RU2796658C2 - Method, device and system of intersystem handover - Google Patents

Abstract

FIELD: communications.

SUBSTANCE: invention is proposed to provide intersystem handover. For this, the UE user device receives the indication information during the first session establishment process. It is determined whether a first session exists in the first communication system, where it is possible to transfer the first session from the first communication system to the second communication system. The first message is transmitted by the UE to the first main network device of the second communication system if the presence of the first session is determined, where the first message is used to establish a second session in the second communication system, and the second session corresponds to the first session.

EFFECT: intersystem handover.

29 cl, 25 dwg

Description

The field of technology to which the invention belongs

The present invention relates to the field of communication and, in particular, to a method, device and system for intersystem movement.

State of the art

In the latest technology of the fifth generation of mobile communication ( ^5th Generation, 5G) and fourth generation mobile communication technology ( ^4th Generation, 4G), the standards of the ^3rd Generation Partnership Project (3GPP), user equipment (user equipment, UE) can support dual registration (registration with both 5G and 4G).

If the UE transitions seamlessly from 5G to 4G in a dual registration state (i.e., the Internet Protocol (IP) address assigned to the UE does not change and the pluggable network element on the core network does not change), then all sessions are transferred (session ) a Protocol Data Unit (PDU) established by a UE in 5G, in 4G by sending a 4G connection message including a handover indication and a connection setup PDU request message including a handover indication.

However, it is possible that the transfer of some session PDUs established in 5G cannot be performed in 4G in a seamless manner. During migration, the Mobile Management Entity (MME) may reject the PDN connection request because the MME cannot find the PGW address based on the Access Point Name (APN). Therefore, the UE cannot continue to use the service. Further, during the UE's seamless roaming from 5G to 4G network, after establishing a 4G PDN connection, the PGW is configured to remove the seamless transfer session from the 5G PDU, but cannot remove the non-seamless transfer to 4G session PDU.

The essence of the invention

Embodiments of the present invention provide a method, apparatus, and system for intersystem movement for performing UE movement between communication systems and deleting a non-transferable session.

To achieve this task, the following technical solutions are used in the embodiments of the present invention:

According to a first aspect, an inter-system roaming method is provided, wherein the method includes: determining, by a UE, whether a first session exists in a session established in a first communication system, where transfer of the first session from the first communication system to the second system can be performed communications; and sending, by the UE, a first message to the first primary network device of the second communication system upon determining that there is no first session, where the first message is used to perform joining to the second communication system. According to the intersystem migration method presented in this embodiment of the present invention, when determining whether a first session exists in the first communication system, the user device sends a first message to the first primary network device of the second communication system to perform joining to the second communication system. The third primary network device obtains a first session ID and a third session ID, where the third session is a session on the first communication system, without being able to transfer from the first communication system to the second communication system. Then, the third primary network device deletes the first session based on the first session ID. Since the second session in the second communication system corresponds to the first session in the first communication system, deleting the first session in the first communication system implements the transfer of the first session. In addition, the fourth main network device sends a fourth message to the fourth main network device corresponding to the second session ID, so that the fourth main network device deletes the third session corresponding to the third session ID, that is, deletes the session without being able to perform a transfer. Thus, during the period of performing the transfer, the UEs between communication systems delete the session without the possibility of transfer.

In an exemplary implementation, a first message is used to perform the attachment to the second communication system, which includes: using the first message to perform the initial attachment to the second communication system. Such an implementation provides a specific message to indicate the attachment.

In one possible implementation, sending by the UE a first message to the first main network device of the second communication system when determining that the first session is not present, which further includes: sending by the UE the first message to the first main network device of the second communication system when the UE determines that the first session is not present, and that the UE or the second communication system does not support said flag, wherein said flag includes joining a second communication system without a PDN connection. Such an implementation allows the UE to send a message when the UE determines that the first session is not present.

In one possible implementation, the method further includes: sending, by the UE, a second message to the first primary network device of the second communication system when the UE determines that the first session exists, where the second message is used to perform a tracking area update in the second communication system. Such an implementation allows the UE to send a message when the UE determines that the first session exists.

In an exemplary implementation, the method further includes: sending, by the UE, a third message to the first primary network device of the second communication system when the UE determines that the first session exists, where the third message is used to establish a second session in the second communication system, and the second session corresponds to the first session. Such an implementation provides a way to transfer a session between another communication system.

In an exemplary implementation, the third message is an attach request message, the attach request message includes a handover indication and an encrypted options transmission flag, and the method further includes: receiving, by the UE, an encrypted options request message from the first underlying network device, in which the request message the encrypted options are sent by the first primary network device based on the encrypted options transmission flag; and sending, by the UE, an encrypted options response message to the first core network device, wherein the encrypted options response message includes an APN corresponding to the first session. According to this implementation, the new MME can obtain the APN corresponding to the first UE session.

In an exemplary implementation, before the UE sends the third message to the first primary network device of the second communication system, the method further includes: determining by the UE that the APN corresponding to the first session is not a default APN; or determining by the UE that the data network name DNN corresponding to the first session is not the default DNN. Such an implementation exposes two conditions for sending an APN by a UE.

In an exemplary implementation, the third message is a protocol data network connection request, PDN, and the PDN connection request includes an indication of a handover and an APN corresponding to the first session. This implementation exposes the content of the PDN connection request.

In an exemplary implementation, before the UE sends the third message to the first primary network device of the second communication system, the method includes: determining by the UE that the APN corresponding to the first session is not the default APN; or determining by the UE that the DNN corresponding to the first session is not the default DNN. Such an implementation exposes two conditions for sending an APN by a UE.

In an exemplary implementation, the method further includes: deriving by the UE an APN based on the locally stored data network name a matching DNN-APN and a DNN corresponding to the first session. Such an implementation discloses a method for obtaining a DNN corresponding to the first session by the UE.

In an exemplary implementation, before the UE determines whether the first session exists, the method further includes: sending, by the UE, a session establishment request message PDU to the second primary network device of the first communication system to establish the first session; and receiving, by the UE, a session establishment permission message PDU from the second primary network device, in which the session establishment permission message PDU includes an APN.

In an exemplary implementation, the method further includes: receiving by the UE the indication information during a first session establishment process, which uses the indication information to indicate the first session in a transferable manner from the first communication system to the second communication system. Such an implementation discloses a method for obtaining by the UE information indicating the ability to transfer the first session from the first communication system to the second communication system.

In an exemplary implementation, the method further includes: receiving by the UE the indication information during the process of establishing a first session in the first communication system, where the indication information is used by the UE to determine that it is possible to transfer the first session from the first communication system to the second communication system. Such an implementation discloses a method for the UE to obtain information indicating the possibility of transferring the first session from the first communication system to the second communication system.

In an exemplary implementation, the indication information includes one or a combination of the following information: a parameter related to a session in the second communication system corresponding to the first session, where when the UE receives the corresponding parameter, the UE determines that the first session can be transferred from the first system communication to the second communication system; a service and session continuity mode of the first session, where when the service and session continuity mode of the first session is a certain mode, the UE determines that it is possible to transfer the first session from the first communication system to the second communication system; the IP address of the first session, where, when the IP address belongs to the specified segment of the address, the UE determines that it is possible to transfer the first session from the first communication system to the second communication system; network segment corresponding to the first session where, when the network segment has a corresponding service in the second communication system, the UE determines that it is possible to transfer the first session from the first communication system to the second communication system; and a data network name corresponding to the first session, where, when given an access point name corresponding to the data network name, the UE determines that it is possible to transfer the first session from the first communication system to the second communication system. This implementation exposes the specific content of the indication information.

In an exemplary implementation, receiving by the UE the indication information during the first session establishment process includes: sending, by the UE, a session establishment request message PDU to the second primary network device of the first communication system to establish the first session; and receiving, by the UE, a session establishment permission message PDU from the second main network device, in which the session establishment permission message PDU includes indication information. Such an implementation discloses a method for obtaining indication information by a UE.

In one possible implementation, the encrypted options response message further includes a third session identifier, and the third session is a session on the first communication system that is not transferrable from the first communication system to the second communication system. Such an implementation discloses a method for transferring a non-portable session identifier from a first communication system to a second communication system.

In a possible implementation, it is possible to transfer the first session from the first communication system to the second communication system, which includes: the third main network device serving the first session is the main network device shared by the first communication system and the second communication system, in which the third main network device the device provides the control plane service for the first session; or the third primary network device and the fourth primary network device that serve the first session are the primary network devices shared by the first communication system and the second communication system, in which the third primary network device provides a control plane service for the first session and the fourth primary network device provides user plane service for the first session. This implementation discloses specific content that it is possible to transfer the first session from the first communication system to the second communication system.

In an exemplary implementation, the second session corresponds to the first session, which includes: the first session and the second session have the same IP address; or the first session and the second session have the same IP address and the same third primary network device, in which the third primary network device provides the control plane service for the first session; or the first session and the second session have the same IP address, the same third primary network device, and the same fourth primary network device, in which the third primary network device provides the control plane service for the first session and the fourth primary network device provides the user plane service for the first session. This implementation exposes specific content that the second session corresponds to the first session.

In an exemplary implementation, the first communication system is a 5G communication system and the second communication system is a 4G communication system, the first session is a session PDU and the second session is a connection PDN; or the first communication system is a 4G communication system, the second communication system is a 5G communication system, the first session is a connection PDN, and the second session is a session PDU. This implementation discloses a possible handover direction for the intersystem movement method.

According to a second aspect, an embodiment of the present invention provides a UE, including: a determination unit configured to determine whether a first session exists in a session established in a first communication system, where transfer of the first session from the first communication system to a second communication system; and a sender configured to send a first message for the UE to the first primary network device of the second communication system when it is determined that there is no first session, where the first message is used to perform joining to the second communication system. Based on the same concept of the invention, for the principle of solving the technical problem and the beneficial effect of the device, the first aspect, the possible implementations of the method according to the first aspect, and the beneficial effects obtained are referred to. Thus, for the implementation of the device, reference is made to the first aspect and possible implementations of the method according to the first aspect. The same details are not repeated.

According to a third aspect, an inter-system move method is provided, wherein the method includes: determining, by a user device UE, whether a first session exists in a first communication system where transfer of the first session from the first communication system to the second communication system is possible; and sending, by the UE, a first message to the first primary network device of the second communication system if a first session is determined, where the first message is used to establish a second session in the second communication system, and the second session corresponds to the first session. According to the intersystem roaming method presented in this embodiment of the present invention, when determining whether a first session exists in the first communication system, the user device sends a first message to the first primary network device of the second communication system to establish a second session in the second communication system, where the second session corresponds to the first session. The third primary network device obtains a first session identifier and a third session identifier, where the third session is a session in the first communication system without the possibility of transferring from the first communication system to the second communication system. Then, the third primary network device deletes the first session based on the first session ID. Since the second session in the second communication system corresponds to the first session in the first communication system, deleting the first session in the first communication system implements the transfer of the first session. Additionally, the fourth main network device sends a fourth message to the fourth main network device corresponding to the second session ID, so that the fourth main network device deletes the third session corresponding to the third session ID, i.e., deletes the session without being able to implement the transfer. Thus, the session is deleted without the possibility of realizing the transfer while the UE moves between communication systems.

In an exemplary implementation, the first message is an attach request message, the attach request message includes a handover indication and an encrypted options transmission flag, and the method further includes: receiving, by the UE, an encrypted options request message from the first underlying network device, in which the request message the encrypted options are sent by the first master network device based on the encrypted options transmission flag; and sending, by the UE, an encrypted options response message to the first core network device, in which the encrypted options response message includes an APN corresponding to the first session. According to this implementation, the new MME can obtain the APN corresponding to the first UE session.

In an exemplary implementation, before the UE sends the first message to the first primary network device of the second communication system, the method further includes: determining by the UE that the APN corresponding to the first session is not a default APN; or determining by the UE that the data network name DNN corresponding to the first session is not the default DNN. Such an implementation exposes two conditions for sending an APN by a UE.

In an exemplary implementation, the first message is a protocol data network PDN connection request, and the PDN connection request includes an indication of a handover and an APN corresponding to the first session. This implementation exposes the content of the PDN connection request.

In an exemplary implementation, before the UE sends the first message to the first primary network device of the second communication system, the method includes: determining by the UE that the APN corresponding to the first session is not the default APN; or determining by the UE that the DNN corresponding to the first session is not the default DNN. This implementation exposes two conditions for sending an APN by a UE.

In an exemplary implementation, the method further includes: deriving the UE APN based on the locally stored data network name DNN-APN of the match and the DNN corresponding to the first session. Such an implementation discloses a method for obtaining a DNN corresponding to the first session by the UE.

In an exemplary implementation, before the user device UE determines whether a first session exists in the first communication system, the method further includes: sending, by the UE, a session PDU establishment request message to the second primary network device of the first communication system to establish the first session; and receiving, by the UE, a session PDU establishment grant message from the second primary network device, wherein the session PDU establishment grant message includes an APN. Such an implementation discloses a method for obtaining an APN by a UE.

