A handover method, a communication device and a communication system

Abstract

The application provides a switching method, a communication device and a communication system. The method comprises: when a user plane network element serving a first terminal device is switched, a target user plane network element after switching sends information indicating that the user plane network element of the first terminal device is switched to a session management network element, and carries tunnel information of the target user plane network element after switching in the information, so that the session management network element can provide the tunnel information of the target user plane network element of the first terminal device after switching to a user plane network element of a second terminal device in time, and ensure correct execution of the switching.

Description

Technical Field

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

[0002] Currently, access network equipment and user plane network elements that provide services to terminal devices can be deployed on satellites. Based on this scenario, how to achieve correct handover when access network equipment and / or user plane network elements that provide services to terminal devices switch over remains to be solved. Summary of the Invention

[0003] This application provides a handover method, communication device, and communication system to achieve correct handover of access network devices and / or user plane network elements that provide services to terminal devices.

[0004] In a first aspect, embodiments of this application provide a handover method in which a handover occurs in a first terminal device. This method can be executed by a session management network element or a module (such as a chip) applied to the session management network element. The method includes: the session management network element receiving information from a target user plane network element of the first terminal device, indicating a handover of the user plane network element of the first terminal device, through a target access network device of the first terminal device. This information includes tunnel information of the target user plane network element of the first terminal device. The session management network element then sends the tunnel information of the target user plane network element of the first terminal device to a user plane network element of a second terminal device to update the user plane network element information of the first terminal device in the user plane network element of the second terminal device. The tunnel information of the target user plane network element of the first terminal device is used to send downlink data of the first terminal device to the target user plane network element of the first terminal device.

[0005] According to the above scheme, when the user plane network element providing services to the first terminal device is switched, the target user plane network element after the switch sends information to the session management network element indicating that the user plane network element of the first terminal device has been switched, and carries the tunnel information of the target user plane network element after the switch in the information. Thus, the session management network element can promptly provide the tunnel information of the target user plane network element after the switch of the first terminal device to the user plane network element of the second terminal device, ensuring the correct execution of the switch.

[0006] In one possible implementation, the session management network element sends an end-of-terminal marker indication to the user plane network element of the second terminal device, the end-of-terminal marker indication being used to instruct the source user plane network element of the first terminal device to send an end-of-terminal marker.

[0007] In one possible implementation, the second terminal device undergoes a handover, and the user plane network element of the second terminal device is the target user plane network element of the second terminal device. Before the session management network element receives information from the target user plane network element of the first terminal device indicating that the user plane network element of the first terminal device has undergone a handover through the target access network device, the session management network element receives the tunnel information of the target user plane network element of the second terminal device. The session management network element sends the tunnel information of the target user plane network element of the second terminal device to the source user plane network element of the first terminal device to update the user plane network element information of the second terminal device in the source user plane network element of the first terminal device. The session management network element receives a response message from the source user plane network element of the first terminal device rejecting the update.

[0008] In one possible implementation, after the session management network element receives information from the target user plane network element of the first terminal device indicating that the user plane network element of the first terminal device has been switched, the session management network element sends the tunnel information of the target user plane network element of the second terminal device to the target user plane network element of the first terminal device.

[0009] In one possible implementation, the second terminal device undergoes a handover, and the user plane network element of the second terminal device is the target user plane network element of the second terminal device. After the session management network element receives information from the target user plane network element of the first terminal device indicating that the user plane network element of the first terminal device has undergone a handover through the target access network device, the session management network element receives the tunnel information of the target user plane network element of the second terminal device. The session management network element then sends the tunnel information of the target user plane network element of the second terminal device to the target user plane network element of the first terminal device.

[0010] In one possible implementation, the session management network element sends an end marker indication to the target user plane network element of the first terminal device, the end marker indication being used to instruct the source user plane network element of the second terminal device to send an end marker.

[0011] In one possible implementation, the session management network element receives a session modification request from the mobility management network element, the session modification request including information instructing the user plane network element of the first terminal device to undergo handover.

[0012] In one possible implementation, the second terminal device undergoes a handover, and the user plane network element of the second terminal device is the target user plane network element of the second terminal device. Before the session management network element receives information from the target user plane network element of the first terminal device indicating that the user plane network element of the first terminal device has undergone a handover through the target access network device, the session management network element receives the tunnel information of the target user plane network element of the second terminal device. The session management network element sends the tunnel information of the target user plane network element of the second terminal device to the source user plane network element of the first terminal device.

[0013] In one possible implementation, the session management network element sends an end-of-terminal marker indication to the source user plane network element of the first terminal device. The end-of-terminal marker indication is used to instruct the source access network device to send an end-of-terminal marker to the first terminal device.

[0014] In one possible implementation, the session management network element sends an end-of-terminal flag indication to the source user plane network element of the second terminal device. The end-of-terminal flag indication is used to instruct the source access network device to send an end-of-terminal flag to the second terminal device.

[0015] In one possible implementation, after the session management network element receives information from the target user plane network element of the first terminal device indicating that the user plane network element of the first terminal device has been switched, the session management network element sends the tunnel information of the target user plane network element of the second terminal device to the target user plane network element of the first terminal device.

[0016] In one possible implementation, the session management network element receives source tunnel information of the user plane network element of the second terminal device from the target user plane network element of the first terminal device; if the tunnel information of the source user plane network element of the second terminal device from the target user plane network element of the first terminal device is different from the tunnel information of the target user plane network element of the second terminal device stored by the session management network element, the session management network element sends the tunnel information of the target user plane network element of the second terminal device to the target user plane network element of the first terminal device.

[0017] In one possible implementation, after the session management network element receives information from the target user plane network element of the first terminal device indicating a handover of the user plane network element of the first terminal device through the target access network device, the session management network element receives the tunnel information of the target user plane network element of the second terminal device; the session management network element sends the tunnel information of the target user plane network element of the second terminal device to the source user plane network element and the target user plane network element of the first terminal device.

[0018] In one possible implementation, the session management network element sends an end-of-terminal marker indication to the source user plane network element of the first terminal device. The end-of-terminal marker indication is used to instruct the source access network device to send an end-of-terminal marker to the first terminal device.

[0019] In one possible implementation, the session management network element receives a message from the mobility management network element or the target access network device indicating that the first terminal device is undergoing a handover, the message including information indicating that the user plane network element of the first terminal device is undergoing a handover.

[0020] Secondly, embodiments of this application provide a handover method in which a handover occurs in a first terminal device. This method can be executed by a user plane network element or a module (such as a chip) applied to the user plane network element. The method includes: a target user plane network element of the first terminal device receiving first tunnel information of a user plane network element of a second terminal device from a source user plane network element of the first terminal device via a target access network device of the first terminal device. The first tunnel information of the user plane network element of the second terminal device is used to send downlink data of the second terminal device to the user plane network element of the second terminal device. The target user plane network element sends the first tunnel information of the target user plane network element of the first terminal device to a session management network element via the target access network device. The first tunnel information of the target user plane network element of the first terminal device is used to send downlink data of the first terminal device to the target user plane network element of the first terminal device.

[0021] According to the above scheme, when the user plane network element providing services to the first terminal device is switched, the target user plane network element after the switch receives the user plane network element of the second terminal device and sends the first tunnel information of the target user plane network element after the switch to the session management network element. Thus, the session management network element can promptly provide the first tunnel information of the target user plane network element after the switch of the first terminal device to the user plane network element of the second terminal device, ensuring the correct execution of the switch.

[0022] In one possible implementation, the first tunnel information of the user plane network element of the second terminal device is included in the context of the session of the first terminal device. The context of the session also includes at least one of the following: the session endpoint identifier of the session management network element, the packet detection rule corresponding to the session, and the identification information of the session management network element. The session endpoint identifier of the session management network element is used to identify the session in the session management network element, and the packet detection rule corresponding to the session is used by the target user plane network element of the first terminal device to process the uplink data packets and / or downlink data packets of the first terminal device.

[0023] In one possible implementation, the session corresponds to a local area network (LAN) group. The target user plane network element receives the packet detection rules corresponding to the LAN group from the source user plane network element of the first terminal device through the target access network device. The packet detection rules corresponding to the LAN group are used by the target user plane network element to process data packets sent to other UEs in the LAN group.

[0024] In one possible implementation, the target user plane network element sends information to the session management network element through the target access network device, indicating that the user plane network element of the first terminal device is being switched. The information indicating that the user plane network element of the first terminal device is being switched includes the first tunnel information of the target user plane network element of the first terminal device.

[0025] In one possible implementation, the information regarding the handover of the user plane network element of the first terminal device further includes the session endpoint identifier of the target user plane network element of the first terminal device, which is used to identify the session in the target user plane network element of the first terminal device.

[0026] In one possible implementation, the target user plane network element is allocated first tunnel information.

[0027] In one possible implementation, the target user plane network element receives tunnel information from the target access network device; the target user plane network element sends second tunnel information to the target access network device, and the second tunnel information is used by the target access network device of the first terminal device to send uplink data of the first terminal device to the target user plane network element.

[0028] In one possible implementation, the target user plane network element receives first tunnel information of the target user plane network element of the second terminal device from the session management network element; the target user plane network element sends downlink data of the second terminal device to the target user plane network element of the second terminal device.

[0029] In one possible implementation, the target user plane network element receives an end marker indication from the session management network element; the target user plane network element sends an end marker to the source user plane network element of the second terminal device according to the end marker indication.

[0030] Thirdly, embodiments of this application provide a handover method in which a handover occurs in a first terminal device. This method can be executed by an access network device or a module (such as a chip) applied to the access network device. The method includes: a source access network device of the first terminal device sending a handover preparation request message to a source user plane network element of the first terminal device, the handover preparation request message including an identifier of the session of the first terminal device; the source access network device receiving a handover preparation response message from the source user plane network element, the handover preparation response message including tunnel information of the user plane network element of the second terminal device corresponding to the session; and the source access network device sending the tunnel information of the user plane network element of the second terminal device to a target user plane network element of the first terminal device through the target access network device.

[0031] According to the above scheme, the source user plane network element of the first terminal device before the handover provides the tunnel information of the user plane network element of the second terminal device to the target user plane network element of the first terminal device after the handover through the source access network device of the first terminal device, which can speed up the handover process and ensure the accurate execution of the handover.

[0032] In one possible implementation, the source access network device receives radio resource information allocated by the target access network device for the session from the target access network device; the source access network device then sends the radio resource information to the first terminal device.

[0033] In one possible implementation, the source access network device receives forwarding tunnel information of the target access network device corresponding to the session from the target access network device; the source access network device sends downlink data of the first terminal device to the target access network device based on the forwarding tunnel information.

[0034] Fourthly, embodiments of this application provide a handover method in which a handover occurs in a first terminal device. This method can be executed by an access network device or a module (such as a chip) applied to the access network device. The method includes: a target access network device of the first terminal device receiving tunnel information from a source user plane network element of the first terminal device via a source access network device of the first terminal device, representing a user plane network element of the second terminal device; and the target access network device sending the tunnel information of the user plane network element of the second terminal device to a target user plane network element of the first terminal device.

[0035] According to the above scheme, the source user plane network element of the first terminal device before the handover provides the tunnel information of the user plane network element of the second terminal device to the target user plane network element of the first terminal device after the handover through the source access network device of the first terminal device, which can speed up the handover process and ensure the accurate execution of the handover.

[0036] In one possible implementation, the target access network device receives information from the target user plane network element of the first terminal device indicating that the user plane network element of the first terminal device is undergoing a handover, the information including tunnel information of the target user plane network element of the first terminal device; the target access network device sends the information to the session management network element.

[0037] In one possible implementation, the information also includes a session endpoint identifier of the target user plane network element of the first terminal device, which is used to identify the session in the target user plane network element of the first terminal device.

[0038] In one possible implementation, the tunnel information of the user plane network element of the second terminal device is included in the context of the session of the first terminal device. The context of the session also includes at least one of the following: the session endpoint identifier of the session management network element, the packet detection rule corresponding to the session, and the identification information of the session management network element. The session endpoint identifier of the session management network element is used to identify the session in the session management network element, and the packet detection rule corresponding to the session is used by the target user plane network element of the first terminal device to process the uplink data packets and / or downlink data packets of the first terminal device.

[0039] In one possible implementation, the session corresponds to a local area network (LAN) group. The target access network device receives packet detection rules corresponding to the LAN group from the source user plane network element of the first terminal device. The packet detection rules corresponding to the LAN group are used by the target user plane network element of the first terminal device to process data packets sent to other UEs in the LAN group. The target access network device sends the packet detection rules corresponding to the LAN group to the target user plane network element of the first terminal device.

[0040] Fifthly, embodiments of this application provide a handover method where a handover occurs between a first terminal device and a second terminal device. This method can be executed by a session management network element or a module (such as a chip) applied to the session management network element. The method includes: the session management network element receiving information indicating a handover for the first terminal device; the session management network element receiving first tunnel information of the target user plane network element of the second terminal device from a target user plane network element of the second terminal device; the session management network element sending the first tunnel information of the target user plane network element of the second terminal device to a source user plane network element of the first terminal device to update the user plane network element information of the second terminal device in the source user plane network element of the first terminal device; the session management network element sending the first tunnel information of the target user plane network element of the second terminal device to the target user plane network element of the first terminal device; and the session management network element sending the second tunnel information of the target user plane network element of the first terminal device to a target access network device of the first terminal device.

[0041] In one possible implementation, before the session management network element receives the first tunnel information of the target user plane network element of the second terminal device from the target user plane network element of the second terminal device, the session management network element receives information indicating that the second terminal device is undergoing a handover; the session management network element sends the first tunnel information of the source user plane network element of the first terminal device to the target user plane network element of the second terminal device.

[0042] In one possible implementation, before the session management network element sends the first tunnel information of the target user plane network element of the second terminal device to the target user plane network element of the first terminal device, the session management network element sends an end marker indication to the source user plane network element of the first terminal device. The end marker indication is used to indicate that an end marker is sent to the source user plane network element of the second terminal device.

[0043] Sixthly, embodiments of this application provide a communication device, which may be a session management network element or a module (such as a chip) applied in a session management network element. The device has the function of implementing any of the implementation methods of the first or fifth aspects described above. This function can be implemented by hardware or by hardware executing corresponding software. The hardware or software includes one or more modules corresponding to the above functions.

[0044] Seventhly, embodiments of this application provide a communication device, which may be a user plane network element or a module (such as a chip) applied in a user plane network element. The device has the function of implementing any of the implementation methods of the second aspect described above. This function can be implemented in hardware or by hardware executing corresponding software. The hardware or software includes one or more modules corresponding to the above-described functions.

[0045] Eighthly, embodiments of this application provide a communication device, which may be a user plane network element or a module (such as a chip) applied in a user plane network element. The device has the function of implementing any of the implementation methods of the third or fourth aspects described above. This function can be implemented in hardware or by hardware executing corresponding software. The hardware or software includes one or more modules corresponding to the above functions.

[0046] Ninthly, embodiments of this application provide a communication device including a processor coupled to a memory, the processor being configured to invoke a program stored in the memory to execute any of the implementation methods described in the first to fifth aspects. The memory may be located within or outside the device. Furthermore, the processor may be one or more.

[0047] In a tenth aspect, embodiments of this application provide a communication device, including a processor and a memory; the memory is used to store computer instructions, and when the device is running, the processor executes the computer instructions stored in the memory to cause the device to perform any of the implementation methods in the first to fifth aspects described above.

[0048] Eleventhly, embodiments of this application provide a communication device including units or means for performing various steps of any of the implementation methods in the first to fifth aspects described above.

[0049] In a twelfth aspect, embodiments of this application provide a communication device, including a processor and an interface circuit. The processor is configured to communicate with other devices via the interface circuit and execute any of the implementation methods described in the first to fifth aspects. The processor may include one or more devices.

[0050] In a thirteenth aspect, embodiments of this application also provide a chip system, including: a processor for executing any of the implementation methods in the first to fifth aspects described above.

[0051] In a fourteenth aspect, embodiments of this application also provide a computer-readable storage medium storing instructions that, when executed on a communication device, cause any of the implementation methods in the first to fifth aspects described above to be performed.

[0052] In a fifteenth aspect, embodiments of this application also provide a computer program product, which includes a computer program or instructions that, when executed by a communication device, cause any of the implementation methods in the first to fifth aspects to be performed.

[0053] In a sixteenth aspect, an embodiment of this application provides a communication system comprising any plurality of communication devices that execute any implementation method of the first aspect, any implementation method of the second aspect, any implementation method of the third aspect, any implementation method of the fourth aspect, or any implementation method of the fifth aspect. Attached Figure Description

[0054] Figure 1(a) is a schematic diagram of a 5G network architecture based on a service-oriented architecture;

[0055] Figure 1(b) is a schematic diagram of a 5G network architecture based on a point-to-point interface;

[0056] Figure 2 This is a schematic diagram of the communication path between UEs;

[0057] Figure 3 This is a schematic diagram of the communication path between UEs;

[0058] Figure 4 This is a schematic diagram of the communication path between UEs;

[0059] Figure 5 A flowchart illustrating a switching method provided in an embodiment of this application;

[0060] Figure 6 A flowchart illustrating a switching method provided in an embodiment of this application;

[0061] Figure 7(a) is a flowchart illustrating a switching method provided in an embodiment of this application;

[0062] Figure 7(b) is a flowchart illustrating a switching method provided in an embodiment of this application;

[0063] Figure 7(c) is a flowchart illustrating a switching method provided in an embodiment of this application;

[0064] Figure 7(d) is a flowchart illustrating a switching method provided in an embodiment of this application;

[0065] Figure 7(e) is a flowchart illustrating a switching method provided in an embodiment of this application;

[0066] Figure 7(f) is a flowchart illustrating a switching method provided in an embodiment of this application;

[0067] Figure 8 A flowchart illustrating a switching method provided in an embodiment of this application;

[0068] Figure 9 A flowchart illustrating a switching method provided in an embodiment of this application;

[0069] Figure 10 A flowchart illustrating a switching method provided in an embodiment of this application;

[0070] Figure 11 A flowchart illustrating a switching method provided in an embodiment of this application;

[0071] Figure 12 A flowchart illustrating a switching method provided in an embodiment of this application;

[0072] Figure 13 A flowchart illustrating a switching method provided in an embodiment of this application;

[0073] Figure 14 A flowchart illustrating a switching method provided in an embodiment of this application;

[0074] Figure 15 A schematic diagram of a communication device provided in an embodiment of this application;

[0075] Figure 16 This is a schematic diagram of a communication device provided in an embodiment of this application. Detailed Implementation

[0076] To address the challenges of wireless broadband technology and maintain the leading edge of the 3rd Generation Partnership Project (3GPP) network, the 3GPP standards group developed the Next Generation System architecture, known as the 5G network architecture. This architecture not only supports radio access technologies defined by the 3GPP standards group (such as Long Term Evolution (LTE) and 5G Radio Access Network (RAN)) to access the 5G core network (CN), but also supports access to the core network using non-3GPP access technologies through non-3GPP interworking functions (N3IWF) or next-generation packet data gateways (ngPDG).

[0077] Figure 1(a) is a schematic diagram of a service-based 5G network architecture. The 5G network architecture shown in Figure 1(a) may include access network equipment and core network equipment. Terminal devices access the data network (DN) through the access network equipment and core network equipment. The core network equipment includes, but is not limited to, some or all of the following network elements: authentication server function (AUSF) network element (not shown in the figure), unified data management (UDM) network element, unified data repository (UDR) network element, network repository function (NRF) network element (not shown in the figure), network exposure function (NEF) network element (not shown in the figure), application function (AF) network element, policy control function (PCF) network element, access and mobility management function (AMF) network element, session management function (SMF) network element, user plane function (UPF) network element, and binding support function (BSF) network element (not shown in the figure).

[0078] Terminal devices can be user equipment (UE), mobile stations, mobile terminal devices, etc. They can be widely used in various scenarios, such as device-to-device (D2D), vehicle-to-everything (V2X) communication, machine-type communication (MTC), the Internet of Things (IoT), virtual reality, augmented reality, industrial control, autonomous driving, telemedicine, smart grids, smart furniture, smart offices, smart wearables, smart transportation, smart cities, etc. Terminal devices can include mobile phones, tablets, computers with wireless transceiver capabilities, wearable devices, vehicles, urban air mobility vehicles (such as drones, helicopters, etc.), ships, robots, robotic arms, smart home devices, etc.

