WO2023116568A1 - 一种切换方法、通信装置及通信系统 - Google Patents

一种切换方法、通信装置及通信系统 Download PDF

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Publication number
WO2023116568A1
WO2023116568A1 PCT/CN2022/139599 CN2022139599W WO2023116568A1 WO 2023116568 A1 WO2023116568 A1 WO 2023116568A1 CN 2022139599 W CN2022139599 W CN 2022139599W WO 2023116568 A1 WO2023116568 A1 WO 2023116568A1
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WIPO (PCT)
Prior art keywords
network element
terminal device
user plane
target
plane network
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PCT/CN2022/139599
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English (en)
French (fr)
Inventor
宗在峰
张成晨
屈琴
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华为技术有限公司
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Publication of WO2023116568A1 publication Critical patent/WO2023116568A1/zh

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W36/00—Hand-off or reselection arrangements
    • H04W36/0005—Control or signalling for completing the hand-off
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W36/00—Hand-off or reselection arrangements
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W36/00—Hand-off or reselection arrangements
    • H04W36/0005—Control or signalling for completing the hand-off
    • H04W36/0011—Control or signalling for completing the hand-off for data sessions of end-to-end connection

Definitions

  • the present application relates to the technical field of communication, and in particular to a handover method, a communication device and a communication system.
  • the access network equipment and user plane network elements that provide services for terminal equipment can be deployed on satellites. Based on this scenario, when the access network equipment and/or user plane network elements that provide services for terminal equipment are switched, How to realize correct switching remains to be solved.
  • Embodiments of the present application provide a handover method, a communication device, and a communication system, so as to implement correct handover of access network equipment and/or user plane network elements that provide services for terminal equipment.
  • the embodiment of the present application provides a handover method.
  • the 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 receives, through the target access network device of the first terminal device, 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 handed over, the The information includes 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 among the user plane network elements of the second terminal device, the tunnel information of the target user plane network element of the first terminal device is used to The network element sends the downlink data of the first terminal device.
  • the switched target user plane network element when the user plane network element providing services for the first terminal device is switched, the switched target user plane network element sends information indicating that the user plane network element of the first terminal device is switched to the session management network element, And carry the tunnel information of the switched target user plane network element in this information, so that the session management network element can timely provide the tunnel information of the switched target user plane network element of the first terminal device to the second terminal device.
  • the user plane network element ensures correct execution of handover.
  • the session management network element sends an end mark indication to the user plane network element of the second terminal device, where the end mark indication is used to indicate to send the end tag.
  • the second terminal device is handed over, and the user plane network element of the second terminal device is the target user plane network element of the second terminal device; the session management network element accesses the Before the network device receives the 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 switched, the session management network element receives the target user plane network element of the second terminal device tunnel information; 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 source user plane network element of the first terminal device Information about the user plane network element of the second terminal device; the session management network element receives a response message of refusing to update from the source user plane network element of the first terminal device.
  • the session management network element receives information from the target user plane network element of the first terminal device through the target access network device indicating that the user plane network element of the first terminal device is handed over Afterwards, 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.
  • the second terminal device is handed over, and the user plane network element of the second terminal device is the target user plane network element of the second terminal device; the session management network element passes the target access network element After the 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 switched, the session management network element receives the tunnel of the target user plane network element of the second terminal device Information: 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.
  • the session management network element sends an end mark indication to the target user plane network element of the first terminal device, where the end mark indication is used to indicate that the source user plane network element of the second terminal device Send end marker.
  • the session management network element receives a session modification request from a mobility management network element, where the session modification request includes information indicating that the user plane network element of the first terminal device is switched.
  • the second terminal device is handed over, and the user plane network element of the second terminal device is the target user plane network element of the second terminal device; the session management network element accesses the Before the network device receives the 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 switched, the session management network element receives 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.
  • the session management network element sends an end mark indication to the source user plane network element of the first terminal device, where the end mark indication is used to indicate that the source access network device of the first terminal device Send end marker.
  • the session management network element sends an end mark indication to the source user plane network element of the second terminal device, where the end mark indication is used to indicate that the source access network device of the second terminal device Send end marker.
  • the session management network element receives information from the target user plane network element of the first terminal device through the target access network device indicating that the user plane network element of the first terminal device is handed over Afterwards, 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.
  • the session management network element receives the 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;
  • the tunnel information of the source user plane network element of the second terminal device in the target user plane network element of the target user plane network element is different from the tunnel information of the target user plane network element of the second terminal device stored in the session management network element, and the session management network element Sending 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.
  • the session management network element receives information from the target user plane network element of the first terminal device through the target access network device indicating that the user plane network element of the first terminal device is handed over Afterwards, 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 source user plane network element of the first terminal device and the target user plane network element of the first terminal device The network element sends the tunnel information of the target user plane network element of the second terminal device.
  • the session management network element sends an end mark indication to the source user plane network element of the first terminal device, where the end mark indication is used to indicate that the source access network device of the first terminal device Send end marker.
  • the session management network element receives a message indicating that the first terminal device is handing over from the mobility management network element or the target access network device, and the message includes a message indicating that the first terminal device Information about handover of user plane network elements.
  • the embodiment of the present application provides a handover method.
  • the method may 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: the target user plane network element of the first terminal device receives the first 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 of the first terminal device.
  • Tunnel information 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 passes the target The access network device sends the first tunnel information of the target user plane network element of the first terminal device to the session management network element, and the first tunnel information of the target user plane network element of the first terminal device is used to send the first tunnel information to the first terminal device The target user plane network element of the device sends the downlink data of the first terminal device.
  • the switched target user plane network element when the user plane network element serving the first terminal device is switched, receives the user plane network element of the second terminal device, and sends the switched target network element to the session management network element.
  • the first tunnel information of the user plane network element so that the session management network element can provide the first tunnel information of the target user plane network element of the first terminal device after switching to the user plane network element of the second terminal device in a timely manner, ensuring correct implementation of the switch.
  • the first tunnel information of the user plane network element of the second terminal device is included in the session context of the first terminal device, and the session context also includes the session of the session management network element At least one of the endpoint identifier, the packet detection rule corresponding to the session, and the identifier 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 session corresponding to the The packet detection rule is used for the target user plane network element of the first terminal device to process the uplink data packet and/or downlink data packet of the first terminal device.
  • the session corresponds to a local area network LAN group
  • the target user plane network element receives the LAN group correspondence from the source user plane network element of the first terminal device through the target access network device.
  • the packet detection rule corresponding to the LAN group is used for the target user plane network element to process the data packets sent to other UEs in the LAN group.
  • the target user plane network element sends information indicating that the user plane network element of the first terminal device is handed over to the session management network element through the target access network device, and the first terminal device's
  • the information about the handover of the user plane network element includes the first tunnel information of the target user plane network element of the first terminal device.
  • the information about the handover of the user plane network element of the first terminal device also includes the session endpoint identifier of the target user plane network element of the first terminal device, and the target user plane network element of the first terminal device The session endpoint identifier of the network element is used to identify the session in the target user plane network element of the first terminal device.
  • the target user plane network element allocates the first tunnel information of the target user plane network element.
  • the target user plane network element receives tunnel information of the target access network device from the target access network device; the target user plane network element sends the target user plane information to the target access network device
  • the second tunnel information of the target user plane network element, 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.
  • 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 second terminal device The target user plane network element sends the downlink data of the second terminal device.
  • the target user plane network element receives an end mark indication from a session management network element; and the target user plane network element sends an end mark indication to the source user plane network element of the second terminal device according to the end mark indication end tag.
  • the embodiment of the present application provides a handover method.
  • the first terminal device is handed over, and the method can be executed by the 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 sends a handover preparation request message to a source user plane network element of the first terminal device, where the handover preparation request message includes a session identifier of the first terminal device;
  • the network access device receives a handover preparation response message from the source user plane network element, where the handover preparation response message includes tunnel information of the user plane network element of the second terminal device corresponding to the session;
  • the network access device sends 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.
  • the source user plane network element of the first terminal device before handover provides the tunnel information of the user plane network element of the second terminal to the handover of the first terminal device through the source access network device of the first terminal device
  • the final target user plane network element can speed up the handover process and ensure the accurate execution of the handover.
  • the source access network device receives from the target access network device the radio resource information allocated by the target access network device for the session; the source access network device sends the first terminal device Send the radio resource information.
  • 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, according to the forwarding tunnel information, Send the downlink data of the first terminal device to the target access network device.
  • the embodiment of the present application provides a handover method.
  • the method can be executed by the access network device or a module (such as a chip) applied to the access network device.
  • the method includes: the target access network device of the first terminal device receives the tunnel from 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 of the first terminal device Information: the target access network device sends 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.
  • the source user plane network element of the first terminal device before handover provides the tunnel information of the user plane network element of the second terminal to the handover of the first terminal device through the source access network device of the first terminal device
  • the final target user plane network element can speed up the handover process and ensure the accurate execution of the handover.
  • 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 switched, and the information includes the first Tunnel information of a target user plane network element of a terminal device; the target access network device sends the information to a session management network element.
  • the information further includes the session endpoint identifier of the target user plane network element of the first terminal device, and the session endpoint identifier of the target user plane network element of the first terminal device is used in the first terminal device The session is identified in the target user plane network element of the terminal device.
  • the tunnel information of the user plane network element of the second terminal device is included in the session context of the first terminal device, and the session context also includes the session endpoint identifier of the session management network element , at least one of 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 The rule is used for the target user plane network element of the first terminal device to process the uplink data packet and/or downlink data packet of the first terminal device.
  • the session corresponds to a local area network LAN group
  • the target access network device receives the packet detection rule corresponding to the LAN group from the source user plane network element of the first terminal device, and the LAN
  • the packet detection rule corresponding to the group is 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 network element sends the packet inspection rule corresponding to the LAN group.
  • the embodiment of the present application provides a handover method, where the handover between the first terminal device and the second terminal device occurs, and the method can be executed by a session management network element or a module (such as a chip) applied to a session management network element .
  • the method includes: the session management network element receives information indicating handover of the first terminal device; the session management network element receives first tunnel information from the target user plane network element of the second terminal device; the session management network element sends the first tunnel information to the second terminal device
  • the source user plane network element of a terminal device sends the first tunnel information of the target user plane network element of the second terminal device to update the user plane network element of the second terminal device among the source user plane network elements of the first terminal device information
  • 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 the target user plane network element of the first terminal device
  • the access network device sends the second tunnel information of the target user plane network element of the first terminal device.
  • the session management network element 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 The element receives the information indicating that the handover of the second terminal device occurs; 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.
  • the session management network element 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 Sending an end marker indication to the source user plane network element of the first terminal device, where the end marker indication is used to instruct sending an end marker to the source user plane network element of the second terminal device.
  • the embodiment of the present application provides a communication device, which may be a session management network element or a module (such as a chip) applied to the session management network element.
  • the device has the function of implementing any implementation method of the first aspect or the fifth aspect. This function may be implemented by hardware, or may be implemented by executing corresponding software on the hardware.
  • the hardware or software includes one or more modules corresponding to the above functions.
  • the embodiment of the present application provides a communication device, and the device may be a user plane network element or a module (such as a chip) applied to the user plane network element.
  • the device has the function of implementing any implementation method of the second aspect above. This function may be implemented by hardware, or may be implemented by executing corresponding software on the hardware.
  • the hardware or software includes one or more modules corresponding to the above functions.
  • the embodiment of the present application provides a communication device, and the device may be a user plane network element or a module (such as a chip) applied to the user plane network element.
  • the device has the function of realizing any realization method of the above-mentioned third aspect or fourth aspect. This function may be implemented by hardware, or may be implemented by executing corresponding software on the hardware.
  • the hardware or software includes one or more modules corresponding to the above functions.
  • an embodiment of the present application provides a communication device, including a processor coupled to a memory, and the processor is used to call a program stored in the memory to execute any implementation method in the first aspect to the fifth aspect above .
  • the memory may be located within the device or external to the device. And there may be one or more processors.
  • the embodiment of the present application provides 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 so that the device executes Any implementation method in the first aspect to the fifth aspect above.
  • the embodiment of the present application provides a communication device, including a unit or means (means) for performing each step of any implementation method in the first aspect to the fifth aspect.
  • the embodiment of the present application provides a communication device, including a processor and an interface circuit, the processor is used to communicate with other devices through the interface circuit, and execute any implementation method in the first to fifth aspects above .
  • the processor includes one or more.
  • the embodiment of the present application further provides a chip system, including: a processor, configured to execute any implementation method in the first aspect to the fifth aspect above.
  • the embodiment of the present application also provides a computer-readable storage medium, the computer-readable storage medium stores instructions, and when it is run on a communication device, the above-mentioned first to fifth aspects Any implementation method of is executed.
  • the embodiment of the present application also provides a computer program product, the computer program product includes a computer program or instruction, when the computer program or instruction is run by the communication device, any of the above first to fifth aspects The implementation method is executed.
  • the embodiment of the present application is a communication system, including a communication device that executes any implementation method in the above-mentioned first aspect, a communication device that executes any implementation method in the above-mentioned second aspect, and executes any implementation method in the above-mentioned third aspect Any multiple of the communication device, the communication device implementing any method in the fourth aspect above, or the communication device implementing any method in the fifth aspect above.
  • Figure 1(a) is a schematic diagram of a 5G network architecture based on a service architecture
  • Figure 1(b) is a schematic diagram of a 5G network architecture based on a point-to-point interface
  • FIG. 2 is a schematic diagram of a communication path between UEs
  • 3 is a schematic diagram of a communication path between UEs
  • FIG. 4 is a schematic diagram of a communication path between UEs
  • FIG. 5 is a schematic flowchart of a switching method provided in an embodiment of the present application.
  • FIG. 6 is a schematic flowchart of a handover method provided in an embodiment of the present application.
  • FIG. 7(a) is a schematic flowchart of a handover method provided by an embodiment of the present application.
  • FIG. 7(b) is a schematic flowchart of a handover method provided by the embodiment of the present application.
  • FIG. 7(c) is a schematic flowchart of a handover method provided in the embodiment of the present application.
  • Fig. 7(d) is a schematic flowchart of a handover method provided by the embodiment of the present application.
  • FIG. 7(e) is a schematic flowchart of a handover method provided by an embodiment of the present application.
  • FIG. 7(f) is a schematic flowchart of a handover method provided by an embodiment of the present application.
  • FIG. 8 is a schematic flowchart of a handover method provided by an embodiment of the present application.
  • FIG. 9 is a schematic flowchart of a switching method provided in an embodiment of the present application.
  • FIG. 10 is a schematic flowchart of a handover method provided in an embodiment of the present application.
  • FIG. 11 is a schematic flowchart of a handover method provided by an embodiment of the present application.
  • FIG. 12 is a schematic flowchart of a handover method provided by an embodiment of the present application.
  • FIG. 13 is a schematic flowchart of a handover method provided by an embodiment of the present application.
  • FIG. 14 is a schematic flowchart of a handover method provided in an embodiment of the present application.
  • FIG. 15 is a schematic diagram of a communication device provided by an embodiment of the present application.
  • FIG. 16 is a schematic diagram of a communication device provided by an embodiment of the present application.
  • next generation mobile communication network system Next Generation System
  • 5G network architecture Next Generation Mobile communication network system
  • This architecture not only supports wireless access technologies defined by the 3GPP standard group (such as long term evolution (LTE) access technologies, 5G radio access network (RAN) access technologies, etc.) to access the 5G core Network (core network, CN), and supports the use of non-3GPP (non-3GPP) access technology through non-3GPP interworking function (non-3GPP interworking function, N3IWF) or next generation access gateway (next generation packet data gateway, ngPDG) Access to the core network.
  • LTE long term evolution
  • RAN radio access network
  • N3IWF non-3GPP interworking function
  • N3IWF next generation access gateway
  • ngPDG next generation packet data gateway
  • Figure 1(a) is a schematic diagram of a 5G network architecture based on a service-based architecture.
  • the 5G network architecture shown in Figure 1(a) may include access network equipment and core network equipment.
  • the terminal device accesses the data network (data network, DN) through the access network device and the core network device.
  • data network data network
  • the core network equipment includes but not limited to some or all of the following network elements: authentication server function (authentication server function, AUSF) network element (not shown in the figure), unified data management (unified data management, UDM) network element, unified data repository (unified data repository, UDR) network element, network repository function (network repository function, NRF) network element (not shown in the figure), network exposure function (network exposure function, NEF) network element (not shown in the figure) shown), application function (application function, AF) network element, policy control function (policy control function, PCF) network element, access and mobility management function (access and mobility management function, AMF) network element, session management function (session management function, SMF) network element, user plane function (user plane function, UPF) network element, binding support function (binding support function, BSF) network element (not shown in the figure).
  • authentication server function authentication server function, AUSF
  • UDM authentication server function
  • UDR unified data repository
  • NRF network repository function
  • NEF network exposure function
  • AMF access
  • the terminal equipment may be a user equipment (user equipment, UE), a mobile station, a mobile terminal equipment, and the like.
  • Terminal devices can be widely used in various scenarios, such as device-to-device (D2D), vehicle-to-everything (V2X) communication, machine-type communication (MTC), Internet of Things (internet of things, IOT), virtual reality, augmented reality, industrial control, automatic driving, telemedicine, smart grid, smart furniture, smart office, smart wear, smart transportation, smart city, etc.
  • Terminal devices can be mobile phones, tablet computers, computers with wireless transceiver functions, wearable devices, vehicles, urban air vehicles (such as drones, helicopters, etc.), ships, robots, robotic arms, smart home devices, etc.
  • the access network device may be a radio access network (RAN) device or a wired access network (wireline access network, FAN) device.
  • the wireless access network 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 not limited to: evolved base station (evolved NodeB, eNodeB) in LTE, next generation base station (next generation NodeB, gNB) in 5G mobile communication system, base station or completed base station in future mobile communication system Modules or units with some functions, such as centralized unit (central unit, CU), distributed unit (distributed unit, DU), etc.
  • Untrusted non-3GPP access network equipment includes but not limited to: untrusted non-3GPP access gateway or N3IWF equipment, untrusted wireless local area network (wireless local area network, WLAN) access point (access point, AP), switch ,router.
  • Trusted non-3GPP access network devices include, but are not limited to: trusted non-3GPP access gateways, trusted WLAN APs, switches, and routers.
  • Wired access network equipment includes but not limited to: wired access gateway (wireline access gateway), fixed telephone network equipment, switches, routers.
  • Access network equipment and terminal equipment can be fixed or mobile. Access network equipment and terminal equipment can be deployed on land, including indoor or outdoor, handheld or vehicle-mounted; they can also be deployed on water; they can also be deployed on aircraft, balloons and artificial satellites in the air.
  • the embodiments of the present application do not limit the application scenarios of the access network device and the terminal device.
  • the AMF network element includes functions such as mobility management and access authentication/authorization. In addition, it is also responsible for transmitting user policies between terminal equipment and PCF network elements.
  • the SMF network element includes the functions of executing session management, executing the control strategy issued by the PCF, selecting UPF, and assigning the Internet protocol (internet protocol, IP) address of the terminal device, etc.
  • UPF network element including the functions of completing user plane data forwarding, session/flow level-based accounting statistics, and bandwidth limitation.
  • UDM network element including the execution management of subscription data, user access authorization and other functions.
  • the UDR network element includes the access function for performing subscription data, policy data, application data and other types of data.
  • NEF network elements are used to support the opening of capabilities and events.
  • the AF network element transmits the requirements from the application side to the network side, such as QoS requirements or user status event subscription.
  • the AF may be a third-party functional entity, or an application service deployed by an operator, such as an IP Multimedia Subsystem (IP Multimedia Subsystem, IMS) voice call service.
  • IP Multimedia Subsystem IP Multimedia Subsystem
  • the AF network element includes an AF network element in the core network (that is, an operator's AF network element) and a third-party AF network element (such as an application server of an enterprise).
  • PCF network elements include policy control functions such as charging for sessions and service flow levels, QoS bandwidth guarantee, mobility management, and terminal equipment policy decisions.
  • PCF network elements include access and mobility management policy control function (access and mobility management policy control function, AM PCF) network elements and session management policy control function (session management PCF, SM PCF) network elements.
  • AM PCF access and mobility management policy control function
  • AM PCF access and mobility management policy control function
  • SM PCF session management policy control function
  • the AM PCF network element is used to formulate an AM policy for the terminal device
  • the AM PCF network element can also be called a policy control network element (PCF for a UE) that provides services for the terminal device.
  • PCF policy control network element
  • the SM PCF network element is used to formulate a session management policy (session management policy, SM policy) for the session, and the SM PCF network element can also be called a policy control network element ((PCF for a PDU session)) that provides services for the session.
  • SM policy session management policy
  • PCF policy control network element
  • the NRF network element can be used to provide a network element discovery function, and provide network element information corresponding to the network element type based on the request of other network elements.
  • NRF also provides network element management services, such as network element registration, update, de-registration, network element status subscription and push, etc.
  • BSF network element can provide functions such as BSF service registration/deregistration/update, connection detection with NRF, creation of session binding information, acquisition of UE information, query of session binding information with duplicate IP addresses, etc.
  • the AUSF network element is responsible for authenticating users to determine whether users or devices are allowed to access the network.
  • DN is a network outside the operator's network.
  • the operator's network can access multiple DNs, and various services can be deployed on the DN, which can provide data and/or voice services for terminal equipment.
  • DN is a private network of a smart factory.
  • the sensors installed in the workshop of the smart factory can be terminal devices.
  • the control server of the sensor is deployed in the DN, and the control server can provide services for the sensor.
  • the sensor can communicate with the control server, obtain instructions from the control server, and transmit the collected sensor data to the control server according to the instructions.
  • DN is a company's internal office network, and the mobile phone or computer of the company's employees can be a terminal device, and the employee's mobile phone or computer can access information and data resources on the company's internal office network.
  • Npcf, Nufr, Nudm, Naf, Namf, and Nsmf are the service interfaces provided by the above-mentioned PCF, UDR, UDM, AF, AMF, and SMF, respectively, and are used to call corresponding service operations.
  • N1, N2, N3, N4, and N6 are interface serial numbers. The meanings of these interface serial numbers are as follows:
  • N1 the interface between the AMF and the terminal device, which can be used to transmit non-access stratum (non access stratum, NAS) signaling (such as including QoS rules from the AMF) to the terminal device.
  • non-access stratum non access stratum, NAS
  • N2 the interface between the AMF and the access network device, which can be used to transfer radio bearer control information from the core network side to the access network device.
  • N3 the interface between the access network device and the UPF, mainly used to transfer the uplink and downlink user plane data between the access network device and the UPF.
  • N4 The interface between SMF and UPF, which can be used to transfer information between the control plane and the user plane, including controlling the delivery of forwarding rules, QoS rules, traffic statistics rules, etc. for the user plane, as well as user plane information report.
  • N6 interface between UPF and DN, used to transmit uplink and downlink user data flow between UPF and DN.
  • Figure 1(b) is a schematic diagram of a 5G network architecture based on a point-to-point interface, and the introduction of the functions of the network elements can refer to the introduction of the functions of the corresponding network elements in Figure 1(b), and will not be repeated here.
  • the main difference between Figure 1(b) and Figure 1(a) is that the interface between each control plane network element in Figure 1(a) is a service interface, and each control plane network element in Figure 1(b) The interface between them is a point-to-point interface.
  • N1, N2, N3, N4 and N6 interfaces can refer to the foregoing description.
  • N5 the interface between the AF network element and the PCF network element, which can be used for sending application service requests and reporting network events.
  • N7 the interface between the PCF network element and the SMF network element, which can be used to deliver protocol data unit (protocol data unit, PDU) session granularity and service data flow granularity control policy.
  • protocol data unit protocol data unit
  • PDU protocol data unit
  • N8 The interface between the AMF network element and the UDM network element, which can be used for the AMF network element to obtain access and mobility management-related subscription data and authentication data from the UDM network element, and for the AMF network element to register with the UDM network element Terminal equipment mobility management related information, etc.
  • N9 UPF network element and user plane interface between UPF network elements, used to transfer uplink and downlink user data flows between UPF network elements.
  • N10 The interface between the SMF network element and the UDM network element, which can be used for the SMF network element to obtain session management-related contract data from the UDM network element, and for the SMF network element to register terminal device session-related information with the UDM network element.
  • N11 The interface between the SMF network element and the AMF network element, which can be used to transfer the PDU session tunnel information between the access network device and the UPF, transfer the control message sent to the terminal device, and send it to the access network The radio resource control information of the device, etc.
  • N15 the interface between the PCF network element and the AMF network element, which can be used to issue terminal equipment policies and access control related policies.
  • N35 the interface between the UDM network element and the UDR network element, which can be used for the UDM network element to obtain user subscription data information from the UDR network element.
  • N36 the interface between the PCF network element and the UDR network element, which can be used for the PCF network element to obtain policy-related subscription data and application data-related information from the UDR network element.
  • the above-mentioned network element or function may be a network element in a hardware device, or a software function running on dedicated hardware, or a virtualization function instantiated on a platform (for example, a cloud platform).
  • a platform for example, a cloud platform.
  • the foregoing network element or function may be implemented by one device, or jointly implemented by multiple devices, or may be a functional module in one device, which is not specifically limited in this embodiment of the present application.
  • the user plane network element, mobility management network element, and session management network element in this application can be the UPF network element, AMF network element, and SMF network element in the 5G system, or they can be future communications such as 6G networks with the above UPF
  • the function of the network element, the AMF network element, and the SMF network element is not limited in this application.
  • a UPF network element, an AMF network element, and an SMF network element are respectively used as an example of a user plane network element, a mobility management network element, and a session management network element for description.
  • the UPF network element, the AMF network element, and the SMF network element are respectively referred to as UPF, AMF, and SMF for short.
  • a base station such as a 4G eNB, a 5G gNB, or a base station in future communications
  • the subsequent "base station” can be replaced with " access network equipment”.
  • UE is used as an example of a terminal device for description, and "UE" that appears subsequently may be replaced with "terminal device”.
  • the Nx tunnel information of the UPF or the first tunnel information of the UPF refers to the tunnel information used for other UPFs to send data to the UPF.
  • UPF2 can send data to UPF1 according to the Nx tunnel information of UPF1.
  • the Nx tunnel information of UPF can also be called the tunnel information of UPF, or have other names, such as the N19 tunnel information called UPF in a 5G local area network (local area network, LAN), which is not limited .
  • the N3 tunnel information of the UPF or the second tunnel information of the UPF refers to the tunnel information used by the base station to send data to the UPF.
  • the base station may send data to UPF1 according to the N3 tunnel information of UPF1.
  • the N3 tunnel information of the UPF may also be called the tunnel information of the UPF, or have other names, which are not limited.
  • the N3 tunnel information of the base station or the tunnel information of the base station refers to the tunnel information used for the UPF to send data to the base station.
  • the UPF may send data to the base station 1 according to the N3 tunnel information of the base station 1.
  • the N3 tunnel information of the base station may also be referred to as tunnel information of the base station, or have other names, which are not limited.
  • 3GPP R17 proposes deploying base stations on satellites. According to the existing architecture, only the base station is deployed on the satellite, and the UPF, the anchor point of the session, is still deployed on the ground.
  • FIG. 2 it is a schematic diagram of a communication path between UEs.
  • the communication path between UE1 and UE2 is: UE1 -> satellite base station 1 of UE1 -> ground UPF1 of UE1 -> ground UPF2 of UE2 -> satellite base station 2 of UE2 -> UE2.
  • This path includes four segments of space-to-ground communication (also known as satellite-to-ground communication), specifically: 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 feeder circuit between the satellite and the ground station, and the ground link between the ground station and the UPF.
  • the 4G air interface, 5G air interface or air interface in future communication is between the UE and the satellite base station.
  • FIG. 3 it is a schematic diagram of a communication path between UEs.
  • the communication path between UE1 and UE2 is: UE1 -> UE1 satellite base station 1 -> UE1 satellite UPF1 -> UE2 satellite UPF2 -> UE2 satellite base station 2 -> UE2.
  • the path includes two segments of satellite-ground communication, specifically: 1) UE1 -> UE1's satellite base station 1; 2) UE2's satellite base station 2 -> UE2.
  • an Nx tunnel can be established between UE1’s satellite UPF and UE2’s satellite UPF for use between UE1 and UE2’s satellites Data is forwarded, so that the IP address of the UE may not be exposed on the interface of the inter-satellite link, and the underlying routing module of the inter-satellite link only sees the IP address of the satellite UPF, but not the IP address of the UE.
  • Nx tunnel may be an N19 tunnel
  • GTP-U GPRS Tunneling Protocol User Plane
  • GPRS refers to general packet radio service (general packet radio service).
  • the satellite base station and the satellite UPF serving the UE can be located on the same satellite, so UPF1 is located on the same satellite as base station 1, UPF2 is located on the same satellite as base station 2, and UPF1 is located on the same satellite.
  • An Nx tunnel is established with UPF2 so that UPF1 and UPF2 do not need to deal with routing based on UE IP addresses when UPF1 and UPF2 forward data packets for communication between UE1 and UE2, reducing the complexity of inter-satellite routing.
  • UPF1 of UE1 and UPF2 of UE2 may be controlled by different SMFs, or may be controlled by the same SMF.
  • Fig. 4 shows the situation that UPF1 and UPF2 are respectively controlled by different SMFs.
  • the switching of the satellite means that the satellite base station serving the UE and the satellite UPF change at the same time.
  • FIG. 5 it is a schematic flowchart of a handover method provided by an embodiment of the present application.
  • the satellite of UE1 is handed over.
  • the source base station 1 and the source UPF1 on satellite 1 provide services for UE1.
  • the target base station 1 and target UPF1 on satellite 2 provide services for UE1.
  • the satellite of UE2 does not switch over, and it is the base station 2 and UPF2 on the satellite 3 that serve the UE2.
  • the process includes the following steps:
  • Step 501 the source base station 1 sends a handover request message to the target base station 1 .
  • the target base station 1 receives the handover request message.
  • the handover request message includes the N3 tunnel information of the source UPF1, so as 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.
  • Step 502 the target base station 1 sends a handover response message to the source base station 1 .
  • the source base station 1 receives the handover response message.
  • the handover response message includes radio resource information allocated by target base station 1 to UE1.
  • Step 503 source base station 1 sends an RRC reconfiguration message to UE1.
  • UE1 receives the RRC reconfiguration message.
  • the RRC reconfiguration message includes radio resource information allocated by target base station 1 for UE1.
  • the source base station 1 may stop sending downlink data to the UE1, and start to send the received downlink data to the UE1 to the target base station 1 through the forwarding tunnel between the source base station 1 and the target base station 1 .
  • Step 504 UE1 and target base station 1 perform synchronization.
  • UE1 performs wireless synchronization with target base station 1 according to the radio resource information allocated for UE1.
  • Step 505 UE1 sends an RRC reconfiguration complete message to target base station 1.
  • the target base station 1 receives the RRC reconfiguration complete message.
  • UE1 can send uplink data to target base station 1, and target base station 1 sends the uplink data received from UE1 to source UPF1, and then source UPF1 sends UE1 to UPF2 according to the Nx tunnel information of UPF2. uplink data.
  • UPF2 sends the downlink data of UE1 to the source UPF1
  • the source UPF1 sends the downlink data of UE1 to the source base station 1
  • the source base station 1 passes through the forwarding tunnel between the source base station 1 and the target base station 1, and transmits the downlink data of UE1
  • the data is sent to the target base station 1, and the target base station 1 sends the downlink data of UE1 to UE1.
  • Step 506 the target base station 1 sends a path switching request message (PATH SWITCH REQUEST) to the AMF.
  • the AMF receives the path switching request message.
  • the path switching request message includes the N3 tunnel information of the target base station 1 .
  • step 507 the AMF sends a session modification request message to the SMF.
  • the SMF receives the session modification request message.
  • the session modification request message includes the N3 tunnel information of the target base station 1, and the session modification request message is used to notify the SMF that the UE1 has handover.
  • the session modification request message may be a Nsmf_PDUSession_SMContextUpdate Request message.
  • step 508a the SMF selects the target UPF1 deployed on the same satellite as the target base station 1 as the new UPF of UE1, and sends an N4 session modification request message to the target UPF1.
  • the target UPF1 receives the N4 session modification request message.
  • the N4 session modification message includes the N3 tunnel information of the target base station 1 and the Nx tunnel information of the UPF2.
  • step 508b the target UPF1 sends an N4 session modification response message to the SMF.
  • the SMF receives the N4 session modification response message.
  • the N4 session modification response message includes the N3 tunnel information of the target UPF1 and the Nx tunnel information of the target UPF1.
  • Step 509 the SMF sends a session modification response message to the AMF.
  • the AMF receives the session modification response message.
  • the session modification response message includes the N3 tunnel information of the target UPF1.
  • the session modification response message may be a Nsmf_PDUSession_SMContextUpdate Response message.
  • step 510 the AMF sends a path switching response message to the target base station 1.
  • the target base station 1 receives the path switch response message.
  • the path switching response message includes the N3 tunnel information of the target UPF1.
  • the target base station 1 directly sends the uplink data of the UE1 to the target UPF1, and the target UPF1 sends it to the UPF2.
  • the path switch response message may be a PATH SWITCH REQUEST ACK message.
  • step 511 the SMF sends an N4 session update request message to UPF2.
  • UPF2 receives the N4 session update request message.
  • the N4 session update request message includes an end marker (End Marker) indication and the Nx tunnel information of the target UPF1.
  • the End Marker indication is used to instruct UPF2 to send End Marker through the source path (that is, to the source UPF1).
  • UPF2 sends an End Marker to the source UPF1 according to the End Marker instruction.
  • the source UPF1 sends the End Marker to the source base station 1, and the source base station 1 forwards it to the target base station 1.
  • 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.
  • the target base station 1 temporarily buffers the downlink data of UE1 received from the target UPF1 before receiving the End Marker. After receiving the End Marker, the target base station 1 can send the data received from the target UPF1 to UE1.
  • UPF2 starts to send the downlink data packet sent to UE1 to target UPF1, and the target UPF1 sends it directly to target base station 1.
  • the out-of-sequence problem caused by the data received by the UE through the source path (source UPF1 ) arriving later than the data received through the target path (target UPF1 ) during the handover process can be avoided.
  • steps 506, 508a, 508b, 510, and 511 are all inter-satellite communication, which increases the satellite-ground communication signaling and makes the process time
  • the delay is long, and it is necessary to rely on inter-satellite forwarding to avoid packet loss, and there is detour between satellites, which not only increases the delay, but also increases the load on the inter-satellite link.
  • UPF2 of satellite 3 sends the downlink data of UE1 to source UPF1 of satellite 1, and source UPF1 sends the downlink data of UE1 to source base station 1 of satellite 1, and then Source base station 1 sends the downlink data of UE1 to target base station 1 of satellite 2, that is, UPF2 forwards the downlink data of UE1 to target base station 1 via source UPF1 and source base station 1. Since target base station 1 is connected with source UPF1 and source base station 1 is not on the same satellite, so the downlink data has an inter-satellite detour, that is, the data sent from satellite 3 to satellite 2 needs to be forwarded to satellite 2 via satellite 1.
  • UE1 sends the uplink data of UE1 to the target base station 1 of satellite 2, and 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 For UPF2 for satellite 3, since the source UPF1 and target base station 1 are not on the same satellite, the uplink data also has inter-satellite detour, that is, the data sent from satellite 2 to satellite 3 needs to be forwarded to satellite 3 via satellite 1.
  • the embodiment of the present application will subsequently optimize the handover process shown in FIG. 5 , so as to reduce the signaling between satellites and the ground during the handover process and reduce the detour of data between satellites.
  • FIG. 6 it is a schematic flowchart of a handover method provided by an embodiment of the present application.
  • the satellite of UE1 is handed over.
  • the source base station 1 and the source UPF1 on satellite 1 provide services for UE1.
  • the target base station 1 and target UPF1 on satellite 2 provide services for UE1.
  • the satellite of UE2 is also handed over.
