CN116456400A - Communication system, method, apparatus and storage medium - Google Patents

Abstract

The application provides a communication system, a method, a device and a storage medium, which relate to the technical field of communication and can realize redirection of connection-state terminal equipment among networks of a plurality of operators in the process of sharing a core network by the operators. The method comprises the following steps: the target AMF receives a redirection request from target access network equipment; the redirection request comprises a first global unique temporary identifier GUTI of the terminal equipment; the first GUTI is a GUTI of the terminal device in the first PLMN network; the target AMF determines a first GUTI of the terminal equipment 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; the target AMF receives session information from the terminal device of the source AMF. The embodiment of the application is used in the redirection process of the multi-operator shared core network.

Description

Communication system, method, device and storage medium

Technical Field

The present application relates to the field of communication technology, and in particular to a communication system, method, device and storage medium.

Background Art

In the related art, when multiple operators share a network, they usually only share access network equipment, and the shared access network equipment is connected to the core network equipment of each operator respectively. The terminal equipment is connected to the core network equipment to which the terminal equipment belongs through the shared access network equipment.

Currently, there is a demand for multiple operators to share a core network, but the related technology lacks a solution for redirecting a connected terminal device between the networks of multiple operators when multiple operators share a core network.

Summary of the invention

The present application provides a communication system, method, device and storage medium, which can realize the redirection of connected terminal devices between networks of multiple operators in the process of multiple operators sharing a core network.

In order to achieve the above purpose, this application adopts the following technical solutions:

In the first aspect, a communication system is provided, 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 network; the target AMF belongs to a second PLMN network; the source AMF is connected to the target AMF through a communication interface; the source access network device is used to determine the frequency information of the target access network device and send the frequency information to the terminal device; the terminal device is used to determine the target access network device according to the frequency 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 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 according to the first GUTI, and send a session information request message to the source AMF; the source AMF is used to send the session information of the terminal device to the target AMF in response to the session request message.

In combination with the above-mentioned first aspect, in a possible implementation method, the source access network device is specifically used to: determine the target PLMD identification ID; the target PLMN ID is the PLMN ID required to be selected when the terminal device accesses the second PLMN network; determine that the frequency information of the PLMN network corresponding to the target PLMN ID is the frequency information of the target access network device.

In combination with the above-mentioned first aspect, in a possible implementation method, the target AMF is also used to send a first request message to the source AMF; the first request message is used to request context information and a user permanent identifier SUPI of the terminal device; the source AMF is used 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 according to the SUPI, and create a context for the terminal device according to the context information.

In combination with the above-mentioned first aspect, in a possible implementation method, the target AMF 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 the GUAMI is the source AMF.

In combination with the above-mentioned first aspect, in a possible implementation method, 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 items: the HPLMN of the terminal device, the service PLMN, the equivalent public land mobile network EPLMN, and the previously selected PLMN; the source access network device is also used to determine the target PLMN from the PLMN list.

In combination with the above-mentioned first aspect, in a possible implementation method, the source access network device is specifically used to: determine the current service PLMN ID of the terminal device according to the PLMN list; determine the home network of the terminal device according to the service PLMN ID of the terminal device; determine that the PLMN ID of the home network of the terminal device in the second PLMN network is the first PLMN ID; and determine the first PLMN ID as the target PLMN ID.

In combination with the above-mentioned first aspect, in a possible implementation method, the source AMF is also used 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 home network of the terminal device in the second PLMN network; the source access network device is used to receive the mobility restriction list, and determine that the first PLMN ID indicated by the mobility restriction list is the target PLMN ID.

In combination with the above-mentioned first aspect, in a possible implementation method, the source AMF is specifically used 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; determine that the PLMN ID that allows the terminal device to access the network is the first PLMN ID.

In combination with the above-mentioned first aspect, in a possible implementation manner, the source access network device is further used to: determine an access network device adjacent to the source access network device in the second PLMN network as a target access network device; and determine frequency information of the target access network device.

In combination with the above-mentioned first aspect, in a possible implementation method, the target access network device is also used to: obtain the target PLMN ID, the location information of the terminal device, and the slice information requested by the terminal device; determine the target AMF according to the target PLMN ID, the location information of the terminal device, and the slice information requested by the terminal device.

In combination with the above-mentioned first aspect, in a possible implementation method, the source AMF is also used to send first slice indication information to the target AMF; the first slice indication information is used to indicate the first slice information, and the first slice information is the slice information of the terminal device in the home network.

In combination with the above-mentioned first aspect, in a possible implementation method, the source AMF is specifically used 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 combination with the above-mentioned first aspect, in a possible implementation method, 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 first network in the home network; the target AMF is specifically used to: when the first PLMN network is the home network, determine that the slice information of the terminal device in the first PLMN network is the first slice information; when the first PLMN network is not the home network, determine that the slice information of the mapped terminal device in the first network in the home network is the first slice information.

In combination with the above-mentioned first aspect, in a possible implementation method, the target AMF is also used to: determine the first slice information; determine the second slice information mapped by the first slice information in the second PLMN network; determine the target session management function SMF based on the second slice information and at least one item of the location information of the terminal device; the target SMF is the SMF in the second PLMN network.

In combination with the above-mentioned first aspect, in a possible implementation method, 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 the 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; the source AMF is also used to release the preset session in response to the registration status update message.

In combination with the first aspect, in a possible implementation, the system further includes: a home unified data management function UDM; a target AMF, further configured to send a context request message to the home UDM; the context request message is used to request the UDM for the contract data of the terminal device; the UDM is configured to respond to the context request message and send the contract data of the terminal device to the target AMF. 17. The system according to claim 15, characterized in that the target AMF is further configured to obtain the contract data of the terminal device from the source AMF through the communication interface.

In combination with the above-mentioned first aspect, in a possible implementation method, the system also includes: a target network slice selection function NSSF; a target AMF, which is also used to initiate a query to the target NSSF based on the first slice information, determine the second slice information, and an AMF list that supports the second slice information.

In combination with the above-mentioned first aspect, in a possible implementation method, the target AMF is also used to query the slice mapping relationship configured in the target AMF according to the first slice information, determine the second slice information, and the AMF list that supports the second slice information.

In combination with the above-mentioned first aspect, in a possible implementation method, the system also includes: a first AMF; a target AMF, and is also used to: determine whether the target AMF is included in the AMF list; the first AMF is the AMF in the AMF list; if not included, determine the first AMF according to the AMF list.

In combination with the above-mentioned first aspect, in a possible implementation method, the target AMF is also used to send first indication information to the target access network device, and the first indication information includes at least one of the following: an identifier of the first AMF, a registration request message, and second slice information; the target access network device is used 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: an identifier of the first AMF, a registration request message, and second slice information; the first AMF is used 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.

In combination with the above-mentioned first aspect, in a possible implementation method, the target AMF is also used 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 pole device, the context of the terminal device, and the second slice information; the first AMF is used 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 according to the third indication information.

In combination with the above-mentioned first aspect, in a possible implementation method, the system also includes: a belonging SMF and a belonging policy control function PCF; the belonging SMF is also used to send a fourth indication information to the belonging PCF; the fourth indication information is used to indicate SM policy management; and indicate the location information of the terminal device to the belonging PCF.

In combination with the above-mentioned first aspect, in a possible implementation method, the target AMF is also used to send fifth indication information to the target access network device, and the fifth indication information is used to indicate at least one item in the PLMN list and the mobility restriction list.

In a second aspect, a communication method is provided, which is applied to a communication system, wherein the communication system includes: 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 network; 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 target AMF receives 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 network; 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.

In combination with the above-mentioned second aspect, in a possible implementation method, obtaining session information of a terminal device from a source AMF includes: a target AMF sends a first request message to a source AMF; the first request message is used to request context information and a 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 according to the SUPI, and creates a context for the terminal device according to the context information.

In combination with the above-mentioned second aspect, in a possible implementation method, determining the source AMF according to the first GUTI includes: the target AMF parses the first GUTI to determine 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.

In combination with the above-mentioned second aspect, in a possible implementation method, after determining the source AMF according to the first GUTI, the method also 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 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.

In combination with the above-mentioned second aspect, in a possible implementation method, after the target AMF sends a registration status update message to the source AMF, the method also includes: the target AMF sends a context request message to the affiliated unified data management function UDM; the context request message is used to request the contract data of the terminal device from the UDM; the target AMF receives the contract data of the terminal device from the UDM.

In combination with the above-mentioned second aspect, in a possible implementation method, after the target AMF sends a registration status update message to the source AMF, the method also includes: the target AMF obtains the contract data of the terminal device from the source AMF through the communication interface.

In combination with the above-mentioned second aspect, in a possible implementation method, the method also 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 AMF list that supports the second slice information, where the first slice information is the slice information of the terminal device in the home network.

In combination with the above-mentioned second aspect, in a possible implementation method, 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 AMF list that supports the second slice information, the method also includes: the target AMF determines whether the target AMF is included in the AMF list; the first AMF is the AMF in the AMF list; if not included, the target AMF determines the first AMF based on the AMF list.

In combination with the above-mentioned second aspect, in a possible implementation method, after the target AMF determines the first AMF according to the AMF list, the method also includes: the target AMF sends a first indication message to the target access network device, so that the target access network device forwards the first AMF identifier, the registration request message, and at least one of the second slice information to the first AMF according to the first indication information.

In combination with the above-mentioned second aspect, in a possible implementation method, after the target AMF determines the first AMF according to the AMF list, the method also includes: the target AMF sends a 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 pole device, the context of the terminal device, and the second slice information.

In combination with the above-mentioned second aspect, in a possible implementation manner, the method also includes: the target AMF sends fifth indication information to the target access network device, and the fifth indication information is used to indicate at least one item in the PLMN list and the mobility restriction list.

According to a third aspect, a communication method is provided, which is applied to a communication system, wherein the communication system includes: 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 network; 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 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 via the target access network device.

In combination with the above-mentioned third aspect, in a possible implementation method, the source access network device determines the frequency information of the target access network device, including: the source access network device determines the target PLMD identification ID; the target PLMN ID is the PLMN ID required to be selected when the terminal device accesses the second PLMN network; the source access network device determines that the frequency information of the PLMN network corresponding to the target PLMN ID is the frequency information of the target access network device.

In combination with the above-mentioned third aspect, in a possible implementation method, after the source access network device sends the frequency information to the terminal device, the method also includes: the source access network device receives a PLMN list from the source AMF; the PLMN list includes at least one of the following: the HPLMN of the terminal device, the service PLMN, the equivalent public land mobile network EPLMN, the PLMN selected last time; the source access network device determines the target PLMN from the PLMN list.

In combination with the above-mentioned third aspect, in a possible implementation method, the source access network device determines the target PLMN from the PLMN list, including: the source access network device determines the current service PLMN ID of the terminal device according to the PLMN list; the source access network device determines the home network of the terminal device according to the service 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 the first PLMN ID as the target PLMN ID.

In combination with the above-mentioned third aspect, in a possible implementation method, after the source access network device sends the frequency information to the terminal device, the method also includes: 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.

In combination with the above-mentioned third aspect, in a possible implementation method, the source access network device determines the frequency 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 information of the target access network device.

In a fourth aspect, a communication method is provided, which is applied to a communication system, wherein the communication system includes: 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 network; 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 AMF receives a session information request message from the target AMF; wherein the source AMF is the AMF determined by the target AMF according to the first GUTI of the terminal device; the source AMF sends the session information of the terminal device to the target AMF in response to the session request message.

In combination with the above-mentioned fourth aspect, in a possible implementation method, the method also includes: the source AMF sends 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 service PLMN, the equivalent public land mobile network EPLMN, and the previously selected PLMN.

In combination with the above-mentioned fourth aspect, in a possible implementation method, the method also includes: the source AMF sends a mobility restriction list to the source access network device; the mobility restriction list is used to indicate the first PLMN ID; the first PLMN ID is the PLMN ID of the terminal device's home network in the second PLMN network.

In combination with the above-mentioned fourth aspect, in a possible implementation method, before the source AMF sends the mobility restriction list to the source access network device, the method also includes: the source AMF determines the location information of the terminal device, the source AMF determines 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 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.

In combination with the above-mentioned fourth aspect, in a possible implementation method, the method also includes: the source AMF sends first slice indication information to the target AMF; the first slice indication information is used to indicate the first slice information, and the first slice information is the slice information of the terminal device in the home network.

In combination with the above-mentioned fourth aspect, in a possible implementation method, the method also includes: when the PLMN IDs of the source AMF and the target AMF are different, determining the first slice information; and generating a first slice indication message based on the first slice information.

In combination with the above-mentioned fourth aspect, in a possible implementation method, 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 first network in the home network.

In combination with the above-mentioned fourth aspect, in a possible implementation method, the method also 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 the 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; the source AMF releases the preset session in response to the registration status update message.