In an exemplary implementation, before the UE determines whether a first session exists in the first communication system, the method further includes: receiving, by the UE, indication information during the first session establishment process, where the indication information is used to indicate that the transfer of the first session from the first system is possible. communication to the second communication system. Such an implementation discloses a method for the UE to obtain indication information that a transfer of the first session from the first communication system to the second communication system is possible.

In an exemplary embodiment, the indication information includes one or a combination of the following information: a parameter related to a session in the second communication system corresponding to the first session, where, when the UE receives the corresponding parameter, the UE determines that the first session can be transferred from the first communication system to the second communication system; a service and session continuity mode of the first session, where when the service and session continuity mode of the first session is the specified mode, the UE determines that it is possible to transfer the first session from the first communication system to the second communication system; the IP address of the first session, where, when the IP address belongs to the specified segment address, the UE determines that it is possible to transfer the first session from the first communication system to the second communication system; a network segment corresponding to the first session, where, when the network segment has a corresponding service in the second communication system, the UE determines that it is possible to transfer the first session from the first communication system to the second communication system; and a data network name corresponding to the first session, where when there is an access point name corresponds to a data network name, the UE determines that it is possible to transfer the first session from the first communication system to the second communication system. This implementation exposes the specific content of the indication information.

In an exemplary implementation, receiving by the UE the indication information during the first session establishment process includes: sending, by the UE, a session establishment request message PDU to the second primary network device of the first communication system to establish the first session; and receiving, by the UE, a session PDU establishment permission message from the second main network device, in which the session PDU establishment permission message includes indication information. Such an implementation discloses a method for obtaining indication information by a UE.

In one possible implementation, the encrypted options response message further includes a third session identifier, and the third session is a session on the first communication system that is not transferable from the first communication system to the second communication system. Such an implementation discloses a method for transferring a non-portable session identifier from a first communication system to a second communication system.

In an exemplary implementation in which the transfer of the first session from the first communication system to the second communication system is possible, the third primary network device serving the first session is the primary network device shared by the first communication system and the second communication system, in which the third primary the network device provides the control plane service for the first session; or the third primary network device and the fourth primary network device that serves the first session are the primary network devices shared by the first communication system and the second communication system, in which the third primary network device provides a control plane service for the first session and the fourth primary network device provides user plane service for the first session. This implementation discloses specific content that it is possible to transfer the first session from the first communication system to the second communication system.

In a possible implementation in which the second session corresponds to the first session includes: the first session and the second session have the same IP address; or the first session and the second session have the same IP address and the same third primary network device, in which the third primary network device provides the control plane service for the first session; or the first session and the second session have the same IP address, the same third primary network device and the same fourth primary network device, in which the third primary network device provides the control plane service for the first session and the fourth primary network device provides the user plane service for the first session . This implementation exposes the specific content that the second session corresponds to the first session.

In an exemplary implementation, the first communication system is a 5G communication system, the second communication system is a 4G communication system, the first session is a session PDU, and the second session is a connection PDN; or the first communication system is a 4G communication system, the second communication system is a 5G communication system, the first session is a connection PDN, and the second session is a session PDU. Such an implementation discloses a possible handover direction for the intersystem transfer method.

According to a fourth aspect, an embodiment of the present invention provides a UE, including: a determination unit configured to determine whether a first session exists in a first communication system, where transfer of the first session from the first communication system to the second communication system is possible; and a sender configured to send a first message from the first host network device of the second communication system when a first session is determined, where the first message is used to establish a second session in the second communication system, and the second session corresponds to the first session. According to the user device provided in this embodiment of the present invention, when determining whether a first session exists in the first communication system, the user device sends a first message to the first main network device of the second communication system to establish a second session in the second communication system, where the second session corresponds to the first session. The third primary network device obtains a first session identifier and a third session identifier, where the third session is a session in the first communication system that cannot be transferred from the first communication system to the second communication system. Then, the third primary network device deletes the first session based on the first session ID. Since the second session in the second communication system corresponds to the first session in the first communication system, deleting the first session in the first communication system implements the transfer of the first session. Additionally, the fourth main network device sends a fourth message to the fourth main network device corresponding to the second session ID, so that the fourth main network device deletes the third session corresponding to the third session ID, i.e., deletes the session without being able to be transferred. Thus, a non-transferable session is deleted while the UE moves between communication systems. Based on the same concept of the invention, for the principle of solving the technical problem and the beneficial effect of the device, reference is made to the third aspect, possible implementations of the method according to the third aspect, and the beneficial effects achieved. Thus, to implement the device, reference is made to the third aspect and possible implementations of the method according to the third aspect. The same details are not repeated.

According to a fifth aspect, an embodiment of the present invention provides a UE user device including a processor, a memory, a bus, and a communication interface, where the memory is configured to store an instruction executable on a computer, the processor and the memory are connected via a bus, and when the device of the UE user is running, the processor executes an instruction on the computer stored in the memory to cause the UE user device to execute the method of any one of the first aspect or possible implementations of the first aspect, or the method of any one of the third aspect or possible implementations of the third aspect. Based on the same concept of the invention, the processor calls the instruction stored in the memory to implement the decision in the development of the method according to the first aspect. To realize the solution of the technical problem and the beneficial effect of the operation of the user's device, reference is made to the first aspect, possible implementations of the method according to the first aspect, the third aspect, possible implementations of the method according to the third aspect, as well as their beneficial effects. Thus, reference is made to method implementations to implement a user's device. The same details are not repeated.

According to a sixth aspect, an embodiment of the present invention provides a computer storage medium containing an instruction, when executed on the computer, the computer is configured to perform the intersystem transfer method in the first aspect or the third aspect.

According to a seventh aspect, an embodiment of the present invention provides a computer program product including an instruction, when executing the computer program product on the computer, the computer is configured to execute the intersystem transfer method in the first aspect or the third aspect.

Additionally, in order to describe the technical effects of any implementation of the fifth aspect through the seventh aspect, reference is made to the technical effects of the implementations according to the first aspect or the third aspect. Details are not described here again.

According to an eighth aspect, an intersystem migration method is provided, including: receiving a first message by a first primary network device, where the first message is used to establish a second session in the second communication system, the second session corresponds to the first session in the first communication system, and transferring the first session from a first communication system to a second communication system; obtaining by the first primary network device the identifier of the first session; and sending, by the first primary network device, a second message to the second primary network device, wherein the second message includes a first session identifier, and the second message is used to request the second primary network device to delete the first session. According to the intersystem movement method presented in this embodiment of the present application, when determining whether a first session exists in the first communication system, the UE sends a first message to the first main network device of the second communication system to establish a second session in the second communication system, where the second session corresponds to the first session. The third primary network device obtains a first session identifier and a third session identifier, where the third session is a session in the first communication system that cannot be transferred from the first communication system to the second communication system. Then, the third primary network device deletes the first session based on the first session ID. Since the second session in the second communication system corresponds to the first session in the first communication system, deleting the first session in the first communication system implements the transfer of the first session. Additionally, the fourth main network device sends a fourth message to the fourth main network device corresponding to the second session ID, so that the fourth main network device deletes the third session corresponding to the third session ID, i.e., deletes the session without being able to be transferred. Thus, a non-transferable session is deleted while the UE moves between communication systems.

In an exemplary implementation, the first message is a session establishment request message, the session establishment request message includes a handover indication and an APN corresponding to the first session; and obtaining by the first primary network device the first session ID includes: obtaining by the first primary network device a data network name DNN corresponding to the APN and an Internet Protocol IP address corresponding to the DNN, or obtaining an Internet Protocol IP address corresponding to the APN; and obtaining by the first primary network device a first session identifier corresponding to the IP address. This implementation exposes two ways to get the first session ID.

In a possible implementation, prior to the first primary network device receiving the first message, the method further comprising: sending the first primary network device a first request message to the third primary network device during a first session establishment process for the UE, wherein the first request message includes an address a first primary network device and a DNN corresponding to the first session; or the first primary network device receiving the APN corresponding to the first session during the first session establishment process for the UE and sending the first request message to the third primary network device, where the first request message includes the address of the first primary network device and the APN. Such an implementation exposes two message content types of the first request message.

In an exemplary implementation, the first message further includes a third session identifier, and the third session is a non-transferable session on the first communication system from the first communication system to the second communication system; and the second message further includes a third session identifier, and is used to request the second primary network device to delete the third session. Such an implementation discloses a method for deleting a session without being able to transfer from a first communication system to a second communication system.

In one possible implementation, that it is possible to transfer the first session from the first communication system to the second communication system includes: the first primary network device is a primary network device shared by the first communication system and the second communication system; or the first primary network device is the primary network device shared by the first communication system and the second communication system, and the fourth primary network device serving the first session is the primary network device shared by the first communication system and the second communication system, where the fourth primary network device provides the user plane service for the first session. This implementation discloses the specific content that it is possible to transfer the first session from the first communication system to the second communication system.

In a possible implementation that the second session corresponds to the first session in the first communication system includes: the first session and the second session have the same IP address; or the first session and the second session have the same IP address and the same first primary network device; or the first session and the second session have the same IP address, the same first primary network device, and the same fourth primary network device, in which the fourth primary network device provides the user plane service for the first session. This implementation exposes the specific content that the second session corresponds to the first session.

In an exemplary implementation, the first communication system is a 5G communication system, the second communication system is a 4G communication system, the first session is a session PDU, and the second session is a connection PDN; or the first communication system is a 4G communication system, the second communication system is a 5G communication system, the first session is a PDN connection, and the second session is a PDU session. Such an implementation discloses a possible handover direction for the intersystem movement method.

According to a ninth aspect, an embodiment of the present invention provides a basic network device, including: a receiving unit configured to receive a first message, wherein the first message is used to establish a second session in a second communication system, the second session corresponds to a first session in the first system communication, and it is possible to transfer the first session from the first communication system to the second communication system; a receiving unit, configured to obtain a first session identifier; and a sender configured to send a second message to the second host network device, where the second message includes a first session identifier, and the second message is used to request the second host network device to delete the first session. According to the core network device provided in this embodiment of the present invention, when determining whether a first session exists in the first communication system, the UE sends a first message to the first core network device of the second communication system to establish a second session in the second communication system, where the second session corresponds to the first session. The third primary network device obtains a first session ID and a third session ID, where the third session is a session on the first communication system, not transferable from the first communication system to the second communication system. Then, the third primary network device deletes the first session based on the first session ID. Since the second session in the second communication system corresponds to the first session in the first communication system, deleting the first session in the first communication system implements the transfer of the first session. Additionally, the fourth main network device sends a fourth message to the fourth main network device corresponding to the second session ID, so that the fourth main network device deletes the third session corresponding to the third session ID, i.e., deletes the session without being able to be transferred. Thus, a non-transferable session is deleted while the UE moves between communication systems. Based on the same concept of the invention, for the principle of solving the technical problem and the beneficial effect, reference is made to the eighth aspect, possible implementations of the method in accordance with the eighth aspect, and the beneficial effects obtained. Thus, for the implementation of the device, reference is made to the eighth aspect and possible implementations of the method according to the eighth aspect. The same details are not repeated.

According to a tenth aspect, an embodiment of the present invention provides a main network device including a processor, a memory, a bus, and a communication interface, where the memory is configured to store an instruction executable on a computer, the processor and the memory are connected by a bus, and when running host network device, the processor executes an instruction on the computer stored in memory to enable the host network device to execute the method of any of the eighth aspect or possible implementations of the eighth aspect. Based on the same concept of the invention, the processor calls the instruction stored in the memory to implement the decision in the method in the eighth aspect. In order to realize the solution of the technical problem and the beneficial effect of the main network device, reference is made to the eighth aspect, possible implementations of the method in accordance with the eighth aspect, and their beneficial effects. Thus, for the implementation of the main network device, reference is made to the implementation of the method. The same details are not repeated.

According to an eleventh aspect, an embodiment of the present invention provides a computer storage medium including an instruction that, when executed on a computer, the computer is configured to perform the intersystem movement method of the eighth aspect.

According to a twelfth aspect, an embodiment of the present invention provides a computer program product including an instruction that, when executed on a computer, the computer is configured to perform the intersystem movement method of the eighth aspect.

Additionally, in order to obtain technical effects on the method of implementation in the tenth aspect through the twelfth aspect, reference is made to the technical effects on the method in the eighth aspect. Details are not described here again.

According to a thirteenth aspect, a method for inter-system migration is provided, including: obtaining by a first primary network device a first session identifier and a second session identifier, where the first session is a session in the first communication system, with the possibility of being transferred from the first communication system to the second communication system, and the second session is a session in the first communication system, without the possibility of transfer from the first communication system to the second communication system; deleting by the first primary network device the first session based on the identifier of the first session; and sending, by the first host network device, a first message to the second host network device corresponding to the second session ID, wherein the first message is used by the second host network device to delete the second session corresponding to the second session ID. In accordance with the intersystem roaming method presented in the embodiments of the present invention, when determining whether a first session exists in the first communication system, the UE sends a first message to the first primary network device of the second communication system to establish a second session in the second communication system, where the second session corresponds to the first session. The third primary network device obtains a first session ID and a third session ID, where the third session is a session on the first communication system, not transferable from the first communication system to the second communication system. Then, the third primary network device deletes the first session based on the first session ID. Since the second session in the second communication system corresponds to the first session in the first communication system, deleting the first session in the first communication system implements the transfer of the first session. In addition, the fourth main network device sends a fourth message to the fourth main network device corresponding to the second session ID, so that the fourth main network device deletes the third session corresponding to the third session ID, i.e., deletes the session without being able to be transferred. Thus, a non-transferable session is deleted while the UE moves between communication systems.