  • the source base station 2 and the source UPF2 on the satellite 3 provide services for UE2.
  • the target base station 2 and the target UPF2 on the satellite 4 provide services for UE2.
  • the step description of the handover process of UE1 can refer to FIG. 5 .
  • the difference between the handover process in FIG. 6 and the handover process in FIG. 5 is that UE2 also undergoes handover during the handover process of UE1, wherein the handover process of UE2 is similar to the handover process of UE1. Therefore, at any moment of the handover process of UE1, the SMF may receive the Nx tunnel information of the target UPF2 of UE2. Similarly, at any moment during the handover process of UE2, the SMF may also receive the Nx tunnel information of the target UPF1 of UE1.
  • step 608a SMF will The Nx tunnel information of the source UPF2 of UE2 is sent to the target UPF1 of UE1. If the SMF receives the Nx tunnel information of the target UPF2 of UE2 after step 608a, the target UPF1 of UE1 will not be able to obtain the Nx tunnel information of the target UPF2 of UE2. The data of the target UPF1 is still sent to the source UPF2 of UE2.
  • End Marker can be understood as the last packet sent to the source UPF2.
  • the embodiment of the present application will optimize the handover process shown in FIG. 6 above, so as to avoid as much as possible the problem of packet loss or out-of-sequence of data packets generated when UEs at both ends of the communication simultaneously perform inter-satellite handover.
  • Fig. 7(a) is a schematic flowchart of a handover method provided by an embodiment of the present application.
  • the satellite of UE1 is handed over.
  • the source base station 1 and the source UPF1 on satellite 1 provide services for UE1.
  • the target base station 1 and target UPF1 on satellite 2 provide services for UE1.
  • the satellite of UE2 does not switch over, and it is the base station 2 and UPF2 on the satellite 3 that serve the UE2.
  • the method includes the following steps:
  • Step 701a the source base station 1 sends a handover preparation request message to the source UPF1, and the handover preparation request message includes the identifier of the session of UE1.
  • the handover preparation request message is used to instruct the source UPF1 to prepare for the inter-satellite handover of UE1.
  • the embodiment of the present application does not limit the name of the handover preparation request message, and the message may also have other names.
  • Step 702a the source UPF1 sends a handover preparation response message to the source base station 1, and the handover preparation response message includes the Nx tunnel information of the UPF2 corresponding to the session.
  • the handover preparation response message is a response to the above handover preparation request message.
  • the Nx tunnel information of UPF2 is included in the context of the session of UE1, and the context of the session also includes at least one of the session endpoint identifier of the SMF, the packet detection rule corresponding to the session, and the identification information of the SMF, and the SMF
  • the session endpoint identifier of is used to identify the session in the SMF
  • the packet detection rule corresponding to the session is used for the target UPF1 to process the uplink data packet and/or downlink data packet of UE1.
  • the handover preparation response message also includes a packet detection rule corresponding to the LAN group, and the packet detection rule corresponding to the LAN group is used for processing by the target UPF1 and sent to the LAN group Data packets of other UEs except UE1.
  • step 703a the source base station 1 sends the Nx tunnel information of UPF2 to the target base station 1 .
  • step 703a is specifically: the source base station 1 sends the session context of UE1 to the target base station 1 .
  • the target base station 1 also sends to the source base station 1 the radio resource information allocated by the target base station 1 for the session of UE1, so that the source base station 1 sends the radio resource information to UE1, so that UE1 , establish an air interface connection with the target base station 1, and implement handover of the UE1 from the source base station 1 to the target base station 1.
  • 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 tunnel information of UE1 to the target base station 1 according to the forwarding tunnel information. data.
  • step 704a the target base station 1 sends the Nx tunnel information of UPF2 to the target UPF1.
  • UPF2 is a UPF corresponding to the session of UE2 communicating with UE1.
  • the Nx tunnel information of the UPF2 is used for the target UPF1 to send the downlink data of the UE2 to the UPF2.
  • the downlink data of UE2 refers to the data sent to UE2.
  • step 704a specifically includes: the target base station 1 sends the session context of UE1 to the target UPF1.
  • the target base station 1 also sends the N3 tunnel information of the target base station 1 to the target UPF1, and the N3 tunnel information of the target base station 1 is used for the target UPF1 to send the downlink data of the UE1 to the target base station 1.
  • the downlink data of UE1 refers to the data sent to UE1.
  • Step 705a the target UPF1 sends to the target base station 1 information indicating that the UPF of UE1 is switched, and the information includes the Nx tunnel information of the target UPF1.
  • the Nx tunnel information of the target UPF1 is allocated by the target UPF1.
  • the Nx tunnel information of the target UPF1 is used for the UPF2 to send the downlink data of the UE1 to the target UPF1.
  • the information indicating that the UPF of UE1 is switched also includes the session endpoint identifier of the target UPF1, and the session endpoint identifier of the target UPF1 is used to identify the session in the target UPF1.
  • the session endpoint identifier of the target UPF1 is allocated for the session by the target UPF1.
  • the information indicating that the UPF of UE1 is switched is contained in an N4 container and sent to the target base station 1, and the target base station 1 does not perceive the contents of the N4 container.
  • the target UPF1 also sends the N3 tunnel information of the target UPF1 to the target base station 1, and the N3 tunnel information of the target UPF1 is used for the target base station 1 to send the uplink data of UE1 to the target UPF1.
  • the uplink data of UE1 refers to data sent by UE1.
  • step 706a the target base station 1 sends information indicating that the UPF of UE1 is switched to the SMF.
  • the target base station 1 sends a message indicating that UE1 is switching to the SMF or via the AMF to the SMF, and the message includes information indicating that the UPF of UE1 is switched.
  • the SMF can perceive the content in the N4 container.
  • step 707a the SMF sends the Nx tunnel information of the target UPF1 to UPF2, so as to update the UPF information of UE1 in UPF2.
  • UPF Nx tunnel information of the UE1 is not stored in the UPF2
  • "updating the UPF information of the UE1 in the UPF2" here refers to storing the UPF Nx tunnel information of the UE1 in the UPF2. If the UPF Nx tunnel information of UE1 has been stored in UPF2, the "update UPF information of UE1 in UPF2" here refers to replacing the UPF Nx tunnel information of UE2 currently stored in UPF2 with the newly received Nx tunnel information of target UPF1.
  • the Nx tunnel information of the target UPF1 is used for the UPF2 to send the downlink data of the UE1 to the target UPF1.
  • the downlink data of UE1 refers to the data sent to UE1.
  • the SMF of UE1 sends the Nx tunnel information of the target UPF1 to UPF2 through the SMF of UE2.
  • the SMF also sends an End Marker indication to UPF2, where the End Marker indication is used to instruct UPF2 to send an End Marker to the source UPF1. If the SMF of UE1 is different from the SMF of UE2, 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.
  • the source UPF when UE1 is handed over, sends the context information of the source UPF session (including the Nx tunnel information of UE2’s UPF) to the target UPF in the preparation stage before the handover, so as to avoid sending UE2’s session information to the target UPF by the SMF.
  • the Nx tunnel information of the UPF can reduce the satellite-ground interaction between the SMF and the target UPF, thereby reducing data transmission delay and handover delay.
  • FIG. 7(b) is a schematic flowchart of a handover method provided by an embodiment of the present application.
  • This embodiment can be applied to a scenario where UE1 and UE2 are handed over across satellites at the same time (for example, this scenario occurs due to satellite movement).
  • the satellite of UE1 is handed over.
  • the source base station 1 and the source UPF1 on satellite 1 provide services for UE1.
  • the target base station 1 and target UPF1 on satellite 2 provide services for UE1.
  • the satellite of UE2 is also handed over.
  • the source base station 2 and the source UPF2 on the satellite 3 provide services for UE2.
  • the target base station 2 and the target UPF2 on the satellite 4 provide services for UE2.
  • the method includes the following steps:
  • step 701b the source base station 1 sends a handover preparation request message to the source UPF1, and the handover preparation request message includes the identifier of the session of UE1.
  • step 702b the source UPF1 sends a handover preparation response message to the source base station 1, and the handover preparation response message includes the Nx tunnel information of the source UPF2 corresponding to the session.
  • the Nx tunnel information of the source UPF2 is included in the context of the session of UE1, and the context of the session also includes at least one of the session endpoint identifier of the SMF, the packet detection rule corresponding to the session, and the identifier information of the SMF,
  • the session endpoint identifier of the SMF is used to identify the session in the SMF
  • the packet detection rule corresponding to the session is used for the target UPF1 to process the uplink data packet and/or downlink data packet of the UE1.
  • the handover preparation response message also includes a packet detection rule corresponding to the LAN group, and the packet detection rule corresponding to the LAN group is used for processing by the target UPF1 and sent to the LAN group Data packets of other UEs except UE1.
  • step 703b the source base station 1 sends the Nx tunnel information of the source UPF2 to the target base station 1 .
  • the step 703b is specifically: the source base station 1 sends the session context of the UE1 to the target base station 1 .
  • the target base station 1 also sends to the source base station 1 the radio resource information allocated by the target base station 1 for the session of UE1, so that the source base station 1 sends the radio resource information to UE1, so that UE1 , establish an air interface connection with the target base station 1, and implement handover of the UE1 from the source base station 1 to the target base station 1.
  • 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 tunnel information of UE1 to the target base station 1 according to the forwarding tunnel information. data.
  • step 704b the target base station 1 sends the Nx tunnel information of the source UPF2 to the target UPF1.
  • the source UPF2 is the UPF corresponding to the session of UE2 communicating with UE1.
  • the Nx tunnel information of the source UPF2 is used for the target UPF1 to send the downlink data of the UE2 to the source UPF2.
  • the downlink data of UE2 refers to the data sent to UE2.
  • step 704b specifically includes: the target base station 1 sends the session context of the UE1 to the target UPF1.
  • the target base station 1 also sends the N3 tunnel information of the target base station 1 to the target UPF1, and the N3 tunnel information of the target base station 1 is used for the target UPF1 to send the downlink data of the UE1 to the target base station 1.
  • the downlink data of UE1 refers to the data sent to UE1.
  • the target UPF1 sends to the target base station 1 information indicating that the UPF of UE1 is switched, and the information includes the Nx tunnel information of the target UPF1.
  • the Nx tunnel information of the target UPF1 is allocated by the target UPF1.
  • the Nx tunnel information of the target UPF1 is used by the UPF of the UE2 to send the downlink data of the UE1 to the target UPF1.
  • the information indicating that the UPF of UE1 is switched also includes the session endpoint identifier of the target UPF1, and the session endpoint identifier of the target UPF1 is used to identify the session in the target UPF1.
  • the session endpoint identifier of the target UPF1 is allocated for the session by the target UPF1.
  • the information indicating that the UPF of UE1 is switched is contained in an N4 container and sent to the target base station 1, and the target base station 1 does not perceive the contents of the N4 container.
  • the target UPF1 also sends the N3 tunnel information of the target UPF1 to the target base station 1, and the N3 tunnel information of the target UPF1 is used for the target base station 1 to send the uplink data of the UE1 to the target UPF1.
  • the uplink data of UE1 refers to data sent by UE1.
  • Step 706b the SMF receives the Nx tunnel information of the target UPF2 from the target UPF2 through the target base station 2.
  • UE2 is also handover, and UE2 handover is earlier than UE1 handover, so before step 709b, the SMF has received the Nx tunnel information of the target UPF2 from the target UPF2.
  • step 707b 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.
  • step 708b the source UPF1 sends a response message rejecting the update to the SMF.
  • the SMF When the SMF receives the Nx tunnel information of the target UPF2 from the target UPF2, it does not know that UE1 is also switching, so 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. But the source UPF1 knows that UE1 is handing over, so the source UPF1 refuses to update, that is, sends a response message of rejecting update to the SMF, so as to refuse to update the UPF information of UE2 in the source UPF1.
  • the update rejection response message carries a rejection reason value, and the rejection reason value is that UE1 is handing over.
  • step 709b the target base station 1 sends information indicating that the UPF of UE1 is switched to the SMF.
  • the SMF can perceive the content in the N4 container.
  • this step 709b specifically includes: the target base station 1 sends information indicating that UPF of UE1 is switched to AMF, and then AMF sends a session modification request to SMF, and the session modification request includes information indicating that UPF of UE1 is switched.
  • the SMF knows that UE1 has completed the handover and that the UPF after the handover is the target UPF1, so the following step 710b can be performed.
  • step 710b the SMF sends the Nx tunnel information of the target UPF2 to the target UPF1.
  • the SMF may send an End Marker indication to the target UPF1, and the target UPF1 sends an End Marker to the source UPF2 according to the End Marker indication.
  • the SMF knows that the UE1 has completed the handover and that the UPF after the handover is the target UPF1, so the following step 711b can be performed, which has no sequence relationship with the above step 710b.
  • step 711b the SMF sends the Nx tunnel information of the target UPF1 to the target UPF2.
  • the SMF sends an End Marker indication to the target UPF2, and the target UPF2 sends an End Marker to the source UPF1 according to the End Marker indication.
  • SMF receives the updated Nx tunnel information of the target UPF2 from UE2, and does not know that UE1 is switching, then the SMF sends the Nx tunnel information of the target UPF2 to the source UPF1 of UE1
  • the SMF receives the response message of rejecting the update from the source UPF2, it knows that UE1 is switching, and then the SMF receives the information indicating that the UPF of UE1 is switching, and then sends the update of UE2 to the target UPF1 of UE1 after switching.
  • the Nx tunnel information of the target UPF2 thus ensuring the normal completion of the handover.
  • Fig. 7(c) is a schematic flowchart of a handover method provided by the embodiment of the present application.
  • This embodiment can be applied to a scenario where UE1 and UE2 are handed over across satellites at the same time (for example, this scenario occurs due to satellite movement).
  • the satellite of UE1 is handed over.
  • the source base station 1 and the source UPF1 on satellite 1 provide services for UE1.
  • the target base station 1 and target UPF1 on satellite 2 provide services for UE1.
  • the satellite of UE2 is also handed over.
  • the source base station 2 and the source UPF2 on the satellite 3 provide services for UE2.
  • the target base station 2 and the target UPF2 on the satellite 4 provide services for UE2.
  • the method includes the following steps:
  • Step 701c to step 705c are the same as the above step 701b to step 705b, and reference may be made to the foregoing description.
  • step 706c the target base station 1 sends information indicating that the UPF of UE1 is switched to the SMF.
  • the target base station 1 sends a message indicating that UE1 is switching to the SMF or via the AMF to the SMF, and the message includes information indicating that the UPF of UE1 is switched.
  • the SMF can perceive the content in the N4 container.
  • Step 707c the SMF receives the Nx tunnel information of the target UPF2 from the target UPF2 through the target base station 2.
  • the SMF When the SMF receives the Nx tunnel information of the target UPF2 from the target UPF2, it has learned through the above step 706c that UE1 is also switching, and knows that the UPF after UE1 switching is the target UPF1, so the SMF sends the Nx tunnel information of the target UPF2 to the target UPF1 , that is, perform the following step 708c.
  • step 708c the SMF sends the Nx tunnel information of the target UPF2 to the target UPF1.
  • the SMF sends an End Marker indication to the target UPF1, and the target UPF1 sends an End Marker to the source UPF2 according to the End Marker indication.
  • step 707c the following step 709c is also performed, and this step 709c has no sequence relationship with the above step 708c.
  • step 709c the SMF sends the Nx tunnel information of the target UPF1 to the target UPF2.
  • the SMF sends an End Marker indication to the target UPF2, and the target UPF2 sends an End Marker to the source UPF1 according to the End Marker indication.
  • SMF when UE1 and UE2 switch simultaneously, SMF receives the Nx tunnel information of UE2’s updated target UPF2, and has learned the information of UE1’s target UPF1 after switching, then SMF sends target UPF1 to UE1’s target UPF1.
  • the Nx tunnel information of UPF2 thus ensuring the normal completion of the handover.
  • FIG. 7( d ) is a schematic flowchart of a handover method provided by an embodiment of the present application.
  • This embodiment can be applied to a scenario where UE1 and UE2 are handed over across satellites at the same time (for example, this scenario occurs due to satellite movement).
  • the satellite of UE1 is handed over.
  • the source base station 1 and the source UPF1 on satellite 1 provide services for UE1.
  • the target base station 1 and target UPF1 on satellite 2 provide services for UE1.
  • the satellite of UE2 is also handed over.
  • the source base station 2 and the source UPF2 on the satellite 3 provide services for UE2.
  • the target base station 2 and the target UPF2 on the satellite 4 provide services for UE2.
  • the method includes the following steps:
  • Step 701d to step 705d are the same as the above step 701b to step 705b, and reference may be made to the foregoing description.
  • Step 706d the SMF receives the Nx tunnel information of the target UPF2 from the target UPF2 through the target base station 2.
  • UE2 is also undergoing handover, and UE2 handover is earlier than UE1 handover, so after step 705d, the SMF has received the Nx tunnel information of the target UPF2 from the target UPF2.
  • 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.
  • the SMF When the SMF receives the Nx tunnel information of the target UPF2 from the target UPF2, it does not know that UE1 is also switching, so 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.
  • the SMF sends an End Marker indication to the source UPF2, and the End Marker indication is used to instruct the source UPF2 to send an End Marker to the source base station 2.
  • the source UPF2 sends the End Marker to the source base station 2.
  • step 708d the target base station 1 sends information indicating that the UPF of UE1 is switched to the SMF.
  • the SMF can perceive the content in the N4 container.
  • this step 708d specifically includes: the target base station 1 sends information indicating that UPF of UE1 is switched to AMF, and then AMF sends a session modification request to SMF, and the session modification request includes information indicating that UPF of UE1 is switched.
  • step 709d the SMF sends the Nx tunnel information of the target UPF2 to the target UPF1.
  • the SMF also receives the Nx tunnel information of the UPF of UE2 sent by the target UPF1 through the above steps 705d and 708d, wherein the target UPF1 is the Nx tunnel information of the UPF of the UE2 received from the source UPF1, then
  • This step 709d is specifically: the SMF determines that if the Nx tunnel information of the UPF of the UE2 from the target UPF1 is different from the Nx tunnel information of the UPF of the UE2 saved by the SMF, then the SMF sends the Nx tunnel information of the target UPF2 to the target UPF1.
  • the Nx tunnel information of UPF of UE2 from target UPF1 is the Nx tunnel information of source UPF2
  • the Nx tunnel information of UPF of UE2 saved by SMF is the Nx tunnel information of target UPF2
  • SMF determines the UPF of UE2 from target UPF1
  • the Nx tunnel information is different from the Nx tunnel information of the UE2's UPF saved by the SMF, and then the SMF sends the Nx tunnel information of the target UPF2 to the target UPF1.
  • the SMF knows that the UE1 has completed the handover and that the UPF after the handover is the target UPF1, so the following step 710d can be performed, which has no sequence relationship with the above step 709d.
  • step 710d the SMF sends the Nx tunnel information of the target UPF1 to the target UPF2.
  • the SMF sends an End Marker indication to the source UPF1, where the End Marker indication is used to instruct the source UPF1 to send an End Marker to the source base station 1.
  • the source UPF1 sends the End Marker to the source base station 1 according to the End Marker instruction.
  • SMF when UE1 and UE2 are switched at the same time, SMF receives the updated Nx tunnel information of the target UPF2 from UE2, and does not know that UE1 is switching, then the SMF 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 the downlink data of UE2 to the target UPF2 instead of sending the downlink data of UE2 to the source UPF2. After receiving the information indicating that the UPF of UE1 is switched, the SMF sends the Nx tunnel information of the updated target UPF2 of UE2 to the switched target UPF1 of UE1, thereby ensuring the normal completion of the switch.
  • FIG. 7( e ) is a schematic flowchart of a handover method provided by an embodiment of the present application.
  • This embodiment can be applied to a scenario where UE1 and UE2 are handed over across satellites at the same time (for example, this scenario occurs due to satellite movement).
  • the satellite of UE1 is handed over.
  • the source base station 1 and the source UPF1 on satellite 1 provide services for UE1.
  • the target base station 1 and target UPF1 on satellite 2 provide services for UE1.
  • the satellite of UE2 is also handed over.
  • the source base station 2 and the source UPF2 on the satellite 3 provide services for UE2.
  • the target base station 2 and the target UPF2 on the satellite 4 provide services for UE2.
  • the method includes the following steps:
  • Step 701e to step 705e are the same as the above step 701b to step 705b, and reference may be made to the foregoing description.
  • step 706e the target base station 1 sends information indicating that the UPF of UE1 is switched to the SMF.
  • the target base station 1 sends a message indicating that UE1 is switching to the SMF or via the AMF to the SMF, and the message includes information indicating that the UPF of UE1 is switched.
  • the SMF can perceive the content in the N4 container.
  • Step 707e the SMF receives the Nx tunnel information of the target UPF2 from the target UPF2 through the target base station 2.
  • the SMF When the SMF receives the Nx tunnel information of the target UPF2 from the target UPF2, it has learned through the above step 706e that UE1 is also switching, and knows that the UPF after UE1 switching is the target UPF1, so the SMF sends the Nx tunnel information of the target UPF2 to the target UPF1 , that is, perform the following step 708e. And the following step 709e is also executed, and there is no time sequence limitation between step 708e and step 709e.
  • step 708e the SMF sends the Nx tunnel information of the target UPF2 to the target UPF1.
  • step 709e the SMF sends the Nx tunnel information of the target UPF2 to the source UPF1.
  • the SMF sends an End Marker indication to the source UPF2, where the End Marker indication is used to instruct the source UPF2 to send an End Marker to the source base station 2.
  • the source UPF2 sends the End Marker to the source base station 2 according to the End Marker instruction.
  • step 706e the following step 710e is also performed, and there is no sequence relationship between this step 710e and the above-mentioned step 708e and step 709e.
  • step 710e the SMF sends the Nx tunnel information of the target UPF1 to the target UPF2.
  • the SMF sends an End Marker indication to the source UPF1, where the End Marker indication is used to instruct the source UPF1 to send an End Marker to the source base station 1.
  • the source UPF1 sends the End Marker to the source base station 1 according to the End Marker instruction.
  • SMF when UE1 and UE2 switch simultaneously, SMF receives the Nx tunnel information of UE2's updated target UPF2, and has learned the information of UE1's target UPF1 after switching, then SMF sends UE1's target UPF1 and source UPF1 sends the Nx tunnel information of the target UPF2 to ensure the normal completion of the handover.
  • FIG. 7(f) is a schematic flowchart of a handover method provided by an embodiment of the present application.
  • This embodiment can be applied to a scenario where UE1 and UE2 are handed over across satellites at the same time (for example, this scenario occurs due to satellite movement).
  • the satellite of UE1 is handed over.
  • the source base station 1 and the source UPF1 on satellite 1 provide services for UE1.
  • the target base station 1 and target UPF1 on satellite 2 provide services for UE1.
  • the satellite of UE2 is also handed over.
  • the source base station 2 and the source UPF2 on the satellite 3 provide services for UE2.
  • the target base station 2 and the target UPF2 on the satellite 4 provide services for UE2.
  • the method includes the following steps:
  • step 701f the SMF receives the Nx tunnel information of the target UPF2 from the target UPF2.
  • the target UPF2 may be the switched target UPF selected by the SMF for UE2.
  • the SMF may receive the Nx tunnel information of the target UPF2 from the target UPF2.
  • the SMF receives information indicating that UE2 is handovered, and then the SMF sends the Nx tunnel information of the source UPF1 to the target UPF2.
  • step 702f the SMF receives information indicating that UE1 is handovered.
  • the SMF determines that the UE1 is being handed over according to the information indicating that the UE1 is handed over.
  • the information instructing UE1 to switch may be information for selecting a UPF for UE1, or the identification information of the target UPF1.
  • the information indicating UE1 handover may be included in the session modification request message and sent to the SMF, and the SMF acquires the information indicating UE1 handover from the session modification request message.
  • step 701f there is no sequential execution sequence between the above step 701f and step 702f.
  • step 703f the SMF sends the Nx tunnel information of the target UPF2 to the source UPF1, so as to update the UPF information of UE2 in the source UPF1.
  • SMF When SMF receives the Nx tunnel information of UE2's target UPF2, UE1 is also switching and the handover has not been completed, then SMF first sends the Nx tunnel information of UE2's target UPF2 to UE1's source UPF1 to update UE1's source UPF1 UPF information of UE2 in .
  • the SMF also sends an end marker indication to the source UPF1, where the end marker indication is used to instruct the source UPF1 to send an end marker to the source UPF2.
  • step 704f the SMF sends the Nx tunnel information of the target UPF2 to the target UPF1.
  • the SMF may send the N3 tunnel information of the target UPF1 to the target base station 1 . Therefore, the target base station 1 can send data to the target UPF1 according to the N3 tunnel information of the target UPF1.
  • FIG. 8 it is a schematic flowchart of a handover method provided by an embodiment of the present application.
  • the satellite of UE1 is handed over.
  • the source base station 1 and the source UPF1 on the satellite 1 provide services for UE1.
  • the target base station 1 and the target UPF1 on the satellite 2 provide services for UE1.
  • the satellite of UE2 does not switch over, and it is the base station 2 and UPF2 on the satellite 3 that serve the UE2.
  • the embodiment of FIG. 8 is an improvement to the embodiment of FIG. 5 described above.
  • the embodiment corresponding to FIG. 8 is also a specific implementation of the embodiment in FIG. 7(a) above.
  • the process includes the following steps:
  • Step 801 UE1 is about to move out of the coverage of source base station 1, and source base station 1 decides to handover UE1 to target base station 1, then source base station 1 sends a handover preparation request message to source UPF1. Correspondingly, the source UPF1 receives the handover preparation request message.
  • the handover preparation request message is used to instruct the source UPF1 to prepare for the inter-satellite handover of UE1.
  • this step 801 is performed once, and the handover preparation request message includes the identifier of the PDU session.
  • step 801 may be performed once or multiple times. That is, the source base station 1 may send a handover preparation request message to the source UPF1 for each PDU session, and the handover preparation request message includes an identifier of a PDU session. Alternatively, the source base station 1 sends a handover preparation request message for the multiple PDU sessions of the UE, where the handover preparation request message includes identifiers of the multiple PDU sessions of the UE1. That is, the handover preparation request message may be at UE granularity, or at the PDU session granularity.
  • Step 802 the source UPF1 sends a handover preparation response message to the source base station 1.
  • the source base station 1 receives the handover preparation response message.
  • the handover preparation response message includes context information of the PDU session of UE1 in the source UPF1.
  • the source base station 1 sends a handover preparation request message for each PDU session
  • the source UPF1 sends a handover preparation response message for each handover preparation request message
  • the handover preparation response message includes context information of a PDU session.
  • the source base station 1 sends the handover preparation request message 1 to the source UPF1, which includes the identifier of the PDU session 1, and sends the handover preparation request message 2 to the source UPF1, which includes the identifier of the PDU session 2, then the source UPF1 sends a message to the source base station 1 Send the handover preparation response message 1 for the handover preparation request message 1, which includes the context information of the PDU session 1, and send the handover preparation response message 2 for the handover preparation request message 2, which includes the context information of the PDU session 2, to the source base station 1 information.
  • source base station 1 sends a handover preparation request message for multiple PDU sessions of UE1
  • source UPF1 sends a handover preparation response message to source base station 1
  • the handover preparation response message includes context information of multiple PDU sessions of UE1.
  • each PDU session corresponds to context information of a PDU session.
  • the context information of each PDU session includes the identifier of the PDU session and all packet detection rules (Packet Detection Rule, PDR) corresponding to the PDU session.
  • PDR Packet Detection Rule
  • the PDR includes an uplink PDR and a downlink PDR
  • the uplink PDR is used to determine the transmission mode of the received uplink data packet
  • the downlink PDR is used to determine the transmission mode of the received downlink data packet.
  • the uplink PDR includes the Nx tunnel information of UPF2, or when the PDU session is a 5G local area network (Local Area Network, LAN) session, the uplink PDR indicates that the received uplink data packet is sent to the 5G LAN internal interface.
  • LAN Local Area Network
  • the downlink PDR includes the information of the QoS flow corresponding to the PDU session (for example, QoS flow identity (QoS flow identity, QFI) and QoS flow description information (for the target UPF to determine the QFI corresponding to the downlink data packet)).
  • QoS flow identity QoS flow identity, QFI
  • QoS flow description information for the target UPF to determine the QFI corresponding to the downlink data packet
  • the source interface (Source Interface) of the downlink PDR of the PDU session is the 5G LAN internal interface
  • the source network instance (Network Instance) of the PDR is set to the identifier of the 5G LAN
  • the uplink of the PDU session The destination interface (Destination Interface) of the PDR is the internal interface of the 5G LAN
  • the destination network instance (Network Instance) of the PDR in the uplink direction is set to the identity of the 5G LAN, that is, the uplink data packet received from the PDU session is sent to the 5G LAN
  • the internal interface of the LAN is set to the identity of the 5G LAN.
  • the handover preparation response message also includes the context information of the 5G LAN session
  • the context information of the 5G LAN session includes the uplink PDR at the 5G LAN group level
  • the source network instance (Network Instance) of the uplink PDR is set as the identifier of the 5G LAN
  • the PDR includes address information
  • the PDR is used to set the destination address to the one included in the PDR
  • the data packet of the address is sent to UPF2 through the Nx tunnel.
  • the context information of the 5G LAN session also includes the downlink PDR at the 5G LAN group level, the destination interface of the downlink PDR is the 5G LAN internal interface (VN Internal), and the destination network instance (Network Instance) of the downlink PDR Set as the identifier of the 5G LAN, the downlink PDR is used to indicate that the data packet received from the Nx tunnel is sent to the internal interface of the 5G LAN.
  • VN Internal 5G LAN internal interface
  • Network Instance Network Instance
  • the PDR of the PDU session and the PDR of the 5G LAN group level are used for the target UPF1 to process the uplink and downlink data packets.
  • the context information of the PDU session also includes: N4 session information, for example, the F-SEID of the SMF corresponding to the PDU session and/or the Node ID of the SMF.
  • N4 session information for example, 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 in the SMF
  • the F-SEID is an abbreviation of a Fully Qualified Session Endpoint Identifier (Fully Qualified Session Endpoint Identifier).
  • the source UPF1 can encapsulate the context information of each PDU session of the UE1 in a context container, and the source base station 1 does not need to understand the content in the container.
  • the handover preparation response message includes one or more (identification of the PDU session, context container corresponding to the PDU session).
  • Step 803 the source base station 1 sends a handover request message to the target base station 1 .
  • the target base station 1 receives the handover request message.
  • the switch request message includes the identifier of each PDU session and the context container corresponding to the PDU session, or it can be understood that the switch request message includes one or more (the identifier of the PDU session, the context container corresponding to the PDU session).
  • the (identification of the PDU session, the context container corresponding to the PDU session) here represents a combination of the identification of the PDU session and the context container corresponding to the PDU session, so one or more (identification of the PDU session, the corresponding context container of the PDU session Context container) represents one or more combinations, and each combination includes an identifier of a PDU session and a context container corresponding to the PDU session, which are uniformly described here and will not be repeated hereafter.
  • Step 804 the target base station 1 sends a handover preparation request message to the target UPF1 located on the same satellite.
  • the target UPF1 receives the handover preparation request message.
  • the handover preparation request message includes context information of the PDU session of UE1.
  • the handover preparation request message includes at least one identifier of the PDU session of UE1 and a context container corresponding to the PDU session.
  • the handover preparation request message also includes the N3 tunnel information of the target base station 1 corresponding to at least one PDU session of the UE1, and the N3 tunnel is used for the target base station 1 to receive the data of the PDU session. For example, if the target base station 1 determines that the context container corresponding to the PDU session is included in the received handover request message, the target base station 1 allocates an N3 tunnel information for the PDU session, and carries the identifier of the PDU session in the handover preparation request message, The context container of the PDU session and the N3 tunnel information of the target base station 1 corresponding to the PDU session.
  • the source base station 1 indicates which PDU sessions of the target base station 1 need to create N3 tunnels to the target UPF1 in the handover request message (the source base station 1 knows which PDU sessions are served by the source UPF1), and the target base station 1 allocates N3 for these PDU sessions tunnel, and carry 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 may include one or more (identification of the PDU session, context container, and N3 tunnel information of the target base station 1).
  • Step 805 the target UPF1 sends a handover preparation response message to the target base station 1 .
  • the target base station 1 receives the handover preparation response message.
  • the target UPF1 After receiving the handover preparation request message, the 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.
  • 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.
  • the format of the handover preparation response message is as follows: the handover preparation response message includes one or more (identification of the PDU session, N4 container, and N3 tunnel information of the target UPF1).
  • the N3 tunnel information of the target UPF1 is sent to the target base station 1, and the N4 container is sent to the SMF.
  • the target UPF1 allocates the N3 tunnel information of the target UPF1 for each PDU session, and the N3 tunnel information is used to receive the data of the PDU session from the target base station 1, and each PDU session allocates the N3 tunnel information of the target UPF1 to carry in the handover preparation
  • the response message is sent to the target base station 1.
  • the target base station 1 can receive the N3 tunnel information of the target UPF1 corresponding to each PDU session, thus in the target An N3 tunnel corresponding to each PDU session is established between the base station 1 and the target UPF1, and the N3 tunnel is used to transmit data of the PDU session.
  • the uplink data sent by UE1 can be directly sent to target UPF1 through the N3 tunnel, avoiding detour through source UPF1.
  • the N3 tunnel is a PDU session granularity, that is, each PDU corresponds to one N3 tunnel.
  • N4 message is encapsulated in the N4 container corresponding to each PDU session.
  • the N4 message may also be a PFCP session modification request message, and the PFCP session modification request message is generated by the target UPF1 for the PDU session to notify SMF: 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 (for example, the F-SEID of the SMF and/or the Node ID of the SMF, wherein the F-SEID of the SMF is used to uniquely identify the PDU session in the SMF) , the N4 interface information of the target UPF1 (for example, the F-SEID of the target UPF1 and/or the Node ID of the target UPF1, etc., wherein, the F-SEID of the target UPF1 is used to uniquely identify the session in the target UPF1) and include the target UPF1 as The Nx tunnel information of the target UPF1 assigned by the PDU session, the Nx tunnel information of the target UPF1 will be sent to UPF2, and used for UPF2 to send to the target UPF1 the data that UE2 needs to send to UE1 according to the Nx tunnel information of the target UPF1.
  • the N4 interface information of the target UPF1 for example, the F-SEID of the target UPF1 and
  • the PFCP session modification request message may also include N3 tunnel information of the target UPF1 corresponding to the PDU session.
  • the PFCP session modification request message may also include N3 tunnel information of the target base station 1 corresponding to the PDU session.
  • Step 806 the target base station 1 sends a handover response message to the source base station 1 .
  • the source base station 1 receives the handover response message.
  • the target base station 1 obtains the N3 tunnel information of the target UPF1 corresponding to each PDU session of the UE1 from the handover preparation response message in the above step 805, and saves the N3 tunnel information of the target UPF1.
  • the target base station 1 also sends a handover response message to the source base station 1, which includes the identifier of the PDU session of the UE1.
  • the handover response message may also include radio resource information allocated by the target base station 1 for each PDU session of UE1.
  • the handover response message may also include forwarding tunnel information of the target base station 1, and the forwarding tunnel information is used for the source base station 1 to forward the received data destined for the UE1 to the target base station 1.
  • the data sent from UE2 to UE1 can reach the target base station 1 through the forwarding tunnel of the target base station 1, and 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 established a connection with target base station 1 at this time, the data sent by UE2 to UE1 can be temporarily buffered in target base station 1. After the connection between target base station 1 and UE1 is subsequently established, target base station 1 The cached data can be sent to UE1.
  • Step 807 the source base station 1 sends a handover command to UE1.
  • UE1 receives the handover command.
  • the source base station 1 when the source base station 1 receives the handover response message in step 806, the source base station 1 is triggered to send a handover command to UE1.
  • the handover command may be an RRC reconfiguration message.
