Communication method, access network device, terminal device, and core network device

Abstract

To provide a communication method, an access network device, a terminal device, and a core network device that ensure a multicast service reception continuity of the terminal device in a handover process and avoid a packet loss or a redundant transmission.SOLUTION: In a communication system, a terminal device can know, in a handover process, a first service progress of a first access network device based on the first sequence number of a data packet forwarded by the first access network device. A method includes: a step of receiving, by the first access network device, first indication information indicating a first data packet and a sequence of the first data packet from a core network device; a step of determining a first sequence number of a first protocol layer of the first data packet based on the first indication information; and a step of transmitting the first data packet to the terminal device.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] This application claims priority to Chinese Patent Application No. 202010203782.4, entitled "COMMUNICATION METHOD, ACCESS NETWORK DEVICE, TERMINAL DEVICE, AND CORE NETWORK DEVICE," filed with the State Intellectual Property Office of the People's Republic of China on March 20, 2020, which is incorporated herein by reference in its entirety.

[0002] The present application relates to the field of communications, and more particularly to a communication method, an access network device, a terminal device, and a core network device. [Background technology]

[0003] A Multimedia Broadcast Multicast Service (MBMS) is a service addressed to multiple terminal devices. For example, live broadcast services and some public safety services are both MBMS services. In current communication systems, an access network device can transmit an MBMS service to a terminal device in unicast transmission mode by establishing a dedicated bearer with a single terminal device, or in multicast (groupcast) transmission mode by establishing a common bearer with multiple terminal devices. Regardless of the unicast or multicast transmission mode, different access network devices separately determine the sequence numbers of MBMS service data packets when transmitting them to terminal devices within their coverage.

[0004] When moving from a source access network device to a target access network device, in order to continue receiving the MBMS service, after being handed over to the target access network device, the terminal device must continue receiving the MBMS service originally received from the source access network device. However, the progress of the MBMS services transmitted by the two access network devices may be inconsistent. Because the source access network device and the target access network device are independent of each other when determining the sequence numbers of the data packets of the MBMS service, the source access network device and the target access network device may have inconsistent understandings of the sequence numbers of the data packets of the MBMS service during the terminal device handover process. As a result, when a handover occurs, the terminal device's reception of the MBMS service may be interrupted or the terminal device may receive redundant data packets. Therefore, the continuity of the MBMS service cannot be guaranteed. Summary of the Invention [Means for solving the problem]

[0005] The present application provides a communication method, an access network device, a terminal device, and a core network device, according to which the prior art case in which a terminal device receiving an MBMS service receives redundant data packets or service data is interrupted during handover between access network devices because the multicast service progress of different access network devices is inconsistent.

[0006] According to a first aspect, there is provided a communication method, the method being applied to a first access network device, the method comprising: The method includes receiving a first data packet and first indication information from a core network device, the first indication information indicating a sequence of the first data packet in at least one data packet; determining a first sequence number of a first protocol layer of the first data packet based on the first indication information; and transmitting the first data packet to a terminal device.

[0007] Therefore, in the process of a terminal device being handed over from a first access network device to a second access network device, the second access network device can know the first service progress of the first access network device based on the sequence number of the data packet forwarded by the first access network device without introducing additional progress exchange information between the two access network devices.

[0008] Referring to the first aspect, in some implementation forms of the first aspect, the first indication information includes at least one of the following information: a General Packet Radio Service Tunneling Protocol-User Plane GTP-U sequence number and a first service sequence number, the first service sequence number is set by a core network device or a data server, the first data packet is a data packet of the first service, and the at least one data packet is a data packet of the first service.

[0009] Referring to the first aspect, in some implementations of the first aspect, the first protocol layer includes at least one of a Service Data Adaptation Protocol (SDAP) layer, a Packet Data Convergence Protocol (PDCP) layer, and a Radio Link Control (RLC) layer.

[0010] Referring to the first aspect, in some implementations of the first aspect, the method further includes setting a starting sequence number of the first protocol layer of the first data packet based on the first indication information when any one of establishment of the first protocol entity, re-establishment of the first protocol entity, and recovery of the first protocol entity occurs.

[0011] Therefore, when any one of the establishment of the first protocol entity, the re-establishment of the first protocol entity, and the recovery of the first protocol entity occurs, the first access network device sets a starting sequence number of the first protocol layer of the first data packet based on the first instruction information to ensure continuity of the data packet of the first service and avoid sequence discontinuity caused by setting the starting sequence number of the first protocol layer of the data packet of the first service.

[0012] Referring to the first aspect, in some implementation forms of the first aspect, the method further includes a step of sending second instruction information to the terminal device, wherein the second instruction information indicates a sequence number of a first data packet belonging to the first service to be sent by the first access network device to the terminal device after the first protocol entity is established, after the first protocol entity is re-established, or after the first protocol entity is recovered.

[0013] Therefore, the terminal device can determine the starting sequence number of the first protocol layer of the first received data packet based on the second indication information, thereby avoiding data packet loss caused by inconsistent determination of the first data packet by the first terminal device and the first access network device.

[0014] Referring to the first aspect, in some implementation forms of the first aspect, the method further includes receiving third instruction information from the second access network device, where the third instruction information instructs the first access network device to stop forwarding data packets to the second access network device; and stopping forwarding data packets to the second access network device based on the third instruction information.

[0015] Therefore, in the handover process of the first terminal device, the second access network device determines whether the data forwarding of the first access network device can be stopped, and sends data forwarding stop instruction information to the first access network device, so that the continuity of multicast service reception of the terminal device in the handover process is guaranteed, and packet loss or redundant transmission is avoided.

[0016] Referring to the first aspect, in some implementation forms of the first aspect, the method further includes: receiving fourth instruction information sent by the second access network device, wherein the fourth instruction information indicates a sequence number of a first data packet forwarded by the first access network device to the second access network device; and forwarding the data packet to the second access network device based on the fourth instruction information.

[0017] The fourth indication information indicates the sequence number of the first protocol layer of the first data packet not received by the first terminal device, i.e., the starting data packet in the data forwarding performed by the first access network device. In this way, it is possible to prevent the first terminal device from receiving redundant data packets. Specifically, it is possible to avoid the following case: A data packet sent by the first access network device is successfully received by the first terminal device, but is still forwarded by the first access network device to the second access network device, and then transmitted by the second access network device to the first terminal device.

[0018]

[0013] Referring to the first aspect, in some implementation forms of the first aspect, the method further includes receiving fifth instruction information sent by the second access network device, where the fifth instruction information includes a second sequence number N, and the second sequence number indicates a sequence number of a first data packet of the first service to be sent by the second access network device to the terminal device after handover of the terminal device is completed. If the sequence number of the protocol layer corresponding to the data packet successfully sent by the first access network device to the terminal device is N-1, the first access network device stops sending data packets to the terminal device.

[0019] Therefore, in the handover process, the first access network device determines when to stop connecting to the terminal device based on the SN indicated by the second access network device, so that the terminal device's multicast service reception continuity is ensured in the handover process and packet loss or redundant transmission is avoided.

[0020] Referring to the first aspect, in some implementation forms of the first aspect, the first access network device sends stop instruction information to the second access network device to instruct the first access network device to disconnect from the first terminal device.

[0021] Referring to the first aspect, in some implementation forms of the first aspect, the second access network device sends fifth instruction information to the first access network device, where the fifth instruction information includes a second sequence number N-1, and the second sequence number instructs the first access network device to stop sending data packets to the terminal device if the first protocol layer sequence number of the data packet successfully sent by the first access network device to the terminal device is N-1.

[0022] Therefore, the first access network device no longer needs to perform calculations and can directly stop sending data packets after the data packet with the first sequence number N-1 is sent.

[0023] According to a second aspect, there is provided a communication method, applied to a terminal device, comprising: receiving second indication information from a first access network device, the second indication information indicating a sequence number of a first data packet belonging to a first service to be transmitted by the first access network device to the terminal device after a first protocol entity is established, after the first protocol entity is re-established, or after the first protocol entity is restored.

[0024] Referring to the second aspect, in some implementation forms of the second aspect, the method further includes a step of sending request information to the first access network device when the first protocol entity is re-established or recovered, the request information requesting the first access network device to send a sequence number of a first data packet belonging to the first service to be sent by the first access network device to the terminal device after the first protocol entity is re-established or the first protocol entity is recovered.