[0079] Access network equipment can be either Radio Access Network (RAN) equipment or Wired Access Network (FAN) equipment. RAN equipment includes 3GPP access network equipment, untrusted non-3GPP access network equipment, and trusted non-3GPP access network equipment. 3GPP access network equipment includes, but is not limited to: evolved NodeBs (eNodeBs) in LTE, next-generation NodeBs (gNBs) in 5G mobile communication systems, base stations in future mobile communication systems, or modules or units that perform some base station functions, such as central units (CUs) and distributed units (DUs). Untrusted non-3GPP access network equipment includes, but is not limited to: untrusted non-3GPP access gateways or N3IWF devices, untrusted wireless local area network (WLAN) access points (APs), switches, and routers. Trusted non-3GPP access network equipment includes, but is not limited to: trusted non-3GPP access gateways, trusted WLAN APs, switches, and routers. Wired access network equipment includes, but is not limited to: wireline access gateway, fixed telephone network equipment, switches, and routers.

[0080] Access network equipment and terminal equipment can be fixed or mobile. They can be deployed on land, including indoors or outdoors, handheld or vehicle-mounted; they can also be deployed on water; and they can be deployed in the air on aircraft, balloons, and satellites. The embodiments of this application do not limit the application scenarios of the access network equipment and terminal equipment.

[0081] The AMF (Automatic Mobility Management) network element includes functions such as mobility management and access authentication / authorization. In addition, it is responsible for transmitting user policies between terminal devices and the PCF (Programmable Default Function) network element.

[0082] The SMF network element includes functions such as performing session management, executing control policies issued by the PCF, selecting the UPF, and allocating Internet Protocol (IP) addresses to terminal devices.

[0083] UPF network elements include functions such as user plane data forwarding, session / flow-based billing and statistics, and bandwidth limiting.

[0084] UDM network elements include functions such as managing contracted data and authorizing user access.

[0085] UDR network elements include functions for storing and retrieving data of various types, such as contract data, policy data, and application data.

[0086] NEF network elements are used to support the opening of capabilities and events.

[0087] AF (Application Provider) network elements convey application-side requests to the network side, such as QoS requirements or user state event subscriptions. AFs can be third-party functional entities or application services deployed by operators, such as IP Multimedia Subsystem (IMS) voice call services. AF network elements include those within the core network (i.e., the operator's AFs) and third-party AFs (such as an enterprise's application server).

[0088] PCF (Policy Control Function) network elements include policy control functions responsible for session and service flow-level billing, QoS bandwidth guarantee, mobility management, and terminal device policy decisions. PCF network elements include access and mobility management policy control function (AM PCF) network elements and session management policy control function (SM PCF) network elements. AM PCF network elements are used to formulate AM policies for terminal devices; AM PCF network elements can also be referred to as policy control network elements providing services to terminal devices (PCF for a UE). SM PCF network elements are used to formulate session management policies (SM policies); SM PCF network elements can also be referred to as policy control network elements providing services to sessions (PCF for a PDU session).

[0089] NRF network elements can be used to provide network element discovery functionality, providing network element information corresponding to the network element type based on requests from other network elements. NRF also provides network element management services, such as network element registration, updates, deregistration, and network element status subscription and push.

[0090] The BSF network element can provide functions such as BSF service registration / deregistration / update, NRF connection detection, session binding information creation, UE information acquisition, and session binding information query for duplicate IP addresses.

[0091] The AUSF network element is responsible for authenticating users to determine whether to allow users or devices to access the network.

[0092] A Domain Provider (DN) is a network located outside of the carrier's network. A carrier's network can connect to multiple DNs, and various services can be deployed on a DN, providing data and / or voice services to terminal devices. For example, a DN might be the private network of a smart factory. Sensors installed in the workshop can act as terminal devices, and a control server for these sensors is deployed within the DN. The control server provides services to the sensors. Sensors can communicate with the control server, receive instructions from it, and transmit the collected sensor data back to the control server accordingly. Another example is a DN serving as an internal office network for a company. Employees' mobile phones or computers can act as terminal devices, accessing information and data resources on the company's internal office network.

[0093] In Figure 1(a), Npcf, Nufr, Nudm, Naf, Namf, and Nsmf are the service interfaces provided by PCF, UDR, UDM, AF, AMF, and SMF, respectively, used to call the corresponding service operations. N1, N2, N3, N4, and N6 are interface sequence numbers, and the meanings of these interface sequence numbers are as follows:

[0094] 1) N1: The interface between the AMF and the terminal device, which can be used to transmit non-access stratum (NAS) signaling (such as QoS rules from the AMF) to the terminal device.

[0095] 2) N2: The interface between the AMF and the access network equipment, which can be used to transmit radio bearer control information from the core network side to the access network equipment.

[0096] 3) N3: The interface between the access network device and the UPF, mainly used to transmit uplink and downlink user plane data between the access network device and the UPF.

[0097] 4) N4: The interface between SMF and UPF, which can be used to transmit information between the control plane and the user plane, including the distribution of forwarding rules, QoS rules, traffic statistics rules, etc. from the control plane to the user plane, as well as the reporting of information from the user plane.

[0098] 5) N6: The interface between UPF and DN, used to transmit uplink and downlink user data streams between UPF and DN.

[0099] Figure 1(b) is a schematic diagram of a 5G network architecture based on point-to-point interfaces. The functions of the network elements are described in Figure 1(b), and will not be repeated here. The main difference between Figure 1(b) and Figure 1(a) is that the interfaces between the control plane network elements in Figure 1(a) are service-oriented interfaces, while the interfaces between the control plane network elements in Figure 1(b) are point-to-point interfaces.

[0100] In the architecture shown in Figure 1(b), the interface names and functions between the various network elements are as follows:

[0101] 1) The meanings of interfaces N1, N2, N3, N4 and N6 can be found in the previous description.

[0102] 2) N5: The interface between the AF network element and the PCF network element, which can be used for application service request distribution and network event reporting.

[0103] 3) N7: The interface between PCF network elements and SMF network elements, which can be used to issue protocol data unit (PDU) session granularity and service data flow granularity control strategies.

[0104] 4) N8: The interface between the AMF network element and the UDM network element. It can be used by the AMF network element to obtain access and mobility management related subscription data and authentication data from the UDM network element, as well as by the AMF network element to register terminal device mobility management related information with the UDM network element.

[0105] 5) N9: User plane interface between UPF network elements, used to transmit uplink and downlink user data streams between UPF network elements.

[0106] 6) N10: The interface between SMF network elements and UDM network elements. It can be used for SMF network elements to obtain session management-related subscription data from UDM network elements, and for SMF network elements to register terminal device session-related information with UDM network elements.

[0107] 7) N11: The interface between SMF network elements and AMF network elements. It can be used to transmit PDU session tunnel information between access network devices and UPF, transmit control messages sent to terminal devices, and transmit radio resource control information sent to access network devices.

[0108] 8) N15: The interface between PCF network elements and AMF network elements, which can be used to issue terminal equipment policies and access control related policies.

[0109] 9) N35: The interface between UDM network elements and UDR network elements, which can be used by UDM network elements to obtain user subscription data information from UDR network elements.

[0110] 10) N36: The interface between PCF network elements and UDR network elements, which can be used by PCF network elements to obtain policy-related contract data and application data related information from UDR network elements.

[0111] It is understood that the aforementioned network element or function can be a network component in a hardware device, a software function running on dedicated hardware, or a virtualized function instantiated on a platform (e.g., a cloud platform). Optionally, the aforementioned network element or function can be implemented by one device, multiple devices working together, or a functional module within a single device; this application embodiment does not specifically limit this.

[0112] The user plane network element, mobility management network element, and session management network element in this application can be a UPF network element, an AMF network element, and a SMF network element in a 5G system, respectively, or they can be network elements in future communications such as 6G networks that have the functions of the aforementioned UPF network element, AMF network element, and SMF network element. This application does not limit them in this way. In the embodiments of this application, an example of a user plane network element, a mobility management network element, and a session management network element is used to describe the UPF network element, AMF network element, and SMF network element, respectively. Furthermore, the UPF network element, AMF network element, and SMF network element are abbreviated as UPF, AMF, and SMF, respectively.

[0113] For ease of explanation, in this embodiment, a base station (such as a 4G eNB, a 5G gNB, or a base station in future communications) is used as an example of an access network device. The term "base station" can be replaced with "access network device" in subsequent embodiments. Similarly, in this embodiment, a UE is used as an example of a terminal device. The term "UE" can be replaced with "terminal device" in subsequent embodiments.

[0114] In this embodiment, the Nx tunnel information or the first tunnel information of the UPF refers to the tunnel information used by other UPFs to send data to this UPF. For example, UPF2 can send data to UPF1 based on the Nx tunnel information of UPF1. In this embodiment, the Nx tunnel information of the UPF can also be called the tunnel information of the UPF, or it can have other names, such as the N19 tunnel information of the UPF in a 5G local area network (LAN), and there is no limitation on this.

[0115] In this embodiment, the N3 tunnel information or the second tunnel information of the UPF refers to the tunnel information used by the base station to send data to the UPF. For example, the base station can send data to UPF1 based on the N3 tunnel information of UPF1. In this embodiment, the N3 tunnel information of the UPF can also be called the tunnel information of the UPF, or have other names, and there is no limitation on this.

[0116] In this embodiment, the N3 tunnel information or tunnel information of the base station refers to the tunnel information used by the UPF to send data to the base station. For example, the UPF can send data to base station 1 based on the N3 tunnel information of base station 1. In this embodiment, the N3 tunnel information of the base station can also be called the tunnel information of the base station, or have other names, and there is no limitation on this.

[0117] 3GPP Release 17 proposes deploying base stations on satellites. Under the existing architecture, only the base stations are deployed on satellites; the session anchor point (UPF) remains deployed on the ground. (Reference) Figure 2 This diagram illustrates the communication path between UEs. The communication path between UE1 and UE2 is as follows: UE1 -> UE1's satellite base station 1 -> UE1's ground UPF1 -> UE2's ground UPF2 -> UE2's satellite base station 2 -> UE2. This path includes four segments of space-to-ground communication (also known as satellite-to-ground communication): 1) UE1 -> UE1's satellite base station 1; 2) UE1's satellite base station 1 -> UE1's ground UPF1; 3) UE2's ground UPF2 -> UE2's satellite base station 2; 4) UE2's satellite base station 2 -> UE2. The path between the satellite base station and the ground UPF includes the power supply circuit between the satellite and the ground station, as well as the ground link between the ground station and the UPF. The communication between the UE and the satellite base station uses a 4G air interface, a 5G air interface, or an air interface used in future communications.

[0118] Because satellites are deployed far from the ground, communication between UEs would experience significant latency if traversed through four satellite-to-ground links. To reduce this latency, a UPF (User-Defined Component Provider) can be deployed on the satellite. This allows UE-to-UE communication to bypass the ground-based UPF and directly relay messages through satellite links, thereby reducing the latency of the two power supply circuits. (Reference) Figure 3 This diagram illustrates the communication path between UEs. The communication path between UE1 and UE2 is: UE1 -> UE1's satellite base station 1 -> UE1's satellite UPF1 -> UE2's satellite UPF2 -> UE2's satellite base station 2 -> UE2. This path includes two segments of satellite-to-ground communication: 1) UE1 -> UE1's satellite base station 1; 2) UE2's satellite base station 2 -> UE2.

[0119] After the UPF is deployed to a satellite, to reduce the complexity of inter-satellite routing, an Nx tunnel can be established between the satellite UPFs of UE1 and UE2 for direct communication between them. This tunnel is used to forward data between the satellites of UE1 and UE2, so the UE's IP address is not exposed on the inter-satellite link interface. The underlying routing module of the inter-satellite link only sees the IP address of the satellite UPF, not the UE's IP address. (Reference) Figure 4The diagram illustrates the communication path between UEs. It shows that an Nx interface is added between satellite UPF1 and satellite UPF2, establishing an Nx tunnel between them. For example, the Nx tunnel could be an N19 tunnel, or a GPRS Tunneling Protocol User Plane (GTP-U) tunnel. Here, GPRS refers to General Packet Radio Service.

[0120] exist Figure 4 In this configuration, to reduce latency, the satellite base station and satellite UPF serving the UE can be located on the same satellite. Therefore, UPF1 and base station 1 are on the same satellite, and UPF2 and base station 2 are on the same satellite. An Nx tunnel is established between UPF1 and UPF2 so that when UPF1 and UPF2 forward data packets for communication between UE1 and UE2, they do not need to handle routing based on the UE's IP address, reducing the complexity of inter-satellite routing. UE1's UPF1 and UE2's UPF2 can be controlled by different SMFs or they can be controlled by the same SMF. Figure 4 The diagram shows the case where UPF1 and UPF2 are controlled by different SMFs.

[0121] When base stations and UPFs are deployed on satellites, satellite handover will occur even if the UE remains stationary on the ground, because satellites orbit the Earth at fixed frequencies and move very quickly in low Earth orbit. In the above architecture, satellite handover means that both the satellite base station and the satellite UPF serving the UE change simultaneously.

[0122] refer to Figure 5 This is a flowchart illustrating a handover method provided in an embodiment of this application. In this process, the satellite of UE1 undergoes handover. Before the handover, source base station 1 and source UPF1 on satellite 1 provide services to UE1. After the handover, target base station 1 and target UPF1 on satellite 2 provide services to UE1. The satellite of UE2 does not undergo handover; services for UE2 are provided by base station 2 and UPF2 on satellite 3. This process includes the following steps:

[0123] Step 501: Source base station 1 sends a handover request message to target base station 1. Accordingly, target base station 1 receives the handover request message.

[0124] The handover request message includes N3 tunnel information of the source UPF1 in order to establish an uplink tunnel from the target base station 1 to the source UPF1, that is, the target base station 1 can send the uplink data received from UE1 to the source UPF1.

[0125] Step 502: Target base station 1 sends a handover response message to source base station 1. Correspondingly, source base station 1 receives the handover response message.

[0126] The handover response message includes radio resource information allocated by target base station 1 to UE1.

[0127] Through steps 501 and 502 above, a forwarding tunnel between source base station 1 and target base station 1 is also established.

[0128] Step 503: Source base station 1 sends an RRC reconfiguration message to UE1. Correspondingly, UE1 receives the RRC reconfiguration message.

[0129] The RRC reconfiguration message includes radio resource information allocated by target base station 1 to UE1.

[0130] Source base station 1 can stop sending downlink data to UE1 and start sending the received downlink data that needs to be sent to UE1 to target base station 1 through the forwarding tunnel between source base station 1 and target base station 1.

[0131] Step 504: UE1 synchronizes with target base station 1.

[0132] UE1 performs wireless synchronization with target base station 1 based on the radio resource information allocated to UE1.

[0133] Step 505: UE1 sends an RRC reconfiguration complete message to target base station 1. Accordingly, target base station 1 receives the RRC reconfiguration complete message.

[0134] Following step 505, in the uplink direction, UE1 can send uplink data to target base station 1. Target base station 1 sends the uplink data received from UE1 to source UPF1, and then source UPF1 sends UE1's uplink data to UPF2 based on the Nx tunnel information of UPF2. In the downlink direction, UPF2 sends UE1's downlink data to source UPF1, source UPF1 sends UE1's downlink data to source base station 1, and source base station 1 then sends UE1's downlink data to target base station 1 through the forwarding tunnel between source base station 1 and target base station 1. Finally, target base station 1 sends UE1's downlink data back to UE1.

[0135] Step 506: Target base station 1 sends a path switch request message to the AMF. Correspondingly, the AMF receives the path switch request message.

[0136] The path switching request message includes N3 tunnel information for target base station 1.

[0137] Step 507: The AMF sends a session modification request message to the SMF. Correspondingly, the SMF receives the session modification request message.

[0138] The session modification request message includes the N3 tunnel information of the target base station 1. The session modification request message is used to notify the SMF that UE1 has undergone a handover.

[0139] Optionally, the session modification request message can be the Nsmf_PDUSession_SMContextUpdate Request message.

[0140] In step 508a, the SMF selects a target UPF1 deployed on the same satellite as the target base station 1 as the new UPF for UE1, and sends an N4 session modification request message to the target UPF1. Correspondingly, the target UPF1 receives the N4 session modification request message.

[0141] The N4 session modification message includes the N3 tunnel information of target base station 1 and the Nx tunnel information of UPF2.

[0142] In step 508b, the target UPF1 sends an N4 session modification response message to the SMF. Correspondingly, the SMF receives the N4 session modification response message.

[0143] The N4 session modification response message includes the N3 tunnel information and the Nx tunnel information of the target UPF1.

[0144] Step 509: The SMF sends a session modification response message to the AMF. The AMF then receives this session modification response message.

[0145] The session modified response message includes N3 tunnel information for target UPF1.

[0146] Optionally, the session modification response message can be the Nsmf_PDUSession_SMContextUpdate Response message.

[0147] In step 510, the AMF sends a path handover response message to the target base station 1. Correspondingly, the target base station 1 receives the path handover response message.

[0148] The path switching response message includes N3 tunnel information for target UPF1.

[0149] At this time, in the uplink direction, target base station 1 directly sends the uplink data of UE1 to target UPF1, which then sends it to UPF2.

[0150] Optionally, the path switch response message can be a PATH SWITCH REQUEST ACK message.

[0151] Step 511: SMF sends an N4 session update request message to UPF2. Correspondingly, UPF2 receives the N4 session update request message.

[0152] The N4 session update request message includes an end marker indication and Nx tunnel information for the target UPF1.

[0153] The End Marker instruction is used to instruct UPF2 to send an End Marker through the source path (i.e., to source UPF1). UPF2 sends an End Marker to source UPF1 based on this instruction. Source UPF1 sends the End Marker to source base station 1, which then forwards it to target base station 1. The End Marker is the last downlink data packet of UE1 received by target base station 1 from the forwarding tunnel between target base station 1 and source base station 1. Target base station 1 temporarily buffers the downlink data of UE1 received from target UPF1 before receiving the End Marker. After receiving the End Marker, target base station 1 can send the data received from target UPF1 to UE1.

[0154] After step 511, UPF2 begins to send downlink data packets destined for UE1 to target UPF1, which then directly sends them to target base station 1.

[0155] According to the above scheme, the out-of-order problem caused by the UE receiving data through the source path (source UPF1) later than the data received through the target path (target UPF1) during the handover process can be avoided.

[0156] In the above Figure 5 In the handover process shown, since the AMF and SMF are located on the ground, steps 506, 508a, 508b, 510 and 511 are all satellite-to-ground communication. This increases satellite-to-ground communication signaling and makes the process more time-consuming. It is necessary to rely on inter-satellite forwarding to avoid packet loss, and there is inter-satellite detour, which not only increases the time-consuming process but also increases the load on the inter-satellite link.

[0157] refer to Figure 5For UE1, in the downlink direction, before step 503, UPF2 of satellite 3 sends the downlink data of UE1 to the source UPF1 of satellite 1. The source UPF1 sends the downlink data of UE1 to the source base station 1 of satellite 1. Then the source base station 1 sends the downlink data of UE1 to the target base station 1 of satellite 2. That is, UPF2 forwards the downlink data of UE1 to the target base station 1 via the source UPF1 and the source base station 1. Since the target base station 1 is not on the same satellite as the source UPF1 and the source base station 1, the downlink data has inter-satellite detours. That is, the data sent from satellite 3 to satellite 2 needs to be forwarded to satellite 2 via satellite 1. In the uplink direction, after step 505 and before step 506, UE1 sends its uplink data to the target base station 1 of satellite 2. Then, the target base station 1 sends the uplink data of UE1 to the source UPF1 of satellite 1, and then the source UPF1 sends it to the UPF2 of satellite 3. Since the source UPF1 and the target base station 1 are not on the same satellite, the uplink data also has inter-satellite routing. That is, the data sent from satellite 2 to satellite 3 needs to be forwarded to satellite 3 via satellite 1.

[0158] Therefore, the embodiments of this application will subsequently refer to the above. Figure 5 The handover process shown has been optimized to reduce signaling between satellite and ground during the handover process and to reduce data routing between satellites.

[0159] In satellite scenarios, the probability of simultaneous cross-satellite handover between the UEs at both ends of the communication is relatively high. (Reference) Figure 6 This is a flowchart illustrating a handover method provided in an embodiment of this application. In this process, the satellite of UE1 undergoes handover. Before the handover, source base station 1 and source UPF1 on satellite 1 provide services to UE1. After the handover, target base station 1 and target UPF1 on satellite 2 provide services to UE1. The satellite of UE2 also undergoes handover. Before the handover, source base station 2 and source UPF2 on satellite 3 provide services to UE2. After the handover, target base station 2 and target UPF2 on satellite 4 provide services to UE2. For a detailed description of the handover process for UE1, please refer to [link to relevant documentation]. Figure 5 .Should Figure 6 Switching process and Figure 5 The handover process differs from that of UE1 in that UE2 also undergoes handover during the handover process of UE1, and the handover process of UE2 is similar to that of UE1. Therefore, at any point during the handover process of UE1, the SMF may receive Nx tunnel information from the target UPF2 of UE2. Similarly, at any point during the handover process of UE2, the SMF may also receive Nx tunnel information from the target UPF1 of UE1.