In a possible implementation, obtaining by the first primary network device the first session identifier and the second session identifier includes: the first primary network device receiving a second message from the third primary network device, wherein the second message includes the first session identifier and the second session identifier. Such an implementation discloses a way to obtain a first session ID and a second session ID.

In an exemplary implementation, obtaining by the first primary network device a first session identifier and a second session identifier includes: receiving by the first primary network device a second message from a third primary network device, wherein the second message includes the first session identifier; and obtaining, by the first host network device, a second session identifier based on the stored session information of the first communication system. Such an implementation discloses a way to obtain a first session ID and a second session ID.

In an exemplary implementation, before the first host network device obtains a second session identifier based on the stored session information of the first communication system, the method further includes: receiving by the first host network device a third message from the fourth host network device, and determining based on the third message that the user device UE is in the second communication system. Such an implementation discloses a method for obtaining information that the UE is in the second communication system.

In an exemplary implementation, before the first primary network device receives a first session ID and a second session ID, the method further includes: receiving by the first primary network device a session PDU establishment request message from the UE to establish a first session; and sending a session PDU establishment permission message to the UE, in which the session PDU establishment permission message includes indication information, and the indication information is used to indicate that it is possible to transfer the first session from the first communication system to the second communication system; or receiving, by the first primary network device, a session establishment request message from the UE to establish a second session; and sending a session PDU establishment permission message to the UE, in which the session PDU establishment permission message includes indication information, and the indication information is used to indicate that it is not possible to transfer the second session from the first communication system to the second communication system. Such an implementation discloses a method for notifying a UE whether a session transfer from a first communication system to a second communication system is possible.

In an exemplary implementation, before the first primary network device receives a first session identifier and a second session identifier, the method further includes: sending the first primary network device a third message to the fourth primary network device, where the third message includes the address of the second primary network device, and DNN corresponding to the first session; or, the first primary network device receiving the APN corresponding to the first session and sending a third message to the fourth primary network device, wherein the third message includes the address of the third primary network device and the APN. Such an implementation discloses a method for transmitting the address of the third primary network device, APN or DNN.

In a possible implementation, that the first session is a session in the first communication system with the possibility of being transferred from the first communication system to the second communication system includes: the third primary network device served by the first session is the primary network device shared by the first communication system and the second a communication system in which the third primary network device provides a control plane service for the first session; or the third primary network device and the fourth primary network device that serves the first session are the primary network devices shared by the first communication system and the second communication system in which the third primary network device provides the control plane service for the first session, and the fourth primary network device provides the user plane service for the first session. This implementation discloses the specific content that it is possible to transfer the first session from the first communication system to the second communication system. This implementation discloses the specific content that it is possible to transfer the first session in the first communication system from the first communication system to the second communication system.

In an exemplary implementation, the first communication system is a 5G communication system, the second communication system is a 4G communication system, and the first session and the second session are session PDUs; or the first communication system is a 4G communication system, the second communication system is a 5G communication system, and the first session and the second session are a PDN connection. Such an implementation discloses a possible handover direction for the intersystem movement method.

According to a fourteenth aspect, an embodiment of the present invention provides a basic network device, including: an acquisition unit configured to obtain a first session identifier and a second session identifier, where the first session is a session in a first communication system with the possibility of being transferred from the first system communication to the second communication system, and the second session is a session in the first communication system, without the possibility of transfer from the first communication system to the second communication system; a delete unit, configured to delete the first session based on the first session ID; and a sender configured to send the first message to the second primary network device corresponding to the second session ID, wherein the first message is used by the second primary network device to delete the second session corresponding to the second session ID. According to the main network device provided in the embodiments of the present invention, when determining whether a first session exists in the first communication system, the UE sends a first message to the first main network device of the second communication system to establish a second session in the second communication system, where the second session corresponds to first session. The third primary network device obtains a first session ID and a third session ID, where the third session is a session on the first communication system, not transferable from the first communication system to the second communication system. Then, the third primary network device deletes the first session based on the first session ID. Since the second session in the second communication system corresponds to the first session in the first communication system, deleting the first session in the first communication system implements the transfer of the first session. Additionally, the fourth main network device sends a fourth message to the fourth main network device corresponding to the second session ID, so that the fourth main network device deletes the third session corresponding to the third session ID, i.e., deletes the session without being able to be transferred. Thus, a non-transferable session is deleted while the UE moves between communication systems. Based on the same concept of the invention, in order to explain the principle of solving the technical problem and the beneficial effect of the device, reference is made to the thirteenth aspect, possible implementations of the method in accordance with the thirteenth aspect, and the beneficial effects achieved. Thus, for the implementation of the device, reference is made to the thirteenth aspect and possible implementations of the method according to the thirteenth aspect. The same details are not repeated.

According to a fifteenth aspect, an embodiment of the present invention provides a main network device including a processor, a memory, a bus, and a communication interface, where the memory is configured to store an instruction executable on a computer, the processor and the memory are connected by a bus, and when running host network device, the processor executes an instruction on the computer stored in memory to enable the host network device to execute the method of any of the thirteenth aspect or possible implementations of the thirteenth aspect. Based on the same concept of the invention, the processor invokes the stored inductions to implement the decision in the development of the method in the eleventh aspect. In order to realize the solution of the technical problem and the beneficial effect of the main network device, reference is made to the thirteenth aspect, possible implementations of the method in accordance with the thirteenth aspect and their beneficial effects. Thus, for the implementation of the main network device, reference is made to the implementation of the method. The same details are not repeated.

According to a sixteenth aspect, an embodiment of the present invention provides a computer storage medium including an instruction, when executed on a computer, the computer is configured to perform the intersystem transfer method of the thirteenth aspect.

According to a seventeenth aspect, an embodiment of the present invention provides a computer program product including an instruction, when executing the computer program product on the computer, the computer is configured to perform the intersystem movement method of the thirteenth aspect.

Additionally, in order to explain the technical effects of any of the methods in the fifteenth aspect to the seventeenth aspect, reference is made to the technical effects of the thirteenth aspect. Details are not described here again.

According to an eighteenth aspect, an inter-system migration method is provided, including: obtaining information by a first primary network device that a UE is registered with a second primary network device in a first communication system; receiving by the first main network device the first message sent by the third main network device of the second communication system, and obtaining information based on the first message that the UE has entered the second communication system; and sending, by the first primary network device, a second message to the second primary network device based that the UE has performed dual registration, where the second message is used to notify the second primary network device that the UE has entered the second communication system. According to the intersystem roaming method presented in this embodiment of the present invention, when determining whether a first session exists in the first communication system, the UE sends a first message to the first primary network device of the second communication system to establish a second session in the second communication system, where the second session corresponds to the first session. The third primary network device obtains a first session ID and a third session ID, where the third session is a session on the first communication system, not transferable from the first communication system to the second communication system. Then, the third primary network device deletes the first session based on the first session ID. Since the second session in the second communication system corresponds to the first session in the first communication system, deleting the first session in the first communication system implements the transfer of the first session. Additionally, the fourth main network device sends a fourth message to the fourth main network device corresponding to the second session ID, wherein the fourth main network device deletes the third session corresponding to the third session ID, i.e., deletes the session without the possibility of transfer. Thus, a non-transferable session is deleted while the UE moves between communication systems.

In an exemplary implementation, before the first primary network device sends a second message to the first primary network device on the basis that the UE supports dual registration, the method includes: when the UE registers with the first communication system, the first primary network device receives a third message from the second primary network device. device, and obtaining information based on the third message that the UE has performed dual registration. Such an implementation discloses a method for the first primary network device to know that the UE has performed dual registration.

According to a nineteenth aspect, an embodiment of the present invention provides a main network device, including: an acquisition unit configured to obtain information that a user device UE is registered with a second main network device in a first communication system; a receiving unit configured to receive a first message sent by the third primary network device of the second communication system, wherein the receiving unit is further configured to receive information based on the first message that the UE has entered the second communication system; and a sender configured to send a second message to the second primary network device based that the UE has performed dual registration, where the second message is used to notify the second primary network device that the UE has entered the second communication system. According to the core network device provided in this embodiment of the present invention, when determining whether a first session exists in the first communication system, the user device sends the first message to the first core network device of the second communication system to establish a second session in the second communication system. where the second session corresponds to the first session. The third primary network device obtains a first session ID and a third session ID, where the third session is a session on the first communication system, not transferable from the first communication system to the second communication system. Then, the third primary network device deletes the first session based on the first session ID. Since the second session in the second communication system corresponds to the first session in the first communication system, deleting the first session in the first communication system implements a session transfer. In addition, the fourth main network device sends a fourth message to the fourth main network device corresponding to the second session ID, so that the fourth main network device deletes the third session corresponding to the third session ID, that is, deletes the session without being able to be transferred. Thus, a non-transferable session is deleted while the UE moves between communication systems. Based on the same concept of the invention, in order to present the principle of solving the technical problem and the beneficial effect of the device, reference is made to the eighteenth aspect, possible implementations of the method in accordance with the eighteenth aspect, and the beneficial effects achieved. Thus, for the implementation of the apparatus, reference is made to the eighteenth aspect and possible implementations of the method in accordance with the eighteenth aspect. The same details are not repeated.

According to a twentieth aspect, an embodiment of the present invention provides a main network device including a processor, a memory, a bus, and a communication interface, where the memory is configured to store an instruction executable on a computer, the processor and the memory are connected via a bus, and when running host network device, the processor executes an instruction on the computer stored in memory to enable the host network device to execute the method according to any of the eighteenth aspect or possible implementations of the eighteenth aspect. Based on the same inventive concept, the processor calls the instruction stored in the memory to implement the decision of the method in the sixteenth aspect. To implement the solution of the technical problem and the beneficial effect of the main network device, reference is made to the eighteenth aspect, possible implementations of the method in accordance with the eighteenth aspect and their beneficial effects. Thus, for the implementation of the main network device, reference is made to the implementation of the method. The same details are not repeated.

According to a twenty-first aspect, an embodiment of the present invention provides a computer storage medium including an instruction, when executed on a computer, the computer is configured to perform the inter-system transfer method in the eighteenth aspect.

According to a twenty-second aspect, an embodiment of the present invention provides a computer program product including an instruction, when executing the computer program product on the computer, the computer is configured to execute the intersystem transfer method in the eighteenth aspect.

Additionally, the technical effects obtained by any implementation of the method in the twentieth aspect through the twenty-second aspect can be obtained with reference to the technical effects obtained in the eighteenth aspect. Details are not repeated.

Brief description of the drawings

In order to more clearly describe the technical solutions in the embodiments of the present invention or in the prior art, the following is a brief description of the accompanying drawings necessary to describe the embodiments or the prior art.

1 is a schematic architectural diagram of a communication system in accordance with an embodiment of the present invention;

Fig. 2 is a block diagram of devices in a communication system according to an embodiment of the present invention;

3 is a flowchart of an intersystem transfer method according to an embodiment of the present invention;

4A and 4B are flowcharts of another intersystem transfer method according to an embodiment of the present invention;

Fig. 5 is a flowchart of a 5G UE registration process in the prior art;

6 is a flowchart of a 5G UE registration process according to an embodiment of the present invention;

Fig. 7 is a flowchart of a method for establishing a session PDU in 5G in the prior art;

8 is a flowchart of a 5G session PDU establishment process according to an embodiment of the present invention;

Fig.9 and Fig.9B are a flowchart of the algorithm of another method of intersystem movement in accordance with an embodiment of the present invention;

Fig. 10A and Fig. 10B are flowcharts of yet another intersystem transfer method in accordance with an embodiment of the present invention;

Fig. 11 is a block diagram of a UE according to an embodiment of the present invention;

Fig. 12 is a block diagram of another UE according to an embodiment of the present invention;

Fig. 13 is a block diagram of yet another UE, in accordance with an embodiment of the present invention;

Fig. 14 is a block diagram of a second main network device according to an embodiment of the present invention;

Fig. 15 is a block diagram of another second main network device according to an embodiment of the present invention;

Fig. 16 is a block diagram of yet another second main network device according to an embodiment of the present invention;

Fig. 17 is a block diagram of a third main network device according to an embodiment of the present invention;

Fig. 18 is a block diagram of another third main network device according to an embodiment of the present invention;

Fig. 19 is a block diagram of another third main network device according to an embodiment of the present invention;

Fig. 20 is a block diagram of a fifth main network device according to an embodiment of the present invention;

Fig. 21 is a block diagram of another fifth main network device according to an embodiment of the present invention; And

Fig.22 is a block diagram of another fifth main network device in accordance with an embodiment of the present invention.