In a fifth aspect, a communication device is provided, which is applied to a communication system, wherein the communication system includes: 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 network; the target AMF belongs to a second PLMN network; the source AMF and the target AMF are connected through a communication interface; the device includes: a communication unit and a processing unit, the communication unit being used for 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 being 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 also used to send a session information request message to the source AMF; the communication unit is also used to receive session information of the terminal device from the source AMF.

In combination with the fifth aspect above, in a possible implementation method, the processing unit is specifically used to: instruct the communication unit to send a first request message to the source AMF; the first request message is used to request context information and a user permanent identifier SUPI of the terminal device; the communication unit receives a first response message from the source AMF; the first response message includes the context information and SUPI of the terminal device; the terminal device is determined according to the SUPI, and a context is created for the terminal device according to the context information.

In combination with the fifth aspect, in a possible implementation method, 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 the GUAMI is the source AMF.

In combination with the above-mentioned fifth aspect, in a possible implementation method, the communication unit 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.

In combination with the above-mentioned fifth aspect, in a possible implementation method, the communication unit is also used to send a context request message to the unified data management function UDM; the context request message is used to request the contract data of the terminal device from the UDM; the target AMF receives the contract data of the terminal device from the UDM.

In combination with the above-mentioned fifth aspect, in a possible implementation method, the processing unit is also used to instruct the communication unit to obtain the contract data of the terminal device from the source AMF through the communication interface.

In combination with the above-mentioned fifth aspect, in a possible implementation method, the processing unit is also used 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, where the first slice information is the slice information of the terminal device in the home network.

In combination with the above-mentioned fifth aspect, in a possible implementation method, the processing unit is also used to determine whether the target AMF is included in the AMF list; the first AMF is the AMF in the AMF list; if not included, the first AMF is determined according to the AMF list.

In combination with the above-mentioned fifth aspect, in a possible implementation method, the communication unit is also used to send a first indication information to the target access network device, so that the target access network device forwards the first AMF identifier, the registration request message, and at least one of the second slice information to the first AMF according to the first indication information.

In combination with the above-mentioned fifth aspect, in a possible implementation method, the communication unit is also used 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 pole device, the context of the terminal device, and the second slice information.

In combination with the fifth aspect above, in a possible implementation, the communication unit is further used to send fifth indication information to the target access network device, where the fifth indication information is used to indicate at least one item in the PLMN list and the mobility restriction list.

In a sixth aspect, a communication device is provided, which is applied to a communication system, wherein the communication system includes: 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 network; the target AMF belongs to a second PLMN network; the source AMF and the target AMF are connected via a communication interface; the device includes: a communication unit, and a processing unit; the processing unit is used to determine the frequency information of the target access network device, and the communication unit is used to send 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 send a redirection request to the terminal device via the target access network device.

In combination with the above-mentioned sixth aspect, in a possible implementation method, the processing unit is also used to: determine the target PLMD identification ID; the target PLMN ID is the PLMN ID required to be selected when the terminal device accesses the second PLMN network; determine that the frequency information of the PLMN network corresponding to the target PLMNID is the frequency information of the target access network device.

In combination with the above-mentioned sixth aspect, in a possible implementation method, the communication unit is also used to receive a PLMN list from the source AMF; the PLMN list includes at least one of the following: HPLMN of the terminal device, the service PLMN, the equivalent public land mobile network EPLMN, and the previously selected PLMN; the processing unit is also used to determine the target PLMN from the PLMN list.

In combination with the sixth aspect, in a possible implementation method, the processing unit is further used to: determine the current service PLMN ID of the terminal device according to the PLMN list; the source access network device determines the home network of the terminal device according to the service PLMN ID of the terminal device; determine that the PLMN ID of the home network of the terminal device in the second PLMN network is the first PLMN ID; and determine that the first PLMN ID is the target PLMN ID.

In combination with the above-mentioned sixth aspect, in a possible implementation method, the communication unit is also used to receive a mobility restriction list from a source AMF; 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 in the second PLMN network; the processing unit is also used to determine that the first PLMN ID indicated by the mobility restriction list is the target PLMN ID.

In combination with the sixth aspect, in a possible implementation, the processing unit is further used to: determine an access network device adjacent to the source access network device in the second PLMN network as a target access network device; and determine frequency information of the target access network device.

In the seventh aspect, a communication device is provided, which is applied to a communication system, wherein the communication system includes: 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 network; the target AMF belongs to a second PLMN network; the source AMF and the target AMF are connected through a communication interface; the device includes: a communication unit and a processing unit; the processing unit is used to instruct the communication unit to receive a session information request message from the target AMF; wherein the source AMF is the AMF determined by the target AMF according to the first GUTI of the terminal device; the processing unit is also used to instruct the communication unit to send the session information of the terminal device to the target AMF in response to the session request message.

In combination with the above-mentioned seventh aspect, in a possible implementation method, the device also includes: a processing unit, which is also used to instruct the communication unit to send a PLMN list to the source access network device; the PLMN list includes at least one of the following items: the HPLMN of the terminal device, the service PLMN, the equivalent public land mobile network EPLMN, and the previously selected PLMN.

In combination with the above-mentioned seventh aspect, in a possible implementation method, the processing unit is also used 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 the first PLMN ID; the first PLMN ID is the PLMN ID of the terminal device's home network in the second PLMN network.

In combination with the above-mentioned seventh aspect, in a possible implementation method, the processing unit is also used 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; determine that the PLMN ID that allows the terminal device to access the network is the first PLMN ID.

In combination with the above-mentioned seventh aspect, in a possible implementation method, the device also includes: a processing unit, which is also used 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, and the first slice information is slice information of the terminal device in the home network.

In combination with the above-mentioned seventh aspect, in a possible implementation method, the processing unit is also used 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 combination with the above-mentioned seventh aspect, in a possible implementation method, 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 first network in the home network.

In combination with the above-mentioned seventh aspect, in a possible implementation method, the processing unit is also used 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 the 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; in response to the registration status update message, the preset session is released.

In an eighth aspect, the present application provides a communication device, comprising: a processor and a communication interface; the communication interface and the processor are coupled, and the processor is used to run a computer program or instructions to implement the communication method described in the first aspect and any possible implementation method of the first aspect.

In a ninth aspect, the present application provides a communication device, comprising: a processor and a communication interface; the communication interface and the processor are coupled, and the processor is used to run a computer program or instructions to implement the communication method described in the second aspect and any possible implementation method of the second aspect.

In the tenth aspect, the present application provides a communication device, comprising: a processor and a communication interface; the communication interface and the processor are coupled, and the processor is used to run a computer program or instructions to implement the communication method described in the third aspect and any possible implementation method of the third aspect.

In the eleventh aspect, the present application provides a computer-readable storage medium, which stores instructions. When the instructions in the computer-readable storage medium are executed by a processor of a communication device, the communication device is enabled to perform the communication method described in the first aspect and any possible implementation of the first aspect.

In the twelfth aspect, the present application provides a computer-readable storage medium, which stores instructions. When the instructions in the computer-readable storage medium are executed by a processor of a communication device, the communication device is enabled to perform the communication method described in the second aspect and any possible implementation of the second aspect.

In the thirteenth aspect, the present application provides a computer-readable storage medium, which stores instructions. When the instructions in the computer-readable storage medium are executed by a processor of a communication device, the communication device is enabled to perform the communication method described in the third aspect and any possible implementation of the third aspect.

In this application, the name of the above communication device does not limit the device or functional module itself. In actual implementation, these devices or functional modules may appear with other names. As long as the functions of each device or functional module are similar to those of the present invention, they belong to the scope of the claims of the present invention and their equivalent technologies.

These and other aspects of the present invention will become more apparent from the following description.

The technical solution provided by the present application brings at least the following beneficial effects: In the communication system provided by the present application, the source AMF and the target AMF of different operators communicate through a communication interface (exemplarily, the communication interface can be an N14+ interface). When the terminal device is redirected from the first PLMN network to the second PLMN network, the source access network device indicates the frequency of the target access network device to the terminal device by discovering the frequency of the target access network device, so that the terminal device can access the target access network device according to the frequency information. The target AMF discovers the source AMF according to the GUTI of the terminal device, and obtains the session information of the terminal device 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 session information of the terminal device, so that the terminal device can be redirected to the second PLMN network. Thereby, the redirection of the connected terminal device between the networks of multiple operators is realized.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a system architecture diagram of a MOCN system provided in an embodiment of the present application;

FIG2 is a system architecture diagram of a communication system provided in an embodiment of the present application;

FIG3 is a schematic diagram of a scenario in which multiple operators share an access network and a core network according to an embodiment of the present application;

FIG4 is a system architecture diagram of another communication system provided in an embodiment of the present application;

FIG5 is a flow chart of a communication method provided in an embodiment of the present application;

FIG6 is a flow chart of a redirection method when a terminal device moves from a first area to a second area provided in an embodiment of the present application;

7 is a schematic flow chart of a redirection method when a terminal device moves from a second area to a first area provided in an embodiment of the present application;

FIG8 is a schematic flow chart of a redirection method when a terminal device moves from a second area to a third area provided in an embodiment of the present application;

FIG9 is a schematic diagram of the structure of a communication device provided in an embodiment of the present application;

FIG10 is a schematic diagram of the structure of another communication device provided in an embodiment of the present application;

FIG. 11 is a schematic diagram of the structure of another communication device provided in an embodiment of the present application.

DETAILED DESCRIPTION

The communication system, method, device and storage medium provided in the embodiments of the present application are described in detail below in conjunction with the accompanying drawings.

The term "and/or" in this article is merely a description of the association relationship of associated objects, indicating that three relationships may exist. For example, A and/or B can mean: A exists alone, A and B exist at the same time, and B exists alone.

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

In addition, the terms "including" and "having" and any variations thereof mentioned in the description of the present application are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device comprising a series of steps or units is not limited to the listed steps or units, but may optionally include other steps or units that are not listed, or may optionally include other steps or units that are inherent to these processes, methods, products or devices.

It should be noted that in the embodiments of the present application, words such as "exemplary" or "for example" are used to indicate examples, illustrations or descriptions. Any embodiment or design described as "exemplary" or "for example" in the embodiments of the present application should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of words such as "exemplary" or "for example" is intended to present related concepts in a specific way.

In the description of the present application, unless otherwise specified, “plurality” means two or more.

The following explains the terms involved in the embodiments of the present application to facilitate the reader's understanding.

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

At present, with the development of the fifth generation mobile communication technology (5G) network, the network coverage is more dense, the number of base stations is increasing, and the network construction cost of operators is also increasing. In order to reduce the cost of network construction, a network sharing method is currently proposed, in which multiple operators share the same network, thereby reducing the duplication of communication network construction, saving the overall network investment, and alleviating the huge cost faced by network construction.

The 3GPP R16 protocol specification specifies a shared network architecture that supports 5G MOCN. In this network architecture, terminal devices are supported to share 5G access networks (RAN) of different operators. The network architecture of MOCN is shown in Figure 1.

As shown in FIG. 1 , the MOCN system 10 includes a core network device 101 of operator A, a core network device 102 of operator B, a core network device 103 of operator C, a core network device 104 of operator X, and an access network device 105 of operator X.

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.

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.

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 the access network device 105 of operator X within the coverage of operator X to complete the communication service for the terminal devices.

2. The way in which access network equipment broadcasts public land mobile network (PLMN) identification (Identity, ID) in the current MOCN shared network system.

In the current MOCN system, the access network device of the shared network will carry the PLMN ID of the core network of each operator sharing the access network device in the broadcast system message.

For example, when operator A and operator X share access networks in the MOCN mode, the access network equipment of the shared network carries the PLMN IDs of operator A and operator X in the broadcast system information. Each PLMN ID corresponds to a core network of an operator.

After receiving the broadcast system message, the terminal device parses the system message and determines the PLMN ID carried in the system message. The terminal device determines the core network to which the access network device of the shared network is connected based on the PLMN ID, and selects the PLMN ID of the network to which the terminal device belongs. The terminal device notifies the access network device of the shared network of the selected PLMN ID. After receiving the PLMN ID selected by the terminal device, the access network device of the shared network routes the service data of the terminal device to the core network selected by the terminal device based on the PLMN ID selected by the terminal device.

