Communication method, communication system and communication apparatus

Abstract

Disclosed in the present application are a communication method, a communication system and a communication apparatus. The method relates to the technical field of communications. The method comprises: a first network device receiving a handover request message which is from a second network device, wherein the handover request message instructs a terminal device to request a handover from the second network device to the first network device, the handover request message also indicates a first serial number, the first serial number is the serial number of the newest multicast and broadcast service (MBS) data packet which is received by the second network device and is from a core network device, the first serial number is less than a second serial number, and the second serial number is the serial number of the latest MBS data packet which is received by the first network device and is from the core network device; and the first network device sending a handover response message to the second network device, wherein the handover response message instructs the second network device not to forward an MBS data packet. On the basis of the method, saving on resource overheads is facilitated.

Description

Communication method, communication system and communication device

[0001] This application claims priority to the Chinese patent application filed with the State Intellectual Property Office of China on September 26, 2023, with application number 202311257921.1 and application name “Communication Method, Communication System and Communication Device”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application relates to the field of communication technology, and in particular to a communication method, a communication system, and a communication device. Background Art

[0003] Multicast and Broadcast Service (MBS) is a service for multiple user equipment (UE), such as live broadcast service, public safety service, batch software update service, etc. MBS service comes from the data server. First, the data server sends the MBS data to the core network device, then the core network device sends the MBS data to the base station, and finally the base station sends the MBS data to one or more UEs receiving the MBS service at the same time. Network handover refers to the process of UE switching from the source base station to the target base station. During the UE's MBS process, network handover is triggered. When the MBS progress of the target base station is faster than that of the source base station, in order to achieve lossless handover of the UE, the source base station will establish a forwarding tunnel with the target base station. The forwarding tunnel is used to forward MBS data packets to avoid the UE being unable to receive some MBS data packets during the handover process due to the target base station's MBS progress being too fast.

[0004] To reduce handover interruption time, the 3rd Generation Partnership Project (3GPP) Release 16 introduced dual active protocol stack (DAPS) handover. During the DAPS handover process, the UE will maintain its user plane connection with the source base station and continue to transmit data with the source base station until the UE completes the connection with the target base station and transmits data. DAPS handover requires that the UE can simultaneously receive and transmit data with the source base station and the target base station within a short period of time. When using DAPS handover, the UE can also receive MBS data packets from the source base station during the handover process. In this case, the target base station establishes a data forwarding tunnel with the source base station to forward MBS data packets. Then, during the handover process, the terminal device will receive MBS data packets from the source base station while receiving MBS data packets sent by the target base station and forwarded by the source base station through the forwarding tunnel. The terminal device may receive a large number of duplicate data packets, wasting resources.

[0005] Summary of the Invention

[0006] The embodiments of the present application provide a communication method, a communication system, and a communication device, which are conducive to saving resource overhead.

[0007] In a first aspect, the present application provides a communication method, applied to a first network device, the method comprising: receiving a switching request message from a second network device, the switching request message indicating that the terminal device requests to switch from the second network device to the first network device, the switching request message also indicating a first sequence number, the first sequence number being the sequence number of the latest multicast broadcast service MBS data packet received by the second network device from the core network device, the first sequence number being smaller than the second sequence number, the second sequence number being the sequence number of the latest MBS data packet received by the first network device from the core network device; and sending a switching response message to the second network device, the switching response message indicating that the second network device does not forward the MBS data packet.

[0008] Based on the method described in the first aspect, before the terminal device switching is completed, the first network device instructs the second network device not to forward the MBS data packet through a switching response message. During the switching period, the terminal device can directly receive the MBS data packet through the first network device and the second network device, and will not receive the MBS data packet sent by the first network device and forwarded by the second network device. This can avoid the situation where the terminal device receives duplicate data packets through the first network device and the second network device, which is beneficial to saving resource overhead.

[0009] In a possible implementation, the handover response message includes user plane transport layer information of the first network device, where the user plane transport layer information is used to establish a forwarding tunnel with the second network device.

[0010] In a possible implementation manner, the handover response message includes first indication information, where the first indication information indicates not to forward the MBS data packet.

[0011] In a possible implementation manner, the method further includes: receiving a first report from the terminal device, where the first report indicates MBS data packets lost by the terminal device.

[0012] In one possible implementation, the method further includes: determining, based on the first report, that among the MBS data packets lost by the terminal device, there is at least one MBS data packet whose sequence number is smaller than the second sequence number; and sending a switching success message to the second network device, where the switching success message indicates a request to forward the MBS data packet lost by the terminal device.

[0013] In a possible implementation, the switching success message includes second indication information, where the second indication information indicates a request to forward the MBS data packets lost by the terminal device.

[0014] In one possible implementation, the method further includes: receiving one or more MBS data packets from the second network device; and sending one or more MBS data packets to the terminal device. Based on this implementation, the terminal device can receive lost data packets, ensuring data integrity and achieving lossless switching.

[0015] In a possible implementation, the switching success message indicates the sequence number of the MBS data packet lost by the terminal device, and the one or more MBS data packets are the MBS data packets lost by the terminal device.

[0016] In one possible implementation, the switching success message indicates a third sequence number, which is the smallest sequence number among the sequence numbers of the MBS data packets lost by the terminal device, and the sequence number of any one of the sequence numbers of one or more MBS data packets is greater than or equal to the third sequence number.

[0017] In a second aspect, the present application provides a communication method, applied to a second network device, the method comprising: sending a switching request message to the first network device, the switching request indicating that the terminal device requests to switch from the second network device to the first network device, the switching request message also indicating a first sequence number, the first sequence number being the sequence number of the latest multicast broadcast service MBS data packet received by the second network device from the core network device at the first time point, the first sequence number being smaller than the second sequence number, the second sequence number being the sequence number of the latest MBS data packet received by the first network device from the core network device at the first time; receiving a switching response message from the second network device, the switching response message indicating that the MBS data packet is not to be forwarded.

[0018] Among them, the beneficial effects corresponding to the second aspect can be found in the description corresponding to the above-mentioned first aspect, and will not be repeated here.

[0019] In a possible implementation, the handover response message includes user plane transport layer information of the first network device, where the user plane transport layer information is used to establish a forwarding tunnel between the first network device and the second network device.

[0020] In a possible implementation manner, the handover response message includes first indication information, where the first indication information indicates not to forward the MBS data packet.

[0021] In a possible implementation, the method further includes: receiving a switching success message from the first network device, the switching success message indicating a request to forward the MBS data packets lost by the terminal device; and sending one or more MBS data packets to the first network device.

[0022] In a possible implementation, the switching success message includes second indication information, where the second indication information indicates a request to forward the MBS data packets lost by the terminal device.

[0023] In a possible implementation, the switching success message indicates the sequence number of the MBS data packet lost by the terminal device, and the one or more MBS data packets are the MBS data packets lost by the terminal device.

[0024] In a third aspect, the present application provides a communication method, applied to a first network device, the method comprising: receiving a switching request message from a second network device, the switching request message indicating that the terminal device requests to switch from the second network device to the first network device, the switching request message also indicating a first sequence number, the first sequence number being the sequence number of the latest multicast broadcast service MBS data packet received by the second network device from the core network device, the first sequence number being smaller than the second sequence number, the second sequence number being the sequence number of the latest MBS data packet received by the first network device from the core network device; sending a switching response message to the second network device, the switching response message not including user plane transport layer information, the user plane transport layer information being used to establish a forwarding tunnel between the first network device and the second network device; receiving a first report from the terminal device, the first report indicating data packets lost by the terminal device; determining based on the first report that among the MBS data packets lost by the terminal device, there is at least one MBS data packet whose sequence number is smaller than the second sequence number; sending a switching success message to the second network device, the switching success message indicating a request to forward the MBS data packet lost by the terminal device, the switching success message including user plane transport layer information.

[0025] Based on the method described in the third aspect, since the handover response message does not include user plane transport layer information, the second network device cannot establish a forwarding tunnel with the first network device. As a result, during the handover process of the terminal device, the second network device will not forward MBS data packets to the first network device. During the handover period, the terminal device can directly receive MBS data from the first network device and the second network device, but will not receive MBS data packets sent by the first network device and forwarded by the second network device. Therefore, the terminal device can avoid receiving duplicate data packets through the first network device and the second network device, which is beneficial for saving resource overhead. In addition, when the terminal device loses a data packet, the handover success message sent by the first network device to the second network device includes user plane transport layer information. Therefore, the second network device can establish a forwarding tunnel with the first network device. The second network device sends one or more MBS data packets to the first network device through the forwarding tunnel, and the first network device forwards the one or more data packets to the terminal device. Therefore, the terminal device can receive the lost data packets, ensure data integrity, and achieve lossless handover.