  • the handover command includes radio resource information allocated by target base station 1 for each PDU session of UE1, so that UE1 configures an air interface according to the radio resource information.
  • Step 808, UE1 synchronizes with target base station 1.
  • UE1 may send uplink data through target base station 1 . Since the N3 tunnel between the target base station 1 and the target UPF1 has been established in the handover preparation stage, the target base station 1 can send the uplink data of the UE1 received from the UE1 to the target UPF1. Moreover, since the context information of the PDU session obtained by the target UPF1 from the source UPF1 includes the Nx tunnel information of UPF2 of UE2, the target UPF1 can send the received uplink data of UE1 to UPF2, and UPF2 sends it to UE2. That is, after step 808, the uplink path has been switched.
  • Step 809 UE1 sends a handover completion indication to target base station 1.
  • the target base station 1 receives the handover completion indication.
  • the handover completion indication may be an RRC reconfiguration completion message.
  • the target base station 1 may start to send downlink data to UE1. For example, the target base station 1 may send to UE1 the previously buffered data that needs to be sent to the UE1, and the buffered data is sent by the source base station 1 to the target base station 1 .
  • Step 810 the target base station 1 sends a path switch request message (PATH SWITCH REQUEST) to the AMF.
  • the AMF receives the path switching request message.
  • the path switch request message includes the identifier of the PDU session of UE1 and the N4 container corresponding to each PDU session, or it can be understood that the path switch request message includes one or more (the identifier of the PDU session, the N4 container).
  • the N4 container is the N4 container in the handover preparation request message in step 805 above.
  • step 811 the AMF sends a session modification request message to the SMF.
  • the SMF receives the session modification request message.
  • the SMF here refers to the SMF corresponding to the PDU session.
  • different PDU sessions of UE1 may correspond to the same SMF, or may correspond to different SMFs, which is not limited in this application.
  • the session modification request message includes the N4 container corresponding to the PDU session.
  • the SMF performs corresponding operations according to 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 corresponds to the UPF of the PDU session
  • the F-SEID is replaced with the F-SEID of the target UPF1 in the N4 message.
  • the SMF stores the Nx tunnel information of the target UPF1 carried in the N4 container, the N3 tunnel information of the target UPF1, and the like.
  • the session modification request message may be an Nsmf_PDUSession_SMContextUpdate Request message.
  • step 812 the SMF sends a session modification request message to UPF2.
  • UPF2 receives the session modification request message.
  • the session modification request message includes the Nx tunnel information of the target UPF1 corresponding to the PDU session of UE1.
  • 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, so that UPF2 corresponds to the Nx tunnel information of the PDU session , the Nx tunnel information of the source UPF1 corresponding to the PDU session is updated to the Nx tunnel information of the target UPF1 corresponding to the PDU session, so that the subsequent UPF2 directly sends the received data that UE2 needs to send to UE1 to the target UPF1, that is, no longer Detour via source UPF1 and source base station 1.
  • the session modification request message may also include an End Marker indication, and the End Marker indication is used to instruct UPF2 to send the End Marker through the source path (that is, to the source UPF1).
  • UPF2 sends the End Marker through the source path according to the End Marker instruction.
  • UPF2 starts to send data through the new path (namely to the target UPF1).
  • the downlink path of UE1 is switched to: UE2->base station 2->UPF2->target UPF1->target base station 1->UE1.
  • both the uplink and downlink paths of UE1 are switched.
  • the session modification request message may be an N4 session modification request message, that is, a PFCP Session Modification Request message.
  • the SMF corresponding to the target UPF1 if the SMF corresponding to the target UPF1 is different from the SMF corresponding to UPF2, the SMF corresponding to the target UPF1 sends the Nx tunnel information of the target UPF1 corresponding to the PDU session of UE1 to the SMF corresponding to UPF2, and then the SMF corresponding to UPF2 Send the Nx tunnel information of the target UPF1 corresponding to the PDU session of UE1 to UPF2.
  • the End Marker instruction is also sent by the SMF corresponding to the target UPF1 to the SMF corresponding to UPF2, and then sent to UPF2 by the SMF corresponding to UPF2.
  • step 813 the SMF sends a session modification response message to the AMF.
  • the AMF receives the session modification response message.
  • the session modification response message includes an N4 container including the PFCP session modification response message.
  • the N4 container needs to be sent to the target UPF1.
  • the session modification response message may be a Nsmf_PDUSession_SMContextUpdate Response message.
  • 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 receives the path switch response message.
  • the path switching response message includes the identifier of the successfully switched PDU session and the N4 container corresponding to the PDU session, and the N4 container comes from the session modification response message in step 813 above.
  • step 815 the target base station 1 sends the N4 container to the target UPF1.
  • the target UPF1 receives the N4 container.
  • This N4 container includes the PFCP Session Modification Response message.
  • the embodiment corresponding to FIG. 8 reduces the signaling interaction between the satellite and the ground during the handover process (for example, reduces the signaling between the satellite and the ground by 50%), thereby reducing the link between the satellite and the ground. load and reduce switching delay.
  • the context information of the PDU session of the source UPF is sent to the target UPF, and the N3 tunnel between the target base station and the target UPF is established, thereby avoiding the detour of the uplink data through the source UPF and further reducing the data transmission delay .
  • FIG. 9 it is a schematic flowchart of a handover method provided by an embodiment of the present application.
  • This embodiment can be applied to a scenario where UE1 and UE2 are handed over across satellites at the same time (for example, this scenario occurs due to satellite movement).
  • the satellite of UE1 is handed over.
  • the source base station 1 and the source UPF1 on satellite 1 provide services for UE1.
  • the target base station 1 and target UPF1 on satellite 2 provide services for UE1.
  • the satellite of UE2 is also handed over.
  • the source base station 2 and the source UPF2 on the satellite 3 provide services for UE2.
  • FIG. 9 is an improvement to the embodiment of FIG. 6 described above.
  • the embodiment corresponding to FIG. 9 is also a specific implementation of the embodiment in FIG. 7(b) above.
  • This embodiment can be used for the timing problem of Nx tunnel switching caused when UE1 and UE2 move across satellites at the same time.
  • the process includes the following steps:
  • Step 901 to step 906 are the same as above step 801 to step 806.
  • step 906a the SMF sends the Nx tunnel information of the target UPF2 to the source UPF1.
  • the source UPF1 receives the Nx tunnel information of the target UPF2.
  • step 906a UE2 also undergoes handover, and the SMF has received the Nx tunnel information of the handover target UPF2.
  • the SMF Since the SMF does not yet know that UE1 is being handed over, the SMF will think that UE1 is still served by the source UPF1, so when the SMF receives the Nx tunnel information of the target UPF2 after UE2's handover, it sends the Nx tunnel information of the target UPF2 to the source UPF1.
  • This step 906a may be performed at any step after step 901 and before step 911.
  • the step 906a is executed after the step 906 and before the step 907 as an example for illustration.
  • the reason why this step 906a is limited to be performed after step 901 is because after step 901, the source UPF1 can know that UE1 is handing over, so when the source UPF1 receives the Nx tunnel information from the target UPF1 of the SMF, the source UPF1 can not temporarily Update the Nx tunnel information of the UPF, and perform the following step 906b.
  • step 906a is limited to be performed before step 911.
  • the SMF may know that UE1 is switching, and the SMF may not perform this step 906a, in other words, before step 911, the SMF It does not know that UE1 is handing over, so the SMF will perform the above step 906a.
  • the SMF may also send an End marker indication to the source UPF1, where the End marker indication is used to instruct the source UPF1 to send an End Marker through the source path (that is, to the source UPF2).
  • step 906b the source UPF1 sends a rejection message to the SMF.
  • the SMF receives the rejection message.
  • the rejection message may carry a cause value, and the cause value is that UE1 is switching.
  • the source UPF1 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. Wherein, if the 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.
  • the source UPF1 rejects the handover of the Nx tunnel, which means that the uplink data sent by UE1 is still sent to the source UPF2, and the source UPF2
  • the data is sent to the source base station 2, and the source base station 2 then sends it to the target base station 2 through the forwarding tunnel, and then the target base station 2 sends the data of UE1 to UE2.
  • the uplink data sent by UE1 detours between the source satellite (namely satellite 3 ) and the target satellite (namely satellite 4 ) of UE2 . Although there is a detour, it can avoid the disorder of data packets caused by concurrent switching.
  • Step 907 to step 911 are the same as above step 807 to step 811.
  • step 901 to step 906, and step 907 to step 911 refer to the corresponding steps in the embodiment of FIG. 8 .
  • the above steps 901 to 906, and the UPF2 involved in steps 907 to 911 all refer to the source UPF2.
  • Step 912 the SMF sends a session modification request message to the target UPF2.
  • the target UPF2 receives the session modification request message.
  • the session modification request message includes the Nx tunnel information of the target UPF1 corresponding to the PDU session of UE1, and the End Marker indication.
  • 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, so that the target UPF2 corresponds to the Nx tunnel information of the PDU session.
  • the tunnel information is updated from the Nx tunnel information of the source UPF1 to the Nx tunnel information of the target UPF1, so that the subsequent target UPF2 will directly send the received data that UE2 needs to send to UE1 to the target UPF1, that is, no longer go through the source UPF1 and the source base station 1 bypass.
  • the End Marker indication is used to instruct the target UPF2 to send the End Marker through the source path (that is, to the source UPF1).
  • the target UPF2 sends the End Marker through the source path.
  • the target UPF2 sends the received data that the UE2 needs to send to the UE1 to the target UPF1, and the target UPF1 sends the data to the UE1.
  • the downlink path switching of UE1 is: UE2->target base station 2->target UPF2->target UPF1->target base station 1->UE1.
  • both the uplink and downlink paths of UE1 are switched.
  • the target UPF2 is the information obtained from the source UPF2 to the source UPF1 during the handover preparation phase.
  • the session modification request message may be an N4 session modification request message, that is, a PFCP Session Modification Request message.
  • the SMF corresponding to the target UPF1 if the SMF corresponding to the target UPF1 is different from the SMF corresponding to the target UPF2, the SMF corresponding to the target UPF1 sends the Nx tunnel information and the End Marker indication of the target UPF1 corresponding to the PDU session of UE1 to the SMF corresponding to the target UPF2, Then the SMF corresponding to the target UPF2 sends the Nx tunnel information and End marker indication of the target UPF1 corresponding to the PDU session of UE1 to the target UPF2.
  • Step 913 the SMF sends a session modification response message to the AMF.
  • the AMF receives the session modification response message.
  • the session modification response message includes an N4 container including the PFCP session modification response message and the Nx tunnel information of the target UPF2.
  • the N4 container needs to be sent to the target UPF1.
  • the N4 container also includes an End Marker indication.
  • 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 receives the path switch response message.
  • the path switching response message includes the identifier of the successfully switched PDU session and the N4 container corresponding to the PDU session, and the N4 container comes from the session modification response message in step 913 above.
  • step 915 the target base station 1 sends the N4 container to the target UPF1.
  • the target UPF1 receives the N4 container.
  • the N4 container includes the PFCP session modification response message and the Nx tunnel information of the target UPF2, and the target UPF1 stores the Nx tunnel information of the target UPF2.
  • the target UPF1 sends an End Marker to the source UPF2 according to the End Marker indication, and starts sending data to the target UPF2.
  • the target UPF1 is information obtained from the source UPF2 during the handover preparation phase.
  • this embodiment is described by taking UE1 and UE2 served by the same AMF and SMF as an example, and this embodiment is also applicable to UE1 and UE2 being served by different SMFs and/or different AMFs.
  • the source UPF1 when the source UPF1 finds that the UPF of the communication peer of the UE being switched is also switched, the source UPF1 does not update the Nx tunnel, and still sends data through the source path, so as to avoid packet loss or Out of order.
  • the SMF before the SMF notifies the target UPF1 to send the End Marker, UE1 has switched the path to send uplink data to the target UPF1. Therefore, no uplink data has been sent to the target UPF1 through the source UPF1 before the SMF sends the End marker indication to the target UPF1.
  • the source UPF2 is down, 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 the data to the target UPF2.
  • the End Marker is further sent by the source UPF2 to the source base station 2, and sent by the source base station 2 to the target base station 2.
  • 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 sends the downlink data of UE2 received from the target UPF2 to UE2, and the sending time of the data packet received from the forwarding tunnel is shorter than The sending time of the data packet received from the target UPF2 is early, and should be sent to UE2 first, thus ensuring the sequential transmission of data.
  • FIG. 10 it is a schematic flowchart of a handover method provided by an embodiment of the present application.
  • This embodiment may be applied to a scenario where UE1 and UE2 are handed over across satellites at the same time caused by satellite movement.
  • the satellite of UE1 is handed over.
  • the source base station 1 and the source UPF1 on satellite 1 provide services for UE1.
  • the target base station 1 and target UPF1 on satellite 2 provide services for UE1.
  • the satellite of UE2 is also handed over.
  • the source base station 2 and the source UPF2 on the satellite 3 provide services for UE2.
  • the target base station 2 and the target UPF2 on the satellite 4 provide services for UE2.
  • the embodiment of FIG. 10 is an improvement to the embodiment of FIG. 6 described above.
  • the embodiment corresponding to FIG. 10 is also a specific implementation of the embodiment in FIG. 7(c) above.
  • This embodiment can be used for the timing problem of Nx tunnel switching caused when UE1 and UE2 move across satellites at the same time.
  • the process includes the following steps:
  • Step 1001 to step 1009 are the same as above step 801 to step 809.
  • the above-mentioned embodiment in FIG. 8 involves only one UPF of UE2, that is, UPF2, while the embodiment in FIG. 10 involves two UPFs in UE2, that is, source UPF2 and target UPF2.
  • the above step 1001 to step 1009 refer to the corresponding steps in the embodiment of FIG. 8 .
  • the UPF2 involved in the above step 1001 to step 1009 refers to the source UPF2.
  • UE2 also undergoes inter-satellite handover, and UE2 completes operations similar to the above steps 1001 to 1009 .
  • Step 1010 the target base station 1 sends a path switching request message (PATH SWITCH REQUEST) to the AMF.
  • the AMF receives the path switching request message.
  • the path switch request message includes the identifier of the PDU session of UE1 and the N4 container corresponding to each PDU session, or it can be understood that the path switch request message includes one or more (the identifier of the PDU session, the N4 container).
  • the N4 message is encapsulated in the N4 container corresponding to each PDU session.
  • the N4 message can be a PFCP session modification request message.
  • the PFCP session modification request message is generated by the target UPF1 for the PDU session, and is used to notify the SMF: the PDU session The corresponding UPF is switched.
  • the N4 session information for example, the F-SEID of SMF and/or the Node ID of SMF
  • the N4 interface information of target UPF1 for example, the F-SEID and/or the F-SEID of target UPF1 Or the Node ID of the target UPF1, etc., wherein the F-SEID of the target UPF1 is used to uniquely identify the session in the target UPF1
  • the Nx tunnel information of the target UPF1 allocated by the target UPF1 for the PDU session the Nx tunnel of the target UPF1
  • the information will be sent to the target UPF2 for the target UPF2 to send the data that the UE2 needs to send to the UE1 to the target UPF1.
  • the PFCP session modification request message may also include N3 tunnel information of the target UPF1 corresponding to the PDU session.
  • the PFCP session modification request message may also include N3 tunnel information of the target base station 1 corresponding to the PDU session.
  • Step 1011 the target base station 2 sends a path switch request message (PATH SWITCH REQUEST) to the AMF.
  • the AMF receives the path switching request message.
  • the path switch request message includes the identifier of the PDU session of UE2 and the N4 container corresponding to each PDU session, or it can be understood that the path switch request message includes one or more (the identifier of the PDU session, the N4 container).
  • the N4 message is encapsulated in the N4 container corresponding to each PDU session.
  • the N4 message can be a PFCP session modification request message.
  • the PFCP session modification request message is generated by the target UPF2 for the PDU session, and is used to notify the SMF: the PDU session The corresponding UPF is switched.
  • the PFCP session modification request message includes the N4 session information corresponding to the PDU session (for example, the F-SEID of the SMF and/or the Node ID of the SMF), the N4 interface information of the target UPF2 (for example, the F-SEID of the target UPF2, the target Node ID of UPF2, etc.) and the Nx tunnel information of the target UPF2 allocated by the target UPF2 for the PDU session, the Nx tunnel information of the target UPF2 will be sent to the target UPF1, and used for the target UPF1 to send the target UPF2 to the target UPF2.
  • UE1 needs to send to UE2 The data.
  • the PFCP session modification request message may also include N3 tunnel information of the target UPF2 corresponding to the PDU session.
  • the PFCP session modification request message may also include N3 tunnel information of the target base station 2 corresponding to the PDU session.
  • step 1012 the AMF sends a session modification request message to the SMF.
  • the SMF receives the session modification request message.
  • the SMF here refers to the SMF corresponding to the PDU session of UE1.
  • different PDU sessions of UE1 may correspond to the same SMF, or may correspond to different SMFs, which is not limited in this application.
  • the session modification request message includes the N4 container corresponding to the PDU session of UE1.
  • the N4 container is the N4 container received by the AMF in step 1010 above.
  • the SMF performs corresponding operations according to the N4 message in the N4 container, for example, the SMF replaces the NodeID of the source UPF1 of the UPF corresponding to the PDU session with the NodeID of the target UPF1 in the N4 message, and/or the SMF corresponds to the UPF of the PDU session
  • the F-SEID of the target UPF1 in the N4 message is replaced by the F-SEID of the target UPF1.
  • the SMF stores the Nx tunnel information of the target UPF1, the N3 tunnel information of the target UPF1, and the like.
  • the session modification request message may be an Nsmf_PDUSession_SMContextUpdate Request message.
  • Step 1013 the SMF sends a session modification response message to the AMF.
  • the AMF receives the session modification response message.
  • the session modification response message includes an N4 container including the PFCP session modification response message.
  • the N4 container needs to be sent to the target UPF1.
  • the session modification response message is a response message to the session modification request message in step 1012 above. Since the SMF has not 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.
  • the session modification response message may be a Nsmf_PDUSession_SMContextUpdate Response message.
  • step 1014 the AMF sends a session modification request message to the SMF.
  • the SMF receives the session modification request message.
  • the SMF here refers to the SMF corresponding to the PDU session of UE2.
  • different PDU sessions of UE2 may correspond to the same SMF, or may correspond to different SMFs, which is not limited in this application.
  • the session modification request message includes the N4 container corresponding to the PDU session of UE2.
  • the N4 container is the N4 container received by the AMF in step 1011 above.
  • the SMF performs corresponding operations according to the N4 message in the N4 container, for example, the 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 the F- The SEID is replaced with the F-SEID of the target UPF2 in the N4 message.
  • the SMF stores the Nx tunnel information of the target UPF2, the N3 tunnel information of the target UPF2, and the like.
  • the session modification request message may be an Nsmf_PDUSession_SMContextUpdate Request message.
  • 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 receives the path switch response message.
  • 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, and the N4 container comes from the session modification response message in step 1013 above.
  • Step 1016 the SMF sends a session modification response message to the AMF.
  • the AMF receives the session modification response message.
  • the session modification response message includes an N4 container, and the N4 container includes Nx tunnel information and an End Marker indication of the target UPF1.
  • the N4 container needs to be sent to the target UPF2.
  • the End Marker indication is used to instruct the target UPF2 to send the End Marker through the source path (that is, to the source UPF1) before sending data to the target UPF1.
  • the session modification response message is a response message to the session modification request message in step 1014 above. Since the SMF has 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.
  • the session modification response message may be a Nsmf_PDUSession_SMContextUpdate Response message.
  • step 1017 the AMF sends a path switch response message (PATH SWITCH REQUEST ACK) to the target base station 2.
  • PATH SWITCH REQUEST ACK a path switch response message
  • the target base station 2 receives the path switch response message.
  • the path switching response message includes the identifier of the PDU session of UE2 successfully switched and the N4 container corresponding to the PDU session, and the N4 container comes from the session modification response message in step 1016 above.
  • Step 1018 the target base station 2 sends the N4 container to the target UPF2.
  • the target UPF2 receives the N4 container.
  • the target UPF2 sends the End Marker through the source path (that is, to the source UPF1) according to the End Marker instruction in the N4 container.
  • the target UPF2 sends the received data that the UE2 needs to send to the UE1 to the target UPF1, and the target UPF1 sends the data to the UE1.
  • the downlink path switching of UE2 is: UE2->target base station 2->target UPF2->target UPF1->target base station 1->UE1.
  • the downlink path switching of UE1 is completed.
  • Step 1019 the SMF sends the Nx tunnel information and the End Marker indication of the target UPF2 to the target UPF1.
  • the target UPF1 receives the Nx tunnel information and the End Marker indication of the target UPF2.
  • the End Marker indication is used to instruct the target UPF1 to send the End Marker through the source path (that is, to the source UPF2) before sending data to the target UPF2.
  • the target UPF1 sends the End Marker through the source path (that is, to the source UPF2). Subsequently, the target UPF1 sends the received data that UE1 needs to send to UE2 to the target UPF2, and the target UPF2 sends it to UE2.
  • the uplink path switching of UE1 is: UE1->target base station 1->target UPF1->target UPF2->target base station 2->UE2. At this time, the uplink path switching of UE1 is completed.
  • this embodiment is described by taking UE1 and UE2 served by the same AMF and SMF as an example, and this embodiment is also applicable to UE1 and UE2 being served by different SMFs and/or different AMFs.
  • the SMF in step 1019, notifies the target UPF1 to switch paths and send the End marker, and the target UPF1 will not send any data packets to the source UPF2 after sending the End marker.
  • 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 sends the downlink data of UE2 received from the target UPF2 to UE2, and the sending time of the data packet received from the forwarding tunnel is shorter than The sending time of the data packet received from the target UPF2 is early, and should be sent to UE2 first, thus ensuring the sequential transmission of data.
  • FIG. 11 it is a schematic flowchart of a handover method provided by an embodiment of the present application.
  • This embodiment may be applied to a scenario where UE1 and UE2 are handed over across satellites at the same time caused by satellite movement.
  • the satellite of UE1 is handed over.
  • the source base station 1 and the source UPF1 on satellite 1 provide services for UE1.
  • the target base station 1 and target UPF1 on satellite 2 provide services for UE1.
  • the satellite of UE2 is also handed over.
  • the source base station 2 and the source UPF2 on the satellite 3 provide services for UE2.
  • the target base station 2 and the target UPF2 on the satellite 4 provide services for UE2.
  • the embodiment of FIG. 11 is an improvement to the embodiment of FIG. 6 described above.
  • the embodiment corresponding to FIG. 11 is also a specific implementation of the embodiment in FIG. 7( d ).
  • This embodiment can be used for the problem of data detour caused when UE1 and UE2 move across satellites at the same time.
  • the process includes the following steps:
  • Step 1101 to step 1103 are the same as above step 801 to step 803.
  • step 1103a the SMF sends the Nx tunnel information of the target UPF2 to the source UPF1.
  • the source UPF1 receives the Nx tunnel information of the target UPF2.
  • step 1103a UE2 also undergoes handover, and the SMF has received the Nx tunnel information of the handover target UPF2.
  • the SMF Since the SMF does not yet know that UE1 is being handed over, the SMF will think that UE1 is still served by the source UPF1, so when the SMF receives the Nx tunnel information of the target UPF2 after UE2's handover, it sends the Nx tunnel information of the target UPF2 to the source UPF1.
  • the source UPF1 rejects the Nx tunnel information of the target UPF2. For details, refer to the above step 906a and step 906b.
  • the source UPF1 does not reject the Nx tunnel information of the target UPF2, and the subsequent source UPF1 uses the Nx tunnel information of the target UPF2 to send the uplink data packet of UE1 to the target UPF2, and no longer sent to the source UPF2.
  • the SMF records the time stamp of sending the Nx tunnel information of the target UPF1 to the source UPF1.
  • the SMF After receiving the response message for this step 1103a, the SMF notifies the source UPF2 of UE2 to send the 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, and in the previous In the embodiment, the End Marker is sent by the source UPF1 or the target UPF1 of the peer UE (that is, UE1).
  • the SMF confirms that the UE1 side no longer sends data through the source path, it notifies the source UPF2 to send the End Marker.
  • the SMF notifies the source UPF1 to switch paths first, it can be considered that in general, the data packet sent by the source UPF1 to the source UPF2 is earlier than the SMF notifies the source UPF2 to send the End Marker.
  • Step 1103a may occur at any time before step 1106a.
  • the step 1103a occurs after step 1103 and before step 1104 as an example for illustration.
  • Step 1104 to step 1106 are the same as above step 804 to step 806.
  • Step 1106a the target base station 1 sends a handover preparation request message to the AMF of UE1.
  • the AMF receives the handover preparation request message.
  • the handover preparation request message includes the identifier of the target base station 1 and the N4 container corresponding to each PDU session of UE1.
  • An N4 message is encapsulated in the N4 container.
  • the N4 message can be a PFCP session modification request message.
  • the PFCP session modification request message 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 switched .
  • the N4 session information for example, the F-SEID of SMF and/or the Node ID of SMF
  • the N4 interface information of target UPF1 for example, the F-SEID and/or the F-SEID of target UPF1 Or the Node ID of the target UPF1, etc., wherein the F-SEID of the target UPF1 is used to uniquely identify the session in the target UPF1
  • the Nx tunnel information of the target UPF1 allocated by the target UPF1 for the PDU session the Nx tunnel of the target UPF1
  • the information will be sent to the target UPF2 for the target UPF2 to send the data of the UE2 to the target UPF1 according to the Nx tunnel information of the target UPF1.
  • the PFCP session modification request message may also include N3 tunnel information of the target UPF1 corresponding to the PDU session.
  • the PFCP session modification request message may also include N3 tunnel information of the target base station 1 corresponding to the PDU session.
  • the N4 container further includes Nx tunnel information of the source UPF2.
  • step 1106b the AMF sends a session modification request message to the SMF.
  • the SMF receives the session modification request message.
  • the session modification request message includes the N4 container corresponding to the PDU session and an indication information, and the indication information is used to prepare the process for handover.
  • step 1106c the SMF sends a session modification response message to the AMF.
  • the AMF receives the session modification response message.
  • the session modification response message includes an N4 container, and the N4 container includes the PFCP session modification response message.
  • the N4 container needs to be sent to the target UPF1.
  • SMF checks the timestamp of the Nx tunnel information of the target UPF2 sent to the source UPF1 last time. If the difference between the timestamp and the current time is less than the predetermined threshold, it indicates that the source UPF1 has received an updated Nx tunnel message after step 1102, that is, the target The tunnel information of UPF2, so the Nx tunnel information of the source UPF2 received by the target UPF1 is outdated, so the SMF carries the Nx tunnel information of the target UPF2 in the N4 container, so that the target UPF1 saves the Nx tunnel information of the target UPF2.
  • the SMF may not judge whether to send the Nx tunnel information of the target UPF2 to the target UPF1 based on the timestamp, but always carry the latest Nx tunnel information corresponding to UE2 stored locally in the N4 container. Whether the source UPF1 receives the latest Nx tunnel information corresponding to UE2, the target UPF1 can always receive the latest Nx tunnel information corresponding to UE2.
  • the SMF judges whether the Nx tunnel information of UPF2 stored locally is the same as the Nx tunnel information of UPF2 in the N4 container, and if not, then The latest Nx tunnel information corresponding to UE2 is carried in the N4 container of the session modification response message.
  • step 1106d the AMF sends a handover preparation response message to the target base station 1 .
  • the target base station 1 receives the handover preparation response message.
  • the 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, and the handover preparation response message includes the N4 container.
  • step 1106e the target base station 1 sends the N4 container to the target UPF1.
  • the target UPF1 receives the N4 container.
  • the target UPF1 saves the Nx tunnel information, and uses the Nx tunnel information when sending the uplink data packet of UE1 subsequently.
  • Step 1107 to step 1111 are the same as above step 807 to step 811.
  • the path switching request message in step 1110 may not carry the N4 container. This is because the handover preparation request message in the above step 1106a has already carried the N4 container, if the target UPF1 has no content to be updated, the target UPF1 does not need to carry the N4 container.
  • Step 1112 the SMF sends a session modification request message to the target UPF2.
  • the target UPF2 receives the session modification request message.
  • the session modification request message includes the Nx tunnel information of the target UPF1 corresponding to the PDU session of UE1.
  • 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, so that the target UPF2 corresponds to the Nx tunnel information of the PDU session.
  • Tunnel information, the Nx tunnel information of the source UPF1 corresponding to the PDU session is updated to the Nx tunnel information of the target UPF1 corresponding to the PDU session, so that the subsequent target UPF2 directly sends the received data that UE2 needs to send to UE1 to the target UPF1, That is, the source UPF1 and the source base station 1 are no longer detoured.
  • the session modification request message may be an N4 session modification request message, that is, a PFCP Session Modification Request message.
  • the SMF corresponding to the target UPF1 if the SMF corresponding to the target UPF1 is different from the SMF corresponding to the target UPF2, the SMF corresponding to the target UPF1 sends the Nx tunnel information of the target UPF1 corresponding to the PDU session of UE1 to the SMF corresponding to the target UPF2, and then the target UPF2 The corresponding SMF sends the Nx tunnel information of the target UPF1 corresponding to the PDU session of UE1 to the target UPF2.
  • Step 1113 is the same as step 813 above.
  • Step 1114 after the SMF confirms that the Nx tunnel information of the target UPF1 is sent to the target UPF2, the SMF sends an End Marker indication to the source UPF1. Correspondingly, the source UPF1 receives the End Marker indication.
  • the End Marker indication is used to instruct the source UPF1 to send the End Marker to the source base station 1, and the End Marker is forwarded by the source base station 1 to the target base station 1.
  • the target base station 1 knows that no more data will be sent from the source UPF1 to the target base station 1, therefore, the target base station 1 can start to process the data from the target UPF1.
  • SMF sends the latest Nx tunnel information corresponding to UE2 to source UPF1 in time, so source UPF1 can send UE1 data to target UPF2 according to the latest Nx tunnel information, avoiding sending data to The source UPF 2 then forwards through the forwarding path between the source base station 2 and the target base station 2, which reduces the detour of the data.
  • the SMF notifies the UE's source UPF to send the End Marker after confirming that the UE's communication peer has switched from the source path to the target path, so as to avoid packet disorder.
  • FIG. 12 it is a schematic flowchart of a handover method provided by an embodiment of the present application.
  • This embodiment may be applied to a scenario where UE1 and UE2 are handed over across satellites at the same time caused by satellite movement.
  • the satellite of UE1 is handed over.
  • the source base station 1 and the source UPF1 on satellite 1 provide services for UE1.
  • the target base station 1 and target UPF1 on satellite 2 provide services for UE1.
  • the satellite of UE2 is also handed over.
  • the source base station 2 and the source UPF2 on the satellite 3 provide services for UE2.
  • the target base station 2 and the target UPF2 on the satellite 4 provide services for UE2.
  • the embodiment of FIG. 12 is an improvement to the embodiment of FIG. 6 described above.
  • the embodiment corresponding to FIG. 12 is also a specific implementation of the embodiment in FIG. 7(e) above.
  • This embodiment can be used for the data detour problem caused when UE1 and UE2 move across satellites at the same time.
  • the process includes the following steps:
  • Step 1201 to step 1206 are the same as above step 801 to step 806.
  • Step 1206a is the same as the above step 1106a.
  • Step 1206b is the same as the above step 1106b.
  • Step 1206c is the same as the above step 1106c.
  • step 1206d the AMF sends a handover preparation response message to the target base station 1 .
  • the target base station 1 receives the handover preparation response message.
  • the handover preparation response message includes the N4 container.
  • This N4 container includes the PFCP Session Modification Response message.
  • the N4 container needs to be sent to the target UPF1.
  • step 1206e the target base station 1 sends the N4 container to the target UPF1.
  • the target UPF1 receives the N4 container.
  • the N4 container of step 1206c, step 1206d and step 1206e does not include the Nx tunnel information of the target UPF2.
  • the SMF receives the latest Nx tunnel information corresponding to UE2, that is, 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 Source UPF1.
  • 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 of the target UPF2 Tunnel information, that is, to send the uplink data of UE1 to the target UPF2.
  • the SMF Since the UE1 may continue to send uplink data through the source base station 1 at this time, the SMF also needs to send the Nx tunnel information of the target UPF2 to the source UPF1. In this way, the source UPF1 can also directly use the Nx tunnel information of the target UPF2, that is, send the uplink data of the UE1 to the target UPF2.
  • Step 1207 to step 1209 are the same as above step 807 to step 809.
  • Step 1210 after the SMF confirms 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 indication to the source UPF2. Correspondingly, the source UPF2 receives the End Marker indication.
  • the End Marker indication is used to instruct the source UPF2 to send the End Marker to the source base station 2, the source UPF2 to send the End Marker to the source base station 2, and the End Marker is forwarded by the source base station 2 to the target base station 2.
  • the target base station 2 knows that no more data will be sent from the source UPF2 to the target base station 2, so the target base station 2 can start processing the data sent by UPF1 (source UPF1 or target UPF1).
  • Step 1211 to step 1215 are the same as above step 1110 to step 1114.
  • SMF sends the latest Nx tunnel information corresponding to UE2 to source UPF1 in time, so source UPF1 can send UE1 data to target UPF2 according to the latest Nx tunnel information, avoiding sending data to The source UPF 2 then forwards through the forwarding path between the source base station 2 and the target base station 2, which reduces the detour of the data.
  • FIG. 13 it is a schematic flowchart of a handover method provided by an embodiment of the present application.
  • This embodiment may be applied to a scenario where UE1 and UE2 are handed over across satellites at the same time caused by satellite movement.
  • the satellite of UE1 is handed over.
  • the source base station 1 and the source UPF1 on satellite 1 provide services for UE1.
  • the target base station 1 and target UPF1 on satellite 2 provide services for UE1.
  • the satellite of UE2 is also handed over.
  • the source base station 2 and the source UPF2 on the satellite 3 provide services for UE2.
  • the target base station 2 and the target UPF2 on the satellite 4 provide services for UE2.
  • the embodiment of FIG. 13 is an improvement to the embodiment of FIG. 6 described above.
  • This embodiment can be used for the data detour problem caused when UE1 and UE2 move across satellites at the same time.
  • the process includes the following steps:
  • Step 1301 to step 1306 are the same as above step 801 to step 806.
  • Step 1306a is the same as the above step 1206a.
  • Step 1306b is the same as the above step 1206b.
  • Step 1306c is the same as the above step 1206c.
  • Step 1306d is the same as the above step 1206d.
  • Step 1306e is the same as the above step 1206e.
  • the N4 container of step 1306c, step 1306d and step 1306e does not include the Nx tunnel information of the target UPF2.
  • Step 1307 to step 1309 are the same as above step 807 to step 809.
  • Step 1310 the target base station 1 sends a path switch request message (PATH SWITCH REQUEST) to the AMF.
  • the AMF receives the path switching request message.
  • the path switching request message includes the identifier of the PDU session of UE1.
  • step 1311 UE2 also undergoes handover, and the target base station 2 of UE2 sends a path switch request message (PATH SWITCH REQUEST) to AMF.
  • the AMF receives the path switching request message.
  • the path switch request message includes the identifier of the PDU session of UE2.
  • step 1312 the AMF sends a session modification request message to the SMF.
  • the SMF receives the session modification request message.
  • the SMF here refers to the SMF corresponding to the PDU session of UE1.
  • different PDU sessions of UE1 may correspond to the same SMF, or may correspond to different SMFs, which is not limited in this application.
  • the session modification request message may be an Nsmf_PDUSession_SMContextUpdate Request message.
  • This message instructs the SMF to perform path switching.
  • Step 1313 the SMF sends the Nx tunnel information of the target UPF1 to the target UPF2 and the source UPF2.
  • step 1314 the SMF sends an End Marker indication to the source UPF1.
  • the source UPF1 receives the End Marker indication.
  • the End Marker indication is used to instruct the source UPF1 to send the End Marker to the source base station 1, and the End Marker is forwarded by the source base station 1 to the target base station 1.