[0160] Refer to the above Figure 6When UE1 and UE2 undergo cross-satellite handover simultaneously, packet loss or out-of-order packet issues may occur because the UPFs corresponding to UE1 and UE2 change. For example, in step 608a, the SMF sends the Nx tunnel information of UE2's source UPF2 to UE1's target UPF1. If the SMF receives UE2's target UPF2's Nx tunnel information after step 608a, UE1's target UPF1 will not be able to obtain UE2's target UPF2's Nx tunnel information, and the data from the target UPF1 will still be sent to UE2's source UPF2. In this case, if the order of sending the end marker is inappropriate, UE2's source UPF2 may still receive data packets sent by either the source UPF1 or the target UPF1 after receiving the end marker, causing these data packets arriving at the source UPF2 after the end marker to be discarded. The end marker can be understood as the last data packet sent to the source UPF2.

[0161] Therefore, the embodiments of this application will subsequently refer to the above. Figure 6 The handover process shown has been optimized to minimize packet loss or out-of-order data packets that occur when both UEs at the communication ends simultaneously perform cross-satellite handovers.

[0162] Figure 7(a) is a schematic flowchart of a handover method provided in an embodiment of this application. In this process, the satellite of UE1 undergoes handover. Before the handover, the source base station 1 and source UPF1 on satellite 1 provide services to UE1. After the handover, the target base station 1 and target UPF1 on satellite 2 provide services to UE1. The satellite of UE2 does not undergo handover, and the base station 2 and UPF2 on satellite 3 provide services to UE2.

[0163] The method includes the following steps:

[0164] Step 701a: Source base station 1 sends a handover preparation request message to source UPF1, which includes the identifier of UE1's session.

[0165] The handover preparation request message is used to instruct the source UPF1 to prepare for the inter-satellite handover of UE1. This embodiment of the application does not limit the name of the handover preparation request message; it may also have other names. Step 702a: The source UPF1 sends a handover preparation response message to the source base station 1. This handover preparation response message includes the Nx tunnel information of the UPF2 corresponding to the session.

[0166] This handover preparation response message is a response to the aforementioned handover preparation request message.

[0167] Optionally, the Nx tunnel information of the UPF2 is included in the context of the UE1 session. The context of the session also includes at least one of the following: the session endpoint identifier of the SMF, the packet detection rule corresponding to the session, and the identification information of the SMF. The session endpoint identifier of the SMF is used to identify the session in the SMF, and the packet detection rule corresponding to the session is used by the target UPF1 to process the uplink data packets and / or downlink data packets of UE1.

[0168] Optionally, when the session of UE1 corresponds to a LAN group, the handover preparation response message also includes the packet detection rules corresponding to the LAN group. The packet detection rules corresponding to the LAN group are used by the target UPF1 to process data packets sent to other UEs in the LAN group besides UE1.

[0169] Step 703a: Source base station 1 sends the Nx tunnel information of UPF2 to target base station 1.

[0170] Optionally, if the Nx tunnel information of UPF2 is contained in the context of UE1’s session, then step 703a specifically involves: source base station 1 sending the context of UE1’s session to target base station 1.

[0171] Optionally, after step 703a, the target base station 1 also sends radio resource information allocated by the target base station 1 for the session of UE1 to the source base station 1, so that the source base station 1 sends the radio resource information to UE1, thereby UE1 establishes an air interface connection with the target base station 1 according to the radio resource information, and realizes the handover of UE1 from the source base station 1 to the target base station 1.

[0172] Optionally, after step 703a, the target base station 1 also sends the forwarding tunnel information of the target base station 1 corresponding to the session of UE1 to the source base station 1, so that the source base station 1 can send the downlink data of UE1 to the target base station 1 according to the forwarding tunnel information.

[0173] Step 704a: Target base station 1 sends the Nx tunnel information of UPF2 to target UPF1.

[0174] UPF2 is the UPF corresponding to the session of UE2 communicating with UE1. The Nx tunnel information of this UPF2 is used by the target UPF1 to send downlink data of UE2 to UPF2. Here, the downlink data of UE2 refers to the data sent to UE2.

[0175] Optionally, if the Nx tunnel information of UPF2 is contained in the context of UE1’s session, then step 704a specifically involves: target base station 1 sending the context of UE1’s session to target UPF1.

[0176] Optionally, in step 704a, target base station 1 also sends its N3 tunnel information to target UPF1. The N3 tunnel information of target base station 1 is used by target UPF1 to send downlink data of UE1 to target base station 1. Here, downlink data of UE1 refers to data sent to UE1.

[0177] Step 705a: Target UPF1 sends information to target base station 1 indicating that the UPF of UE1 has been switched. This information includes the Nx tunnel information of target UPF1.

[0178] The Nx tunnel information of target UPF1 is allocated by target UPF1. The Nx tunnel information of target UPF1 is used by UPF2 to send downlink data of UE1 to target UPF1.

[0179] Optionally, the information indicating a UPF handover for UE1 may also include the session endpoint identifier of the target UPF1, which is used to identify the session within the target UPF1. The session endpoint identifier of the target UPF1 is assigned to the session by the target UPF1.

[0180] Optionally, the information indicating that the UPF of UE1 has been switched is contained in an N4 container and sent to the target base station 1. The target base station 1 is unaware of the contents of the N4 container.

[0181] Optionally, in step 705a, target UPF1 also sends its N3 tunnel information to target base station 1. The N3 tunnel information of target UPF1 is used by target base station 1 to send uplink data of UE1 to target UPF1. Here, uplink data of UE1 refers to the data sent by UE1.

[0182] Step 706a: Target base station 1 sends information to SMF indicating that UE1's UPF has been switched.

[0183] As one implementation method, the target base station 1 sends a message to the SMF or via the AMF to the SMF indicating that UE1 is in the process of handover. The message includes information indicating that the UPF of UE1 is being handed over.

[0184] When the information indicating that the UPF of UE1 has been switched is sent to the SMF in an N4 container, the SMF can be aware of the contents of the N4 container.

[0185] Step 707a: SMF sends the Nx tunnel information of target UPF1 to UPF2 to update the UPF information of UE1 in UPF2.

[0186] If UPF2 does not store the Nx tunnel information of UE1's UPF, then "updating the UPF information of UE1 in UPF2" means storing the Nx tunnel information of UE1's UPF in UPF2. If UPF2 already stores the Nx tunnel information of UE1's UPF, then "updating the UPF information of UE1 in UPF2" means replacing the currently stored Nx tunnel information of UE2's UPF in UPF2 with the newly received Nx tunnel information of the target UPF1.

[0187] The Nx tunnel information of the target UPF1 is used by UPF2 to send downlink data of UE1 to the target UPF1. Here, the downlink data of UE1 refers to the data sent to UE1.

[0188] Optionally, if the SMF of UE1 is different from that of UE2, then the SMF of UE1 sends the Nx tunnel information of the target UPF1 to UPF2 through the SMF of UE2.

[0189] Optionally, after step 707a, the SMF also sends an End Marker indication to UPF2, which instructs UPF2 to send an End Marker to the source UPF1. If the SMF of UE1 is different from that of UE2, then the SMF of UE1 sends an End Marker indication to the SMF of UE2, and then the SMF of UE2 sends an End Marker indication to UPF2.

[0190] According to the above scheme, when UE1 is switched over, the source UPF sends the session context information of the source UPF (including the Nx tunnel information of UE2's UPF) to the target UPF during the preparation phase before the switchover. This avoids the SMF sending the Nx tunnel information of UE2's UPF to the target UPF, which can reduce the satellite-to-ground interaction between the SMF and the target UPF, thereby reducing data transmission latency and switchover latency.

[0191] Figure 7(b) is a schematic flowchart of a handover method provided in an embodiment of this application. This embodiment can be applied to scenarios where UE1 and UE2 simultaneously handover across satellites (e.g., due to satellite movement). In this process, UE1's satellite undergoes handover. Before the handover, source base station 1 and source UPF1 on satellite 1 provide services to UE1. After the handover, target base station 1 and target UPF1 on satellite 2 provide services to UE1. UE2's satellite also undergoes handover. Before the handover, source base station 2 and source UPF2 on satellite 3 provide services to UE2. After the handover, target base station 2 and target UPF2 on satellite 4 provide services to UE2.

[0192] The method includes the following steps:

[0193] Step 701b: Source base station 1 sends a handover preparation request message to source UPF1, which includes the identifier of UE1's session.

[0194] Step 702b: Source UPF1 sends a handover preparation response message to source base station 1. The handover preparation response message includes the Nx tunnel information of source UPF2 corresponding to the session.

[0195] Optionally, the Nx tunnel information of the source UPF2 is included in the context of the UE1 session. The context of the session also includes at least one of the following: the session endpoint identifier of the SMF, the packet detection rule corresponding to the session, and the identification information of the SMF. The session endpoint identifier of the SMF is used to identify the session in the SMF, and the packet detection rule corresponding to the session is used by the target UPF1 to process the uplink data packets and / or downlink data packets of UE1.

[0196] Optionally, when the session of UE1 corresponds to a LAN group, the handover preparation response message also includes the packet detection rules corresponding to the LAN group. The packet detection rules corresponding to the LAN group are used by the target UPF1 to process data packets sent to other UEs in the LAN group besides UE1.

[0197] Step 703b: Source base station 1 sends the Nx tunnel information of source UPF2 to target base station 1.

[0198] Optionally, if the Nx tunnel information of the source UPF2 is included in the context of the UE1 session, then step 703b specifically involves the source base station 1 sending the context of the UE1 session to the target base station 1.

[0199] Optionally, after step 703b, the target base station 1 also sends radio resource information allocated by the target base station 1 for the session of UE1 to the source base station 1, so that the source base station 1 sends the radio resource information to UE1, thereby UE1 establishes an air interface connection with the target base station 1 based on the radio resource information, and realizes the handover of UE1 from the source base station 1 to the target base station 1.

[0200] Optionally, after step 703b, the target base station 1 also sends the forwarding tunnel information of the target base station 1 corresponding to the session of UE1 to the source base station 1, so that the source base station 1 can send the downlink data of UE1 to the target base station 1 according to the forwarding tunnel information.

[0201] Step 704b: Target base station 1 sends the Nx tunnel information of source UPF2 to target UPF1.

[0202] Source UPF2 is the UPF corresponding to the session of UE2 communicating with UE1. The Nx tunnel information of this source UPF2 is used by target UPF1 to send downlink data of UE2 to source UPF2. Here, downlink data of UE2 refers to the data sent to UE2.

[0203] Optionally, if the Nx tunnel information of the source UPF2 is included in the context of the UE1 session, then step 704b specifically involves the target base station 1 sending the context of the UE1 session to the target UPF1.

[0204] Optionally, in step 704b, target base station 1 also sends its N3 tunnel information to target UPF1. The N3 tunnel information of target base station 1 is used by target UPF1 to send downlink data of UE1 to target base station 1. Here, downlink data of UE1 refers to data sent to UE1.

[0205] Step 705b: Target UPF1 sends information to target base station 1 indicating that the UPF of UE1 has been switched. This information includes the Nx tunnel information of target UPF1.

[0206] The Nx tunnel information of target UPF1 is allocated by target UPF1. The Nx tunnel information of target UPF1 is used by UE2's UPF to send UE1's downlink data to target UPF1.

[0207] Optionally, the information indicating a UPF handover for UE1 may also include the session endpoint identifier of the target UPF1, which is used to identify the session within the target UPF1. The session endpoint identifier of the target UPF1 is assigned to the session by the target UPF1.

[0208] Optionally, the information indicating that the UPF of UE1 has been switched is contained in an N4 container and sent to the target base station 1. The target base station 1 is unaware of the contents of the N4 container.

[0209] Optionally, in step 705b, target UPF1 also sends its N3 tunnel information to target base station 1. The N3 tunnel information of target UPF1 is used by target base station 1 to send uplink data of UE1 to target UPF1. Here, uplink data of UE1 refers to the data sent by UE1.

[0210] Step 706b: SMF receives Nx tunnel information from target UPF2 via target base station 2.

[0211] At this time, UE2 is also switching over, and UE2 switches over earlier than UE1. Therefore, before step 709b, SMF has already received the Nx tunnel information from target UPF2.

[0212] Step 707b: SMF sends the Nx tunnel information of target UPF2 to source UPF1 to update the UPF information of UE2 in source UPF1.

[0213] Step 708b: Source UPF1 sends a response message to SMF rejecting the update.

[0214] When the SMF receives the Nx tunnel information from the target UPF2, it is unaware that UE1 is also undergoing a handover. Therefore, the SMF sends the Nx tunnel information of the target UPF2 to the source UPF1 to update the UPF information of UE2 in the source UPF1. However, the source UPF1 is aware that UE1 is handover, so the source UPF1 refuses to update, that is, it sends a response message to the SMF to refuse to update the UPF information of UE2 in the source UPF1.

[0215] Optionally, the response message for the rejection message may carry a rejection reason value, whereby the rejection reason value is that UE1 is switching.

[0216] Step 709b: Target base station 1 sends information to SMF indicating that UE1's UPF has been switched.

[0217] When the information indicating that the UPF of UE1 has been switched is sent to the SMF in an N4 container, the SMF can be aware of the contents of the N4 container.

[0218] Optionally, step 709b specifically involves: the target base station 1 sending information to the AMF indicating that the UPF of UE1 has been switched, and then the AMF sending a session modification request to the SMF, which includes the information indicating that the UPF of UE1 has been switched.

[0219] After step 709b, the SMF learns that UE1 has completed the handover and that the UPF after the handover is the target UPF1, so it can execute the following step 710b.

[0220] Step 710b: SMF sends the Nx tunnel information of target UPF2 to target UPF1.

[0221] Optionally, since a rejection message for updating was received in step 708b, the SMF may send an End Marker instruction to the target UPF1 in or after step 710b, and the target UPF1 may send an End Marker to the source UPF2 in accordance with the End Marker instruction.

[0222] After step 709b, the SMF learns that UE1 has completed the handover and that the UPF after the handover is the target UPF1. Therefore, it can execute the following step 711b, which is independent of step 710b mentioned above.

[0223] Step 711b: SMF sends the Nx tunnel information of target UPF1 to target UPF2.

[0224] Optionally, in or after step 711b, the SMF sends an End Marker instruction to the target UPF2, and the target UPF2 sends an End Marker to the source UPF1 according to the End Marker instruction.

[0225] According to the above scheme, when UE1 and UE2 are simultaneously handover, the SMF receives the updated Nx tunnel information of the target UPF2 from UE2, and is unaware that UE1 is handovering. The SMF then sends the Nx tunnel information of the target UPF2 to the source UPF1 of UE1. After receiving the response message of the source UPF2 rejecting the update, the SMF knows that UE1 is handovering. Then, after receiving the information indicating that the UPF of UE1 is handovering, the SMF sends the updated Nx tunnel information of the target UPF2 of UE2 to the target UPF1 of UE1 after the handover, thereby ensuring the normal completion of the handover.

[0226] Figure 7(c) is a schematic flowchart of a handover method provided in an embodiment of this application. This embodiment can be applied to scenarios where UE1 and UE2 simultaneously handover across satellites (e.g., this scenario occurs due to satellite movement). In this process, UE1's satellite undergoes handover. Before the handover, source base station 1 and source UPF1 on satellite 1 provide services to UE1. After the handover, target base station 1 and target UPF1 on satellite 2 provide services to UE1. UE2's satellite also undergoes handover. Before the handover, source base station 2 and source UPF2 on satellite 3 provide services to UE2. After the handover, target base station 2 and target UPF2 on satellite 4 provide services to UE2.

[0227] The method includes the following steps:

[0228] Steps 701c to 705c are the same as steps 701b to 705b above, and can be referred to the foregoing description.

[0229] Step 706c: Target base station 1 sends information to SMF indicating that UE1's UPF has been switched.

[0230] As one implementation method, the target base station 1 sends a message to the SMF or via the AMF to the SMF indicating that UE1 is in the process of handover. The message includes information indicating that the UPF of UE1 is being handed over.

[0231] When the information indicating that the UPF of UE1 has been switched is sent to the SMF in an N4 container, the SMF can be aware of the contents of the N4 container.

[0232] Step 707c: SMF receives Nx tunnel information from target UPF2 via target base station 2.

[0233] When the SMF receives the Nx tunnel information of the target UPF2 from the target UPF2, it has already learned through the above step 706c that UE1 is also undergoing a handover, and that the UPF after the handover of UE1 is the target UPF1. Therefore, the SMF sends the Nx tunnel information of the target UPF2 to the target UPF1, that is, it executes the following step 708c.

[0234] Step 708c: SMF sends the Nx tunnel information of target UPF2 to target UPF1.

[0235] Optionally, in or after step 708c, the SMF sends an End Marker instruction to the target UPF1, and the target UPF1 sends an End Marker to the source UPF2 according to the End Marker instruction.

[0236] Optionally, after step 707c, step 709c is also performed, which is independent of step 708c.

[0237] Step 709c: SMF sends the Nx tunnel information of target UPF1 to target UPF2.

[0238] Optionally, in or after step 709c, the SMF sends an End Marker instruction to the target UPF2, and the target UPF2 sends an End Marker to the source UPF1 according to the End Marker instruction.

[0239] According to the above scheme, when UE1 and UE2 are switched at the same time, the SMF receives the updated Nx tunnel information of the target UPF2 from UE2 and has already learned the information of the target UPF1 after the switch of UE1. Then the SMF sends the Nx tunnel information of the target UPF2 to the target UPF1 of UE1, thereby ensuring the normal completion of the switch.

[0240] Figure 7(d) is a schematic flowchart of a handover method provided in an embodiment of this application. This embodiment can be applied to scenarios where UE1 and UE2 simultaneously handover across satellites (e.g., this scenario occurs due to satellite movement). In this process, UE1's satellite undergoes handover. Before the handover, source base station 1 and source UPF1 on satellite 1 provide services to UE1. After the handover, target base station 1 and target UPF1 on satellite 2 provide services to UE1. UE2's satellite also undergoes handover. Before the handover, source base station 2 and source UPF2 on satellite 3 provide services to UE2. After the handover, target base station 2 and target UPF2 on satellite 4 provide services to UE2.

[0241] The method includes the following steps:

[0242] Steps 701d to 705d are the same as steps 701b to 705b above, and can be referred to the foregoing description.

[0243] In step 706d, the SMF receives the Nx tunnel information from the target UPF2 via the target base station 2.

[0244] At this time, UE2 is also undergoing a handover, and the handover of UE2 is earlier than that of UE1. Therefore, after step 705d, SMF has received the Nx tunnel information from the target UPF2.

[0245] In step 707d, the SMF sends the Nx tunnel information of the target UPF2 to the source UPF1 to update the UPF information of UE2 in the source UPF1.

[0246] When the SMF receives the Nx tunnel information of the target UPF2 from the target UPF2, it is unaware that UE1 is also undergoing a handover. Therefore, the SMF sends the Nx tunnel information of the target UPF2 to the source UPF1 to update the UPF information of UE2 in the source UPF1.

[0247] Optionally, after step 706d, the SMF sends an End Marker instruction to the source UPF2, which instructs the source UPF2 to send an End Marker to the source base station 2. The source UPF2 then sends the End Marker to the source base station 2.

[0248] Step 708d: Target base station 1 sends information to SMF indicating that UE1's UPF has been switched.

[0249] When the information indicating that the UPF of UE1 has been switched is sent to the SMF in an N4 container, the SMF can be aware of the contents of the N4 container.

[0250] Optionally, step 708d specifically involves: the target base station 1 sending information to the AMF indicating that the UPF of UE1 has been switched, and then the AMF sending a session modification request to the SMF, which includes the information indicating that the UPF of UE1 has been switched.

[0251] In step 709d, the SMF sends the Nx tunnel information of the target UPF2 to the target UPF1.