[0026] In a possible implementation, the switching success message includes second indication information, where the second indication information indicates a request to forward the MBS data packets lost by the terminal device.

[0027] In a possible implementation manner, the method further includes: receiving one or more MBS data packets from the second network device; and sending one or more MBS data packets to the terminal device.

[0028] In a possible implementation, the switching success message indicates the sequence number of the MBS data packet lost by the terminal device, and the one or more MBS data packets are the MBS data packets lost by the terminal device.

[0029] In one possible implementation, the switching success message indicates a third sequence number, which is the smallest sequence number among the sequence numbers of the MBS data packets lost by the terminal device, and the sequence number of any one of the sequence numbers of one or more MBS data packets is greater than or equal to the third sequence number.

[0030] In a fourth aspect, the present application provides a communication method, which is applied to a second network device, the method comprising: sending a handover request message to a first network device, the handover request message indicating that the terminal device requests to be handed over from the second network device to the first network device, the handover request message also indicating a first sequence number, the first sequence number being the sequence number of the latest multicast broadcast service MBS data packet received by the second network device from the core network device, the first sequence number being less than the second sequence number, the second sequence number being the sequence number of the latest MBS data packet received by the first network device from the core network device; receiving a handover response message from the first network device, the handover response message not including user plane transport layer information, the user plane transport layer information being used to establish a forwarding tunnel between the first network device and the second network device; receiving a handover success message from the first network device, the handover success message indicating a request to forward the MBS data packet lost by the terminal device, the handover success message including user plane transport layer information. The beneficial effects corresponding to the fourth aspect can be found in the description corresponding to the third aspect above, which will not be repeated here.

[0031] In a possible implementation, the switching success message includes second indication information, where the second indication information indicates a request to forward the MBS data packets lost by the terminal device.

[0032] In a possible implementation manner, the method further includes: sending one or more MBS data packets to the first network device.

[0033] In a possible implementation, the switching success message indicates the sequence number of the MBS data packet lost by the terminal device, and the one or more MBS data packets are the MBS data packets lost by the terminal device.

[0034] In one possible implementation, the switching success message indicates a third sequence number, which is the smallest sequence number among the sequence numbers of the MBS data packets lost by the terminal device, and the sequence number of any one of the sequence numbers of one or more MBS data packets is greater than or equal to the third sequence number.

[0035] In a fifth aspect, the present application provides a communication device, which may also be a chip system. The communication device may perform the method described in the first or third aspect. The functions of the communication device may be implemented by hardware, or by hardware executing corresponding software implementations. The hardware or software includes one or more units or modules corresponding to the above-mentioned functions. The units or modules may be software and / or hardware. The operations and beneficial effects performed by the communication device may refer to the methods and beneficial effects described in the first or third aspect above, and any repetitions will not be repeated.

[0036] In a sixth aspect, the present application provides a communication device, which may also be a chip system. The communication device may perform the method described in the second aspect or the fourth aspect. The functions of the communication device may be implemented by hardware, or by hardware executing corresponding software implementations. The hardware or software includes one or more units or modules corresponding to the above-mentioned functions. The units or modules may be software and / or hardware. The operations and beneficial effects performed by the communication device may refer to the methods and beneficial effects described in the second aspect or the fourth aspect above, and any repetitions will not be repeated.

[0037] In a seventh aspect, the present application provides a communication device, which includes a processor. When the processor calls a computer program in a memory, the method described in any one of the first aspect or the second aspect and its possible implementation method are executed.

[0038] In a possible implementation, the communication device further includes a memory, and the memory and the processor are coupled to each other. Optionally, the memory and the processor are integrated together.

[0039] In a possible implementation, the communication device further includes a transceiver, which is used to transmit and receive data and / or signaling.

[0040] In an eighth aspect, the present application provides a communication device, which includes a processor and an interface circuit, wherein the interface circuit is used to receive signals from other communication devices outside the communication device and transmit them to the processor or send signals from the processor to other communication devices outside the communication device, and the processor is used to implement the method described in any one of the first to fourth aspects and its possible implementation methods through logic circuits or execution code instructions.

[0041] In the ninth aspect, the present application provides a computer-readable storage medium, which stores a computer program or instruction. When the computer program or instruction is executed by a communication device, it implements any one of the methods in the first to fourth aspects and its possible implementation methods.

[0042] In the tenth aspect, an embodiment of the present application provides a computer program or computer program product, including code or instructions. When the code or instructions are run on a computer, the computer executes the method described in any one of the first to fourth aspects and its possible implementation methods.

[0043] In an eleventh aspect, an embodiment of the present application provides a communication system, which includes the communication device described in the fifth aspect and the communication device described in the sixth aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] FIG1 is a schematic diagram of data transmission during network switching according to an embodiment of the present application;

[0045] FIG2 is a schematic diagram of a communication system provided in an embodiment of the present application;

[0046] FIG3 is a flow chart of a communication method provided in an embodiment of the present application;

[0047] FIG4 is a schematic diagram of a terminal device obtaining a lost data packet according to an embodiment of the present application;

[0048] FIG5 is a flow chart of another communication method provided in an embodiment of the present application;

[0049] FIG6 is a schematic structural diagram of a communication device provided in an embodiment of the present application;

[0050] FIG7 is a schematic structural diagram of another communication device provided in an embodiment of the present application;

[0051] FIG8 is a schematic structural diagram of a chip provided in an embodiment of the present application. DETAILED DESCRIPTION

[0052] The specific embodiments of the present application are further described in detail below with reference to the accompanying drawings.

[0053] The terms "first" and "second" and the like in the specification, claims, and drawings of this application are used to distinguish between different objects, not to describe a particular order. Furthermore, the terms "including" and "having," and any variations thereof, are intended to cover non-exclusive inclusions. For example, a process, method, system, product, or apparatus comprising a series of steps or elements is not limited to the listed steps or elements, but may optionally include steps or elements not listed, or may optionally include other steps or elements inherent to the process, method, product, or apparatus.

[0054] References herein to "embodiments" mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0055] In this application, "at least one (item)" refers to one or more, "more than one" refers to two or more, "at least two (items)" refers to two or three and more than three, and "and / or" is used to describe the corresponding relationship of associated objects, indicating that there can be three relationships. For example, "A and / or B" can mean: only A exists, only B exists, and A and B exist at the same time, where A and B can be singular or plural. The character " / " generally indicates that the previous and next associated objects are in an "or" relationship. "At least one of the following items" or similar expressions refers to any combination of these items, including any combination of single or plural items. For example, at least one of a, b or c can mean: a, b, c, "a and b", "a and c", "b and c", or "a and b and c", where a, b, c can be single or multiple.

[0056] The following describes the system architecture of the embodiment of the present application:

[0057] To facilitate understanding of the technical solutions of the embodiments of the present application, the system architecture of the method provided in the embodiments of the present application is briefly described below. It is understood that the system architecture described in the embodiments of the present application is for the purpose of more clearly illustrating the technical solutions of the embodiments of the present application and does not constitute a limitation on the technical solutions provided in the embodiments of the present application.

[0058] The technical solutions of the embodiments of the present application can be applied to various communication systems, such as satellite communication systems and traditional mobile communication systems. The satellite communication system can be integrated with a traditional mobile communication system (i.e., a terrestrial communication system). Communication systems include, for example, wireless local area network (WLAN) communication systems, wireless fidelity (WiFi) systems, long term evolution (LTE) systems, LTE frequency division duplex (FDD) systems, LTE time division duplex (TDD) systems, fifth generation (5G) systems or new radio (NR), sixth generation (6G) systems, and other future communication systems. It also supports communication systems that integrate multiple wireless technologies. For example, it can also be applied to systems that integrate non-terrestrial networks (NTNs) such as drones, satellite communication systems, and high altitude platform stations (HAPS) communications with terrestrial mobile communication networks.

[0059] is an example of a communication system applicable to an embodiment of the present application. The communication system includes at least two network devices and at least one terminal device. FIG1 takes two network devices (a first network device and a second network device) and one terminal device as an example. These multiple terminal devices can be cellular phones, smart phones, portable computers, handheld communication devices, handheld computing devices, satellite radio devices, global positioning systems, personal digital assistants (PDAs) and / or any other suitable devices for communicating on wireless communication systems, and can all be connected to the network devices. These multiple terminal devices are all capable of communicating with the network devices. The number of terminal devices and network devices in FIG1 is only an example, and the embodiments of the present application do not limit this.