  • the target base station 1 knows that no more data will be sent from the source UPF1 to the target base station 1, therefore, the target base station 1 can start to process the data from the target UPF1.
  • Step 1315 the SMF sends a session modification response message to the AMF.
  • the AMF receives the session modification response message.
  • the session modification response message includes an N4 container including the PFCP session modification response message.
  • the N4 container needs to be sent to the target UPF1.
  • step 1316 the AMF sends a session modification request message to the SMF.
  • the SMF receives the session modification request message.
  • the SMF here refers to the SMF corresponding to the PDU session of UE2.
  • different PDU sessions of UE2 may correspond to the same SMF, or may correspond to different SMFs, which is not limited in this application.
  • the session modification request message may be an Nsmf_PDUSession_SMContextUpdate Request message.
  • This message instructs the SMF to perform path switching.
  • step 1317 the AMF sends a path switch response message (PATH SWITCH REQUESTACK) to the target base station 1.
  • the target base station 1 receives the path switch response message.
  • Step 1318 the SMF sends the Nx tunnel information of the target UPF2 to the target UPF1.
  • the target UPF1 receives the Nx tunnel information of the target UPF2.
  • step 1319 the SMF sends an End Marker indication to the source UPF2.
  • the source UPF2 receives the End Marker indication.
  • the End Marker indication is used to instruct the source UPF2 to send the End Marker to the source base station 2, the source UPF2 to send the End Marker to the source base station 2, and the End Marker is forwarded by the source base station 2 to the target base station 2.
  • the target base station 2 knows that no more data will be sent from the source UPF2 to the target base station 2, so the target base station 2 can start processing the data sent by UPF1 (source UPF1 or target UPF1).
  • step 1318 all the data sent by the target UPF1 to the source UPF2 has arrived at the source UPF2.
  • Step 1320 the SMF sends a session modification response message to the AMF.
  • the AMF receives the session modification response message.
  • the session modification response message is a response to step 1316 .
  • 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 receives the path switch response message.
  • SMF sends the latest Nx tunnel information corresponding to UE2 to source UPF1 in time, so source UPF1 can send UE1 data to target UPF2 according to the latest Nx tunnel information, avoiding sending data to The source UPF 2 then forwards through the forwarding path between the source base station 2 and the target base station 2, which reduces the detour of the data.
  • FIG. 14 it is a schematic flowchart of a handover method provided by an embodiment of the present application.
  • This embodiment may be applied to a scenario where UE1 and UE2 are handed over across satellites at the same time caused by satellite movement.
  • the satellite of UE1 is handed over.
  • the source base station 1 and the source UPF1 on satellite 1 provide services for UE1.
  • the target base station 1 and target UPF1 on satellite 2 provide services for UE1.
  • the satellite of UE2 is also handed over.
  • the source base station 2 and the source UPF2 on the satellite 3 provide services for UE2.
  • the target base station 2 and the target UPF2 on the satellite 4 provide services for UE2.
  • the embodiment of FIG. 14 is an improvement to the embodiment of FIG. 6 described above.
  • the embodiment corresponding to FIG. 14 is also a specific implementation of the embodiment in FIG. 7(f) above.
  • This embodiment does not optimize the handover process.
  • the uplink and downlink data of the UE are all sent through the source UPF.
  • the SMF reselects the UPF deployed on the same satellite as the target base station as the target UPF, and switches the UPF currently corresponding to the UE to this UPF.
  • the process includes the following steps:
  • step 1401 the source base station 1 determines that the UE1 is to be handed over, and the source base station 1 sends a handover request message to the target base station 1 .
  • the target base station 1 receives the handover request message.
  • the handover request message includes the N3 tunnel information of the source UPF1.
  • Step 1402 the target base station 1 sends a handover response message to the source base station 1.
  • the source base station 1 receives the handover response message.
  • a forwarding tunnel between source base station 1 and target base station 1 can be established, so the downlink data sent to UE1 can be sent by source base station 1 to target base station 1 through the forwarding tunnel, and target base station 1 Temporarily cache downlink data.
  • Step 1403 the source base station 1 sends a handover command to UE1.
  • UE1 receives the handover command.
  • the handover command may be an RRC reconfiguration message.
  • Step 1404 UE1 synchronizes with target base station 1.
  • UE1 After receiving the handover command, UE1 initiates a synchronization process with target base station 1 so as to access through target base station 1 .
  • Step 1405 UE1 sends a handover completion indication to target base station 1.
  • the target base station 1 receives the handover completion indication.
  • the handover completion indication may be an RRC reconfiguration completion message.
  • target base station 1 may send downlink data to UE1.
  • the UE1 may send uplink data through target base station 1 .
  • the target base station 1 may use the N3 tunnel information of the source UPF1 received in step 1401 to send the uplink data to the source UPF1, and then the source UPF1 sends the uplink data to the source UPF2.
  • Step 1406 the target base station 2 sends a path switch request message (PATH SWITCH REQUEST) to the AMF.
  • the AMF receives the path switching request message.
  • UE2 also undergoes cross-satellite handover, and the cross-satellite handover process of UE2 may refer to the above steps 1401 to 1404. Then the target base station 2 of UE2 executes this step 1406 .
  • the path switching request includes information for selecting a UPF, such as identification information of the target base station 2 or identification information of the satellite 4, or the path switching request includes identification information of the target UPF2.
  • the path switch request also includes the N3 tunnel information of the target base station 2 .
  • Step 1407 the AMF sends a session modification request message to the SMF.
  • the SMF receives the session modification request message.
  • the session modification request message includes information for selecting a UPF or identification information of the target UPF2.
  • the path switch request also includes the N3 tunnel information of the target base station 2 .
  • the session modification request message may be an Nsmf_PDUSession_SMContextUpdate Request message.
  • step 1407a the SMF selects the target UPF2.
  • the SMF may send a query request to the NRF, which carries the identification information of the target base station 2, and the NRF sends the The SMF returns the identification information of the target UPF2 deployed on the same satellite as the target base station 2 .
  • the session modification request message includes information for selecting UPF, and the information for selecting UPF is the identification information of satellite 4, then SMF can send a query request to NRF, which carries the identification information of satellite 4, and NRF sends the information to SMF Return the identification information of the target UPF2 deployed on satellite 4.
  • the SMF may directly select the target UPF2.
  • Step 1408 the target base station 1 sends a path switch request message (PATH SWITCH REQUEST) to the AMF.
  • the AMF receives the path switching request message.
  • the path switching request includes information for selecting a UPF, for example, it may be identification information of target base station 1 or identification information of satellite 2, or the path switching request includes identification information of target UPF1.
  • the path switch request also includes the N3 tunnel information of the target base station 1 .
  • step 1409a the SMF sends a PFCP session establishment request message to the target UPF2.
  • the target UPF2 receives the PFCP session establishment request message.
  • 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 .
  • the SMF Since the SMF has not received the Nx tunnel information of the target UPF1, at this time, the SMF still sends the Nx tunnel information of the source UPF1 to the target UPF2.
  • step 1409b the target UPF2 sends a PFCP session establishment response message to the SMF.
  • the SMF receives the PFCP session establishment response message.
  • the PFCP session establishment response message includes the N3 tunnel information of the target UPF2 and the Nx tunnel information of the target UPF2.
  • Step 1410 AMF sends a session modification request message to SMF.
  • the SMF receives the session modification request message.
  • the session modification request message includes information for selecting a UPF or identification information of the target UPF1.
  • the path switch request also includes the N3 tunnel information of the target base station 1 .
  • step 1410 and step 1409b may be concurrent, that is, the SMFs arrive almost at the same time.
  • the session modification request message may be an Nsmf_PDUSession_SMContextUpdate Request message.
  • step 1410a the SMF selects the target UPF1.
  • the SMF may send a query request to the NRF, which carries the identification information of the target base station 1, and the NRF sends the The SMF returns the identification information of the target UPF1 deployed on the same satellite as the target base station 1.
  • the SMF may send a query request to the NRF, which carries the identification information of the satellite 2, and the NRF sends a query to the SMF. Return the identification information of the target UPF1 deployed on satellite 2.
  • the SMF may directly select the target UPF1.
  • step 1411 the SMF sends an N4 update message to the source UPF1.
  • the source UPF1 receives the N4 update message.
  • the N4 update message includes the Nx tunnel information and the End Marker indication of the target UPF2.
  • the SMF will suspend the processing of the handover process of UE1, and send the Nx tunnel information of the target UPF2 to the source UPF1 first. That is, if the path switching process of UE1 is being executed, after the SMF receives the Nx tunnel information of the target UPF of UE2, before sending the session update response message (step 1417), the SMF sends the source UPF1 the Nx tunnel information of the target UPF2 and the End Marker instructions.
  • the EndMarker indication is used to instruct the source UPF1 to send the End Marker through the source path (via the source UPF2).
  • the source UPF1 sends the End Marker through the source path (via the source UPF2) according to the EndMarker instruction.
  • the source UPF1 starts to send the received data that UE1 needs to send to UE2 (that is, the downlink data of UE2) to the target path (via the target UPF2).
  • the downlink data of UE2 is directly sent to UE2 through target UPF2 and target base station 2, and is no longer forwarded through source UPF2 and source base station 2.
  • step 1412a the SMF sends a PFCP session establishment request message to the target UPF1.
  • the target UPF1 receives the PFCP session establishment request message.
  • 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.
  • step 1412b the target UPF1 sends a PFCP session establishment response message to the SMF.
  • the SMF receives the PFCP session establishment response message.
  • the PFCP session establishment response message includes the N3 tunnel information of the target UPF1 and the Nx tunnel information of the target UPF1.
  • step 1413 the SMF sends an N4 update message to the source UPF2.
  • the source UPF2 receives the N4 update message.
  • the N4 update message includes the Nx tunnel information and the End Marker indication of the target UPF1.
  • the target base station 2 Since the path switching of UE2 has not been completed, the target base station 2 still sends the uplink data of UE2 to the source UPF2, so the SMF suspends the path switching process of UE2, and sends the Nx tunnel information of the target UPF1 to the source UPF2. That is, if the path switching process of UE2 is being executed, after the SMF receives the Nx tunnel information of the target UPF1, the SMF sends the Nx tunnel information and the End Marker indication of the target UPF1 to the source UPF2 before sending the session update response message (step 1415) .
  • the EndMarker indication is used to instruct the source UPF2 to send the End Marker through the source path (via the source UPF1).
  • the source UPF2 sends the End Marker through the source path (via the source UPF1) according to the EndMarker instruction.
  • the source UPF2 starts to send the received data that UE2 needs to send to UE1 (that is, the downlink data of UE1) to the target path (via the target UPF1).
  • the source UPF2 starts to send the data received from UE2 to be sent to UE1 through the new path (via the target UPF2), that is, the downlink data of UE1.
  • Step 1414 the SMF sends the Nx tunnel information of the target UPF1 to the target UPF2.
  • the target UPF2 receives the Nx tunnel information of the target UPF1.
  • the SMF needs to notify the target UPF2 to update the Nx tunnel information.
  • Step 1415 the SMF sends a session modification response message to the AMF.
  • the AMF sends a session modification response message.
  • the session modification response message is a session modification response for UE2.
  • the session modification response message includes the N3 tunnel information of the target UPF2.
  • the session modification response message may be a Nsmf_PDUSession_SMContextUpdate Response message.
  • 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 receives the path switch response message.
  • the path switch response message includes the N3 tunnel information of the target UPF2.
  • the data sent by UE2 to UE1 is directly sent by target base station 2 to target UPF2, without detour through source UPF2.
  • Step 1417 the SMF sends a session modification response message to the AMF.
  • the AMF sends a session modification response message.
  • the session modification response message is a session modification response for UE1.
  • the session modification response message includes the N3 tunnel information of the target UPF1.
  • the session modification response message may be a Nsmf_PDUSession_SMContextUpdate Response message.
  • step 1418 the AMF sends a path switch response message to the target base station 1.
  • the target base station 1 receives the path switch response message.
  • the path switching response message includes the N3 tunnel information of the target UPF1.
  • the SMF if the SMF receives new Nx tunnel information during the path switching process of the UE, the SMF first suspends the path switching process, and sends the new Nx tunnel information to the source UPF first. After the Nx path switching is completed, the SMF continues Path switching process. Therefore, if the UEs at both ends of the communication switch concurrently, the switching of the Nx tunnel is always earlier than the switching of the UPF of the UE, which is equivalent to decoupling the switching of the Nx tunnel and the switching of the UPF, and avoids the switching of the UPF at the same time as the switching of the Nx path. A situation occurs that causes some packets to be lost or out of order.
  • the session management network element, the user plane network element or the access network device includes corresponding hardware structures and/or software modules for performing various functions.
  • the present application can be implemented in the form of hardware or a combination of hardware and computer software with reference to the units and method steps of the examples described in the embodiments disclosed in the present application. Whether a certain function is executed by hardware or computer software drives the hardware depends on the specific application scenario and design constraints of the technical solution.
  • FIG. 15 and FIG. 16 are schematic structural diagrams of possible communication devices provided by the embodiments of the present application. These communication devices can be used to implement the functions of the session management network element, user plane network element or access network device in the above-mentioned Figure 7(a) to Figure 7(f), and the method embodiments in Figure 8 to Figure 14, and therefore also The beneficial effects possessed by the foregoing method embodiments can be realized.
  • the communication device may be a session management network element, a user plane network element or an access network device, or a module applied to a session management network element, a user plane network element or an access network device (such as chips).
  • a communication device 1500 includes a processing unit 1510 and a transceiver unit 1520 .
  • the communication device 1500 is configured to realize the functions of the session management network element, the user plane network element, or the access network device in the foregoing method embodiments.
  • the communication device is configured to perform the function of a session management network element
  • the transceiver unit 1520 is configured to receive an instruction from a target user plane network element of the first terminal device through the target access network device.
  • Information about handover of the user plane network element of the first terminal device where the information includes tunnel information of a target user plane network element of the first terminal device; and, sending the first terminal device to a user plane network element of the second terminal device Tunnel information of the target user plane network element of the second terminal device to update the user plane network element information of the first terminal device among the user plane network elements of the second terminal device, the tunnel information of the target user plane network element of the first terminal device It 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 transceiver unit 1520 is further configured to send an end mark indication to the user plane network element of the second terminal device, where the end mark indication is used to indicate that the source user plane network element of the first terminal device Meta send end tag.
  • the second terminal device is handed over, and the user plane network element of the second terminal device is the target user plane network element of the second terminal device;
  • the target access network device receives the tunnel of the target user plane network element of the second terminal device before receiving the information indicating that the user plane network element of the first terminal device is handed over from the target user plane network element of the first terminal device information; sending 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 tunnel information of the second terminal device in the source user plane network element of the first terminal device User plane network element information; and receiving a response message of rejecting update from the source user plane network element of the first terminal device.
  • the transceiving unit 1520 is further configured to receive, through the target access network device, an indication from the target user plane network element of the first terminal device that handover occurs to the user plane network element of the first terminal device After the information, the tunnel information of the target user plane network element of the second terminal device is sent to the target user plane network element of the first terminal device.
  • the second terminal device is handed over, 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 also configured to pass the target