[0252] As one implementation method, the SMF also receives the Nx tunnel information of the UE2's UPF sent by the target UPF1 via steps 705d and 708d above. Here, the target UPF1 receives the Nx tunnel information of the UE2's UPF from the source UPF1. Specifically, step 709d involves the SMF determining that if the Nx tunnel information of the UE2's UPF from the target UPF1 differs from the Nx tunnel information of the UE2's UPF stored by the SMF, then the SMF sends the Nx tunnel information of the target UPF2 to the target UPF1. For example, if the Nx tunnel information of the UE2's UPF from the target UPF1 is the Nx tunnel information of the source UPF2, and the Nx tunnel information of the UE2's UPF stored by the SMF is the Nx tunnel information of the target UPF2, then the SMF determines that the Nx tunnel information of the UE2's UPF from the target UPF1 differs from the Nx tunnel information of the UE2's UPF stored by the SMF, and thus the SMF sends the Nx tunnel information of the target UPF2 to the target UPF1.

[0253] After step 708d, the SMF learns that UE1 has completed the handover and that the UPF after the handover is the target UPF1. Therefore, it can execute the following step 710d, which is independent of step 709d mentioned above.

[0254] In step 710d, SMF sends the Nx tunnel information of target UPF1 to target UPF2.

[0255] Optionally, after step 710d, the SMF sends an End Marker instruction to the source UPF1, which instructs the source UPF1 to send an End Marker to the source base station 1. The source UPF1 then sends an End Marker to the source base station 1 according to the End Marker instruction.

[0256] According to the above scheme, when UE1 and UE2 undergo handover simultaneously, the SMF, upon receiving the updated Nx tunnel information of the target UPF2 from UE2 and unaware that UE1 is undergoing handover, sends the Nx tunnel information of the target UPF2 to the source UPF1 of UE1 to update the UPF information of UE2 in the source UPF1. The source UPF2 accepts the update and subsequently sends downlink data of UE2 to the target UPF2 instead of sending downlink data of UE2 to the source UPF2. After receiving information indicating that the UPF of UE1 has undergone handover, the SMF then sends the updated Nx tunnel information of the target UPF2 of UE2 to the target UPF1 of UE1 after the handover, thus ensuring the normal completion of the handover.

[0257] Figure 7(d) is a schematic flowchart of a handover method provided in an embodiment of this application. This embodiment can be applied to scenarios where UE1 and UE2 simultaneously handover across satellites (e.g., this scenario occurs due to satellite movement). In this process, UE1's satellite undergoes handover. Before the handover, source base station 1 and source UPF1 on satellite 1 provide services to UE1. After the handover, target base station 1 and target UPF1 on satellite 2 provide services to UE1. UE2's satellite also undergoes handover. Before the handover, source base station 2 and source UPF2 on satellite 3 provide services to UE2. After the handover, target base station 2 and target UPF2 on satellite 4 provide services to UE2.

[0258] The method includes the following steps:

[0259] Steps 701e to 705e are the same as steps 701b to 705b above, and can be referred to the foregoing description.

[0260] Step 706e: Target base station 1 sends information to SMF indicating that UE1's UPF has been switched.

[0261] As one implementation method, the target base station 1 sends a message to the SMF or via the AMF to the SMF indicating that UE1 is in the process of handover. The message includes information indicating that the UPF of UE1 is being handed over.

[0262] When the information indicating that the UPF of UE1 has been switched is sent to the SMF in an N4 container, the SMF can be aware of the contents of the N4 container.

[0263] Step 707e: SMF receives Nx tunnel information from target UPF2 via target base station 2.

[0264] When the SMF receives the Nx tunnel information from the target UPF2, it has already learned through step 706e that UE1 is also undergoing a handover, and that the UPF after the handover of UE1 is the target UPF1. Therefore, the SMF sends the Nx tunnel information of the target UPF2 to the target UPF1, that is, it executes the following step 708e. It also executes the following step 709e, and there is no sequential order constraint between steps 708e and 709e.

[0265] Step 708e: SMF sends the Nx tunnel information of target UPF2 to target UPF1.

[0266] Step 709e: SMF sends the Nx tunnel information of target UPF2 to source UPF1.

[0267] Optionally, after step 709e, the SMF sends an End Marker instruction to the source UPF2, which instructs the source UPF2 to send an End Marker to the source base station 2. The source UPF2 then sends an End Marker to the source base station 2 according to the End Marker instruction.

[0268] Optionally, after step 706e, step 710e is also performed. Step 710e is not sequential with steps 708e and 709e.

[0269] Step 710e: SMF sends the Nx tunnel information of target UPF1 to target UPF2.

[0270] Optionally, after step 710e, the SMF sends an End Marker instruction to the source UPF1, which instructs the source UPF1 to send an End Marker to the source base station 1. The source UPF1 sends an End Marker to the source base station 1 according to the End Marker instruction.

[0271] According to the above scheme, when UE1 and UE2 are switched at the same time, the SMF receives the updated Nx tunnel information of the target UPF2 from UE2 and has already learned the information of the target UPF1 after the switch of UE1. Then the SMF sends the Nx tunnel information of the target UPF2 to both the target UPF1 and the source UPF1 of UE1 to ensure the normal completion of the switch.

[0272] Figure 7(f) is a schematic flowchart of a handover method provided in an embodiment of this application. This embodiment can be applied to scenarios where UE1 and UE2 simultaneously handover across satellites (e.g., this scenario occurs due to satellite movement). In this process, UE1's satellite undergoes handover. Before the handover, source base station 1 and source UPF1 on satellite 1 provide services to UE1. After the handover, target base station 1 and target UPF1 on satellite 2 provide services to UE1. UE2's satellite also undergoes handover. Before the handover, source base station 2 and source UPF2 on satellite 3 provide services to UE2. After the handover, target base station 2 and target UPF2 on satellite 4 provide services to UE2.

[0273] The method includes the following steps:

[0274] Step 701f: SMF receives Nx tunneling information from target UPF2.

[0275] The target UPF2 can be the target UPF selected by SMF for UE2 after the handover.

[0276] Specifically, SMF can receive Nx tunneling information from target UPF2.

[0277] Optionally, before step 701f, the SMF receives information indicating that UE2 has undergone a handover, and then the SMF sends the Nx tunnel information of the source UPF1 to the target UPF2.

[0278] Step 702f: The SMF receives information indicating that UE1 has undergone a handover.

[0279] Based on the information indicating that UE1 is undergoing a handover, SMF determines that UE1 is undergoing a handover.

[0280] Optionally, the information indicating that UE1 is switching may be information for selecting a UPF for UE1, or identification information of the target UPF1.

[0281] Optionally, the information indicating that UE1 has undergone a handover can be included in a session modification request message and sent to the SMF. The SMF obtains the information indicating that UE1 has undergone a handover from the session modification request message.

[0282] It should be noted that there is no specific execution order between steps 701f and 702f.

[0283] Step 703f: SMF sends the Nx tunnel information of target UPF2 to source UPF1 to update the UPF information of UE2 in source UPF1.

[0284] When the SMF receives the Nx tunnel information of the target UPF2 of UE2, and UE1 is also undergoing a handover and the handover has not yet been completed, the SMF first sends the Nx tunnel information of the target UPF2 of UE2 to the source UPF1 of UE1 to update the UPF information of UE2 in the source UPF1 of UE1.

[0285] Optionally, at the same time as or after step 703f, the SMF also sends an end marker indication to the source UPF1, which instructs the source UPF1 to send an end marker to the source UPF2.

[0286] Step 704f: SMF sends the Nx tunnel information of target UPF2 to target UPF1.

[0287] Optionally, after step 702f, the SMF can send the N3 tunnel information of the target UPF1 to the target base station 1. Thus, the target base station 1 can send data to the target UPF1 based on the N3 tunnel information of the target UPF1.

[0288] According to the above scheme, when UE2 completes the handover and the SMF receives the Nx tunnel information of the target UPF after the handover from UE2, if UE1 is also undergoing a handover at this time, and UE1's handover is not yet complete, the SMF first sends the Nx tunnel information of UE2's target UPF2 to UE1's source UPF1, so that source UPF1 can start sending data to target UPF2. On the one hand, this ensures a normal handover; on the other hand, by decoupling the update of the UPF's Nx tunnel information from the handover of the UE's UPF, it avoids data packet loss or out-of-order delivery caused by the simultaneous updating of the UPF's Nx tunnel information and the handover of the UE's UPF.

[0289] refer to Figure 8 This is a schematic flowchart illustrating a handover method provided in an embodiment of this application. In this process, the satellite of UE1 undergoes handover. Before the handover, source base station 1 and source UPF1 on satellite 1 provide services to UE1. After the handover, target base station 1 and target UPF1 on satellite 2 provide services to UE1. The satellite of UE2 does not undergo handover; services for UE2 are provided by base station 2 and UPF2 on satellite 3. Figure 8 The embodiments described above are examples of the above. Figure 5 An improvement to the embodiment. Figure 8 The corresponding embodiment is also a specific implementation of the embodiment shown in Figure 7(a) above.

[0290] The process includes the following steps:

[0291] In step 801, UE1 is about to move out of the coverage area of ​​source base station 1. Source base station 1 decides to hand over UE1 to target base station 1, and sends a handover preparation request message to source UPF1. Accordingly, source UPF1 receives the handover preparation request message.

[0292] This handover preparation request message is used to instruct source UPF1 to prepare for cross-satellite handover of UE1.

[0293] If UE1 establishes a PDU session, this step 801 is executed once, and the handover preparation request message includes the identifier of the PDU session.

[0294] If UE1 has established multiple PDU sessions, step 801 can be performed once or multiple times. That is, source base station 1 can send a handover preparation request message to source UPF1 for each PDU session, and the handover preparation request message includes an identifier of a PDU session. Alternatively, source base station 1 can send a handover preparation request message for multiple PDU sessions of the UE, and the handover preparation request message includes the identifiers of the multiple PDU sessions of the UE1. In other words, the handover preparation request message can be at the UE level or at the PDU session level.

[0295] Step 802: Source UPF1 sends a handover preparation response message to source base station 1. Correspondingly, source base station 1 receives the handover preparation response message.

[0296] The handover preparation response message includes the context information of UE1's PDU session in the source UPF1.

[0297] Specifically, if source base station 1 sends a handover preparation request message for each PDU session, then source UPF1 sends a handover preparation response message for each handover preparation request message. This handover preparation response message includes the context information of a PDU session. For example, if source base station 1 sends handover preparation request message 1 to source UPF1, which includes the identifier of PDU session 1, and also sends handover preparation request message 2 to source UPF1, which includes the identifier of PDU session 2, then source UPF1 sends handover preparation response message 1 to source base station 1 in response to handover preparation request message 1, which includes the context information of PDU session 1, and also sends handover preparation response message 2 to source base station 1 in response to handover preparation request message 2, which includes the context information of PDU session 2.

[0298] If source base station 1 sends a handover preparation request message for multiple PDU sessions of UE1, then source UPF1 sends a handover preparation response message to source base station 1. This handover preparation response message includes the context information of the multiple PDU sessions of UE1. Each PDU session corresponds to the context information of one PDU session.

[0299] The context information for each PDU session includes the PDU session identifier and all corresponding Packet Detection Rules (PDRs). The PDRs include uplink PDRs and downlink PDRs. The uplink PDR determines the transmission method of received uplink data packets, and the downlink PDR determines the transmission method of received downlink data packets. The uplink PDR includes the Nx tunnel information of the UPF2, or, when the PDU session is a 5G Local Area Network (LAN) session, the uplink PDR instructs that received uplink data packets be sent to the 5G LAN internal interface. The downlink PDR includes QoS flow information corresponding to the PDU session (e.g., QoS flow identity (QFI) and QoS flow description information (used by the target UPF to determine the QFI corresponding to the downlink data packet)).

[0300] If the PDU session is a 5G LAN session, then the source interface of the downlink PDR of the PDU session is the internal interface of the 5G LAN, and the source network instance of the PDR is set to the identifier of the 5G LAN. The destination interface of the uplink PDR of the PDU session is the internal interface of the 5G LAN, and the destination network instance of the uplink PDR is set to the identifier of the 5G LAN. That is, the uplink data packets received from the PDU session are sent to the internal interface of the 5G LAN.

[0301] If the PDU session is a 5G LAN session, the handover preparation response message also includes context information for the 5G LAN session. This context information includes an uplink PDR at the 5G LAN group level, where the source interface of the uplink PDR is a 5G LAN internal interface (VN Internal), the source network instance of the uplink PDR is set to the identifier of the 5G LAN, and the PDR includes address information. This PDR is used to send data packets destined for addresses included in the PDR to UPF2 via the Nx tunnel. The 5G LAN session context information also includes a downlink PDR at the 5G LAN group level, where the destination interface of the downlink PDR is a 5G LAN internal interface (VN Internal), the destination network instance of the downlink PDR is set to the identifier of the 5G LAN, and the downlink PDR is used to indicate that data packets received from the Nx tunnel will be sent to the internal interface of the 5G LAN.

[0302] The PDR of the PDU session and the PDR at the 5G LAN group level are used for the target UPF1 to process uplink and downlink packets.

[0303] Optionally, the context information of a PDU session may also include: N4 session information, such as the F-SEID of the SMF corresponding to the PDU session and / or the Node ID of the SMF. The F-SEID of the SMF is used to uniquely identify the PDU session within the SMF; F-SEID is short for Fully Qualified Session Endpoint Identifier.

[0304] The source UPF1 can encapsulate the context information of each PDU session of UE1 into a separate context container, and the source base station 1 does not need to understand the contents of the container. The handover preparation response message includes one or more (PDU session identifier, context container corresponding to the PDU session).

[0305] Step 803: Source base station 1 sends a handover request message to target base station 1. Accordingly, target base station 1 receives the handover request message.

[0306] The handover request message includes the identifier of each PDU session and the context container corresponding to that PDU session. Alternatively, it can be understood that the handover request message includes one or more (PDU session identifier, PDU session context container). Here, (PDU session identifier, PDU session context container) represents a combination of the PDU session identifier and the context container corresponding to that PDU session. Therefore, one or more (PDU session identifier, PDU session context container) represent one or more combinations. Each combination includes the identifier of a PDU session and the context container corresponding to that PDU session. This will be described uniformly here and will not be elaborated further later.

[0307] Step 804: Target base station 1 sends a handover preparation request message to target UPF1 located on the same satellite. Accordingly, target UPF1 receives the handover preparation request message.

[0308] The handover preparation request message includes the context information of UE1's PDU session. As a specific implementation method, the handover preparation request message includes the identifier of at least one PDU session of UE1 and the context container corresponding to the PDU session.

[0309] Furthermore, the handover preparation request message also includes N3 tunnel information of the target base station 1 corresponding to at least one PDU session of UE1. This N3 tunnel is used by the target base station 1 to receive data from the PDU session. For example, if the target base station 1 determines that the received handover request message includes a context container corresponding to the PDU session, then the target base station 1 allocates N3 tunnel information for the PDU session and carries the identifier of the PDU session, the context container of the PDU session, and the N3 tunnel information of the target base station 1 corresponding to the PDU session in the handover preparation request message. Alternatively, if the source base station 1 indicates in the handover request message which PDU sessions need to create N3 tunnels to the target UPF 1 (the source base station 1 knows which PDU sessions are served by the source UPF 1), then the target base station 1 allocates N3 tunnels for these PDU sessions and carries the identifier of the PDU session, the context container of the PDU session, and the N3 tunnel information of the target base station 1 corresponding to the PDU session in the handover preparation request message. Therefore, the handover preparation request message can include one or more (PDU session identifier, context container, and target base station 1 N3 tunnel information).

[0310] Step 805: Target UPF1 sends a handover preparation response message to target base station 1. Accordingly, target base station 1 receives the handover preparation response message.

[0311] After receiving the handover preparation request message, target UPF1 saves the identifier of the PDU session, the context information of the PDU session, and the N3 tunnel information of the target base station 1 corresponding to the PDU session.

[0312] The handover preparation response message includes the N3 tunnel information of the target UPF1 corresponding to the PDU session of UE1 and the N4 container corresponding to each PDU session. As one implementation method, the format of the handover preparation response message is as follows: The handover preparation response message includes one or more (PDU session identifier, N4 container, N3 tunnel information of target UPF1).

[0313] The N3 tunnel information of target UPF1 is sent to target base station 1, and the N4 container is sent to SMF.

[0314] In this process, target UPF1 allocates N3 tunnel information for each PDU session. This N3 tunnel information is used to receive data from target base station 1 for that PDU session. The N3 tunnel information allocated to target UPF1 for each PDU session is carried in the handover preparation response message and sent to target base station 1. Since target UPF1 receives the N3 tunnel information of target base station 1 corresponding to each PDU session in step 804, and target base station 1 can receive the N3 tunnel information of target UPF1 corresponding to each PDU session in step 805, an N3 tunnel corresponding to each PDU session is established between target base station 1 and target UPF1. This N3 tunnel is used to transmit the data of that PDU session. When UE1 successfully establishes a connection with target base station 1, the uplink data sent by UE1 can be directly sent to target UPF1 through this N3 tunnel, avoiding detours through source UPF1. It should be noted that the N3 tunnel is at the PDU session granularity, that is, each PDU corresponds to one N3 tunnel.

[0315] Each PDU session contains an N4 message encapsulated within its corresponding N4 container. For example, the N4 message can also be a PFCP session modification request message, which is generated by the target UPF1 for the PDU session and is used to notify the SMF that the UPF corresponding to the PDU session has been switched. The PFCP session modification request message includes the N4 session information corresponding to the PDU session (e.g., the SMF's F-SEID and / or the SMF's Node ID, where the SMF's F-SEID is used to uniquely identify the PDU session within the SMF), the N4 interface information of the target UPF1 (e.g., the target UPF1's F-SEID and / or the target UPF1's Node ID, where the target UPF1's F-SEID is used to uniquely identify the session within the target UPF1), and the Nx tunnel information of the target UPF1 allocated by the target UPF1 for the PDU session. This Nx tunnel information of the target UPF1 will be sent to UPF2, which will then use it to send data that UE2 needs to send to UE1. Optionally, the PFCP session modification request message may also include the N3 tunnel information of the target UPF1 corresponding to the PDU session. Optionally, the PFCP session modification request message may also include the N3 tunnel information of the target base station 1 corresponding to the PDU session.

[0316] Step 806: Target base station 1 sends a handover response message to source base station 1. Correspondingly, source base station 1 receives the handover response message.

[0317] The target base station 1 obtains the N3 tunnel information of the target UPF1 corresponding to each PDU session of UE1 from the handover preparation response message in step 805 above, and saves the N3 tunnel information of the target UPF1.

[0318] Additionally, the target base station 1 also sends a handover response message to the source base station 1, which includes the identifier of the UE1's PDU session.

[0319] Furthermore, the handover response message may also include radio resource information allocated by the target base station 1 for each PDU session of UE1.

[0320] Optionally, the handover response message may also include forwarding tunnel information of target base station 1. This forwarding tunnel information is used by source base station 1 to forward data received destined for UE1 to target base station 1. Thus, data sent from UE2 to UE1 can reach target base station 1 via the forwarding tunnel of target base station 1. The path of the data sent from UE2 to UE1 is: UE2 -> Base station 2 -> UPF2 -> Source UPF1 -> Source base station 1 -> Target base station 1. Since UE1 has not yet established a connection with target base station 1, the data sent from UE2 to UE1 can be temporarily cached in target base station 1. After the connection between target base station 1 and UE1 is established, target base station 1 can send the cached data to UE1.

[0321] Step 807: Source base station 1 sends a handover command to UE1. UE1 then receives the handover command.

[0322] When the source base station 1 receives the handover response message in step 806, it triggers the source base station 1 to send a handover command to the UE1.

[0323] The switching command can be an RRC reconfiguration message.

[0324] The handover command includes radio resource information allocated by target base station 1 to each PDU session of UE1, so that UE1 can configure the air interface according to the radio resource information.

[0325] Step 808: UE1 synchronizes with target base station 1.

[0326] After UE1 synchronizes with target base station 1, UE1 can send uplink data through target base station 1. Since the N3 tunnel between target base station 1 and target UPF1 has been established during the handover preparation phase, target base station 1 can send the uplink data received from UE1 to target UPF1. Furthermore, since the context information of the PDU session obtained by target UPF1 from source UPF1 includes the Nx tunnel information of UE2's UPF2, target UPF1 can send the received uplink data from UE1 to UPF2, and UPF2 will then send it to UE2 through base station 2. That is, after step 808, the uplink path handover is complete.

[0327] Step 809: UE1 sends a handover completion indication to target base station 1. Target base station 1 receives the handover completion indication accordingly.

[0328] The switchover completion indication can be an RRC reconfiguration completion message.

[0329] After receiving the handover completion indication, target base station 1 can begin sending downlink data to UE1. For example, target base station 1 can send previously cached data that needs to be sent to UE1 to UE1, which was sent from source base station 1 to target base station 1.