[0060] The second network device is the source network device (also known as the working network device or the serving network device) of the terminal device, and the first network device is the target network device (also known as the backup network device) of the terminal device, that is, the network device that provides services to the terminal device after the switch. "Switching" refers to the switching of the network device providing services to the terminal device, such as "cell switching". When the terminal device moves from the area corresponding to the second network device to the area where the first network device is located, the terminal device will disconnect from the second network device, and the first network device will provide services to the terminal device.

[0061] The terminal device involved in the embodiments of the present application, which may also be referred to as a terminal, is an entity on the user side for receiving or transmitting signals. The terminal device can be a device that provides voice and / or data connectivity to the user, for example, a handheld device with wireless connection function, a vehicle-mounted device, etc. The terminal device can also be other processing devices connected to a wireless modem. The terminal device can communicate with a radio access network (RAN). The terminal device can also be called a wireless terminal, a subscriber unit, a subscriber station, a mobile station, a mobile station, a mobile station, a remote station, an access point, a remote terminal, an access terminal, a user terminal, a user agent, a user device, or a UE, etc. The terminal device can be a mobile terminal, such as a mobile phone (or "cellular" phone) and a computer with a mobile terminal, for example, a portable, pocket-sized, handheld, computer-built-in or vehicle-mounted mobile device, which exchanges voice and / or data with a radio access network. For example, the terminal device may also be a personal communication service (PCS) phone, a cordless phone, a session initiation protocol (SIP) phone, a wireless local loop (WLL) station, a personal digital assistant (PDA), etc. Common terminal devices include, for example, mobile phones, tablet computers, laptop computers, PDAs, mobile internet devices (MIDs), and wearable devices such as smart watches, smart bracelets, and pedometers, but the embodiments of the present application are not limited thereto.

[0062] The embodiments of this application do not limit the device form factor of the terminal. The device used to implement the terminal's function can be a terminal; it can also be a device that supports the terminal in implementing the function, such as a chip system. The device can be installed in the terminal or used in conjunction with the terminal. In the embodiments of this application, the chip system can be composed of a chip or include a chip and other discrete components.

[0063] A network device is an entity on the network side that is used to send signals, receive signals, or both send and receive signals. A network device can be a device deployed in a radio access network (RAN) to provide wireless communication functions for terminals.

[0064] In one possible scenario, a network device may be a device with base station functionality, such as an evolved NodeB (eNodeB), a transmitting and receiving point (TRP), a transmitting point (TP), a next-generation NodeB (gNB), a next-generation base station in a 6G mobile communication system, an integrated access and backhaul (IAB) node, or a non-terrestrial network device, i.e., a device that can be deployed on a high-altitude platform or satellite. A network device may be a transmission reception point (TRP), a base station, or various forms of control nodes, such as a network controller or wireless controller. Specifically, network devices can include various forms of macro base stations, micro base stations (also known as small cells) in heterogeneous network (HetNet) scenarios, relay stations, access points (APs), radio network controllers (RNCs), node Bs (NBs), base station controllers (BSCs), base transceiver stations (BTSs), home base stations (e.g., home evolved node Bs, or home node Bs, HNBs), baseband units (BBUs) and remote radio units (RRUs) in distributed base station scenarios, transmission points (TRPs), transmitting points (TPs), mobile switching centers, and the like. They can also be base station antenna panels. A control node can connect to multiple base stations and configure resources for multiple terminals covered by multiple base stations. In systems using different wireless access technologies, the names of devices with base station functionality may vary. For example, it can be a gNB in ​​5G, or a network-side device in a network after 5G, or a network device in a future evolved public land mobile (communication) network (public land mobile network, PLMN) network, or a device that performs base station functions in device-to-device (D2D) communication, machine-to-machine (M2M) communication, and vehicle network communication, etc. This application does not limit the specific name of the network device.The network equipment may also be an open access network (O-RAN or ORAN), a baseband pool (BBU pool) and RRU under a cloud radio access network (CRAN), etc.

[0065] In another possible scenario, multiple network devices collaborate to assist the terminal in achieving wireless access, and different network devices respectively implement part of the functions of the base station. For example, the network device may include a centralized unit (CU), a distributed unit (DU), a CU-control plane (CP), a CU-user plane (UP), or a radio unit (RU). The CU and DU may be set separately, or may be included in the same network element, such as a baseband unit (BBU). The RU may be included in a radio frequency device or radio frequency unit, such as a remote radio unit (RRU), an active antenna unit (AAU), or a remote radio head (RRH). It is understandable that the network device may be a CU node, a DU node, or a device including a CU node and a DU node. In addition, the CU may be divided into a network device in the access network RAN, or the CU may be divided into a network device in the core network CN, without limitation here.

[0066] In different systems, CU (or CU-CP and CU-UP), DU or RU may also have different names, but those skilled in the art can understand their meanings. For example, in the ORAN system, CU may also be called O-CU (Open CU), DU may also be called O-DU, CU-CP may also be called O-CU-CP, CU-UP may also be called O-CU-UP, and RU may also be called O-RU. For the convenience of description, this application uses CU, CU-CP, CU-UP, DU and RU as examples for description. Any unit of CU (or CU-CP, CU-UP), DU and RU in this application can be implemented by a software module, a hardware module, or a combination of a software module and a hardware module.

[0067] By way of example and not limitation, in embodiments of the present application, a network device may have a mobile characteristic, for example, a network device may be a mobile device. In some embodiments, the network device may be a satellite or a balloon station. For example, the satellite may be a low earth orbit (LEO) satellite, a medium earth orbit (MEO) satellite, a geostationary earth orbit (GEO) satellite, a high elliptical orbit (HEO) satellite, etc.

[0068] In the embodiments of the present application, the form of the network device is not limited. The device used to implement the function of the network device can be a network device; it can also be a device that can support the network device to implement the function, such as a chip system. The device can be installed in the network device or used in conjunction with the network device.

[0069] Multicast and Broadcast Service (MBS) is a service for multiple terminal devices, such as live broadcast services, public safety services, and batch software update services. MBS services originate from data servers. First, the data server sends the MBS data to the core network device, which then sends the MBS data to the base station. Finally, the base station simultaneously sends the MBS data to one or more terminal devices receiving the MBS service. Network handover refers to the process of switching a terminal device from a source base station to a target base station. During the MBS process, a network handover is triggered. To ensure lossless handover of the terminal device, the source base station establishes a forwarding tunnel with the target base station.

[0070] For example, as shown in Figure 2, the last MBS packet currently received by the source base station is sequence number 4, but the earliest MBS packet currently received by the target base station is sequence number 9. The sequence number of the MBS packet currently received by the target base station is greater than the sequence number of the MBS packet currently received by the source base station, which can be understood as the target base station's MBS data reception progress being faster than the source base station. Before the handover, the terminal device could receive MBS packets with sequence numbers 1 to 4, but after handover to the target base station, it can only receive MBS packets with sequence numbers 9 and later. During the network handover, the terminal device cannot receive MBS packets, meaning that it cannot receive packets with sequence numbers 5 to 8. Therefore, the target base station decides to establish a data forwarding tunnel with the source base station and obtains the packets between MBS packet 4 and MBS packet 9, namely, MBS packets with sequence numbers 5 to 8. The source base station then forwards the MBS packets with sequence numbers 5 to 8 subsequently sent by the core network device to the target base station, allowing the target base station to send MBS packets with sequence numbers 5 to 8 to the terminal device, achieving lossless handover for the terminal device.

[0071] The 3rd Generation Partnership Project (3GPP) Release 16 introduced dual active protocol stack (DAPS) switching. During the DAPS switching process, the terminal device will maintain its user plane connection with the source base station and continue to transmit data with the source base station until the terminal device completes the connection establishment with the target base station and transmits data with the target base station. In the DAPS switching scenario, the terminal device can still transmit data with the source base station during the switching process. If the target base station establishes a forwarding tunnel with the source base station and forwards MBS data packets during the switching process of the terminal device, the terminal device will receive MBS data from the source base station while receiving MBS data sent by the target base station from the source base station through the forwarding tunnel. The terminal device may receive a large number of duplicate data packets, wasting resources.

[0072] For example, in Figure 2, if the terminal device uses DAPS handover, during the handover process, the terminal device can receive packets with sequence numbers 5 to 8 from the source base station. Therefore, if the source base station still forwards packets with sequence numbers 5 to 8 to the target base station, it will waste resources. How to save resource overhead is an urgent problem that needs to be solved.