[0025] Referring to the second aspect, in some implementation forms of the second aspect, the method further includes a step of transmitting status report information of the data packets to a second access network device, wherein the status report information of the data packets indicates to the second access network device data packets that have been successfully received by the terminal device and data packets that have not been successfully received by the terminal device, and the terminal device is handed over from the first access network device to the second access network device.

[0026] According to a third aspect, there is provided a communication method, applied to a second access network device, comprising: receiving a first data packet and first indication information from a core network device, the first indication information indicating a sequence of the first data packet in at least one data packet; determining a second sequence number of a first protocol layer of the first data packet based on the first indication information; and transmitting the first data packet to a first terminal device.

[0027] Referring to the third aspect, in some implementation forms of the third aspect, the first indication information includes at least one of the following information: a General Packet Radio Service Tunneling Protocol-User Plane GTP-U sequence number and a first service sequence number, the first service sequence number is set by a core network device or a data server, the first data packet is a data packet of the first service, and the at least one data packet is a data packet of the first service.

[0028] Referring to the third aspect, in some implementations of the third aspect, the first protocol layer includes at least one of a Service Data Adaptation Protocol (SDAP) layer, a Packet Data Convergence Protocol (PDCP) layer, and a Radio Link Control (RLC) layer.

[0029] Referring to the third aspect, in some implementations of the third aspect, the method further includes setting a starting sequence number of the first protocol layer of the first data packet based on the first indication information when any one of establishment of the first protocol entity, re-establishment of the first protocol entity, and recovery of the first protocol entity occurs.

[0030] Referring to the third aspect, in some implementation forms of the third aspect, the method further includes a step of sending second instruction information to the terminal device, wherein the second instruction information indicates a sequence number of a first data packet belonging to the first service to be sent by the first access network device to the terminal device after the first protocol entity is established, after the first protocol entity is re-established, or after the first protocol entity is recovered.

[0031] Referring to the third aspect, in some implementation forms of the third aspect, the method further includes: receiving a data packet from a first access network device, wherein a second terminal device connected to the first access network device is handed over from the first access network device to the second access network device, both the first terminal device and the second terminal device are running a first service, and the data packet sent by the first access network device is a data packet of the first service; and if a second sequence number of a first protocol layer of the data packet being sent to the first terminal device is greater than or equal to the first sequence number of the first protocol layer of the data packet sent by the first access network device, sending third instruction information to the first access network device, wherein the third instruction information instructs the first access network device to stop forwarding the data packet to the second access network device.

[0032] Referring to the third aspect, in some implementation forms of the third aspect, the method further includes a step of receiving status report information of data packets from the second terminal device, where the status report information of the data packets indicates to the second access network device data packets that have been successfully received by the terminal device and data packets that have not been successfully received by the terminal device; and a step of sending fourth indication information to the first access network device based on the status report information, where the fourth indication information indicates a sequence number of a first data packet forwarded by the first access network device to the second access network device.

[0033] Referring to the third aspect, in some implementation forms of the third aspect, the method further includes a step of sending fifth instruction information to the first access network device, wherein the fifth instruction information includes a second sequence number N, and the second sequence number indicates a sequence number of a first data packet belonging to the first service to be sent by the second access network device to the second terminal device after handover of the second terminal device is completed.

[0034] According to a fourth aspect, there is provided a communication method, which is applied to a core network device and includes the steps of: receiving a first data packet sent by a data server; sending a second data packet and first indication information to a first access network device, where the first indication information indicates a sequence of the second data packet in at least one data packet sent by the core network device; and sending a third data packet and the second indication information to a second access network device, where the second indication information indicates a sequence of the third data packet in the at least one data packet of the core network device, and where data in the second data packet and data in the third data packet are the same as data in the first data packet.

[0035] Referring to the fourth aspect, in some implementation forms of the fourth aspect, the first indication information includes at least one of the following information: a General Packet Radio Service Tunneling Protocol-User Plane GTP-U sequence number and a first service sequence number, the first service sequence number is set by a core network device or a data server, the first data packet is a data packet of the first service, and the at least one data packet is a data packet of the first service.

[0036] According to a fifth aspect, there is provided an access network device, which may be a first access network device, a chip or module within the first access network device, or a chip or system-on-chip, including: a transceiver unit configured to receive a first data packet and first indication information from a core network device, the first indication information indicating a sequence of the first data packet in at least one data packet; and a processing unit configured to determine a first sequence number of a first protocol layer of the first data packet based on the first indication information, wherein the transceiver unit is further configured to transmit the first data packet to a terminal device.

[0037] Referring to the fifth aspect, in some implementation forms of the fifth aspect, the first indication information includes at least one of the following information: a General Packet Radio Service Tunneling Protocol-User Plane GTP-U sequence number and a first service sequence number, the first service sequence number is set by a core network device or a data server, the first data packet is a data packet of the first service, and the at least one data packet is a data packet of the first service.

[0038] Referring to the fifth aspect, in some implementations of the fifth aspect, the first protocol layer includes at least one of a Service Data Adaptation Protocol (SDAP) layer, a Packet Data Convergence Protocol (PDCP) layer, and a Radio Link Control (RLC) layer.

[0039] Referring to the fifth aspect, in some implementation forms of the fifth aspect, the processing unit is further configured to determine a starting sequence number of the first protocol layer of the first data packet based on the first indication information when any one of establishment of the first protocol entity, re-establishment of the first protocol entity, and recovery of the first protocol entity occurs.

[0040] Referring to the fifth aspect, in some implementation forms of the fifth aspect, the transceiver unit is further configured to send second instruction information to the terminal device, wherein the second instruction information indicates a sequence number of a first data packet belonging to the first service to be sent by the first access network device to the terminal device after the first protocol entity is established, after the first protocol entity is re-established, or after the first protocol entity is recovered.

[0041] Referring to the fifth aspect, in some implementation forms of the fifth aspect, the transceiver unit is further configured to receive third instruction information from the second access network device, the third instruction information instructing the first access network device to stop forwarding data packets to the second access network device, and the processing unit is configured to stop forwarding data packets to the second access network device based on the third instruction information.

[0042] Referring to the fifth aspect, in some implementation forms of the fifth aspect, the transceiver unit is further configured to receive fourth instruction information sent by the second access network device, the fourth instruction information indicating a sequence number of a first data packet forwarded by the first access network device to the second access network device, and the processing unit is configured to forward the data packet to the second access network device based on the fourth instruction information.

[0043] In relation to the fifth aspect, in some implementation forms of the fifth aspect, the transceiver unit is further configured to receive fifth instruction information sent by the second access network device, the fifth instruction information including a second sequence number N, the second sequence number indicating the sequence number of a first data packet belonging to the first service to be sent by the second access network device to the terminal device after handover of the terminal device is completed, and the processing unit is configured to determine to stop sending data packets to the terminal device if the sequence number belonging to the protocol layer corresponding to the data packet successfully sent by the first access network device to the terminal device is N-1.

[0044] According to a sixth aspect, there is provided a terminal device, which may be a terminal device, a chip or module within the terminal device, or a chip or system-on-chip. The terminal device includes a transceiver unit configured to receive second indication information sent by a first access network device, the second indication information indicating a sequence number of a first data packet belonging to a first service that is sent by the first access network device to the terminal device after the first protocol entity is established, after the first protocol entity is re-established, or after the first protocol entity is recovered.

[0045] Referring to the sixth aspect, in some implementation forms of the sixth aspect, the transceiver unit is further configured to send request information to the first access network device when the first protocol entity is re-established or recovered, the request information requesting the first access network device to send a sequence number of a first data packet belonging to the first service to be sent by the first access network device to the terminal device after the first protocol entity is re-established or the first protocol entity is recovered.

[0046] Referring to the sixth aspect, in some implementation forms of the sixth aspect, the transceiver unit is further configured to transmit status report information of the data packets to the second access network device, wherein the status report information of the data packets indicates to the second access network device the data packets that have been successfully received by the terminal device and the data packets that have not been successfully received by the terminal device, and the terminal device is handed over from the first access network device to the second access network device.

[0047] According to a seventh aspect, there is provided an access network device, which may be a second access network device, a chip or module within the second access network device, or a chip or system-on-chip. The access network device includes: a transceiver unit configured to receive a first data packet and first indication information from a core network device, the first indication information indicating a sequence of the first data packet in at least one data packet; and a processing unit configured to determine a second sequence number of a first protocol layer of the first data packet based on the first indication information, and the transceiver unit is configured to transmit the first data packet to a first terminal device.