  • the access network device receives the tunnel information of the target user plane network element of the second terminal device after receiving the information indicating that the user plane network element of the first terminal device is handed over from the target user plane network element of the first terminal device ; and sending 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.
  • the transceiver unit 1520 is further configured to send an end mark indication to the target user plane network element of the first terminal device, where the end mark indication is used to indicate that the source user plane network element of the second terminal device The network element sends the end marker.
  • the transceiving unit 1520 is configured to receive a session modification request from a mobility management network element, where the session modification request includes information indicating that the user plane network element of the first terminal device is switched.
  • the second terminal device is handed over, 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 also configured to pass the target The access network device receives the tunnel information of the target user plane network element of the second terminal device before receiving the information indicating that the user plane network element of the first terminal device is switched from the target user plane network element of the first terminal 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.
  • the transceiver unit 1520 is further configured to send an end mark indication to the source user plane network element of the first terminal device, where the end mark indication is used to indicate the source access to the first terminal device The network device sends the end marker.
  • the transceiver unit 1520 is further configured to send an end mark indication to the source user plane network element of the second terminal device, where the end mark indication is used to indicate the source access to the second terminal device The network device sends the end marker.
  • the transceiving unit 1520 is further configured to receive, through the target access network device, an indication from the target user plane network element of the first terminal device that handover occurs to the user plane network element of the first terminal device After the information, the tunnel information of the target user plane network element of the second terminal device is sent to the target user plane network element of the first terminal device.
  • the transceiver unit 1520 is further configured to receive tunnel information from the user plane network element of the second terminal device that is the target user plane network element of the first terminal device;
  • the tunnel information of the user plane network element of the second terminal device on the target user plane network element of the device is different from the tunnel information of the user plane network element of the second terminal device saved by the session management network element, and the first terminal device
  • the target user plane network element of the second terminal device sends the tunnel information of the target user plane network element of the second terminal device.
  • the transceiving unit 1520 is further configured to receive, through the target access network device, an indication from the target user plane network element of the first terminal device that handover occurs to the user plane network element of the first terminal device After receiving the tunnel information of the target user plane network element of the second terminal device; sending 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 Tunnel information of the target user plane network element.
  • the transceiver unit 1520 is further configured to send an end mark indication to the source user plane network element of the first terminal device, where the end mark indication is used to indicate the source access to the first terminal device The network device sends the end marker.
  • the transceiving 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 performing handover, the message includes indicating that the first terminal Information about handover of the user plane network element of the device.
  • 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 transmit the network element from the source user plane network of the first terminal device through the target access network device receiving the first tunnel information of the user plane network element of the second terminal device, and the first tunnel information of the user plane network element of the second terminal device is used to send the second terminal to the user plane network element of the second terminal device Downlink data of the device; sending 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, and the first tunnel information of the target user plane network element of the first terminal device The information is used to send downlink data of the first terminal device to a target user plane network element of the first terminal device.
  • the first tunnel information of the user plane network element of the second terminal device is included in the session context of the first terminal device, and the session context also includes the session of the session management network element At least one of the endpoint identifier, the packet detection rule corresponding to the session, and the identifier 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 session corresponding to the The packet detection rule is used for the target user plane network element of the first terminal device to process the uplink data packet and/or downlink data packet of the first terminal device.
  • the session corresponds to a local area network LAN group
  • the transceiver unit 1520 is further configured to receive the LAN group from the source user plane network element of the first terminal device through the target access network device A corresponding packet detection rule, the packet detection rule corresponding to the LAN group is used by the target user plane network element to process data packets sent to other UEs in the LAN group.
  • the transceiver unit 1520 is configured to send, through the target access network device, information indicating that the user plane network element of the first terminal device is switched to a session management network element, where the information includes the first The first tunnel information of the target user plane network element of the terminal device.
  • the information further includes the session endpoint identifier of the target user plane network element of the first terminal device, and the session endpoint identifier of the target user plane network element of the first terminal device is used in the first terminal device The session is identified in the target user plane network element of the terminal device.
  • the processing unit 1510 is configured to allocate the first tunnel information of the target user plane network element.
  • the transceiver unit 1520 is further configured to receive the tunnel information of the target access network device from the target access network device; send the target user plane network element information to the target access network device
  • the second tunnel information, 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.
  • the transceiver unit 1520 is further configured to receive the first tunnel information of the target user plane network element of the second terminal device from the session management network element; send the downlink data of the second terminal device.
  • the transceiving unit 1520 is further configured to receive an end mark indication from a session management network element; according to the end mark indication, send the end mark to the source user plane network element of the second terminal device.
  • the communication device is used to perform the function 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 includes the identifier of the session of the first terminal device
  • receives a handover preparation response message from the source user plane network element and the handover preparation response message includes the user plane network element of the second terminal device corresponding to the session the tunnel information of the user plane network element of the second terminal device through the target access network device to the target user plane network element of the first terminal device.
  • the transceiver unit 1520 is further configured to receive, from the target access network device, radio resource information allocated by the target access network device for the session; and send the radio resource information to the first terminal device .
  • the transceiver unit 1520 is further configured to receive the forwarding tunnel information of the target access network device corresponding to the session from the target access network device; The network device sends the downlink data of the first terminal device.
  • 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 the source user from the first terminal device through the source access network device Tunnel information of the user plane network element of the second terminal device on the network element; sending 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.
  • the transceiving 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 switched, and the information includes the Tunnel information of the target user plane network element of the first terminal device; sending the information to the session management network element.
  • the information further includes the session endpoint identifier of the target user plane network element of the first terminal device, and the session endpoint identifier of the target user plane network element of the first terminal device is used in the first terminal device The session is identified in the target user plane network element of the terminal device.
  • the tunnel information of the user plane network element of the second terminal device is included in the session context of the first terminal device, and the session context also includes the session endpoint identifier of the session management network element , at least one of 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 The rule is used for the target user plane network element of the first terminal device to process the uplink data packet and/or downlink data packet of the first terminal device.
  • the session corresponds to a local area network LAN group
  • the transceiver unit 1520 is further configured to receive a packet detection rule corresponding to the LAN group from the source user plane network element of the first terminal device, the The packet detection rule corresponding to the LAN group is 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 packet inspection rule corresponding to the group.
  • the communication device is used to perform the function of a session management network element
  • the transceiver unit 1520 is used to receive information indicating handover of the first terminal device; receive the target user plane network element from the second terminal device The first tunnel information of the target user plane network element of the first terminal device; sending 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, so as to update the first terminal device
  • the target base station of the first terminal device sends the second tunnel information of the target user plane network element of the first terminal device.
  • the transceiver unit 1520 is further configured to, before receiving the first tunnel information from the target user plane network element of the second terminal device, receive Information indicating handover of the second terminal device; sending 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.
  • the transceiver unit 1520 is further configured to send an end mark indication to the source user plane network element of the first terminal device, where the end mark indication is used to indicate that the source user plane network element of the second terminal device The network element sends the end marker.
  • processing unit 1510 and the transceiver unit 1520 can be directly obtained by referring to related descriptions in the above method embodiments, and details are not repeated here.
  • a 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.
  • the interface circuit 1620 may be a transceiver or an input/output interface.
  • the communication device 1600 may further include a memory 1630 for storing instructions executed by the processor 1610 or storing input data required by the processor 1610 to execute the instructions or storing data generated by the processor 1610 after executing the instructions.
  • the processor 1610 is used to realize the functions of the above-mentioned processing unit 1510
  • the interface circuit 1620 is used to realize the functions of the above-mentioned transceiver unit 1520.
  • processor in the embodiments of the present application may be a central processing unit (central processing unit, CPU), and may also be other general processors, digital signal processors (digital signal processor, DSP), application specific integrated circuits (application specific integrated circuit, ASIC), field programmable gate array (field programmable gate array, FPGA) or other programmable logic devices, transistor logic devices, hardware components or any combination thereof.
  • CPU central processing unit
  • DSP digital signal processor
  • ASIC application specific integrated circuit
  • FPGA field programmable gate array
  • a general-purpose processor can be a microprocessor, or any conventional processor.
  • the method steps in the embodiments of the present application may be implemented by means of hardware, or may be implemented by means of a processor executing software instructions.
  • Software instructions can be composed of corresponding software modules, and software modules 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 disk, removable hard disk, CD-ROM or any other form of storage medium known in the art.
  • An exemplary storage medium is coupled to the processor such the processor can read information from, and write information to, the storage medium.
  • the storage medium may also be a component of the processor.
  • the processor and storage medium can be located in the ASIC.
  • the ASIC can be located in the base station or the terminal.
  • the processor and the storage medium may also exist in the base station or the terminal as discrete components.
  • all or part of them may be implemented by software, hardware, firmware or any combination thereof.
  • software When implemented using software, it may be implemented in whole or in part in the form of a computer program product.
  • the computer program product comprises one or more computer programs or instructions. When the computer program or instructions are loaded and executed on the computer, the processes or functions described in the embodiments of the present application are executed in whole or in part.
  • the computer may be a general purpose computer, a special purpose computer, a computer network, a base station, user equipment or other programmable devices.
  • the computer program or instructions may be stored in or transmitted from one computer-readable storage medium to another computer-readable storage medium, for example, the computer program or instructions may be downloaded from a website, computer, A server or data center transmits to another website site, computer, server or data center by wired or wireless means.
  • the computer-readable storage medium may be any available medium that can be accessed by a computer, or a data storage device such as a server or a data center integrating one or more available media.
  • the available medium may be a magnetic medium, such as a floppy disk, a hard disk, or a magnetic tape; it may also be an optical medium, such as a digital video disk; or it may be a semiconductor medium, such as a solid state disk.
  • the computer readable storage medium may be a volatile or a nonvolatile storage medium, or may include both volatile and nonvolatile types of storage media.
  • “at least one” means one or more, and “multiple” means two or more.
  • “And/or” describes the association relationship of associated objects, indicating that there may be three types of relationships, for example, A and/or B, which can mean: A exists alone, A and B exist at the same time, and B exists alone, where A, B can be singular or plural.
  • the character “/” generally indicates that the contextual objects are an “or” relationship; in the formulas of this application, the character “/” indicates that the contextual objects are a "division” Relationship.

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Abstract

本申请提供一种切换方法、通信装置及通信系统。该方法包括：当为第一终端设备提供服务的用户面网元发生切换，切换后的目标用户面网元向会话管理网元发送指示该第一终端设备的用户面网元发生切换的信息，并在该信息中携带切换后的目标用户面网元的隧道信息，从而会话管理网元可以及时地将第一终端设备的切换后的目标用户面网元的隧道信息提供给第二终端设备的用户面网元，保证切换的正确执行。

Description

一种切换方法、通信装置及通信系统
相关申请的交叉引用
本申请要求在2021年12月21日提交中国专利局、申请号为202111568633.9、申请名称为“一种切换方法、通信装置及通信系统”的中国专利申请的优先权，其全部内容通过引用结合在本申请中。
技术领域
本申请涉及通信技术领域，尤其涉及一种切换方法、通信装置及通信系统。
背景技术
目前，为终端设备提供服务的接入网设备和用户面网元均可以部署在卫星上，基于该场景，当为终端设备提供服务的接入网设备和/或用户面网元发生切换时，如何实现正确切换，有待解决。
发明内容
本申请实施例提供一种切换方法、通信装置及通信系统，用以实现为终端设备提供服务的接入网设备和/或用户面网元的正确切换。
第一方面，本申请实施例提供一种切换方法，第一终端设备发生了切换，该方法可以由会话管理网元或应用于会话管理网元的模块(如芯片)来执行。该方法包括：会话管理网元通过第一终端设备的目标接入网设备接收来自该第一终端设备的目标用户面网元的指示该第一终端设备的用户面网元发生切换的信息，该信息包括该第一终端设备的目标用户面网元的隧道信息；该会话管理网元向第二终端设备的用户面网元发送该第一终端设备的目标用户面网元的隧道信息，以更新该第二终端设备的用户面网元中的该第一终端设备的用户面网元信息，该第一终端设备的目标用户面网元的隧道信息用于向该第一终端设备的目标用户面网元发送该第一终端设备的下行数据。
根据上述方案，当为第一终端设备提供服务的用户面网元发生切换，切换后的目标用户面网元向会话管理网元发送指示该第一终端设备的用户面网元发生切换的信息，并在该信息中携带切换后的目标用户面网元的隧道信息，从而会话管理网元可以及时地将第一终端设备的切换后的目标用户面网元的隧道信息提供给第二终端设备的用户面网元，保证切换的正确执行。
在一种可能的实现方法中，该会话管理网元向该第二终端设备的用户面网元发送结束标记指示，该结束标记指示用于指示向该第一终端设备的源用户面网元发送结束标记。
在一种可能的实现方法中，该第二终端设备发生切换，该第二终端设备的用户面网元是该第二终端设备的目标用户面网元；该会话管理网元通过该目标接入网设备接收来自该第一终端设备的目标用户面网元的指示该第一终端设备的用户面网元发生切换的信息之前，该会话管理网元接收该第二终端设备的目标用户面网元的隧道信息；该会话管理网元 向该第一终端设备的源用户面网元发送该第二终端设备的目标用户面网元的隧道信息以更新该第一终端设备的源用户面网元中的该第二终端设备的用户面网元信息；该会话管理网元接收来自该第一终端设备的源用户面网元的拒绝更新的响应消息。
在一种可能的实现方法中，该会话管理网元通过该目标接入网设备接收来自该第一终端设备的目标用户面网元的指示该第一终端设备的用户面网元发生切换的信息之后，该会话管理网元向该第一终端设备的目标用户面网元发送该第二终端设备的目标用户面网元的隧道信息。
在一种可能的实现方法中，该第二终端设备发生切换，该第二终端设备的用户面网元是该第二终端设备的目标用户面网元；会话管理网元通过该目标接入网设备接收来自该第一终端设备的目标用户面网元的指示该第一终端设备的用户面网元发生切换的信息之后，会话管理网元接收该第二终端设备的目标用户面网元的隧道信息；该会话管理网元向该第一终端设备的目标用户面网元发送该第二终端设备的目标用户面网元的隧道信息。
在一种可能的实现方法中，该会话管理网元向该第一终端设备的目标用户面网元发送结束标记指示，该结束标记指示用于指示向该第二终端设备的源用户面网元发送结束标记。
在一种可能的实现方法中，该会话管理网元接收来自移动性管理网元的会话修改请求，该会话修改请求包括指示该第一终端设备的用户面网元发生切换的信息。
在一种可能的实现方法中，该第二终端设备发生切换，该第二终端设备的用户面网元是该第二终端设备的目标用户面网元；该会话管理网元通过该目标接入网设备接收来自该第一终端设备的目标用户面网元的指示该第一终端设备的用户面网元发生切换的信息之前，该会话管理网元接收该第二终端设备的目标用户面网元的隧道信息；该会话管理网元向该第一终端设备的源用户面网元发送该第二终端设备的目标用户面网元的隧道信息。
在一种可能的实现方法中，该会话管理网元向该第一终端设备的源用户面网元发送结束标记指示，该结束标记指示用于指示向该第一终端设备的源接入网设备发送结束标记。
在一种可能的实现方法中，该会话管理网元向该第二终端设备的源用户面网元发送结束标记指示，该结束标记指示用于指示向该第二终端设备的源接入网设备发送结束标记。
在一种可能的实现方法中，该会话管理网元通过该目标接入网设备接收来自该第一终端设备的目标用户面网元的指示该第一终端设备的用户面网元发生切换的信息之后，该会话管理网元向该第一终端设备的目标用户面网元发送该第二终端设备的目标用户面网元的隧道信息。
在一种可能的实现方法中，该会话管理网元接收来自该第一终端设备的目标用户面网元的该第二终端设备的用户面网元的源隧道信息；若来自该第一终端设备的目标用户面网元的该第二终端设备的源用户面网元的隧道信息与该会话管理网元保存的该第二终端设备的目标用户面网元的隧道信息不同，该会话管理网元向该第一终端设备的目标用户面网元发送该第二终端设备的目标用户面网元的隧道信息。
在一种可能的实现方法中，该会话管理网元通过该目标接入网设备接收来自该第一终端设备的目标用户面网元的指示该第一终端设备的用户面网元发生切换的信息之后，该会话管理网元接收该第二终端设备的目标用户面网元的隧道信息；该会话管理网元向该第一终端设备的源用户面网元和该第一终端设备的目标用户面网元发送该第二终端设备的目标用户面网元的隧道信息。
在一种可能的实现方法中，该会话管理网元向该第一终端设备的源用户面网元发送结 束标记指示，该结束标记指示用于指示向该第一终端设备的源接入网设备发送结束标记。
在一种可能的实现方法中，会话管理网元接收来自移动性管理网元或该目标接入网设备的指示该第一终端设备正在进行切换的消息，该消息包括指示该第一终端设备的用户面网元发生切换的信息。
第二方面，本申请实施例提供一种切换方法，第一终端设备发生了切换，该方法可以由用户面网元或应用于用户面网元的模块(如芯片)来执行。该方法包括：第一终端设备的目标用户面网元通过第一终端设备的目标接入网设备从该第一终端设备的源用户面网元接收第二终端设备的用户面网元的第一隧道信息，该第二终端设备的用户面网元的第一隧道信息用于向该第二终端设备的用户面网元发送该第二终端设备的下行数据；该目标用户面网元通过该目标接入网设备向会话管理网元发送该第一终端设备的目标用户面网元的第一隧道信息，该第一终端设备的目标用户面网元的第一隧道信息用于向该第一终端设备的目标用户面网元发送该第一终端设备的下行数据。
根据上述方案，当为第一终端设备提供服务的用户面网元发生切换，切换后的目标用户面网元接收第二终端设备的用户面网元，以及向会话管理网元发送切换后的目标用户面网元的第一隧道信息，从而会话管理网元可以及时地将第一终端设备的切换后的目标用户面网元的第一隧道信息提供给第二终端设备的用户面网元，保证切换的正确执行。
在一种可能的实现方法中，该第二终端设备的用户面网元的第一隧道信息包含在该第一终端设备的会话的上下文中，该会话的上下文还包括该会话管理网元的会话端点标识、该会话对应的包检测规则、该会话管理网元的标识信息中的至少一项，该会话管理网元的会话端点标识用于在会话管理网元中标识该会话，该会话对应的包检测规则用于该第一终端设备的目标用户面网元处理该第一终端设备的上行数据包和/或下行数据包。
在一种可能的实现方法中，该会话对应于局域网LAN群组，该目标用户面网元通过该目标接入网设备接收来自该第一终端设备的源用户面网元的该LAN群组对应的包检测规则，该LAN群组对应的包检测规则用于该目标用户面网元处理发送给该LAN群组中其他UE的数据包。
在一种可能的实现方法中，该目标用户面网元通过该目标接入网设备向会话管理网元发送指示该第一终端设备的用户面网元发生切换的信息，该第一终端设备的用户面网元发生切换的信息包括该第一终端设备的目标用户面网元的第一隧道信息。
在一种可能的实现方法中，该第一终端设备的用户面网元发生切换的信息还包括该第一终端设备的目标用户面网元的会话端点标识，该第一终端设备的目标用户面网元的会话端点标识用于在该第一终端设备的目标用户面网元中标识该会话。