Description of Embodiments

Embodiments of the present invention are described below with reference to the accompanying drawings.

The network architecture and service scenario described in the embodiments of the present invention are intended to more clearly describe the technical solutions in the embodiments of the present invention, and do not represent any limitation of the technical solutions provided in the embodiments of the present invention. The person skilled in the art will appreciate that with the development of network architectures and the advent of new service scenarios, the technical solutions proposed in the embodiments of the present invention are also applicable to similar technical problems. It should be noted that the solutions in the embodiments of the present invention can also be applied to another wireless communication network, and the corresponding name can also be changed to the name of the corresponding function in another wireless communication network.

1 is a network architecture diagram of a communication system according to an embodiment of the present invention, including: a UE 101, an Evolved UMTS Terrestrial Radio Access Network (E-UTRAN) 102, a Mobile Management Node 103 Management Entity, MMA), Serving Gateway (SGW) 104, User Plane Function (UPF) + Gateway-Control plane PDN 105, Session Management Function (SMF) ) + Gateway-User plane PDN (PDN Gateway-User plane, PGW-U) 106, policy control function (PCF) block 107 + Policy and Charging Rules Function (PCRF), reference subscriber server (Home Subscriber Server, HSS) + Unified Management Data (UDM) 108, Access and Mobility Management Function (AMF) 109 and 5G Radio Access Network (5G-RAN) 110.

E-UTRAN 102 is a 4G base station and the UE can access the 4G communication system using the base station. The 5G-RAN 110 is a 5G base station and the UE can access the 5G communication system with the base station. The 5G-RAN may be an evolved E-UTRAN through which a UE can access a base station of a 5G communication system. Alternatively, the 5G-RAN may be a base station specifically used by the UE to access the 5G communication system.

The MME 103 is a 4G network core device that performs authentication, authorization, mobility management, and session management of the UE. The Linked EPS Bearer ID (LBI) of the protocol data network (PDN) connection (Connection or Connectivity) of the 4G UE is allocated by the node.

The SGW 104 is a 4G core network gateway and is designed for data forwarding, downlink data storage, and the like.

UPF+PGW-U 105 is the main network device shared in 4G and 5G, namely the main network device integrated for 4G and 5G, and includes the functions of UPF and PGW-U. The UPF is a 5G user plane device of the core network, and provides a user plane service for a UE session PDU, and is a gateway interface between the operator's network and the external network. The PGW-U is a 4G core network user plane device, and provides a user plane service for a UE connection PDN, and is a gateway interface between the operator network and the external network. UPF + PGW-U may also be referred to as PGW-U + UPF and includes any device that has both UPF and PGW-U functions.

SMF + PGW-C 106 is the main network device shared by 4G and 5G, namely, the main network device is integrated for 4G and 5G, and includes the functions of SMF and PGW-C. The SMF is a 5G control plane device of the core network, and provides a control plane service for a UE session PDU, manages a session PDU and QoS in 5G, and is for assigning an IP address to a UE and selecting a UPF for the UE. The PGW-C is a 4G core network control plane device and provides a user plane service for a connection PDN of a UE, and is dedicated to assigning an IP address to the UE and establishing an EPS channel for the UE. SMF + PGW-C can also be referred to as PGW-C + SMF and includes any device that has SMF and PGW-C functions.

PCF + PCRF 107 is the main network device shared by 4G and 5G, namely the main network device integrated for 4G and 5G, and includes PCF and PCRF. PCRF is the main 4G network device, and is intended to generate a policy used by the user to establish a data transmission channel (bearer). PCF is the main 5G network device, and has the same function as PCRF. PCF + PCRF may also be referred to as PCRF + PCF and includes any device that has PCF and PCRF functionality.

UDM + HSS 108 is the main network device shared by 4G and 5G, namely the main network device integrated for 4G and 5G, and includes HSS and UDM. The HSS is a core 4G network device and is configured to store the user's subscription data. The UDM is a core 5G network device and is configured to store the user's subscription data. UDM + HSS may also be referred to as HSS + UDM and includes any device that has HSS and UDM functionality.

The AMF 109 is a core 5G network device, and is configured to perform authentication and authorization for the user and manage the user's mobility.

The Nx interface is the interface between MME 103 and AMF 109, and currently, this interface is optional. When the network supports the Nx interface, the network instructs the UE to perform a single registration (single registration). When the network does not support the Nx interface, but the UE supports dual registration, the network instructs the UE to perform dual registration. In this embodiment of the present invention, one registration means that the UE can register with only one communication system (eg, 4G or 5G) at a time. Dual registration means that the UE can register with two communication systems (for example, 4G and 5G) at the same time, but communicates using only one of the communication systems at a certain time, for example, communicates using the session PDU set in 5G, or communicate using a PDN connection established in 4G.

2 is a block diagram of hardware devices in accordance with an embodiment of the present invention. UE 100 includes at least one processor 101, at least one memory 102, and at least one transceiver 103. Optionally, UE 100 may further include an output device 104 and an input device 105.

The processor 101, the memory 102, and the transceiver 103 are connected via a bus. The processor 101 may be a central processing unit (CPU), a microprocessor, an application-specific integrated circuit (ASIC), or one or more integrated circuits configured to control the execution of the solution programs of the present invention. The processor 101 may alternatively be a plurality of processors, each processor may be a single-core (single-CPU) processor or a multi-core processor (multi-CPU). A processor, as used herein, may be one or more devices, circuits, and/or processing cores for processing data (eg, a computer program instruction).

Memory 102 may be read-only memory (ROM), another type of static storage device that can store static information and instructions, random access memory (RAM), or another type of dynamic storage device. which can store information and instructions; or may be electrically erasable programmable read-only memory (EEPROM), compact disc read-only memory (CD-ROM) or other optical disc storage device, optical storage disc (including compact optical disc, laser disc, optical disc, digital versatile disc, Blu-ray optical disc, or the like), magnetic disk media or other magnetic storage device, or any other media that can be used for transferring or storing the required program code in the form of instructions or data structures, and which can be accessed by a computer, but is not limited to. The memory 102 may exist independently and is connected to the processor 101 via a bus. The memory 102 may alternatively be integrated with the processor 101. The memory 102 is configured to store the application program code for carrying out the solution of the present invention, and the processor 401 controls the execution of the application program code. The processor 401 is configured to execute the computer program code stored in the memory 403 to implement the methods described in the embodiments of the present invention.

The transceiver 103 may be any type of transceiver, and is configured to connect to another device or communication network such as Ethernet, radio access network (RAN) or wireless local area network (wireless local area network, WLAN). The transceiver 103 includes a Tx transmitter and an Rx receiver.

Output device 104 communicates with processor 401 and can display information in a variety of ways. For example, the output device 104 may be a liquid crystal display (LCD), a light emitting diode (LED), a display device, a cathode ray tube (CRT) display device, a projector, or the like. The input device 105 communicates with the processor 101 and can receive user input in a variety of ways. For example, the water device 105 may be a mouse, keyboard, touch screen, touch device, or the like.

Base station 200 (E-UTRAN 102 or 5G-RAN 110) includes at least one processor 201, at least one memory 202, at least one transceiver 203, and at least one network interface 204. The network interface 204 is configured to connect to the network interface 304 of the main network device 300 using a communication line (for example, the S1 interface), or connect to the network interface 204 of another base station using a wired or wireless connection (for example, the X2 interface). For the functions of the components of the base station 200, reference may be made to the description of the functions of the components of the UE 100. Details not described here again.

The primary network device 300 may provide additional network connections, such as connections to a telephone network and/or a data network (eg, the Internet). The main network device 300 includes at least one processor 301, at least one memory 302, and at least one network interface 304. For the functions of the components of the main network device 300, reference is made to the description of the functions of the components of the UE 100. The details are not described here again.

The intersystem movement method, device, and system provided in the embodiments of the present invention are mainly used to transfer the first UE session in the first communication system from the first communication system to the second communication system. Essentially, the transfer of the first session is the formation of the second session in the second communication system and removes the original first session, where the second session corresponds to the first session. Additionally, the third UE session is a non-transferable session from the first communication system to the second communication system to be removed from the first communication system.

The first communication system may be a 5G communication system and the second communication system is a 4G communication system. In this case, the first session is a session PDU and the second session is a connection PDN. Alternatively, the first communication system is a 4G communication system, the second communication system is a 5G communication system, the first session is a PDN connection, and the second session is a PDU session.

For example, in the dual registration mode, when seamless transfer of a session PDU established by a UE in 5G to 4G is possible, the AMF selects for the UE an SMF + PGW-C network element shared or integrated for 5G and 4G. Thus, during the seamless transfer, the session IP address of the UE does not change and use the same SMF + PGW-C network element before and after the transfer. Seamless transfer of a session PDU established by a UE in 5G to 4G essentially establishes a connection corresponding to the original PDU in the 4G PDN, and then deletes the original 5G session PDU to achieve the goal of seamless transfer. It should be noted that a session PDU or PDN connection is described in this embodiment of the present invention for one UE and only for the corresponding UE, but does not apply to session PDUs or PDN connections of multiple UEs or another UE.

In this embodiment of the present invention, that it is possible to transfer the first session from the first communication system to the second communication system includes: the first primary network device serving the first session is the primary network device shared by the first communication system and the second communication system, and the third the underlying network device (eg, SMF + PGW-C), provides the control plane service for the first session; or both the first primary network device and the second primary network device serving the first session are primary network devices shared by the first communication system and the second communication system, the first primary network device (e.g., SMF+PGW-C) provides a control plane service for the first session, and the second primary network device (eg, UPF + PGW-U) provides the user plane service for the first session.

In this embodiment of the present invention, that it is possible to transfer the first session from the first communication system to the second communication system can be explained as: the first session supports interworking between the first communication system and the second communication system, or the first session supports Interworking ) from the first communication system to the second communication system, or the SMF + PGW-C main network device serving the first session supports interworking, or the SMF + PGW-C and UPF + PGW-U main network devices that serve the first session support the interworking or primary network device SMF + PGW-C that serves the first session is a network element specially configured for interworking between the first communication system and the second communication system, or the basic network devices SMF + PGW-C and UPF + PGW -U that serve the first session are network elements specially configured for interworking between the first communication system and the second communication system.

In this embodiment of the present invention, the main network device shared by the first communication system and the second communication system should be considered as: the main network device is a main network device specially used for interworking between the first communication system and the second communication system .

In this embodiment of the present invention, what the second session corresponds to the first session may include: the first session and the second session have the same IP address; or the first session and the second session have the same IP address and the same first primary network device and the first primary network device (eg, SMF+PGW-C) provides the control plane service for the first session; or the first session and the second session have the same IP address, the same first primary network device, and the same second primary network device, the first primary network device (for example, SMF + PGW-C), provides control plane service for the first session and the second primary network device (eg UPF+PGW-U) provides the user plane service for the first session.

This embodiment of the present invention illustrates examples of various messages for conveying information, but is not intended to be limited to a particular message name. For example, the first message, the second message, or the like may be used to represent a particular message name, or an appropriate message name may be used based on a particular communication system. Similarly, this embodiment of the present invention contains examples of various names of the main network devices, but is not intended to limit the specific name of the main network device. For example, a first primary network device, a second primary network device, or the like may be used to represent a specific primary network device, or an appropriate primary network device name may be used based on a particular communication system.

An embodiment of the present invention provides an intersystem transfer method. As shown in figure 3, the method includes the following steps.

S101. The UE determines whether there is a first session in a session established in the first communication system, where it is possible to transfer the first session from the first communication system to the second communication system.

S102. The UE sends the first message or the second message to the first primary network device of the second communication system if it is determined that the first session exists, where the first message is used to establish a second session in the second communication system, the second session corresponds to the first session, and the second message is used to perform an update tracking area update (TAU) in the second communication system.

For example, the first primary network device may be an MME and the first message may be a join request message, a PDN connection request message, or the like.

It should be noted that the second message may be sent when the UE determines that the first session exists or when another condition is met (e.g., the UE does not support dual registration, the UE does not support join without PDN connection (Join without PDN connection), or the network does not supports join without PDN connection (join without PDN connection).

S103. The UE sends a third message to the first primary network device of the second communication system upon determining that there is no first session, where the third message is used to perform joining to the second communication system.

In particular, the third message can be used to perform the initial (initial) connection to the second communication system. An initial attachment is an attachment message carrying an indication of an initial attachment, or an attachment message carrying an indication of an initial request (initial Request) in the Request Type field of the attachment message.

It should be noted that this step may be performed when the UE determines that there is no first session or when another condition is met. For example, this step may be performed when the UE determines that there is no first session and that the UE or the second communication system does not support the indicated feature. Said feature includes attaching to a second communication system without a PDN connection (attach without PDN connectivity).

S104. The first primary network device receives the first message, or the second message, or the third message, and obtains the fourth message based on the first message.