[0073] In order to save resource overhead, an embodiment of the present application proposes a communication method, as shown in Figure 3, which includes steps 301 and 302. The execution entities corresponding to the method shown in Figure 3 are the first network device and the second network device, respectively. Alternatively, the execution entity of the method shown in Figure 3 can be a chip in the first network device and a chip in the second network device. Figure 3 is illustrated using the first network device and the second network device as an example. The embodiment of the present application does not limit the execution entity of the communication method. The terminal device can be the first network device and the second network device shown in Figure 3, or can be the first network device and the second network device in the communication system shown in Figure 2. Wherein:

[0074] 301. The second network device sends a handover request message to the first network device. Correspondingly, the first network device receives a handover request message from the second network device. The handover request message indicates that the terminal device requests to switch from the second network device to the first network device. The handover request message also indicates a first sequence number, which is smaller than the second sequence number.

[0075] In the embodiment of the present application, the second network device is the source network device of the terminal device, that is, the network device that provides services to the terminal device before the handover, and the first network device is the target network device of the terminal device, that is, the network device that provides services to the terminal device after the handover. After the terminal device initiates the handover request, the second network device sends a handover request message to the first network device, indicating that the terminal device requests to be handed over from the second network device to the first network device.

[0076] While the terminal device is switching, the terminal device is transmitting MBS. MBS is a service for multiple terminal devices, which enables multiple terminal devices to receive the same message at the same time, such as live broadcast service, public safety service, batch software update service, etc. In order to ensure the MBS transmission of the terminal device, the switching request message also carries the multicast broadcast system radio bearer (MBS Radio Bearer, MRB) progress information, that is, the switching request message also indicates the first sequence number, where the first sequence number is the sequence number of the latest (the lastest) MBS data packet received by the second network device from the core network device. It can be understood that the core network device sends MBS data packets in order from small to large based on the sequence number of the MBS data packet, that is, the core network device will give priority to sending MBS data packets with small sequence numbers. The sequence number of the latest MBS data packet refers to the largest sequence number among the sequence numbers of the MBS data packets from the core network device cached by the second network device. For example, suppose that the second network device caches 4 MBS data packets from the core network, and the sequence numbers of the 4 MBS data packets are 1, 2, 3, and 4 respectively. The first sequence number refers to the sequence number of the latest MBS data packet among the 4 MBS data packets, that is, the largest sequence number among the sequence numbers of the 4 MBS data packets, and the first sequence number is 4.

[0077] The first network device will compare the size of the first sequence number with the size of the second sequence number to determine how fast the MBS progress of the first network device is relative to the MBS progress of the second network device. The second sequence number is the sequence number of the oldest MBS data packet received by the first network device from the core network device. It can be understood that the sequence number of the latest MBS data packet refers to the smallest sequence number among the sequence numbers of the MBS data packets from the core network device cached by the first network device. Assume that the first network device has cached 4 MBS data packets from the core network, and the sequence numbers of the 4 MBS data packets are 9, 10, 11, and 12 respectively. The second sequence number refers to the sequence number of the latest MBS data packet among the 4 MBS data packets, that is, the smallest sequence number among the sequence numbers of the 4 MBS data packets, and the second sequence number is 9.

[0078] The first sequence number is smaller than the second sequence number, indicating that the first network device is receiving MBS data packets from the core network device faster than the second network device. For example, suppose the second network device has cached four MBS data packets from the core network, with sequence numbers 1, 2, 3, and 4, respectively, and the first sequence number is 4. The first network device has cached four MBS data packets from the core network, with sequence numbers 9, 10, 11, and 12, respectively, and the second sequence number is 9. The core network device sends MBS data packets in ascending order based on the sequence number of the MBS data packets. The second sequence number 9 is larger than the first sequence number 4, indicating that the first network device is receiving MBS data packets from the core network device faster than the second network device.

[0079] 302. The first network device sends a handover response (handover request ACK) message to the second network device. Correspondingly, the second network device receives the handover response message from the first network device. The handover response message instructs the second network device not to forward the MBS data packet.

[0080] In an embodiment of the present application, the terminal device can maintain a communication connection with the second network device during the handover process and continue to receive data from the second network device. For example, the terminal device uses DAPS handover. Before the terminal device handover is completed, the first network device instructs the second network device not to forward MBS data packets through a handover response message. During the handover period, the terminal device will directly receive MBS data packets through the second network device and the first network device, and will not receive MBS data packets sent by the first network device and forwarded by the second network device. This can prevent the terminal device from receiving duplicate data packets through the first network device and the second network device, which is beneficial for saving resource overhead.

[0081] In one possible implementation, the handover response message includes first indication information, and the first indication information indicates that the MBS data packet is not forwarded. The first indication information may be a field or a bit in the handover response message. When the value of the first indication information is a first value, it indicates that the MBS data packet is not forwarded. When the value of the first indication information is a second value, it indicates that the MBS data packet is forwarded. The first value is 1 and the second value is 0, or the first value is 0 and the second value is 1, and this application is not limited to this. Optionally, the first network device sends the handover response message to the second network device, specifically, the first network device sends the handover response message to the second network device CU-CP, the handover response message includes the first indication information, the first indication information indicates that the MBS data packet is not forwarded, and the first network device CU-CP sends the first indication information to the CU-UP of the first network device. The CP is mainly responsible for transmitting control signaling, and the UP is mainly responsible for transmitting actual data. Based on this implementation method, before the terminal device switching is completed, the first network device instructs the second network device not to forward the MBS data packet through a switching response message, which can avoid the terminal device receiving duplicate data packets through the first network device and the second network device, which is conducive to saving resource overhead.

[0082] In a possible implementation, the switching response message includes user plane transport layer information of the first network device. The user plane transport layer information is the user plane address of the first network device, which can be used to send or receive data. The user plane transport layer information can be used to establish a forwarding tunnel between the first network device and the second network device. Optionally, the user plane transport layer information is downlink forwarding data plane transport layer information (DL Forwarding UP TNL Information). After the second network device receives the user plane transport layer information of the first network device, the second network device will establish a forwarding tunnel with the first network device, but because the switching response message indicates not to forward MBS data, the second network device will not forward MBS data packets to the first network device through the forwarding tunnel. The forwarding tunnel can be used for subsequent use when the terminal device loses the MBS data packet from the second network device. The second network device can directly forward the lost MBS data packet of the terminal device to the first network device through the forwarding tunnel.

[0083] In one possible implementation, a terminal device sends a first report to a first network device. Accordingly, the first network device receives the first report from the terminal device, the first report indicating MBS data packets lost by the terminal device. Based on the first report, the first network device determines that at least one of the MBS data packets lost by the terminal device has a sequence number less than a second sequence number. The first network device sends a handover success message to a second network device, the handover success message indicating a request to forward the MBS data packets lost by the terminal device. Accordingly, the second network device receives the handover success message from the first network device. The second network device sends one or more MBS data packets to the first network device. The first network device forwards the one or more MBS data packets to the terminal device.

[0084] Among them, the first report is used to indicate the status of the MBS data packets received by the terminal device. Optionally, the first report sent by the terminal device is a Packet Data Convergence Protocol (PDCP) status report. When the first network device determines through the first report that among the MBS data packets lost by the terminal device, there is at least one MBS data packet with a sequence number less than the second sequence number, the second sequence number refers to the sequence number of the latest MBS data packet received by the first network device from the core network device. The data packets with sequence numbers less than the second sequence number have been deleted by the first network device, so the first network device cannot provide the terminal device with MBS data packets with sequence numbers less than the second sequence number, and the second network device needs to forward this part of the MBS data packets through the forwarding tunnel. Based on this implementation method, the terminal device can receive the lost data packets, ensure the integrity of the data, and achieve lossless switching.

[0085] For example, as shown in FIG4 , it is assumed that the second network device sends MBS data packets with sequence numbers 1 to 8 to the terminal device, but the terminal device fails to successfully receive the data packets with sequence numbers 6 and 7. The terminal device sends a first report to the first network device indicating that the sequence numbers of the lost MBS data packets are 6 and 7. The first network device determines that the second sequence number is 9, which is greater than the sequence number of the MBS data packet lost by the terminal device. Therefore, the first network device sends a switching success message to the second network device, and the switching success message indicates a request to forward the MBS data packet lost by the terminal device. After receiving the switching success message, the second network device sends MBS data packets with sequence numbers 6 and 7 to the first network device. Correspondingly, the first network device forwards the MBS data packets with sequence numbers 6 and 7 to the terminal device.