在一种可能的实现方法中，该目标用户面网元分配该目标用户面网元的第一隧道信息。
在一种可能的实现方法中，该目标用户面网元从该目标接入网设备接收该目标接入网设备的隧道信息；该目标用户面网元向该目标接入网设备发送该目标用户面网元的第二隧道信息，该目标用户面网元的第二隧道信息用于该第一终端设备的目标接入网设备向该目标用户面网元发送该第一终端设备的上行数据。
在一种可能的实现方法中，该目标用户面网元从会话管理网元接收该第二终端设备的目标用户面网元的第一隧道信息；该目标用户面网元向该第二终端设备的目标用户面网元发送该第二终端设备的下行数据。
在一种可能的实现方法中，该目标用户面网元从会话管理网元接收结束标记指示；该 目标用户面网元根据该结束标记指示，向该第二终端设备的源用户面网元发送结束标记。
第三方面，本申请实施例提供一种切换方法，第一终端设备发生了切换，该方法可以由接入网设备或应用于接入网设备的模块(如芯片)来执行。该方法包括：第一终端设备的源接入网设备向第一终端设备的源用户面网元发送切换准备请求消息，该切换准备请求消息包括该第一终端设备的会话的标识；该源接入网设备接收来自该源用户面网元的切换准备响应消息，该切换准备响应消息包括该会话对应的第二终端设备的用户面网元的隧道信息；该源接入网设备通过该目标接入网设备向该第一终端设备的目标用户面网元发送该第二终端设备的用户面网元的隧道信息。
根据上述方案，由第一终端设备的切换前的源用户面网元将第二终端的用户面网元的隧道信息，通过第一终端设备的源接入网设备提供给第一终端设备的切换后的目标用户面网元，可以加快切换流程以及保证切换的准确执行。
在一种可能的实现方法中，该源接入网设备从该目标接入网设备接收该目标接入网设备为该会话分配的无线资源信息；该源接入网设备向该第一终端设备发送该无线资源信息。
在一种可能的实现方法中，该源接入网设备从该目标接入网设备接收该会话对应的该目标接入网设备的转发隧道信息；该源接入网设备根据该转发隧道信息，向该目标接入网设备发送该第一终端设备的下行数据。
第四方面，本申请实施例提供一种切换方法，第一终端设备发生了切换，该方法可以由接入网设备或应用于接入网设备的模块(如芯片)来执行。该方法包括：第一终端设备的目标接入网设备通过第一终端设备的源接入网设备接收来自该第一终端设备的源用户面网元的第二终端设备的用户面网元的隧道信息；该目标接入网设备向该第一终端设备的目标用户面网元发送该第二终端设备的用户面网元的隧道信息。
根据上述方案，由第一终端设备的切换前的源用户面网元将第二终端的用户面网元的隧道信息，通过第一终端设备的源接入网设备提供给第一终端设备的切换后的目标用户面网元，可以加快切换流程以及保证切换的准确执行。
在一种可能的实现方法中，该目标接入网设备接收来自该第一终端设备的目标用户面网元的指示该第一终端设备的用户面网元发生切换的信息，该信息包括该第一终端设备的目标用户面网元的隧道信息；该目标接入网设备向会话管理网元发送该信息。
在一种可能的实现方法中，该信息还包括该第一终端设备的目标用户面网元的会话端点标识，该第一终端设备的目标用户面网元的会话端点标识用于在该第一终端设备的目标用户面网元中标识该会话。
在一种可能的实现方法中，该第二终端设备的用户面网元的隧道信息包含在该第一终端设备的会话的上下文中，该会话的上下文还包括该会话管理网元的会话端点标识、该会话对应的包检测规则、该会话管理网元的标识信息中的至少一项，该会话管理网元的会话端点标识用于在会话管理网元中标识该会话，该会话对应的包检测规则用于该第一终端设备的目标用户面网元处理该第一终端设备的上行数据包和/或下行数据包。
在一种可能的实现方法中，该会话对应于局域网LAN群组，该目标接入网设备接收来自该第一终端设备的源用户面网元的该LAN群组对应的包检测规则，该LAN群组对应的包检测规则用于该第一终端设备的目标用户面网元处理发送给该LAN群组中其他UE的数据包；该目标接入网设备向该第一终端设备的目标用户面网元发送该LAN群组对应的包检测规则。
第五方面，本申请实施例提供一种切换方法，第一终端设备和第二终端设备发生了切换，该方法可以由会话管理网元或应用于会话管理网元的模块(如芯片)来执行。该方法包括：会话管理网元接收指示第一终端设备发生切换的信息；会话管理网元接收来自该第二终端设备的目标用户面网元的第一隧道信息；该会话管理网元向该第一终端设备的源用户面网元发送该第二终端设备的目标用户面网元的第一隧道信息，以更新第一终端设备的源用户面网元中的第二终端设备的用户面网元信息；该会话管理网元向该第一终端设备的目标用户面网元发送该第二终端设备的目标用户面网元的第一隧道信息；该会话管理网元向该第一终端设备的目标接入网设备发送该第一终端设备的目标用户面网元的第二隧道信息。
在一种可能的实现方法中，该会话管理网元接收来自该第二终端设备的目标用户面网元的第二终端设备的该目标用户面网元的第一隧道信息之前，该会话管理网元接收指示该第二终端设备发生切换的信息；该会话管理网元向该第二终端设备的目标用户面网元发送该第一终端设备的源用户面网元的第一隧道信息。
在一种可能的实现方法中，该会话管理网元向该第一终端设备的目标用户面网元发送该第二终端设备的目标用户面网元的第一隧道信息之前，该会话管理网元向该第一终端设备的源用户面网元发送结束标记指示，该结束标记指示用于指示向该第二终端设备的源用户面网元发送结束标记。
第六方面，本申请实施例提供一种通信装置，该装置可以是会话管理网元或应用于会话管理网元中的模块(如芯片)。该装置具有实现上述第一方面或第五方面的任意实现方法的功能。该功能可以通过硬件实现，也可以通过硬件执行相应的软件实现。该硬件或软件包括一个或多个与上述功能相对应的模块。
第七方面，本申请实施例提供一种通信装置，该装置可以是用户面网元或应用于用户面网元中的模块(如芯片)。该装置具有实现上述第二方面的任意实现方法的功能。该功能可以通过硬件实现，也可以通过硬件执行相应的软件实现。该硬件或软件包括一个或多个与上述功能相对应的模块。
第八方面，本申请实施例提供一种通信装置，该装置可以是用户面网元或应用于用户面网元中的模块(如芯片)。该装置具有实现上述第三方面或第四方面的任意实现方法的功能。该功能可以通过硬件实现，也可以通过硬件执行相应的软件实现。该硬件或软件包括一个或多个与上述功能相对应的模块。
第九方面，本申请实施例提供一种通信装置，包括与存储器耦合的处理器，该处理器用于调用所述存储器中存储的程序，以执行上述第一方面至第五方面中的任意实现方法。该存储器可以位于该装置之内，也可以位于该装置之外。且该处理器可以是一个或多个。
第十方面，本申请实施例提供一种通信装置，包括处理器和存储器；该存储器用于存储计算机指令，当该装置运行时，该处理器执行该存储器存储的计算机指令，以使该装置执行上述第一方面至第五方面中的任意实现方法。
第十一方面，本申请实施例提供一种通信装置，包括用于执行上述第一方面至第五方面中的任意实现方法的各个步骤的单元或手段(means)。
第十二方面，本申请实施例提供一种通信装置，包括处理器和接口电路，所述处理器用于通过接口电路与其它装置通信，并执行上述第一方面至第五方面中的任意实现方法。该处理器包括一个或多个。
第十三方面，本申请实施例还提供一种芯片系统，包括：处理器，用于执行上述第一方面至第五方面中的任意实现方法。
第十四方面，本申请实施例还提供一种计算机可读存储介质，所述计算机可读存储介质中存储有指令，当其在通信装置上运行时，使得上述第一方面至第五方面中的任意实现方法被执行。
第十五方面，本申请实施例还提供一种计算机程序产品，该计算机程序产品包括计算机程序或指令，当计算机程序或指令被通信装置运行时，使得上述第一方面至第五方面中的任意实现方法被执行。
第十六方面，本申请实施例一种通信系统，包括执行上述第一方面中任意实现方法的通信装置、执行上述第二方面中任意实现方法的通信装置、执行上述第三方面中任意实现方法的通信装置、执行上述第四方面中任意实现方法的通信装置或执行上述第五方面中任意实现方法的通信装置中的任意多个。
附图说明
图1(a)为基于服务化架构的5G网络架构示意图；
图1(b)为基于点对点接口的5G网络架构示意图；
图2为UE之间的通信路径的示意图；
图3为UE之间的通信路径的示意图；
图4为UE之间的通信路径的示意图；
图5为本申请实施例提供的一种切换方法的流程示意图；
图6为本申请实施例提供的一种切换方法的流程示意图；
图7(a)为本申请实施例提供的一种切换方法的流程示意图；
图7(b)为本申请实施例提供的一种切换方法的流程示意图；
图7(c)为本申请实施例提供的一种切换方法的流程示意图；
图7(d)为本申请实施例提供的一种切换方法的流程示意图；
图7(e)为本申请实施例提供的一种切换方法的流程示意图；
图7(f)为本申请实施例提供的一种切换方法的流程示意图；
图8为本申请实施例提供的一种切换方法的流程示意图；
图9为本申请实施例提供的一种切换方法的流程示意图；
图10为本申请实施例提供的一种切换方法的流程示意图；
图11为本申请实施例提供的一种切换方法的流程示意图；
图12为本申请实施例提供的一种切换方法的流程示意图；
图13为本申请实施例提供的一种切换方法的流程示意图；
图14为本申请实施例提供的一种切换方法的流程示意图；
图15为本申请实施例提供的一种通信装置示意图；
图16为本申请实施例提供的一种通信装置示意图。
具体实施方式
为了应对无线宽带技术的挑战，保持第三代合作伙伴计划(3rd generation partnership  project，3GPP)网络的领先优势，3GPP标准组制定了下一代移动通信网络系统(Next Generation System)架构，称为5G网络架构。该架构不但支持3GPP标准组定义的无线接入技术(如长期演进(long term evolution，LTE)接入技术，5G无线接入网(radio access network，RAN)接入技术等)接入到5G核心网(core network，CN)，而且支持使用非3GPP(non-3GPP)接入技术通过非3GPP转换功能(non-3GPP interworking function，N3IWF)或下一代接入网关(next generation packet data gateway，ngPDG)接入到核心网。
图1(a)为基于服务化架构的5G网络架构示意图。图1(a)所示的5G网络架构中可包括接入网设备以及核心网设备。终端设备通过接入网设备和核心网设备接入数据网络(data network，DN)。其中，核心网设备包括但不限于以下网元中的部分或者全部：鉴权服务器功能(authentication server function，AUSF)网元(图中未示出)、统一数据管理(unified data management，UDM)网元、统一数据库(unified data repository，UDR)网元、网络存储功能(network repository function，NRF)网元(图中未示出)、网络开放功能(network exposure function，NEF)网元(图中未示出)、应用功能(application function，AF)网元、策略控制功能(policy control function，PCF)网元、接入与移动性管理功能(access and mobility management function，AMF)网元、会话管理功能(session management function，SMF)网元、用户面功能(user plane function，UPF)网元、绑定支持功能(binding support function，BSF)网元(图中未示出)。
终端设备可以是用户设备(user equipment，UE)、移动台、移动终端设备等。终端设备可以广泛应用于各种场景，例如，设备到设备(device-to-device，D2D)、车物(vehicle to everything，V2X)通信、机器类通信(machine-type communication，MTC)、物联网(internet of things，IOT)、虚拟现实、增强现实、工业控制、自动驾驶、远程医疗、智能电网、智能家具、智能办公、智能穿戴、智能交通、智慧城市等。终端设备可以是手机、平板电脑、带无线收发功能的电脑、可穿戴设备、车辆、城市空中交通工具(如无人驾驶机、直升机等)、轮船、机器人、机械臂、智能家居设备等。
接入网设备可以是无线接入网(RAN)设备或有线接入网(wirelineaccess network，FAN)设备。其中，无线接入网设备包括3GPP接入网设备、非可信非3GPP接入网设备和可信非3GPP接入网设备。3GPP接入网设备包括但不限于：LTE中的演进型基站(evolved NodeB，eNodeB)、5G移动通信系统中的下一代基站(next generation NodeB，gNB)、未来移动通信系统中的基站或完成基站部分功能的模块或单元，如集中式单元(central unit，CU)，分布式单元(distributed unit，DU)等。非可信非3GPP接入网设备包括但不限于：非可信非3GPP接入网关或N3IWF设备、非可信无线局域网(wireless local area network，WLAN)接入点(access point，AP)、交换机、路由器。可信非3GPP接入网设备包括但不限于：可信非3GPP接入网关、可信WLAN AP、交换机、路由器。有线接入网设备包括但不限于：有线接入网关(wireline access gateway)、固定电话网络设备、交换机、路由器。
接入网设备和终端设备可以是固定位置的，也可以是可移动的。接入网设备和终端设备可以部署在陆地上，包括室内或室外、手持或车载；也可以部署在水面上；还可以部署在空中的飞机、气球和人造卫星上。本申请的实施例对接入网设备和终端设备的应用场景不做限定。
AMF网元，包含执行移动性管理、接入鉴权/授权等功能。此外，还负责在终端设备与PCF网元间传递用户策略。
SMF网元，包含执行会话管理、执行PCF下发的控制策略、选择UPF、分配终端设备的互联网协议(internet protocol，IP)地址等功能。
UPF网元，包含完成用户面数据转发、基于会话/流级的计费统计、带宽限制等功能。
UDM网元，包含执行管理签约数据、用户接入授权等功能。
UDR网元，包含执行签约数据、策略数据、应用数据等类型数据的存取功能。
NEF网元，用于支持能力和事件的开放。
AF网元，传递应用侧对网络侧的需求，例如，QoS需求或用户状态事件订阅等。AF可以是第三方功能实体，也可以是运营商部署的应用服务，如IP多媒体子系统(IP Multimedia Subsystem，IMS)语音呼叫业务。其中，AF网元包括核心网内的AF网元(即运营商的AF网元)和第三方AF网元(如某个企业的应用服务器)。
PCF网元，包含负责针对会话、业务流级别进行计费、QoS带宽保障及移动性管理、终端设备策略决策等策略控制功能。PCF网元包括接入与移动性管理策略控制网元(access and mobility management policy control function，AM PCF)网元和会话管理策略控制功能(session management PCF，SM PCF)网元。其中，AM PCF网元用于为终端设备制定AM策略，AM PCF网元也可以称为为终端设备提供服务的策略控制网元(PCF for a UE))。SM PCF网元用于为会话制定会话管理策略(session management policy，SM策略)，SM PCF网元也可以称为为会话提供服务的策略控制网元((PCF for a PDU session))。
NRF网元，可用于提供网元发现功能，基于其他网元的请求，提供网元类型对应的网元信息。NRF还提供网元管理服务，如网元注册、更新、去注册以及网元状态订阅和推送等。
BSF网元，可提供BSF服务注册/注销/更新，与NRF连接检测，会话绑定信息创建，UE信息的获取，IP地址重复的会话绑定信息查询等功能。
AUSF网元，负责对用户进行鉴权，以确定是否允许用户或设备接入网络。
DN，是位于运营商网络之外的网络，运营商网络可以接入多个DN，DN上可部署多种业务，可为终端设备提供数据和/或语音等服务。例如，DN是某智能工厂的私有网络，智能工厂安装在车间的传感器可为终端设备，DN中部署了传感器的控制服务器，控制服务器可为传感器提供服务。传感器可与控制服务器通信，获取控制服务器的指令，根据指令将采集的传感器数据传送给控制服务器等。又例如，DN是某公司的内部办公网络，该公司员工的手机或者电脑可为终端设备，员工的手机或者电脑可以访问公司内部办公网络上的信息、数据资源等。
图1(a)中Npcf、Nufr、Nudm、Naf、Namf、Nsmf分别为上述PCF、UDR、UDM、AF、AMF和SMF提供的服务化接口，用于调用相应的服务化操作。N1、N2、N3、N4以及N6为接口序列号，这些接口序列号的含义如下：
1)、N1：AMF与终端设备之间的接口，可以用于向终端设备传递非接入层(non access stratum，NAS)信令(如包括来自AMF的QoS规则)等。
2)、N2：AMF与接入网设备之间的接口，可以用于传递核心网侧至接入网设备的无线承载控制信息等。
3)、N3：接入网设备与UPF之间的接口，主要用于传递接入网设备与UPF间的上下行用户面数据。
4)、N4：SMF与UPF之间的接口，可以用于控制面与用户面之间传递信息，包括控 制面向用户面的转发规则、QoS规则、流量统计规则等的下发以及用户面的信息上报。
5)、N6：UPF与DN的接口，用于传递UPF与DN之间的上下行用户数据流。
图1(b)为基于点对点接口的5G网络架构示意图，其中的网元的功能的介绍可以参考图1(b)中对应的网元的功能的介绍，不再赘述。图1(b)与图1(a)的主要区别在于：图1(a)中的各个控制面网元之间的接口是服务化的接口，图1(b)中的各个控制面网元之间的接口是点对点的接口。
在图1(b)所示的架构中，各个网元之间的接口名称及功能如下：
1)、N1、N2、N3、N4和N6接口的含义可以参考前述描述。
2)、N5：AF网元与PCF网元之间的接口，可以用于应用业务请求下发以及网络事件上报。
3)、N7：PCF网元与SMF网元之间的接口，可以用于下发协议数据单元(protocol data unit，PDU)会话粒度以及业务数据流粒度控制策略。
4)、N8：AMF网元与UDM网元间的接口，可以用于AMF网元向UDM网元获取接入与移动性管理相关签约数据与鉴权数据，以及AMF网元向UDM网元注册终端设备移动性管理相关信息等。
5)、N9：UPF网元和UPF网元之间的用户面接口，用于传递UPF网元间的上下行用户数据流。
6)、N10：SMF网元与UDM网元间的接口，可以用于SMF网元向UDM网元获取会话管理相关签约数据，以及SMF网元向UDM网元注册终端设备会话相关信息等。
7)、N11：SMF网元与AMF网元之间的接口，可以用于传递接入网设备和UPF之间的PDU会话隧道信息、传递发送给终端设备的控制消息、传递发送给接入网设备的无线资源控制信息等。
8)、N15：PCF网元与AMF网元之间的接口，可以用于下发终端设备策略及接入控制相关策略。
9)、N35：UDM网元与UDR网元间的接口，可以用于UDM网元从UDR网元中获取用户签约数据信息。
10)、N36：PCF网元与UDR网元间的接口，可以用于PCF网元从UDR网元中获取策略相关签约数据以及应用数据相关信息。
可以理解的是，上述网元或者功能既可以是硬件设备中的网络元件，也可以是在专用硬件上运行软件功能，或者是平台(例如，云平台)上实例化的虚拟化功能。可选的，上述网元或者功能可以由一个设备实现，也可以由多个设备共同实现，还可以是一个设备内的一个功能模块，本申请实施例对此不作具体限定。
本申请中的用户面网元、移动性管理网元、会话管理网元分别可以是5G系统中的UPF网元、AMF网元、SMF网元，也可以是未来通信如6G网络中具有上述UPF网元、AMF网元、SMF网元的功能的网元，本申请对此不限定。在本申请的实施例中，以UPF网元、AMF网元、SMF网元分别为用户面网元、移动性管理网元、会话管理网元的一个示例进行描述。并且，将UPF网元、AMF网元、SMF网元分别简称为UPF、AMF、SMF。
为便于说明，本申请实施例中，以基站(如4G的eNB、5G的gNB或未来通信中的基站)作为接入网设备的一个示例进行说明，后续出现的“基站”均可以替换为“接入网设备”。本申请实施例中，以UE作为终端设备的一个示例进行说明，后续出现的“UE” 均可以替换为“终端设备”。
本申请实施例中，UPF的Nx隧道信息或UPF的第一隧道信息，指的是用于其他UPF向该UPF发送数据的隧道信息。比如UPF2可以根据UPF1的Nx隧道信息，向UPF1发送数据。本申请实施例中，UPF的Nx隧道信息也可以称为UPF的隧道信息，或者有其它名称，比如在5G局域网(local area network，LAN)中称为UPF的N19隧道信息，对此不做限定。
本申请实施例中，UPF的N3隧道信息或UPF的第二隧道信息，指的是用于基站向该UPF发送数据的隧道信息。比如基站可以根据UPF1的N3隧道信息，向UPF1发送数据。本申请实施例中，UPF的N3隧道信息也可以称为UPF的隧道信息，或者有其它名称，对此不做限定。
本申请实施例中，基站的N3隧道信息或基站的隧道信息，指的是用于UPF向该基站发送数据的隧道信息。比如UPF可以根据基站1的N3隧道信息，向基站1发送数据。本申请实施例中，基站的N3隧道信息也可以称为基站的隧道信息，或者有其它名称，对此不做限定。
3GPP R17提出将基站部署到卫星上。按现有架构，只将基站部署到卫星，会话的锚点UPF仍然部署在地面。参考图2，为UE之间的通信路径的示意图。UE1与UE2之间的通信路径为：UE1->UE1的卫星基站1->UE1的地面UPF1->UE2的地面UPF2->UE2的卫星基站2->UE2。该路径中包括了四段天地通信(也称为星地通信)，具体为：1)UE1->UE1的卫星基站1；2)UE1的卫星基站1->UE1的地面UPF1；3)UE2的地面UPF2->UE2的卫星基站2；4)UE2的卫星基站2->UE2。其中，卫星基站与地面UPF间的路径包括卫星与地面站间的馈电电路，以及地面站与UPF间的地面链路。UE与卫星基站间为4G空口、5G空口或未来通信中的空口。
由于卫星部署位置离地面较远，若经过四段星地链路会导致UE与UE间的通信时延较大。为了减少通信时延，可以在卫星上部署UPF，从而UE与UE间的通信可以不经过地面UPF，直接通过卫星间的链路转发，从而可以减少两段馈电电路的时延。参考图3，为UE之间的通信路径的示意图。UE1与UE2之间的通信路径为：UE1->UE1的卫星基站1->UE1的卫星UPF1->UE2的卫星UPF2->UE2的卫星基站2->UE2。该路径中包括了两段星地通信，具体为：1)UE1->UE1的卫星基站1；2)UE2的卫星基站2->UE2。
当UPF部署到卫星之后，为了减少卫星间路由的复杂性，在UE1和UE2间进行直接通信时，UE1的卫星UPF和UE2的卫星UPF间可以建立Nx隧道，用于在UE1和UE2的卫星间转发数据，从而UE的IP地址可以不暴露在卫星间链路接口上，卫星间链路的底层路由模块只看到卫星UPF的IP地址，看不到UE的IP地址。参考图4，为UE之间的通信路径的示意图，可以看出，在卫星UPF1和卫星UPF2之间增加了Nx接口，也即卫星UPF1和卫星UPF2之间建立Nx隧道。示例性的，Nx隧道可以是N19隧道，Nx隧道可以是GPRS隧道协议用户面(GRPS Tunnelling Protocol User Plane，GTP-U)隧道。其中，GPRS指的是通用无线分组业务(general packet radio service)。
在图4中，为了减少时延，为UE服务的卫星基站和卫星UPF可以位于同一颗卫星上，因此UPF1与基站1位于同一颗卫星上，UPF2与基站2位于同一颗卫星上，并且在UPF1与UPF2间建立了Nx隧道，以便UPF1和UPF2转发UE1与UE2间进行通信的数据包时，不用处理基于UE IP地址的路由，减少星间路由的复杂性。UE1的UPF1和UE2的UPF2 可以由不同的SMF控制，也可能由相同的SMF控制。图4中示出了UPF1和UPF2分别由不同的SMF控制的情形。
当基站和UPF部署到卫星上时，由于卫星是绕地球按固定频率移动的，并且低轨卫星移动速度很快，UE在地面上即使不移动也会发生卫星切换。在上述架构中，卫星的切换意味着为UE服务的卫星基站和卫星UPF同时发生了变化。
参考图5，为本申请实施例提供的一种切换方法的流程示意图。该流程中，UE1的卫星发生切换，切换前，由卫星1上的源基站1和源UPF1为UE1提供服务，切换后，由卫星2上的目标基站1和目标UPF1为UE1提供服务。UE2的卫星没有发生切换，为该UE2提供服务的是卫星3上的基站2和UPF2。该流程包括以下步骤：
步骤501，源基站1向目标基站1发送切换请求消息。相应的，目标基站1接收该切换请求消息。
该切换请求消息包括源UPF1的N3隧道信息，以便建立目标基站1到源UPF1的上行隧道，即目标基站1可将从UE1收到的上行数据发送给源UPF1。
步骤502，目标基站1向源基站1发送切换响应消息。相应的，源基站1接收该切换响应消息。
该切换响应消息包括目标基站1为UE1分配的无线资源信息。
通过上述步骤501和步骤502，还建立了源基站1与目标基站1间的转发隧道。
步骤503，源基站1向UE1发送RRC重配置消息。相应的，UE1接收该RRC重配置消息。
该RRC重配置消息包括目标基站1为UE1分配的无线资源信息。
源基站1可停止向UE1发送下行数据，并开始通过源基站1与目标基站1之间的转发隧道，将收到的需要发送给UE1的下行数据发送给目标基站1。
步骤504，UE1与目标基站1间进行同步。
UE1根据为UE1分配的无线资源信息，与目标基站1进行无线同步。
步骤505，UE1向目标基站1发送RRC重配置完成消息。相应的，目标基站1接收该RRC重配置完成消息。
该步骤505之后，在上行方向，UE1可以向目标基站1发送上行数据，目标基站1将从UE1收到的上行数据发送给源UPF1，再由源UPF1根据UPF2的Nx隧道信息，向UPF2发送UE1的上行数据。在下行方向，UPF2将UE1的下行数据发送给源UPF1，源UPF1将UE1的下行数据发送给源基站1，源基站1再经过源基站1与目标基站1之间的转发隧道，将UE1的下行数据发送给目标基站1，并由目标基站1将UE1的下行数据发送给UE1。
步骤506，目标基站1向AMF发送路径切换请求消息(PATH SWITCH REQUEST)。相应的，AMF接收该路径切换请求消息。
该路径切换请求消息包括目标基站1的N3隧道信息。
步骤507，AMF向SMF发送会话修改请求消息。相应的，SMF接收该会话修改请求消息。
该会话修改请求消息包括目标基站1的N3隧道信息，该会话修改请求消息用于通知SMF该UE1发生了切换。
可选的，会话修改请求消息可以是Nsmf_PDUSession_SMContextUpdate Request消息。
步骤508a，SMF选择与目标基站1部署在同一卫星的目标UPF1作为UE1的新UPF， 并向目标UPF1发送N4会话修改请求消息。相应的，目标UPF1接收该N4会话修改请求消息。
该N4会话修改消息包括目标基站1的N3隧道信息和UPF2的Nx隧道信息。
步骤508b，目标UPF1向SMF发送N4会话修改响应消息。相应的，SMF接收该N4会话修改响应消息。
该N4会话修改响应消息包括目标UPF1的N3隧道信息和目标UPF1的Nx隧道信息。
步骤509，SMF向AMF发送会话修改响应消息。相应的，AMF接收该会话修改响应消息。
该会话修改响应消息包括目标UPF1的N3隧道信息。
可选的，会话修改响应消息可以是Nsmf_PDUSession_SMContextUpdate Response消息。
步骤510，AMF向目标基站1发送路径切换响应消息。相应的，目标基站1接收该路径切换响应消息。
该路径切换响应消息包括目标UPF1的N3隧道信息。
此时，上行方向，目标基站1将UE1的上行数据直接发送给目标UPF1，由目标UPF1发送给UPF2。
可选的，路径切换响应消息可以是PATH SWITCH REQUEST ACK消息。
步骤511，SMF向UPF2发送N4会话更新请求消息。相应的，UPF2接收该N4会话更新请求消息。
该N4会话更新请求消息包括结束标记(End Marker)指示和目标UPF1的Nx隧道信息。
该End Marker指示用于指示UPF2通过源路径(即向源UPF1)发送End Marker。UPF2根据该End Marker指示，向源UPF1发送End Marker。源UPF1将End Marker发送给源基站1，并由源基站1转发给目标基站1。End Marker是目标基站1从目标基站1与源基站1之间的转发隧道上收到的UE1的最后一个下行数据包。目标基站1在收到End Marker前暂时缓存从目标UPF1收到的UE1的下行数据。目标基站1在收到End Marker后，可将从目标UPF1收到的数据发送给UE1。
在步骤511之后，UPF2开始将发送给UE1的下行数据包发送给目标UPF1，并由目标UPF1直接发送给目标基站1。
根据上述方案，可以避免在切换过程中UE通过源路径(源UPF1)接收的数据比通过目标路径(目标UPF1)接收的数据晚到而导致的乱序问题。
在上述图5所示的切换流程中，由于AMF和SMF位于地面，因此步骤506、508a、508b、510和511均为星地间通信，这增加了星地通信信令，并且使得流程的时延变长，需要依靠卫星间转发避免丢包，存在卫星间绕行，这不仅仅增加了时延，也增加了卫星间链路的负荷。
参考图5，针对UE1，在下行方向，在步骤503之前，卫星3的UPF2将UE1的下行数据发送给卫星1的源UPF1，源UPF1将UE1的下行数据发送给卫星1的源基站1，然后源基站1将UE1的下行数据发送给卫星2的目标基站1，也即UPF2是经由源UPF1、源基站1，将UE1的下行数据转发给目标基站1，由于目标基站1与源UPF1、源基站1不在同一颗卫星上，因此下行数据存在星间绕行，也即由卫星3发送给卫星2的数据，需要经由卫星1转发给卫星2。在上行方向，在步骤505之后、步骤506之前，UE1将UE1 的上行数据发送至卫星2的目标基站1，然后目标基站1将UE1的上行数据发送给卫星1的源UPF1，再由源UPF1发送给卫星3的UPF2，由于源UPF1与目标基站1不在同一颗卫星上，因此上行数据也存在星间绕行，也即由卫星2发送给卫星3的数据，需要经由卫星1转发给卫星3。
因此，本申请实施例后续将对上述图5所示的切换流程进行优化，以便减少切换过程中发生的星地间的信令，以及减少数据在卫星间的绕行。
在卫星场景下，通信两端的UE同时发生跨卫星切换的概率也较高。参考图6，为本申请实施例提供的一种切换方法的流程示意图。该流程中，UE1的卫星发生切换，切换前，由卫星1上的源基站1和源UPF1为UE1提供服务，切换后，由卫星2上的目标基站1和目标UPF1为UE1提供服务。UE2的卫星也发生切换，切换前，由卫星3上的源基站2和源UPF2为UE2提供服务，切换后，由卫星4上的目标基站2和目标UPF2为UE2提供服务。该流程中，UE1的切换流程的步骤描述可参见图5。该图6的切换流程与图5的切换流程所不同的是：在UE1发生切换的过程中UE2也发生了切换，其中，UE2的切换流程与UE1的切换流程类似。因此，在UE1的切换流程的任何时刻，SMF都可能收到UE2的目标UPF2的Nx隧道信息。类似的，在UE2的切换过程的任意时刻，SMF也可能收到UE1的目标UPF1的Nx隧道信息。
参考上述图6，当UE1与UE2同时发生跨卫星切换时，由于UE1与UE2分别对应的UPF都发生变化，可能会出现丢包或数据包乱序的问题，例如，在步骤608a中，SMF将UE2的源UPF2的Nx隧道信息发送给了UE1的目标UPF1，若SMF在步骤608a之后收到UE2的目标UPF2的Nx隧道信息，将导致UE1的目标UPF1无法获得UE2的目标UPF2的Nx隧道信息，目标UPF1的数据仍然发送给UE2的源UPF2。此时，若发送结束标记(End Marker)的顺序不恰当，会导致UE2的源UPF2在收到End Marker后仍然收到源UPF1或目标UPF1发送的数据包，导致这些在End Marker之后到达源UPF2的数据包被丢弃。其中，End Marker可以理解为发送给源UPF2的最后一个数据包。
因此，本申请实施例后续将对上述图6所示的切换流程进行优化，以尽量避免通信两端UE同时发生跨卫星切换时所产生的丢包或数据包乱序的问题。
图7(a)为本申请实施例提供的一种切换方法的流程示意图。该流程中，UE1的卫星发生切换，切换前，由卫星1上的源基站1和源UPF1为UE1提供服务，切换后，由卫星2上的目标基站1和目标UPF1为UE1提供服务。UE2的卫星没有发生切换，为该UE2提供服务的是卫星3上的基站2和UPF2。
该方法包括以下步骤：
步骤701a，源基站1向源UPF1发送切换准备请求消息，该切换准备请求消息包括UE1的会话的标识。
该切换准备请求消息用于指示源UPF1为UE1的跨卫星切换做准备。本申请实施例对该切换准备请求消息的名称不做限定，该消息也可以有其它名称。步骤702a，源UPF1向源基站1发送切换准备响应消息，该切换准备响应消息包括该会话对应的UPF2的Nx隧道信息。
该切换准备响应消息是对上述切换准备请求消息的响应。
可选的，该UPF2的Nx隧道信息包含在UE1的会话的上下文中，该会话的上下文还包括SMF的会话端点标识、该会话对应的包检测规则、SMF的标识信息中的至少一项， SMF的会话端点标识用于在SMF中标识会话，该会话对应的包检测规则用于目标UPF1处理UE1的上行数据包和/或下行数据包。
可选的，当该UE1的会话对应于LAN群组，则该切换准备响应消息还包括LAN群组对应的包检测规则，LAN群组对应的包检测规则用于目标UPF1处理发送给LAN群组中除UE1之外的其他UE的数据包。
步骤703a，源基站1向目标基站1发送UPF2的Nx隧道信息。
可选的，如果UPF2的Nx隧道信息包含在UE1的会话的上下文中，则该步骤703a具体是：源基站1向目标基站1发送UE1的会话的上下文。
可选的，该步骤703a之后，目标基站1还向源基站1发送目标基站1为UE1的会话分配的无线资源信息，以便源基站1向UE1发送该无线资源信息，从而UE1根据该无线资源信息，建立与目标基站1之间的空口连接，实现UE1从源基站1切换至目标基站1。
可选的，该步骤703a之后，目标基站1还向源基站1发送UE1的会话对应的目标基站1的转发隧道信息，从而源基站1可以根据该转发隧道信息，向目标基站1发送UE1的下行数据。
步骤704a，目标基站1向目标UPF1发送UPF2的Nx隧道信息。
UPF2是与UE1通信的UE2的会话对应的UPF。该UPF2的Nx隧道信息用于目标UPF1向UPF2发送UE2的下行数据。其中，UE2的下行数据指的是发送给UE2的数据。
可选的，如果UPF2的Nx隧道信息包含在UE1的会话的上下文中，则该步骤704a具体是：目标基站1向目标UPF1发送UE1的会话的上下文。
可选的，该步骤704a中，目标基站1还向目标UPF1发送目标基站1的N3隧道信息，目标基站1的N3隧道信息用于目标UPF1向目标基站1发送UE1的下行数据。其中，UE1的下行数据指的是发送给UE1的数据。
步骤705a，目标UPF1向目标基站1发送指示UE1的UPF发生切换的信息，该信息包括目标UPF1的Nx隧道信息。
该目标UPF1的Nx隧道信息是由目标UPF1分配的。该目标UPF1的Nx隧道信息用于UPF2向目标UPF1发送UE1的下行数据。
可选的，该指示UE1的UPF发生切换的信息还包括目标UPF1的会话端点标识，目标UPF1的会话端点标识用于在目标UPF1中标识会话。其中，目标UPF1的会话端点标识由目标UPF1为该会话分配。
可选的，该指示UE1的UPF发生切换的信息包含在一个N4容器中发送给目标基站1，目标基站1不感知该N4容器的内容。
可选的，该步骤705a中，目标UPF1还向目标基站1发送目标UPF1的N3隧道信息，目标UPF1的N3隧道信息用于目标基站1向目标UPF1发送UE1的上行数据。其中，UE1的上行数据是指UE1发送的数据。
步骤706a，目标基站1向SMF发送指示UE1的UPF发生切换的信息。
作为一种实现方法，目标基站1向SMF或经由AMF向SMF发送指示UE1正在进行切换的消息，该消息包括指示UE1的UPF发生切换的信息。
当指示UE1的UPF发生切换的信息携带于一个N4容器中发送给SMF，则SMF可以感知该N4容器中的内容。
步骤707a，SMF向UPF2发送目标UPF1的Nx隧道信息，以更新UPF2中的UE1的 UPF信息。
如果UPF2中没有存储UE1的UPF的Nx隧道信息，则这里的“更新UPF2中的UE1的UPF信息”指的是在UPF2中存储该UE1的UPF的Nx隧道信息。如果UPF2中已经存储UE1的UPF的Nx隧道信息，则这里的“更新UPF2中的UE1的UPF信息”指的是将UPF2中当前存储的UE2的UPF的Nx隧道信息，替换为该重新收到的目标UPF1的Nx隧道信息。
该目标UPF1的Nx隧道信息用于UPF2向目标UPF1发送UE1的下行数据。其中，UE1的下行数据指的是发送给UE1的数据。
可选的，如果UE1的SMF与UE2的SMF不同，则UE1的SMF通过UE2的SMF向UPF2发送目标UPF1的Nx隧道信息。
可选的，在步骤707a之后，SMF还向UPF2发送End Marker指示，该End Marker指示用于指示UPF2向源UPF1发送End Marker。如果UE1的SMF与UE2的SMF不同，则UE1的SMF向UE2的SMF发送End marker指示，然后UE2的SMF向UPF2发送End Marker指示。
根据上述方案，当UE1发生切换，源UPF在切换之前的准备阶段将源UPF的会话的上下文信息(其中包括UE2的UPF的Nx隧道信息)发送给目标UPF，避免由SMF向目标UPF发送UE2的UPF的Nx隧道信息，可以减少SMF与目标UPF之间的星地交互，从而减少数据传输时延以及切换时延。
图7(b)为本申请实施例提供的一种切换方法的流程示意图。该实施例可以应用于UE1和UE2同时跨卫星切换的场景(例如，由于卫星移动导致该场景的发生)。该流程中，UE1的卫星发生切换，切换前，由卫星1上的源基站1和源UPF1为UE1提供服务，切换后，由卫星2上的目标基站1和目标UPF1为UE1提供服务。UE2的卫星也发生切换，切换前，由卫星3上的源基站2和源UPF2为UE2提供服务，切换后，由卫星4上的目标基站2和目标UPF2为UE2提供服务。
该方法包括以下步骤：
步骤701b，源基站1向源UPF1发送切换准备请求消息，该切换准备请求消息包括UE1的会话的标识。
步骤702b，源UPF1向源基站1发送切换准备响应消息，该切换准备响应消息包括该会话对应的源UPF2的Nx隧道信息。
可选的，该源UPF2的Nx隧道信息包含在UE1的会话的上下文中，该会话的上下文还包括SMF的会话端点标识、该会话对应的包检测规则、SMF的标识信息中的至少一项，SMF的会话端点标识用于在SMF中标识会话，该会话对应的包检测规则用于目标UPF1处理UE1的上行数据包和/或下行数据包。
可选的，当该UE1的会话对应于LAN群组，则该切换准备响应消息还包括LAN群组对应的包检测规则，LAN群组对应的包检测规则用于目标UPF1处理发送给LAN群组中除UE1之外的其他UE的数据包。
步骤703b，源基站1向目标基站1发送源UPF2的Nx隧道信息。
可选的，如果源UPF2的Nx隧道信息包含在UE1的会话的上下文中，则该步骤703b具体是：源基站1向目标基站1发送UE1的会话的上下文。
可选的，该步骤703b之后，目标基站1还向源基站1发送目标基站1为UE1的会话 分配的无线资源信息，以便源基站1向UE1发送该无线资源信息，从而UE1根据该无线资源信息，建立与目标基站1之间的空口连接，实现UE1从源基站1切换至目标基站1。
可选的，该步骤703b之后，目标基站1还向源基站1发送UE1的会话对应的目标基站1的转发隧道信息，从而源基站1可以根据该转发隧道信息，向目标基站1发送UE1的下行数据。
步骤704b，目标基站1向目标UPF1发送源UPF2的Nx隧道信息。
源UPF2是与UE1通信的UE2的会话对应的UPF。该源UPF2的Nx隧道信息用于目标UPF1向源UPF2发送UE2的下行数据。其中，UE2的下行数据指的是发送给UE2的数据。
可选的，如果源UPF2的Nx隧道信息包含在UE1的会话的上下文中，则该步骤704b具体是：目标基站1向目标UPF1发送UE1的会话的上下文。
可选的，该步骤704b中，目标基站1还向目标UPF1发送目标基站1的N3隧道信息，目标基站1的N3隧道信息用于目标UPF1向目标基站1发送UE1的下行数据。其中，UE1的下行数据指的是发送给UE1的数据。
步骤705b，目标UPF1向目标基站1发送指示UE1的UPF发生切换的信息，该信息包括目标UPF1的Nx隧道信息。
该目标UPF1的Nx隧道信息是由目标UPF1分配的。该目标UPF1的Nx隧道信息用于UE2的UPF向目标UPF1发送UE1的下行数据。
可选的，该指示UE1的UPF发生切换的信息还包括目标UPF1的会话端点标识，目标UPF1的会话端点标识用于在目标UPF1中标识会话。其中，目标UPF1的会话端点标识由目标UPF1为该会话分配。
可选的，该指示UE1的UPF发生切换的信息包含在一个N4容器中发送给目标基站1，目标基站1不感知该N4容器的内容。
可选的，该步骤705b中，目标UPF1还向目标基站1发送目标UPF1的N3隧道信息，目标UPF1的N3隧道信息用于目标基站1向目标UPF1发送UE1的上行数据。其中，UE1的上行数据是指UE1发送的数据。
步骤706b，SMF通过目标基站2接收来自目标UPF2的目标UPF2的Nx隧道信息。
此时，UE2也在发生切换，且UE2切换比UE1切换要早，因此在步骤709b之前，SMF已经收到来自目标UPF2的目标UPF2的Nx隧道信息。
步骤707b，SMF向源UPF1发送目标UPF2的Nx隧道信息以更新源UPF1中的UE2的UPF信息。
步骤708b，源UPF1向SMF发送拒绝更新的响应消息。
SMF收到来自目标UPF2的目标UPF2的Nx隧道信息时，还不知道UE1也在发生切换，因此SMF向源UPF1发送目标UPF2的Nx隧道信息，以更新源UPF1中的UE2的UPF信息。但源UPF1知晓UE1正在切换，因此源UPF1拒绝更新，也即向SMF发送拒绝更新的响应消息，以拒绝更新源UPF1中的UE2的UPF信息。
可选的，该拒绝更新的响应消息携带拒绝原因值，且拒绝原因值为UE1正在切换。
步骤709b，目标基站1向SMF发送指示UE1的UPF发生切换的信息。
当指示UE1的UPF发生切换的信息携带于一个N4容器中发送给SMF，则SMF可以感知该N4容器中的内容。
可选的，该步骤709b具体是：目标基站1向AMF发送指示UE1的UPF发生切换的信息，然后AMF向SMF发送会话修改请求，该会话修改请求包括指示UE1的UPF发生切换的信息。
该步骤709b之后，SMF获知UE1完成切换，且获知切换后的UPF是目标UPF1，因此可以执行以下步骤710b。
步骤710b，SMF向目标UPF1发送目标UPF2的Nx隧道信息。
可选的，由于步骤708b收到了拒绝更新的响应消息，因此在步骤710b中或之后，SMF可以向目标UPF1发送End Marker指示，目标UPF1根据End Marker指示，向源UPF2发送End Marker。
该步骤709b之后，SMF获知UE1完成切换，且获知切换后的UPF是目标UPF1，因此可以执行以下步骤711b，该步骤711b与上述步骤710b没有先后关系。
步骤711b，SMF向目标UPF2发送目标UPF1的Nx隧道信息。
可选的，在步骤711b中或之后，SMF向目标UPF2发送End Marker指示，目标UPF2根据End Marker指示，向源UPF1发送End Marker。
根据上述方案，当UE1和UE2同时发生切换，SMF在收到UE2的更新后的目标UPF2的Nx隧道信息，且不知道UE1正在发生切换，则SMF向UE1的源UPF1发送目标UPF2的Nx隧道信息，SMF收到源UPF2的拒绝更新的响应消息后，获知UE1正在发生切换，则SMF在后续收到指示UE1的UPF发生切换的信息后，再向UE1的切换后的目标UPF1发送UE2的更新后的目标UPF2的Nx隧道信息，从而保证了切换的正常完成。
图7(c)为本申请实施例提供的一种切换方法的流程示意图。该实施例可以应用于UE1和UE2同时跨卫星切换的场景(例如，由于卫星移动导致该场景的发生)。该流程中，UE1的卫星发生切换，切换前，由卫星1上的源基站1和源UPF1为UE1提供服务，切换后，由卫星2上的目标基站1和目标UPF1为UE1提供服务。UE2的卫星也发生切换，切换前，由卫星3上的源基站2和源UPF2为UE2提供服务，切换后，由卫星4上的目标基站2和目标UPF2为UE2提供服务。
该方法包括以下步骤：
步骤701c至步骤705c，同上述步骤701b至步骤705b，可参考前述描述。
步骤706c，目标基站1向SMF发送指示UE1的UPF发生切换的信息。
作为一种实现方法，目标基站1向SMF或经由AMF向SMF发送指示UE1正在进行切换的消息，该消息包括指示UE1的UPF发生切换的信息。
当指示UE1的UPF发生切换的信息携带于一个N4容器中发送给SMF，则SMF可以感知该N4容器中的内容。
步骤707c，SMF通过目标基站2接收来自目标UPF2的目标UPF2的Nx隧道信息。
SMF收到来自目标UPF2的目标UPF2的Nx隧道信息时，已经通过上述步骤706c获知UE1也在发生切换，且获知UE1切换后的UPF是目标UPF1，因此SMF向目标UPF1发送目标UPF2的Nx隧道信息，也即执行以下步骤708c。
步骤708c，SMF向目标UPF1发送目标UPF2的Nx隧道信息。
可选的，在步骤708c中或之后，SMF向目标UPF1发送End Marker指示，目标UPF1根据End Marker指示，向源UPF2发送End Marker。
可选的，在步骤707c之后，还执行以下步骤709c，该步骤709c与上述步骤708c没 有先后关系。
步骤709c，SMF向目标UPF2发送目标UPF1的Nx隧道信息。
可选的，在步骤709c中或之后，SMF向目标UPF2发送End Marker指示，目标UPF2根据End Marker指示，向源UPF1发送End Marker。
根据上述方案，当UE1和UE2同时发生切换，SMF在收到UE2的更新后的目标UPF2的Nx隧道信息，且已经获知UE1发生切换后的目标UPF1的信息，则SMF向UE1的目标UPF1发送目标UPF2的Nx隧道信息，从而保证了切换的正常完成。
图7(d)为本申请实施例提供的一种切换方法的流程示意图。该实施例可以应用于UE1和UE2同时跨卫星切换的场景(例如，由于卫星移动导致该场景的发生)。该流程中，UE1的卫星发生切换，切换前，由卫星1上的源基站1和源UPF1为UE1提供服务，切换后，由卫星2上的目标基站1和目标UPF1为UE1提供服务。UE2的卫星也发生切换，切换前，由卫星3上的源基站2和源UPF2为UE2提供服务，切换后，由卫星4上的目标基站2和目标UPF2为UE2提供服务。
该方法包括以下步骤：
步骤701d至步骤705d，同上述步骤701b至步骤705b，可参考前述描述。
步骤706d，SMF通过目标基站2接收来自目标UPF2的目标UPF2的Nx隧道信息。
此时，UE2也在发生切换，且UE2切换比UE1切换要早，因此在步骤705d之后，SMF已经收到来自目标UPF2的目标UPF2的Nx隧道信息。
步骤707d，SMF向源UPF1发送目标UPF2的Nx隧道信息以更新源UPF1中的UE2的UPF信息。
SMF收到来自目标UPF2的目标UPF2的Nx隧道信息时，还不知道UE1也在发生切换，因此SMF向源UPF1发送目标UPF2的Nx隧道信息，以更新源UPF1中的UE2的UPF信息。