The fourth message is used to establish a second session in the second communication system, and the second session corresponds to the first session in the first communication system. The first primary network device may also perform a tracking area update procedure based on the second message, or perform an attach procedure based on the third message. Details are not described here.

S105. The first primary network device sends a fourth message to the second primary network device.

For example, the second primary network device may be an SMF + PGW-C and the fourth message may be a session establishment request message.

There may be another primary network device, such as an SGW, between the first primary network device and the second primary network device.

S106. The second primary network device receives the fourth message.

S107. The second primary network device receives the first session ID.

S108. The second primary network device sends the fifth message to the third primary network device.

The fifth message includes a first session identifier and is used to request a third primary network device to delete the first session.

For example, the third primary network device may be an AMF and the fifth message may be a session delete request.

S109. The third primary network device receives the fifth message.

S110. The third primary network device receives a first session ID and a third session ID.

The third session is a session in the first communication system without the possibility of transfer from the first communication system to the second communication system.

S111. The third primary network device deletes the first session based on the first session ID.

For example, the third primary network device may be an AMF, and the AMF removes the match between the first session ID and the second primary network device.

S112. The third primary network device sends a sixth message to the fourth primary network device corresponding to the second session ID, in which the sixth message is used by the fourth primary network device to delete the third session corresponding to the third session ID.

For example, the fourth primary network device may be an SMF and the sixth message may be a session delete request. The SMF initiates a third session removal procedure based on the third session ID in the sixth message.

According to the intersystem roaming method presented in this embodiment of the present invention, upon determining that a first session exists in the first communication system, the UE sends a first message to the first primary network device of the second communication system to establish a second session in the second communication system, where the second session corresponds to first session. The third primary network device obtains a first session ID and a third session ID, where the third session is a session on the first communication system, not transferable from the first communication system to the second communication system. Then, the third primary network device deletes the first session based on the first session ID. Since the second session in the second communication system corresponds to the first session in the first communication system, deleting the first session in the first communication system implements the transfer of the first session. In addition, the fourth main network device sends a sixth message to the fourth main network device corresponding to the second session ID, so that the fourth main network device deletes the third session corresponding to the third session ID, that is, the session is deleted without transfer. Thus, a non-transferable session is deleted during UE handover between communication systems.

It should be noted that the above contents only show examples of several possible implementations of the indication information, as well as other implementation of the indication information, which can be identified by a person skilled in the art and a combination of the above implementations should also be within the protection scope of the embodiments of the present invention.

Perhaps with reference to FIG. 4A, before step S101, the method further includes the following step:

S113. The UE receives indication information during the first session establishment process in the first communication system, where the indication information is used to indicate that the transfer of the first session from the first communication system to the second communication system is possible, or the indication information is used by the UE to determine that the transfer of the first session is possible. from the first communication system to the second communication system.

When the indication information is used by the UE to determine that it is possible to transfer the first session from the first communication system to the second communication system, the indication information includes one or a combination of the following information:

The parameter is related to the session in the second communication system corresponding to the first session: when the UE receives the parameter related to the session, the UE may determine that it is possible to transfer the session from the first communication system to the second communication system. When the UE does not receive the session-related parameter, the UE may determine that it is not possible to transfer the session from the first communication system to the second communication system. The session-related parameter herein includes one or more of a Quality of Service (QoS) parameter, a Traffic Flow Template (TFT), and an EPS bearer ID (EBI).

Service and Session Continuity mode (SSC mode) of the first session: when the SSC mode received by the UE is the specified mode (eg, 1), then the UE may determine that session transfer from the first communication system to the second system is possible connections. When the SSC mode received by the UE is not the specified mode (eg, 2 or 3), then the UE may determine that it is not possible to transfer the session from the first communication system to the second communication system.

First session IP address: When the IP address received by the UE belongs to the specified segment IP address, the UE may determine that session transfer from the first communication system to the second communication system is possible. When the IP address received by the UE does not belong to the specified IP address of the segment, then the UE may determine that it is not possible to transfer the session from the first communication system to the second communication system.

Slicing information to which the first session belongs: for example, the information is Single Network Slice Selection Assistance Information (S-NSSAI). When the UE determines that the network segment corresponding to the S-NSSAI has a corresponding service in the second communication system, the UE may determine that session transfer from the first communication system to the second communication system is possible. When the UE determines that the network segment corresponding to the S-NSSAI can only be used in the first communication system, then the UE may determine that it is not possible to transfer the session from the first communication system to the second communication system. For example, a Mobile Broadband (MBB) service can be used in both the first communication system and the second communication system, while the high security service bank type can only be used in the first communication system and is not corresponding service in the second communication system.

Data Network Name (DNN) corresponds to the first session: if there is an Access Point Name (APN) corresponding to the data network name, the UE can determine that it is possible to transfer the first session from the first communication system to the second system connections. In the absence of an access point name corresponding to the data network name, the UE may determine that it is not possible to transfer the first session from the first communication system to the second communication system.

It should be noted that when the indication information is a combination of a plurality of pieces of information, the UE can determine, only by determining that each piece of information satisfies the transfer condition, that the transfer of the first session from the first communication system to the second communication system is possible. In other words, if any piece of information does not meet the transfer condition, then the UE may determine that the transfer of the first session cannot be implemented from the first communication system to the second communication system. For example, if the indication information is a combination of the SSC mode and the DNN when the SSC mode is a given mode (eg, 1) and the DNN has a corresponding APN, then the UE may determine that session transfer from the first communication system to the second communication system is possible. . As another example, if the indication information is a combination of an SSC mode and a network segment, when the SSC mode is a predetermined mode (eg, 1), the network segment does not have a corresponding service in the second communication of the system, the UE may determine that it is not possible to transfer the session from the first communication system to the second communication system.

It should be noted that the above contents only show examples of several possible implementations of indication information, as well as other implementation of indication information that can be obtained by a person skilled in the art and a combination of the above implementations, which should also be within the protection scope of embodiments of the present invention. .

Possibly with reference to FIG. 4B, before step S110, the method further includes the following steps:

S114. The fifth primary network device learns that the UE is registered with the third primary network device of the first communication system.

For example, the fifth primary network device may be a UDM + HSS.

S115. The fifth main network device receives the seventh message from the first main network device of the second communication system, and learns, based on the seventh message, that the UE has entered the second communication system. That the UE has entered the second communication system can be understood as: the UE is currently in the second communication system or the UE has performed a registration or location update in the second communication system.

For example, the seventh message may be a location update request.

S116. The fifth primary network device sends an eighth message to the third primary network device based that the UE has performed dual registration, where the eighth message is used to notify the third primary network device that the UE has been moved to the second communication system. That the UE has moved to the second communication system can be considered as: the UE is currently in the second communication system or the UE has performed a registration or location update in the second communication system.

The following describes in detail an example of an intersystem migration method in which the first communication system is a 5G communication system, the second communication system is a 4G communication system, the first session is the first session PDU, and the second session is a PDN connection, and the third session is the second session PDU. It should be noted that a person skilled in the art can understand that the method of intersystem transfer in this embodiment of the present invention can also be applied to transfer in the reverse direction. More specifically, the first communication system is 4G, the second communication system is 5G, and the PDN connection in 4G is transferred from 4G to 5G.

In particular, the intersystem relocation method in this embodiment of the present invention improves a 5G UE registration procedure, a 5G session PDU generation procedure by a UE, and a 4G UE registration procedure during a seamless handover from 5G to 4G UE session PDU in 5G.

In the prior art, the 5G UE registration procedure is shown in FIG. 5 and includes the following steps.

S201. The UE initiates a Registration Request for a new AMF (AMF currently serving the UE) using 5G-RAN, in which the registration request includes indication information, and the indication information is used to indicate whether the UE supports dual registration , or the indication information is used to indicate that the UE supports single registration or dual registration.

S202. When the new AMF is different from the previous AMF (Serving UE AMF when the UE performs deregistration), the new AMF requests the UE context information from the previous AMF with Information Request and Information Response between the new AMF and the previous AMF. AMF.

S203. When the new AMF or the predecessor AMF fails to validate the UE, the new AMF requests the UE's International Mobile Subscriber Identification Number (IMSI) from the UE using an Identity Request and an Identity Response between the new AMF and U.E.

S204. The new AMF validates the UE based on the IMSI using an Authentication message and a Security message.

S205. The new AMF sends an Update Location Request to the UDM+HSS, where the location update request includes the UE IMSI and the AMF identity.

The UDM+HSS may know, based on the location update request, that the UE has registered with the AMF, or the UE has registered with the 5G communication system, or the UE has moved to the 5G communication system.

S206. The UDM+HSS returns an Update Response to the AMF, where the Location Update Response includes the UE's subscription data.

S207. The new AMF requests operator policies from the PCF using a UE Context Establishment Request and a UE Context Establishment Acknowledge.

S208. The new AMF determines whether the UE performs single registration or dual registration.

S209. The new AMF sends a Registration Accept message to the UE, where the Registration Accept message includes registration result information, and the registration result information is used to direct the UE to perform single registration or dual registration.

S210. The UE returns a Registration Complete message to the new AMF.

Steps S202-S204 are possible, and when the new AMF is the same as the previous AMF, steps S202-S204 are not performed.

An embodiment of the present invention improves the UE registration procedure in 5G. For more information, refer to FIG. 6. The following steps are optional.

S211. If the AMF determines that the UE should dual-register, the AMF sends a request message to the UDM+HSS to notify the AMF that the UE should dual-register, wherein the request message further includes the IMSI at the UE, and the request message may be, for example, a notification request (Notify Request).

S212. UDM + HSS receives a request message.

When using step S212, the UDM + HSS may know whether the UE should perform dual registration.

S213. The UDM + HSS returns a response message to the UDM, where the response message could be, for example, a Notify Response message.

In the prior art, the procedure for generating a session PDU in 5G after registering a UE in 5G is shown in FIG. 7 and includes the following steps:

S301. In the 5G communication system, the UE sends a session establishment request PDU message to the AMF to request to establish a session PDU in the 5G communication system, where the session PDU establishment request includes Single Network Slice Selection Facilitation information. Selection Assistance Information, S-NSSAI), the Data Network Name (DNN) of the corresponding session PDU, and the session PDU ID (session ID).

S302. The AMF receives a session PDU request message.

S303. If the AMF determines, based on the DNN, S-NSSAI, subscription information, operator policy, and the like, that the session PDU can be transferred to the 4G communication system, the AMF selects the Session Management Function (SMF) shared with 4G communication system or corresponding session management function, namely SMF + PGW-C.

S304. The AMF sends a PDU Establishment Request to the SMF+PGW-C to initiate a session management request (SM Request), where the session PDU establishment request includes a persistent UE identifier, DNN, S-NSSAI, session PDU ID and AMF identifier (AMF ID).

S305. If there is no UE subscription data corresponding to the DNNs on the SMF + PGW-C, the SMF + PGW-C sends a Subscription Data Request message to the UDM + HSS to request the subscription data corresponding to the DNNs from the UDM + HSS.

S306. The UDM + HSS returns a Subscription Data Response message to the SMF + PGW-C, where the Subscription Data Response message includes the subscription data corresponding to the DNN.

S307. When using Policy and Charging Control (PCC) dynamically, the SMF + PGW-C requests the appropriate PCC policy from the PCF + PCRF using a PDU-CAN Session Establishment Request message and a response message. establishing a session PDU-CAN (PDU-CAN Session Establishment Response).

S308. The SMF + PGW-C initiates a session establishment request to the UPF + PGW-U with a Session Establishment Request message and a Session Establishment Response message.

S309. The SMF + PGW-C sends a PDU Establishment Accept message to the AMF to acknowledge the session management request (SM Request ACK).

S310. The AMF sends a PDU Session Establishment Accept message to the UE.

Steps S305-S307 are optional.

An embodiment of the present invention improves the procedure for generating a session PDU in 5G by a UE. For more information, refer to FIG. 8. Use the following steps.

In step S310, the session PDU establishment permission message includes indication information, in which the indication information indicates whether it is possible to transfer the established session PDU from the first communication system (for example, 5G) to the second communication system (for example, 4G), and the AMFs store the information whether it is possible to transfer the session PDU from the first communication system to the second communication system.

Alternatively, the indication information is used by the UE to determine whether the first session can be transferred from the first communication system to the second communication system, and the indication information includes one or a combination of the following information:

Session related parameter in the second communication system corresponding to the first session: When the UE receives the session related parameter, the UE may determine that it is possible to transfer the session from the first communication system to the second communication system. When the UE does not receive the session related parameter, the UE may determine that it is not possible to perform a session transfer from the first communication system to the second communication system. The session-related parameter herein includes one or more of a Quality of Service (QoS) parameter, a Traffic Flow Template (TFT), and an EPS bearer ID (EBI) .

Service and Session Continuity mode (SSC mode) of the first session: when receiving the SSC mode by the UE, this mode is the specified mode (for example, 1), then the UE may determine that it is possible to transfer the session from the first communication system to second communication system. When the SSC mode received by the UE is not the specified mode (eg, 2 or 3), then the UE may determine that it is not possible to transfer the session from the first communication system to the second communication system.