[0330] Step 810: Target base station 1 sends a path switch request message to the AMF. Correspondingly, the AMF receives the path switch request message.

[0331] The path handover request message includes the identifier of UE1's PDU session and the N4 container corresponding to each PDU session, or it can be understood that the path handover request message includes one or more (PDU session identifiers and N4 containers). The N4 container is the same as the N4 container in the handover preparation request message in step 805 above.

[0332] Step 811: The AMF sends a session modification request message to the SMF. Correspondingly, the SMF receives the session modification request message.

[0333] Here, SMF refers to the SMF corresponding to the PDU session. Different PDU sessions of UE1 may correspond to the same SMF or different SMFs; this application does not limit this.

[0334] The session modification request message includes the N4 container corresponding to the PDU session. The SMF performs corresponding operations based on the N4 message in the N4 container. For example, the SMF replaces the Node ID of the UPF corresponding to the PDU session with the Node ID of the target UPF1 in the N4 message, and / or the SMF replaces the F-SEID of the UPF corresponding to the PDU session with the F-SEID of the target UPF1 in the N4 message.

[0335] Furthermore, SMF stores the Nx tunnel information and N3 tunnel information of the target UPF1 carried in the N4 container.

[0336] Optionally, the session modification request message can be an Nsmf_PDUSession_SMContextUpdateRequest message.

[0337] In step 812, SMF sends a session modification request message to UPF2. Correspondingly, UPF2 receives the session modification request message.

[0338] The session modification request message includes the Nx tunnel information of the target UPF1 corresponding to the PDU session of UE1.

[0339] The SMF obtains the Nx tunnel information of the target UPF1 corresponding to the PDU session of UE1 from the N4 container, and sends the Nx tunnel information of the target UPF1 corresponding to the PDU session of UE1 to UPF2. UPF2 then updates the Nx tunnel information of the PDU session corresponding to the target UPF1 from the Nx tunnel information of the source UPF1 corresponding to the PDU session. As a result, UPF2 will directly send the data that UE2 needs to send to UE1 to the target UPF1, without going through the source UPF1 and source base station 1.

[0340] Optionally, the session modification request message may also include an End Marker indication, which instructs UPF2 to send an End Marker through the source path (i.e., to source UPF1). UPF2 sends an End Marker through the source path according to this End Marker indication. UPF2 then begins sending data through the new path (i.e., to target UPF1). At this point, the downlink path of UE1 switches to: UE2 -> Base Station 2 -> UPF2 -> Target UPF1 -> Target Base Station 1 -> UE1. At this point, both uplink and downlink paths of UE1 have been switched.

[0341] Optionally, the session modification request message can be an N4 session modification request message, i.e., a PFCPSessionModificationRequest message.

[0342] It should be noted that if the SMF corresponding to target UPF1 is different from the SMF corresponding to UPF2, the SMF corresponding to target UPF1 will send the Nx tunnel information of target UPF1 corresponding to UE1's PDU session to the SMF corresponding to UPF2. Then, the SMF corresponding to UPF2 will send the Nx tunnel information of target UPF1 corresponding to UE1's PDU session to UPF2. Similarly, the End Marker indication is also sent from the SMF corresponding to target UPF1 to the SMF corresponding to UPF2, and then from the SMF corresponding to UPF2 to UPF2.

[0343] Step 813: The SMF sends a session modification response message to the AMF. The AMF then receives this session modification response message.

[0344] The session modification response message includes an N4 container, which contains the PFCP session modification response message. This N4 container needs to be sent to the target UPF1.

[0345] Optionally, the session modification response message can be the Nsmf_PDUSession_SMContextUpdateResponse message.

[0346] In step 814, the AMF sends a path switch response message (PATH SWITCH REQUEST ACK) to the target base station 1. The target base station 1 then receives this path switch response message.

[0347] The path switching response message includes the identifier of the successfully switched PDU session and the N4 container corresponding to the PDU session. The N4 container comes from the session modification response message in step 813 above.

[0348] In step 815, target base station 1 sends an N4 container to target UPF1. Correspondingly, target UPF1 receives the N4 container.

[0349] The N4 container includes PFCP session modification response messages.

[0350] Compared to Figure 5 In the corresponding embodiment, the Figure 8 The corresponding implementation reduces signaling interaction between satellite and ground during handover (e.g., reducing satellite-to-ground signaling by 50%), thereby reducing the load on the satellite-to-ground link and lowering handover latency. Furthermore, by sending the PDU session context information of the source UPF to the target UPF during the preparation phase, an N3 tunnel is established between the target base station and the target UPF, thus avoiding uplink data detouring through the source UPF and further reducing data transmission latency.

[0351] refer to Figure 9This is a flowchart illustrating a handover method provided in an embodiment of this application. This embodiment can be applied to scenarios where UE1 and UE2 simultaneously handover across satellites (e.g., due to satellite movement). In this process, UE1's satellite undergoes handover. Before the handover, source base station 1 and source UPF1 on satellite 1 provide services to UE1; after the handover, target base station 1 and target UPF1 on satellite 2 provide services to UE1. UE2's satellite also undergoes handover. Before the handover, source base station 2 and source UPF2 on satellite 3 provide services to UE2; after the handover, target base station 2 and target UPF2 on satellite 4 provide services to UE2. Figure 9 The embodiments described above are examples of the above. Figure 6 An improvement to the embodiment. Figure 9 The corresponding embodiment is also a specific implementation of the embodiment shown in Figure 7(b) above.

[0352] This embodiment can be used to address timing issues related to Nx tunnel switching when UE1 and UE2 move across satellites simultaneously.

[0353] The process includes the following steps:

[0354] Steps 901 to 906 are the same as steps 801 to 806 above.

[0355] Step 906a: The SMF sends the Nx tunneling information of the target UPF2 to the source UPF1. Correspondingly, the source UPF1 receives the Nx tunneling information of the target UPF2.

[0356] Before step 906a, UE2 also undergoes a handover, and SMF has already received the Nx tunnel information of the target UPF2 after the handover.

[0357] Since the SMF is unaware that UE1 is undergoing a handover, the SMF assumes that UE1 is still being served by the source UPF1. Therefore, when the SMF receives the Nx tunnel information of the target UPF2 after the handover from UE2, it sends the Nx tunnel information of the target UPF2 to the source UPF1.

[0358] Step 906a can be executed at any step after step 901 and before step 911. This embodiment uses the example of step 906a being executed after step 906 and before step 907. The reason step 906a is limited to being executed after step 901 is that after step 901, the source UPF1 can know that UE1 is switching. Therefore, when the source UPF1 receives the Nx tunnel information from the target UPF1 of the SMF, the source UPF1 can temporarily not update the Nx tunnel information of the UPF and execute the following step 906b. The reason step 906a is limited to being executed before step 911 is that after the SMF receives the session modification request message in step 911, it can know that UE1 is switching. Therefore, the SMF may not execute step 906a. In other words, before step 911, the SMF does not know that UE1 is switching, and thus the SMF will execute the aforementioned step 906a.

[0359] Optionally, in step 906a, the SMF may also send an End marker indication to the source UPF1, which is used to instruct the source UPF1 to send an End Marker through the source path (i.e. to the source UPF2).

[0360] In step 906b, the source UPF1 sends a rejection message to the SMF. The SMF then receives the rejection message.

[0361] The rejection message can carry a reason value, which is that UE1 is switching.

[0362] Since the source UPF1 refuses to update the Nx tunnel information, the source UPF1 continues to send the uplink data of UE1 to the source UPF2 of UE2. If an End Marker indication is also sent in step 906a, the source UPF1 does not send the End Marker, that is, the source UPF1 ignores the End Marker indication.

[0363] It should be noted that, since a forwarding tunnel was established between source base station 2 and target base station 2 during the handover preparation phase, source UPF1 rejected the handover of the Nx tunnel. This means that the uplink data sent by UE1 is still sent to source UPF2, and then from source UPF2 to source base station 2. Source base station 2 then sends it to target base station 2 through the forwarding tunnel, and finally, target base station 2 sends UE1's data to UE2. At this time, the uplink data sent by UE1 detours between the source satellite (i.e., satellite 3) and the target satellite (i.e., satellite 4) of UE2. Although detours exist, this avoids out-of-order data packets during concurrent handover.

[0364] Steps 907 to 911 are the same as steps 807 to 811 above.

[0365] It should be noted that the above Figure 8 The embodiment only involves one UPF of UE2, namely UPF2, and the Figure 9 In this embodiment, two UPFs are involved for UE2: source UPF2 and target UPF2. Steps 901 to 906 and steps 907 to 911 above refer to... Figure 8 The corresponding steps in the embodiments. Among them, the UPF2 involved in steps 901 to 906 and steps 907 to 911 all refer to source UPF2.

[0366] In step 912, SMF sends a session modification request message to target UPF2. Accordingly, target UPF2 receives the session modification request message.

[0367] The session modification request message includes the Nx tunnel information of the target UPF1 corresponding to the PDU session of UE1, as well as the EndMarker indication.

[0368] The SMF obtains the Nx tunnel information of the target UPF1 corresponding to the PDU session of UE1 from the N4 container, and sends the Nx tunnel information of the target UPF1 corresponding to the PDU session of UE1 to the target UPF2. As a result, the target UPF2 updates the Nx tunnel information corresponding to the PDU session from the Nx tunnel information of the source UPF1 to the Nx tunnel information of the target UPF1. Thus, the target UPF2 will directly send the data that UE2 needs to send to UE1 to the target UPF1, that is, it no longer goes through the source UPF1 and the source base station 1.

[0369] The End Marker instruction is used to instruct target UPF2 to send an End Marker through the source path (i.e., to source UPF1). Target UPF2 sends the End Marker through the source path. Target UPF2 sends the data received from UE2 that needs to be sent to UE1 to target UPF1, which then sends it to UE1. At this point, the downlink path of UE1 switches to: UE2 -> Target Base Station 2 -> Target UPF2 -> Target UPF1 -> Target Base Station 1 -> UE1. At this point, both uplink and downlink paths of UE1 are switched. Target UPF2 obtains the information from source UPF1 from source UPF2 during the handover preparation phase.

[0370] Optionally, the session modification request message can be an N4 session modification request message, i.e., a PFCPSessionModification Request message.

[0371] It should be noted that if the SMF corresponding to target UPF1 is different from the SMF corresponding to target UPF2, the SMF corresponding to target UPF1 will send the Nx tunnel information and End Marker indication of target UPF1 corresponding to UE1's PDU session to the SMF corresponding to target UPF2. Then, the SMF corresponding to target UPF2 will send the Nx tunnel information and End Marker indication of target UPF1 corresponding to UE1's PDU session to target UPF2.

[0372] Step 913: The SMF sends a session modification response message to the AMF. The AMF then receives this session modification response message.

[0373] The session modification response message includes an N4 container, which contains the PFCP session modification response message and the Nx tunnel information for the target UPF2. This N4 container needs to be sent to the target UPF1.

[0374] Optionally, the N4 container also includes an End Marker indication.

[0375] In step 914, the AMF sends a path switch response message (PATH SWITCH REQUEST ACK) to the target base station 1. The target base station 1 then receives this path switch response message.

[0376] The path switching response message includes the identifier of the successfully switched PDU session and the N4 container corresponding to the PDU session. The N4 container comes from the session modification response message in step 913 above.

[0377] In step 915, target base station 1 sends an N4 container to target UPF1. Correspondingly, target UPF1 receives the N4 container.

[0378] The N4 container includes the PFCP session modification response message and the Nx tunnel information of the target UPF2, while the target UPF1 stores the Nx tunnel information of the target UPF2.

[0379] Optionally, if the N4 container includes an End Marker instruction, then the target UPF1 sends an End Marker to the source UPF2 according to the End Marker instruction and begins sending data to the target UPF2. Here, the target UPF1 obtains the information from the source UPF2 during the handover preparation phase.

[0380] It should be noted that this embodiment is illustrated using the example of UE1 and UE2 being served by the same AMF and SMF. This embodiment is also applicable to UE1 and UE2 being served by different SMFs and / or different AMFs.

[0381] In this embodiment, when the source UPF1 discovers that the communication peer UPF of the UE undergoing handover has also handover, the source UPF1 does not update the Nx tunnel and continues to send data through the source path to avoid packet loss or out-of-order delivery due to path inconsistency with the target UPF1. In this embodiment, before the SMF notifies the target UPF1 to send the End Marker, UE1 has already switched its path to send uplink data to the target UPF1. Therefore, before the SMF sends the End Marker indication to the target UPF1, no uplink data has been sent from the source UPF1 to the source UPF2. That is, the End Marker sent by the target UPF1 is the last data packet sent to the source UPF2, and the target UPF1 subsequently sends data to the target UPF2. The End Marker is further sent by the source UPF2 to the source base station 2, and then by the source base station 2 to the target base station 2. After receiving the End Marker through the forwarding tunnel between the source base station 2 and the target base station 2, the target base station 2 will send the downlink data of UE2 received from the target UPF2 to UE2. Furthermore, the data packets received from the forwarding tunnel are sent earlier than the data packets received from the target UPF2, so they should be sent to UE2 first, thus ensuring the in-order transmission of data.

[0382] refer to Figure 10 This is a flowchart illustrating a handover method provided in an embodiment of this application. This embodiment can be applied to scenarios where UE1 and UE2 simultaneously handover across satellites due to satellite movement. In this process, UE1's satellite handover occurs. Before the handover, source base station 1 and source UPF1 on satellite 1 provide services to UE1. After the handover, target base station 1 and target UPF1 on satellite 2 provide services to UE1. UE2's satellite handover also occurs. Before the handover, source base station 2 and source UPF2 on satellite 3 provide services to UE2. After the handover, target base station 2 and target UPF2 on satellite 4 provide services to UE2. Figure 10 The embodiments described above are examples of the above. Figure 6 An improvement to the embodiment. Figure 10 The corresponding embodiment is also a specific implementation of the embodiment shown in Figure 7(c) above.

[0383] This embodiment can be used to address timing issues related to Nx tunnel switching when UE1 and UE2 move across satellites simultaneously.

[0384] The process includes the following steps:

[0385] Steps 1001 to 1009 are the same as steps 801 to 809 above.

[0386] It should be noted that the above Figure 8 The embodiment only involves one UPF of UE2, namely UPF2, and the Figure 10In this embodiment, two UPFs are involved for UE2: source UPF2 and target UPF2. Steps 1001 to 1009 above refer to... Figure 8 The corresponding steps in the embodiments. Among them, the UPF2 involved in the above steps 1001 to 1009 all refer to source UPF2.

[0387] At the same time, UE2 also underwent a cross-satellite handover, and UE2 completed operations similar to steps 1001 to 1009 above.

[0388] Step 1010: Target base station 1 sends a path switch request message to the AMF. Correspondingly, the AMF receives the path switch request message.

[0389] The path switching request message includes the identifier of UE1's PDU session and the N4 container corresponding to each PDU session, or it can be understood that the path switching request message includes one or more (PDU session identifier, N4 container).

[0390] Each PDU session contains an N4 container encapsulating an N4 message, which can be a PFCP session modification request message. This message is generated by the target UPF1 for the PDU session and is used to notify the SMF that a UPF switch has occurred for the PDU session. The PFCP session modification request message includes the N4 session information corresponding to the PDU session (e.g., the SMF's F-SEID and / or the SMF's Node ID), the N4 interface information of the target UPF1 (e.g., the target UPF1's F-SEID and / or the target UPF1's Node ID, where the target UPF1's F-SEID uniquely identifies the session within the target UPF1), and the Nx tunnel information allocated by the target UPF1 for the PDU session. This Nx tunnel information is sent to the target UPF2, which then sends data that UE2 needs to send to UE1 to the target UPF1. Optionally, the PFCP session modification request message may also include the N3 tunnel information of the target UPF1 corresponding to the PDU session. Optionally, the PFCP session modification request message may also include the N3 tunnel information of the target base station 1 corresponding to the PDU session.

[0391] Step 1011: Target base station 2 sends a path switch request message to the AMF. Correspondingly, the AMF receives the path switch request message.

[0392] The path switching request message includes the identifier of UE2's PDU session and the N4 container corresponding to each PDU session, or it can be understood that the path switching request message includes one or more (PDU session identifier, N4 container).

[0393] Each PDU session contains an N4 container encapsulating an N4 message, which can be a PFCP session modification request message. This PFCP session modification request message is generated by the target UPF2 for the PDU session and is used to notify the SMF that a UPF handover has occurred for the PDU session. The PFCP session modification request message includes the N4 session information corresponding to the PDU session (e.g., the SMF's F-SEID and / or SMF's Node ID), the N4 interface information of the target UPF2 (e.g., the target UPF2's F-SEID, the target UPF2's Node ID, etc.), and the Nx tunnel information of the target UPF2 allocated to the PDU session by the target UPF2. This Nx tunnel information of the target UPF2 will be sent to the target UPF1 for the target UPF1 to send data that UE1 needs to send to UE2. Optionally, the PFCP session modification request message may also include the N3 tunnel information of the target UPF2 corresponding to the PDU session. Optionally, the PFCP session modification request message may also include the N3 tunnel information of the target base station 2 corresponding to the PDU session.

[0394] In step 1012, the AMF sends a session modification request message to the SMF. Correspondingly, the SMF receives the session modification request message.

[0395] Here, SMF refers to the SMF corresponding to the PDU session of UE1. Different PDU sessions of UE1 may correspond to the same SMF or different SMFs; this application does not limit this.

[0396] The session modification request message includes the N4 container corresponding to the PDU session of UE1. This N4 container is the same N4 container received by the AMF in step 1010 above.

[0397] SMF performs corresponding operations based on the N4 message in the N4 container. For example, SMF replaces the NodeID of the source UPF1 of the PDU session with the NodeID of the target UPF1 in the N4 message, and / or SMF replaces the F-SEID of the UPF corresponding to the PDU session with the F-SEID of the target UPF1 in the N4 message.

[0398] Furthermore, SMF stores the Nx tunnel information and N3 tunnel information of the target UPF1.

[0399] Optionally, the session modification request message can be an Nsmf_PDUSession_SMContextUpdateRequest message.

[0400] Step 1013: The SMF sends a session modification response message to the AMF. The AMF then receives this session modification response message.

[0401] The session modification response message includes an N4 container, which contains the PFCP session modification response message. This N4 container needs to be sent to the target UPF1.

[0402] This session modification response message is a response to the session modification request message in step 1012 above. Since the SMF has not yet received the Nx tunnel information of the target UPF2 of UE2 at this time, the session modification response message does not carry the Nx tunnel information of the target UPF2.

[0403] Optionally, the session modification response message can be the Nsmf_PDUSession_SMContextUpdateResponse message.

[0404] Step 1014: The AMF sends a session modification request message to the SMF. Correspondingly, the SMF receives the session modification request message.

[0405] Here, SMF refers to the SMF corresponding to the PDU session of UE2. Different PDU sessions of UE2 may correspond to the same SMF or different SMFs; this application does not limit this.

[0406] The session modification request message includes the N4 container corresponding to UE2's PDU session. This N4 container is the same N4 container received by the AMF in step 1011 above.

[0407] SMF performs corresponding operations based on the N4 message in the N4 container. For example, SMF replaces the NodeID of the UPF corresponding to the PDU session with the NodeID of the target UPF2 in the N4 message, and / or SMF replaces the F-SEID of the UPF corresponding to the PDU session with the F-SEID of the target UPF2 in the N4 message.

[0408] Furthermore, SMF stores the Nx tunnel information and N3 tunnel information of the target UPF2.

[0409] Optionally, the session modification request message can be an Nsmf_PDUSession_SMContextUpdateRequest message.

[0410] In step 1015, the AMF sends a path switch response message (PATH SWITCH REQUEST ACK) to the target base station 1. The target base station 1 then receives this path switch response message.

[0411] The path switching response message includes the identifier of the PDU session of the successfully switched UE1 and the N4 container corresponding to the PDU session. The N4 container comes from the session modification response message in step 1013 above.

[0412] Step 1016: The SMF sends a session modification response message to the AMF. The AMF then receives this session modification response message.

[0413] The session modification response message includes an N4 container, which contains the Nx tunnel information for target UPF1 and an EndMarker indication. This N4 container needs to be sent to target UPF2. The EndMarker indication is used to instruct target UPF2 to send an EndMarker through the source path (i.e., to source UPF1) before sending data to target UPF1.

[0414] This session modification response message is a response to the session modification request message in step 1014 above. Since the SMF has already received the Nx tunnel information of the target UPF1 of UE1 at this time, the session modification response message carries the Nx tunnel information of the target UPF1.