[0086] Optionally, the handover success message indicates the sequence numbers of the MBS data packets lost by the terminal device, where the one or more MBS data packets are the MBS data packets lost by the terminal device. Further, optionally, the handover success message includes second indication information, where the second indication information indicates the sequence numbers of the MBS data packets lost by the terminal device. For example, the second indication information may be a field in the handover success message, where the field indicates the sequence numbers of the MBS data packets lost by the terminal device. The second indication information may include the sequence numbers of the MBS data packets partially or completely lost by the terminal device. For example, assuming that the sequence numbers of the MBS data packets lost by the terminal device are 6 and 7, the second indication information indicates sequence numbers 6 and 7. Alternatively, the second indication information may be a bitmap, where the bitmap includes i bits, and the value of the jth bit in the bitmap is a first value, indicating that the MBS data packet corresponding to the jth bit is lost, where i is a positive integer and j is a positive integer less than or equal to i. The first value may be 0 or 1. For example, assuming that the sequence numbers of the MBS data packets lost by the terminal device are 6 and 7, the bitmap includes 8 bits, the jth bit in the bitmap corresponds to the data packet with sequence number j, and if the first value is 1, the bitmap included in the handover success message sent by the first network device is 00000110, and the second network device can determine, based on the bitmap, that the sequence numbers of the MBS data packets lost by the terminal device are 6 and 7. Alternatively, if the first value is 0, the bitmap included in the handover success message sent by the first network device is 11111001, and the second network device can determine, based on the bitmap, that the sequence numbers of the MBS data packets lost by the terminal device are 6 and 7.

[0087] Optionally, the handover success message indicates a third sequence number, which is the smallest sequence number among the sequence numbers of the MBS data packets lost by the terminal device, and the sequence number of any one of the sequence numbers of the one or more MBS data packets is greater than or equal to the third sequence number. Further optionally, the handover success message includes second indication information, and the second indication information indicates the third sequence number. For example, the second indication information may be a field in the handover success message, and the field indicates the third sequence number. Exemplarily, assuming that the sequence numbers of the MBS data packets lost by the terminal device are 6 and 7, and the third sequence number indicated in the handover success message sent by the first network device is 6, the second network device sends MBS data packets with sequence numbers greater than or equal to 6 to the first network device through the forwarding tunnel, for example, MBS data packets with sequence numbers 6, 7, and 8.

[0088] In order to save resource overhead, an embodiment of the present application proposes a communication method, as shown in Figure 5, which includes steps 501 to 505. The execution entities corresponding to the method shown in Figure 5 are respectively the first network device, the second network device and the terminal device. Alternatively, the execution entity of the method shown in Figure 5 can be a chip in the first network device, a chip in the second network device and a chip in the terminal device. Figure 5 is illustrated using the first network device, the second network device and the terminal device as examples. The embodiment of the present application does not limit the execution entity of the communication method. The terminal device can be the first network device, the second network device and the terminal device shown in Figure 5, and can be the first network device, the second network device and the terminal device in the communication system shown in Figure 2. Wherein:

[0089] 501. The second network device sends a switching request message to the first network device. Correspondingly, the first network device receives a switching request message from the second network device. The switching request message indicates that the terminal device requests to switch from the second network device to the first network device. The switching request message also indicates a first sequence number, which is smaller than the second sequence number.

[0090] The specific implementation of step 501 is the same as that of step 301 , and reference may be made to the description of step 301 , which will not be repeated here.

[0091] 502. The first network device sends a switching response message to the second network device. Correspondingly, the second network device receives the switching response message from the first network device. The switching response message does not include user plane transport layer information. The user plane transport layer information is used to establish a forwarding tunnel between the first network device and the second network device.

[0092] In an embodiment of the present application, a terminal device can maintain a communication connection with the second network device during the handover process and continue to receive data from the second network device. For example, if the terminal device utilizes DAPS handover, the first network device does not send user plane transport layer information to the second network device before the terminal device handover is complete. The user plane transport layer information is the user plane address of the first network device and can be used to send or receive data. The user plane transport layer information can be used to establish a forwarding tunnel between the first network device and the second network device. Optionally, the user plane transport layer information is downlink forwarding data plane transport layer information. Because the second network device does not have the user plane transport layer information of the first network device, it cannot establish a forwarding tunnel with the first network device. Consequently, during the terminal device handover, the second network device will not forward MBS data packets to the first network device. During the handover, the terminal device will directly receive MBS data packets through the second network device and the first network device, and will not receive MBS data packets sent by the first network device and forwarded by the second network device. Therefore, based on this implementation, the terminal device can avoid receiving duplicate data packets through the first and second network devices, which helps save resource overhead.

[0093] 503. The terminal device sends a first report to the first network device. Correspondingly, the first network device receives the first report from the terminal device, where the first report indicates the MBS data packets lost by the terminal device.

[0094] 504. The first network device determines, based on the first report, that among the MBS data packets lost by the terminal device, there is at least one MBS data packet whose sequence number is smaller than the second sequence number.

[0095] Among them, the first report is used to indicate the status of the MBS data packets received by the terminal device. Optionally, the first report sent by the terminal device is a Packet Data Convergence Protocol (PDCP) status report. When the first network device determines through the first report that among the MBS data packets lost by the terminal device, there is at least one MBS data packet with a sequence number less than the second sequence number, the second sequence number refers to the sequence number of the latest MBS data packet received by the first network device from the core network device. The data packets with sequence numbers less than the second sequence number have been deleted by the first network device, so the first network device cannot provide the terminal device with MBS data packets with sequence numbers less than the second sequence number, and the second network device needs to forward this part of the MBS data packets through the forwarding tunnel.

[0096] 505. The first network device sends a switching success message to the second network device. Correspondingly, the second network device receives the switching success message from the first network device. The switching success message indicates a request to forward the MBS data packet lost by the terminal device. The switching success message includes user plane transport layer information.

[0097] In an embodiment of the present application, since the switching success message includes user plane transport layer information, the second network device can establish a forwarding tunnel with the first network device. The second network device sends one or more MBS data packets to the first network device through the forwarding tunnel. After the first network device receives the one or more MBS data packets, it forwards the one or more data packets to the terminal device. Therefore, based on this method, the terminal device can receive lost data packets, ensure data integrity, and achieve lossless switching.

[0098] Optionally, the handover success message indicates the sequence numbers of the MBS data packets lost by the terminal device, where the one or more MBS data packets are the MBS data packets lost by the terminal device. Further, optionally, the handover success message includes second indication information, where the second indication information indicates the sequence numbers of the MBS data packets lost by the terminal device. For example, the second indication information may be a field in the handover success message, where the field indicates the sequence numbers of the MBS data packets lost by the terminal device. The second indication information may include the sequence numbers of the MBS data packets partially or completely lost by the terminal device. For example, assuming that the sequence numbers of the MBS data packets lost by the terminal device are 6 and 7, the second indication information indicates sequence numbers 6 and 7. Alternatively, the second indication information may be a bitmap, where the bitmap includes i bits, and the value of the jth bit in the bitmap is a first value, indicating that the MBS data packet corresponding to the jth bit is lost. The first value may be 0 or 1, where i is a positive integer and j is a positive integer less than or equal to i. For example, assuming that the sequence numbers of the MBS data packets lost by the terminal device are 6 and 7, the bitmap includes 8 bits, the j-th bit in the bitmap corresponds to the data packet with sequence number j, the first value is 1, and the bitmap included in the switching success message sent by the first network device is 00000110. The second network device can determine that the sequence numbers of the MBS data packets lost by the terminal device are 6 and 7 based on the bitmap.

[0099] In one possible implementation, the handover success message indicates a third sequence number, which is the smallest sequence number among the sequence numbers of the MBS data packets lost by the terminal device, and the sequence number of any one of the sequence numbers of the one or more MBS data packets is greater than or equal to the third sequence number. Further optionally, the handover success message includes second indication information, and the second indication information indicates the third sequence number. For example, the second indication information may be a field in the handover success message, and the field indicates the third sequence number. Exemplarily, assuming that the sequence numbers of the MBS data packets lost by the terminal device are 6 and 7, and the third sequence number indicated in the handover success message sent by the first network device is 6, the second network device sends MBS data packets with sequence numbers greater than or equal to 6, for example, MBS data packets with sequence numbers 6, 7, and 8, to the first network device through the forwarding tunnel.

[0100] To implement the various functions of the methods provided in the embodiments of the present application, the first network device and the second network device may each include hardware structures and / or software modules, and implement the aforementioned functions in the form of hardware structures, software modules, or a combination of hardware structures and software modules. Whether a particular one of the aforementioned functions is implemented in the form of hardware structures, software modules, or a combination of hardware structures and software modules depends on the specific application and design constraints of the technical solution.

[0101] Please refer to Figure 6, which shows a schematic diagram of the structure of a communication device according to an embodiment of the present application. The communication device can be a first network device or a second network device. In one possible implementation, the communication device can include a module or unit corresponding to the method / operation / step / action performed by the first network device or the second network device in the method embodiment shown in Figure 3 or Figure 5 above. The unit can be a hardware circuit, software, or a combination of hardware circuit and software.