In one example, in conjunction with FIG1 , when operator X, operator A, operator B, and operator C share the access network of operator X, the PLMN selection (or reselection) process of the terminal equipment of operator X, operator A, operator B, and operator C is shown in Table 1 below:

Table 1. In the MOCN sharing mode, the PLMN ID carried in the system message broadcast by the access network equipment of the shared network and the PLMN selection and message routing of the terminal equipment of each operator:

It should be pointed out that in actual applications, in addition to the core network identification PLMN-ID (A) of operator A, the core network identification PLMN-ID (B) of operator B, and the core network identification PLMN-ID (C) of operator C in the broadcast system message, the access network equipment of operator X also carries the core network identification PLMN-ID (X) of operator X. Since the access network equipment of operator X carries PLMN-ID (X) in the broadcast system message, it belongs to the conventional broadcast mode, not the shared network broadcast mode. Therefore, FIG. 1 and Table 1 do not show the situation where the terminal equipment of operator X performs network sharing.

In one example, when operator A and operator X share the network using MOCN, the access network built by operator A carries the PLMN ID of operator B in the broadcast system message, so that the terminal equipment of operator B can access the access network of operator A; at the same time, the system message also carries the PLMN ID of operator A so that the terminal equipment of operator A can also access the access network of operator A.

Similarly, the access network built by operator X carries the PLMN ID of operator A in the broadcast system message, so that the terminal equipment of operator A can access the access network of operator X; at the same time, the system message also carries the PLMN ID of operator X so that the terminal equipment of operator X can also access the access network of operator X.

In MOCN sharing mode, the terminal device needs to select the core network according to the PLMN ID broadcast by the access network device of the shared network. Therefore, the number of PLMN IDs broadcast by the access network device of the shared network needs to be the same as the number of 5G core networks sharing the access network. Therefore, the access network device of the shared network must broadcast multiple PLMN IDs so that all terminal devices can access the access network.

In the case where N operators share access, the maximum number of shared operators carried in the system message broadcast by the access network device of the shared access network is N-1. N is a positive integer.

In addition, in the MOCN sharing mode, the PLMN ID broadcast by the shared access network is the same as the PLMNID of each shared operator. In this way, the terminal device has the shortest delay in selecting the PLMN (the specific delay is determined according to the selection order of the PLMN ID of the terminal device) and the shortest time for the terminal device to select the network. In particular, when the terminal device is turned on, or when the terminal device selects a cell after recovering from a cell without coverage, and when the terminal device in the idle state reselects a cell, this method has the shortest delay required for selecting the PLMN and selecting the network.

The use of MOCN shared access network has at least the following advantages: Under the architecture of MOCN's shared access network, the core networks of different operators are set up completely independently, and have better support for 5G special services such as network slicing and edge computing.

The above explains the terms involved in the embodiments of the present application.

Figure 2 is a communication system 20 provided in an embodiment of the present application. As shown in Figure 2, the communication system provided in an embodiment of the present application 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.

The first access network device 201 is used to implement the function of the wireless access network and provide wireless access services for the terminal device. The first access network device 201 is the access network device of the operator of the construction party. For example, the access network device of operator X.

The first core network device 202 is a core network device of the operator of the construction party, for example, a core network device of operator X.

For the terminal equipment of the construction operator, the first core network equipment 202 is used to implement core network related functions and provide core network related business services.

The first core network device 202 for the terminal device of the shared operator is used to provide data routing function, routing the service data of the terminal device to the core network of the terminal device. At this time, the first core network device 202 can also perform access control, policy control, network selection, and billing settlement on the terminal device.

The second core network device 203 is a core network device of a sharing operator, and is used for the terminal device of the sharing operator to implement core network related functions, for example, to provide data processing or forwarding functions.

In FIG. 2 , an example is taken in which one less second core network device 203 includes a core network device 2031 of operator A, a core network device 2032 of operator B, and a core network device 2033 of operator C. The example is used for explanation.

Among them, the core network equipment 2031 of operator A is used to provide core network-related business services for the terminal equipment of operator A; the core network equipment 2032 of operator B is used to provide core network-related business services for the terminal equipment of operator B; and the core network equipment 2033 of operator C is used to provide core network-related business services for the terminal equipment of operator C.

The terminal device 204 is a device that needs to provide communication services, and may be a terminal device that belongs to the same operator as the first access network device 201 and the first core network device 202. The terminal device 204 may also be a terminal device that belongs to the same operator as any one of the at least one second core network devices 203. This application is mainly described by taking the example that the terminal device is a terminal device that belongs to the same operator as any one of the at least one second core network devices 203.

It should be pointed out that the core network equipment in the embodiments of the present application mainly refers to 5G core network equipment.

In the above, each device in the communication system 20 shown in FIG. 2 is briefly described.

Figure 3 is a schematic diagram of a scenario in which multiple operators share access networks and core networks according to an embodiment of the present application. As shown in Figure 3, 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.

In the embodiment of the present application, the terminal device is mainly taken as a terminal device belonging to operator A as an example for description.

Among them, operator A, operator X and operator Y can share access network and core network. In this way, when the terminal device moves within the coverage of operator A's access network device 304, operator X's access network device 305 and operator Y's access network device 306, it can access the corresponding operator's access network device and core network device to provide network communication services.

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.

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.

The access network equipment 306 of operator Y is connected to the core network equipment 303 of operator Y through the N1/N2/N3 interface; the core network equipment 303 of operator Y is connected to the core network equipment 301 of operator A through the N9/N16/N8/N12/N24/N32/N14+ interface.

The coverage area of the access network device 304 of operator A is recorded as the first area; the coverage area of the access network device 305 of operator X is recorded as the second area; and the coverage area of the access network device 306 of operator Y is recorded as the third area.

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

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.

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.

The application scenarios of the embodiments of the present application are described above.

It should be pointed out that in the communication systems shown in Figures 2 and 3, the terminal equipment, access network equipment and core network equipment all need to execute corresponding action processes and implement corresponding functions to achieve redirection of connected terminal equipment between networks of multiple operators.

Specifically, it 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 frequency of target access network equipment; Scenario 3, the interconnection and interaction between access network equipment and core network equipment of different operators.

The following describes scenarios 1 to 3 respectively:

Scenario 1: The process of access network equipment broadcasting PLMN ID.

In order to inform the terminal device of the PLMN network supported by the access network device, the access network device needs to broadcast the PLMN ID to the terminal device. When broadcasting the PLMN ID, the access network device can use any of the following schemes 1 to 3 to broadcast the PLMN ID. The following describes schemes 1, 2, and 3 respectively:

Solution 1: The access network device broadcasts the original PLMN ID of each core network connected to the access network device. The PLMN ID of each core network is the same as the PLMN ID broadcasted for the core network in the network of the operator to which it belongs. That is to say, in Solution 1, the access network device broadcasts the PLMN ID of each core network in the same manner as the MOCN broadcasts the PLMN ID in the related art.

As an example, in conjunction with Figure 2, when the access network equipment of operator X broadcasts the PLMN ID, the core network of operator A broadcasts PLMN ID (A), the core network of operator B broadcasts PLMN ID (B), and the core network of operator C broadcasts PLMN ID (C).

The use of solution 1 to broadcast the PLMN ID brings at least the following beneficial effects: when the terminal device obtains the PLMN ID, the delay required to select the PLMN (for example, when the terminal device is disconnected from the network during the startup process or when recovering from a coverage-free area) is the shortest. In addition, in solution 1, the access network device broadcasts the PLMN ID of each core network in the same manner as the MOCN broadcasts the PLMN ID in the related art, without creating a new network number, which will not cause a waste of network number resources.

In solution 1, the maximum number of PLMN IDs of the core network of the shared operator that can be broadcast by the access network device is N-1. N is the maximum number of broadcast PLMN IDs that can be supported by the access network device, and N is a positive integer.

Solution 2: The access network device broadcasts a new PLMN ID for each core network connected to the access network device. The new PLMN ID of each core network is different from the PLMN ID broadcast for the core network in the network of the operator to which it belongs. For example, the access network device can merge the PLMN ID of the contractor operator with the PLMN ID of the shared operator to obtain the PLMN ID of each core network.

As an example, in conjunction with Figure 2, when the access network equipment of operator X broadcasts the PLMN ID, the core network of operator A broadcasts the PLMN ID (XA), the core network of operator B broadcasts the PLMN ID (XB), and the core network of operator C broadcasts the PLMN ID (XC).

The adoption of solution 2 to broadcast the PLMN ID brings at least the following beneficial effects: the access network device can customize and broadcast the new PLMN ID. In this way, after receiving the new PLMN ID, the terminal device can determine that the access network is a shared access network constructed by operator X according to the new PLMN ID. In addition, the terminal device can also display the network identifier of the operator who constructed the network and the network identifier of the shared operator on the display interface at the same time according to the new PLMN ID.

In solution 2, the maximum number of PLMN IDs of the core network of the shared operator that can be broadcast by the access network device is N-1.

Solution 3: The access network device broadcasts a same PLMN ID to each core network connected to the access network device.

In one example, in conjunction with FIG2 , the access network device only broadcasts the PLMN ID of the core network of operator X. Alternatively, the access network device only broadcasts the new PLMN ID (XY) of the core network of operator X.

Adopting Scheme 3 to broadcast the PLMN ID brings at least the following beneficial effects: the access network device only needs to broadcast one PLMNID, which reduces the signaling overhead of the access network device. When the access network device only broadcasts the PLMN ID of the core network of operator X, it will not cause 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 increase the function of the first core network device to determine the home network of the terminal device without the need to use the PLMN ID selected by the terminal device. For example, the function of the first core network device to identify the user permanent identifier (SUbscription Permanent Identifier, SUPI) or HPLMN of the terminal device is extended. Accordingly, the terminal device also needs to have the function of reporting SUPI or HPLMN.

As an example, in combination with the above-mentioned solution 1, solution 2, and solution 3 and FIG. 2, the PLMN ID broadcast by the access network equipment of operator X is shown in Table 2 below:

Table 2: The way in which the access network equipment of operator X broadcasts the PLMN ID

In a possible implementation manner, the access network device broadcasts the PLMN ID by broadcasting a first system message, wherein the first system message carries the PLMN ID that the terminal device needs to broadcast.

The above describes in detail the manner in which the access network device in scenario 1 broadcasts the PLMN ID.

The following describes scenario 2, a process in which an access network device selects a target PLMN ID and a frequency of a target access network device.

Scenario 2: The process in which the source access network device selects the target PLMN ID and the frequency of the target access network device.

In scenario 2, the source access network device may determine the frequency of the target access network device by the following method 1; and determine the target PLMN ID by any of the following methods 2 and 5. The following are respectively described:

Method 1: The source access network device configures the frequency of the target access network device based on the PLMN ID.

Specifically, the description is given by taking the terminal device being the access network device of operator A as an example.

Mode 1.1: For the source access network device of operator A, when the source access network device is a base station at the boundary of the first area and the second area. The source access network device determines that the PLMN ID used by the terminal device to access operator X is PLMN-ID (XA) in scheme 2 (it can also be the PLMN ID in other schemes). 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 that the target PLMN ID is PLMN-ID (XA), and the frequency of the target access network device is F2.

When the source access network device is a base station at the boundary of the first area and the third area. The source access network device determines that the PLMN ID used by the terminal device to access operator Y is PLMN-ID (YA) in scheme 2 (it can also be the PLMN ID in other schemes). The source access network device determines the frequency (or frequency point) F3 of the access network device of operator Y adjacent to it. At this time, the source access network device determines that the target PLMN ID is PLMN-ID (YA), and the frequency of the target access network device is F3.

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

When the source access network device is a base station at the boundary of the second area and the third area. The source access network device determines that the PLMN ID used by the terminal device to access operator Y is PLMN-ID (YA) in scheme 2 (it can also be the PLMN ID in other schemes). The source access network device determines the frequency (or frequency point) F3 of the access network device of operator Y adjacent to it. At this time, the source access network device determines that the target PLMN ID is PLMN-ID (YA), and the frequency of the target access network device is F3.

Method 1.3: For the source access network device of operator Y, when the source access network device is a base station at the boundary of the third area and the first area. The source access network device determines that the PLMN ID used by the terminal device to access operator A is PLMN-ID(A). The source access network device determines the frequency (or frequency point) F1 of the access network device of operator A adjacent to it. At this time, the source access network device determines that the target PLMN ID is PLMN-ID(A), and the frequency of the target access network device is F1.

When the source access network device is a base station at the boundary of the third area and the second area. The source access network device determines that the PLMN ID used by the terminal device to access operator X is PLMN-ID (XA) in solution 2 (it can also be PLMN ID in other solutions). The source access network device determines the frequency (or frequency point) F2 of the adjacent operator X access network device. At this time, the source access network device determines that the target PLMN ID is PLMN-ID (XA), and the frequency of the target access network device is F2.

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

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

The source AMF can select the target AMF/Mobility Management Entity (MME) mobility management entity MME (this application mainly uses the target AMF as an example for explanation) according to the TAI information provided by the source access network device. Then, the source AMF sends the selected target PLMN ID to the target AMF/MME.