[0048] Referring to the seventh aspect, in some implementation forms of the seventh aspect, the first indication information includes at least one of the following information: a General Packet Radio Service Tunneling Protocol-User Plane GTP-U sequence number and a first service sequence number, the first service sequence number is set by a core network device or a data server, the first data packet is a data packet of the first service, and the at least one data packet is a data packet of the first service.

[0049] Referring to the seventh aspect, in some implementations of the seventh aspect, the first protocol layer includes at least one of a Service Data Adaptation Protocol (SDAP) layer, a Packet Data Convergence Protocol (PDCP) layer, and a Radio Link Control (RLC) layer.

[0050] Referring to the seventh aspect, in some implementation forms of the seventh aspect, the processing unit is further configured to set a starting sequence number of the first protocol layer of the first data packet based on the first indication information when any one of establishment of the first protocol entity, re-establishment of the first protocol entity, and recovery of the first protocol entity occurs.

[0051] Referring to the seventh aspect, in some implementation forms of the seventh aspect, the transceiver unit is further configured to send second instruction information to the terminal device, wherein the second instruction information indicates a sequence number of a first data packet belonging to the first service to be sent by the first access network device to the terminal device after the first protocol entity is established, after the first protocol entity is re-established, or after the first protocol entity is recovered.

[0052] Referring to the seventh aspect, in some implementation forms of the seventh aspect, the transceiver unit is further configured to: receive a data packet transmitted by a first access network device; when a second terminal device connected to the first access network device is handed over from the first access network device to the second access network device, both the first terminal device and the second terminal device are running a first service, the data packet transmitted by the first access network device is a data packet of the first service, and a second sequence number of a first protocol layer of the data packet being transmitted to the first terminal device is greater than or equal to the first sequence number of the first protocol layer of the data packet transmitted by the first access network device, send third instruction information to the first access network device, wherein the third instruction information instructs the first access network device to stop forwarding the data packet to the second access network device.

[0053] Referring to the seventh aspect, in some implementation forms of the seventh aspect, the transceiver unit is further configured to: receive status report information for a data packet transmitted by the second terminal device, the status report information for the data packet indicating to the second access network device the data packet successfully received by the terminal device and the data packet not successfully received by the terminal device; and send fourth instruction information to the first access network device based on the status report information, the fourth instruction information indicating a sequence number of a first data packet forwarded by the first access network device to the second access network device.

[0054] Referring to the seventh aspect, in some implementation forms of the seventh aspect, the transceiver unit is further configured to send fifth instruction information to the first access network device, where the fifth instruction information includes a second sequence number N, and the second sequence number indicates a sequence number of a first data packet belonging to the first service to be sent by the second access network device to the second terminal device after handover of the second terminal device is completed.

[0055] According to an eighth aspect, there is provided a core network device, which may be a core network device, a chip or module within the core network device, or a chip or system-on-chip. The core network device includes a transceiver unit configured to receive a first packet transmitted by a data server, the transceiver unit configured to transmit a second data packet and first indication information to a first access network device, the first indication information indicating a sequence of the second data packets in the at least one data packet transmitted by the core network device, and the transceiver unit configured to transmit a third data packet and the second indication information to a second access network device, the second indication information indicating a sequence of the third data packets in the at least one data packet transmitted by the core network device, and data in the second data packet and data in the third data packet being the same as data in the first data packet.

[0056] Referring to the eighth aspect, in some implementation forms of the eighth aspect, the first indication information includes at least one of the following information: a General Packet Radio Service Tunneling Protocol-User Plane GTP-U sequence number and a first service sequence number, the first service sequence number is set by a core network device or a data server, the first data packet is a data packet of the first service, and the at least one data packet is a data packet of the first service.

[0057] According to a ninth aspect, there is provided a communications device, the device including a processor. The processor is connected to a memory. The memory is configured to store a computer program. The processor is configured to execute the computer program stored in the memory to enable the device to perform a method according to the first aspect or any one of possible implementations of the first aspect, a method according to the second aspect or any one of possible implementations of the second aspect, a method according to the third aspect or any one of possible implementations of the third aspect, or a method according to the fourth aspect or any one of possible implementations of the fourth aspect.

[0058] According to a tenth aspect, there is provided a computer-readable storage medium having stored thereon a computer program, which, when executed, performs a method according to the first aspect or any one of possible implementations of the first aspect, a method according to the second aspect or any one of possible implementations of the second aspect, a method according to the third aspect or any one of possible implementations of the third aspect, or a method according to the fourth aspect or any one of possible implementations of the fourth aspect.

[0059] According to an eleventh aspect, there is provided a chip including a processor and an interface, wherein the processor is configured to read instructions to perform a method according to the first aspect or any one of its possible implementations, a method according to the second aspect or any one of its possible implementations, a method according to the third aspect or any one of its possible implementations, or a method according to the fourth aspect or any one of its possible implementations.

[0060] Optionally, the chip may further include a memory, the memory storing instructions, and the processor configured to execute the instructions stored in the memory or other instructions.

[0061] According to a twelfth aspect, there is provided a communications system, the system including an apparatus capable of implementing the method and possible designs of the first aspect, an apparatus capable of implementing the method and possible designs of the second aspect, an apparatus capable of implementing the method and possible designs of the third aspect, and an apparatus capable of implementing the method and possible designs of the fourth aspect. [Brief explanation of the drawings]

[0062] [Figure 1] FIG. 1 is a schematic diagram of an application scenario according to an embodiment of the present application; [Figure 2] 1 is a schematic flowchart of a communication method according to an embodiment of the present application; [Figure 3] 1 is a schematic flowchart of a method for handing over a terminal device between access network devices in the prior art; [Figure 4] FIG. 1 is a schematic diagram of an application scenario of a multicast service according to an embodiment of the present application; [Figure 5] 1 is a schematic flowchart of a communication method according to an embodiment of the present application; [Figure 6] 2 is a schematic flowchart of data transfer in a communication method according to an embodiment of the present application; [Figure 7]1 is a schematic flowchart of a communication method according to an embodiment of the present application; [Figure 8] 1 is a schematic block diagram of a communication device according to an embodiment of the present application; [Figure 9] 1 is a schematic diagram of the structure of a terminal device according to the present application; [Figure 10] 1 is a schematic diagram of the structure of an access network device according to the present application; DETAILED DESCRIPTION OF THE INVENTION

[0063] The technical solutions in this application are described below with reference to the accompanying drawings.

[0064] To better understand the present application, terms that may appear in the embodiments of the present application are first explained.

[0065] The technical solutions in the embodiments of the present application may be applied to various communication systems, such as a global system for mobile communications (GSM) system, a code division multiple access (CDMA) system, a wideband code division multiple access (WCDMA) system, a general packet radio service (GPRS) system, a long term evolution (LTE) system, an LTE frequency division duplex (FDD) system, an LTE time division duplex (TDD), a universal mobile telecommunications system (UMTS), a worldwide interoperability for microwave access (WiMAX) communication system, a fifth generation (5G) system, or a new radio (NR) system. In addition, the technical solution may alternatively be applied to subsequent evolutionary systems, such as sixth generation 6G communication systems, or even more advanced seventh generation 7G communication systems.

[0066] A terminal device in embodiments of the present application may also be referred to as user equipment (UE), a mobile station (MS), a mobile terminal (MT), an access terminal, a subscriber unit, a subscriber station, a remote station, a remote terminal, a mobile device, a user terminal, a terminal, a wireless communication device, a user agent, or a user equipment.

[0067] A terminal device may be a wireless terminal or a wired terminal. A wireless terminal may refer to a device that provides a user with voice and / or other service data connectivity, a handheld device with wireless connectivity, or another processing device connected to a wireless modem. A wireless terminal can communicate with one or more core networks via a Radio Access Network (RAN). A wireless terminal may be a mobile terminal such as a mobile phone (also called a "cellular" phone) or a computer with a mobile terminal, e.g., a portable, pocket-sized, handheld, computer-integrated, or vehicle-mounted mobile device that exchanges voice and / or data with a radio access network. For example, a wireless terminal may be a device such as a Personal Communication Service (PCS) phone, a cordless phone, a Session Initiation Protocol (SIP) phone, a Wireless Local Loop (WLL) station, or a Personal Digital Assistant (PDA).A wireless terminal is also called a system, a subscriber unit, a subscriber station, a mobile station, a mobile, a remote station, a remote terminal, an access terminal, a user terminal, a user agent, a user device or user equipment, a mobile internet device (MID), a wearable device, a virtual reality (VR) device, an augmented reality (AR) device, a wireless terminal in industrial control, a wireless terminal in self driving, a wireless terminal in remote medical surgery, a wireless terminal in a smart grid, a wireless terminal in transportation safety, a wireless terminal in a smart city, a wireless terminal in a smart home, an in-vehicle device, a wearable device, a terminal device of a 5G network, a terminal device of a future evolved public land mobile network, a network (PLMN) terminal devices, etc. This is not limited in the embodiments of the present application.