First session IP address: When the IP address received by the UE belongs to the specified segment IP address, the UE may determine that session transfer from the first communication system to the second communication system is possible. When the IP address received by the UE does not belong to the specified IP address segment, then the UE may determine that the session cannot be transferred from the first communication system to the second communication system.

Information about the network segment (Slicing) to which the first session belongs: for example, the information is Single Network Slice Selection Assistance Information (S-NSSAI). When the UE determines that the network segment corresponding to the S-NSSAI has a corresponding service in the second communication system, then the UE may determine that session transfer from the first communication system to the second communication system is possible. When the UE determines that the network segment corresponding to the S-NSSAI can only be used in the first communication system, then the UE may determine that the session cannot be transferred from the first communication system to the second communication system. So, for example, a Mobile Broadband (MBB) service can be used in both the first communication system and the second communication system, while the high security service type can only be used in the first communication system and there is no corresponding service in the second communication system.

Data Network Name (DNN) corresponding to the first session: if there is an Access Point Name (APN) corresponding to the data network name, the UE can determine that it is possible to transfer the first session from the first communication system to the second communication system. In the absence of an access point name corresponding to the data network name, the UE may determine that the first session cannot be transferred from the first communication system to the second communication system.

It should be noted that when the indication information is a combination of a plurality of pieces of information, the UE can determine, only by determining that each piece of information satisfies the transfer condition, that the transfer of the first session from the first communication system to the second communication system is possible. In other words, if any piece of information does not meet the transfer condition, then the UE may determine that the first session cannot be transferred from the first communication system to the second communication system. For example, if the indication information is a combination of the SSC mode and the DNN, when the SSC mode is the specified mode (eg, 1) and the DNN has a corresponding APN, then the UE may determine whether to perform a session transfer from the first communication system to the second communication system. As another example, if the indication information is a combination of an SSC mode and a network segment, when the SSC mode is the specified mode (eg, 1), the network segment does not have a corresponding service in the second system link, then the UE may determine that session transfer cannot be performed. from the first communication system to the second communication system.

It should be noted that the above contents only show examples of a few possible implementations of the indication information and other implementations of the indication information are possible, which can be understood by a person skilled in the art and a combination of the above implementations should also be within the protection scope of the embodiments of the present invention.

Specifically, the established session PDU is classified into a first session PDU and a second session PDU. The first session PDU is a session PDU capable of performing transfer from a first communication system (eg, 5G) to a second communication system (eg, 4G), or a session PDU that supports Interworking. The first session PDU is not limited to one session PDU and may include multiple session PDUs. Unlike the first session PDU, the second session PDU is a non-transferable session PDU from a first communication system (eg, 5G) to a second communication system (eg, 4G) or a session PDU that does not support interworking. Likewise, the second session PDU is not limited to a single session PDU and may include multiple session PDUs.

Such an implementation allows the UE to know if it is possible to transfer the established session PDU from the first communication system (eg, 5G) to the second communication system (eg, 4G).

Perhaps the AMF maps the DNN corresponding to the first session PDU to the APN corresponding to the first session PDU. Thus, the session PDU establishment permission message may further include mapped to an APN so that the UE may obtain an APN corresponding to the established first session PDU.

S311. The UE receives the session PDU establishment permission message, learns, based on the indication information, whether the transfer of the first communication system to the second communication system session PDU is possible, and stores the session PDU establishment permission message.

In other words, the UE can know whether it is possible to transfer from the first communication system (eg, 5G) to the second communication system (eg, 4G) a session corresponding to a session PDU (Session PDU ID).

The indication information may indicate, using various values, for example, true (true)/(false), whether it is possible to transfer the session PDU from the first communication system to the second system. Alternatively, the presence of the indication information indicates that the session PDU can be transferred from the first communication system to the second communication system. For example, the indication information is sent in a session PDU establishment permission message for a transferable session PDU from a first communication system to a second communication system; and the indication information is not transmitted in the session PDU establishment permission message for the session PDU without the ability to perform handover from the first communication system to the second communication system. Alternatively, the indication information is used by the UE to determine if the first session can be transferred from the first communication system to the second communication system. The indication information includes one or a combination of the following information: a session-related parameter in the second communication system corresponding to the first session, the SSC mode of the first session, the IP address of the first session, information about the network segment to which the first session belongs, and the network name data transfer corresponding to the first session.

S312. When the AMF determines that it can perform session PDU transfer from the first communication system to the second communication system, the AMF sends a Notify Request message to the UDM+HSS.

The notification request message may include a DNN corresponding to the first session PDU and an SMF + PGW-C address corresponding to the first PDU, or may include an APN corresponding to the first session PDU and an SMF + PGW-C address corresponding to the first PDU session.

The DNN corresponding to the first session PDU may be considered as the DNN used by the first session PDU. The APN corresponding to the first session PDU may be considered as the APN corresponding to the DNN. The SMF+PGW-C address corresponding to the first session PDU can be understood as the SMF+PGW-C address used by the first session PDU.

If the notification request message includes the APN corresponding to the first session PDU and the first session PDU, the AMF first obtains the DNN corresponding to the first session PDU and then obtains the APN corresponding to the DNN.

S313. UDM + HSS returns a Notify Response message to the AMF.

It should be noted that the execution sequence of step S310 and step S312 is not limited. In addition, steps S312 and S313 are possible. The SMF + PGW-C address corresponding to the DNN may also be contained in the subscription data request in step S305, in which case, steps S312 and S313 are not performed. The function of step S312, step S313, step S305 provides the UDM+HSS to obtain the SMF+PGW-C address corresponding to the set first session PDU.

An embodiment of the present invention provides an intersystem roaming method for improving a UE registration procedure with a second communication system (eg, 4G) during transfer of a 5G UE session PDU from a first communication system (eg, 5G) to a second communication system (eg, 4G). As shown in FIG. 9A and FIG. 9B, the method includes the following steps.

S401. When the UE moves from 5G to 4G to be performed, the UE determines whether it is possible to move the first session PDU from 5G to 4G to 5G.

This step corresponds to step S101.

When the UE has a plurality of first 5G to 4G bearable session PDUs in 5G, then the UE initiates a request to each first 5G to 4G bearable session PDU.

It should be noted that in step S311, the UE may know whether it is possible to transfer each session PDU from 5G to 4G.

S402. The UE initiates an Attach Request message to the new MME upon determining that a first session PDU exists in 5G.

This step corresponds to step S102.

The attach request message includes a handover indication, and hence the attach request is a handover attach request. The attach request message may further include a Ciphered Options Transfer Flag. It should be noted whether or not to add an encrypted option transmission flag in the attach request message may be determined by the UE. For example, if the UE determines that the APN corresponding to the first session PDU is not the default APN, or determines that the DNN corresponding to the first session PDU is not the default DNN, an encrypted options transmission flag is added to the attach request message.

It should be noted that when the UE determines that there is no session PDU with 5G to 4G transfer capability, the UE initiates an attach request including an initial attach indication.

S403. When the new MME (the MME currently serving the UE) differs from the previous AMF (the MME serving the UE when the UE performs a detach operation), the new MME requests context information about the UE from the previous MME using an Information Request and information response (Information Response).

S404. When the new MME or the predecessor MME fails to validate the UE, the new MME requests the IMSI of the UE from the UE using an Identity Request and an Identity Response between the new MME and the UE.

S405. The new MME validates the UE based on the IMSI using an Authentication message and a Security message.

S406. After the new MME verifies that the UE is valid, the new MME sends a Ciphered Options Transfer Request message to the UE.

Since the encrypted options transmission flag is transmitted in step S402, the new MME sends an encrypted options request message to the UE based on the encrypted options transmission flag.

S407. The UE receives an encrypted options request message.

S408. The UE obtains the APN corresponding to the first session PDU and sends a Ciphered Options Transfer Response message to the new MME, where the Ciphered Options Response message includes the APN.

In particular, there are two ways to obtain an APN:

Method 1: If the session PDU establishment permission message includes an APN in step S310, then the UE uses the APN directly.

Method 2: If the session PDU establishment permission message does not include an APN in step S310, then the UE obtains the APN corresponding to the first session PDU based on the locally stored matching DNN-APN and the DNN corresponding to the first session PDU and mapping the DNN of the first session PDU on APN.

S409. The new MME sends an Update Location Request to the UDM + HSS, where the location update request includes the IMSI of the UE and the ID of the new MME.

Perhaps the location update request may further include indication information indicating whether the UE should perform dual registration. If the MME determines that the UE should perform dual registration, the MME adds indication information indicating dual registration to the location update request; otherwise, the MME adds indication information indicating one registration to the location update request or does not add indication information to the location update request.

S410. The UDM+HSS receives the location update request, and learns, based on the location update request, that the UE has been moved to the second communication system. That the UE has entered the second communication system can be understood as: the UE is currently in the second communication system, or the UE has performed a registration or location update in the second communication system.

S411. The UDM + HSS returns an Update Location Response to the new MME, where the location update response includes the UE subscription data, the UE APN, and the SMF + PGW-C address corresponding to the APN.

Specifically, the UDM+HSS obtains the SMF+PGW-C address corresponding to the DNN in step S312, and the UDM+HSS stores the DNN-APN mapping locally. Thus, the UDM + HSS receives the SMF + PGW-C address corresponding to the APN and then sends the SMF + PGW-C address to the MME.

S412. After receiving the SMF+PGW-C address corresponding to the APN, the new MME sends a session creation request message to the corresponding SMF+PGW-C using the SGW, where the Create Session Request message includes the handover indication and the APN corresponding to the first Session PDU.

This step corresponds to steps S104 and S105.

The session formation request message is used to establish a PDN connection in 4G, and the PDN connection corresponds to the first session PDU in 5G.

S413. SMF + PGW-C receives a session formation request.

S414. The SMF + PGW-C returns a Create Session Response message to the new MME by using the SGW.

The SMF + PGW-C can obtain, based on the APN, in the session formation request message in step S412, the DNN corresponding to the APN, and obtain the corresponding IP address of the first session PDU based on the DNN; or SMF + PGW-C can directly obtain the corresponding IP address of the first session PDU based on the APN. It is possible that the SMF + PGW-C can derive the session PDU (PDU session ID) of the first session PDU based on the IP address. Perhaps the session formation response message includes an IP address.

S415. The new MME sends an Attach Accept message to the UE.

S416. The UE sends an Attach Complete message to the new MME.

S417. The new MME sends a Modify Bearer Request message to the SMF+PGW-C using the SGW.

The SMF + PGW-C learns that the UE has completed the transfer of the first session PDU from 5G to 4G.

S418. The SMF+PGW-C obtains a session PDU (PDU session ID) corresponding to the first session PDU.

In particular, two methods are used to obtain a session PDU corresponding to the first session PDU:

Method 1: If the SMF+PGW-C obtained the session PDU ID of the first session PDU in step S414, then the SMF+PGW-C directly uses the session PDU ID.

Method 2: If the SMF+PGW-C did not obtain the session PDU ID of the first session PDU in step S414, the SMF+PGW-C obtains the session PDU ID of the first session PDU based on the IP address of the first session PDU obtained in step S414.

S419. The SMF + PGW-C sends the first Delete Session Request to the UPF + PGW-U, where the first delete session request includes the identifier of the first session PDU obtained in step S418.

The first delete session request is used to request the UPF+PGW-U to delete the data of the first user plane session PDU.

S420. The SMF + PGW-C sends a second Delete Session Request to the AMF corresponding to the UE, where the second delete session request includes the identifier of the first session PDU obtained in step S415.

The first delete session request is used to request the AMF to delete the first session PDU data, and in particular the AMF request to locally delete the match between the first session PDU ID and the corresponding SMF + PGW-C.

Upon receiving the second delete session request, the AMF deletes the first session PDU based on the ID of the first session PDU.

S421. AMF receives a second session delete request.

S422. The UDM + HSS sends a notification message to the AMF based on the UE has performed dual registration to notify the AMF that the UE has performed a move from the first communication system (for example, 5G) to the second communication system (for example, 4G) (i.e., the UE is located currently in 4G).

In particular, the way the UDM + HSS knows that the UE has performed dual registration includes:

Method 1: In step S211, the UDM + HSS learns that the UE has performed dual registration.

Method 2: The UDM + HSS learns from the location update request in step S410 that the UE has performed dual registration.

S423. After receiving the notification message, the AMF may determine based on the message that the UE is currently in the second communication system.

S424. The AMF derives the ID of the second session PDU based on locally stored information about all session PDUs.

According to step S110, step S420 and step S424 disclose an approach for obtaining a first session PDU ID and a second session PDU ID by AMF.

S425. The AMF sends a third Delete Session Request to the SMF corresponding to the second session PDU to initiate the procedure for deleting the second session PDU.

In particular, the third session delete request uses the SMF to delete the second session PDU corresponding to the identifier of the second session PDU. The third session delete request includes a second session PDU identifier.

Upon receiving the third delete session request, the SMF deletes the second session PDU based on the ID of the second session PDU.