Specifically, the source access network device is able to determine the current service PLMN ID of the terminal device, and determine the home network of the terminal device based on the service PLMN ID of the terminal device; the terminal device determines that the PLMN ID of the home network of the terminal device in the second PLMN network is the first PLMN ID, and the terminal device determines the first PLMN ID as the target PLMN ID.

In one example, when the terminal device of operator A moves from the second area to the first area, it determines that the PLMN ID of the current service is PLMN ID (XA) (that is, the access network device broadcasts the PLMN ID using solution 2). At this time, the source access network device determines that the home network of the terminal device is the network of operator A based on the PLMN ID of the current service being PLMN ID (XA). In the network of operator A, the PLMN ID of operator A is PLMN ID (A). At this time, the source access network device determines PLMN ID (A) as the target PLMN ID.

In another example, the access network device of operator X broadcasts the PLMN ID (XA) for the terminal device of operator A. When the terminal device of operator A moves from the second area to the first area, the access network device of operator X can determine that the home network of the terminal device is PLMN ID (A) according to the current service PLMN ID (XA) of the terminal device. At this time, the access network device of operator X determines that the target PLMN ID is PLMN ID (A) according to the current service PLMN ID (XA). The access network device of operator X indicates to the AMF of operator X that the target PLMN ID is PLMN ID (A).

The above is merely an exemplary description, and the implementation methods of the process of moving the terminal device between other areas will not be elaborated on.

Mode 3: The source access network device determines the target PLMN ID according to the PLMN list sent by the source AMF (referred to as Mode 3.1), or determines the target PLMN ID according to the mobility restriction list sent by the source AMF (referred to as Mode 3.2). The following describes Mode 3.1 and Mode 3.2 respectively:

Method 3.1: The source access network device determines the target PLMN ID based on the PLMN list sent by the source AMF.

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 service PLMN ID of the terminal device, the SUPI number segment of the terminal device, and the location information of the terminal device; the source AMF determines the first PLMN ID according to the PLMN auxiliary information of the terminal device, and generates the PLMN list according to 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 according to the PLMN list.

Alternatively, the source AMF determines the PLMN list of the terminal device based on the HPLMN, serving PLMN, EPLMN, previous PLMN (Last PLMN) and other information of the terminal device.

The PLMN list includes a first PLMN ID; the first PLMN ID is the PLMN ID of the home network of the terminal device in the second PLMN network.

In one example, when the terminal device of operator A moves from the second area to the first area, it determines that the PLMN ID of the current service is PLMN ID (XX) (that is, the access network device adopts scheme 3 to broadcast the PLMN ID). At this time, the source access network device determines that the home network information of the terminal device is the network of operator A based on the SUPI number segment of the terminal device. The PLMN ID of operator A in the network of operator A is PLMN ID (A), and at this time the source AMF determines that the first PLMN ID is 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 that the target PLMN ID is PLMN ID (A) based on the PLMN list.

In another example, after the terminal device of operator A accesses the access network device and AMF of operator X, the AMF of operator X will send a PLMN list to the terminal device according to at least one of the service PLMN ID of the terminal device, the number segment of the terminal device, and the location information of the terminal device. When the terminal device is at the boundary of the first area and the second area, the AMF of operator X sends an EPLMN list containing PLMN ID (A). When the terminal device is at the boundary of the second area and the third area, the AMF of operator X sends an EPLMN list containing PLMN ID (YA).

The above is merely an exemplary description, and the implementation methods of the process of moving the terminal device between other areas will not be elaborated on.

Method 3.2: The source AMF determines the target PLMN ID according to the mobility restriction list sent by the source AMF.

Determine the location information of the terminal device, and 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. The source AMF determines the PLMN ID of the second PLMN network that allows the terminal device to access the network; the source AMF determines that the PLMNID that allows the terminal device to access the network is 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.

The mobility restriction list is used to indicate a first PLMN ID; the first PLMN ID is a PLMN ID of a home network of the terminal device in the second PLMN network;

In one example, when the terminal device of operator A moves from the second area to the first area, the source AMF determines that the neighboring network of operator X at the current location is the network of operator A. The PLMN ID in the network of operator A that allows the terminal device to access the 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 through the mobility restriction list. The source access network device determines PLMN ID (A) as the target PLMN ID. In another example, the AMF of operator X sends a mobility restriction list to the terminal device of operator A, instructing the terminal device to give priority to the 5G NR access technology of PLMNID (A) and the 5G NR access technology of PLMN ID (YA). AMF can send a mobility restriction list according to TA. When the terminal device is at the boundary of the first area and the second area, the terminal device is instructed to give priority to the 5G NR access technology of PLMN ID (A). At the boundary of the second area and the third area, the terminal device is instructed to give priority to the 5G NR access technology of PLMN ID (YA).

The above is merely an exemplary description, and the implementation methods of the process of moving the terminal device between other areas will not be elaborated on.

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.

For example, when the access network device of operator X broadcasts the same PLMN ID PLMNID (XX) to the terminal device of operator A (for example, the above solution 3), when the terminal device of operator A moves from the second area to the first area, the access network device of operator X can indicate to the AMF of operator X that the target PLMN ID is PLMN ID (A) based on the current service PLMN ID (XX) of the terminal device and the PLMN list issued by the source AMF.

The specific implementation method of method 4 can refer to the above method 3.1, which will not be repeated here.

The above is merely an exemplary description, and the implementation methods of the process of moving the terminal device between other areas will not be elaborated on.

Method 5: The source access network device selects the target PLMN ID based on the current service PLMN ID of the terminal device and the mobility restriction list issued by the source AMF.

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

The specific implementation method of method 5 can refer to the above method 3.2, which will not be repeated here.

The above is merely an exemplary description, and the implementation methods of the process of moving the terminal device between other areas will not be elaborated on.

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

In scenario 3, the interconnection and interaction between access network equipment and core network equipment of different operators include the following scenarios 1 to 3.

Case 1: The access network equipment and core network equipment of different operators support connection-state redirection parameters.

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

Case 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) allocated to the terminal device by the source PLMN network. The signaling in the process of the target AMF discovering the source AMF can be forwarded through the secure signaling gateway.

Case 2: AMF quality inspection of different operators supports interfaces and parameters for connection-state redirection.

Specifically, it includes: Case 2.1, operators sharing the core network support the interconnection interface N14+, which can be isolated by a secure signaling gateway.

Case 2.2: The target AMF can obtain the SUPI and terminal device context of the terminal device from the source AMF through the N14+ interface. The target AMF can create a context for the terminal device based on the obtained SUPI and terminal device context, and notify the source AMF of the result after the creation is completed.

Case 2.3: The target AMF obtains the access and mobility data of the terminal device, the context information of the terminal device, SMF information, etc. from the source AMF through the N14+ interface across the PLMN. In this way, the target AMF does not need to obtain the subscription data of the terminal device from the UDM, which not only ensures the IP address of the terminal device and the continuity of the service, but also optimizes the process and reduces the pressure on the UDM.

Case 2.4: The access network device can indicate the change of the PLMN ID of the serving PLMN to the terminal device through 5G-GUTI.

Case 3: Network elements such as source access network equipment, source AMF, source SMF, source UPF, target access network equipment, target AMF, target SMF, and target UPF can support the redirection signaling process under the connected core network shared architecture.

In the above, in combination with Scenario 1 and Scenario 3, the terminal equipment, access network equipment and core network equipment in the communication system of this application need to perform corresponding action processes and realize corresponding functions.

FIG4 is a schematic diagram of the structure of another communication system 40 provided in an embodiment of the present application. As shown in FIG4, the communication system provided in an embodiment of the present application includes: a terminal device 401, a source access network device 402, a source access and mobility management function AMF403, a target AMF404, and a target access network device 405; the source access network device 402 and the source AMF403 belong to a first public land mobile network PLMN network; the target AMF404 belongs to a second PLMN network; the source AMF403 and the target AMF404 are connected via a communication interface; the source access network device 402 is used to determine the frequency information of the target access network device 405 and send the frequency information to the terminal device 401; the terminal device 401 is used to determine the target access network device 405 according to the frequency information The target access network device 405 is used to forward the redirection request to the target AMF404; the target AMF404 is used to determine the first GUTI of the terminal device 401, determine the source AMF403 according to the first GUTI, and send a session information request message to the source AMF403; the source AMF403 is used to send the session information of the terminal device 401 to the target AMF404 in response to the session request message.

The above technical solution brings at least the following beneficial effects: in the communication system provided by the present application, the source AMF and target AMF of different operators communicate through a communication interface (exemplarily, the communication interface can be an N14+ interface). When the terminal device is redirected from the first PLMN network to the second PLMN network, the source access network device indicates the frequency of the target access network device to the terminal device by discovering the frequency of the target access network device, so that the terminal device can access the target access network device according to the frequency information. The target AMF discovers the source AMF according to the GUTI of the terminal device, and obtains the session information of the terminal device 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 session information of the terminal device, so that the terminal device can be redirected to the second PLMN network. Thereby, the redirection of the connected terminal device between the networks of multiple operators is realized.

In a possible implementation, the source access network device 402 is specifically used to: determine the target PLMD identification ID; the target PLMN ID is the PLMN ID required to be selected when the terminal device 401 accesses the second PLMN network; 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.

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

In a possible implementation manner, the target AMF 404 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 the GUAMI is the source AMF 403.

In a possible implementation, the source AMF 403 is further used 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 service PLMN, the equivalent public land mobile network EPLMN, and the PLMN selected last time; the source access network device 402 is further used to determine the target PLMN from the PLMN list.

In one possible implementation, the source access network device 402 is specifically used to: determine the current service PLMN ID of the terminal device 401 according to the PLMN list; determine the home network of the terminal device 401 according to the service PLMN ID of the terminal device 401; determine that the PLMN ID of the home network of the terminal device 401 in the second PLMN network is the first PLMN ID; and determine that the first PLMN ID is the target PLMN ID.

In a possible implementation, the source AMF 403 is further used 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 used to receive the mobility restriction list and determine that the first PLMN ID indicated by the mobility restriction list is the target PLMN ID.

In a possible implementation, the source AMF403 is specifically used to: determine the location information of the terminal device 401; determine 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; determine the PLMN ID in the second PLMN network that allows the terminal device 401 to access the network; determine that the PLMN ID that allows the terminal device 401 to access the network is the first PLMN ID.

In a possible implementation, the source access network device 402 is further configured to: determine an 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 frequency information of the target access network device 405 .

In a possible implementation, the target access network device 405 is also used to: obtain the target PLMN ID, the location information of the terminal device 401, and the slice information requested by the terminal device 401; determine the target AMF404 based on the target PLMN ID, the location information of the terminal device 401, and the slice information requested by the terminal device 401.

In a 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, and the first slice information is the slice information of the terminal device 401 in the home network.

In a possible implementation, the source AMF403 is specifically used to: determine the first slice information when the PLMNID of the source AMF403 is different from that of the target AMF404; and generate a first slice indication message according to the first slice information.

In a possible implementation, the first indication information is specifically used to indicate at least one of the slice information of the terminal device 401 in the first PLMN network and the slice information of the mapped terminal device 401 in the first network in the home network; the target AMF404 is specifically used to: when the first PLMN network is the home network, determine that the slice information of the terminal device 401 in the first PLMN network is the first slice information; when the first PLMN network is not the home network, determine that the slice information of the mapped terminal device 401 in the first network in the home network is the first slice information.

In a possible implementation, the target AMF404 is also used to: determine the first slice information; determine the second slice information mapped by the first slice information in the second PLMN network; determine the target session management function SMF based on the second slice information and at least one item of the location information of the terminal device 401; the target SMF is the SMF in the second PLMN network.

In a possible implementation, the target AMF404 is also used 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 the 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 also used to release the preset session in response to the registration status update message.

In a possible implementation, the system further comprises: a home unified data management function UDM406; a target AMF404, further configured to send a context request message to the home UDM406; the context request message is used to request the UDM406 for the subscription data of the terminal device 401; the UDM406, configured to respond to the context request message and send the subscription data of the terminal device 401 to the target AMF404. 17. The system according to claim 15, characterized in that the target AMF404 is further configured to obtain the subscription data of the terminal device 401 from the source AMF403 through the communication interface.

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

In a possible implementation, the target AMF404 is also used to query the slice mapping relationship configured in the target AMF404 according to the first slice information, determine the second slice information, and the AMF list supporting the second slice information.

In a possible implementation, the system also includes: a first AMF; a target AMF404, and is also used to: determine whether the target AMF404 is included in the AMF list; the first AMF is the AMF in the AMF list; if not included, determine the first AMF according to the AMF list.

In a possible implementation, the target AMF404 is also used to send first indication information to the target access network device 405, and the first indication information includes at least one of the following: an identifier of the first AMF, a registration request message, and second slice information; the target access network device 405 is used 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: an identifier of the first AMF, a registration request message, and second slice information; the first AMF is used 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.