[0415] Optionally, the session modification response message can be the Nsmf_PDUSession_SMContextUpdateResponse message.

[0416] In step 1017, the AMF sends a path switch response message (PATH SWITCH REQUEST ACK) to the target base station 2. The target base station 2 then receives this path switch response message.

[0417] The path switching response message includes the identifier of the PDU session of the successfully switched UE2 and the N4 container corresponding to the PDU session. The N4 container comes from the session modification response message in step 1016 above.

[0418] In step 1018, target base station 2 sends the N4 container to target UPF2. Correspondingly, target UPF2 receives the N4 container.

[0419] Target UPF2 sends an EndMarker via the source path (i.e., to source UPF1) according to the End Marker instruction in the N4 container. Target UPF2 then forwards the data received from UE2 that needs to be sent to UE1 to Target UPF1, which in turn forwards it to UE1. At this point, the downlink path of UE2 switches to: UE2 -> Target Base Station 2 -> Target UPF2 -> Target UPF1 -> Target Base Station 1 -> UE1. The downlink path switch for UE1 is now complete.

[0420] In step 1019, the SMF sends the Nx tunneling information and End Marker indication of target UPF2 to target UPF1. Correspondingly, target UPF1 receives the Nx tunneling information and End Marker indication from target UPF2.

[0421] This End Marker instruction is used to instruct target UPF1 to send an End Marker through the source path (i.e., to source UPF2) before sending data to target UPF2.

[0422] According to the End Marker instruction, target UPF1 sends an End Marker through the source path (i.e., to source UPF2). Subsequently, target UPF1 sends the data received from UE1 that needs to be sent to UE2 to target UPF2, which then forwards it to UE2. At this point, the uplink path of UE1 switches to: UE1 -> target base station 1 -> target UPF1 -> target UPF2 -> target base station 2 -> UE2. The uplink path switch for UE1 is now complete.

[0423] It should be noted that this embodiment is illustrated using the example of UE1 and UE2 being served by the same AMF and SMF. This embodiment is also applicable to UE1 and UE2 being served by different SMFs and / or different AMFs. In this embodiment, in step 1019, the SMF notifies the target UPF1 to switch paths and sends an End marker. After sending the End marker, the target UPF1 no longer sends any data packets to the source UPF2. After receiving the End Marker through the forwarding tunnel between the source base station 2 and the target base station 2, the target base station 2 sends the downlink data of UE2 received from the target UPF2 to UE2. Furthermore, the data packets received from the forwarding tunnel are sent earlier than the data packets received from the target UPF2, and should be sent to UE2 first, thus ensuring the in-order transmission of data.

[0424] refer to Figure 11This is a flowchart illustrating a handover method provided in an embodiment of this application. This embodiment can be applied to scenarios where UE1 and UE2 simultaneously handover across satellites due to satellite movement. In this process, UE1's satellite handover occurs. Before the handover, source base station 1 and source UPF1 on satellite 1 provide services to UE1. After the handover, target base station 1 and target UPF1 on satellite 2 provide services to UE1. UE2's satellite handover also occurs. Before the handover, source base station 2 and source UPF2 on satellite 3 provide services to UE2. After the handover, target base station 2 and target UPF2 on satellite 4 provide services to UE2. Figure 11 The embodiments described above are examples of the above. Figure 6 An improvement to the embodiment. Figure 11 The corresponding embodiment is also a specific implementation of the embodiment shown in Figure 7(d) above.

[0425] This embodiment can be used to address the data detour problem caused when UE1 and UE2 move across satellites simultaneously.

[0426] The process includes the following steps:

[0427] Steps 1101 to 1103 are the same as steps 801 to 803 above.

[0428] Step 1103a: The SMF sends the Nx tunneling information of the target UPF2 to the source UPF1. Correspondingly, the source UPF1 receives the Nx tunneling information of the target UPF2.

[0429] Before step 1103a, UE2 also undergoes a handover, and SMF has already received the Nx tunnel information of the target UPF2 after the handover.

[0430] Since the SMF is unaware that UE1 is undergoing a handover, the SMF assumes that UE1 is still being served by the source UPF1. Therefore, when the SMF receives the Nx tunnel information of the target UPF2 after the handover from UE2, it sends the Nx tunnel information of the target UPF2 to the source UPF1.

[0431] In the above Figure 9 In this embodiment, before the switching of source UPF1 is completed, source UPF1 rejects the Nx tunnel information of target UPF2, specifically referring to steps 906a and 906b above. Figure 11 In one embodiment, when the handover of the source UPF1 is not yet complete, the source UPF1 does not reject the Nx tunnel information of the target UPF2. Subsequently, the source UPF1 uses the Nx tunnel information of the target UPF2 to send the uplink data packets of UE1 to the target UPF2, instead of sending them to the source UPF2.

[0432] Furthermore, in one possible implementation, the SMF records the timestamp of sending the Nx tunnel information of the target UPF1 to the source UPF1. After receiving the response message for step 1103a, the SMF notifies the source UPF2 of UE2 to send an End Marker to the target base station 2 of UE2. That is, the End Marker received by the target base station 2 of UE2 is sent by the source UPF2, whereas in the previous implementation, the End Marker was sent by the source UPF1 or the target UPF1 of the peer UE (i.e., UE1). When the SMF confirms that UE1 is no longer sending data through the source path, it notifies the source UPF2 to send an End Marker. As long as the data packet sent by the source UPF1 to the source UPF2 is earlier than the SMF's notification to the source UPF2 to send the End Marker, out-of-order delivery will not occur. Since the SMF notifies the source UPF1 to switch paths first, it can be assumed that, under normal circumstances, the data packet sent by the source UPF1 to the source UPF2 is earlier than the SMF's notification to the source UPF2 to send the End Marker.

[0433] Step 1103a can occur at any time before step 1106a. This embodiment will be described using the example of step 1103a occurring after step 1103 and before step 1104.

[0434] Steps 1104 to 1106 are the same as steps 804 to 806 above.

[0435] Step 1106a: Target base station 1 sends a handover preparation request message to the AMF of UE1. Correspondingly, the AMF receives the handover preparation request message.

[0436] The handover preparation request message includes the identifier of target base station 1 and the N4 container corresponding to each PDU session of UE1. The N4 container encapsulates an N4 message, which can be a PFCP session modification request message. This PFCP session modification request message is generated by target UPF1 for the PDU session and is used to notify the SMF that a handover has occurred to the UPF corresponding to the PDU session. The PFCP session modification request message includes the N4 session information corresponding to the PDU session (e.g., the SMF's F-SEID and / or the SMF's Node ID), the N4 interface information of target UPF1 (e.g., the target UPF1's F-SEID and / or the target UPF1's Node ID, where the target UPF1's F-SEID is used to uniquely identify the session within the target UPF1), and the Nx tunnel information allocated by target UPF1 for the PDU session. This Nx tunnel information will be sent to target UPF2, which will then use it to send UE2's data to target UPF1. Optionally, the PFCP session modification request message may also include the N3 tunnel information of the target UPF1 corresponding to the PDU session. Optionally, the PFCP session modification request message may also include the N3 tunnel information of the target base station 1 corresponding to the PDU session.

[0437] In one possible implementation, the N4 container also includes Nx tunneling information from the source UPF2.

[0438] In step 1106b, the AMF sends a session modification request message to the SMF. Correspondingly, the SMF receives the session modification request message.

[0439] The session modification request message includes the N4 container corresponding to the PDU session and an indication message, which is used for the process to prepare for the handover.

[0440] In step 1106c, the SMF sends a session modification response message to the AMF. The AMF then receives the session modification response message.

[0441] The session modification response message includes an N4 container, which contains the PFCP session modification response message. This N4 container needs to be sent to the target UPF1.

[0442] SMF checks the timestamp of the last time the target UPF2 Nx tunnel information was sent to the source UPF1. If the difference between the timestamp and the current time is less than a predetermined threshold, it indicates that the source UPF1 has received an updated Nx tunnel message after step 1102, namely the tunnel information of the target UPF2. Therefore, the Nx tunnel information of the source UPF2 received by the target UPF1 is outdated. Thus, SMF carries the target UPF2 Nx tunnel information in the N4 container so that the target UPF1 can save the target UPF2 Nx tunnel information.

[0443] Alternatively, SMF can also avoid using timestamps to determine whether to send Nx tunnel information of target UPF2 to target UPF1. Instead, it can always carry the latest Nx tunnel information corresponding to UE2 stored locally in the N4 container. In this way, regardless of whether the target UPF1 receives the latest Nx tunnel information corresponding to UE2 from the source UPF1, the target UPF1 will always receive the latest Nx tunnel information corresponding to UE2.

[0444] Alternatively, if the N4 container sent by the target UPF1 to the SMF includes the Nx tunnel information of UE2's UPF2, the SMF determines whether the Nx tunnel information of UPF2 stored locally is the same as the Nx tunnel information of UPF2 in the N4 container. If they are different, the SMF carries the latest Nx tunnel information corresponding to UE2 in the N4 container of the session modification response message.

[0445] In step 1106d, the AMF sends a handover preparation response message to the target base station 1. Correspondingly, the target base station 1 receives the handover preparation response message.

[0446] AMF obtains the N4 container from the session modification response message and then sends a handover preparation response message to the target base station 1, which includes the N4 container.

[0447] In step 1106e, target base station 1 sends an N4 container to target UPF1. Correspondingly, target UPF1 receives the N4 container.

[0448] If the N4 container contains the latest Nx tunnel information corresponding to UE2, that is, the Nx tunnel information of the target UPF2, the target UPF1 saves the Nx tunnel information and uses the Nx tunnel information to send uplink data packets of UE1 in the future.

[0449] Steps 1107 to 1111 are the same as steps 807 to 811 above.

[0450] It should be noted that the path switching request message in step 1110 may not include the N4 container. This is because the switching preparation request message in step 1106a above already includes the N4 container, and if the target UPF1 does not have any content to be updated, the target UPF1 does not need to include the N4 container.

[0451] In step 1112, SMF sends a session modification request message to the target UPF2. The target UPF2 then receives this session modification request message.

[0452] The session modification request message includes the Nx tunnel information of the target UPF1 corresponding to the PDU session of UE1.

[0453] The SMF obtains the Nx tunnel information of the target UPF1 corresponding to the PDU session of UE1 from the N4 container, and sends the Nx tunnel information of the target UPF1 corresponding to the PDU session of UE1 to the target UPF2. As a result, the target UPF2 updates the Nx tunnel information corresponding to the PDU session from the Nx tunnel information of the source UPF1 corresponding to the PDU session to the Nx tunnel information of the target UPF1 corresponding to the PDU session. Thus, the target UPF2 will directly send the data that UE2 needs to send to UE1 to the target UPF1, that is, it no longer needs to go through the source UPF1 and the source base station 1.

[0454] Optionally, the session modification request message can be an N4 session modification request message, i.e., a PFCP SessionModification Request message.

[0455] It should be noted that if the SMF corresponding to target UPF1 is different from the SMF corresponding to target UPF2, the SMF corresponding to target UPF1 will send the Nx tunnel information of target UPF1 corresponding to UE1's PDU session to the SMF corresponding to target UPF2, and then the SMF corresponding to target UPF2 will send the Nx tunnel information of target UPF1 corresponding to UE1's PDU session to target UPF2.

[0456] Step 1113 is the same as step 813 above.

[0457] In step 1114, after confirming that the Nx tunnel information of target UPF1 has been sent to target UPF2, the SMF sends an End Marker instruction to source UPF1. Accordingly, source UPF1 receives the End Marker instruction.

[0458] The End Marker instruction is used to instruct source UPF1 to send an End Marker to source base station 1, which is then forwarded by source base station 1 to target base station 1. At this point, target base station 1 knows that no more data will be sent from source UPF1, and therefore, target base station 1 can begin processing data from target UPF1.

[0459] According to the above scheme, when UE2 undergoes a handover, the SMF promptly sends the latest Nx tunnel information corresponding to UE2 to the source UPF1. Therefore, the source UPF1 can send UE1's data to the target UPF2 based on the latest Nx tunnel information, avoiding the need to send data to the source UPF2 and then forward it through the forwarding path between the source base station 2 and the target base station 2, thus reducing data detours. Furthermore, in this scheme, the SMF notifies the UE's source UPF to send an End Marker after confirming that the UE's communication peer has switched from the source path to the target path, preventing out-of-order data packets.

[0460] refer to Figure 12 This is a flowchart illustrating a handover method provided in an embodiment of this application. This embodiment can be applied to scenarios where UE1 and UE2 simultaneously handover across satellites due to satellite movement. In this process, UE1's satellite handover occurs. Before the handover, source base station 1 and source UPF1 on satellite 1 provide services to UE1. After the handover, target base station 1 and target UPF1 on satellite 2 provide services to UE1. UE2's satellite handover also occurs. Before the handover, source base station 2 and source UPF2 on satellite 3 provide services to UE2. After the handover, target base station 2 and target UPF2 on satellite 4 provide services to UE2. Figure 12 The embodiments described above are examples of the above. Figure 6 An improvement to the embodiment. Figure 12 The corresponding embodiment is also a specific implementation of the embodiment shown in Figure 7(e) above.

[0461] This embodiment can be used to address the data detour problem caused when UE1 and UE2 move across satellites simultaneously.

[0462] The process includes the following steps:

[0463] Steps 1201 to 1206 are the same as steps 801 to 806 above.

[0464] Step 1206a is the same as step 1106a above.

[0465] Step 1206b is the same as step 1106b above.

[0466] Step 1206c is the same as step 1106c above.

[0467] In step 1206d, the AMF sends a handover preparation response message to the target base station 1. Correspondingly, the target base station 1 receives the handover preparation response message.

[0468] The switchover preparation response message includes an N4 container. This N4 container contains a PFCP session modification response message. This N4 container needs to be sent to the target UPF1.

[0469] In step 1206e, target base station 1 sends an N4 container to target UPF1. Correspondingly, target UPF1 receives the N4 container.

[0470] At this point, since the SMF has not yet received the Nx tunnel information of the target UPF2 of UE2, the N4 container in steps 1206c, 1206d and 1206e does not include the Nx tunnel information of the target UPF2.

[0471] At any time before step 1212 and after step 1206e, if the SMF receives the latest Nx tunnel information corresponding to UE2, i.e., the Nx tunnel information of the target UPF2, the SMF immediately sends the latest Nx tunnel information corresponding to UE2 to the target UPF1 and the source UPF1. For example... Figure 12 As shown in step A. In this step, the SMF can use the F-SEID of the target UPF1 in the N4 container received in step 1206b to directly send a PFCP session modification request message to the target UPF1 (that is, without going through the target base station 1), so as to notify the target UPF1 to use the Nx tunnel information of the target UPF2, that is, to send the uplink data of UE1 to the target UPF2.

[0472] Since UE1 may still be sending uplink data through source base station 1 at this time, SMF also needs to send the Nx tunnel information of target UPF2 to source UPF1. In this way, source UPF1 can also directly use the Nx tunnel information of target UPF2, that is, send UE1's uplink data to target UPF2.

[0473] Steps 1207 to 1209 are the same as steps 807 to 809 above.

[0474] In step 1210, after confirming that both the source UPF1 and the target UPF1 have updated the Nx tunnel information of the target UPF2, the SMF sends an End Marker instruction to the source UPF2. Correspondingly, the source UPF2 receives the End Marker instruction.

[0475] The End Marker instruction is used to instruct source UPF2 to send an End Marker to source base station 2. Source UPF2 sends an End Marker to source base station 2, and the End Marker is forwarded by source base station 2 to target base station 2. At this time, target base station 2 knows that no more data will be sent from source UPF2 to target base station 2. Therefore, target base station 2 can start processing the data sent by UPF1 (source UPF1 or target UPF1).

[0476] Steps 1211 to 1215 are the same as steps 1110 to 1114 above.

[0477] According to the above scheme, when UE2 is switched over, SMF promptly sends the latest Nx tunnel information corresponding to UE2 to source UPF1. Therefore, source UPF1 can send UE1's data to target UPF2 based on the latest Nx tunnel information, avoiding the need to send the data to source UPF2 and then forward it through the forwarding path between source base station 2 and target base station 2, thus reducing data detours.

[0478] refer to Figure 13 This is a flowchart illustrating a handover method provided in an embodiment of this application. This embodiment can be applied to scenarios where UE1 and UE2 simultaneously handover across satellites due to satellite movement. In this process, UE1's satellite handover occurs. Before the handover, source base station 1 and source UPF1 on satellite 1 provide services to UE1. After the handover, target base station 1 and target UPF1 on satellite 2 provide services to UE1. UE2's satellite handover also occurs. Before the handover, source base station 2 and source UPF2 on satellite 3 provide services to UE2. After the handover, target base station 2 and target UPF2 on satellite 4 provide services to UE2. Figure 13 The embodiments described above are examples of the above. Figure 6 An improvement to the embodiments.

[0479] This embodiment can be used to address the data detour problem caused when UE1 and UE2 move across satellites simultaneously.

[0480] The process includes the following steps:

[0481] Steps 1301 to 1306 are the same as steps 801 to 806 above.

[0482] Step 1306a is the same as step 1206a above.

[0483] Step 1306b is the same as step 1206b above.

[0484] Step 1306c is the same as step 1206c above.

[0485] Step 1306d is the same as step 1206d above.

[0486] Step 1306e is the same as step 1206e above.

[0487] At this point, since the SMF has not yet received the Nx tunnel information of the target UPF2 of UE2, the N4 container in steps 1306c, 1306d and 1306e does not include the Nx tunnel information of the target UPF2.

[0488] Steps 1307 to 1309 are the same as steps 807 to 809 above.

[0489] Step 1310: Target base station 1 sends a path switch request message to the AMF. Correspondingly, the AMF receives the path switch request message.

[0490] The path switching request message includes the identifier of UE1's PDU session.

[0491] In step 1311, UE2 also undergoes a handover, and the target base station 2 of UE2 sends a path switch request message (PATHSWITCH REQUEST) to the AMF. Correspondingly, the AMF receives the path switch request message.

[0492] The path switching request message includes the identifier of UE2's PDU session.

[0493] In step 1312, the AMF sends a session modification request message to the SMF. Correspondingly, the SMF receives the session modification request message.

[0494] Here, SMF refers to the SMF corresponding to the PDU session of UE1. Different PDU sessions of UE1 may correspond to the same SMF or different SMFs; this application does not limit this.

[0495] Optionally, the session modification request message can be an Nsmf_PDUSession_SMContextUpdateRequest message.

[0496] This message instructs SMF to perform a path switch.

[0497] Step 1313: SMF sends the Nx tunnel information of target UPF1 to target UPF2 and source UPF2.

[0498] In step 1314, the SMF sends an End Marker instruction to the source UPF1. Correspondingly, the source UPF1 receives the End Marker instruction.

[0499] The End Marker instruction is used to instruct source UPF1 to send an End Marker to source base station 1, which is then forwarded by source base station 1 to target base station 1. At this point, target base station 1 knows that no more data will be sent from source UPF1, and therefore, target base station 1 can begin processing data from target UPF1.

[0500] Here, it is assumed that before step 1314, all data packets sent from source UPF2 or target UPF2 to source UPF1 have arrived at source UPF1.

[0501] In step 1315, the SMF sends a session modification response message to the AMF. The AMF then receives this session modification response message.

[0502] The session modification response message includes an N4 container, which contains the PFCP session modification response message. This N4 container needs to be sent to the target UPF1.

[0503] Step 1316: The AMF sends a session modification request message to the SMF. Correspondingly, the SMF receives the session modification request message.

[0504] Here, SMF refers to the SMF corresponding to the PDU session of UE2. Different PDU sessions of UE2 may correspond to the same SMF or different SMFs; this application does not limit this.

[0505] Optionally, the session modification request message can be an Nsmf_PDUSession_SMContextUpdateRequest message.

[0506] This message instructs SMF to perform a path switch.

[0507] Step 1317: The AMF sends a path switch response message (PATH SWITCH REQUESTACK) to the target base station 1. The target base station 1 then receives this path switch response message.

[0508] Step 1318: SMF sends the Nx tunneling information of target UPF2 to target UPF1. Correspondingly, target UPF1 receives the Nx tunneling information of target UPF2.

[0509] In step 1319, SMF sends an End Marker instruction to source UPF2. Correspondingly, source UPF2 receives the End Marker instruction.

[0510] The End Marker instruction is used to instruct source UPF2 to send an End Marker to source base station 2. Source UPF2 sends an End Marker to source base station 2, and the End Marker is forwarded by source base station 2 to target base station 2. At this time, target base station 2 knows that no more data will be sent from source UPF2 to target base station 2. Therefore, target base station 2 can start processing the data sent by UPF1 (source UPF1 or target UPF1).