[0102] The communication device shown in Figure 6 may include a processing unit 601 and a communication unit 602. The processing unit 601 is configured to process data. The communication unit 602 integrates a receiving unit and a transmitting unit. The communication unit 602 may also be referred to as a transceiver unit. Alternatively, the communication unit 602 may be split into a receiving unit and a transmitting unit.

[0103] The communication device shown in Figure 6 may be a first network device, or a device that can be used in conjunction with the first network device.

[0104] When the communication device is used to execute part or all of the functions of the first network device in the method embodiment described in Figure 3 above, the communication unit 602 is used to receive a switching request message from the second network device, where the switching request message indicates that the terminal device requests to switch from the second network device to the first network device, and the switching request message also indicates a first sequence number, which is the sequence number of the latest multicast broadcast service MBS data packet received by the second network device from the core network device. The first sequence number is smaller than the second sequence number, and the second sequence number is the sequence number of the latest MBS data packet received by the first network device from the core network device; the communication unit 602 is also used to send a switching response message to the second network device, where the switching response message indicates that the second network device does not forward the MBS data packet.

[0105] In a possible implementation, the handover response message includes user plane transport layer information of the first network device, where the user plane transport layer information is used to establish a forwarding tunnel with the second network device.

[0106] In a possible implementation manner, the handover response message includes first indication information, where the first indication information indicates not to forward the MBS data packet.

[0107] In a possible implementation, the communication unit 602 is further configured to receive a first report from the terminal device, where the first report indicates MBS data packets lost by the terminal device.

[0108] In one possible implementation, the processing unit 601 is used to determine, based on the first report, that among the MBS data packets lost by the terminal device, there is at least one MBS data packet whose sequence number is smaller than the second sequence number; the communication unit 602 is also used to send a switching success message to the second network device, where the switching success message indicates a request to forward the MBS data packets lost by the terminal device.

[0109] In a possible implementation, the switching success message includes second indication information, where the second indication information indicates a request to forward the MBS data packets lost by the terminal device.

[0110] In a possible implementation, the communication unit 602 is further configured to receive one or more MBS data packets from the second network device; and send one or more MBS data packets to the terminal device.

[0111] In a possible implementation, the switching success message indicates the sequence number of the MBS data packet lost by the terminal device, and the one or more MBS data packets are the MBS data packets lost by the terminal device.

[0112] In one possible implementation, the switching success message indicates a third sequence number, which is the smallest sequence number among the sequence numbers of the MBS data packets lost by the terminal device, and the sequence number of any one of the sequence numbers of one or more MBS data packets is greater than or equal to the third sequence number.

[0113] When the communication device is used to execute part or all of the functions of the first network device in the method embodiment described in FIG5 , the communication unit 602 is used to receive a switching request message from the second network device, the switching request message indicating that the terminal device requests to switch from the second network device to the first network device, and the switching request message also indicates a first sequence number, the first sequence number being the sequence number of the latest multicast broadcast service MBS data packet received by the second network device from the core network device, the first sequence number being less than the second sequence number, and the second sequence number being the sequence number of the latest MBS data packet received by the first network device from the core network device; the communication unit 602 is further used to send a switching request message to the second network device. response message, the switching response message does not include user plane transport layer information, the user plane transport layer information is used to establish a forwarding tunnel between the first network device and the second network device; the communication unit 602 is also used to receive a first report from the terminal device, the first report indicates the data packet lost by the terminal device; the processing unit 601 is used to determine based on the first report that there is at least one MBS data packet whose sequence number is less than the second sequence number among the MBS data packets lost by the terminal device; the communication unit 602 is also used to send a switching success message to the second network device, the switching success message indicates a request to forward the MBS data packet lost by the terminal device, and the switching success message includes user plane transport layer information.

[0114] In a possible implementation, the switching success message includes second indication information, where the second indication information indicates a request to forward the MBS data packets lost by the terminal device.

[0115] In a possible implementation, the communication unit 602 is further configured to: receive one or more MBS data packets from the second network device; and send one or more MBS data packets to the terminal device.

[0116] In a possible implementation, the switching success message indicates the sequence number of the MBS data packet lost by the terminal device, and the one or more MBS data packets are the MBS data packets lost by the terminal device.

[0117] In a possible implementation, the third sequence number is the smallest sequence number among the sequence numbers of the MBS data packets lost by the terminal device, and the sequence number of any one of the sequence numbers of the one or more MBS data packets is greater than or equal to the third sequence number.

[0118] The communication device shown in Figure 6 may be a second network device, or a device that can be used in conjunction with the second network device.

[0119] When the communication device is used to execute part or all of the functions of the second network device in the method embodiment described in Figure 3 above, the communication unit 602 is used to send a switching request message to the first network device, where the switching request indicates that the terminal device requests to switch from the second network device to the first network device, and the switching request message also indicates a first sequence number, which is the sequence number of the latest multicast broadcast service MBS data packet received by the second network device from the core network device at the first time point, and the first sequence number is smaller than the second sequence number, which is the sequence number of the latest MBS data packet received by the first network device from the core network device at the first time; the communication unit 602 is also used to receive a switching response message from the second network device, and the switching response message indicates that the MBS data packet is not forwarded.

[0120] In a possible implementation, the handover response message includes user plane transport layer information of the first network device, where the user plane transport layer information is used to establish a forwarding tunnel between the first network device and the second network device.

[0121] In a possible implementation manner, the handover response message includes first indication information, where the first indication information indicates not to forward the MBS data packet.

[0122] In a possible implementation, the communication unit 602 is further configured to: receive a handover success message from the first network device, the handover success message indicating a request to forward MBS data packets lost by the terminal device; and send one or more MBS data packets to the first network device.

[0123] In a possible implementation, the switching success message includes second indication information, where the second indication information indicates a request to forward the MBS data packets lost by the terminal device.

[0124] In a possible implementation, the switching success message indicates the sequence number of the MBS data packet lost by the terminal device, and the one or more MBS data packets are the MBS data packets lost by the terminal device.

[0125] In one possible implementation, the switching success message indicates a third sequence number, which is the smallest sequence number among the sequence numbers of the MBS data packets lost by the terminal device, and the sequence number of any one of the sequence numbers of one or more MBS data packets is greater than or equal to the third sequence number.

[0126] When the communication device is used to execute part or all of the functions of the second network device in the method embodiment described in Figure 5 above, the communication unit 602 is used to send a switching request message to the first network device, where the switching request message indicates that the terminal device requests to switch from the second network device to the first network device, and the switching request message also indicates a first sequence number, where the first sequence number is the sequence number of the latest multicast broadcast service MBS data packet received by the second network device from the core network device, the first sequence number is smaller than the second sequence number, and the second sequence number is the sequence number of the latest MBS data packet received by the first network device from the core network device; the communication unit 602 is also used to receive a switching response message from the first network device, where the switching response message does not include user plane transport layer information, where the user plane transport layer information is used to establish a forwarding tunnel between the first network device and the second network device; the communication unit 602 is also used to receive a switching success message from the first network device, where the switching success message indicates a request to forward the MBS data packet lost by the terminal device, and the switching success message includes user plane transport layer information.

[0127] In a possible implementation, the switching success message includes second indication information, where the second indication information indicates a request to forward the MBS data packets lost by the terminal device.

[0128] In a possible implementation, the communication unit 602 is further configured to send one or more MBS data packets to the first network device.

[0129] In one possible implementation, the switching success message indicates a third sequence number, which is the smallest sequence number among the sequence numbers of the MBS data packets lost by the terminal device, and the sequence number of any one of the sequence numbers of one or more MBS data packets is greater than or equal to the third sequence number.

[0130] Figure 7 shows a schematic diagram of the structure of another communication device. The communication device 700 can be the first network device in the above method embodiment, or can be a chip, chip system, or processor that supports the first network device to implement the above method. This communication device can be used to implement the method described in the above method embodiment. For details, please refer to the description of the above method embodiment.

[0131] Alternatively, the communication device 700 may be the second network device in the above method embodiment, or may be a chip, chip system, or processor that supports the second network device to implement the above method. The communication device may be used to implement the method described in the above method embodiment, and details may be found in the description of the above method embodiment.

[0132] The communication device 700 may include one or more processors 701. The processor 701 may be a general-purpose processor or a dedicated processor. For example, it may be a baseband processor or a central processing unit (CPU). The baseband processor may be used to process communication protocols and communication data, while the CPU may be used to control a communication device (e.g., a base station, a baseband chip, a terminal, a terminal chip, a DU or a CU), execute software programs, and process data in the software programs.