In a possible implementation, the target AMF404 is also used 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 pole device, the context of the terminal device 401, and the second slice information; the first AMF is used 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.

In a possible implementation, the system also 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.

In a possible implementation, the target AMF 404 is further used to send fifth indication information to the target access network device 405, where the fifth indication information is used to indicate at least one item in the PLMN list and the mobility restriction list.

The above describes the interaction process of each network element in a communication system provided by an embodiment of the present application. In addition, an embodiment of the present application also provides a communication method for implementing the redirection of a connected terminal device between networks of multiple operators.

As shown in FIG5 , a communication method is also provided for the embodiment of the present application, which can be applied to any communication system in FIG2 to FIG4 . As shown in FIG5 , the method includes:

S501. A source access network device determines frequency information of a target access network device.

In one possible implementation, the source access network device determines the target PLMN identification 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.

It should be noted that the process of the source access network device determining the frequency information of the target access network device can be understood by referring to the process of the source access network device selecting the target PLMN ID and the frequency of the target access network device in the above scenario 2, and will not be repeated here.

S502: The source access network device sends frequency information to the terminal device. Correspondingly, the terminal device receives the frequency information from the source access network device.

S503: The terminal device determines the target access network device according to the frequency information.

In a possible implementation, the terminal device searches for signals sent by various access network devices, and selects an access network device whose signal frequency information is the same as the above frequency information as the target access network device.

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.

The redirection request includes the first GUTI of the terminal device; the first GUTI is the GUTI of the terminal device in the first PLMN network.

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 allocated by the first PLMN network to the terminal device, the TAI of the terminal device in the first PLMN network, the PDU session list that the terminal device needs to activate, and the NSSAI requested by the terminal device.

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.

In a possible implementation, the target access network device selects a target AMF based on the PLMN ID selected by the terminal device to access the target access network device (that is, the above-mentioned target PLMN ID), the TAI of the terminal device in the first PLMN network, and the NSSAI requested by the terminal device. After selecting the target AMF, the redirection request is forwarded to the target AMF.

S506. The target AMF determines the source AMF according to the redirection request.

In a possible implementation, the target AMF parses the redirection request to determine the first GUTI carried in the redirection request. The target AMF parses the first GUTI to determine 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.

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.

Optionally, the session request message is: Namf_Communication_UEContextTransferRequest. The message carries a NAS message complete Registration Request.

The session request message is used to request the source AMF to obtain the SUPI (i.e. IMSI) of the terminal device and the context information of the terminal device. The context information of the terminal device includes: AUSF\PCF\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 HPLMN and the corresponding HPLMN.

S508. The source AMF sends the session information of the terminal device to the target AMF.

Optionally, the above session request message is: Namf_Communication_UEContextTransferResponse. The message carries SUPI, UE Context, SMF information, DNN(s), source NSSAI(s) and PDUSession ID(s).

After receiving the session information, the target AMF creates a context for the terminal device in the second PLMN network according to the session information.

It should be noted that in the above process, the source AMF needs to indicate the slice information of the terminal device in the home network (recorded as the first slice information) to the target AMF, so that the target AMF maps the slice information of the terminal device in the second PLMN network (recorded as the second slice information) according to the first slice information. Among them, the source AMF and the target AMF can indicate the first slice information and determine the second slice information in the following manner, which is described in detail below:

Method 1: The source AMF adds a new cell message in the session request message to indicate the first slice information.

When the source AMF sends the 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 not the same, a first information element message (for example, 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 information element message, and determines the first slice information according to the first information element message.

Exemplarily, the first cell message is carried in UeContex object>MmContext->allowedHomeNssai.

Method 2: The source AMF indicates the first slice information according to the original information element of the session request message, and the target AMF parses different information elements from the session request message to determine the first slice information according to different mobile scenarios of the terminal device.

Specifically, the session request message 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 in the home network mapped in the first network.

The target AMF parses the session request message according to different mobile scenarios of the terminal device to determine the first slice information.

When the first PLMN network is the home network, the target AMF determines that the slice information of the terminal device in the first PLMN network is the first slice information.

In one example, the source AMF passes the slice information to the target AMF through UeContextTransferRspData->UeContex target>MmContex target>allowedNssai in Namf_Communication_CreateUEContext, and the target AMF regards allowedNssai as the first slice information.

When the first PLMN network is not the home network, the target AMF determines that the slice information of the terminal device mapped in the first network in the home network is the first slice information.

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

The above technical solution brings at least the following beneficial effects: in the communication system provided by the present application, the source AMF and target AMF of different operators communicate through a communication interface (exemplarily, the communication interface can be an N14+ interface). When the terminal device is redirected from the first PLMN network to the second PLMN network, the source access network device indicates the frequency of the target access network device to the terminal device by discovering the frequency of the target access network device, so that the terminal device can access the target access network device according to the frequency information. The target AMF discovers the source AMF according to the GUTI of the terminal device, and obtains the session information of the terminal device 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 session information of the terminal device, so that the terminal device can be redirected to the second PLMN network. Thereby, the redirection of the connected terminal device between the networks of multiple operators is realized.

The communication method provided in the embodiments of the present application is described above in detail.

It should be noted that the communication method provided in the embodiment of the present application has different redirection processes in different scenarios. For example, in combination with the above-mentioned Figure 3, the mobile scenarios of the terminal device in the present 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.

The following describes the redirection process in the communication method provided in the embodiment of the present application in combination with the above-mentioned scenarios 4 to 6 respectively:

Scenario 4: The terminal device moves from the first area to the second area

As shown in FIG6 , when the terminal device moves from the first area to the second area, the redirection process of the terminal device includes the following steps:

S601. The source access network device sends a context release request to the source AMF.

Optionally, UE Context Release Request, cause = redirection, instructs the source AMF of operator A to release the terminal device context due to redirection, and carries a list of PDU sessions activated by the terminal device.

When the source access network device initiates the terminal device context release process to the source AMF, it will send an AN Connectiong Release message to the terminal device, indicating the redirected frequency point, that is, the NR frequency F2 of operator X (the NG-RAN and 5GC selection function of the target PLMN-ID and frequency described in the first part above).

S602: The source access network device releases the context.

Specifically including: S602a, the source AMF of operator A sends to the source access network device: UE Context Release Command

S602b, the source access network device replies to the source AMF: UE Context Release Complete.

S603: The terminal device sends a mobility registration update request to the target access network device.

Optionally, the mobility registration update request is: Registration Request. The mobility registration update request carries the 5G-GUTI assigned by operator A to the terminal device, the list of PDU sessions that need to be activated in operator A's TAI, and the requested NSSAI (the 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).

S604. The target access network device selects a target AMF.

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

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

S606. The target AMF discovers the source AMF.

In a possible implementation, the target AMF discovers the source AMF based on the 5G-GUTI allocated by operator A to the terminal device. The 5G-GUTI includes the GUAMI of the source AMF. The target AMF discovers the source AMF based on the GUAMF.

Specifically including: S606a, the target AMF sends to the source AMF: Namf_Communication_UEContextTransferRequest.

The Namf_Communication_UEContextTransfer Request carries: NAS message completeRegistration Request, the target AMF obtains the SUPI (i.e. IMSI) and context of the terminal device from the source AMF, the context includes the AUSF\PCF\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, the Allowed NSSAI in the HPLMN and the corresponding HPLMN, etc. It should be pointed out 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: request PLMN), and the target PLMN is the PLMN ID carried in the GUAMI of the terminal device.

S606b. The source AMF sends Namf_Communication_UEContextTransferResponse to the target AMF.

Namf_Communication_UEContextTransfer Response carries SUPI, UE Context, SMFinformation, DNN(s), source NSSAI(s) and PDU Session ID(s).

After the target AMF receives the context of the terminal device from the source AMF, it creates a context for the terminal device.

It should be noted that in S603, the target AMF needs to map slice resources for the terminal device in the target network according to the slice resources of the terminal device in the home network. The specific method can refer to method 1 and method 2 in the above S508, which will not be repeated here.

S607: A security process is performed between the terminal device and the AUSF.

S608. The target AMF sends a registration status update message to the source AMF.

Optionally, the registration status update message is: Namf_Communication_RegistrationStatusUpdate. The registration status update message carries: PDU Session ID(s). The target AMF notifies the source AMF through this message that the registration of the terminal device in the target AMF has been completed. For slices and sessions that the target AMF cannot support (based on network capabilities and network sharing agreements), the target AMF notifies the source AMF in this message, and the source AMF initiates the release process for the unsupported sessions. In the message, transferStatus: is set to "Transferred", carrying the PDU Session ID list transferred to the target AMF.

S609: The target AMF discovers the belonging UDM.

Optionally, the target AMF discovers the process of the home UDM through the secure signaling gateway between the networks based on SUPI.

S610. The target AMF obtains context information of the terminal device.

Specifically including: S610a, the target AMF sends a context registration message to the home UDM.

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

S610b, the target AMF sends Nudm_SDM_Get to the home UDM. Through this message, the target AMF obtains the subscription data of the terminal device from the home UDM, including access and mobility data, SMF selection migration data, context data of the terminal device in SMF, etc., and the UDM replies with a response message.

The target AMF obtains the access and mobility data of the terminal device, the context information of the terminal device, SMF information, etc. from the source AMF through the N14+ interface across the PLMN, without obtaining the subscription data of the terminal device from the UDM.

On the one hand, it provides IP addresses and business continuity, and on the other hand, it optimizes the process and reduces the pressure on UDM.

S610c, the target AMF sends Nudm_UECM_Subscribe to the home UDM. The vAMF uses this process to subscribe to the notification of the home UDM, and the home UDM replies with a response.

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

S610e. The source AMF sends a message to the affiliated UDM: Nudm_SDM_unsubscribe to cancel the subscription to the affiliated UDM notification message.

S611. The target AMF discovers the target SMF.

Optionally, the target AMF initiates a target SMF (shared SMF) discovery process. The target AMF can discover the target SMF through the location information and slice information of the terminal device.

Specifically including: S611a, the target AMF obtains the mapped slice information.

Specifically, it includes the following situation A and situation B, which are described in detail below.

Case A: The target AMF determines the mapped slice information by querying the target NSSF.

Specifically: the target AMF queries the target NSSF according to the allowedHomeNssai obtained in S606 to obtain the mapped NSSAI, including Allowed NSSAI, Configed NSSAI, mapped Allowed NSSAI, Mapped ConfigedNSSAI, etc., as well as the AMF SET that supports the above mapped NSSAI.

Case B: The target AMF determines the mapped slice information by querying the local configuration.

Specifically, the target AMF obtains the mapped slice and the AMFSET that supports the mapped slice according to the local configuration of the target AMF.

S611b. If the current target AMF cannot support the mapped slices, reselect the target AMF.

Specifically, when the target AMF does not belong to an NF in the AMF SET returned by the NSSF, or the local configuration of the target AMF cannot support the mapping slice, the target AMF determines that it is necessary to reselect the AMF and sends the slice information to the reselected AMF after the reselection.

The method of the target AMF sending slice information to the reselected target AMF includes the following case C and case D, which are described in detail below.

Case C: The target AMF sends slice information to the reselected target AMF through the target access network device.

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

(2) The target access network device sends an Initial UE message to the target AMF, including the slice information obtained from the initial target AMF.

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

Specifically, it includes: the initial target AMF directly forwards the NAS message to the target AMF of the target; the initial target AMF directly sends the Namf_Communication_N1MessageNotify message to the target AMF of the target, carrying the Registration Request message, the SUPI of the terminal device, the MM Context of the terminal device, the slice mapping information, etc.

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

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 S606, UE location info, Access Type, RAT Type, Operation Type, where the SMContext ID points to the source SMF, and the target AMF sets the Operation Type to "UP activate", indicating that the N3 tunnel of the user plane is established for the PDUSession(s).

S613: The target SMF determines the PDU session context.

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

S613b. The source SMF determines the PDU session context information of the terminal device according to the SM Context ID, and sends a response to the target SMF.

S614. The target SMF selects a target UPF.

S615. The target SMF initiates the N4 session establishment process to the target UPF.

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

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, SM ContextID of the target SMF, Access Type, RAT type).

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

S617. The source SMF performs N4 session modification.

Specifically including: S617a, the source SMF initiates the SM policy management process to the PCF, and notifies the PCF of the location information of the terminal device.

S617b. The source SMF initiates the N4 session modification process to the source UPF. The source SMF provides the N9 tunnel information of the target UPF, and the source UPF allocates N9 tunnel resources.

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

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.

The downlink data channel from source UPF to target UPF is established.

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

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), 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.

S620. The target AMF sends an initial context request to the target access network device.