可选的，该步骤706d之后，SMF向源UPF2发送End Marker指示，End Marker指示用于指示源UPF2向源基站2发送End Marker。源UPF2向源基站2发送End Marker。
步骤708d，目标基站1向SMF发送指示UE1的UPF发生切换的信息。
当指示UE1的UPF发生切换的信息携带于一个N4容器中发送给SMF，则SMF可以感知该N4容器中的内容。
可选的，该步骤708d具体是：目标基站1向AMF发送指示UE1的UPF发生切换的信息，然后AMF向SMF发送会话修改请求，该会话修改请求包括指示UE1的UPF发生切换的信息。
步骤709d，SMF向目标UPF1发送目标UPF2的Nx隧道信息。
作为一种实现方法，SMF还收到目标UPF1经由上述步骤705d和步骤708d发送的UE2的UPF的Nx隧道信息，其中，目标UPF1是从源UPF1收到的该UE2的UPF的Nx隧道信息，则该步骤709d具体是：SMF确定若来自目标UPF1的UE2的UPF的Nx隧道信息与SMF保存的UE2的UPF的Nx隧道信息不同，则SMF向目标UPF1发送目标UPF2的Nx隧道信息。比如，来自目标UPF1的UE2的UPF的Nx隧道信息是源UPF2的Nx隧道信息，SMF保存的UE2的UPF的Nx隧道信息是目标UPF2的Nx隧道信息，因此SMF确定来自目标UPF1的UE2的UPF的Nx隧道信息与SMF保存的UE2的UPF的Nx隧道信息不同，进而SMF向目标UPF1发送目标UPF2的Nx隧道信息。
该步骤708d之后，SMF获知UE1完成切换，且获知切换后的UPF是目标UPF1，因此可以执行以下步骤710d，该步骤710d与上述步骤709d没有先后关系。
步骤710d，SMF向目标UPF2发送目标UPF1的Nx隧道信息。
可选的，在步骤710d之后，SMF向源UPF1发送End Marker指示，End Marker指示用于指示源UPF1向源基站1发送End Marker。源UPF1根据End Marker指示，向源基站1发送End Marker。
根据上述方案，当UE1和UE2同时发生切换，SMF在收到UE2的更新后的目标UPF2的Nx隧道信息，且不知道UE1正在发生切换，则SMF向UE1的源UPF1发送目标UPF2的Nx隧道信息以更新源UPF1中的UE2的UPF信息，源UPF2接受更新，后续向目标UPF2发送UE2的下行数据，而不是向源UPF2发送UE2的下行数据。SMF在后续收到指示UE1的UPF发生切换的信息后，再向UE1的切换后的目标UPF1发送UE2的更新后的目标UPF2的Nx隧道信息，从而保证了切换的正常完成。
图7(e)为本申请实施例提供的一种切换方法的流程示意图。该实施例可以应用于UE1和UE2同时跨卫星切换的场景(例如，由于卫星移动导致该场景的发生)。该流程中，UE1的卫星发生切换，切换前，由卫星1上的源基站1和源UPF1为UE1提供服务，切换后，由卫星2上的目标基站1和目标UPF1为UE1提供服务。UE2的卫星也发生切换，切换前，由卫星3上的源基站2和源UPF2为UE2提供服务，切换后，由卫星4上的目标基站2和目标UPF2为UE2提供服务。
该方法包括以下步骤：
步骤701e至步骤705e，同上述步骤701b至步骤705b，可参考前述描述。
步骤706e，目标基站1向SMF发送指示UE1的UPF发生切换的信息。
作为一种实现方法，目标基站1向SMF或经由AMF向SMF发送指示UE1正在进行切换的消息，该消息包括指示UE1的UPF发生切换的信息。
当指示UE1的UPF发生切换的信息携带于一个N4容器中发送给SMF，则SMF可以感知该N4容器中的内容。
步骤707e，SMF通过目标基站2接收来自目标UPF2的目标UPF2的Nx隧道信息。
SMF收到来自目标UPF2的目标UPF2的Nx隧道信息时，已经通过上述步骤706e获知UE1也在发生切换，且获知UE1切换后的UPF是目标UPF1，因此SMF向目标UPF1发送目标UPF2的Nx隧道信息，也即执行以下步骤708e。以及还执行以下步骤709e，且步骤708e与步骤709e没有先后时序限制。
步骤708e，SMF向目标UPF1发送目标UPF2的Nx隧道信息。
步骤709e，SMF向源UPF1发送目标UPF2的Nx隧道信息。
可选的，在步骤709e之后，SMF向源UPF2发送End Marker指示，End Marker指示用于指示源UPF2向源基站2发送End Marker。源UPF2根据End Marker指示，向源基站2发送End Marker。
可选的，在步骤706e之后，还执行以下步骤710e，该步骤710e与上述步骤708e、步骤709e之间没有先后关系。
步骤710e，SMF向目标UPF2发送目标UPF1的Nx隧道信息。
可选的，在步骤710e之后，SMF向源UPF1发送End Marker指示，End Marker指示用于指示源UPF1向源基站1发送End Marker。源UPF1根据End Marker指示，向源基站 1发送End Marker。
根据上述方案，当UE1和UE2同时发生切换，SMF在收到UE2的更新后的目标UPF2的Nx隧道信息，且已经获知UE1发生切换后的目标UPF1的信息，则SMF向UE1的目标UPF1和源UPF1均发送目标UPF2的Nx隧道信息，以保证了切换的正常完成。
图7(f)为本申请实施例提供的一种切换方法的流程示意图。该实施例可以应用于UE1和UE2同时跨卫星切换的场景(例如，由于卫星移动导致该场景的发生)。该流程中，UE1的卫星发生切换，切换前，由卫星1上的源基站1和源UPF1为UE1提供服务，切换后，由卫星2上的目标基站1和目标UPF1为UE1提供服务。UE2的卫星也发生切换，切换前，由卫星3上的源基站2和源UPF2为UE2提供服务，切换后，由卫星4上的目标基站2和目标UPF2为UE2提供服务。
该方法包括以下步骤：
步骤701f，SMF接收来自目标UPF2的目标UPF2的Nx隧道信息。
该目标UPF2可以是SMF为UE2选择的、切换后的目标UPF。
具体的，SMF可以从目标UPF2接收目标UPF2的Nx隧道信息。
可选的，在步骤701f之前，SMF接收到指示UE2发生切换的信息，然后SMF向目标UPF2发送源UPF1的Nx隧道信息。
步骤702f，SMF接收指示UE1发生切换的信息。
SMF根据指示UE1发生切换的信息，确定UE1正在发生切换。
可选的，指示UE1发生切换的信息可以是用于为UE1选择UPF的信息，或者是目标UPF1的标识信息。
可选的，指示UE1发生切换的信息可以包含于会话修改请求消息中发送至SMF，SMF从该会话修改请求消息中获取指示UE1发生切换的信息。
需要说明的是，上述步骤701f和步骤702f之间没有先后执行顺序。
步骤703f，SMF向源UPF1发送目标UPF2的Nx隧道信息，以更新源UPF1中的UE2的UPF信息。
当SMF收到UE2的目标UPF2的Nx隧道信息时，UE1也在发生切换且切换还未完成，则SMF先将UE2的目标UPF2的Nx隧道信息发送给UE1的源UPF1，以更新UE1的源UPF1中的UE2的UPF信息。
可选的，在步骤703f的同时或之后，SMF还向源UPF1发送结束标记指示，结束标记指示用于指示源UPF1向源UPF2发送结束标记。
步骤704f，SMF向目标UPF1发送目标UPF2的Nx隧道信息。
可选的，在步骤702f之后，SMF可以向目标基站1发送目标UPF1的N3隧道信息。从而目标基站1可以根据目标UPF1的N3隧道信息，向目标UPF1发送数据。
根据上述方案，当UE2完成切换且SMF收到UE2的切换后的目标UPF的Nx隧道信息，若此时UE1也在发生切换，且UE1的切换还未完成，则SMF先将UE2的目标UPF2的Nx隧道信息发送给UE1的源UPF1，从而源UPF1可以开始向目标UPF2发送数据。一方面，可以保证正常完成切换，另一方面，由于将UPF的Nx隧道信息的更新与UE的UPF的切换进行解耦，可以避免由于UPF的Nx隧道信息的更新与UE的UPF的切换的同时进行而导致的数据包丢失或乱序。
参考图8，为本申请实施例提供的一种切换方法的流程示意图。该流程中，UE1的卫 星发生切换，切换前，由卫星1上的源基站1和源UPF1为UE1提供服务，切换后，由卫星2上的目标基站1和目标UPF1为UE1提供服务。UE2的卫星没有发生切换，为该UE2提供服务的是卫星3上的基站2和UPF2。该图8的实施例是对上述图5的实施例的改进。该图8对应的实施例也是上述图7(a)的实施例的一种具体实现。
该流程包括以下步骤：
步骤801，UE1即将移出源基站1的覆盖范围，源基站1决定将UE1切换到目标基站1，则源基站1向源UPF1发送切换准备请求消息。相应的，源UPF1接收该切换准备请求消息。
该切换准备请求消息用于指示源UPF1为UE1的跨卫星切换做准备。
若UE1建立了1个PDU会话，该步骤801执行1次，该切换准备请求消息包括该PDU会话的标识。
若UE1建立了多个PDU会话，该步骤801可以执行1次或多次。即，源基站1可以针对每个PDU会话向源UPF1发送一条切换准备请求消息，该切换准备请求消息包括一个PDU会话的标识。或者，源基站1为该UE的多个PDU会话发送一条切换准备请求消息，该切换准备请求消息包括该UE1的多个PDU会话的标识。也即切换准备请求消息可以是UE粒度，也可以是PDU会话粒度。
步骤802，源UPF1向源基站1发送切换准备响应消息。相应的，源基站1接收该切换准备响应消息。
该切换准备响应消息包括UE1的PDU会话在该源UPF1中的上下文信息。
其中，如果源基站1针对每个PDU会话发送一条切换准备请求消息，则源UPF1针对每个切换准备请求消息，发送一条切换准备响应消息，该切换准备响应消息包括一个PDU会话的上下文信息。例如，源基站1向源UPF1发送了切换准备请求消息1，其中包括PDU会话1的标识，以及向源UPF1发送了切换准备请求消息2，其中包括PDU会话2的标识，则源UPF1向源基站1发送针对切换准备请求消息1的切换准备响应消息1，其中包括PDU会话1的上下文信息，以及向源基站1发送针对切换准备请求消息2的切换准备响应消息2，其中包括PDU会话2的上下文信息。
如果源基站1针对UE1的多个PDU会话发送一条切换准备请求消息，则源UPF1向源基站1发送一条切换准备响应消息，该切换准备响应消息包括UE1的多个PDU会话的上下文信息。其中，每个PDU会话对应一个PDU会话的上下文信息。
其中，每个PDU会话的上下文信息包括该PDU会话的标识和该PDU会话对应的所有包检测规则(Packet Detection Rule，PDR)。其中，所述PDR包括上行PDR和下行PDR，上行PDR用于确定收到的上行数据包的发送方式，下行PDR用于确定收到的下行数据包的发送方式。上行PDR包括UPF2的Nx隧道信息，或当该PDU会话为5G局域网(Local Area Network，LAN)会话时上行PDR指示将收到的上行数据包发送给5G LAN内部接口。下行PDR包括该PDU会话对应的QoS流的信息(例如，QoS流标识(QoS flow identity，QFI)和QoS流描述信息(用于目标UPF确定下行数据包对应的QFI))。
若该PDU会话是5G LAN会话，则PDU会话的下行PDR的源接口(Source Interface)为5G LAN内部接口，该PDR的源网络实例(Network Instance)设置为该5G LAN的标识，PDU会话的上行PDR的目的接口(Destination Interface)为5G LAN内部接口，该上行方向PDR的目的网络实例(Network Instance)设置为该5G LAN的标识，即，从该PDU 会话收到的上行数据包发送到该5G LAN的内部接口。
若该PDU会话是5G LAN会话，该切换准备响应消息还包括5G LAN会话的上下文信息，该5G LAN会话的上下文信息包括5G LAN群组级别的上行PDR，该上行PDR的源接口(Source Interface)是5G LAN内部接口(VN Internal)，该上行PDR的源网络实例(Network Instance)设置为该5G LAN的标识，该PDR中包括地址信息，该PDR用于将目的地址为该PDR中所包括的地址的数据包通过Nx隧道发送给UPF2。该5G LAN会话的上下文信息中还包括5G LAN群组级别的下行PDR，该下行PDR的目的接口(Destination Interface)为5G LAN内部接口(VN Internal)，该下行PDR的目的网络实例(Network Instance)设置为该5G LAN的标识，该下行PDR用于指示将从Nx隧道收到的数据包发送到该5G LAN的内部接口。
PDU会话的PDR和5G LAN群组级别的PDR用于目标UPF1处理上下行数据包。
可选的，PDU会话的上下文信息还包括：N4会话信息，例如，该PDU会话对应的SMF的F-SEID和/或SMF的Node ID。其中，该SMF的F-SEID用于在SMF中唯一标识该PDU会话，F-SEID是完全限定会话端点标识(Fully Qualified Session Endpoint Identifier)的简称。
源UPF1可以将UE1的每个PDU会话的上下文信息分别封装在一个上下文容器中，源基站1可以不用理解容器中的内容。该切换准备响应消息中包括一个或多个(PDU会话的标识，PDU会话对应的上下文容器)。
步骤803，源基站1向目标基站1发送切换请求消息。相应的，目标基站1接收该切换请求消息。
该切换请求消息中包括每个PDU会话的标识和该PDU会话对应的上下文容器，或者理解为该切换请求消息包括一个或多个(PDU会话的标识，PDU会话对应的上下文容器)。其中，这里的(PDU会话的标识，PDU会话对应的上下文容器)表示PDU会话的标识与该PDU会话对应的上下文容器构成的一个组合，因此一个或多个(PDU会话的标识，PDU会话对应的上下文容器)表示一个或多个组合，每个组合包括一个PDU会话的标识以及该PDU会话对应的上下文容器，这里做统一描述，后续不再赘述。
步骤804，目标基站1向位于同一卫星的目标UPF1发送切换准备请求消息。相应的，目标UPF1接收该切换准备请求消息。
该切换准备请求消息包括UE1的PDU会话的上下文信息，作为一种具体实现方法，该切换准备请求消息包括UE1的至少一个PDU会话的标识和该PDU会话对应的上下文容器。
以及，该切换准备请求消息还包括UE1的至少一个PDU会话对应的目标基站1的N3隧道信息，该N3隧道用于目标基站1接收该PDU会话的数据。比如，目标基站1确定收到的切换请求消息中包括了PDU会话对应的上下文容器，则目标基站1为该PDU会话分配一个N3隧道信息，并在切换准备请求消息中携带该PDU会话的标识，该PDU会话的上下文容器以及该PDU会话对应的目标基站1的N3隧道信息。或者，源基站1在切换请求消息中指示目标基站1哪些PDU会话需要创建到目标UPF1的N3隧道(源基站1知道哪些PDU会话由源UPF1提供服务)，则目标基站1为这些PDU会话分配N3隧道，并在切换准备请求消息中携带该PDU会话的标识，该PDU会话的上下文容器以及该PDU会话对应的目标基站1的N3隧道信息。因此，切换准备请求消息可以包括一个或多个(PDU 会话的标识、上下文容器、目标基站1的N3隧道信息)。
步骤805，目标UPF1向目标基站1发送切换准备响应消息。相应的，目标基站1接收该切换准备响应消息。
目标UPF1收到切换准备请求消息后，保存PDU会话的标识、该PDU会话的上下文信息以及该PDU会话对应的目标基站1的N3隧道信息。
该切换准备响应消息中包括UE1的PDU会话对应的目标UPF1的N3隧道信息和每个PDU会话对应的N4容器。作为一种实现方法，该切换准备响应消息的格式如下：切换准备响应消息包括一个或多个(PDU会话的标识、N4容器、目标UPF1的N3隧道信息)。
目标UPF1的N3隧道信息是发送给目标基站1的，N4容器是发送给SMF的。
其中，目标UPF1为每个PDU会话分配目标UPF1的N3隧道信息，该N3隧道信息用于接收来自目标基站1的该PDU会话的数据，每个PDU会话分配目标UPF1的N3隧道信息携带于切换准备响应消息中发送给目标基站1。由于目标UPF1在步骤804收到了每个PDU会话对应的目标基站1的N3隧道信息，以及在该步骤805中目标基站1可以收到每个PDU会话对应的目标UPF1的N3隧道信息，从而在目标基站1与目标UPF1之间建立了每个PDU会话对应的N3隧道，该N3隧道用于传输该PDU会话的数据。当UE1成功与目标基站1建立连接后，UE1发送的上行数据可通过该N3隧道直接发送给目标UPF1，避免通过源UPF1绕行。需要说明的是，N3隧道是PDU会话粒度，即每个PDU对应一个N3隧道。
每个PDU会话对应的N4容器内封装有N4消息，示例性的，该N4消息也可以是PFCP会话修改请求消息，该PFCP会话修改请求消息是由目标UPF1为该PDU会话生成的，用于通知SMF：该PDU会话对应的UPF发生了切换。该PFCP会话修改请求消息中包括该PDU会话对应的N4会话信息(例如，SMF的F-SEID和/或SMF的Node ID，其中该SMF的F-SEID用于在SMF中唯一标识该PDU会话)、目标UPF1的N4接口信息(例如，目标UPF1的F-SEID和/或目标UPF1的Node ID等，其中，目标UPF1的F-SEID用于在目标UPF1中唯一标识该会话)以及包括目标UPF1为该PDU会话分配的目标UPF1的Nx隧道信息，该目标UPF1的Nx隧道信息将会发送给UPF2，用于UPF2根据该目标UPF1的Nx隧道信息，向目标UPF1发送UE2需要发送给UE1的数据。可选的，该PFCP会话修改请求消息中还可以包括该PDU会话对应的目标UPF1的N3隧道信息。可选的，该PFCP会话修改请求消息中还可以包括该PDU会话对应的目标基站1的N3隧道信息。
步骤806，目标基站1向源基站1发送切换响应消息。相应的，源基站1接收该切换响应消息。
目标基站1从上述步骤805的切换准备响应消息中获取到UE1的每个PDU会话对应的目标UPF1的N3隧道信息，并保存该目标UPF1的N3隧道信息。
以及，目标基站1还向源基站1发送切换响应消息，其中包括UE1的PDU会话的标识。
以及，该切换响应消息中还可以包括目标基站1为UE1的每个PDU会话分配的无线资源信息。
可选的，切换响应消息中还可以包括目标基站1的转发隧道信息，该转发隧道信息用于源基站1将收到的发往UE1的数据转发给目标基站1。如此，从UE2发送给UE1的数据可以经过该目标基站1的转发隧道到达目标基站1，从UE2发送给UE1的数据的路径为： UE2->基站2->UPF2->源UPF1->源基站1->目标基站1。由于此时UE1还未与目标基站1之间建立连接，因此，UE2发往UE1的数据可以暂时缓存在目标基站1中，待后续建立了目标基站1与UE1之间的连接后，目标基站1可以将缓存的数据发给UE1。
步骤807，源基站1向UE1发送切换命令。相应的，UE1接收该切换命令。
其中，当源基站1收到步骤806的切换响应消息，触发源基站1向UE1发送切换命令。
该切换命令可以是一个RRC重配置消息。
该切换命令中包括目标基站1为UE1的每个PDU会话分配的无线资源信息，以便UE1根据无线资源信息配置空口。
步骤808，UE1与目标基站1进行同步。
在UE1与目标基站1进行同步之后，UE1可以通过目标基站1发送上行数据。由于目标基站1与目标UPF1间的N3隧道在切换准备阶段已经建立，目标基站1可将从UE1收到的UE1的上行数据发送给目标UPF1。并且，由于目标UPF1从源UPF1获得的PDU会话的上下文信息中包括了UE2的UPF2的Nx隧道信息，因此目标UPF1可将收到的UE1的上行数据发送给UPF2，并由UPF2通过基站2发送给UE2。即，在步骤808之后，上行路径已经切换完成。
步骤809，UE1向目标基站1发送切换完成指示。相应的，目标基站1接收该切换完成指示。
该切换完成指示可以是RRC重配置完成消息。
目标基站1在收到切换完成指示之后，可以开始向UE1发送下行数据。比如，目标基站1可以将之前缓存的需要发送给UE1的数据，发送给UE1，该缓存的数据是源基站1发送给目标基站1的。
步骤810，目标基站1向AMF发送路径切换请求消息(PATH SWITCH REQUEST)。相应的，AMF接收该路径切换请求消息。
该路径切换请求消息中包括UE1的PDU会话的标识以及每个PDU会话对应的N4容器，或者理解为该路径切换请求消息中包括一个或多个(PDU会话的标识、N4容器)。该N4容器即为上述步骤805的切换准备请求消息中的N4容器。
步骤811，AMF向SMF发送会话修改请求消息。相应的，SMF接收该会话修改请求消息。
这里的SMF指的是PDU会话对应的SMF。其中，UE1的不同PDU会话可以对应相同的SMF，也可以对应不同的SMF，本申请不限定。
该会话修改请求消息包括该PDU会话对应的N4容器。SMF根据N4容器中的N4消息执行相应的操作，例如，SMF将该PDU会话对应的UPF的Node ID替换为N4消息中的目标UPF1的Node ID，和/或SMF将该PDU会话对应的UPF的F-SEID替换为N4消息中目标UPF1的F-SEID。
并且，SMF保存N4容器中携带的目标UPF1的Nx隧道信息、目标UPF1的N3隧道信息等。
可选的，该会话修改请求消息可以是Nsmf_PDUSession_SMContextUpdate Request消息。
步骤812，SMF向UPF2发送会话修改请求消息。相应的，UPF2接收该会话修改请求消息。
该会话修改请求消息包括UE1的PDU会话对应的目标UPF1的Nx隧道信息。
SMF从N4容器中获取到UE1的PDU会话对应的目标UPF1的Nx隧道信息，并将该UE1的PDU会话对应的目标UPF1的Nx隧道信息发送给UPF2，从而UPF2将该PDU会话对应的Nx隧道信息，由该PDU会话对应的源UPF1的Nx隧道信息更新为该PDU会话对应的目标UPF1的Nx隧道信息，从而后续UPF2将收到的UE2需要发送给UE1的数据直接发送给目标UPF1，即不再经过源UPF1和源基站1绕行。
可选的，该会话修改请求消息还可以包括End Marker指示，该End Marker指示用于指示UPF2通过源路径(即向源UPF1)发送End Marker。UPF2根据该End Marker指示，通过源路径发送End Marker。UPF2开始通过新路径(即向目标UPF1)发送数据，此时，UE1的下行路径切换为：UE2->基站2->UPF2->目标UPF1->目标基站1->UE1。此时，UE1的上下行路径均切换完成。
可选的，该会话修改请求消息可以是N4会话修改请求消息，即PFCP Session ModificationRequest消息。
需要说明的是，若目标UPF1对应的SMF与UPF2对应的SMF不同，则目标UPF1对应的SMF将UE1的PDU会话对应的目标UPF1的Nx隧道信息发送给UPF2对应的SMF，然后由UPF2对应的SMF将UE1的PDU会话对应的目标UPF1的Nx隧道信息发送给UPF2。类似的，End Marker指示也由目标UPF1对应的SMF发送给UPF2对应的SMF，再由UPF2对应的SMF发送给UPF2。
步骤813，SMF向AMF发送会话修改响应消息。相应的，AMF接收该会话修改响应消息。
该会话修改响应消息包括N4容器，该N4容器包括PFCP会话修改响应消息。该N4容器是需要发送给目标UPF1的。
可选的，该会话修改响应消息可以是Nsmf_PDUSession_SMContextUpdate Response消息。
步骤814，AMF向目标基站1发送路径切换响应消息(PATH SWITCH REQUEST ACK)。相应的，目标基站1接收该路径切换响应消息。
该路径切换响应消息中包括成功切换的PDU会话的标识和该PDU会话对应的N4容器，该N4容器来自上述步骤813的会话修改响应消息。
步骤815，目标基站1向目标UPF1发送N4容器。相应的，目标UPF1接收该N4容器。
该N4容器包括PFCP会话修改响应消息。
相较于图5对应的实施例，该图8对应的实施例减少了切换过程中的星地间的信令交互(例如减少了50％的星地信令)，从而减少星地间链路的负荷和降低切换时延。并且，在准备阶段将源UPF的PDU会话的上下文信息发送给目标UPF，建立了目标基站到目标UPF之间的N3隧道，从而可以避免上行数据经过源UPF绕行，可以进一步减少数据传输时延。
参考图9，为本申请实施例提供的一种切换方法的流程示意图。该实施例可以应用于UE1和UE2同时跨卫星切换的场景(例如，由于卫星移动导致该场景的发生)。该流程中，UE1的卫星发生切换，切换前，由卫星1上的源基站1和源UPF1为UE1提供服务，切换后，由卫星2上的目标基站1和目标UPF1为UE1提供服务。UE2的卫星也发生切换，切 换前，由卫星3上的源基站2和源UPF2为UE2提供服务，切换后，由卫星4上的目标基站2和目标UPF2为UE2提供服务。该图9的实施例是对上述图6的实施例的改进。该图9对应的实施例也是上述图7(b)的实施例的一种具体实现。
该实施例可用于UE1和UE2同时跨卫星移动时导致的Nx隧道切换的时序问题。
该流程包括以下步骤：
步骤901至步骤906，同上述步骤801至步骤806。
步骤906a，SMF向源UPF1发送目标UPF2的Nx隧道信息。相应的，源UPF1接收该目标UPF2的Nx隧道信息。
在步骤906a之前，UE2也发生切换，且SMF已经收到切换后的目标UPF2的Nx隧道信息。
由于SMF还不知道UE1正在发生切换，SMF会认为UE1仍然由源UPF1服务，因此当SMF收到UE2的切换后的目标UPF2的Nx隧道信息后，将目标UPF2的Nx隧道信息发送给源UPF1。
该步骤906a可以在步骤901之后、步骤911之前的任意步骤执行。该实施例中以该步骤906a在步骤906之后、步骤907之前执行为例进行说明。其中，之所以限定该步骤906a在步骤901之后执行，是因为步骤901之后，源UPF1可以获知UE1正在切换，因此当源UPF1收到来自SMF的目标UPF1的Nx隧道信息，则源UPF1可以暂不更新UPF的Nx隧道信息，并执行以下步骤906b。之所以限定该步骤906a在步骤911之前执行，是因为SMF收到步骤911的会话修改请求消息后，可以获知UE1正在切换，则SMF可能不会执行该步骤906a，换句话说在步骤911之前SMF并不知道UE1正在切换，从而SMF会执行上述步骤906a。
可选的，该步骤906a中，SMF还可以向源UPF1发送End marker指示，该End marker指示用于指示源UPF1通过源路径(即向源UPF2)发送End Marker。
步骤906b，源UPF1向SMF发送拒绝消息。相应的，SMF接收该拒绝消息。
该拒绝消息可以携带原因值，该原因值为UE1正在切换。
由于源UPF1拒绝更新Nx隧道信息，因此源UPF1继续将UE1的上行数据发送给UE2的源UPF2。其中，若步骤906a中还发送了End Marker指示，则源UPF1不发送End Marker，也即源UPF1忽略该End Marker指示。
需要说明的是，由于源基站2与目标基站2之间在切换准备阶段建立了转发隧道，源UPF1拒绝了Nx隧道的切换，意味着UE1发送的上行数据仍然发送给源UPF2，并由源UPF2发送给源基站2，源基站2再通过该转发隧道发送给目标基站2，然后目标基站2将UE1的数据发送给UE2。此时，UE1发送的上行数据在UE2的源卫星(即卫星3)和目标卫星(即卫星4)之间存在绕行。虽然存在绕行，但可避免并发切换时导致的数据包乱序。
步骤907至步骤911，同上述步骤807至步骤811。
需要说明的是，上述图8的实施例仅涉及到UE2的一个UPF，即UPF2，而该图9的实施例中，涉及到UE2的两个UPF，即源UPF2和目标UPF2。上述步骤901至步骤906，以及步骤907至步骤911是引用了图8的实施例中的相应步骤。其中，上述步骤901至步骤906，以及步骤907至步骤911中涉及到的UPF2均是指源UPF2。
步骤912，SMF向目标UPF2发送会话修改请求消息。相应的，目标UPF2接收该会话修改请求消息。
该会话修改请求消息包括UE1的PDU会话对应的目标UPF1的Nx隧道信息，以及End Marker指示。
SMF从N4容器中获取到UE1的PDU会话对应的目标UPF1的Nx隧道信息，并将该UE1的PDU会话对应的目标UPF1的Nx隧道信息发送给目标UPF2，从而目标UPF2将该PDU会话对应的Nx隧道信息，由源UPF1的Nx隧道信息更新为目标UPF1的Nx隧道信息，从而后续目标UPF2将收到的UE2需要发送给UE1的数据直接发送给目标UPF1，即不再经过源UPF1和源基站1绕行。
该End Marker指示用于指示目标UPF2通过源路径(即向源UPF1)发送End Marker。目标UPF2通过源路径发送End Marker。目标UPF2将收到的UE2需要发送给UE1的数据发送给目标UPF1，由目标UPF1发送给UE1。此时，UE1的下行路径切换为：UE2->目标基站2->目标UPF2->目标UPF1->目标基站1->UE1。此时，UE1的上下行路径均切换完成。其中，目标UPF2是在切换准备阶段从源UPF2获取到源UPF1的信息。
可选的，该会话修改请求消息可以是N4会话修改请求消息，即PFCP Session Modification Request消息。
需要说明的是，若目标UPF1对应的SMF与目标UPF2对应的SMF不同，则目标UPF1对应的SMF将UE1的PDU会话对应的目标UPF1的Nx隧道信息和End Marker指示发送给目标UPF2对应的SMF，然后由目标UPF2对应的SMF将UE1的PDU会话对应的目标UPF1的Nx隧道信息和End marker指示发送给目标UPF2。
步骤913，SMF向AMF发送会话修改响应消息。相应的，AMF接收该会话修改响应消息。
该会话修改响应消息包括N4容器，该N4容器包括PFCP会话修改响应消息和目标UPF2的Nx隧道信息。该N4容器是需要发送给目标UPF1的。
可选的，该N4容器中还包括End Marker指示。
步骤914，AMF向目标基站1发送路径切换响应消息(PATH SWITCH REQUEST ACK)。相应的，目标基站1接收该路径切换响应消息。
该路径切换响应消息中包括成功切换的PDU会话的标识和该PDU会话对应的N4容器，该N4容器来自上述步骤913的会话修改响应消息。
步骤915，目标基站1向目标UPF1发送N4容器。相应的，目标UPF1接收该N4容器。
该N4容器包括PFCP会话修改响应消息和目标UPF2的Nx隧道信息，目标UPF1保存目标UPF2的Nx隧道信息。
可选的，若N4容器中包括End Marker指示，则目标UPF1根据End Marker指示，向源UPF2发送End Marker，并且开始向目标UPF2发送数据。其中，目标UPF1是在切换准备阶段获取到源UPF2的信息。
需要说明的是，该实施例是以UE1和UE2由相同的AMF和SMF服务为例进行说明，该实施例也适用于UE1和UE2由不同的SMF和/或不同的AMF提供服务。
该实施例中，源UPF1在发现正在切换的UE的通信对端UPF也发生切换时，源UPF1不更新Nx隧道，仍然通过源路径发送数据，以避免与目标UPF1的路径不一致而导致丢包或乱序。在该实施例中，在SMF通知目标UPF1发送End Marker之前，UE1已经将路径切换到向目标UPF1发送上行数据，因此，在SMF向目标UPF1发送End marker指示之 前已经没有上行数据经过源UPF1发送给源UPF2了，也即目标UPF1发送的End Marker是发送给源UPF2的最后一个数据包，目标UPF1后续将数据发送给目标UPF2。End Marker进一步由源UPF2发送给源基站2，并由源基站2发送给目标基站2。目标基站2在通过源基站2到目标基站2间的转发隧道收到End Marker后再将从目标UPF2收到的UE2的下行数据发送给UE2，并且从转发隧道收到的数据包的发送时间比从目标UPF2收到的数据包的发送时间早，应先发送给UE2，从而保证了数据的按序传输。
参考图10，为本申请实施例提供的一种切换方法的流程示意图。该实施例可以应用于卫星的移动导致的UE1和UE2同时跨卫星切换的场景。该流程中，UE1的卫星发生切换，切换前，由卫星1上的源基站1和源UPF1为UE1提供服务，切换后，由卫星2上的目标基站1和目标UPF1为UE1提供服务。UE2的卫星也发生切换，切换前，由卫星3上的源基站2和源UPF2为UE2提供服务，切换后，由卫星4上的目标基站2和目标UPF2为UE2提供服务。该图10的实施例是对上述图6的实施例的改进。该图10对应的实施例也是上述图7(c)的实施例的一种具体实现。
该实施例可用于UE1和UE2同时跨卫星移动时导致的Nx隧道切换的时序问题。
该流程包括以下步骤：
步骤1001至步骤1009，同上述步骤801至步骤809。
需要说明的是，上述图8的实施例仅涉及到UE2的一个UPF，即UPF2，而该图10的实施例中，涉及到UE2的两个UPF，即源UPF2和目标UPF2。上述步骤1001至步骤1009是引用了图8的实施例中的相应步骤。其中，上述步骤1001至步骤1009中涉及到的UPF2均是指源UPF2。
同时，UE2也发生了跨卫星的切换，且UE2完成了与上述步骤1001至步骤1009类似的操作。
步骤1010，目标基站1向AMF发送路径切换请求消息(PATH SWITCH REQUEST)。相应的，AMF接收该路径切换请求消息。
该路径切换请求消息中包括UE1的PDU会话的标识以及每个PDU会话对应的N4容器，或者理解为该路径切换请求消息中包括一个或多个(PDU会话的标识、N4容器)。
每个PDU会话对应的N4容器内封装有N4消息，该N4消息可以是PFCP会话修改请求消息，该PFCP会话修改请求消息是由目标UPF1为该PDU会话生成的，用于通知SMF：该PDU会话对应的UPF发生了切换。该PFCP会话修改请求消息中包括该PDU会话对应的N4会话信息(例如，SMF的F-SEID和/或SMF的Node ID)、目标UPF1的N4接口信息(例如，目标UPF1的F-SEID和/或目标UPF1的Node ID等，其中，目标UPF1的F-SEID用于在目标UPF1中唯一标识该会话)以及包括目标UPF1为该PDU会话分配的目标UPF1的Nx隧道信息，该目标UPF1的Nx隧道信息将会发送给目标UPF2，用于目标UPF2向目标UPF1发送UE2需要发送给UE1的数据。可选的，该PFCP会话修改请求消息中还可以包括该PDU会话对应的目标UPF1的N3隧道信息。可选的，该PFCP会话修改请求消息中还可以包括该PDU会话对应的目标基站1的N3隧道信息。
步骤1011，目标基站2向AMF发送路径切换请求消息(PATH SWITCH REQUEST)。相应的，AMF接收该路径切换请求消息。
该路径切换请求消息中包括UE2的PDU会话的标识以及每个PDU会话对应的N4容器，或者理解为该路径切换请求消息中包括一个或多个(PDU会话的标识、N4容器)。
每个PDU会话对应的N4容器内封装有N4消息，该N4消息可以是PFCP会话修改请求消息，该PFCP会话修改请求消息是由目标UPF2为该PDU会话生成的，用于通知SMF：该PDU会话对应的UPF发生了切换。该PFCP会话修改请求消息中包括该PDU会话对应的N4会话信息(例如，SMF的F-SEID和/或SMF的Node ID)、目标UPF2的N4接口信息(例如，目标UPF2的F-SEID、目标UPF2的Node ID等)以及包括目标UPF2为该PDU会话分配的目标UPF2的Nx隧道信息，该目标UPF2的Nx隧道信息将会发送给目标UPF1，用于目标UPF1向目标UPF2发送UE1需要发送给UE2的数据。可选的，该PFCP会话修改请求消息中还可以包括该PDU会话对应的目标UPF2的N3隧道信息。可选的，该PFCP会话修改请求消息中还可以包括该PDU会话对应的目标基站2的N3隧道信息。
步骤1012，AMF向SMF发送会话修改请求消息。相应的，SMF接收该会话修改请求消息。
这里的SMF指的是UE1的PDU会话对应的SMF。其中，UE1的不同PDU会话可以对应相同的SMF，也可以对应不同的SMF，本申请不限定。
该会话修改请求消息包括UE1的该PDU会话对应的N4容器。该N4容器即为上述步骤1010中AMF收到的N4容器。
SMF根据N4容器中的N4消息执行相应的操作，例如，SMF将该PDU会话对应的UPF的源UPF1的NodeID替换为N4消息中的目标UPF1的NodeID，和/或SMF将该PDU会话对应的UPF的F-SEID替换为N4消息中目标UPF1的F-SEID。
并且，SMF保存目标UPF1的Nx隧道信息、目标UPF1的N3隧道信息等。
可选的，该会话修改请求消息可以是Nsmf_PDUSession_SMContextUpdate Request消息。
步骤1013，SMF向AMF发送会话修改响应消息。相应的，AMF接收该会话修改响应消息。
该会话修改响应消息包括N4容器，该N4容器包括PFCP会话修改响应消息。该N4容器是需要发送给目标UPF1的。
该会话修改响应消息是针对上述步骤1012的会话修改请求消息的响应消息。由于此时SMF仍未收到UE2的目标UPF2的Nx隧道信息，因此，该会话修改响应消息中不携带目标UPF2的Nx隧道信息。
可选的，该会话修改响应消息可以是Nsmf_PDUSession_SMContextUpdate Response消息。
步骤1014，AMF向SMF发送会话修改请求消息。相应的，SMF接收该会话修改请求消息。
这里的SMF指的是UE2的PDU会话对应的SMF。其中，UE2的不同PDU会话可以对应相同的SMF，也可以对应不同的SMF，本申请不限定。
该会话修改请求消息包括UE2的PDU会话对应的N4容器。该N4容器即为上述步骤1011中AMF收到的N4容器。
SMF根据N4容器中的N4消息执行相应的操作，例如，SMF将该PDU会话对应的UPF的NodeID替换为N4消息中的目标UPF2的NodeID，和/或SMF将该PDU会话对应的UPF的F-SEID替换为N4消息中目标UPF2的F-SEID。
并且，SMF保存目标UPF2的Nx隧道信息、目标UPF2的N3隧道信息等。
可选的，该会话修改请求消息可以是Nsmf_PDUSession_SMContextUpdate Request消息。
步骤1015，AMF向目标基站1发送路径切换响应消息(PATH SWITCH REQUEST ACK)。相应的，目标基站1接收该路径切换响应消息。
该路径切换响应消息中包括成功切换的UE1的PDU会话的标识和该PDU会话对应的N4容器，该N4容器来自上述步骤1013的会话修改响应消息。
步骤1016，SMF向AMF发送会话修改响应消息。相应的，AMF接收该会话修改响应消息。
该会话修改响应消息包括N4容器，该N4容器包括目标UPF1的Nx隧道信息和End Marker指示。该N4容器是需要发送给目标UPF2的。该End Marker指示用于指示目标UPF2在向目标UPF1发送数据前先通过源路径(即向源UPF1)发送End Marker。
该会话修改响应消息是针对上述步骤1014的会话修改请求消息的响应消息。由于此时SMF已经收到UE1的目标UPF1的Nx隧道信息，因此，该会话修改响应消息中携带目标UPF1的Nx隧道信息。
可选的，该会话修改响应消息可以是Nsmf_PDUSession_SMContextUpdate Response消息。
步骤1017，AMF向目标基站2发送路径切换响应消息(PATH SWITCH REQUEST ACK)。相应的，目标基站2接收该路径切换响应消息。
该路径切换响应消息中包括成功切换的UE2的PDU会话的标识和该PDU会话对应的N4容器，该N4容器来自上述步骤1016的会话修改响应消息。
步骤1018，目标基站2向目标UPF2发送N4容器。相应的，目标UPF2接收该N4容器。
目标UPF2根据N4容器中的End Marker指示，通过源路径(即向源UPF1)发送End Marker。目标UPF2将收到的UE2需要发送给UE1的数据发送给目标UPF1，由目标UPF1发送给UE1。此时，UE2的下行路径切换为：UE2->目标基站2->目标UPF2->目标UPF1->目标基站1->UE1。此时，UE1的下行路径切换完成。
步骤1019，SMF向目标UPF1发送目标UPF2的Nx隧道信息和End Marker指示。相应的，目标UPF1接收该目标UPF2的Nx隧道信息和End Marker指示。
该End Marker指示用于指示目标UPF1在向目标UPF2发送数据前先通过源路径(即向源UPF2)发送End Marker。
目标UPF1根据End Marker指示，通过源路径(即向源UPF2)发送End Marker，后续，目标UPF1将收到的UE1需要发送给UE2的数据发送给目标UPF2，由目标UPF2发送给UE2。此时，UE1的上行路径切换为：UE1->目标基站1->目标UPF1->目标UPF2->目标基站2->UE2。此时，UE1的上行路径切换完成。
需要说明的是，该实施例是以UE1和UE2由相同的AMF和SMF服务为例进行说明，该实施例也适用于UE1和UE2由不同的SMF和/或不同的AMF提供服务。在该实施例中，在步骤1019，SMF通知目标UPF1切换路径并发送End marker，目标UPF1在发送End marker之后不再向源UPF2发送任何数据包。目标基站2在通过源基站2到目标基站2间的转发隧道收到End Marker后再将从目标UPF2收到的UE2的下行数据发送给UE2，并 且从转发隧道收到的数据包的发送时间比从目标UPF2收到的数据包的发送时间早，应先发送给UE2，从而保证了数据的按序传输。
参考图11，为本申请实施例提供的一种切换方法的流程示意图。该实施例可以应用于卫星的移动导致的UE1和UE2同时跨卫星切换的场景。该流程中，UE1的卫星发生切换，切换前，由卫星1上的源基站1和源UPF1为UE1提供服务，切换后，由卫星2上的目标基站1和目标UPF1为UE1提供服务。UE2的卫星也发生切换，切换前，由卫星3上的源基站2和源UPF2为UE2提供服务，切换后，由卫星4上的目标基站2和目标UPF2为UE2提供服务。该图11的实施例是对上述图6的实施例的改进。该图11对应的实施例也是上述图7(d)的实施例的一种具体实现。
该实施例可用于UE1和UE2同时跨卫星移动时导致的数据绕行的问题。
该流程包括以下步骤：
步骤1101至步骤1103，同上述步骤801至步骤803。
步骤1103a，SMF向源UPF1发送目标UPF2的Nx隧道信息。相应的，源UPF1接收该目标UPF2的Nx隧道信息。
在步骤1103a之前，UE2也发生切换，且SMF已经收到的了切换后的目标UPF2的Nx隧道信息。
由于SMF还不知道UE1正在发生切换，SMF会认为UE1仍然由源UPF1服务，因此当SMF收到UE2的切换后的目标UPF2的Nx隧道信息后，将目标UPF2的Nx隧道信息发送给源UPF1。
在上述图9的实施例中，源UPF1的切换还未完成时，源UPF1拒绝目标UPF2的Nx隧道信息，具体参考上述步骤906a和步骤906b。而在该图11的实施例中，源UPF1的切换还未完成时，源UPF1不拒绝目标UPF2的Nx隧道信息，后续源UPF1使用该目标UPF2的Nx隧道信息将UE1的上行数据包发送给目标UPF2，而不再发送给源UPF2。
并且，在一种可能的实施方式中，SMF记录向源UPF1发送该目标UPF1的Nx隧道信息的时间戳。SMF在收到针对该步骤1103a的响应消息后，通知UE2的源UPF2向UE2的目标基站2发送End Marker，即，UE2的目标基站2收到的End Marker是由源UPF2发送的，而在前面的实施例中，End Marker是由对端UE(即UE1)的源UPF1或目标UPF1发送的。SMF在确认UE1侧不再通过源路径发送数据时通知源UPF2发送End Marker，只要源UPF1发送给源UPF2的数据包比SMF通知源UPF2发送End Marker早，则不会发生乱序。由于SMF先通知源UPF1切换路径的，因此，可以认为一般情况下源UPF1发送给源UPF2的数据包比SMF通知源UPF2发送End Marker早。
步骤1103a可发生在步骤1106a前的任何时候，本实施例以该步骤1103a发生在步骤1103之后且在步骤1104前为例进行说明。
步骤1104至步骤1106，同上述步骤804至步骤806。
步骤1106a，目标基站1向UE1的AMF发送切换准备请求消息。相应的，AMF接收该切换准备请求消息。
该切换准备请求消息包括目标基站1的标识和UE1的每个PDU会话对应的N4容器。N4容器内封装有N4消息，该N4消息可以是PFCP会话修改请求消息，该PFCP会话修改请求消息是由目标UPF1为该PDU会话生成的，用于通知SMF：该PDU会话对应的UPF发生了切换。该PFCP会话修改请求消息中包括该PDU会话对应的N4会话信息(例 如，SMF的F-SEID和/或SMF的Node ID)、目标UPF1的N4接口信息(例如，目标UPF1的F-SEID和/或目标UPF1的Node ID等，其中，目标UPF1的F-SEID用于在目标UPF1中唯一标识该会话)以及包括目标UPF1为该PDU会话分配的目标UPF1的Nx隧道信息，该目标UPF1的Nx隧道信息将会发送给目标UPF2，用于目标UPF2根据该目标UPF1的Nx隧道信息，向目标UPF1发送UE2的数据。可选的，该PFCP会话修改请求消息中还可以包括该PDU会话对应的目标UPF1的N3隧道信息。可选的，该PFCP会话修改请求消息中还可以包括该PDU会话对应的目标基站1的N3隧道信息。
在一种可能的实施方式中，N4容器中还包括源UPF2的Nx隧道信息。
步骤1106b，AMF向SMF发送会话修改请求消息。相应地，SMF接收该会话修改请求消息。
该会话修改请求消息包括PDU会话对应的N4容器和一个指示信息，该指示信息用于该流程为切换准备流程。
步骤1106c，SMF向AMF发送会话修改响应消息。相应地，AMF接收该会话修改响应消息。
该会话修改响应消息中包括N4容器，该N4容器包括PFCP会话修改响应消息。该N4容器是需要发送给目标UPF1的。
SMF检查上次向源UPF1发送目标UPF2的Nx隧道信息的时间戳，如果该时间戳与当前时刻的差值小于预定的阈值，表明源UPF1在步骤1102后收到了更新的Nx隧道消息，即目标UPF2的隧道信息，因此目标UPF1收到的源UPF2的Nx隧道信息已经过时，从而SMF在该N4容器中携带目标UPF2的Nx隧道信息，以便目标UPF1保存该目标UPF2的Nx隧道信息。
或者，SMF也可以不基于时间戳判断是否向目标UPF1发送目标UPF2的Nx隧道信息，而是总是在该N4容器中携带本地保存的UE2对应的最新的Nx隧道信息，这样，无论目标UPF1从源UPF1收到的是否是UE2对应的最新的Nx隧道信息，目标UPF1总能收到UE2对应的最新的Nx隧道信息。
或者，如果目标UPF1发送给SMF的N4容器中包括UE2的UPF2的Nx隧道信息，则SMF判断本地保存的UPF2的Nx隧道信息与该N4容器中的UPF2的Nx隧道信息是否相同，若不同，则在该会话修改响应消息的N4容器中携带UE2对应的最新的Nx隧道信息。
步骤1106d，AMF向目标基站1发送切换准备响应消息。相应的，目标基站1接收该切换准备响应消息。
AMF从会话修改响应消息中获取N4容器，然后向目标基站1发送切换准备响应消息，该切换准备响应消息中包括该N4容器。
步骤1106e，目标基站1向目标UPF1发送N4容器。相应的，目标UPF1接收该N4容器。
若N4容器中包括了UE2对应的最新的Nx隧道信息，即目标UPF2的Nx隧道信息，目标UPF1保存该Nx隧道信息，并在后续发送UE1的上行数据包时使用该Nx隧道信息进行发送。
步骤1107至步骤1111，同上述步骤807至步骤811。
需要说明的是，在步骤1110的路径切换请求消息中可以不携带N4容器。这是因为在 上述步骤1106a中的切换准备请求消息已经携带了N4容器，若目标UPF1没有需要更新的内容，目标UPF1不需要携带N4容器。
步骤1112，SMF向目标UPF2发送会话修改请求消息。相应的，目标UPF2接收该会话修改请求消息。