[0133] Optionally, the communication device 700 may include one or more memories 702, on which instructions 704 may be stored. The instructions may be executed on the processor 701, causing the communication device 700 to perform the method described in the above method embodiment. Optionally, the memory 702 may also store data. The processor 701 and memory 702 may be provided separately or integrated together.

[0134] Optionally, the communication device 700 may further include a transceiver 705 and an antenna 706. The transceiver 705 may be referred to as a transceiver unit, a transceiver, or a transceiver circuit, etc., and is configured to implement transceiver functions. The transceiver 705 may include a receiver and a transmitter. The receiver may be referred to as a receiver or a receiving circuit, etc., and is configured to implement a receiving function; the transmitter may be referred to as a transmitter or a transmitting circuit, etc., and is configured to implement a transmitting function.

[0135] The communication device 700 is a first network device: the processor 701 is used to execute the data processing operation of the first network device in the above method embodiment. The transceiver 705 is used to execute the data receiving and sending operation of the first network device in the above method embodiment.

[0136] Alternatively, the communication device 700 is a second network device: the processor 701 is used to execute the data processing operation of the second network device in the above method embodiment. The transceiver 705 is used to execute the data transceiver operation of the second network device in the above method embodiment.

[0137] In another possible design, processor 701 may include a transceiver for implementing receiving and transmitting functions. For example, the transceiver may be a transceiver circuit, an interface, or an interface circuit. The transceiver circuit, interface, or interface circuit for implementing the receiving and transmitting functions may be separate or integrated. The transceiver circuit, interface, or interface circuit may be used for reading and writing code / data, or the transceiver circuit, interface, or interface circuit may be used for transmitting or delivering signals.

[0138] In another possible design, the processor 701 may optionally store an instruction 703. The instruction 703 runs on the processor 701, which can cause the communication device 700 to perform the method described in the above method embodiment. The instruction 703 may be fixed in the processor 701. In this case, the processor 701 may be implemented by hardware.

[0139] In another possible design, the communication device 700 may include a circuit that can implement the functions of sending, receiving, or communicating in the aforementioned method embodiments. The processor and transceiver described in the embodiments of the present application can be implemented on an integrated circuit (IC), an analog IC, a radio frequency integrated circuit (RFIC), a mixed signal IC, an application specific integrated circuit (ASIC), a printed circuit board (PCB), an electronic device, etc.

[0140] The communication device described in the above embodiment may be a first network device or a second network device, but the scope of the communication device described in the embodiment of the present application is not limited thereto, and the structure of the communication device may not be limited to FIG7 . The communication device may be an independent device or may be part of a larger device. For example, the communication device may be:

[0141] (1) An independent integrated circuit (IC), or chip, or chip system or subsystem;

[0142] (2) A set of one or more ICs, optionally including a storage component for storing data and instructions;

[0143] (3) ASIC, such as modem (Mobile Station Modem, MSM);

[0144] (4) Modules that can be embedded in other devices;

[0145] (5) Receivers, terminals, smart terminals, cellular phones, wireless devices, handheld devices, mobile units, vehicle-mounted devices, first and second network devices, cloud devices, artificial intelligence devices, etc.;

[0146] (6)Others, etc.

[0147] In the case where the communication device can be a chip or a chip system, please refer to the chip structure diagram shown in Figure 8. The chip shown in Figure 8 includes a processor 801 and an interface 802. Optionally, it may also include a memory 803. The number of processors 801 can be one or more, and the number of interfaces 802 can be multiple.

[0148] In one design, for a case where the chip is used to implement the function of the first network device in the embodiment of the present application:

[0149] The interface 802 is used to input or output signals;

[0150] The processor 801 is configured to execute the data processing operation of the first network device in the above method embodiment.

[0151] In another design, for the case where the chip is used to implement the function of the second network device in the embodiment of the present application:

[0152] The interface 802 is used to input or output signals;

[0153] The processor 801 is configured to execute the data processing operation of the second network device in the above method embodiment.

[0154] It is understandable that some optional features in the embodiments of the present application may, in certain scenarios, be implemented independently of other features, such as the solution on which they are currently based, to solve corresponding technical problems and achieve corresponding effects. They may also be combined with other features in certain scenarios as needed. Accordingly, the communication device provided in the embodiments of the present application may also implement these features or functions accordingly, which will not be described in detail here.

[0155] It should be understood that the processor in the embodiment of the present application can be an integrated circuit chip with signal processing capabilities. During implementation, each step of the above method embodiment can be completed by an integrated logic circuit of hardware in the processor or instructions in the form of software. The above processor can be a general-purpose processor, a digital signal processor (DSP), an ASIC, a field programmable gate array (FPGA) or other programmable logic device, a discrete gate or transistor logic device, or a discrete hardware component.

[0156] It is understood that the memory in the embodiments of the present application may be a volatile memory or a non-volatile memory, or may include both volatile and non-volatile memories. Among them, the non-volatile memory may be a read-only memory (ROM), a programmable read-only memory (PROM), an erasable programmable read-only memory (EPROM), an electrically erasable programmable read-only memory (EEPROM), or a flash memory. The volatile memory may be a random access memory (RAM), which is used as an external cache. By way of example and not limitation, many forms of RAM are available, such as static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), double data rate SDRAM (DDR SDRAM), enhanced SDRAM (ESDRAM), synchronous link DRAM (SLDRAM), and direct RAM bus RAM (DR RAM). It should be noted that the memory of the systems and methods described herein is intended to include, but is not limited to, these and any other suitable types of memory.

[0157] The present application also provides a computer-readable medium for storing computer software instructions, which, when executed by a communication device, implement the functions of any of the above method embodiments.

[0158] The present application also provides a computer program product for storing computer software instructions, which, when executed by a communication device, implements the functions of any of the above method embodiments.

[0159] In the above embodiments, all or part of the embodiments may be implemented by software, hardware, firmware, or any combination thereof. When implemented using software, all or part of the embodiments may be implemented in the form of a computer program product. The computer program product includes one or more computer instructions. When the computer instructions are loaded and executed on a computer, all or part of the processes or functions described in the embodiments of the present application are generated. The computer may be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions may be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another computer-readable storage medium. For example, the computer instructions may be transmitted from one website, computer, server, or data center to another website, computer, server, or data center via a wired (e.g., coaxial cable, optical fiber, digital subscriber line (DSL)) or wireless (e.g., infrared, wireless, microwave, etc.) method. The computer-readable storage medium may be any available medium that a computer can access or a data storage device such as a server or data center that includes one or more available media integrated therein. The available medium may be a magnetic medium (eg, a floppy disk, a hard disk, a magnetic tape), an optical medium (eg, a high-density digital video disc (DVD)), or a semiconductor medium (eg, a solid state drive (SSD)).

[0160] In the above embodiments, the description of each embodiment has its own focus. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

Claims

1. A communication method, characterized in that: Applied to a first network device, the method comprises: receiving a handover request message from a second network device, the handover request message indicating that the terminal device requests to be handed over from the second network device to the first network device, the handover request message further indicating a first sequence number, the first sequence number being the sequence number of the latest multicast broadcast service MBS data packet received by the second network device from the core network device, the first sequence number being less than a second sequence number, the second sequence number being the sequence number of the latest MBS data packet received by the first network device from the core network device; A switching response message is sent to the second network device, where the switching response message indicates that the second network device does not forward the MBS data packet.

2. The method according to claim 1, characterized in that The switching response message includes user plane transport layer information of the first network device, and the user plane transport layer information is used to establish a forwarding tunnel with the second network device.

3. The method according to claim 1 or 2, characterized in that: The switching response message includes first indication information, where the first indication information indicates not to forward the MBS data packet.

4. The method according to any one of claims 1 to 3, characterized in that: The method further comprises: A first report is received from the terminal device, the first report indicating MBS data packets lost by the terminal device.

5. The method according to claim 4, characterized in that The method further comprises: Determine based on the first report that at least one MBS data packet among the MBS data packets lost by the terminal device has a sequence number smaller than the second sequence number; A switching success message is sent to the second network device, where the switching success message indicates a request to forward the MBS data packet lost by the terminal device.

6. The method according to claim 5, characterized in that The switching success message includes second indication information, where the second indication information indicates a request to forward the MBS data packet lost by the terminal device.

7. The method according to claim 5 or 6, characterized in that: The method further comprises: receiving one or more MBS data packets from the second network device; The one or more MBS data packets are sent to the terminal device.

8. The method according to claim 7, characterized in that The switching success message indicates the sequence number of the MBS data packet lost by the terminal device, and the one or more MBS data packets are the MBS data packets lost by the terminal device.