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, a mobility restriction list, a frequency priority, and an equivalent PLMN list for assisting the terminal device in selecting a PLMN-ID.

The target access network device allocates a RAN tunnel for the PDU session and allocates QoS resources for the PDU session.

The uplink data channel from the terminal device to the target UPF to the source UPF is established.

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

S621. The terminal device sends a registration completion message to the target AMF.

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

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

S622. The target AMF sends a PDU session context update request to the target SMF.

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 the N2 SM information received by the target AMF from step 17.

S623. The target SMF performs N4 session modification.

Specifically, the target SMF initiates the N4 session modification process to the target UPF. In the session modification process, the target SMF sends AN Tunnel information to the target UPF, and the downlink channel from the target UPF to the target access network device to the terminal device is established.

S624: The target SMF updates the PDU session context.

Specifically including: S624a, the target SMF sends to the source SMF: Nsmf_PDUSession_Update request (RATtype, Access type), and the source SMF updates the PDU Session.

S624b. The source SMF replies to the target SMF: Nsmf_PDUSession_Update Response.

The target SMF replies to the target AMF: Nsmf_PDUSession_UpdateSMContext Response.

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

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

The above describes in detail the redirection process of the terminal device when the scenario 4 moves from the first area to the second area.

It should be noted that the movement of the terminal device from the first area to the second area in the above scenario 4 is only an exemplary description. The above process is applicable to various scenarios where the terminal device moves from the home network to the shared network (for example, the terminal device moves from the first area to the third area), and the implementation process is similar in other scenarios. This application does not limit this.

The following describes in detail the redirection process of the terminal device when the terminal device moves from the second area to the first area in scenario 5.

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

As shown in FIG7 , when the terminal device moves from the second area to the first area, the redirection process of the terminal device includes the following steps:

S701. The source access network device sends a context release request to the source AMF and releases the context.

Specifically including: S701a, the source access network device sends a context release request to the source AMF.

Optionally, UE Context Release Request, cause = redirection, instructs the source AMF of operator A to release the terminal device context due to redirection, and carries a list of PDU sessions activated by the terminal device.

When the source access network device initiates the terminal device context release process to the source AMF, it will send an AN Connectiong Release message to the terminal device, indicating the redirected frequency point, that is, the NR frequency F1 of operator A.

S701b. The source AMF sends a UE Context Release Command to the source access network device.

S701c. The source access network device replies to the source AMF: UE Context Release Complete.

S702: The terminal device sends a mobility registration update request to the target access network device.

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

The target access network device forwards the mobility registration update request of the terminal device to the target AMF.

S703. The target access network device selects the target AMF.

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

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

S705. The target AMF discovers the source AMF.

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

S706. The target AMF obtains the context information of the terminal device.

Specifically including: S706a, the target AMF sends a context request message to the source AMF.

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 SUPI (i.e., IMSI) of the terminal device and the context of the terminal device from the source AMF. For the inter-PLMN mobility process, the UE Context includes the Allowed NSSAI in the HPLMN and the corresponding HPLMN.

S706b. The source AMF sends a context response message to the target AMF.

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 PDUSession ID(s).

After the target AMF receives the context of the terminal device from the source AMF, it creates a context for the terminal device.

S707: A security process is performed between the terminal device and the AUSF.

S708. The target AMF sends a registration status update message to the source AMF.

Optionally, the registration status update message is: Namf_Communication_RegistrationStatusUpdate. The registration status update message carries: PDU Session ID(s). The target AMF notifies the source AMF through this message that the registration of the terminal device in the target AMF has been completed. For slices and sessions that the target AMF cannot support (based 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 transferStatus: "Transferred" carries the PDUSession ID list transferred to the target AMF. The target AMF determines that the terminal device has returned to the home network, and indicates in the message to delete the source SMF and UPF.

S709: The target AMF discovers the belonging UDM.

Optionally, the target AMF discovers the process of the home UDM through the secure signaling gateway between the networks based on SUPI.

S710. The target AMF obtains context information of the terminal device.

Specifically including: S710a, the target AMF sends a context registration message to the home UDM.

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

S710b. The target AMF obtains the contract data through Nudm_SDM_Get (optional step).

Through this message, v-AMF obtains the contract data of the terminal device from hUDM, including access and mobility data, SMF selection migration data, context data of the terminal device in SMF, etc., and UDM replies with a response message.

The target AMF obtains the access and mobility data of the terminal device, the context information of the terminal device, SMF information, etc. from the source AMF through the N14 interface across the PLMN, without obtaining the subscription data of the terminal device from the UDM.

On the one hand, it provides IP addresses and business continuity, and on the other hand, it optimizes the process and reduces the pressure on UDM.

S710c. The target AMF subscribes to the contract data change notification service through Nudm_SDM_Subscribe.

S710d, the home UDM sends Nudm_UECM_DeregistrationNotify to the source AMF. According to S710a, the target AMF is registered with the home UDM, and the home UDM notifies the source AMF to deregister. The source AMF sets a relevant timer and deletes the context information of the terminal device after the timer expires.

S711. The target AMF sends a PDU session creation request to the target SMF.

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, Userlocation information.

The specific implementation steps of S711 can refer to the above S611 and will not be repeated here.

S712. The home SMF requests a session context.

Specifically, S712a, the home SMF sends a session context request to the source SMF.

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 obtains SMContext from the source SMF.

S712b. The target SMF initiates the SM policy management process to the PCF and notifies the PCF of the location information of the terminal device.

S712c. The source SMF sends a session context reply response message to the target SMF.

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

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

Optionally, the N4 session modification request is: N4 Session Modification Request. The N4 session modification request includes: forwarding parameters. The home UPF replies to the home SMF: N4 session modification response, creates CN TunnelInfo, TEID and IP of UP.

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

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

The downlink user plane from the UPF to the target access network device is established.

S715. The target AMF sends a registration acceptance message to the terminal device.

Optionally, the registration accept message is: Registration Accept. The registration accept message is used to notify the terminal device that the registration request has been received. The registration accept message contains the allocated 5G-GUTI, a mobility restriction list, frequency priority, equivalent PLMN list, etc. that assist the terminal device in selecting PLMN-ID, 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.

The uplink user plane from the terminal device to the target access network device to the affiliated UPF is established.

S716. The terminal device sends a registration completion message to the target AMF.

Optionally, the registration completion message is: Registration Complete.

S717. The source AMF initiates the PDU session release process to the source SMF.

Specifically including: S717a, the source AMF sends Nsmf_PDUSession_ReleaseSMContextRequest to the source SMF, indicating that only the session resources of the source SMF should be released.

S717b. The source SMF replies: Nsmf_PDUSession_ReleaseSMContext Response.

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

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, UE Location.

S719. The target SMF initiates the SM policy management process to the PCF.

The SM policy management process is used to notify the PCF of the location information of the terminal device. The home SMF initiates an N4Session modification request to the home UPF and updates the home network RAN SM N3 forwarding Informationlist to the home UPF. The home UPF 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.

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.

S721. After the timer times out, the source SMF releases the resources of the source UPF.

The above describes in detail the redirection process of the terminal device when the scenario 5 moves from the second area to the first area.

It should be noted that the movement of the terminal device from the second area to the first area in the above scenario 5 is only an exemplary description. The above process is applicable to various scenarios where the terminal device moves from the home network to the shared network (for example, 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 this.

The following describes in detail the redirection process of the terminal device when the terminal device moves from the second area to the third area in scenario 6.

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

As shown in FIG8 , when the terminal device moves from the second area to the third area, the redirection process of the terminal device includes the following steps:

S801. The source access network device sends a context release request to the source AMF.

Optionally, UE Context Release Request, cause = redirection, instructs the source AMF of operator A to release the terminal device context due to redirection, and carries a list of PDU sessions activated by the terminal device.

When the source access network device initiates the terminal device context release process to the source AMF, it will send an AN Connectiong Release message to the terminal device, indicating the redirected frequency point, that is, the NR frequency F3 of operator Y.

S802: The source access network device releases the context.

Specifically including: S802a, the source AMF sends to the source access network device: UE Context Release Command

S802b. The source access network device replies to the source AMF: UE Context Release Complete.

S803: The terminal device sends a mobility registration update request to the target access network device.

Optionally, the mobility registration update request is: Registration Request. The mobility registration update request carries the 5G-GUTI allocated by operator X to the terminal device, the TAI of operator X of the terminal device, the PDU session list to be activated, and the requested NSSAI.

S804. The target access network device selects a target AMF.

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

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

S806. The target AMF discovers the source AMF.

In one possible implementation, the target AMF discovers the source AMF based on the 5G-GUTI allocated to the terminal device by operator A. The 5G-GUTI includes the GUAMI of the source AMF. The target AMF discovers the source AMF based on the GUAMF.

Specifically, S806a, the target AMF sends to the source AMF: Namf_Communication_UEContextTransferRequest. The Namf_Communication_UEContextTransfer Request carries: NAS message completeRegistration Request. The target AMF obtains the SUPI (i.e., IMSI) and the context of the terminal device from the source AMF. The UE Context includes the AUSF\PCF\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, the Allowed NSSAI in the HPLMN and the corresponding HPLMN.

S806b. The source AMF replies to the target AMF: Namf_Communication_UEContextTransfer Response. This message carries SUPI, UE Context, SMF information, DNN(s), source NSSAI(s) and PDU Session ID(s).

After the target AMF receives the context of the terminal device from the source AMF, it creates a context for the terminal device.

S807: A security process is performed between the terminal device and the AUSF.

S808. The target AMF sends a registration status update message to the source AMF.

Optionally, the registration status update message is: Namf_Communication_RegistrationStatusUpdate. The registration status update message carries: PDU Session ID(s). The target AMF notifies the source AMF through this message that the registration of the terminal device in the target AMF has been completed, and carries the PDU Session ID list transferred to the target AMF. For policies, slices and sessions that the target AMF cannot support (based on network capabilities and network sharing agreements), the target AMF notifies the source AMF in this message, and the source AMF initiates the release process for the unsupported sessions.

S809: The target AMF discovers the belonging UDM.

Optionally, the target AMF discovers the process of the home UDM through the secure signaling gateway between the networks based on SUPI.

S810. The target AMF obtains context information of the terminal device.

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

S810b, the target AMF sends Nudm_SDM_Get to the home UDM. Through this message, the target AMF obtains the subscription data of the terminal device from the home UDM, including access and mobility data, SMF selection migration data, context data of the terminal device in SMF, etc., and the UDM replies with a response message.

The target AMF obtains the access and mobility data of the terminal device, the context information of the terminal device, SMF information, etc. from the source AMF through the N14+ interface across the PLMN, without obtaining the subscription data of the terminal device from the UDM.

On the one hand, it provides IP addresses and business continuity, and on the other hand, it optimizes the process and reduces the pressure on UDM.

S810c. The target AMF sends Nudm_UECM_Subscribe to the home UDM. The vAMF uses this process to subscribe to the notification of the home UDM, and the home UDM replies with a response.

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

S810e. The source AMF sends a message to the affiliated UDM: Nudm_SDM_unsubscribe to cancel the subscription to the affiliated UDM notification message.

S811. The target AMF discovers the target SMF.

Optionally, the target AMF initiates a target SMF (shared SMF) discovery process. The target AMF can discover the target SMF through the location information and slice information of the terminal device.

It should be noted that the specific implementation process of S811 can refer to the above S611 and will not be repeated here.

S812. The target AMF sends a PDU session context creation request to the target SMF.

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, Operation Type. Among them, SMContext ID points to the home SMF, and the target AMF sets the Operation Type to "UP activate", indicating that the N3 tunnel of the user plane is established for the PDUSession(s).

S813. The target AMF determines the PDU session context.

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

S813b. The home SMF determines the PDU session context information of the terminal device according to the SM Context ID, and sends a response to the shared SMF.

S814, target SMF selects target UPF

S815. The target SMF initiates the N4 session establishment process to the target UPF.

S816. The target SMF creates a PDU session.

Specifically including: S816a, the target SMF sends a PDU session creation request to the source SMF.

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 (tunnel endpoints f) of the downlink buffer data to be buffered.

S816b, the source SMF sends to the source UPF: N4 session modification, and sends the tunnel information of the downlink buffer data allocated by the target SMF to the source UPF, thereby establishing a forwarding channel for the downlink buffer data from the source UPF to the target UPF.

S816c. The source SMF replies to the target SMF: Nsmf_PDUSession_Update Response.

S817. The target SMF updates the PDU session.

Specifically including: S817a, the target SMF sends to the home SMF: Nsmf_PDUSession_Update Request (SMContext ID, downlink tunnel information of the target UPF, SM Context ID of the target SMF, Access Type, RATtype), the shared SMF initiates the session establishment process 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.

S817b. The home SMF initiates the SM policy management process to the PCF and notifies the PCF of the location information of the terminal device.