An embodiment of the present invention provides another intersystem roaming method for improving the registration procedure of 4G UEs during seamless transfer of 5G UE session PDUs from 5G to 4G. Referring to FIG. 10A and FIG. 10B, the method includes the following steps.

S501-S507 are the same as steps S401-S407 in FIG. 9A. Details are not described here again.

S508. Unlike step S408 in FIG. 9A, the encrypted options response message may further include a second session PDU identifier.

Specifically, the encrypted options response message includes a Protocol Configuration Option (PCO) and the PCO includes a second session PDU identifier.

S509-S511 are the same as steps S409-S411 in FIG. 9A. Details are not described here again.

S512. Unlike step S412 in FIG. 9A, the session formation request message may further include a second session PDU identifier.

Specifically, the session formation request message includes a PCO, and the PCO includes a second session PDU ID.

S513-S519 are the same as steps S413-S419 in FIG. 9A and FIG. 9B. Details are not described here again.

S520. Unlike step S420 in FIG. 9B, the second delete session request further includes a second session PDU identifier to request the AMF to delete the second session PDU.

According to step S110, step S520 discloses another approach for obtaining a first session PDU ID and a second session PDU ID by AMF.

It should be noted that the identifier of the second session PDU may alternatively be implemented in a separate message.

S521 is the same as step S421 in FIG. 9B and S522 is the same as step S425 in FIG. 9B. Details are not described here again.

It should be noted that in steps S401 and S501, if this is the first time the UE registers 4G, seamless transfer of one first session PDU from 5G to 4G can be performed using steps S401 and S501. After the UE completes the 4G registration, the UE can move to 4G by sending a PDN Connectivity Request to the MME, the other first session PDU with the ability to perform 5G to 4G seamless handover. The connection PDN request includes a handover indication and an APN corresponding to the first session PDU. Whether the access point name corresponding to the first session PDU should be added to the connection PDN request may be determined by the UE, or the APN corresponding to the first session PDU may be directly transmitted in the connection PDN request. For example, if the UE determines that the APN corresponding to the first session PDU is not the default APN or determines that the DNN corresponding to the first session PDU is not the default DNN, the APN corresponding to the first session PDU is added a connection PDN request.

An embodiment of the present invention provides a UE to perform the above intersystem moving methods. In this embodiment of the present invention, the division of functional modules for the UE may be based on the above method examples. For example, the separation of functional modules may be based on different functions, or two or more functions may be combined into one processing module. An integrated module may be implemented in hardware or may be implemented as a function of a software module. It should be noted that the division of the module in this embodiment of the present invention is an example, and is only a logical function of the division, and may be a different division in the actual implementation.

11 is a possible schematic block diagram of the UE described in the previous embodiment when the division of functional modules is based on different functions. The UE 10 includes a receiving block 1011, a determining block 1012, and a sending block 1013. The receiving unit 1011 is configured to support the UE 10 while executing the process S113 in FIG. 4A of process S311 in FIG. 8, process S407 in FIG. 9A and process S507 in FIG. 10A. The determiner 1012 is configured to support the UE 10 while executing process S101 in FIG. 3 and process S401 in FIG. 9A. The sender 1013 is configured to support the UE 10 while executing process S102 in FIG. 3, process S102 in FIG. 4A, processes S201 and S210 in FIG. 5, processes S201 and S210 in FIG. 6, process S301 in FIG. 7, process S301 in FIG. 8, processes S401, S408, S416, and in FIG. 9B and processes S501, S508, and S516 in FIG. 10. All contents relating to the various steps described in the above method embodiments can be applied to describing the functions of the respective functional modules. Details are not described here again.

Fig. 12 is an exemplary block diagram of the UE described in the foregoing embodiment of the invention in the case of integrated units. UE 10 includes a processing module 1022 and a communication module 1023. The processing module 1022 is configured to monitor and control the actions of the UE 10. For example, the processing module 1022 is configured to support the UE 10 while executing process S101 in FIG. 3 and process S401 in FIG. 9A. The communication module 1023 is configured to support communication between the UE and another entity, such as communication between the UE and the functional module or network entity in FIG. The user device 10 may further include a storage unit 1021 configured to store program code and data of the UE.

Processing module 1022 may be a processor or a controller. For example, the data processing module 1022 may be a Central Processing Unit (CPU), a general purpose processor, a digital signal processor (DSP), a user-programmable application-specific integrated circuit (ASIC). field programmable gate array (FPGA) or other programmable logic device, logic device transistor, hardware component, or any combination thereof. Processing module 1022 may implement or execute various examples of logical blocks, modules, and circuits described with reference to the content disclosed in this application. Alternatively, the processor may be a combination of processors that implement a computing function, such as a combination of one or more microprocessors, or a combination of a DSP and a microprocessor. The communication module 1023 may be a transceiver, a transceiver circuit, a communication interface, or the like. The storage module 1021 may be a memory.

When the processing unit 1022 is a processor, the communication unit 1023 is a transceiver, and the storage unit 1021 is a memory, then the UE described in this embodiment of the present application may be the next UE 10.

Referring to FIG. 13, UE 10 includes a processor 1032, a transceiver 1033, a memory 1031, and a bus 1034. The transceiver 1033, the processor 1032, and the memory 1031 are connected to each other via a bus 1034. The bus 1034 may be a peripheral component interconnect (PCI) bus. ), an extended industry standard architecture (EISA) bus, or the like. Buses can be classified into an address bus, a data bus, a control bus, and the like. For ease of presentation, in the drawing, only one thick line is used to indicate the tire, but this does not mean at all that there is only one tire or only one type of tire.

An embodiment of the present invention provides a second primary network device for performing the above intersystem migration methods. In this embodiment of the present invention, the division of functional modules for the second main network device may be based on method examples. For example, the separation of functional modules may be based on different functions, or two or more functions may be combined into one processing module. An integrated module may be implemented in hardware or may be implemented as a function of a software module. It should be noted that the division of the module in this embodiment of the present invention is an example, and is only a logical function of the division, and may be a different division in the actual implementation.

14 is a possible block diagram of the second main network device described in the previous embodiment when the division of functional modules is based on different functions. The second main network device 20 includes a receiving unit 2011, a receiving unit 2012, and a sending unit 2013. The receiving unit 2011 is configured to support the second main network device 20 while executing process S106 in FIG. 3, process S106 in FIG. 4A of process S413 in FIG. 9A and process S513 in FIG. 10b. The acquisition unit 2012 is configured to support the second main network device 20 while executing process S107 in FIG. 3, process S107 in FIG. 4A of process S418 in FIG. 9B and process S518 in FIG. 10b. The sender 2013 is configured to support the second main network device 20 while executing process S108 in FIG. 3, process S108 in FIG. 4B, processes S305 and S309 in FIG. 7, processes S305 and S309 in FIG. 8, processes S419 and S420 in FIG. 9B and processes S519 and S520 in FIG. 10b. All contents relating to the various steps described in the previous method embodiments can be applied to the description of the functions of the respective functional modules. Details are not described here again.

15 is a possible block diagram of the main network device described in the previous embodiment of the invention when the blocks are integrated. The second main network device 20 includes a processing module 2022 and a communication module 2023. The processing module 2022 is configured to monitor and control the activities of the second main network device 20. For example, the processing module 2022 is configured to support the second main network device 20 while executing process S107 in FIG. 3, process S108 in FIG. 4B of process S418 in FIG. 9B and process S518 in FIG. 10b. The communication module 2023 is configured to support communication between the main network device and another entity, such as communication between the main network device and the functional module or network entity in FIG. 1. The second main network device 20 may further include a storage unit 2021 configured to store program code and data of the main network device.

Processing module 2022 may be a processor or a controller. For example, the processing unit 2022 may be a Central Processing Unit (CPU), a general purpose processor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field programmable gate array (field programmable gate array, FPGA) or other programmable logic device, logic device transistor, hardware component, or any combination thereof. The processing module 2022 may implement or execute various examples of logical blocks, modules, and circuits described with reference to the content disclosed in this application. Alternatively, the processor may be a combination of processors that implement a computing function, such as a combination of one or more microprocessors, or a combination of a DSP and a microprocessor. The communication module 2023 may be a transceiver, a transceiver circuit, a communication interface, or the like. The storage module 2021 may be a memory.

When the processing unit 2022 is a processor, the communication unit 2023 is a transceiver, and the storage unit 2021 is a memory, the basic network device described in this embodiment of the present application may be the following basic network device.

Referring to FIG. 16, the second main network device 20 includes a processor 2032, a transceiver 2033, a memory 2031, and a bus 2034. The transceiver 2033, the processor 2032, and the memory 2031 are connected to each other via a bus 2034. component interconnect (PCI), extended industry standard architecture (EISA) bus, or the like. Buses can be classified into an address bus, a data bus, a control bus, and the like. For ease of presentation, in the drawing, only one thick line is used to indicate the tire, but this does not mean at all that there is only one tire or only one type of tire.

An embodiment of the present invention provides a third basic network device to perform the above intersystem migration methods. In this embodiment of the present invention, the division of functional modules for the main network device may be based on method examples. For example, the separation of functional modules may be based on different functions, or two or more functions may be combined into one processing module. An integrated module may be implemented in hardware or may be implemented as a function of a software module. It should be noted that the division of a module in this embodiment of this application is an example, and is only a logical division function, and may be a different division in the actual implementation.

17 is a possible block diagram of the main network device described in the previous embodiment when the division of functional modules is based on different functions. The third main network device 30 includes a receiving block 3011, a receiving block 3012, a deleting block 3013, and a sending block 3014. The receiving unit 3011 is configured to support the third main network device 30 while executing process S109 in FIG. 3, process S109 in FIG. 4B of process S302 in FIG. 7, process S302 in FIG. 8, processes S421 and S423 in FIG. 9B and process S521 in FIG. 10b. The acquisition unit 3012 is configured to support the third main network device 30 while executing process S110 in FIG. 3, process S110 in FIG. 4B of process S208 in FIG. 5, process S208 in FIG. 6, process S303 in FIG. 7, process S303 in FIG. 8 and process S424 in FIG. 9B. The removal unit 3013 is configured to support the third main network device 30 while executing process S111 in FIG. 3 and process S111 in FIG. 4B. The sender 3014 is configured to support the third main network device 30 while executing process S112 in FIG. 3, process S112 in FIG. 4B, processes S205 and S209 in FIG. 5, processes S205, S209, S211, and in FIG. 6, processes S304 and S310 in FIG. 7, processes S304, S310, S312, and in FIG. 8, process S425 in FIG. 9B and process S522 in FIG. 10b. All contents relating to the various steps described in the previous embodiments of the method can be applied to the description of the functions of the respective functional modules. Details are not described here again.

18 is a possible block diagram of the main network device described in the previous embodiment of the invention when the blocks are integrated. The third main network device 30 includes a processing module 3022 and a communication module 3023. The processing module 3022 is configured to monitor and control the activities of the third main network device 30. For example, the processing module 3022 is configured to support the third main network device 30 while executing processes S110 and S111 in FIG. 3, processes S110 and S111 in FIG. 4B of process S208 in FIG. 5, process S208 in FIG. 6, process S303 in FIG. 7, process S303 in FIG. 8 and process S424 in FIG. 9B. The communication module 3023 is configured to support communication between the main network device and another entity, such as communication between the main network device and the functional unit or network entity in FIG. 1. The third main network device 30 may further include a storage unit 3021 configured to store program code and data of the main network device.

Processing module 3022 may be a processor or a controller. For example, the processing unit 3022 may be a Central Processing Unit (CPU), a general purpose processor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field programmable gate array (field programmable gate array, FPGA) or other programmable logic device, logic device transistor, hardware component, or any combination thereof. The processing module 3022 may implement or execute various examples of logical blocks, modules, and circuits described with reference to the content disclosed in this application. Alternatively, the processor may be a combination of processors that implement a computing function, such as a combination of one or more microprocessors, or a combination of a DSP and a microprocessor. The communication module 3023 may be a transceiver, a transceiver circuit, a communication interface, or the like. The storage module 3021 may be a memory.

When the processing unit 3022 is a processor, the communication unit 3023 is a transceiver, and the storage unit 3021 is a memory, the main network device described in this embodiment of the present application may be the next third main network device.

Referring to FIG. 19, the third main network device 30 includes a processor 3032, a transceiver 3033, a memory 3031, and a bus 3034. component interconnect (PCI), extended industry standard architecture (EISA) bus, or the like. Buses can be classified into an address bus, a data bus, a control bus, and the like. For ease of presentation, in the drawing, only one thick line is used to indicate the tire, but this does not mean at all that there is only one tire or only one type of tire.

An embodiment of the present invention provides a fifth main network device to perform the above intersystem migration methods. In this embodiment of the present invention, the division of functional modules for the main network device may be based on method examples. For example, the separation of functional modules may be based on different functions, or two or more functions may be combined into one processing module. An integrated module may be implemented in hardware or may be implemented as a function of a software module. It should be noted that the division of the module in this embodiment of this application is an example, and is only a logical function of the division, and may be a different division in the actual implementation.