[0511] Here, it is assumed that after step 1318, all the data sent by target UPF1 to source UPF2 has reached source UPF2.

[0512] Step 1320: The SMF sends a session modification response message to the AMF. The AMF then receives this session modification response message.

[0513] The session modification response message is a response to step 1316.

[0514] Step 1321: The AMF sends a path switch response message (PATH SWITCH REQUEST ACK) to the target base station 2. The target base station 2 then receives this path switch response message.

[0515] According to the above scheme, when UE2 is switched over, SMF promptly sends the latest Nx tunnel information corresponding to UE2 to source UPF1. Therefore, source UPF1 can send UE1's data to target UPF2 based on the latest Nx tunnel information, avoiding the need to send the data to source UPF2 and then forward it through the forwarding path between source base station 2 and target base station 2, thus reducing data detours.

[0516] refer to Figure 14 This is a flowchart illustrating a handover method provided in an embodiment of this application. This embodiment can be applied to scenarios where UE1 and UE2 simultaneously handover across satellites due to satellite movement. In this process, UE1's satellite handover occurs. Before the handover, source base station 1 and source UPF1 on satellite 1 provide services to UE1. After the handover, target base station 1 and target UPF1 on satellite 2 provide services to UE1. UE2's satellite handover also occurs. Before the handover, source base station 2 and source UPF2 on satellite 3 provide services to UE2. After the handover, target base station 2 and target UPF2 on satellite 4 provide services to UE2. Figure 14 The embodiments described above are examples of the above. Figure 6 An improvement to the embodiment. Figure 14 The corresponding embodiment is also a specific implementation of the embodiment shown in Figure 7(f) above.

[0517] This embodiment does not optimize the handover process. During the UE handover, both uplink and downlink data of the UE are transmitted through the source UPF. During path handover, the SMF reselects a UPF deployed on the same satellite as the target base station as the target UPF and switches the UE's current UPF to that UPF.

[0518] The process includes the following steps:

[0519] In step 1401, source base station 1 determines that UE1 needs to perform a handover, and sends a handover request message to target base station 1. Accordingly, target base station 1 receives the handover request message.

[0520] The switch request message includes N3 tunnel information for the source UPF1.

[0521] In step 1402, target base station 1 sends a handover response message to source base station 1. Correspondingly, source base station 1 receives the handover response message.

[0522] During steps 1401 and 1402 of the above process, a forwarding tunnel can be established between the source base station 1 and the target base station 1. Therefore, the downlink data sent to UE1 can be sent from the source base station 1 to the target base station 1 through this forwarding tunnel, and the target base station 1 temporarily buffers the downlink data.

[0523] Step 1403: Source base station 1 sends a handover command to UE1. UE1 then receives the handover command.

[0524] The switching command can be an RRC reconfiguration message.

[0525] Step 1404: UE1 synchronizes with target base station 1.

[0526] After receiving the handover command, UE1 initiates a synchronization process with the target base station 1 in order to access the network through the target base station 1.

[0527] In step 1405, UE1 sends a handover completion indication to target base station 1. Accordingly, target base station 1 receives the handover completion indication.

[0528] The switchover completion indication can be an RRC reconfiguration completion message.

[0529] At this time, target base station 1 can send downlink data to UE1.

[0530] UE1 can send uplink data through target base station 1. Target base station 1 can use the N3 tunnel information of source UPF1 received in step 1401 to send uplink data to source UPF1, and then source UPF1 sends uplink data to source UPF2.

[0531] Step 1406: Target base station 2 sends a path switch request message to the AMF. The AMF then receives this path switch request message.

[0532] During this process, UE2 also underwent a cross-satellite handover. The cross-satellite handover procedure for UE2 can be found in steps 1401 to 1404 above. Then, the target base station 2 of UE2 executes step 1406.

[0533] The path switching request includes information for selecting a UPF, such as the identification information of target base station 2 or satellite 4, or the path switching request includes the identification information of target UPF2.

[0534] In addition, the path switching request also includes N3 tunnel information for target base station 2.

[0535] Step 1407: The AMF sends a session modification request message to the SMF. Correspondingly, the SMF receives the session modification request message.

[0536] The session modification request message includes information for selecting a UPF or identification information for the target UPF2.

[0537] In addition, the path switching request also includes N3 tunnel information for target base station 2.

[0538] Optionally, the session modification request message can be an Nsmf_PDUSession_SMContextUpdateRequest message.

[0539] Step 1407a, SMF selects target UPF2.

[0540] For example, if the session modification request message includes information for selecting a UPF, and the information for selecting a UPF is the identification information of target base station 2, then the SMF can send a query request to the NRF, which carries the identification information of target base station 2. The NRF then returns to the SMF the identification information of target UPF2, which is deployed on the same satellite as target base station 2.

[0541] For example, if the session modification request message includes information for selecting a UPF, and the information for selecting a UPF is the identification information of satellite 4, then the SMF can send a query request to the NRF, which carries the identification information of satellite 4, and the NRF returns to the SMF the identification information of the target UPF2 deployed on satellite 4.

[0542] For example, if the session modification request message includes the identification information of the target UPF2, then SMF can directly select that target UPF2.

[0543] Step 1408: Target base station 1 sends a path switch request message to the AMF. Correspondingly, the AMF receives the path switch request message.

[0544] The path switching request includes information for selecting a UPF, such as the identification information of target base station 1 or satellite 2, or the path switching request includes the identification information of target UPF 1.

[0545] In addition, the path switching request also includes N3 tunnel information of target base station 1.

[0546] Step 1409a: The SMF sends a PFCP session establishment request message to the target UPF2. Correspondingly, the target UPF2 receives the PFCP session establishment request message.

[0547] The PFCP session establishment request message includes the Nx tunnel information of the source UPF1 and the N3 tunnel information of the target base station 2.

[0548] Since the SMF has not yet received the Nx tunnel information from the target UPF1, the SMF will still send the Nx tunnel information from the source UPF1 to the target UPF2.

[0549] In step 1409b, the target UPF2 sends a PFCP session establishment response message to the SMF. Correspondingly, the SMF receives this PFCP session establishment response message.

[0550] The PFCP session establishment response message includes N3 tunnel information and Nx tunnel information for the target UPF2.

[0551] Step 1410: The AMF sends a session modification request message to the SMF. Correspondingly, the SMF receives the session modification request message.

[0552] The session modification request message includes information for selecting a UPF or identification information for the target UPF1.

[0553] In addition, the path switching request also includes N3 tunnel information of target base station 1.

[0554] Optionally, steps 1410 and 1409b can be concurrent, meaning they arrive at the SMF almost simultaneously.

[0555] Optionally, the session modification request message can be an Nsmf_PDUSession_SMContextUpdateRequest message.

[0556] Step 1410a, SMF selects target UPF1.

[0557] For example, if the session modification request message includes information for selecting a UPF, and the information for selecting a UPF is the identification information of target base station 1, then the SMF can send a query request to the NRF, which carries the identification information of target base station 1. The NRF then returns to the SMF the identification information of target UPF 1, which is deployed on the same satellite as target base station 1.

[0558] For example, if the session modification request message includes information for selecting a UPF, and the information for selecting a UPF is the identification information of satellite 2, then the SMF can send a query request to the NRF, which carries the identification information of satellite 2, and the NRF returns to the SMF the identification information of the target UPF1 deployed on satellite 2.

[0559] For example, if the session modification request message includes the identification information of the target UPF1, then SMF can directly select the target UPF1.

[0560] Step 1411: SMF sends an N4 update message to source UPF1. Correspondingly, source UPF1 receives the N4 update message.

[0561] The N4 update message includes Nx tunnel information for target UPF2 and an End Marker indication.

[0562] Based on the principle of prioritizing Nx tunnel updates, even if the SMF has already received the handover from UE1, the SMF will suspend the handover process for UE1 and prioritize sending the Nx tunnel information of the target UPF2 to the source UPF1. That is, if the path handover process for UE1 is in progress, after receiving the Nx tunnel information of the target UPF for UE2, the SMF will send the Nx tunnel information of the target UPF2 and the End Marker indication to the source UPF1 before sending the session update response message (step 1417).

[0563] The EndMarker instruction is used to instruct source UPF1 to send an EndMarker through the source path (via source UPF2). Source UPF1 sends the EndMarker according to the EndMarker instruction, through the source path (via source UPF2). Source UPF1 then begins sending the data received from UE1 that needs to be sent to UE2 (i.e., UE2's downlink data) to the target path (via target UPF2). At this point, UE2's downlink data is sent directly to UE2 through target UPF2 and target base station 2, without being forwarded through source UPF2 and source base station 2.

[0564] In step 1412a, the SMF sends a PFCP session establishment request message to the target UPF1. Correspondingly, the target UPF1 receives the PFCP session establishment request message.

[0565] The PFCP session establishment request message includes the N3 tunnel information of the target base station 1 and the Nx tunnel information of the target UPF2.

[0566] In step 1412b, the target UPF1 sends a PFCP session establishment response message to the SMF. Correspondingly, the SMF receives this PFCP session establishment response message.

[0567] The PFCP session establishment response message includes the N3 tunnel information and the Nx tunnel information of the target UPF1.

[0568] In step 1413, SMF sends an N4 update message to source UPF2. Correspondingly, source UPF2 receives the N4 update message.

[0569] The N4 update message includes Nx tunnel information for target UPF1 and an End Marker indication.

[0570] Since the path handover of UE2 has not yet been completed, the target base station 2 is still sending the uplink data of UE2 to the source UPF2. Therefore, the SMF suspends the path handover process of UE2 and sends the Nx tunnel information of the target UPF1 to the source UPF2. That is, if the path handover process of UE2 is in progress, after receiving the Nx tunnel information of the target UPF1, the SMF sends the Nx tunnel information of the target UPF1 and the End Marker indication to the source UPF2 before sending the session update response message (step 1415).

[0571] The EndMarker instruction is used to instruct source UPF2 to send an EndMarker through the source path (via source UPF1). Source UPF2 sends an EndMarker according to the EndMarker instruction, through the source path (via source UPF1). Source UPF2 then begins sending the data received from UE2 that needs to be sent to UE1 (i.e., UE1's downlink data) to the target path (via target UPF1). At this point, source UPF2 begins sending the data received from UE2 that needs to be sent to UE1, i.e., UE1's downlink data, through a new path (via target UPF2).

[0572] Step 1414: SMF sends the Nx tunneling information of target UPF1 to target UPF2. Correspondingly, target UPF2 receives the Nx tunneling information of target UPF1.

[0573] Since the Nx tunnel information of the source UPF1 is sent to the target UPF2 in step 1409a, the SMF needs to notify the target UPF2 to update the Nx tunnel information here.

[0574] Step 1415: The SMF sends a session modification response message to the AMF. Correspondingly, the AMF sends a session modification response message.

[0575] This session modification response message is a session modification response for UE2.

[0576] The session modified response message includes N3 tunnel information for the target UPF2.

[0577] Optionally, the session modification response message can be the Nsmf_PDUSession_SMContextUpdateResponse message.

[0578] In step 1416, the AMF sends a path switch response message (PATH SWITCH REQUEST ACK) to the target base station 2. The target base station 2 then receives this path switch response message.

[0579] The path switching response message includes N3 tunnel information for target UPF2.

[0580] At this time, the data sent by UE2 to UE1 is directly sent by the target base station 2 to the target UPF2, and no longer bypasses the source UPF2.

[0581] Step 1417: The SMF sends a session modification response message to the AMF. Correspondingly, the AMF sends a session modification response message.

[0582] This session modification response message is a session modification response for UE1.

[0583] The session modified response message includes N3 tunnel information for target UPF1.

[0584] Optionally, the session modification response message can be the Nsmf_PDUSession_SMContextUpdateResponse message.

[0585] In step 1418, the AMF sends a path handover response message to the target base station 1. Correspondingly, the target base station 1 receives the path handover response message.

[0586] The path switching response message includes N3 tunnel information for target UPF1.

[0587] According to the above scheme, if the SMF receives new Nx tunnel information during the UE's path handover process, the SMF first suspends the path handover process and prioritizes sending the new Nx tunnel information to the source UPF. After the Nx path handover is completed, the SMF continues the path handover process. Therefore, if concurrent handovers occur at both ends of the communication, the Nx tunnel handover always precedes the UPF handover, effectively decoupling the Nx tunnel handover from the UPF handover. This avoids the loss or out-of-order delivery of some data packets caused by performing UPF handover simultaneously with the Nx path handover.

[0588] It is understood that, in order to implement the functions in the above embodiments, the session management network element, user plane network element, or access network device includes hardware structures and / or software modules corresponding to perform each function. Those skilled in the art should readily recognize that, based on the units and method steps of the various examples described in conjunction with the embodiments disclosed in this application, this application can be implemented in hardware or a combination of hardware and computer software. Whether a function is executed in hardware or by computer software driving hardware depends on the specific application scenario and design constraints of the technical solution.

[0589] Figure 15 and Figure 16 Schematic diagrams of possible communication devices provided for embodiments of this application. These communication devices can be used to implement the above. Figures 7(a) to 7(f) ,as well as Figures 8 to 14 The method embodiments of the present application can achieve the functions of session management network elements, user plane network elements, or access network devices, and thus also realize the beneficial effects of the above-described method embodiments. In the embodiments of this application, the communication device can be a session management network element, a user plane network element, or an access network device, or it can be a module (such as a chip) applied to a session management network element, a user plane network element, or an access network device.

[0590] like Figure 15 As shown, the communication device 1500 includes a processing unit 1510 and a transceiver unit 1520. The communication device 1500 is used to implement the functions of the session management network element, user plane network element, or access network device in the above method embodiments.

[0591] In the first embodiment, the communication device is used to perform the functions of a session management network element. The transceiver unit 1520 is used to receive information from the target user plane network element of the first terminal device indicating that the user plane network element of the first terminal device has been switched, through the target access network device. The information includes tunnel information of the target user plane network element of the first terminal device. The transceiver unit 1520 is used to send the tunnel information of the target user plane network element of the first terminal device to the user plane network element of the second terminal device to update the user plane network element information of the first terminal device in the user plane network element of the second terminal device. The tunnel information of the target user plane network element of the first terminal device is used to send downlink data of the first terminal device to the target user plane network element of the first terminal device.

[0592] In one possible implementation, the transceiver unit 1520 is further configured to send an end marker indication to the user plane network element of the second terminal device, the end marker indication being used to instruct the source user plane network element of the first terminal device to send an end marker.

[0593] In one possible implementation, the second terminal device undergoes a handover, and the user plane network element of the second terminal device is the target user plane network element of the second terminal device; the transceiver unit 1520 is further configured to receive tunnel information of the target user plane network element of the second terminal device before receiving information from the target user plane network element of the first terminal device indicating that the user plane network element of the first terminal device has undergone a handover through the target access network device; send the tunnel information of the target user plane network element of the second terminal device to the source user plane network element of the first terminal device to update the user plane network element information of the second terminal device in the source user plane network element of the first terminal device; and receive a response message from the source user plane network element of the first terminal device rejecting the update.

[0594] In one possible implementation, the transceiver unit 1520 is further configured to receive information from the target user plane network element of the first terminal device indicating that the user plane network element of the first terminal device has been switched, and then send the tunnel information of the target user plane network element of the second terminal device to the target user plane network element of the first terminal device.

[0595] In one possible implementation, the second terminal device undergoes a handover, and the user plane network element of the second terminal device is the target user plane network element of the second terminal device; the transceiver unit 1520 is further configured to receive, after receiving information from the target user plane network element of the first terminal device indicating that the user plane network element of the first terminal device has undergone a handover through the target access network device, receive tunnel information of the target user plane network element of the second terminal device; and send the tunnel information of the target user plane network element of the second terminal device to the target user plane network element of the first terminal device.

[0596] In one possible implementation, the transceiver unit 1520 is further configured to send an end marker indication to the target user plane network element of the first terminal device, the end marker indication being used to instruct the source user plane network element of the second terminal device to send an end marker.

[0597] In one possible implementation, the transceiver unit 1520 is configured to receive a session modification request from a mobility management network element, the session modification request including information indicating that a handover has occurred in the user plane network element of the first terminal device.

[0598] In one possible implementation, the second terminal device undergoes a handover, and the user plane network element of the second terminal device is the target user plane network element of the second terminal device; the transceiver unit 1520 is further configured to receive tunnel information of the target user plane network element of the second terminal device before receiving information from the target user plane network element of the first terminal device indicating that the user plane network element of the first terminal device has undergone a handover through the target access network device; and send the tunnel information of the target user plane network element of the second terminal device to the source user plane network element of the first terminal device.

[0599] In one possible implementation, the transceiver unit 1520 is further configured to send an end marker indication to the source user plane network element of the first terminal device, the end marker indication being used to instruct the source access network device of the first terminal device to send an end marker.

[0600] In one possible implementation, the transceiver unit 1520 is further configured to send an end marker indication to the source user plane network element of the second terminal device, the end marker indication being used to instruct the source access network device of the second terminal device to send an end marker.

[0601] In one possible implementation, the transceiver unit 1520 is further configured to receive information from the target user plane network element of the first terminal device indicating that the user plane network element of the first terminal device has been switched, and then send the tunnel information of the target user plane network element of the second terminal device to the target user plane network element of the first terminal device.

[0602] In one possible implementation, the transceiver unit 1520 is further configured to receive tunnel information of the user plane network element of the second terminal device from the target user plane network element of the first terminal device; if the tunnel information of the user plane network element of the second terminal device from the target user plane network element of the first terminal device is different from the tunnel information of the user plane network element of the second terminal device stored by the session management network element, the transceiver unit 1520 sends the tunnel information of the target user plane network element of the second terminal device to the target user plane network element of the first terminal device.

[0603] In one possible implementation, the transceiver unit 1520 is further configured to receive, after receiving information from the target user plane network element of the first terminal device indicating a handover of the user plane network element of the first terminal device through the target access network device, receive tunnel information of the target user plane network element of the second terminal device; and send the tunnel information of the target user plane network element of the second terminal device to the source user plane network element of the first terminal device and the target user plane network element of the first terminal device.

[0604] In one possible implementation, the transceiver unit 1520 is further configured to send an end marker indication to the source user plane network element of the first terminal device, the end marker indication being used to instruct the source access network device of the first terminal device to send an end marker.

[0605] In one possible implementation, the transceiver unit 1520 is configured to receive a message from a mobility management network element or the target access network device indicating that the first terminal device is undergoing a handover, the message including information indicating that the user plane network element of the first terminal device is undergoing a handover.

[0606] In the second embodiment, the communication device is used to perform the function of the target user plane network element of the first terminal device. The transceiver unit 1520 is used to receive the first tunnel information of the user plane network element of the second terminal device from the source user plane network element of the first terminal device through the target access network device. The first tunnel information of the user plane network element of the second terminal device is used to send downlink data of the second terminal device to the user plane network element of the second terminal device. The first tunnel information of the target user plane network element of the first terminal device is sent to the session management network element through the target access network device. The first tunnel information of the target user plane network element of the first terminal device is used to send downlink data of the first terminal device to the target user plane network element of the first terminal device.

[0607] In one possible implementation, the first tunnel information of the user plane network element of the second terminal device is included in the context of the session of the first terminal device. The context of the session also includes at least one of the following: the session endpoint identifier of the session management network element, the packet detection rule corresponding to the session, and the identification information of the session management network element. The session endpoint identifier of the session management network element is used to identify the session in the session management network element, and the packet detection rule corresponding to the session is used by the target user plane network element of the first terminal device to process the uplink data packets and / or downlink data packets of the first terminal device.

[0608] In one possible implementation, the session corresponds to a local area network (LAN) group. The transceiver unit 1520 is further configured to receive, through the target access network device, packet detection rules corresponding to the LAN group from the source user plane network element of the first terminal device. The packet detection rules corresponding to the LAN group are used by the target user plane network element to process data packets sent to other UEs in the LAN group.

[0609] In one possible implementation, the transceiver unit 1520 is configured to send information indicating a handover of the user plane network element of the first terminal device to the session management network element through the target access network device, the information including the first tunnel information of the target user plane network element of the first terminal device.

[0610] In one possible implementation, the information also includes a session endpoint identifier of the target user plane network element of the first terminal device, which is used to identify the session in the target user plane network element of the first terminal device.

[0611] In one possible implementation, the processing unit 1510 is used to allocate the first tunnel information of the target user plane network element.