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

S817d. The home SMF sends Nsmf_PDUSession_Update Response to the target SMF.

The downlink data channel from the home UPF to the target UPF is established, the home UPF stops sending the downlink cache data to the source UPF, generates an END-MARKER to the source UPF and sends it to the target UPF. The target UPF starts the timer after receiving the END-MARKER, and releases the indirect forwarding channel after the timer expires.

S818. The target SMF sends a PDU session context creation response to the target AMF.

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.

The target SMF sets a timer and releases the indirect forwarding channel for the downstream buffered data after the timer expires.

S819. The target AMF sends an initial context request to the target access network device.

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, carrying the mobility restriction list, frequency priority, equivalent PLMN list, etc. for assisting the terminal device to select PLMN-ID.

The wireless network allocates a RAN tunnel for the PDU session and allocates QoS resources for the PDU session.

The uplink data channel from the terminal device to the target UPF to the belonging UPF is established.

S820. The terminal device sends a registration completion message to the target AMF.

Optionally, the registration completion message is: Registration Complete.

S821. The source AMF releases the PDU session context.

Specifically including: S821a, the source AMF sends a PDU session context release request to the source SMF.

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 is released and the PDU session context of the belonging SMF cannot be released.

When the source AMF's timer expires, the terminal device context is deleted and the session resources are released. The source SMF sets a timer and releases the source UPF's indirect forwarding channel resources after the timer expires.

S821b. The source SMF sends a PDU session context release response to the source AMF.

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.

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 S820.

S823. The target SMF performs N4 session modification.

Specifically, the target SMF initiates the N4 session modification process to the target UPF. In the session modification process, the target SMF sends AN Tunnel information to the target UPF, and the downlink channel from the target UPF to the target access network device to the terminal device is established.

S824. The target SMF updates the PDU session context.

Specifically including: S824a, the target SMF sends to the belonging SMF: Nsmf_PDUSession_Update request (RATtype, Access type), and the belonging SMF updates the PDU Session.

S824b. The home SMF replies to the V-SMF: Nsmf_PDUSession_Update Response.

S825. The shared SMF sends a PDU session context update response to the target AMF.

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

S826. The target SMF and the source SMF release the indirect forwarding channel.

Specifically including: 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.

S826b. After the timer in S821 expires, the source SMF initiates the N4 session modification process to the source UPF to release the indirect forwarding channel.

The above describes in detail the redirection process of the terminal device when the scenario 6 moves from the second area to the third area.

It should be noted that the movement of the terminal device from the second area to the third area in the above scenario 6 is only an exemplary description. The above process is applicable to various scenarios where the terminal device moves from one shared network to another shared network (for example, the terminal device moves from the third area to the second area), and the implementation process is similar in other scenarios. This application does not limit this.

It should be pointed out that in Scenario 5 and Scenario 6, there are steps that are the same or similar to those in Scenario 4. For understanding of the above-mentioned same or similar steps, please refer to the description in the above-mentioned Scenario 4, and this application will not elaborate on this.

It can be seen that the technical solution provided by the embodiment of the present application is introduced above mainly from the perspective of the method. In order to realize the above functions, it includes hardware structures and/or software modules corresponding to the execution of each function. Those skilled in the art should be easily aware that, in combination with the modules and algorithm steps of each example described in the embodiment disclosed herein, the embodiment of the present application can be implemented in the form of hardware or a combination of hardware and computer software. Whether a function is executed in the form of hardware or computer software driving hardware depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to exceed the scope of the present invention.

The embodiment of the present application can divide the functional modules of the communication device according to the above method example. For example, each functional module can be divided according to each function, or two or more functions can be integrated into one processing module. The above integrated module can be implemented in the form of hardware or in the form of software functional modules. Optionally, the division of modules in the embodiment of the present application is schematic and is only a logical function division. There may be other division methods in actual implementation.

As shown in FIG9 , it is a schematic diagram of the structure of a communication device provided in an embodiment of the present application. The device includes: a communication unit 901 and a processing unit 902 .

Communication unit 901 and processing unit 902, communication unit 901, used for redirection request from 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; processing unit 902, used to determine the first GUTI of the terminal device according to the redirection request, and determine the source AMF according to the first GUTI; communication unit 901, also used to send a session information request message to the source AMF; communication unit 901, also used to receive session information of the terminal device from the source AMF.

Optionally, the processing unit 902 is specifically used 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; the communication unit 901 receives 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.

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 the GUAMI is the source AMF.

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.

Optionally, the communication unit 901 is also used to send a context request message to the unified data management function UDM; the context request message is used to request the UDM for the contract data of the terminal device; the target AMF receives the contract data of the terminal device from the UDM.

Optionally, the processing unit 902 is also used to instruct the communication unit 901 to obtain the contract data of the terminal device from the source AMF through the communication interface.

Optionally, the processing unit 902 is also used 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, where the first slice information is the slice information of the terminal device in the home network.

Optionally, the processing unit 902 is also used to determine whether the target AMF is included in the AMF list; the first AMF is the AMF in the AMF list; if not included, the first AMF is determined according to the AMF list.

Optionally, the communication unit 901 is also used to send a first indication message to the target access network device, so that the target access network device forwards the first AMF identifier, the registration request message, and at least one of the second slice information to the first AMF according to the first indication information.

Optionally, the communication unit 901 is also used 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 pole device, the context of the terminal device, and the second slice information.

Optionally, the communication unit 901 is further used to send fifth indication information to the target access network device, where the fifth indication information is used to indicate at least one item in the PLMN list and the mobility restriction list.

As shown in FIG. 10 , it is a schematic diagram of the structure of another communication device provided in an embodiment of the present application. The device includes: a communication unit 1001 and a processing unit 1002 .

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

Optionally, the processing unit 1002 is further used to: determine a target PLMD identification ID; the target PLMN ID is the PLMN ID required to be selected when the terminal device accesses the second PLMN network; and determine that the frequency information of the PLMN network corresponding to the target PLMN ID is the frequency information of the target access network device.

The optional communication unit 1001 is also used to receive a PLMN list from the source AMF; the PLMN list includes at least one of the following: the HPLMN of the terminal device, the service PLMN, the equivalent public land mobile network EPLMN, and the previously selected PLMN; the processing unit 1002 is also used to determine the target PLMN from the PLMN list.

Optionally, processing unit 1002 is further used to: determine the current service PLMNID of the terminal device according to the PLMN list; the source access network device determines the home network of the terminal device according to the service PLMN ID of the terminal device; determine that the PLMN ID of the home network of the terminal device in the second PLMN network is the first PLMN ID; and determine the first PLMN ID as the target PLMNID.

Optionally, the communication unit 1001 is also used to receive a mobility restriction list from a source AMF; 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 in the second PLMN network; the processing unit 1002 is also used to determine that the first PLMN ID indicated by the mobility restriction list is the target PLMN ID.

Optionally, the processing unit 1002 is further used to: determine an access network device adjacent to the source access network device in the second PLMN network as the target access network device; and determine frequency information of the target access network device.

As shown in FIG. 11 , it is a schematic diagram of the structure of another communication device provided in an embodiment of the present application. The device includes: a communication unit 1101 and a processing unit 1102 .

The processing unit 1102 is used 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 according to the first GUTI of the terminal device; the processing unit 1102 is also used 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.

Optionally, the device also includes: a processing unit 1102, which is also used 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 items: the HPLMN of the terminal device, the service PLMN, the equivalent public land mobile network EPLMN, and the previously selected PLMN.

Optionally, the processing unit 1102 is further used 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 the first PLMN ID; the first PLMN ID is the PLMN ID of the home network of the terminal device in the second PLMN network.

Optionally, the processing unit 1102 is further used 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 that the PLMN ID that allows the terminal device to access the network is the first PLMN ID.

Optionally, the device also includes: a processing unit 1102, which is also used 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, and the first slice information is slice information of the terminal device in the home network.

Optionally, the processing unit 1102 is also used 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 first network in the home network.

Optionally, the processing unit 1102 is also used 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; in response to the registration status update message, the preset session is released.

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

Through the description of the above implementation methods, technicians in the relevant field can clearly understand that for the convenience and simplicity of description, only the division of the above functional modules is used as an example. In actual applications, the above functions can be assigned to different functional modules as needed, that is, the internal structure of the network node is divided into different functional modules to complete all or part of the functions described above. The specific working process of the system, module and network node described above can refer to the corresponding process in the aforementioned method embodiment, and will not be repeated here.

An embodiment of the present application also provides a computer-readable storage medium, in which instructions are stored. When a computer executes the instructions, the computer executes each step in the method flow shown in the above method embodiment.

An embodiment of the present application provides a computer program product including instructions. When the instructions are executed on a computer, the computer executes the communication method in the above method embodiment.

An embodiment of the present application provides a chip, which includes a processor and a communication interface, wherein the communication interface is coupled to the processor, and the processor is used to run a computer program or instruction to implement a communication method as in the above method embodiment.

Among them, the computer-readable storage medium can be, for example, but not limited to, an electrical, magnetic, optical, electromagnetic, infrared, or semiconductor system, device or device, or any combination of the above. More specific examples of computer-readable storage media (a non-exhaustive list) include: an electrical connection with one or more wires, a portable computer disk, and a hard disk. Random Access Memory (RAM), Read-Only Memory (ROM), Erasable Programmable Read Only Memory (EPROM), registers, hard disks, optical fibers, portable compact disk read-only memory (CD-ROM), optical storage devices, magnetic storage devices, or any other form of computer-readable storage medium in a suitable combination of the above, or numerical values in the art. An exemplary storage medium is coupled to a processor so that the processor can read information from the storage medium and write information to the storage medium. Of course, the storage medium can also be a component of the processor. The processor and the storage medium can be located in an Application Specific Integrated Circuit (ASIC). In embodiments of the present invention, computer-readable storage media may be any tangible media that contains or stores a program that may be used by or in conjunction with an instruction execution system, apparatus, or device.

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-mentioned method, the technical effects that can be obtained can also refer to the above-mentioned method embodiments, and the embodiments of the present application will not be repeated here.

The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims (52)

1. A communication system, comprising: 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 network; the target AMF belongs to a second PLMN network; the source AMF is connected with the target AMF through a communication interface;

the source access network device is used for determining the frequency point information of the target access network device and sending the frequency point information to the terminal device;

The terminal equipment is used for determining the target access network equipment according to the frequency point information and initiating a redirection request to the target access network equipment; the redirection request comprises a first global unique temporary identifier GUTI of the terminal equipment; the first GUTI is a GUTI of the terminal device in the first PLMN network;

the target access network device is configured to forward the redirection request to the target AMF;

the target AMF is used for determining a first GUTI of the terminal equipment, determining the source AMF according to the first GUTI, and sending a session information request message to the source AMF;

the source AMF is configured to send session information of the terminal device to the target AMF in response to the session request message.

2. The system according to claim 1, wherein the source access network device is specifically configured to:

determining a target PLMD identification ID; the target PLMNID is the PLMNID which is required to be selected when the terminal equipment accesses the second PLMN network;

and determining the frequency point information of the PLMN network corresponding to the target PLMNID as the frequency point information of the target access network equipment.

3. The system of claim 1, wherein the target AMF is further configured to send a first request message to the source AMF; the first request message is used for requesting context information of the terminal equipment and a user permanent identifier SUPI;

The source AMF is used for sending a first response message to the target AMF according to the first request message; the first response message comprises the context information and SUPI of the terminal equipment;

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.

4. The system according to claim 1, wherein the target AMF is specifically configured to:

analyzing the first GUTI, and determining a globally unique AMF identifier GUAMI in the first GUTI;

and determining the AMF characterized by the GUAMI as the source AMF.

5. The system according to any of claims 2-4, wherein 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 HPLMN of the terminal equipment serves PLMN, equivalent public land mobile network EPLMN, PLMN selected in the previous time;

the source access network device is further configured to determine the target PLMN from the PLMN list.

6. The system according to claim 5, wherein the source access network device is specifically configured to:

determining the current service PLMNID of the terminal equipment according to the PLMN list;

Determining a home network of the terminal equipment according to the service PLMN ID of the terminal equipment;

determining that a PLMNID of the home network of the terminal equipment in the second PLMN network is a first PLMN ID;

and determining the first PLMN ID as the target PLMN ID.

7. The system according to any of claims 2-4, wherein the source AMF is further configured to send a mobility restriction list to the source access network device; the mobility restriction list is used for indicating a first PLMNID; the first PLMNID is the PLMNID of the home network of the terminal equipment in the second PLMN network;

the source access network device is configured to receive the mobility restriction list, and determine that the first PLMNID indicated by the mobility restriction list is the target PLMN ID.

