMN list including at least one of the following: the terminal device's HPLMN, serving PLMN, equivalent public land mobile network (EPLMN), and the previously selected PLMN; the source access network device determining the terminal device's current serving PLMN ID based on the PLMN list; determining the terminal device's home network based on the terminal device's serving PLMN ID; determining the PLMN ID of the terminal device's home network in the second PLMN network as a first PLMN ID; determining the first PLMN ID as the target PLMN ID, or the source AMF sending a mobility restriction list to the source access network device, the mobility restriction list indicating the first PLMN ID, the first PLMN ID being the PLMN ID of the terminal device's home network in the second PLMN network, and determining the first PLMN ID as the target PLMN ID; The source AMF receives a session information request message from the target AMF; wherein the source AMF is the AMF determined by the target AMF based on the first GUTI of the terminal device; In response to the session information request message, the source AMF sends the session information of the terminal device to the target AMF; wherein the session information creates a session for the terminal device in the second PLMN network.

36. The method according to claim 35, characterized in that, Before the source AMF sends the mobility restriction list to the source access network device, the method further includes: The source AMF determines the location information of the terminal device. The source AMF determines the location represented by the location information of the terminal device, and the PLMN network adjacent to the first PLMN network is the second PLMN network; The source AMF determines the PLMN ID in the second PLMN network that allows the terminal device to access the network; The source AMF determines that the PLMN ID that allows the terminal device to access the network is the first PLMN ID.

37. The method according to any one of claims 35-36, characterized in that, After the source AMF receives a session information request message from the target AMF, the source AMF sends a first slice indication message to the target AMF; the first slice indication message is used to indicate first slice information, which is the slice information of the terminal device in its home network.

38. The method according to claim 37, characterized in that, The method further includes: If the PLMN IDs of the source AMF and the target AMF are different, the first slice information is determined; Based on the first slice information, generate the first slice indication message.

39. The method according to claim 37, characterized in that, The first slice indication information is specifically used to indicate at least one of the slice information of the terminal device in the first PLMN network and the slice information of the terminal device mapped in the first PLMN network in the home network.

40. The method according to claim 39, characterized in that, After the source AMF responds to the session information request message and sends the session information of the terminal device to the target AMF, the method further includes: The source AMF receives a registration status update message from the target AMF; the registration status update message is used to instruct the source AMF to release a preset session; the preset session is a session established by the source AMF for the terminal device that is not supported by the target AMF; The source AMF responds to the registration status update message by releasing the preset session.

41. A communication device, characterized in that, include: Communication unit and processing unit; The communication unit is used to communicate with other communication devices; The processing unit is configured to execute the communication method according to any one of claims 22-32; or execute the communication method according to any one of claims 33-34; or execute the communication method according to any one of claims 35-40.

42. A communication device, characterized in that, include: A processor and a memory; wherein the memory is used to store computer execution instructions, and when the communication device is running, the processor executes the computer execution instructions stored in the memory to cause the communication device to perform the communication method of any one of claims 22-32; or perform the communication method of any one of claims 33-34; or perform the communication method of any one of claims 35-40.

43. A computer-readable storage medium, characterized in that, The computer-readable storage medium includes instructions that, when executed, cause the computer to perform the communication method of any one of claims 22-32; or to perform the communication method of any one of claims 33-34; or to perform the communication method of any one of claims 35-40.

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