[0612] In one possible implementation, the transceiver unit 1520 is further configured to receive tunnel information from the target access network device; and send second tunnel information of the target user plane network element to the target access network device, wherein the second tunnel information of the target user plane network element is used by the target access network device of the first terminal device to send uplink data of the first terminal device to the target user plane network element.

[0613] In one possible implementation, the transceiver unit 1520 is further configured to receive first tunnel information of the target user plane network element of the second terminal device from the session management network element; and send downlink data of the second terminal device to the target user plane network element of the second terminal device.

[0614] In one possible implementation, the transceiver unit 1520 is further configured to receive an end-of-terminal flag indication from the session management network element; and send an end-of-terminal flag to the source user plane network element of the second terminal device according to the end-of-terminal flag indication.

[0615] In the third embodiment, the communication device is used to perform the functions of the source access network device of the first terminal device. The transceiver unit 1520 is used to send a handover preparation request message to the source user plane network element of the first terminal device, the handover preparation request message including the identifier of the session of the first terminal device; receive a handover preparation response message from the source user plane network element, the handover preparation response message including the tunnel information of the user plane network element of the second terminal device corresponding to the session; and send the tunnel information of the user plane network element of the second terminal device to the target user plane network element of the first terminal device through the target access network device.

[0616] In one possible implementation, the transceiver unit 1520 is further configured to receive radio resource information allocated by the target access network device for the session from the target access network device; and send the radio resource information to the first terminal device.

[0617] In one possible implementation, the transceiver unit 1520 is further configured to receive forwarding tunnel information of the target access network device corresponding to the session from the target access network device; and send downlink data of the first terminal device to the target access network device according to the forwarding tunnel information.

[0618] In the fourth embodiment, the communication device is used to perform the function of the target access network device of the first terminal device. The transceiver unit 1520 is used to receive tunnel information of the user plane network element of the second terminal device from the source user plane network element of the first terminal device through the source access network device; and to send the tunnel information of the user plane network element of the second terminal device to the target user plane network element of the first terminal device.

[0619] In one possible implementation, the transceiver unit 1520 is further configured to receive information from the target user plane network element of the first terminal device indicating that the user plane network element of the first terminal device is undergoing a handover, the information including tunnel information of the target user plane network element of the first terminal device; and send the information to the session management network element.

[0620] In one possible implementation, the information also includes a session endpoint identifier of the target user plane network element of the first terminal device, which is used to identify the session in the target user plane network element of the first terminal device.

[0621] In one possible implementation, the tunnel information of the user plane network element of the second terminal device is included in the context of the session of the first terminal device. The context of the session also includes at least one of the following: the session endpoint identifier of the session management network element, the packet detection rule corresponding to the session, and the identification information of the session management network element. The session endpoint identifier of the session management network element is used to identify the session in the session management network element, and the packet detection rule corresponding to the session is used by the target user plane network element of the first terminal device to process the uplink data packets and / or downlink data packets of the first terminal device.

[0622] In one possible implementation, the session corresponds to a local area network (LAN) group. The transceiver unit 1520 is further configured to receive packet detection rules corresponding to the LAN group from the source user plane network element of the first terminal device. The packet detection rules corresponding to the LAN group are used by the target user plane network element of the first terminal device to process data packets sent to other UEs in the LAN group; and to send the packet detection rules corresponding to the LAN group to the target user plane network element of the first terminal device.

[0623] In the fifth embodiment, the communication device is used to perform the functions of a session management network element. The transceiver unit 1520 is used to receive information indicating that the first terminal device is undergoing a handover; receive first tunnel information of the target user plane network element of the second terminal device from the target user plane network element of the second terminal device; send the first tunnel information of the target user plane network element of the second terminal device to the source user plane network element of the first terminal device to update the user plane network element information of the second terminal device in the source user plane network element of the first terminal device; send the first tunnel information of the target user plane network element of the second terminal device to the target user plane network element of the first terminal device; and send the second tunnel information of the target user plane network element of the first terminal device to the target base station of the first terminal device.

[0624] In one possible implementation, the transceiver unit 1520 is further configured to receive information indicating that the second terminal device is undergoing a handover before receiving the first tunnel information of the target user plane network element of the second terminal device from the target user plane network element of the second terminal device; and to send the first tunnel information of the source user plane network element of the first terminal device to the target user plane network element of the second terminal device.

[0625] In one possible implementation, the transceiver unit 1520 is further configured to send an end marker indication to the source user plane network element of the first terminal device, the end marker indication being used to instruct the source user plane network element of the second terminal device to send an end marker.

[0626] A more detailed description of the processing unit 1510 and the transceiver unit 1520 can be obtained directly from the relevant descriptions in the above method embodiments, and will not be repeated here.

[0627] like Figure 16 As shown, the communication device 1600 includes a processor 1610 and an interface circuit 1620. The processor 1610 and the interface circuit 1620 are coupled to each other. It is understood that the interface circuit 1620 can be a transceiver or an input / output interface. Optionally, the communication device 1600 may also include a memory 1630 for storing instructions executed by the processor 1610, or storing input data required by the processor 1610 to execute instructions, or storing data generated after the processor 1610 executes instructions.

[0628] When the communication device 1600 is used to implement the above method embodiment, the processor 1610 is used to implement the function of the processing unit 1510, and the interface circuit 1620 is used to implement the function of the transceiver unit 1520.

[0629] It is understood that the processor in the embodiments of this application may be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, transistor logic devices, hardware components, or any combination thereof. A general-purpose processor may be a microprocessor or any conventional processor.

[0630] The method steps in the embodiments of this application can be implemented in hardware or by a processor executing software instructions. The software instructions can consist of corresponding software modules, which can be stored in random access memory, flash memory, read-only memory, programmable read-only memory, erasable programmable read-only memory, electrically erasable programmable read-only memory, registers, hard disks, portable hard disks, CD-ROMs, or any other form of storage medium known in the art. An exemplary storage medium is coupled to a processor, enabling the processor to read information from and write information to the storage medium. Of course, the storage medium can also be a component of the processor. The processor and storage medium can reside in an ASIC. Alternatively, the ASIC can reside in a base station or terminal. Of course, the processor and storage medium can also exist as discrete components in the base station or terminal.

[0631] In the above embodiments, implementation can be achieved entirely or partially through software, hardware, firmware, or any combination thereof. When implemented using software, it can be implemented entirely or partially in the form of a computer program product. The computer program product includes one or more computer programs or instructions. When the computer program or instructions are loaded and executed on a computer, the processes or functions described in the embodiments of this application are performed entirely or partially. The computer can be a general-purpose computer, a special-purpose computer, a computer network, a base station, a user equipment, or other programmable device. The computer program or instructions can be stored in a computer-readable storage medium or transferred from one computer-readable storage medium to another. For example, the computer program or instructions can be transferred from one website, computer, server, or data center to another website, computer, server, or data center via wired or wireless means. The computer-readable storage medium can be any available medium that a computer can access or a data storage device such as a server or data center that integrates one or more available media. The available medium can be a magnetic medium, such as a floppy disk, hard disk, or magnetic tape; it can also be an optical medium, such as a digital video optical disc; or it can be a semiconductor medium, such as a solid-state drive. The computer-readable storage medium may be a volatile or non-volatile storage medium, or may include both types of storage media.

[0632] In the various embodiments of this application, unless otherwise specified or in case of logical conflict, the terminology and / or descriptions of different embodiments are consistent and can be referenced by each other. The technical features of different embodiments can be combined to form new embodiments according to their inherent logical relationship.

[0633] In this application, "at least one" means one or more, and "more than one" means two or more. "And / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A alone, A and B simultaneously, or B alone, where A and B can be singular or plural. In the textual description of this application, the character " / " generally indicates an "or" relationship between the preceding and following related objects; in the formulas of this application, the character " / " indicates a "division" relationship between the preceding and following related objects.

[0634] It is understood that the various numerical designations used in the embodiments of this application are merely for descriptive convenience and are not intended to limit the scope of the embodiments of this application. The order of the process numbers described above does not imply the order of execution; the execution order of each process should be determined by its function and internal logic.

Claims

1. A switching method, characterized in that, Applications to the switching of a first terminal device from a source access network device to a target access network device, including: The session management network element receives information from the target user plane network element of the first terminal device, indicating that the user plane network element of the first terminal device is being switched, through the target access network device. The information indicating that the user plane network element of the first terminal device is being switched includes the tunnel information of the target user plane network element of the first terminal device. The session management network element sends the tunnel information of the target user plane network element of the first terminal device to the user plane network element of the second terminal device to update the user plane network element information of the first terminal device in the user plane network element of the second terminal device. The tunnel information of the target user plane network element of the first terminal device is used to send the downlink data of the first terminal device to the target user plane network element of the first terminal device. The source access network device and the source user plane network element of the first terminal device are deployed on one satellite, while the target access network device and the target user plane network element of the first terminal device are deployed on another satellite.

2. The method as described in claim 1, characterized in that, The method further includes: The session management network element sends an end marker indication to the user plane network element of the second terminal device. The end marker indication is used to instruct the source user plane network element of the first terminal device to send an end marker.

3. The method as described in claim 1 or 2, characterized in that, When the second terminal device is switched over, the user plane network element of the second terminal device is the target user plane network element of the second terminal device; Before the session management network element receives information from the target user plane network element of the first terminal device indicating that the user plane network element of the first terminal device is undergoing handover through the target access network device, the method further includes: The session management network element receives tunnel information from the target user plane network element of the second terminal device; The session management network element sends the tunnel information of the target user plane network element of the second terminal device to the source user plane network element of the first terminal device to update the user plane network element information of the second terminal device in the source user plane network element of the first terminal device. The session management network element receives a response message from the source user plane network element of the first terminal device, indicating a refusal to update.

4. The method as described in claim 3, characterized in that, After the session management network element receives information from the target user plane network element of the first terminal device indicating that the user plane network element of the first terminal device has undergone handover through the target access network device, the method further includes: The session management network element sends the tunnel information of the target user plane network element of the second terminal device to the target user plane network element of the first terminal device.

5. The method as described in claim 1 or 2, characterized in that, When the second terminal device is switched over, the user plane network element of the second terminal device is the target user plane network element of the second terminal device; After the session management network element receives information from the target user plane network element of the first terminal device indicating that the user plane network element of the first terminal device has undergone handover through the target access network device, the method further includes: The session management network element receives tunnel information from the target user plane network element of the second terminal device; The session management network element sends the tunnel information of the target user plane network element of the second terminal device to the target user plane network element of the first terminal device.

6. The method as described in claim 4, characterized in that, The method further includes: The session management network element sends an end marker indication to the target user plane network element of the first terminal device. The end marker indication is used to instruct the source user plane network element of the second terminal device to send an end marker.

7. The method as described in claim 5, characterized in that, The method further includes: The session management network element sends an end marker indication to the target user plane network element of the first terminal device. The end marker indication is used to instruct the source user plane network element of the second terminal device to send an end marker.

8. The method according to any one of claims 4, 6, and 7, characterized in that, The session management network element receives information from the target user plane network element of the first terminal device, indicating that the user plane network element of the first terminal device is undergoing handover, through the target access network device, including: The session management network element receives a session modification request from the mobility management network element, the session modification request including information indicating that the user plane network element of the first terminal device has undergone handover.

9. The method as described in claim 5, characterized in that, The session management network element receives information from the target user plane network element of the first terminal device, indicating that the user plane network element of the first terminal device is undergoing handover, through the target access network device, including: The session management network element receives a session modification request from the mobility management network element, the session modification request including information indicating that the user plane network element of the first terminal device has undergone handover.

10. The method as described in claim 1, characterized in that, The second terminal device undergoes a handover, and the user plane network element of the second terminal device is the target user plane network element of the second terminal device; before the session management network element receives information from the target user plane network element of the first terminal device indicating that the user plane network element of the first terminal device has undergone a handover through the target access network device, the method further includes: The session management network element receives tunnel information from the target user plane network element of the second terminal device; The session management network element sends the tunnel information of the target user plane network element of the second terminal device to the source user plane network element of the first terminal device.

11. The method as described in claim 10, characterized in that, The method further includes: The session management network element sends an end marker indication to the source user plane network element of the first terminal device. The end marker indication is used to instruct the source access network device of the first terminal device to send an end marker.

12. The method as described in claim 10, characterized in that, The method further includes: The session management network element sends an end marker indication to the source user plane network element of the second terminal device. The end marker indication is used to instruct the source access network device of the second terminal device to send an end marker.

13. The method according to any one of claims 10 to 12, characterized in that, After the session management network element receives information from the target user plane network element of the first terminal device indicating that the user plane network element of the first terminal device has undergone handover through the target access network device, the method further includes: The session management network element sends the tunnel information of the target user plane network element of the second terminal device to the target user plane network element of the first terminal device.

14. The method as described in claim 13, characterized in that, The method further includes: The session management network element receives tunnel information from the target user plane network element of the first terminal device and the source user plane network element of the second terminal device; The session management network element sends the tunnel information of the target user plane network element of the second terminal device to the target user plane network element of the first terminal device, including: If the tunnel information of the source user plane network element of the second terminal device from the target user plane network element of the first terminal device is different from the tunnel information of the target user plane network element of the second terminal device stored by the session management network element, the session management network element sends the tunnel information of the target user plane network element of the second terminal device to the target user plane network element of the first terminal device.

15. The method as described in claim 1, characterized in that, After the session management network element receives information from the target user plane network element of the first terminal device indicating that the user plane network element of the first terminal device has undergone handover through the target access network device, the method further includes: The session management network element receives tunnel information from the target user plane network element of the second terminal device; The session management network element sends the tunnel information of the target user plane network element of the second terminal device to the source user plane network element and the target user plane network element of the first terminal device.

16. The method as described in claim 15, characterized in that, The method further includes: The session management network element sends an end marker indication to the source user plane network element of the first terminal device. The end marker indication is used to instruct the source access network device of the first terminal device to send an end marker.

17. The method according to any one of claims 10 to 12, 14 to 16, characterized in that, The session management network element receives information from the target user plane network element of the first terminal device, indicating that the user plane network element of the first terminal device is undergoing handover, through the target access network device, including: The session management network element receives a message from the mobility management network element or the target access network device indicating that the first terminal device is undergoing a handover, the message including information indicating that the user plane network element of the first terminal device is undergoing a handover.

18. The method as described in claim 13, characterized in that, The session management network element receives information from the target user plane network element of the first terminal device, indicating that the user plane network element of the first terminal device is undergoing handover, through the target access network device, including: The session management network element receives a message from the mobility management network element or the target access network device indicating that the first terminal device is undergoing a handover, the message including information indicating that the user plane network element of the first terminal device is undergoing a handover.

19. A switching method, characterized in that, Applications to the switching of a first terminal device from a source access network device to a target access network device, including: The target user plane network element of the first terminal device receives the first tunnel information of the user plane network element of the second terminal device from the source user plane network element of the first terminal device through the target access network device. The first tunnel information of the user plane network element of the second terminal device is used to send the downlink data of the second terminal device to the user plane network element of the second terminal device. The target user plane network element sends the first tunnel information of the target user plane network element of the first terminal device to the session management network element through the target access network device. The first tunnel information of the target user plane network element of the first terminal device is used to send the downlink data of the first terminal device to the target user plane network element of the first terminal device. The source access network device and the source user plane network element of the first terminal device are deployed on one satellite, while the target access network device and the target user plane network element of the first terminal device are deployed on another satellite.

20. The method as described in claim 19, characterized in that, The first tunnel information of the user plane network element of the second terminal device is included in the context of the session of the first terminal device. The context of the session also includes at least one of the session endpoint identifier of the session management network element, the packet detection rule corresponding to the session, and the identification information of the session management network element. The session endpoint identifier of the session management network element is used to identify the session in the session management network element. The packet detection rule corresponding to the session is used by the target user plane network element of the first terminal device to process the uplink data packets and / or downlink data packets of the first terminal device.

21. The method as described in claim 20, characterized in that, The session corresponds to a local area network (LAN) group, and the method further includes: The target user plane network element receives the packet detection rules corresponding to the LAN group from the source user plane network element of the first terminal device through the target access network device. The packet detection rules corresponding to the LAN group are used by the target user plane network element to process data packets sent to other UEs in the LAN group.

22. The method according to any one of claims 19 to 21, characterized in that, The target user plane network element sends the first tunnel information of the target user plane network element of the first terminal device to the session management network element through the target access network device, including: The target user plane network element sends information to the session management network element through the target access network device, indicating that the user plane network element of the first terminal device should be switched. The information indicating that the user plane network element of the first terminal device should be switched includes the first tunnel information of the target user plane network element of the first terminal device.

23. The method as described in claim 22, characterized in that, The information indicating that the user plane network element of the first terminal device has been switched also includes the session endpoint identifier of the target user plane network element of the first terminal device. The session endpoint identifier of the target user plane network element of the first terminal device is used to identify the session in the target user plane network element of the first terminal device.

24. The method according to any one of claims 19 to 21, 23, characterized in that, The method further includes: The target user plane network element receives tunnel information from the target access network device. The target user plane network element sends its second tunnel information to the target access network device. The second tunnel information of the target user plane network element is used by the target access network device of the first terminal device to send the uplink data of the first terminal device to the target user plane network element.

25. The method as described in claim 22, characterized in that, The method further includes: The target user plane network element receives tunnel information from the target access network device. The target user plane network element sends its second tunnel information to the target access network device. The second tunnel information of the target user plane network element is used by the target access network device of the first terminal device to send the uplink data of the first terminal device to the target user plane network element.

26. The method according to any one of claims 19 to 21, 23, and 25, characterized in that, The method further includes: The target user plane network element receives the first tunnel information of the target user plane network element of the second terminal device from the session management network element; The target user plane network element sends the downlink data of the second terminal device to the target user plane network element of the second terminal device.

27. The method as described in claim 22, characterized in that, The method further includes: The target user plane network element receives the first tunnel information of the target user plane network element of the second terminal device from the session management network element; The target user plane network element sends the downlink data of the second terminal device to the target user plane network element of the second terminal device.

28. The method as described in claim 24, characterized in that, The method further includes: The target user plane network element receives the first tunnel information of the target user plane network element of the second terminal device from the session management network element; The target user plane network element sends the downlink data of the second terminal device to the target user plane network element of the second terminal device.

29. The method according to any one of claims 19 to 21, 23, 25, 27, and 28, characterized in that, Also includes: The target user plane network element receives an end marker indication from the session management network element; The target user plane network element sends an end marker to the source user plane network element of the second terminal device according to the end marker instruction.

30. The method as described in claim 22, characterized in that, Also includes: The target user plane network element receives an end marker indication from the session management network element; The target user plane network element sends an end marker to the source user plane network element of the second terminal device according to the end marker instruction.

31. The method as described in claim 24, characterized in that, Also includes: The target user plane network element receives an end marker indication from the session management network element; The target user plane network element sends an end marker to the source user plane network element of the second terminal device according to the end marker instruction.

32. The method as described in claim 26, characterized in that, Also includes: The target user plane network element receives an end marker indication from the session management network element; The target user plane network element sends an end marker to the source user plane network element of the second terminal device according to the end marker instruction.

33. A communication device, characterized in that, Includes a module for performing the method as described in any one of claims 1 to 18.

34. A communication device, characterized in that, Includes modules for performing the method as described in any one of claims 19 to 32.

35. A communication device, characterized in that, The device includes a processor and an interface circuit, wherein the interface circuit is used to receive signals from other communication devices besides the communication device and transmit them to the processor, or to send signals from the processor to other communication devices besides the communication device, and the processor is used to implement the method as described in any one of claims 1 to 18 through logic circuits or execution code instructions.

36. A communication device, characterized in that, The device includes a processor and an interface circuit, wherein the interface circuit is used to receive signals from other communication devices besides the communication device and transmit them to the processor, or to send signals from the processor to other communication devices besides the communication device, and the processor is used to implement the method as described in any one of claims 19 to 32 through logic circuits or execution code instructions.

37. A computer program product, characterized in that, Includes a computer program that, when executed by a communication device, implements the method as described in any one of claims 1 to 32.

38. A computer-readable storage medium, characterized in that, The storage medium stores a computer program or instructions, which, when executed by a communication device, implement the method as described in any one of claims 1 to 32.

39. A communication system, characterized in that, Includes the session management network element as described in any one of claims 1 to 18, and the target user plane network element of the first terminal device; The target user plane network element of the first terminal device is used to send information indicating that the user plane network element of the first terminal device should be switched to the session management network element through the target access network device of the first terminal. The information indicating that the user plane network element of the first terminal device should be switched includes the tunnel information of the target user plane network element of the first terminal device.

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