8. The system according to claim 7, wherein the source AMF is specifically configured to:

determining location information of the terminal device,

determining that a PLMN network adjacent to the first PLMN network is the second PLMN network at a position represented by the position information of the terminal device;

determining PLMNID allowing the terminal equipment access network in the second PLMN network;

And determining the PLMNID of the access network of the terminal equipment to be the first PLMNID.

9. The system of claim 8, wherein the source access network device is further configured to:

determining that access network equipment adjacent to the source access network equipment in the second PLMN network is the target access network equipment;

and determining the frequency point information of the target access network equipment.

10. The system of claim 9, wherein the target access network device is further configured to:

acquiring the target PLMNID, the position information of the terminal equipment and the slice information requested by the terminal equipment;

and determining the target AMF according to the target PLMNID, the position information of the terminal equipment and the slice information requested by the terminal equipment.

11. The system of claim 10, wherein the source AMF is further configured to send first slice indication information to the target AMF; the first slice indication information is used for indicating first slice information, and the first slice information is slice information of the terminal equipment in a home network.

12. The system according to claim 11, wherein the source AMF is specifically configured to:

Determining the first slice information in case that the PLMN IDs of the source AMF and the target AMF are different;

and generating the first slice indication message according to the first slice information.

13. The system according to claim 11, wherein the first indication information is specifically used for indicating at least one of slice information of the terminal device in the first PLMN network and slice information of the terminal device mapped in the first network in a home network;

the target AMF is specifically configured to: determining slice information of the terminal equipment in the first PLMN network as the first slice information under the condition that the first PLMN network is the home network;

and determining slice information of the terminal equipment mapped in the first network in a home network as the first slice information in the case that the first PLMN network is not the home network.

14. The system of claim 11, wherein the target AMF is further configured to: determining the first slice information;

determining second slice information mapped by the first slice information in the second PLMN network;

Determining a target session management function SMF according to at least one of the second slice information and the position information of the terminal equipment; the target SMF is an SMF in the second PLMN network.

15. The system of claim 14, wherein the target AMF is further configured to send a registration status update message to the source AMF; the registration state update message is used for indicating the source AMF to release a preset session; the preset session is a session which is not supported by the target AMF and is established for the terminal equipment in the source AMF;

the source AMF is further configured to release the preset session in response to the registration status update message.

16. The system of claim 15, wherein the system further comprises: belonging to a unified data management function (UDM);

the target AMF is further configured to send a context request message to the home UDM; the context request message is used for requesting subscription data of the terminal equipment from the UDM;

and the UDM is used for responding to the context request message and sending the subscription data of the terminal equipment to the target AMF.

17. The system of claim 15, wherein the target AMF is further configured to obtain subscription data of the terminal device from the source AMF via the communication interface.

18. The system of claim 17, wherein the system further comprises: a target network slice selection function NSSF;

the target AMF is further configured to initiate a query to the target NSSF according to the first slice information, determine the second slice information, and support an AMF list of the second slice information.

19. The system of claim 17, wherein the target AMF is further configured to query a slice mapping relationship configured in the target AMF based on the first slice information, determine the second slice information, and support an AMF list of the second slice information.

20. The system of claim 18 or 19, wherein the system further comprises: a first AMF; the target AMF is further configured to:

determining whether the target AMF is included in the AMF list; the first AMF is an AMF in the AMF list;

and if not, determining the first AMF according to the AMF list.

21. The system of claim 20, wherein the target AMF is further configured to send first indication information to the target access network device, the first indication information comprising at least one of: the identification of the first AMF, the registration request message and the second slice information;

The target access network device is configured to generate second indication information according to the first indication information, and send the second indication information to the first AMF; the second indication information includes at least one of: the identification of the first AMF, the registration request message and the second slice information;

the first AMF is configured to determine, according to the second indication information, an identifier of the first AMF, the registration request message, and at least one item of second slice information.

22. The system of claim 20, wherein 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 registration request message, SUPI of the terminal rod device, context of the terminal device and the second slice information;

the first AMF is configured to determine, according to the third indication information, the registration request message, the SUPI of the terminal rod device, the context of the terminal device, and at least one item of second slice information.

23. The system according to claim 21 or 22, wherein the system further comprises: home SMF and home policy control function PCF;

The attribution SMF is also used for sending fourth indication information to the attribution PCF; the fourth indication information is used for indicating to conduct SM policy management; and indicating location information of the terminal device to the home PCF.

24. The system of claim 23, wherein the target AMF is further configured to send fifth indication information to the target access network device, the fifth indication information being configured to indicate at least one of the PLMN list and the mobility restriction list.

25. A communication method, characterized in that it is applied in a communication system, said communication system comprising: 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 network; the target AMF belongs to a second PLMN network; the source AMF is connected with the target AMF through a communication interface; the method comprises the following steps:

the target AMF receives a redirection request from the target access network equipment; the redirection request comprises a first global unique temporary identifier GUTI of the terminal equipment; the first GUTI is a GUTI of the terminal device in the first PLMN network;

The target AMF determines a first GUTI of the terminal equipment 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 from the terminal device of the source AMF.

26. The method of claim 25, wherein the obtaining session information of the terminal device from the source AMF comprises:

the target AMF sends a first request message to the source AMF; the first request message is used for requesting context information of the terminal equipment and a user permanent identifier SUPI;

the target AMF receives a first response message from the source AMF; the first response message comprises the context information and SUPI of the terminal equipment;

and the target AMF determines the terminal equipment according to the SUPI and creates a context for the terminal equipment according to the context information.

27. The method of claim 25 or 26, wherein the determining the source AMF from the first GUTI comprises:

the target AMF analyzes the first GUTI and determines a globally unique AMF identifier GUAMI in the first GUTI;

The target AMF determines the AMF characterized by the GUAMI as the source AMF.

28. The method of claim 25 or 26, wherein after said determining the source AMF from the first GUTI, the method further comprises:

the target AMF sends a registration state update message to the source AMF; the registration state update message is used for indicating the source AMF to release a preset session; the preset session is a session which is not supported by the target AMF and established by the source AMF for the terminal equipment.

29. The method of claim 25 or 26, wherein after the target AMF sends a registration status update message to the source AMF, the method further comprises:

the target AMF sends a context request message to the home unified data management function UDM; the context request message is used for requesting subscription data of the terminal equipment from the UDM;

the target AMF receives subscription data from the terminal device of the UDM.

30. The method of claim 25 or 26, wherein after the target AMF sends a registration status update message to the source AMF, the method further comprises:

and the target AMF acquires the subscription data of the terminal equipment from the source AMF through the communication interface.

31. The method according to claim 25 or 26, characterized in that the method further comprises:

the target AMF initiates a query to the target network slice selection function NSSF according to first slice information, determines the second slice information and supports an AMF list of the second slice information, wherein the first slice information is slice information of the terminal equipment in a home network.

32. The method of claim 31, wherein after the target AMF initiates a query to the target network slice selection function NSSF based on the first slice information, determines the second slice information, and supports the AMF list of the second slice information, the method further comprises:

the target AMF determines whether the AMF list comprises the target AMF; the first AMF is an AMF in the AMF list;

and if not, the target AMF determines the first AMF according to the AMF list.

33. The method of claim 31, wherein after the target AMF determines the first AMF from the list of AMFs, the method further comprises:

the target AMF sends first indication information to the target access network equipment, so that the target access network equipment forwards the identification of the first AMF to the first AMF according to the first indication information, the registration request message and at least one item of second slice information.

34. The method of claim 31, wherein after the target AMF determines the first AMF from the list of AMFs, the method further comprises:

the target AMF sends third indication information to the first AMF; the third indication information includes at least one of: the registration request message, the SUPI of the terminal lever device, the context of the terminal device, and the second slice information.

35. The method according to claim 33 or 34, characterized in that the method further comprises:

the target AMF sends fifth indication information to the target access network device, where the fifth indication information is used to indicate at least one of the PLMN list and the mobility restriction list.

36. A communication method, characterized in that it is applied in a communication system, said communication system comprising: 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 network; the target AMF belongs to a second PLMN network; the source AMF is connected with the target AMF through a communication interface; the method comprises the following steps:

The source access network equipment determines the frequency point information of the target access network equipment and sends the frequency point information to the terminal equipment; the frequency point information of the target access network equipment is used for indicating the terminal equipment to access the target access network equipment according to the frequency point information, and a redirection request is sent to the terminal equipment through the target access network equipment.

37. The method of claim 36, wherein the source access network device determining frequency point information for the target access network device comprises:

the source access network equipment determines a target PLMD identification ID; the target PLMNID is the PLMNID which is required to be selected when the terminal equipment accesses the second PLMN network;

and the source access network equipment determines the frequency point information of the PLMN network corresponding to the target PLMN ID as the frequency point information of the target access network equipment.

38. The method of claim 37, wherein after the source access network device sends the frequency point information to the terminal device, the method further comprises:

the source access network device receives a PLMN list from the source AMF; the PLMN list includes at least one of the following: the HPLMN of the terminal equipment serves PLMN, equivalent public land mobile network EPLMN, PLMN selected in the previous time;

The source access network device determines the target PLMN from the PLMN list.

39. The method of claim 38, wherein the source access network device determining the target PLMN from the PLMN list comprises:

the source access network equipment determines the current service PLMNID of the terminal equipment according to the PLMN list;

the source access network equipment determines the home network of the terminal equipment according to the service PLMN ID of the terminal equipment;

the source access network device determines that the PLMN ID of the home network of the terminal device in the second PLMN network is a first PLMN ID;

the source access network device determines the first PLMNID as the target PLMNID.

40. The method of claim 37, wherein after the source access network device sends the frequency point information to the terminal device, the method further comprises:

the source access network device receives a mobility restriction list from the source AMF; the mobility restriction list is used for indicating a first PLMNID; the first PLMNID is the PLMN ID of the home network of the terminal equipment 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.

41. The method of claim 40, wherein the source access network device determining frequency point information for the target access network device comprises:

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;

and the source access network equipment determines the frequency point information of the target access network equipment.

42. A communication method, characterized in that it is applied in a communication system, said communication system comprising: 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 network; the target AMF belongs to a second PLMN network; the source AMF is connected with the target AMF through a communication interface; the method comprises the following steps:

the source AMF receives a session information request message from the target AMF; the source AMF is an AMF determined by the target AMF according to the first GUTI of the terminal equipment;

and the source AMF responds to the session request message and sends the session information of the terminal equipment to the target AMF.

43. The method of claim 42, further comprising:

the source AMF sends 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 serves PLMN, equivalent public land mobile network EPLMN, the PLMN selected in the previous time.

44. The method of claim 43, further comprising:

the source AMF sends a mobility limit list to the source access network equipment; the mobility restriction list is used for indicating a first PLMNID; the first PLMN ID is a PLMNID of the home network of the terminal equipment in the second PLMN network.

45. The method of claim 43, wherein before the source AMF sends the mobility restriction list to the source access network device, the method further comprises:

the source AMF determines location information of the terminal device,

the source AMF determines that a PLMN network adjacent to the first PLMN network is the second PLMN network at a position represented by the position information of the terminal equipment;

the source AMF determines PLMNID allowing the terminal equipment access network in the second PLMN network;

And the source AMF determines the PLMNID of the access network of the terminal equipment to be the first PLMNID.

46. The method of any one of claims 42-45, further comprising:

the source AMF sends first slice indication information to the target AMF; the first slice indication information is used for indicating first slice information, and the first slice information is slice information of the terminal equipment in a home network.

47. The method of claim 46, further comprising:

determining first slice information in case that the PLMNID of the source AMF is different from that of the target AMF;

and generating the first slice indication message according to the first slice information.

48. The method of claim 46, wherein the first indication information is specifically used to indicate at least one of slice information of the terminal device in the first PLMN network and slice information of the terminal device mapped in the first network in a home network.

49. The method of claim 48, further comprising:

the source AMF receives a registration status update message from the target AMF; the registration state update message is used for indicating the source AMF to release a preset session; the preset session is a session which is not supported by the target AMF and is established for the terminal equipment in the source AMF;

The source AMF responds to the registration state update message to release the preset session.

50. A communication device, comprising: a communication unit and a processing unit; wherein the communication unit is used for communicating with other communication devices; the processing unit for performing the communication method of any of claims 25-35; or performing the communication method of any one of claims 36-41; or performing the communication method of any of claims 42-49.

51. A communication device, comprising: a processor and a memory; wherein the memory is configured to store computer-executable instructions that, when executed by the communication device, cause the communication device to perform the communication method of any of claims 25-35; or performing the communication method of any one of claims 36-41; or performing the communication method of any of claims 42-49.

52. A computer readable storage medium comprising instructions that, when executed, cause the computer to perform the communication method of any of claims 25-35; or performing the communication method of any one of claims 36-41; or performing the communication method of any of claims 42-49.