[0068] By way of example and not limitation, in embodiments of the present application, a wearable device may also be referred to as a wearable intelligent device, which is a general term for wearable devices such as glasses, gloves, watches, clothes, and shoes that are developed based on an intelligent design and are worn daily using wearable technology. A wearable device is a portable device that is worn directly or integrated into a user's clothing or accessories. A wearable device is not only a hardware device, but also implements more powerful functions through software support, data exchange, and cloud interaction. Typical wearable intelligent devices include full-featured large devices, such as smart watches or smart glasses, that can implement full or partial functions without relying on a smartphone, and devices that focus only on one type of application function and need to cooperate with other devices such as smartphones, such as various smart bands for monitoring physical symptoms, or smart jewelry.

[0069] In addition, in the embodiments of the present application, the terminal device may alternatively be a terminal device in an internet of things (IoT) system. IoT is an important component of future information technology development. The main technical feature of IoT is to connect things to a network using communication technology to implement an intelligent network for interconnection between people and machines and between things.

[0070] When the various terminal devices described above are located in a vehicle (e.g., placed in or mounted in a vehicle), they may all be considered as on-board terminal devices, e.g., they may also be called on-board units (OBUs).

[0071] In the embodiment of the present application, the terminal device may further include a relay. Alternatively, it is understood that any device capable of performing data communication with a base station may be considered as a terminal device.

[0072] The access network device in the embodiments of the present application may be a device configured to communicate with a terminal device, and may be a base station, an access point, or a network device, or may refer to a device that communicates with a wireless terminal over an air interface in an access network using one or more sectors. The network device may be configured to convert received wireless communication frames to and from IP packets and act as a router between the wireless terminal and the rest of the access network, which may include an Internet Protocol (IP) network. The network device may further coordinate attribute management of the air interface. For example, the access network device may be a Base Transceiver Station (BTS) in a Global System for Mobile communications (GSM) or Code Division Multiple Access (CDMA), or a Node B (NB) in a Wideband Code Division Multiple Access (WCDMA) system, or an evolved Node B (eNB or eNodeB) in an LTE system, or a radio controller in a cloud radio access network (CRAN) scenario. Alternatively, the access device may be a relay station, an access point, an in-vehicle device, a wearable device, an access device in a 5G network, or a network device in a future evolved PLMN network, or may be an access point (AP) in a WLAN, or a gNB in ​​a new radio (NR) system. This is not limited to the embodiments of the present application.It should be noted that in a 5G system, one base station may have one or more Transmission Reception Points (TRPs). All TRPs belong to the same cell. The measurement reporting method in the embodiments of the present application may be used for each TRP and each terminal. In another scenario, a network device may be further divided into a control unit (CU) and a data unit (DU). One CU may correspond to multiple DUs. The measurement reporting method in the embodiments of the present application may be used for each DU and each terminal. The difference between the CU-DU division scenario and the multi-TRP scenario is that a TRP is simply a radio frequency unit or antenna device, while a DU can implement protocol stack functions, such as physical layer functions.

[0073] Additionally, in an embodiment of the present application, the access network device is a device in an access network (radio access network, RAN), in other words, a RAN node that connects a terminal device to a wireless network. For example, and not by way of limitation, the access network device may be a gNB, a transmission reception point (TRP), an evolved Node B (eNB), a radio network controller (RNC), a Node B (NB), a base station controller (BSC), a base transceiver station (BTS), a home base station (e.g., a home evolved NodeB or home NodeB, HNB), a base band unit (BBU), or a wireless fidelity (Wi-Fi) access point (AP).

[0074] An access network device provides a service to a cell. A terminal device communicates with the access network device by using transmission resources (e.g., frequency domain resources or spectrum resources) used for the cell. A cell may correspond to an access network device (e.g., a base station). A cell may belong to a macro base station or a base station corresponding to a small cell. Small cells here may include metro cells, micro cells, pico cells, femto cells, etc. Small cells have characteristics such as small coverage and low transmission power, and are suitable for providing high-speed data transmission services.

[0075] Unicast: Point-to-point communication technology, specifically, single-point communication between a network device and a terminal device. The network device may send data to each terminal device separately. Unicast is also sometimes called a unicast transmission mode or technology.

[0076] A transmission performed in unicast transmission mode means that when transmitting a transport block (TB) corresponding to a protocol data unit (PDU), the transmitting device scrambles the PDU or downlink control information (DCI) corresponding to the PDU using a cell network temporary identifier (C-RNTI), and the receiving device receives the same PDU based on the C-RNTI. Alternatively, transmitting a PDU in unicast mode may mean that the PDU is transmitted on a radio bearer established for unicast transmission or on a channel specially designed for unicast.

[0077] Reception performed in unicast transmission mode means that when transmission is performed in unicast mode, the receiving device receives the PDU based on the C-RNTI, or the receiving device receives the PDU on a radio bearer established for unicast transmission or a channel used for unicast transmission.

[0078] Multicast: A point-to-multipoint communication technology, also known as multicast transmission mode or multicast transmission technology, is used to provide multimedia broadcast multicast services. Multicast is also called groupcast and, in some generalized scenarios, broadcast technology. However, multicast differs from traditional broadcast technology. When multicast transmission mode is used, multiple terminal devices simultaneously receive the same data during the process of data transmission from a network device (e.g., a base station). Currently, multicast transmission technologies are mainly classified into two types: multimedia broadcast multicast service single frequency network (MBSFN) service and single cell point-to-multipoint (SC-PTM) service. In addition, other multicast transmission technologies are also described, which are not limited to the present invention.

[0079] A transmission performed in multicast transmission mode means that when transmitting a transport block (TB) corresponding to a protocol data unit (PDU), the transmitting device scrambles the PDU or downlink control information (DCI) corresponding to the PDU using a group radio network temporary identifier (G-RNTI), and one or more receiving devices receive the same PDU based on the G-RNTI. Alternatively, transmitting a PDU in multicast mode may mean that multiple receiving devices are semi-persistently notified of the location of the same PDU, and multiple receiving devices may receive the PDU simultaneously. Alternatively, transmitting a PDU in multicast mode may mean that the PDU is transmitted on a radio bearer established for multicast transmission or on a channel specially designed for multicast.

[0080] Reception in multicast transmission mode means that when transmission is performed by the peer side in multicast mode, one of the multiple receiving devices receives the PDU based on the G-RNTI, or one of the multiple receiving devices receives the PDU on a radio bearer established for multicast transmission or on a channel used for multicast transmission.

[0081] Broadcast: Point-to-multipoint communication technology. Unlike multicast, broadcast is a related technology in which a transmitting device transmits a TB corresponding to a PDU on a broadcast channel, and all receiving devices can receive the PDU on the broadcast channel. Unlike multicast technology, in conventional broadcast transmission, the above scrambling method using G-RNTI is not used for the broadcast channel.

[0082] Handover (HO): An ongoing call is handed over from one wireless channel to another to ensure that communication is not interrupted. In a wireless communication system, each cell covers a limited range. Therefore, when a terminal device moves from a current serving cell to an adjacent cell, in order to ensure service continuity, the network side needs to hand over service to the adjacent cell so that the communication process is not interrupted. Handover is a process in which a link carrying communication data is handed over from one cell (or base station) to another cell (or another base station) in the communication process, ensuring that communication is not interrupted.

[0083] Protocol Stack: Network devices and terminal devices have specific protocol layer structures used for intercommunication. For example, the control plane protocol layer structure may include a radio resource control (RRC) layer, a packet data convergence protocol (PDCP) layer, a radio link control (RLC) layer, a media access control (MAC) layer, and a physical layer. The user plane protocol layer structure may include a PDCP layer, an RLC layer, a MAC layer, a physical layer, etc. The physical layer is located at the bottom (Layer 1), the MAC layer, the RLC layer, and the PDCP layer belong to Layer 2 (Layer 2), and the RRC layer belongs to Layer 3 (Layer 3). In one implementation, a service data adaptation protocol (SDAP) layer may be further included above the PDCP layer. In addition, a transport layer, such as a Transmission Control Protocol / Internet Protocol (TCP / IP) layer and an application layer may further exist above the SDAP layer.