9. The method according to claim 7, characterized in that: The switching success message indicates a third sequence number, where the third sequence number is the smallest sequence number among the sequence numbers of the MBS data packets lost by the terminal device, and the sequence number of any one of the one or more MBS data packets is greater than or equal to the third sequence number.

10. A communication method, characterized in that: Applied to the second network device, the method comprises: Sending a switching request message to the first network device, the switching request indicating that the terminal device requests to switch from the second network device to the first network device, the switching request message further indicating a first sequence number, the first sequence number being the sequence number of the latest multicast broadcast service MBS data packet received by the second network device from the core network device at the first time point, the first sequence number being less than the second sequence number, the second sequence number being the sequence number of the latest MBS data packet received by the first network device from the core network device at the first time point; A switching response message is received from the second network device, where the switching response message indicates not to forward the MBS data packet.

11. The method according to claim 10, characterized in that The handover response message includes user plane transport layer information of the first network device, and the user plane transport layer information is used to establish a forwarding tunnel between the first network device and the second network device.

12. The method according to claim 10 or 11, characterized in that: The switching response message includes first indication information, where the first indication information indicates not to forward the MBS data packet.

13. The method according to any one of claims 10 to 12, characterized in that: The method further comprises: receiving a switching success message from the first network device, wherein the switching success message indicates a request to forward the MBS data packet lost by the terminal device; Send one or more MBS data packets to the first network device.

14. The method according to claim 13, characterized in that The switching success message includes second indication information, where the second indication information indicates a request to forward the MBS data packet lost by the terminal device.

15. The method according to claim 14, characterized in that The switching success message indicates the sequence number of the MBS data packet lost by the terminal device, and the one or more MBS data packets are the MBS data packets lost by the terminal device.

16. The method according to claim 14, characterized in that The switching success message indicates a third sequence number, where the third sequence number is the smallest sequence number among the sequence numbers of the MBS data packets lost by the terminal device, and the sequence number of any one of the one or more MBS data packets is greater than or equal to the third sequence number.

17. A communication method, characterized in that: Applied to a first network device, the method comprises: receiving a handover request message from a second network device, the handover request message indicating that the terminal device requests to be handed over from the second network device to the first network device, the handover request message further indicating a first sequence number, the first sequence number being the sequence number of the latest multicast broadcast service MBS data packet received by the second network device from the core network device, the first sequence number being less than a second sequence number, the second sequence number being the sequence number of the latest MBS data packet received by the first network device from the core network device; Sending a handover response message to the second network device, wherein the handover response message does not include user plane transport layer information, and the user plane transport layer information is used to establish a forwarding tunnel between the first network device and the second network device; receiving a first report from a terminal device, the first report indicating data packets lost by the terminal device; Determine based on the first report that at least one MBS data packet among the MBS data packets lost by the terminal device has a sequence number smaller than the second sequence number; A switching success message is sent to the second network device, where the switching success message indicates a request to forward the MBS data packet lost by the terminal device, and the switching success message includes user plane transport layer information.

18. The method according to claim 17, characterized in that The switching success message includes second indication information, where the second indication information indicates a request to forward the MBS data packet lost by the terminal device.

19. The method according to claim 17 or 18, characterized in that The method further comprises: receiving one or more MBS data packets from the second network device; The one or more MBS data packets are sent to the terminal device.

20. The method according to claim 19, characterized in that The switching success message indicates the sequence number of the MBS data packet lost by the terminal device, and the one or more MBS data packets are the MBS data packets lost by the terminal device.

21. The method according to claim 19, characterized in that The switching success message indicates a third sequence number, where the third sequence number is the smallest sequence number among the sequence numbers of the MBS data packets lost by the terminal device, and the sequence number of any one of the one or more MBS data packets is greater than or equal to the third sequence number.

22. A communication method, characterized in that: Applied to the second network device, the method comprises: Send a switching request message to the first network device, the switching request message indicating that the terminal device requests to switch from the second network device to the first network device, the switching request message also indicating a first sequence number, the first sequence number is the latest multicast broadcast service MBS data packet sequence number received by the second network device from the core network device, the first sequence number is less than the second sequence number, and the second sequence number is the The sequence number of the latest MBS data packet received by the first network device from the core network device; receiving a handover response message from the first network device, wherein the handover response message does not include user plane transport layer information, and the user plane transport layer information is used to establish a forwarding tunnel between the first network device and the second network device; A switching success message is received from the first network device, where the switching success message indicates a request to forward the MBS data packet lost by the terminal device, and the switching success message includes user plane transport layer information.

23. The method according to claim 22, characterized in that The switching success message includes second indication information, where the second indication information indicates a request to forward the MBS data packet lost by the terminal device.

24. The method according to claim 22 or 23, characterized in that The method further comprises: Send one or more MBS data packets to the first network device.

25. The method according to claim 24, characterized in that The switching success message indicates the sequence number of the MBS data packet lost by the terminal device, and the one or more MBS data packets are the MBS data packets lost by the terminal device.

26. The method according to claim 25, characterized in that The switching success message indicates a third sequence number, where the third sequence number is the smallest sequence number among the sequence numbers of the MBS data packets lost by the terminal device, and the sequence number of any one of the one or more MBS data packets is greater than or equal to the third sequence number.

27. A communication system, characterized in that: The communication system comprises a first network device and a second network device: The first network device is configured to send a switching request message to the second network device, wherein the switching request message indicates that the terminal device requests to switch from the second network device to the first network device, and the switching request message further indicates a first sequence number, wherein the first sequence number is a sequence number of a latest multicast broadcast service MBS data packet received by the second network device from a core network device, the first sequence number is smaller than a second sequence number, and the second sequence number is a sequence number of a latest MBS data packet received by the first network device from the core network device; The second network device is used to send a switching response message to the first network device, where the switching response message indicates that the second network device does not forward the MBS data packet.

28. A communication system, characterized in that: The communication system includes a first network device, a second network device and a terminal device: The first network device is configured to receive a switching request message from the second network device, the switching request message indicating that the terminal device requests to switch from the second network device to the first network device, the switching request message further indicating a first sequence number, the first sequence number being a sequence number of a latest multicast broadcast service MBS data packet received by the second network device from a core network device, the first sequence number being smaller than a second sequence number, and the second sequence number being a sequence number of a latest MBS data packet received by the first network device from the core network device; The second network device is used to send a handover response message to the first network device, wherein the handover response message does not include user plane transport layer information, and the user plane transport layer information is used to establish a forwarding tunnel between the first network device and the second network device; The terminal device is used to send a first report to the first network device; The first network device is further configured to determine, based on the first report, that among the MBS data packets lost by the terminal device, at least one MBS data packet has a sequence number that is smaller than the second sequence number; The first network device is further used to send a switching success message to the second network device, where the switching success message indicates a request to forward the MBS data packet lost by the terminal device, and the switching success message includes user plane transport layer information.

29. A communication device, characterized in that: The communication device includes a module or unit for executing the method of any one of claims 1 to 9, or the communication device includes a module or unit for executing the method of any one of claims 10 to 16, or the communication device includes a module or unit for executing the method of any one of claims 17 to 21, or the communication device includes a module or unit for executing the method of any one of claims 22 to 26.

30. A communication device, characterized in that: The method comprises a processor coupled to a memory, wherein the processor is used to execute a computer program or instruction stored in the memory to implement the method according to any one of claims 1 to 9, or to implement the method according to any one of claims 10 to 16, or to implement the method according to any one of claims 17 to 21, or to implement the method according to any one of claims 22 to 26.

31. The device according to claim 30, characterized in that The device further includes the memory and / or a transceiver, wherein the transceiver is used for transmitting and receiving data and / or signaling.

32. A communication device, characterized in that: The invention comprises a processor and an interface circuit, wherein the interface circuit is used to receive signals from other communication devices other than the communication device and transmit the signals to the processor or send the signals from the processor to other communication devices other than the communication device, wherein the processor executes the method according to any one of claims 1 to 9 through a logic circuit or an execution instruction, or the processor executes the method according to any one of claims 10 to 16 through a logic circuit or an execution instruction, or the processor executes the method according to any one of claims 17 to 21 through a logic circuit or an execution instruction, or the processor executes the method according to any one of claims 22 to 26 through a logic circuit or an execution instruction.

33. A computer-readable storage medium, characterized in that: The storage medium stores a computer program or instruction. When the computer program or instruction is executed by the communication device, the method according to any one of claims 1 to 9 is executed, or the method according to any one of claims 10 to 16 is executed, or the method according to any one of claims 17 to 21 is executed, or the method according to any one of claims 22 to 26 is executed.

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