该会话修改请求消息包括UE1的PDU会话对应的目标UPF1的Nx隧道信息。
SMF从N4容器中获取到UE1的PDU会话对应的目标UPF1的Nx隧道信息，并将该UE1的PDU会话对应的目标UPF1的Nx隧道信息发送给目标UPF2，从而目标UPF2将该PDU会话对应的Nx隧道信息，由该PDU会话对应的源UPF1的Nx隧道信息更新为该PDU会话对应的目标UPF1的Nx隧道信息，从而后续目标UPF2将收到的UE2需要发送给UE1的数据直接发送给目标UPF1，即不再经过源UPF1和源基站1绕行。
可选的，该会话修改请求消息可以是N4会话修改请求消息，即PFCP Session Modification Request消息。
需要说明的是，若目标UPF1对应的SMF与目标UPF2对应的SMF不同，则目标UPF1对应的SMF将UE1的PDU会话对应的目标UPF1的Nx隧道信息发送给目标UPF2对应的SMF，然后由目标UPF2对应的SMF将UE1的PDU会话对应的目标UPF1的Nx隧道信息发送给目标UPF2。
步骤1113，同上述步骤813。
步骤1114，SMF在确认将目标UPF1的Nx隧道信息发送给了目标UPF2，SMF向源UPF1发送End Marker指示。相应的，源UPF1接收该End Marker指示。
该End Marker指示用于指示源UPF1向源基站1发送End Marker，该End Marker由源基站1转发给目标基站1。此时目标基站1获知不会再有数据从源UPF1发送给目标基站1，因此，目标基站1可以开始处理来自目标UPF1的数据。
根据上述方案，在UE2发生切换时，SMF及时将UE2对应的最新的Nx隧道信息发送给源UPF1，因此源UPF1可以根据最新的Nx隧道信息向目标UPF2发送UE1的数据，避免了将数据发送给源UPF2后再通过源基站2与目标基站2之间的转发路径进行转发，减少了数据的迂回。并且，该方案中SMF在确认UE的通信对端已经从源路径切换到目标路径后通知UE的源UPF发送End Marker，避免了数据包乱序。
参考图12，为本申请实施例提供的一种切换方法的流程示意图。该实施例可以应用于卫星的移动导致的UE1和UE2同时跨卫星切换的场景。该流程中，UE1的卫星发生切换，切换前，由卫星1上的源基站1和源UPF1为UE1提供服务，切换后，由卫星2上的目标基站1和目标UPF1为UE1提供服务。UE2的卫星也发生切换，切换前，由卫星3上的源基站2和源UPF2为UE2提供服务，切换后，由卫星4上的目标基站2和目标UPF2为UE2提供服务。该图12的实施例是对上述图6的实施例的改进。该图12对应的实施例也是上述图7(e)的实施例的一种具体实现。
该实施例可用于UE1和UE2同时跨卫星移动时导致的数据绕行问题。
该流程包括以下步骤：
步骤1201至步骤1206，同上述步骤801至步骤806。
步骤1206a，同上述步骤1106a。
步骤1206b，同上述步骤1106b。
步骤1206c，同上述步骤1106c。
步骤1206d，AMF向目标基站1发送切换准备响应消息。相应的，目标基站1接收该切换准备响应消息。
该切换准备响应消息中包括N4容器。该N4容器包括PFCP会话修改响应消息。该N4容器是需要发送给目标UPF1的。
步骤1206e，目标基站1向目标UPF1发送N4容器。相应的，目标UPF1接收该N4容器。
此时，由于SMF还未收到UE2的目标UPF2的Nx隧道信息，因此，步骤1206c、步骤1206d和步骤1206e的N4容器中均不包括目标UPF2的Nx隧道信息。
在步骤1212之前、步骤1206e之后的任意时刻，若SMF收到UE2对应的最新的Nx隧道信息，即目标UPF2的Nx隧道信息，SMF都立刻将UE2对应的最新的Nx隧道信息发送给目标UPF1和源UPF1。如图12的步骤A所示。其中，SMF可使用在步骤1206b收到的N4容器中的目标UPF1的F-SEID，直接给目标UPF1发送PFCP会话修改请求消息(即可不经过目标基站1)，以便通知目标UPF1使用目标UPF2的Nx隧道信息，即向目标UPF2发送UE1的上行数据。
由于此时UE1可能还继续通过源基站1发送上行数据，因此，SMF也需要将目标UPF2的Nx隧道信息发送给源UPF1。这样，源UPF1也可以直接使用目标UPF2的Nx隧道信息，即向目标UPF2发送UE1的上行数据。
步骤1207至步骤1209，同上述步骤807至步骤809。
步骤1210，SMF在确认源UPF1、目标UPF1均更新了目标UPF2的Nx隧道信息后，SMF向源UPF2发送End Marker指示。相应的，源UPF2接收该End Marker指示。
该End Marker指示用于指示源UPF2向源基站2发送End Marker，源UPF2向源基站2发送End Marker，该End Marker由源基站2转发给目标基站2。此时目标基站2获知不会再有数据从源UPF2发送给目标基站2，因此，目标基站2可以开始处理由UPF1(源UPF1或目标UPF1)发送的数据。
步骤1211至步骤1215，同上述步骤1110至步骤1114。
根据上述方案，在UE2发生切换时，SMF及时将UE2对应的最新的Nx隧道信息发送给源UPF1，因此源UPF1可以根据最新的Nx隧道信息向目标UPF2发送UE1的数据，避免了将数据发送给源UPF2后再通过源基站2与目标基站2之间的转发路径进行转发，减少了数据的迂回。
参考图13，为本申请实施例提供的一种切换方法的流程示意图。该实施例可以应用于卫星的移动导致的UE1和UE2同时跨卫星切换的场景。该流程中，UE1的卫星发生切换，切换前，由卫星1上的源基站1和源UPF1为UE1提供服务，切换后，由卫星2上的目标基站1和目标UPF1为UE1提供服务。UE2的卫星也发生切换，切换前，由卫星3上的源基站2和源UPF2为UE2提供服务，切换后，由卫星4上的目标基站2和目标UPF2为UE2提供服务。该图13的实施例是对上述图6的实施例的改进。
该实施例可用于UE1和UE2同时跨卫星移动时导致的数据绕行问题。
该流程包括以下步骤：
步骤1301至步骤1306，同上述步骤801至步骤806。
步骤1306a，同上述步骤1206a。
步骤1306b，同上述步骤1206b。
步骤1306c，同上述步骤1206c。
步骤1306d，同上述步骤1206d。
步骤1306e，同上述步骤1206e。
此时，由于SMF还未收到UE2的目标UPF2的Nx隧道信息，因此，步骤1306c、步骤1306d和步骤1306e的N4容器中均不包括目标UPF2的Nx隧道信息。
步骤1307至步骤1309，同上述步骤807至步骤809。
步骤1310，目标基站1向AMF发送路径切换请求消息(PATH SWITCH REQUEST)。相应的，AMF接收该路径切换请求消息。
该路径切换请求消息中包括UE1的PDU会话的标识。
步骤1311，UE2也发生了切换，UE2的目标基站2向AMF发送路径切换请求消息(PATH SWITCH REQUEST)。相应的，AMF接收该路径切换请求消息。
该路径切换请求消息中包括UE2的PDU会话的标识。
步骤1312，AMF向SMF发送会话修改请求消息。相应的，SMF接收该会话修改请求消息。
这里的SMF指的是UE1的PDU会话对应的SMF。其中，UE1的不同PDU会话可以对应相同的SMF，也可以对应不同的SMF，本申请不限定。
可选的，该会话修改请求消息可以是Nsmf_PDUSession_SMContextUpdate Request消息。
该消息指示SMF进行路径切换。
步骤1313，SMF向目标UPF2和源UPF2发送目标UPF1的Nx隧道信息。
步骤1314，SMF向源UPF1发送End Marker指示。相应的，源UPF1接收该End Marker指示。
该End Marker指示用于指示源UPF1向源基站1发送End Marker，该End Marker由源基站1转发给目标基站1。此时目标基站1获知不会再有数据从源UPF1发送给目标基站1，因此，目标基站1可以开始处理来自目标UPF1的数据。
此处，是假设在该步骤1314步前，源UPF2或目标UPF2发送给源UPF1的所有数据包均已到达源UPF1。
步骤1315，SMF向AMF发送会话修改响应消息。相应的，AMF接收该会话修改响应消息。
该会话修改响应消息包括N4容器，该N4容器包括PFCP会话修改响应消息。该N4容器是需要发送给目标UPF1的。
步骤1316，AMF向SMF发送会话修改请求消息。相应的，SMF接收该会话修改请求消息。
这里的SMF指的是UE2的PDU会话对应的SMF。其中，UE2的不同PDU会话可以对应相同的SMF，也可以对应不同的SMF，本申请不限定。
可选的，该会话修改请求消息可以是Nsmf_PDUSession_SMContextUpdate Request消息。
该消息指示SMF进行路径切换。
步骤1317，AMF向目标基站1发送路径切换响应消息(PATH SWITCH REQUESTACK)。相应的，目标基站1接收该路径切换响应消息。
步骤1318，SMF向目标UPF1发送目标UPF2的Nx隧道信息。相应的，目标UPF1接收该目标UPF2的Nx隧道信息。
步骤1319，SMF向源UPF2发送End Marker指示。相应的，源UPF2接收该End Marker指示。
该End Marker指示用于指示源UPF2向源基站2发送End Marker，源UPF2向源基站2发送End Marker，该End Marker由源基站2转发给目标基站2。此时目标基站2获知不会再有数据从源UPF2发送给目标基站2，因此，目标基站2可以开始处理由UPF1(源UPF1或目标UPF1)发送的数据。
其中，这里假设在步骤1318之后，目标UPF1发送给源UPF2的数据均已到达源UPF2。
步骤1320，SMF向AMF发送会话修改响应消息。相应的，AMF接收该会话修改响应消息。
该会话修改响应消息是针对步骤1316的响应。
步骤1321，AMF向目标基站2发送路径切换响应消息(PATH SWITCH REQUEST ACK)。相应的，目标基站2接收该路径切换响应消息。
根据上述方案，在UE2发生切换时，SMF及时将UE2对应的最新的Nx隧道信息发送给源UPF1，因此源UPF1可以根据最新的Nx隧道信息向目标UPF2发送UE1的数据，避免了将数据发送给源UPF2后再通过源基站2与目标基站2之间的转发路径进行转发，减少了数据的迂回。
参考图14，为本申请实施例提供的一种切换方法的流程示意图。该实施例可以应用于卫星的移动导致的UE1和UE2同时跨卫星切换的场景。该流程中，UE1的卫星发生切换，切换前，由卫星1上的源基站1和源UPF1为UE1提供服务，切换后，由卫星2上的目标基站1和目标UPF1为UE1提供服务。UE2的卫星也发生切换，切换前，由卫星3上的源基站2和源UPF2为UE2提供服务，切换后，由卫星4上的目标基站2和目标UPF2为UE2提供服务。该图14的实施例是对上述图6的实施例的改进。该图14对应的实施例也是上述图7(f)的实施例的一种具体实现。
该实施例未对切换流程进行优化，在UE的切换过程中，UE的上下行数据都经过源UPF发送。在路径切换的过程中，由SMF重选与目标基站部署在相同卫星的UPF作为目标UPF，并将UE当前对应的UPF切换到该UPF。
该流程包括以下步骤：
步骤1401，源基站1确定UE1要进行切换，源基站1向目标基站1发送切换请求消息。相应的，目标基站1接收该切换请求消息。
该切换请求消息包括源UPF1的N3隧道信息。
步骤1402，目标基站1向源基站1发送切换响应消息。相应的，源基站1接收该切换响应消息。
在上述过程步骤1401和步骤1402的过程中，可以建立源基站1与目标基站1间的转发隧道，因此发送给UE1的下行数据可以由源基站1经过该转发隧道发送给目标基站1，目标基站1暂时缓存下行数据。
步骤1403，源基站1向UE1发送切换命令。相应的，UE1接收该切换命令。
该切换命令可以是一个RRC重配置消息。
步骤1404，UE1与目标基站1进行同步。
UE1在收到该切换命令后，发起与目标基站1同步过程，以便通过目标基站1接入。
步骤1405，UE1向目标基站1发送切换完成指示。相应的，目标基站1接收该切换完成指示。
该切换完成指示可以是RRC重配置完成消息。
此时，目标基站1可以将下行数据发送给UE1。
UE1可以通过目标基站1发送上行数据。目标基站1可以使用步骤1401中收到的源UPF1的N3隧道信息，将上行数据发送给源UPF1，然后源UPF1将上行数据发送给源UPF2。
步骤1406，目标基站2向AMF发送路径切换请求消息(PATH SWITCH REQUEST)。相应的，AMF接收该路径切换请求消息。
其中，UE2也发生了跨卫星切换，UE2的跨卫星切换流程可参见上述步骤1401至步骤1404。接着UE2的目标基站2执行该步骤1406。
该路径切换请求包括用于选择UPF的信息，比如可以是目标基站2的标识信息或卫星4的标识信息，或者该路径切换请求包括目标UPF2的标识信息。
以及，该路径切换请求还包括目标基站2的N3隧道信息。
步骤1407，AMF向SMF发送会话修改请求消息。相应的，SMF接收该会话修改请求消息。
该会话修改请求消息包括用于选择UPF的信息或目标UPF2的标识信息。
以及，该路径切换请求还包括目标基站2的N3隧道信息。
可选的，该会话修改请求消息可以是Nsmf_PDUSession_SMContextUpdate Request消息。
步骤1407a，SMF选择目标UPF2。
比如，若会话修改请求消息包括用于选择UPF的信息，且用于选择UPF的信息是目标基站2的标识信息，则SMF可以向NRF发送查询请求，其中携带目标基站2的标识信息，NRF向SMF返回与目标基站2部署在同一卫星上的目标UPF2的标识信息。
再比如，若会话修改请求消息包括用于选择UPF的信息，且用于选择UPF的信息是卫星4的标识信息，则SMF可以向NRF发送查询请求，其中携带卫星4的标识信息，NRF向SMF返回部署在卫星4上的目标UPF2的标识信息。
再比如，若会话修改请求消息包括目标UPF2的标识信息，则SMF可直接选择该目标UPF2。
步骤1408，目标基站1向AMF发送路径切换请求消息(PATH SWITCH REQUEST)。相应的，AMF接收该路径切换请求消息。
该路径切换请求包括用于选择UPF的信息，比如可以是目标基站1的标识信息或卫星2的标识信息，或者该路径切换请求包括目标UPF1的标识信息。
以及，该路径切换请求还包括目标基站1的N3隧道信息。
步骤1409a，SMF向目标UPF2发送PFCP会话建立请求消息。相应的，目标UPF2接收该PFCP会话建立请求消息。
该PFCP会话建立请求消息包括源UPF1的Nx隧道信息和目标基站2的N3隧道信息。
由于SMF还未收到目标UPF1的Nx隧道信息，此时，SMF仍然将源UPF1的Nx隧道信息发送给目标UPF2。
步骤1409b，目标UPF2向SMF发送PFCP会话建立响应消息。相应的，SMF接收该 PFCP会话建立响应消息。
该PFCP会话建立响应消息包括目标UPF2的N3隧道信息和目标UPF2的Nx隧道信息。
步骤1410，AMF向SMF发送会话修改请求消息。相应的，SMF接收该会话修改请求消息。
该会话修改请求消息包括用于选择UPF的信息或目标UPF1的标识信息。
以及，该路径切换请求还包括目标基站1的N3隧道信息。
可选，该步骤1410和步骤1409b可以是并发的，即几乎同时到达SMF。
可选的，该会话修改请求消息可以是Nsmf_PDUSession_SMContextUpdate Request消息。
步骤1410a，SMF选择目标UPF1。
比如，若会话修改请求消息包括用于选择UPF的信息，且用于选择UPF的信息是目标基站1的标识信息，则SMF可以向NRF发送查询请求，其中携带目标基站1的标识信息，NRF向SMF返回与目标基站1部署在同一卫星上的目标UPF1的标识信息。
再比如，若会话修改请求消息包括用于选择UPF的信息，且用于选择UPF的信息是卫星2的标识信息，则SMF可以向NRF发送查询请求，其中携带卫星2的标识信息，NRF向SMF返回部署在卫星2上的目标UPF1的标识信息。
再比如，若会话修改请求消息包括目标UPF1的标识信息，则SMF可直接选择该目标UPF1。
步骤1411，SMF向源UPF1发送N4更新消息。相应的，源UPF1接收该N4更新消息。
该N4更新消息包括目标UPF2的Nx隧道信息和End Marker指示。
根据优先更新Nx隧道的原则，即使此时SMF已经收到了UE1的切换，SMF也暂停UE1的切换流程的处理，优先将目标UPF2的Nx隧道信息发送给源UPF1。即，若正在执行UE1的路径切换流程，SMF在收到UE2的目标UPF的Nx隧道信息后，SMF在发送会话更新响应消息(步骤1417)之前，向源UPF1发送目标UPF2的Nx隧道信息和End Marker指示。
其中，EndMarker指示用于指示源UPF1通过源路径(经过源UPF2)发送End Marker。源UPF1根据EndMarker指示，通过源路径(经过源UPF2)发送End Marker。源UPF1开始向目标路径(经过目标UPF2)发送收到的UE1需要发送给UE2的数据(也即UE2的下行数据)。此时，UE2的下行数据直接通过目标UPF2和目标基站2发送给UE2，不再经过源UPF2和源基站2转发。
步骤1412a，SMF向目标UPF1发送PFCP会话建立请求消息。相应的，目标UPF1接收该PFCP会话建立请求消息。
该PFCP会话建立请求消息包括目标基站1的N3隧道信息和目标UPF2的Nx隧道信息。
步骤1412b，目标UPF1向SMF发送PFCP会话建立响应消息。相应的，SMF接收该PFCP会话建立响应消息。
该PFCP会话建立响应消息包括目标UPF1的N3隧道信息和目标UPF1的Nx隧道信息。
步骤1413，SMF向源UPF2发送N4更新消息。相应的，源UPF2接收该N4更新消息。
该N4更新消息包括目标UPF1的Nx隧道信息和End Marker指示。
由于UE2的路径切换还未完成，目标基站2仍然将UE2的上行数据发送给源UPF2，因此SMF暂停UE2的路径切换流程，并向源UPF2发送目标UPF1的Nx隧道信息。即，若正在执行UE2的路径切换流程，SMF在收到目标UPF1的Nx隧道信息后，SMF在发送会话更新响应消息(步骤1415)之前，向源UPF2发送目标UPF1的Nx隧道信息和End Marker指示。
其中，EndMarker指示用于指示源UPF2通过源路径(经过源UPF1)发送End Marker。源UPF2根据EndMarker指示，通过源路径(经过源UPF1)发送End Marker。源UPF2开始向目标路径(经过目标UPF1)发送收到的UE2需要发送给UE1的数据(也即UE1的下行数据)。此时，源UPF2开始通过新路径(经过目标UPF2)发送从UE2收到的需要发送给UE1的数据，即UE1的下行数据。
步骤1414，SMF向目标UPF2发送目标UPF1的Nx隧道信息。相应的，目标UPF2接收该目标UPF1的Nx隧道信息。
由于在步骤1409a中向目标UPF2发送的是源UPF1的Nx隧道信息，这里，SMF需要通知目标UPF2更新Nx隧道信息。
步骤1415，SMF向AMF发送会话修改响应消息。相应的，AMF发送会话修改响应消息。
该会话修改响应消息是针对UE2的会话修改响应。
该会话修改响应消息包括目标UPF2的N3隧道信息。
可选的，该会话修改响应消息可以是Nsmf_PDUSession_SMContextUpdate Response消息。
步骤1416，AMF向目标基站2发送路径切换响应消息(PATH SWITCH REQUEST ACK)。相应的，目标基站2接收该路径切换响应消息。
该路径切换响应消息包括目标UPF2的N3隧道信息。
此时，UE2发送给UE1的数据直接由目标基站2发送给目标UPF2，不再经过源UPF2绕行。
步骤1417，SMF向AMF发送会话修改响应消息。相应的，AMF发送会话修改响应消息。
该会话修改响应消息是针对UE1的会话修改响应。
该会话修改响应消息包括目标UPF1的N3隧道信息。
可选的，该会话修改响应消息可以是Nsmf_PDUSession_SMContextUpdate Response消息。
步骤1418，AMF向目标基站1发送路径切换响应消息。相应的，目标基站1接收该路径切换响应消息。
该路径切换响应消息包括目标UPF1的N3隧道信息。
根据上述方案，若SMF在UE的路径切换过程中收到新的Nx隧道信息，SMF先暂停路径切换流程，优先将新的Nx隧道信息发送给源UPF，在Nx路径切换完成后，SMF再继续路径切换流程。从而如果通信两端的UE发生并发切换，则Nx隧道的切换总是早于 UE的UPF的切换，相当于将Nx隧道切换与UPF的切换解耦，避免在Nx路径切换的同时进行UPF的切换而导致某些数据包丢失或乱序的情况发生。
可以理解的是，为了实现上述实施例中功能，会话管理网元、用户面网元或接入网设备包括了执行各个功能相应的硬件结构和/或软件模块。本领域技术人员应该很容易意识到，结合本申请中所公开的实施例描述的各示例的单元及方法步骤，本申请能够以硬件或硬件和计算机软件相结合的形式来实现。某个功能究竟以硬件还是计算机软件驱动硬件的方式来执行，取决于技术方案的特定应用场景和设计约束条件。
图15和图16为本申请的实施例提供的可能的通信装置的结构示意图。这些通信装置可以用于实现上述图7(a)至图7(f)，以及图8至图14的方法实施例中会话管理网元、用户面网元或接入网设备的功能，因此也能实现上述方法实施例所具备的有益效果。在本申请的实施例中，该通信装置可以是会话管理网元、用户面网元或接入网设备，也可以是应用于会话管理网元、用户面网元或接入网设备的模块(如芯片)。
如图15所示，通信装置1500包括处理单元1510和收发单元1520。通信装置1500用于实现上述方法实施例中会话管理网元、用户面网元或接入网设备的功能。
在第一个实施例中，该通信装置用于执行会话管理网元的功能，收发单元1520，用于通过该目标接入网设备接收来自该第一终端设备的目标用户面网元的指示该第一终端设备的用户面网元发生切换的信息，该信息包括该第一终端设备的目标用户面网元的隧道信息；以及，向第二终端设备的用户面网元发送该第一终端设备的目标用户面网元的隧道信息，以更新该第二终端设备的用户面网元中的该第一终端设备的用户面网元信息，该第一终端设备的目标用户面网元的隧道信息用于向该第一终端设备的目标用户面网元发送该第一终端设备的下行数据。
在一种可能的实现方法中，收发单元1520，还用于向该第二终端设备的用户面网元发送结束标记指示，该结束标记指示用于指示向该第一终端设备的源用户面网元发送结束标记。
在一种可能的实现方法中，该第二终端设备发生切换，该第二终端设备的用户面网元是该第二终端设备的目标用户面网元；收发单元1520，还用于在通过该目标接入网设备接收来自该第一终端设备的目标用户面网元的指示该第一终端设备的用户面网元发生切换的信息之前，接收该第二终端设备的目标用户面网元的隧道信息；向该第一终端设备的源用户面网元发送该第二终端设备的目标用户面网元的隧道信息以更新该第一终端设备的源用户面网元中的该第二终端设备的用户面网元信息；以及接收来自该第一终端设备的源用户面网元的拒绝更新的响应消息。
在一种可能的实现方法中，收发单元1520，还用于通过该目标接入网设备接收来自该第一终端设备的目标用户面网元的指示该第一终端设备的用户面网元发生切换的信息之后，向该第一终端设备的目标用户面网元发送该第二终端设备的目标用户面网元的隧道信息。
在一种可能的实现方法中，该第二终端设备发生切换，该第二终端设备的用户面网元是该第二终端设备的目标用户面网元；收发单元1520，还用于通过该目标接入网设备接收来自该第一终端设备的目标用户面网元的指示该第一终端设备的用户面网元发生切换的信息之后，接收该第二终端设备的目标用户面网元的隧道信息；以及向该第一终端设备的目标用户面网元发送该第二终端设备的目标用户面网元的隧道信息。
在一种可能的实现方法中，收发单元1520，还用于向该第一终端设备的目标用户面网元发送结束标记指示，该结束标记指示用于指示向该第二终端设备的源用户面网元发送结束标记。
在一种可能的实现方法中，收发单元1520，用于接收来自移动性管理网元的会话修改请求，该会话修改请求包括指示该第一终端设备的用户面网元发生切换的信息。
在一种可能的实现方法中，该第二终端设备发生切换，该第二终端设备的用户面网元是该第二终端设备的目标用户面网元；收发单元1520，还用于通过该目标接入网设备接收来自该第一终端设备的目标用户面网元的指示该第一终端设备的用户面网元发生切换的信息之前，接收该第二终端设备的目标用户面网元的隧道信息；向该第一终端设备的源用户面网元发送该第二终端设备的目标用户面网元的隧道信息。
在一种可能的实现方法中，收发单元1520，还用于向该第一终端设备的源用户面网元发送结束标记指示，该结束标记指示用于指示向该第一终端设备的源接入网设备发送结束标记。
在一种可能的实现方法中，收发单元1520，还用于向该第二终端设备的源用户面网元发送结束标记指示，该结束标记指示用于指示向该第二终端设备的源接入网设备发送结束标记。
在一种可能的实现方法中，收发单元1520，还用于通过该目标接入网设备接收来自该第一终端设备的目标用户面网元的指示该第一终端设备的用户面网元发生切换的信息之后，向该第一终端设备的目标用户面网元发送该第二终端设备的目标用户面网元的隧道信息。
在一种可能的实现方法中，收发单元1520，还用于接收来自该第一终端设备的目标用户面网元的该第二终端设备的用户面网元的隧道信息；若来自该第一终端设备的目标用户面网元的该第二终端设备的用户面网元的隧道信息与该会话管理网元保存的该第二终端设备的用户面网元的隧道信息不同，向该第一终端设备的目标用户面网元发送该第二终端设备的目标用户面网元的隧道信息。
在一种可能的实现方法中，收发单元1520，还用于通过该目标接入网设备接收来自该第一终端设备的目标用户面网元的指示该第一终端设备的用户面网元发生切换的信息之后，接收该第二终端设备的目标用户面网元的隧道信息；向该第一终端设备的源用户面网元和该第一终端设备的目标用户面网元发送该第二终端设备的目标用户面网元的隧道信息。
在一种可能的实现方法中，收发单元1520，还用于向该第一终端设备的源用户面网元发送结束标记指示，该结束标记指示用于指示向该第一终端设备的源接入网设备发送结束标记。
在一种可能的实现方法中，收发单元1520，用于接收来自移动性管理网元或该目标接入网设备的指示该第一终端设备正在进行切换的消息，该消息包括指示该第一终端设备的用户面网元发生切换的信息。
在第二个实施例中，该通信装置用于执行第一终端设备的目标用户面网元的功能，收发单元1520，用于通过目标接入网设备从该第一终端设备的源用户面网元接收第二终端设备的用户面网元的第一隧道信息，该第二终端设备的用户面网元的第一隧道信息用于向该第二终端设备的用户面网元发送该第二终端设备的下行数据；通过该目标接入网设备向会 话管理网元发送该第一终端设备的目标用户面网元的第一隧道信息，该第一终端设备的目标用户面网元的第一隧道信息用于向该第一终端设备的目标用户面网元发送该第一终端设备的下行数据。
在一种可能的实现方法中，该第二终端设备的用户面网元的第一隧道信息包含在该第一终端设备的会话的上下文中，该会话的上下文还包括该会话管理网元的会话端点标识、该会话对应的包检测规则、该会话管理网元的标识信息中的至少一项，该会话管理网元的会话端点标识用于在会话管理网元中标识该会话，该会话对应的包检测规则用于该第一终端设备的目标用户面网元处理该第一终端设备的上行数据包和/或下行数据包。
在一种可能的实现方法中，该会话对应于局域网LAN群组，收发单元1520，还用于通过该目标接入网设备接收来自该第一终端设备的源用户面网元的该LAN群组对应的包检测规则，该LAN群组对应的包检测规则用于该目标用户面网元处理发送给该LAN群组中其他UE的数据包。
在一种可能的实现方法中，收发单元1520，用于通过该目标接入网设备向会话管理网元发送指示该第一终端设备的用户面网元发生切换的信息，该信息包括该第一终端设备的目标用户面网元的第一隧道信息。
在一种可能的实现方法中，该信息还包括该第一终端设备的目标用户面网元的会话端点标识，该第一终端设备的目标用户面网元的会话端点标识用于在该第一终端设备的目标用户面网元中标识该会话。
在一种可能的实现方法中，处理单元1510，用于分配该目标用户面网元的第一隧道信息。
在一种可能的实现方法中，收发单元1520，还用于该从该目标接入网设备接收该目标接入网设备的隧道信息；向该目标接入网设备发送该目标用户面网元的第二隧道信息，该目标用户面网元的第二隧道信息用于该第一终端设备的目标接入网设备向该目标用户面网元发送该第一终端设备的上行数据。
在一种可能的实现方法中，收发单元1520，还用于从会话管理网元接收该第二终端设备的目标用户面网元的第一隧道信息；向该第二终端设备的目标用户面网元发送该第二终端设备的下行数据。
在一种可能的实现方法中，收发单元1520，还用于从会话管理网元接收结束标记指示；根据该结束标记指示，向该第二终端设备的源用户面网元发送结束标记。
在第三个实施例中，该通信装置用于执行第一终端设备的源接入网设备的功能，收发单元1520，用于向该第一终端设备的源用户面网元发送切换准备请求消息，该切换准备请求消息包括该第一终端设备的会话的标识；接收来自该源用户面网元的切换准备响应消息，该切换准备响应消息包括该会话对应的第二终端设备的用户面网元的隧道信息；通过该目标接入网设备向该第一终端设备的目标用户面网元发送该第二终端设备的用户面网元的隧道信息。
在一种可能的实现方法中，收发单元1520，还用于从该目标接入网设备接收该目标接入网设备为该会话分配的无线资源信息；向该第一终端设备发送该无线资源信息。
在一种可能的实现方法中，收发单元1520，还用于从该目标接入网设备接收该会话对应的该目标接入网设备的转发隧道信息；根据该转发隧道信息，向该目标接入网设备发送该第一终端设备的下行数据。
在第四个实施例中，该通信装置用于执行第一终端设备的目标接入网设备的功能，收发单元1520，用于通过该源接入网设备接收来自该第一终端设备的源用户面网元的第二终端设备的用户面网元的隧道信息；向该第一终端设备的目标用户面网元发送该第二终端设备的用户面网元的隧道信息。
在一种可能的实现方法中，收发单元1520，还用于接收来自该第一终端设备的目标用户面网元的指示该第一终端设备的用户面网元发生切换的信息，该信息包括该第一终端设备的目标用户面网元的隧道信息；向会话管理网元发送该信息。
在一种可能的实现方法中，该信息还包括该第一终端设备的目标用户面网元的会话端点标识，该第一终端设备的目标用户面网元的会话端点标识用于在该第一终端设备的目标用户面网元中标识该会话。
在一种可能的实现方法中，该第二终端设备的用户面网元的隧道信息包含在该第一终端设备的会话的上下文中，该会话的上下文还包括该会话管理网元的会话端点标识、该会话对应的包检测规则、该会话管理网元的标识信息中的至少一项，该会话管理网元的会话端点标识用于在会话管理网元中标识该会话，该会话对应的包检测规则用于该第一终端设备的目标用户面网元处理该第一终端设备的上行数据包和/或下行数据包。
在一种可能的实现方法中，该会话对应于局域网LAN群组，收发单元1520，还用于接收来自该第一终端设备的源用户面网元的该LAN群组对应的包检测规则，该LAN群组对应的包检测规则用于该第一终端设备的目标用户面网元处理发送给该LAN群组中其他UE的数据包；向该第一终端设备的目标用户面网元发送该LAN群组对应的包检测规则。
在第五个实施例中，该通信装置用于执行会话管理网元的功能，收发单元1520，用于接收指示第一终端设备发生切换的信息；接收来自第二终端设备的目标用户面网元的该目标用户面网元的第一隧道信息；向该第一终端设备的源用户面网元发送该第二终端设备的目标用户面网元的第一隧道信息，以更新第一终端设备的源用户面网元中的第二终端设备的用户面网元信息；向该第一终端设备的目标用户面网元发送该第二终端设备的目标用户面网元的第一隧道信息；以及向该第一终端设备的目标基站发送该第一终端设备的目标用户面网元的第二隧道信息。
在一种可能的实现方法中，收发单元1520，还用于在接收来自该第二终端设备的目标用户面网元的第二终端设备的该目标用户面网元的第一隧道信息之前，接收指示该第二终端设备发生切换的信息；向该第二终端设备的目标用户面网元发送该第一终端设备的源用户面网元的第一隧道信息。
在一种可能的实现方法中，收发单元1520，还用于向该第一终端设备的源用户面网元发送结束标记指示，该结束标记指示用于指示向该第二终端设备的源用户面网元发送结束标记。
有关上述处理单元1510和收发单元1520更详细的描述可以直接参考上述方法实施例中相关描述直接得到，这里不加赘述。
如图16所示，通信装置1600包括处理器1610和接口电路1620。处理器1610和接口电路1620之间相互耦合。可以理解的是，接口电路1620可以为收发器或输入输出接口。可选的，通信装置1600还可以包括存储器1630，用于存储处理器1610执行的指令或存储处理器1610运行指令所需要的输入数据或存储处理器1610运行指令后产生的数据。
当通信装置1600用于实现上述方法实施例时，处理器1610用于实现上述处理单元 1510的功能，接口电路1620用于实现上述收发单元1520的功能。
可以理解的是，本申请的实施例中的处理器可以是中央处理单元(central processing unit，CPU)，还可以是其它通用处理器、数字信号处理器(digital signal processor，DSP)、专用集成电路(application specific integrated circuit，ASIC)、现场可编程门阵列(field programmable gate array，FPGA)或者其它可编程逻辑器件、晶体管逻辑器件，硬件部件或者其任意组合。通用处理器可以是微处理器，也可以是任何常规的处理器。
本申请的实施例中的方法步骤可以通过硬件的方式来实现，也可以由处理器执行软件指令的方式来实现。软件指令可以由相应的软件模块组成，软件模块可以被存放于随机存取存储器、闪存、只读存储器、可编程只读存储器、可擦除可编程只读存储器、电可擦除可编程只读存储器、寄存器、硬盘、移动硬盘、CD-ROM或者本领域熟知的任何其它形式的存储介质中。一种示例性的存储介质耦合至处理器，从而使处理器能够从该存储介质读取信息，且可向该存储介质写入信息。当然，存储介质也可以是处理器的组成部分。处理器和存储介质可以位于ASIC中。另外，该ASIC可以位于基站或终端中。当然，处理器和存储介质也可以作为分立组件存在于基站或终端中。
在上述实施例中，可以全部或部分地通过软件、硬件、固件或者其任意组合来实现。当使用软件实现时，可以全部或部分地以计算机程序产品的形式实现。所述计算机程序产品包括一个或多个计算机程序或指令。在计算机上加载和执行所述计算机程序或指令时，全部或部分地执行本申请实施例所述的流程或功能。所述计算机可以是通用计算机、专用计算机、计算机网络、基站、用户设备或者其它可编程装置。所述计算机程序或指令可以存储在计算机可读存储介质中，或者从一个计算机可读存储介质向另一个计算机可读存储介质传输，例如，所述计算机程序或指令可以从一个网站站点、计算机、服务器或数据中心通过有线或无线方式向另一个网站站点、计算机、服务器或数据中心进行传输。所述计算机可读存储介质可以是计算机能够存取的任何可用介质或者是集成一个或多个可用介质的服务器、数据中心等数据存储设备。所述可用介质可以是磁性介质，例如，软盘、硬盘、磁带；也可以是光介质，例如，数字视频光盘；还可以是半导体介质，例如，固态硬盘。该计算机可读存储介质可以是易失性或非易失性存储介质，或可包括易失性和非易失性两种类型的存储介质。
在本申请的各个实施例中，如果没有特殊说明以及逻辑冲突，不同的实施例之间的术语和/或描述具有一致性、且可以相互引用，不同的实施例中的技术特征根据其内在的逻辑关系可以组合形成新的实施例。
本申请中，“至少一个”是指一个或者多个，“多个”是指两个或两个以上。“和/或”，描述关联对象的关联关系，表示可以存在三种关系，例如，A和/或B，可以表示：单独存在A，同时存在A和B，单独存在B的情况，其中A，B可以是单数或者复数。在本申请的文字描述中，字符“/”，一般表示前后关联对象是一种“或”的关系；在本申请的公式中，字符“/”，表示前后关联对象是一种“相除”的关系。
可以理解的是，在本申请的实施例中涉及的各种数字编号仅为描述方便进行的区分，并不用来限制本申请的实施例的范围。上述各过程的序号的大小并不意味着执行顺序的先后，各过程的执行顺序应以其功能和内在逻辑确定。

Claims (30)

  1. 一种切换方法，其特征在于，应用于第一终端设备从源接入网设备切换到目标接入网设备，包括：
    会话管理网元通过所述目标接入网设备接收来自所述第一终端设备的目标用户面网元的指示所述第一终端设备的用户面网元发生切换的信息，所述指示所述第一终端设备的用户面网元发生切换的信息包括所述第一终端设备的目标用户面网元的隧道信息；
    所述会话管理网元向第二终端设备的用户面网元发送所述第一终端设备的目标用户面网元的隧道信息，以更新所述第二终端设备的用户面网元中的所述第一终端设备的用户面网元信息，所述第一终端设备的目标用户面网元的隧道信息用于向所述第一终端设备的目标用户面网元发送所述第一终端设备的下行数据。
  2. 如权利要求1所述的方法，其特征在于，所述方法还包括：
    所述会话管理网元向所述第二终端设备的用户面网元发送结束标记指示，所述结束标记指示用于指示向所述第一终端设备的源用户面网元发送结束标记。
  3. 如权利要求1或2所述的方法，其特征在于，所述第二终端设备发生切换，所述第二终端设备的用户面网元是所述第二终端设备的目标用户面网元；
    所述会话管理网元通过所述目标接入网设备接收来自所述第一终端设备的目标用户面网元的指示所述第一终端设备的用户面网元发生切换的信息之前，所述方法还包括：
    所述会话管理网元接收所述第二终端设备的目标用户面网元的隧道信息；
    所述会话管理网元向所述第一终端设备的源用户面网元发送所述第二终端设备的目标用户面网元的隧道信息以更新所述第一终端设备的源用户面网元中的所述第二终端设备的用户面网元信息；
    所述会话管理网元接收来自所述第一终端设备的源用户面网元的拒绝更新的响应消息。
  4. 如权利要求3所述的方法，其特征在于，所述会话管理网元通过所述目标接入网设备接收来自所述第一终端设备的目标用户面网元的指示所述第一终端设备的用户面网元发生切换的信息之后，所述方法还包括：
    所述会话管理网元向所述第一终端设备的目标用户面网元发送所述第二终端设备的目标用户面网元的隧道信息。
  5. 如权利要求1或2所述的方法，其特征在于，所述第二终端设备发生切换，所述第二终端设备的用户面网元是所述第二终端设备的目标用户面网元；
    会话管理网元通过所述目标接入网设备接收来自所述第一终端设备的目标用户面网元的指示所述第一终端设备的用户面网元发生切换的信息之后，所述方法还包括：
    会话管理网元接收所述第二终端设备的目标用户面网元的隧道信息；
    所述会话管理网元向所述第一终端设备的目标用户面网元发送所述第二终端设备的目标用户面网元的隧道信息。
  6. 如权利要求4或5所述的方法，其特征在于，所述方法还包括：
    所述会话管理网元向所述第一终端设备的目标用户面网元发送结束标记指示，所述结束标记指示用于指示向所述第二终端设备的源用户面网元发送结束标记。
  7. 如权利要求4至6中任一项所述的方法，其特征在于，所述会话管理网元通过所述 目标接入网设备接收来自所述第一终端设备的目标用户面网元的指示所述第一终端设备的用户面网元发生切换的信息，包括：
    所述会话管理网元接收来自移动性管理网元的会话修改请求，所述会话修改请求包括所述指示所述第一终端设备的用户面网元发生切换的信息。
  8. 如权利要求1所述的方法，其特征在于，所述第二终端设备发生切换，所述第二终端设备的用户面网元是所述第二终端设备的目标用户面网元；所述会话管理网元通过所述目标接入网设备接收来自所述第一终端设备的目标用户面网元的指示所述第一终端设备的用户面网元发生切换的信息之前，所述方法还包括：
    所述会话管理网元接收所述第二终端设备的目标用户面网元的隧道信息；
    所述会话管理网元向所述第一终端设备的源用户面网元发送所述第二终端设备的目标用户面网元的隧道信息。
  9. 如权利要求8所述的方法，其特征在于，所述方法还包括：
    所述会话管理网元向所述第一终端设备的源用户面网元发送结束标记指示，所述结束标记指示用于指示向所述第一终端设备的源接入网设备发送结束标记。
  10. 如权利要求8所述的方法，其特征在于，所述方法还包括：
    所述会话管理网元向所述第二终端设备的源用户面网元发送结束标记指示，所述结束标记指示用于指示向所述第二终端设备的源接入网设备发送结束标记。
  11. 如权利要求8至10中任一项所述的方法，其特征在于，所述会话管理网元通过所述目标接入网设备接收来自所述第一终端设备的目标用户面网元的指示所述第一终端设备的用户面网元发生切换的信息之后，所述方法还包括：
    所述会话管理网元向所述第一终端设备的目标用户面网元发送所述第二终端设备的目标用户面网元的隧道信息。
  12. 如权利要求11所述的方法，其特征在于，所述方法还包括：
    所述会话管理网元接收来自所述第一终端设备的目标用户面网元的所述第二终端设备的源用户面网元的隧道信息；
    所述会话管理网元向所述第一终端设备的目标用户面网元发送所述第二终端设备的目标用户面网元的隧道信息，包括：
    若来自所述第一终端设备的目标用户面网元的所述第二终端设备的源用户面网元的隧道信息与所述会话管理网元保存的所述第二终端设备的目标用户面网元的隧道信息不同，所述会话管理网元向所述第一终端设备的目标用户面网元发送所述第二终端设备的目标用户面网元的隧道信息。
  13. 如权利要求1所述的方法，其特征在于，所述会话管理网元通过所述目标接入网设备接收来自所述第一终端设备的目标用户面网元的指示所述第一终端设备的用户面网元发生切换的信息之后，所述方法还包括：
    所述会话管理网元接收所述第二终端设备的目标用户面网元的隧道信息；
    所述会话管理网元向所述第一终端设备的源用户面网元和所述第一终端设备的目标用户面网元发送所述第二终端设备的目标用户面网元的隧道信息。
  14. 如权利要求13所述的方法，其特征在于，所述方法还包括：
    所述会话管理网元向所述第一终端设备的源用户面网元发送结束标记指示，所述结束标记指示用于指示向所述第一终端设备的源接入网设备发送结束标记。
  15. 如权利要求8至14中任一项所述的方法，其特征在于，所述会话管理网元通过所述目标接入网设备接收来自所述第一终端设备的目标用户面网元的指示所述第一终端设备的用户面网元发生切换的信息，包括：
    会话管理网元接收来自移动性管理网元或所述目标接入网设备的指示所述第一终端设备正在进行切换的消息，所述消息包括所述指示所述第一终端设备的用户面网元发生切换的信息。
  16. 一种切换方法，其特征在于，应用于第一终端设备从源接入网设备切换到目标接入网设备，包括：
    所述第一终端设备的目标用户面网元通过所述目标接入网设备从所述第一终端设备的源用户面网元接收第二终端设备的用户面网元的第一隧道信息，所述第二终端设备的用户面网元的第一隧道信息用于向所述第二终端设备的用户面网元发送所述第二终端设备的下行数据；
    所述目标用户面网元通过所述目标接入网设备向会话管理网元发送所述第一终端设备的目标用户面网元的第一隧道信息，所述第一终端设备的目标用户面网元的第一隧道信息用于向所述第一终端设备的目标用户面网元发送所述第一终端设备的下行数据。
  17. 如权利要求16所述的方法，其特征在于，所述第二终端设备的用户面网元的第一隧道信息包含在所述第一终端设备的会话的上下文中，所述会话的上下文还包括所述会话管理网元的会话端点标识、所述会话对应的包检测规则、所述会话管理网元的标识信息中的至少一项，所述会话管理网元的会话端点标识用于在会话管理网元中标识所述会话，所述会话对应的包检测规则用于所述第一终端设备的目标用户面网元处理所述第一终端设备的上行数据包和/或下行数据包。
  18. 如权利要求17所述的方法，其特征在于，所述会话对应于局域网LAN群组，所述方法还包括：
    所述目标用户面网元通过所述目标接入网设备接收来自所述第一终端设备的源用户面网元的所述LAN群组对应的包检测规则，所述LAN群组对应的包检测规则用于所述目标用户面网元处理发送给所述LAN群组中其他UE的数据包。
  19. 如权利要求16至18中任一项所述的方法，其特征在于，所述目标用户面网元通过所述目标接入网设备向会话管理网元发送所述第一终端设备的目标用户面网元的第一隧道信息，包括：
    所述目标用户面网元通过所述目标接入网设备向会话管理网元发送指示所述第一终端设备的用户面网元发生切换的信息，所述指示所述第一终端设备的用户面网元发生切换的信息包括所述第一终端设备的目标用户面网元的第一隧道信息。
  20. 如权利要求19所述的方法，其特征在于，所述指示所述第一终端设备的用户面网元发生切换的信息还包括所述第一终端设备的目标用户面网元的会话端点标识，所述第一终端设备的目标用户面网元的会话端点标识用于在所述第一终端设备的目标用户面网元中标识所述会话。
  21. 如权利要求16至20中任一项所述的方法，其特征在于，所述方法还包括：
    所述目标用户面网元从所述目标接入网设备接收所述目标接入网设备的隧道信息；
    所述目标用户面网元向所述目标接入网设备发送所述目标用户面网元的第二隧道信息，所述目标用户面网元的第二隧道信息用于所述第一终端设备的目标接入网设备向所述 目标用户面网元发送所述第一终端设备的上行数据。
  22. 如权利要求16至21中任一项所述的方法，其特征在于，所述方法还包括：
    所述目标用户面网元从会话管理网元接收所述第二终端设备的目标用户面网元的第一隧道信息；
    所述目标用户面网元向所述第二终端设备的目标用户面网元发送所述第二终端设备的下行数据。
  23. 如权利要求16至22中任一项所述的方法，其特征在于，还包括：
    所述目标用户面网元从会话管理网元接收结束标记指示；
    所述目标用户面网元根据所述结束标记指示，向所述第二终端设备的源用户面网元发送结束标记。
  24. 一种通信装置，其特征在于，包括用于执行如权利要求1至15中任一项所述方法的模块。
  25. 一种通信装置，其特征在于，包括用于执行如权利要求16至23中任一项所述方法的模块。
  26. 一种通信装置，其特征在于，包括处理器和接口电路，所述接口电路用于接收来自所述通信装置之外的其它通信装置的信号并传输至所述处理器或将来自所述处理器的信号发送给所述通信装置之外的其它通信装置，所述处理器通过逻辑电路或执行代码指令用于实现如权利要求1至15中任一项所述的方法。
  27. 一种通信装置，其特征在于，包括处理器和接口电路，所述接口电路用于接收来自所述通信装置之外的其它通信装置的信号并传输至所述处理器或将来自所述处理器的信号发送给所述通信装置之外的其它通信装置，所述处理器通过逻辑电路或执行代码指令用于实现如权利要求16至23中任一项所述的方法。
  28. 一种计算机程序产品，其特征在于，包括计算机程序，当所述计算机程序被通信装置执行时，实现如权利要求1至23中任一项所述的方法。
  29. 一种计算机可读存储介质，其特征在于，所述存储介质中存储有计算机程序或指令，当所述计算机程序或指令被通信装置执行时，实现如权利要求1至23中任一项所述的方法。
  30. 一种通信系统，其特征在于，包括如权利要求1至15中任一项所述的会话管理网元，和第一终端设备的目标用户面网元；
    所述第一终端设备的目标用户面网元，用于通过所述第一终端的目标接入网设备向所述会话管理网元发送指示所述第一终端设备的用户面网元发生切换的信息，所述指示所述第一终端设备的用户面网元发生切换的信息包括所述第一终端设备的目标用户面网元的隧道信息。
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