[0084] The functions of a protocol layer may be implemented by one node or multiple nodes. For example, in an evolved architecture, a radio access network device may include a centralized unit (CU) and a distributed unit (DU). Multiple DUs may be centrally controlled by one CU. The CU and DU may be obtained by dividing the radio network based on its protocol layer. For example, the CU is configured with functions of the PDCP layer and layers above the PDCP layer, while the DU is configured with functions of protocol layers below the PDCP layer, such as the RLC layer and MAC layer.

[0085] It should be understood that the segmentation based on the protocol layer is merely an example, and that alternatively, segmentation may be performed based on another protocol layer. For example, segmentation may be performed based on the RLC layer. The functions of the RLC layer and layers higher than the RLC layer are assigned to the CU, and the functions of protocol layers lower than the RLC layer are assigned to the DU. Alternatively, segmentation may be performed at the protocol layer. For example, some functions of the RLC layer and functions of protocol layers higher than the RLC layer are assigned to the CU, and the remaining functions of the RLC layer and functions of protocol layers lower than the RLC layer are assigned to the DU. In addition, segmentation may alternatively be performed in another manner. For example, segmentation may be performed based on latency. Functions that require processing time to meet latency requirements are assigned to the DU, and functions that do not require processing time to meet latency requirements are assigned to the CU.

[0086] Radio Bearer: Generally, a radio bearer can be understood as a transmission path or treatment used when data packets or signaling are transmitted over the air interface. Radio bearers include data radio bearers and signaling radio bearers. Radio bearers are established and configured using RRC signaling of network devices. The configuration of a radio bearer involves the configuration of protocol layers. Protocol layer entities of the network device and the terminal device transmit, receive, or process data packets or signaling on the radio bearer based on the configuration. Technically, a radio bearer can be understood as a transmission channel. Whether on the terminal device side or the network device side, each radio bearer includes one PDCP entity and at least one RLC entity for processing data packets transmitted on the radio bearer. In addition to establishing radio bearers, network devices may further add, modify, or delete (release) radio bearers using RRC signaling.

[0087] Multimedia broadcast and multicast services are used for point-to-multipoint unidirectional multimedia services, e.g., multimedia broadcast services are transmitted to users in a cell on a common channel over the air interface, or multicast services subscribed to by users in a cell are transmitted to users in multicast mode, thereby reducing air interface resources.

[0088] The following describes an application scenario of an embodiment of the present application. Figure 1 is a schematic diagram of an application scenario 100 according to an embodiment of the present application. Figure 1 includes an access network device 110, a terminal device 120, a terminal device 130, a terminal device 140, a terminal device 150, a terminal device 160, and a terminal device 170. For example, the access network device 110 operates in an evolved Universal Mobile Telecommunications System terrestrial radio access (E-UTRA) system, an NR system, or an advanced communications system or another communications system. The access network device 110 may communicate with the terminal device 120 to the terminal device 170 via a Uu interface. In the communications system, the terminal device 120 to the terminal device 170 may transmit uplink data to the access network device 110, and the access network device 110 may transmit downlink data from the terminal device 120 to the terminal device 170. In addition, the communications system may alternatively include the terminal device 150 to the terminal device 170. Access network device 110 may transmit downlink data from terminal device 120 to terminal device 150, access network device 110 transmits the downlink data to terminal device 120 and terminal device 150 in unicast mode, and access network device 110 transmits the downlink data to terminal device 130 and terminal device 140 in multicast mode. Terminal device 150 may alternatively transmit the downlink data to terminal device 160 and terminal device 170.

[0089] The access network device in FIG. 1 is, for example, a base station. The access network device corresponds to different devices in different systems. For example, the access network device may correspond to an eNB in ​​a 4G system, or may correspond to an access network device in 5G, for example, a gNB, in a 5G system. The technical solutions provided in the embodiments of the present application may alternatively be applied to future mobile communication systems. Therefore, the access network device in FIG. 1 may alternatively correspond to an access network device in a future mobile communication system. In FIG. 1, an example is used in which the access network device is a base station. In practice, for the access network device, please refer to the above description.

[0090] It should be understood that the communication system shown in Fig. 1 may further include more network nodes, for example, another terminal device or an access network device. The access network device or the terminal device included in the communication system shown in Fig. 1 may be the above-mentioned access network device or the terminal device in various forms, which are not shown one by one in the drawings in the embodiments of the present application.

[0091] Alternatively, the technical solution of the present application may be applied to other communication systems, provided that the transmission direction needs to be indicated within the communication system. In addition, the present application is not only applicable to a scenario where one access network device and multiple UEs exist (e.g., an SC-PTM scenario), but also to a scenario where multiple access network devices cooperate to simultaneously perform data communication with multiple UEs (e.g., an MBSFN scenario) and a multicast / broadcast scenario in 5G.

[0092] Hereinafter, the communication method provided in the present application will be described in detail with reference to Fig. 2. Fig. 2 is a schematic flowchart of a communication method 200 according to an embodiment in the present application. The method 200 may be applied to the scenario shown in Fig. 1, and of course, may also be applied to other communication scenarios, which is not limited in this embodiment of the present application.

[0093] It should be further understood that in this embodiment of the present application, the method is described using an example in which a terminal device, an access network device, and a core network device perform the method. By way of example and not limitation, the method may alternatively be performed by a chip, a chip system, a processor, etc. used in the terminal device, the access network device, and the core network device.

[0094] As shown in Fig. 2, the method 200 shown in Fig. 2 may include steps S201 to S210. Hereinafter, the steps of the method 200 will be described in detail with reference to Fig. 2.

[0095] S201: A data server sends at least one data packet of a first service to a core network device.

[0096] Optionally, the data server may include progress indication information of the first service in at least one data packet of the first service when transmitting at least one data packet to the core network device. The progress indication information indicates a sequence of a current data packet in the at least one data packet of the first service. The progress indication information of the first service may be a sequence number of the first service. The progress indication information may be carried in the data packet, for example in a header of the data packet. Alternatively, the indication information is transmitted separately and independently from the transmission of the data packet.

[0097] Optionally, before S201, the data server receives request information sent by the core network device. The request information requests the data server to include progress indication information of the first service in at least one data packet of the first service when the data server sends at least one data packet to the core network device. After receiving the request information sent by the core network device and sending at least one data packet of the first service to the core network device, the data server may include progress indication information of the first service in each data packet.

[0098] Optionally, the first service may be an MBMS service.

[0099] S202: A core network device receives at least one data packet belonging to a first service sent by a data server.

[0100] Specifically, upon receiving at least one data packet for a first service transmitted by a data server, the core network device determines an access network device that needs to receive the first service, and thereby transmits the at least one data packet separately to different access network devices.

[0101] S203: The core network device sends a first data packet and first indication information to the first access network device, where the first indication information indicates a sequence of the first data packet in the at least one data packet sent by the core network device.

[0102] It should be noted that in this embodiment, S201 and S202 are only optional steps, and S203 unnecessarily depends on S201 and S202. Specifically, the data packet received by the core network device may be received from another location or generated by the core network device. Optionally, the core network device may alternatively receive progress indication information from another location and determine the location of the data packet based on the progress indication information. In addition, the manner in which the core network device transmits data packets to different access network devices is not limited.

[0103] S204: The core network device sends the second data packet and second indication information to the second access network device, where the second indication information indicates the sequence order of the second data packet in the at least one data packet sent by the core network device. The data in the first data packet may be the same as or different from the data in the second data packet. This is not limited. When the data in the data packet received by the first access network device is the same as the data in the data packet received by the second access network device, the first indication information is the same as the second indication information.

[0104] For example, if a core network device sends five data packets with core network sequence numbers 1 to 5 to a first access network device and sends five data packets with core network sequence numbers 5 to 9 to a second access network device, the content and size of the last data packet among the five data packets received by the first access network device are the same as the content and size of the first data packet among the five data packets received by the second access network device, and the instruction information corresponding to the two data packets are the same.

[0105] Specifically, when a core network device transmits at least one data packet of a first service to an access network device, the at least one data packet can carry first indication information, so that the access network device can know the transmission progress of the first service. The first indication information can be implemented by setting a core network sequence number of the data packet. When transmitting data packets received from a data server to different access network devices, the core network device enables the same data packets (if the carried content or carried payload is the same) to carry the same core network sequence number, i.e., the same first indication information, and the first indication information identifies the sequence of the data packets in the at least one transmitted data packet.