Fig. 20 is a possible block diagram of the main network device described in the previous embodiment when the division of functional modules is based on different functions. The fifth main network device 40 includes a receiving unit 4011, a receiving unit 4012, and a sending unit 4013. The receiving unit 4011 is configured to support the fifth main network device 40 while executing process S115 in FIG. 4B of process S212 in FIG. 6, process S410 in FIG. 9A and process S510 in FIG. 10A. The acquisition unit 4012 is configured to support the fifth main network device 40 while executing processes S114 and S115 in FIG. 4B. The sender 4013 is configured to support the fifth main network device 40 while executing process S206 in FIG. 5, processes S206 and S213 in FIG. 6 and process S306 in FIG. 7, processes S306 and S313 in FIG. 8, processes S411 and S422 in FIG. 9 and FIG. 9B and process S511 in FIG. 10A. All contents relating to the various steps described in the previous embodiments of the method can be applied to the description of the functions of the respective functional modules. Details are not described here again.

Fig. 21 is a possible block diagram of the main network device described in the previous embodiment of the invention when the blocks are integrated. The fifth main network device 40 includes a processing module 4022 and a communication module 4023. The processing module 4022 is configured to monitor and control the activities of the fifth main network device 40. For example, the processing module 4022 is configured to support the fifth main network device 40 while executing processes S114 and S115 in FIG. 4B. The communication module 4023 is configured to support communication between the main network device and another entity, such as communication between the main network device and the functional module or network entity in FIG. 1. The fifth main network device 40 may further include a storage unit 4021 configured to store program code and data of the main network device.

Processing module 4022 may be a processor or a controller. For example, the processing unit 4022 may be a Central Processing Unit (CPU), a general purpose processor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field programmable gate array (field programmable gate array, FPGA) or other programmable logic device, logic device transistor, hardware component, or any combination thereof. Processing module 4022 may implement or execute various examples of logical blocks, modules, and circuits described with reference to the content disclosed in this application. Alternatively, the processor may be a combination of processors that implement a computing function, such as a combination of one or more microprocessors, or a combination of a DSP and a microprocessor. The communication module 4023 may be a transceiver, a transceiver circuit, a communication interface, or the like. The storage module 4021 may be a memory.

When the processing unit 4022 is a processor, the communication unit 4023 is a transceiver, and the storage unit 4021 is a memory, the main network device described in this embodiment of the present application may be the next fifth main network device.

Referring to FIG. 22, the fifth main network device 40 includes a processor 4032, a transceiver 4033, a memory 4031, and a bus 4034. The transceiver 4033, the processor 4032, and the memory 4031 are connected to each other via a bus 4034. The bus 4034 may be a peripheral component connection bus. interconnect, PCI), extended industry standard architecture (EISA) bus, or the like. Buses can be classified into an address bus, a data bus, a control bus, and the like. For ease of presentation, in the drawing, only one thick line is used to indicate the tire, but this does not mean at all that there is only one tire or only one type of tire.

All or some of the above embodiments may be implemented in software, hardware, firmware, or any combination thereof. When a program is used to implement the embodiments, some or all of the embodiments may be implemented as a computer program product. A computer program product includes one or more computer instructions. When computer program instructions are downloaded and executed on a computer, all or partial procedures or functions described in embodiments of the present invention are generated. The computer may be a general purpose computer, a dedicated computer, a computer network, or other programmable device. The computer instruction may be stored in a computer-readable storage medium or may be transferred from a computer-readable storage medium to another computer-readable storage medium. For example, a computer instruction may be transmitted from a website, computer, server, or data center to another site, another computer, another server, or another data center over a wired connection (such as coaxial cable, optical fiber, or digital subscriber line (DSL)). Digital Subscriber Line, DSL)) or wireless communication (such as infrared, radio, or microwave). A computer-readable storage medium can be any useful medium available to a computer or storage device, such as a server or data center, including one or more usable storage media. The storage medium may be a magnetic medium (eg floppy disk, hard disk or magnetic tape), an optical medium (eg a DVD), a semiconductor medium (eg a Solid State Disk (SSD)) or the like.

The above descriptions are only specific implementations of the present invention, but are not intended to limit the protection scope of the present invention. It will be appreciated by those skilled in the art that changes can be made within the technical scope disclosed in this application, which should be within the protection scope of the present invention. Thus, the protection scope of the present invention is determined by the protection scope of the claims.

Claims (67)

1. A method for intersystem movement, comprising: receiving, by a user equipment (UE), indication information during a first session establishment process, in which the indication information is used to indicate that the first session can be transferred from the first communication system to the second communication system; determining by the UE whether there is a first session in a session established in the first communication system in which the first session can be transferred from the first communication system to the second communication system; And sending, by the UE, a first message to the first primary network device of the second communication system, code UE determines that there is no first session, and in which the first message is used to perform the initial attachment to the second communication system. 2. The method of claim 1, wherein the method further comprises: sending, by the UE, a second message to the first primary network device of the second communication system when the UE determines that the first session exists, in which the second message is used to perform a tracking area update in the second communication system. 3. The method of claim 1, wherein the indication information includes one or a combination of the following information: a parameter relating to a session in the second communication system corresponding to the first session; a session persistence and first session service mode, in which, when the session persistence and first session service mode is the specified mode, the UE determines that it is possible to transfer the first session from the first communication system to the second communication system; the IP address of the first session, in which when the IP address belongs to the specified segment address, the UE determines that it is possible to transfer the first session from the first communication system to the second communication system; a network segment corresponding to the first session, in which, when the network segment has a corresponding service in the second communication system, the UE determines that it is possible to transfer the first session from the first communication system to the second communication system; And a data network name corresponding to the first session, in which, when there is an access point name corresponding to the data network name, the UE determines that it is possible to transfer the first session from the first communication system to the second communication system. 4. The method of claim 3, wherein the parameter includes one or more of: a Quality of Service (QoS) parameter or an EPS bearer ID (EBI). 5. The method according to any one of paragraphs. 1-4, wherein the receipt by the UE of the indication information during the first session establishment process comprises: sending, by the UE, a PDU session establishment request message to the second primary network device of the first communication system to establish a first session; And receiving, by the UE, a session establishment permission message PDU from the second main network device, in which the session establishment permission message PDU includes indication information. 6. The method according to any one of paragraphs. 1-5, in which that the transfer of the first session from the first communication system to the second communication system is possible, contains: the third primary network device serving the first session is a primary network device shared by the first communication system and the second communication system, in which the third primary network device provides a control plane service for the first session; or the third primary network device and the fourth primary network device that serve the first session are the primary network devices shared by the first communication system and the second communication system, in which the third primary network device provides the control plane service for the first session and the fourth primary network device provides the service user plane for the first session. 7. The method according to any one of paragraphs. 1-6, in which the first communication system is a 5G communication system, the second communication system is a 4G communication system. 8. The method according to any one of paragraphs. 1-7, in which there is an interface between the main network device of the first communication system and the main network device of the second communication system. 9. A user equipment (UE) comprising a processor and a memory, wherein the memory is configured to store instructions executable by the computer, and the processor is configured to execute instructions executable by the computer to cause the UE to perform the intersystem roaming method of any one of claims. 1-8. 10. The method of intersystem movement performed by the user device (UE), comprising: receiving at least one of the quality of service (QoS) parameter of the second communication system or the channel identifier of the second communication system during the session establishment process of a protocol data unit (PDU) in the first communication system, in which at least one of the QoS parameters of the second communication system or the channel identifier of the second communication system corresponds to the PDU session; determining, based on at least one of the QoS parameter of the second communication system or the channel ID of the second communication system, that it is possible to transfer the PDU session from the first communication system to the second communication system; And executing in response to determining an update of the tracking area in the second communication system. 11. The method of claim 10, further comprising: determining that there is no session PDU that can be transferred from the first communication system to the second communication system; And performing, in response to determining that there is no session that can be transferred from the first communication system to the second communication system, initial joining to the second communication system. 12. The method of claim 10, wherein receiving at least one of the QoS parameter of the second communication system or the channel identifier of the second communication system during the session establishment process of the PDU in the first communication system comprises: sending a PDU session request message to the primary network device of the first communication system to establish the PDU session; And receiving a PDU Session Grant message from the host network device, wherein the PDU Session Grant message contains at least one of a QoS parameter of the second communication system or a channel identifier of the second communication system. 13. The method of claim 11, wherein performing, in response to determining that there is no session PDU that can be transferred from the first communication system to the second communication system, of initially attaching to the second communication system comprises performing, in response to determining that there is no session PDU that can be transferred from the first communication system to the second communication system, and the UE or the second communication system does not support attaching to the second communication system without a data communication protocol (PDN) connection initial connection to a second communication system. 14. The method according to p. 10, further comprising communicating via a PDN connection with a second communication system, in which the PDN connection corresponds to a PDU session, and in which the PDU session and the PDN connection have the same Internet Protocol (IP) address. 15. The method of claim 10, wherein the first communication system is a fifth generation (5G) communication system and the second communication system is a fourth generation (4G) communication system. 16. The method of claim 14, wherein the session PDU and the PDN connection have the same session control device and the same user plane device. 17. User device (UE), containing: at least one processor; And a memory coupled to at least one processor, the memory containing instructions that, when executed by the at least one processor, cause the UE to: receive at least one of a quality of service (QoS) parameter of the second communication system or a channel identifier of the second communication system during the session establishment process of a protocol data unit (PDU) in the first communication system, in which at least one of the QoS parameters of the second communication system or the channel identifier of the second communication system corresponds to the PDU session; determine, based on at least one of the QoS parameter of the second communication system or the channel ID of the second communication system, that it is possible to transfer the PDU session from the first communication system to the second communication system; And perform, in response to the determination, updating the tracking area in the second communication system. 18. The UE of claim 17, wherein the memory further comprises instructions that, when executed by the at least one processor, cause the UE to: determine that there is no session PDU that can be transferred from the first communication system to the second communication system; And perform, in response to determining that there is no session PDU that can be transferred from the first communication system to the second communication system, of initial joining to the second communication system. 19. The UE of claim 17, wherein receiving at least one of the QoS parameter of the second communication system or the channel identifier of the second communication system during the session establishment process of the PDU in the first communication system comprises: sending a PDU session request message to the primary network device of the first communication system to establish the PDU session; And receiving a PDU Session Grant message from the host network device, wherein the PDU Session Grant message contains at least one of a QoS parameter of the second communication system or a channel identifier of the second communication system. 20. The UE of claim 18, wherein performing, in response to determining that there is no session that can be transferred from the first communication system to the second communication system, initial joining to the second communication system comprises performing, in response to determining that there is no session that can be transferred from the first communication system to the second communication system, and the UE or the second communication system does not support joining to the second communication system without a data communication network (PDN) connection, initial joining to second communication system. 21. The UE of claim 17, wherein the memory further comprises instructions that, when executed by the at least one processor, cause the UE to communicate via a PDN connection with a second communication system, in which the PDN connection corresponds to a PDU session, and in which the PDU session and connection PDNs share the same Internet Protocol (IP) address. 22. The UE of claim 17, wherein the first communication system is a fifth generation (5G) communication system and the second communication system is a fourth generation (4G) communication system. 23. The UE of claim 21, wherein the session PDU and the PDN connection have the same session control device and the same user plane device. 24. User device (UE), containing: at least one processor; And a memory coupled to at least one processor, the memory containing instructions that, when executed by the at least one processor, cause the UE to: determine that the UE has a protocol data unit (PDU) session that corresponds to at least one of the first QoS parameter of the second communication system or the first channel identifier of the second communication system, in which at least one of the first QoS parameter of the second communication system or the first identifier a channel of the second communication system is received during the session establishment process of the PDU in the first communication system; And perform, in response to the determination, updating the tracking area in the second communication system. 25. The UE of claim 24, wherein the memory further comprises instructions that, when executed by the at least one processor, cause the UE to: determine that there is no session PDU that matches at least one of the first QoS parameter of the second communication system or the first channel ID of the second communication system; And perform in response to determining that there is no session PDU that matches at least one of the first QoS parameter of the second communication system or the first channel ID of the second communication system, initial joining to the second communication system. 26. The UE of claim 24, wherein receiving at least one of the QoS parameter of the second communication system or the channel identifier of the second communication system during the session establishment process of the PDU in the first communication system comprises: sending a PDU session request message to the primary network device of the first communication system to establish the PDU session; And receiving a PDU Session Grant message from the host network device, wherein the PDU Session Grant message contains at least one of a QoS parameter of the second communication system or a first channel identifier of the second communication system. 27. The UE of claim 24, wherein the memory further comprises instructions that, when executed by the at least one processor, cause the UE to communicate via a PDN connection with a second communication system in which the PDN connection corresponds to a PDU session, and in which the PDU session and connection PDNs share the same Internet Protocol (IP) address. 28. The UE of claim 24, wherein the first communication system is a fifth generation (5G) communication system and the second communication system is a fourth generation (4G) communication system. 29. The UE of claim 27, wherein the session PDU and the PDN connection have the same session control device and the same user plane device.

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