[0106] Optionally, the first indication information includes at least one of information of a General Packet Radio Service Tunneling Protocol-U Sequence Number (GTP-U SN) and a first service sequence number, where the first service sequence number is set by a core network device or a data server, the first data packet is a data packet of the first service, and the at least one data packet is a data packet of the first service.

[0107] The following briefly describes the first service sequence number using a GTP-U sequence number as an example. Currently, during data transmission between a core network device and an access network device, the core network device establishes different PDU sessions or GTP tunnels with different access network devices for separate operations. Therefore, even if the core network device receives the same data packet from a data server, the core network device may set different GTP-U SNs when transmitting the same data packet to different access network devices. However, in this application, the core network device sets the same GTP-U SN for the data packet when transmitting the same data packet received from the data server or generated by the core network device to different access network devices. In a possible implementation, the GTP-U SN is set for each data packet based on instruction information from the data server. In this way, since the GTP-U SN is associated with the content of the data packet, different access network devices can determine service transmission progress based on the GTP-U SN.

[0108] Optionally, when the data server sends at least one data packet of the first service to the core network device, if the at least one data packet carries at least one first service sequence number corresponding to the at least one data packet, the core network device may send first indication information to the access network device based on the first service sequence number. The first indication information may be the first service sequence number carried in the at least one data packet. When the data server sends at least one data packet of the first service to the core network device, if the at least one data packet does not carry the first service sequence number, the core network device resets the first service sequence number of the at least one data packet based on the sequence in which the at least one data packet is received. For example, when the core network device receives data packet 1, data packet 2, and data packet 3 from the data server, the core network device may set the first service sequence number 1 for data packet 1, the first service sequence number 2 for data packet 2, and the first service sequence number 3 for data packet 3.

[0109] S205: The first access network device receives a first data packet and first indication information from the core network device.

[0110] It should be noted that the specific implementation form on which S205 relies in the aforementioned steps is not limited in this embodiment, provided that the first data packet and the first indication information are received from the core network device.

[0111] S206: The first access network device determines a first sequence number of a first protocol layer of the first data packet based on the first indication information.

[0112] Optionally, the first protocol layer includes at least one of the following protocol layers: a Service Data Adaptation Protocol SDAP layer, a Packet Data Convergence Protocol PDCP layer, and a Radio Link Control RLC layer.

[0113] It should be understood that the first protocol layer may be an upper layer protocol layer on the radio access network side, and the first protocol layer may also be called a Layer 2 protocol layer, and SDAP, PDCP, RLC, and MAC all belong to Layer 2 protocols. In addition, in subsequent technologies, new protocol layers may be introduced for new functions. Therefore, in this embodiment, the first protocol layer is not limited to existing protocol layers or may be a newly defined protocol layer.

[0114] Specifically, after receiving the first data packet, the first access network device determines a first protocol layer first sequence number of the first data packet based on the first indication information, and the first protocol layer first sequence number is used by the first protocol layer to process the first data packet, for example, to perform sorting or duplicate detection.

[0115] Optionally, when the first access network device establishes a first protocol layer entity for multicast transmission, when a re-establishment process occurs on the established first protocol layer entity for multicast transmission, or when a data recovery process occurs on the first protocol layer entity, the first protocol layer entity of the first access network device determines a starting sequence number of a first data packet based on the first indication information. A PDCP entity is used as an example. After the PDCP entity for multicast transmission is re-established, the access network device receives the first indication information of a first data packet. For example, if the first indication information is a core network sequence number, the core network sequence number corresponding to the first data packet is 5. In this case, the access network device also sets the PDCP sequence number of the first data packet to 5 instead of 0, at which PDCP sequence numbers start in the prior art. It can be ensured that the information corresponding to the data packet is current actual service progress information even when the first protocol layer entity is re-established or recovered.

[0116] S207: The second access network device receives a second data packet and first indication information from the core network device.

[0117] S208: The second access network device determines a second sequence number of the first protocol layer of the second data packet based on the first indication information.

[0118] In steps S206 and S208, after receiving the data packets and core network sequence numbers sent by the core network devices, the first access network device and the second access network device need to determine the sequence numbers of the received data packets. To understand the steps more clearly, the steps are briefly described below with reference to FIG. 6. The first access network device receives a first data packet whose core network sequence number (GTP-U SN) is 8, and determines that the PDCP SN of the first data packet is 8 based on the GTP-U SN of the first data packet. The second access network device receives a data packet whose core network sequence number (GTP-U SN) is 11, and since the GTP-U SN of the second data packet is 11, the second access network device determines that the PDCP SN of the second data packet is 11. PDCP is an example of a first protocol layer.

[0119] It should be understood that the second access network device may alternatively be the first access network device. For a description of the second access network device, please refer to the above description of the first access network device. Details will not be repeated here.

[0120] It should be further understood that the core network device transmits the same first service to the first access network device and the second access network device and includes the same first indication information in data packets having the same content, so that the first access network device and the second access network device can determine the same first protocol layer sequence number for data packets having the same content based on the same first indication information. That is, the sequence numbers of the first protocol layer determined by different access network devices are the same for data packets having the same data. Therefore, in the process of handing over the terminal device from the first access network device to the second access network device, the second access network device can know the first service progress of the first access network device based on the SN state transfer and data transfer steps in the existing handover procedure without introducing additional progress information between the two access network devices.

[0121] This embodiment includes multiple sequence numbers. The sequence numbers of the protocol layers of the data server, core network device, access network device, and terminal device may be set for the protocol layers. For example, the core network sequence number is a sequence number set by the core network device for a data packet, and the PDCP sequence number is a sequence number set by the PDCP layer of the access network device or terminal device for a data packet. Different sequence numbers have different functions in different packets of the same data packet and are visible only to the corresponding device or protocol layer. Furthermore, the term "sequence number" refers to all sequence numbers collectively and is not limited to a specific sequence number. The specific sequence number needs to be specifically determined based on the scenario. For example, the sequence number of the PDCP layer is a PDCP sequence number.

[0122] It should be further noted that when a data packet is transmitted from a core network device to an access network device and then to a terminal device, the data packet is processed at many different protocol layers (e.g., a data packet header is added). The processing is necessary for transmission. After processing, the size or shape of the data packet may change. However, as long as the content of the payload of the data packet does not change, the data packet may be referred to as the same data packet, e.g., a first data packet.

[0123] S209: The first access network device sends a first data packet to the first terminal device.

[0124] Optionally, the first access network device may send second indication information to the first terminal device, where the second indication information indicates a sequence number of a first data packet belonging to the first service to be sent by the first access network device to the first terminal device after the first protocol entity of the first terminal device is established, after the first protocol entity is re-established, or after data recovery occurs on the first protocol entity.

[0125] In a possible implementation, when the first protocol entity is established before the first terminal device starts receiving the first service, the first terminal device first obtains configuration information for receiving the first protocol entity from the first access network device. The first access network device includes second instruction information in the configuration information, which indicates a sequence number (e.g., PDCP SN) of a first data packet of the first service transmitted by the first access network device. In this way, the terminal device can know the sequence number of the first data packet to be received. If the sequence number of the first received data packet is greater than the sequence number indicated by the instruction information, it indicates that the data packet has been lost. The terminal device can determine the lost data packet and request the access network device to retransmit the lost data packet.

[0126] In addition, when a re-establishment process or a data recovery process occurs on the first protocol entity used by the terminal device to transmit the first service, the access network device also needs to send second indication information to the first terminal device, where the second indication information indicates a sequence number (e.g., PDCP SN) of the first data packet of the first service sent by the first access network device. Thus, data packet loss caused by inconsistent understanding of the first data packet by the first terminal device and the first access network device can be avoided.

[0127] S210: A second access network device sends a second data packet to a second terminal device.

[0128] Optionally, the second access network device may send second indication information to the second terminal device.For specific description, please refer to the relevant description of S209.Details will not be repeated here.

[0129] According to the communication method 200 provided in the present application, in the process of a terminal device being handed over from a first access network device to a second access network device, the second access network device can know the first service progress of the first access network device based on the SN state transfer and data transfer steps in the existing handover procedure without introducing additional progress exchange information between the two access network devices. In this way, it is possible to avoid the case where redundant data packets are received by the terminal or service data is interrupted due to inconsistent multicast service progress of different access network devices.

[0130] To better understand the beneficial effects of the method provided in the present application, the following briefly describes a procedure for handing over a terminal device between access network devices (e.g., base stations) in the prior art. The procedure for handover between base stations (gNBs) is shown in FIG. 3. FIG. 3 is a schematic flowchart of a method 300 for handing over a terminal device between access network devices in the prior art. The handover is initiated by a source gNB. The source gNB (Source gNB, SgNB) decides to hand over the UE based on a measurement report reported by the UE and initiates a handover request to a target gNB (Target gNB, TgNB). After the SgNB obtains a positive handover confirmation response from the TgNB, the SgNB sends a handover command to the UE. After the UE receives the handover command, the UE stops uplink or downlink data transmission with the SgNB, starts synchronization with the TgNB, and initiates a random access process. When sending the handover command to the UE, the SgNB stops performing uplink or downlink data transmission with the UE and transmits data stored in the SgNB to the TgNB. After successfully accessing the TgNB, the UE starts transmitting uplink or downlink data with the TgNB. The method 300 shown in FIG. 3 may include S301 to S308. The steps of the method 300 will be briefly described below with reference to FIG. 3.

[0131] S301: In the handover preparation phase, a UE in an RRC connected state sends a “Measurement Report” according to the measurement report trigger criteria configured by the gNB.

[0132] S302: If the UE meets the handover conditions, the source gNB determines a target gNB for the UE based on the UE's measurement report and the radio resource management algorithm (RRM algorithm), and sends UE context information to the target gNB via a handover request.

[0133] S303: The target gNB prepares the UE to be handed over to the target gNB, assigns a cell identity parameter C-RNTI and other parameters to the UE, and returns the C-RNTI and other parameters to the source gNB via a handover request acknowledgement message. After receiving the handover request acknowledgement message, the source gNB prepares to forward packet data to the target gNB.

[0134] S304: The SgNB sends a "Handover Command" to the UE (the Handover Command includes the following information: a new C-RNTI, the SIB of the target gNB, and the UE's configuration information such as the configuration of the MAC, RLC, and PDCP layers). After receiving the Handover Command, the UE stops uplink or downlink data transmission with the source gNB and synchronizes with the target gNB.

[0135] In this case, the source gNB forwards the buffered uplink data transmitted by the UE and the buffered downlink data transmitted by the UPF to the target gNB.

[0136] S305: The source gNB sends SN status information and forwards data (dashed step) to the target gNB.

[0137] S306: After disconnecting data transmission with the source gNB, the UE initiates a downlink synchronization process with the target gNB, and then initiates a random access process to obtain uplink timing and uplink resource allocation. The target gNB sends a tracking area TA to the UE to indicate the resources allocated to the UE. This information is used by the UE to send an RRC connection reconfiguration complete message to the target gNB to indicate handover completion.

[0138] S307: The UE sends “Handover Acknowledgement” information to the target gNB to indicate handover completion.

[0139] S308: The target gNB indicates handover completion to the source gNB, which causes the source gNB to release the UE context information.

[0140] Furthermore, the target gNB notifies the core network node to update information about the target gNB to which the data is forwarded so that the core network can transmit the UE's data to the target gNB.

[0141] In some multicast application scenarios, a UE receives a multicast (groupcast) service from a base station, moves instantaneously, and needs to perform a handover procedure to be handed over to another base station to receive the multicast service. If the progress of the multicast services of the two base stations does not match, the existing handover procedure may cause the UE to receive redundant data packets or cause data interruption for the UE. FIG. 4 is a schematic diagram of a multicast service handover scenario 400. In FIG. 4, a core network device 410, an access network device 420, an access network device 430, a terminal device 440, and a terminal device 450 are included. The access network device 420 and the access network device 430 receive multicast service data transmitted by the core network device 410 and transmit the multicast service data to the terminal device within the coverage of the access network device 420 and the access network device 430. The terminal device 450 is handed over from the access network device 420 to the access network device 430. The progress of the multicast services of the access network device 420 and the access network device 430 does not match. Existing handover procedures may cause the terminal device 450 to receive redundant data packets or cause data interruptions for the terminal device 450 .

[0142] To solve the problem, the present application provides a communication method 500. Hereinafter, the communication method provided in the present application will be described in detail with reference to FIG. 5. FIG. 5 is a schematic flowchart of the communication method 500 according to an embodiment of the present application. The method 500 may be applied to the scenario shown in FIG. 1, and naturally may also be applied to another communication scenario, which is not limited to this embodiment of the present application. In the method 500, a first terminal device connected to a first access network device is handed over from the first access network device to a second access network device, and both the first access network device and the second access network device run a first service.

[0143] It should be understood that before and after handover of the first terminal device, the first terminal device uses the same protocol entity to process data packets received from the first access network device and the second access network device before and after handover, for example, to perform sorting or duplicate detection.

[0144] It should be further understood that in this embodiment of the present application, the method is described using an example in which a terminal device and an access network device perform the method, and by way of example and not limitation, the method may alternatively be performed by a chip, a chip system, a processor, etc. used in the terminal device and the access network device.

[0145] As shown in Fig. 5, the method 500 shown in Fig. 5 may include S501 to S505. Hereinafter, the steps of the method 500 will be described in detail with reference to Fig. 5.

[0146] S501: A first access network device forwards a data packet to a second access network device, and the data packet sent by the first access network device is a data packet of a first service.

[0147] S502: A second access network device receives a data packet sent by the first access network device.

[0148] Specifically, during the handover process, the first access network device needs to forward data sent by the core network device that is not successfully transmitted to the first terminal device to the second access network device. This is a data forwarding process. The sequence numbers of the first protocol layers of the two access network devices are determined based on the first indication information sent by the core network device. Therefore, for data packets with the same content, the sequence numbers of the first protocol layers determined by the two access network devices are the same. Therefore, after receiving the data packets forwarded by the first access network device, the second access network device can know the transmission progress of the first service in the first access network device based on the sequence numbers of the first protocol layers of the data packets and can use the corresponding transmission policy to ensure service continuity for the first terminal device.

[0149] S503: The second access network device determines whether to send third instruction information to the first access network device based on the second sequence number of the first protocol layer of the data packet being sent to the first terminal device and the first sequence number of the first protocol layer of the data packet received from the first access network device, wherein the third instruction information instructs the first access network device to stop forwarding the data packet to the second access network device.

[0150] Optionally, when a second sequence number of the first protocol layer of the data packet being transmitted by the second access network device to the first terminal device is greater than or equal to the first sequence number of the first protocol layer of the data packet transmitted by the first access network device, the second access network device transmits third indication information to the first access network device.

[0151] Optionally, when the second sequence number of the first protocol layer of the data packet being sent by the second access network device to the first terminal device is N and the first sequence number of the first protocol layer of the data packet sent by the first access network device is N-1, the second access network device sends third indication information to the first access network device.

[0152] Specifically, after the terminal device is successfully handed over, the second access network device begins transmitting data packets of the first service to the terminal device, and the first access network device forwards to the second access network device data packets of the first service that were not successfully received by the terminal from the first access network device. If the sequence number of the data packet received by the second access network device from the first access network device is equal to or greater than the sequence number of the data packet transmitted to the terminal device, the second access network device instructs the data forwarding to stop. It is assumed that the transmission progress of the second access network device is fast for the first service. Figure 6 is a schematic flowchart of data forwarding in a communication method according to this embodiment of the present application. The user plane function receives data packets of the first service transmitted by the data server. When the data server transmits data packets of the first service, the data server includes indication information, such as a service sequence number, in the data packets. The user plane function transmits the received data packets of the first service to the first access network device and the second access network device separately. However, the progress of transmitting data packets to the first access network device and the second access network device by the user plane function is inconsistent. The maximum sequence number of data packets of the first service transmitted by the first access network device is SN=8, and the maximum sequence number of data packets of the first service transmitted by the second access network device is SN=11. In this case, after the first terminal device is handed over to the second access network device, when the first terminal device receives the first service based on the transmission progress of the second access network device, data packets with SNs 9 and 10 will be lost. Therefore, the first access network device forwards the data packets with SNs 9 and 10 to the second access network device.When the progress of the data packet forwarded by the first access network device catches up with the transmission progress of the second access network device, i.e., when the sequence number of the data packet received by the second access network device from the first access network device is equal to or greater than the SN of the first data packet belonging to the first service sent by the second access network device after the terminal device is successfully handed over to the second access network device, the second access network device sends stop indication information to the first access network device to indicate that data forwarding has ended.

[0153] In an optional implementation, the third indication information may include identification information of the first service.

[0154] S504: The first access network device receives third indication information from the second access network device.

[0155] S505: The first access network device stops forwarding the data packet to the second access network device based on the third indication information.

[0156] Specifically, after receiving the instruction information, the first access network device stops data forwarding, whereas the first access network device continues to perform data forwarding before receiving the stop instruction information of the target base station.

[0157] Therefore, in the handover process of the first terminal device, the second access network device determines whether the data forwarding of the first access network device can be stopped, and sends data forwarding stop instruction information to the first access network device, so that the continuity of multicast service reception of the terminal device in the handover process is guaranteed, and packet loss or redundant transmission is avoided.

[0158] Optionally, before step S501, the method 500 may further include the following steps:

[0159] The second access network device receives status report information for data packets transmitted by the first terminal device, and the status report information for the data packets indicates to the second access network device data packets for the first service that have been successfully received by the first terminal device and data packets that have not been successfully received by the first terminal device.

[0160] The second access network device sends fourth instruction information to the first access network device based on the status report information, and the fourth instruction information indicates a sequence number of a first data packet forwarded by the first access network device to the second access network device, and the first data packet is a data packet that the first access network device starts forwarding to the second access network device or a data packet having the smallest sequence number among all forwarded data packets in the data forwarding process.

[0161] The first access network device receives the fourth indication information sent by the second access network device.

[0162] The first access network device forwards the data packet to the second access network device based on the fourth indication information.

[0163] Specifically, the first terminal device transmits status report information of data packets to the second access network device after handover, where the status report information indicates to the second access network device the data packets successfully received by the first terminal device and the data packets not successfully received by the first terminal device. After receiving the status report information, the second access network device transmits fourth indication information to the first access network device, where the fourth indication information indicates the first protocol layer sequence number of the first data packet not received by the first terminal device, i.e., the starting data packet in the data forwarding by the first access network device. In this way, the first terminal device can be prevented from receiving redundant data packets. Specifically, the following case can be avoided: A data packet transmitted by the first access network device is successfully received by the first terminal device but is still forwarded by the first access network device to the second access network device and then transmitted by the second access network device to the first terminal device.

[0164] The present application provides a communication method 600. Hereinafter, the communication method provided in the present application will be described in detail with reference to FIG. 7. FIG. 7 is a schematic flowchart of the communication method 600 according to an embodiment of the present application. The method 600 may be applied to the scenario shown in FIG. 1, and of course, may also be applied to other communication scenarios. This is not limited to this embodiment of the present application. In the method 600, in a process in which a first terminal device connected to a first access network device is handed over from the first access network device to a second access network device, the terminal device remains connected to both the first access network device and the second access network device. In this way, the first access network device and the second access network device may simultaneously transmit a first service to the terminal device. The first access network device may continue to transmit data packets that were not successfully received by the terminal device before the handover. In addition, the terminal device may receive data packets of the first service from the second access network device. If the sequence number of a data packet received from the first access network device may be consecutive to the sequence number of a data packet received from the second access network device (e.g., a data packet with the highest SN9 is received from the first access network device and a data packet with the lowest SN10 is received from the second access network device), the first access network device may stop sending data packets to the terminal device and may disconnect from the terminal device.

[0165] It should be further understood that in this embodiment of the present application, the method is described using an example in which a terminal device and an access network device perform the method, and by way of example and not limitation, the method may alternatively be performed by a chip, a chip system, a processor, etc. used in the terminal device and the access network device.

[0166] As shown in Fig. 7, the method 600 shown in Fig. 7 may include S601 to S603. Hereinafter, the steps of the method 600 will be described in detail with reference to Fig. 7.

[0167] S601: The second access network device sends fifth instruction information to the first access network device, where the fifth instruction information includes a first sequence number N, and the first sequence number indicates the sequence number of a first data packet belonging to the first service that is sent by the second access network device to the first terminal device after the first terminal device is successfully handed over from the first access network device to the second access network device.

[0168] S602: The first access network device receives fifth indication information sent by the second access network device.

[0169] S603: If the sequence number of the data packet successfully sent by the first access network device to the terminal device is N-1, the first access network device stops sending data packets to the terminal device.

[0170] Therefore, in the handover process, the first access network device determines when to stop connecting to the terminal device based on the SN indicated by the second access network device, so that the terminal device's multicast service reception continuity is ensured in the handover process and packet loss or redundant transmission is avoided.

[0171] Specifically, in the handover process, the first terminal device receives data packets of the first service from both the first access network device and the second access network device. The first access network device does not need to forward the data packets of the first service to the second access network device. That is, no data forwarding process is required. For example, in FIG. 5, data forwarding is not performed for data packets with SNs 9 and 10, and the data packets are directly sent by the first access network device to the first terminal device. After the first terminal device is successfully handed over to the second access network device, the second access network device may send the SN (e.g., 11) of the first data packet of the first service to be sent to the terminal device to the first access network device. The first access network device determines when to stop sending data to the first terminal device based on the SN of the first data packet. If the sequence number of the first protocol layer of the data packet successfully transmitted by the first access network device to the terminal device is N-1, the first access network device stops transmitting data packets to the first terminal device. For example, in FIG. 5, after transmitting the data packet numbered 11-1=10, the first access network device disconnects from the first terminal device.

[0172] Optionally, the first access network device sends stop instruction information to the second access network device to instruct the first access network device to disconnect from the first terminal device.

[0173] Optionally, when the terminal device is successfully handed over to the second access network device, the second access network device may send information indicating that the first terminal device has been successfully handed over to the first access network device. After the first access network device receives the information indicating that the first terminal device has been successfully handed over, the first access network device sends to the second access network device a first sequence number of a first protocol layer newly sent to the first terminal device, and the second access network device determines whether to stop sending data packets of the first service to the first terminal device based on the first sequence number of the first protocol layer and the second sequence number of the first protocol layer, where the second sequence number of the first protocol layer is the first protocol layer sequence number of a first data packet received by the first terminal device from the second access network device after the first terminal device is handed over from the first access network device to the second access network device. When the first sequence number of the first protocol layer is greater than the second sequence number of the first protocol layer, the second access network device sends instruction information to the first access network device to instruct the first access network device to disconnect from the first terminal device.

[0174] Optionally, the second access network device sends fifth instruction information to the first access network device, where the fifth instruction information includes a first sequence number N-1, and the first sequence number instructs the first access network device to stop sending data packets to the terminal device if a first protocol layer sequence number of a data packet successfully sent by the first access network device to the terminal device is N-1.

[0175] Therefore, the first access network device no longer needs to perform calculations and can directly stop sending data packets after the data packet with the first sequence number N-1 is sent.

[0176] Above, the method for measuring communication parameters of a multi-SIM terminal device according to an embodiment of the present application has been described in detail with reference to Figures 1 to 7. Hereinafter, the communication device according to an embodiment of the present application will be described in detail with reference to Figures 8 to 10.

[0177] FIG. 8 is a schematic block diagram of a communication device 700 according to an embodiment of the present application.

[0178] In some embodiments, the apparatus 700 may be a terminal device or may be a chip or circuit, for example, a chip or circuit that may be located in a terminal device.

[0179] In some embodiments, the apparatus 700 may be an access network device or may be a chip or circuit, for example, a chip or circuit that may be located in an access network device.

[0180] In some embodiments, the apparatus 700 may be a core network device or may be a chip or circuit, for example, a chip or circuit that may be located in a core network device.

[0181] In a possible manner, the apparatus 700 may include a processing unit 710 (i.e., an example of a processor) and a transceiver unit 730. In some possible implementations, the processing unit 710 may also be referred to as a determining unit. In some possible implementations, the transceiver unit 730 may include a receiving unit and a transmitting unit.

[0182] In possible implementations, the transceiver unit 730 may be implemented using a transceiver, transceiver-related circuitry, or interface circuitry.

[0183] In one implementation, the device may further include a storage unit 720. Possibly, the storage unit 720 is configured to store instructions. In one implementation, the storage unit may alternatively be configured to store data or information. The storage unit 720 may be implemented using a memory.

[0184] In some possible designs, processing unit 710 is configured to execute instructions stored in storage unit 720, such that apparatus 700 performs steps performed by a terminal device in the aforementioned methods. Alternatively, processing unit 710 may be configured to access data in storage unit 720, such that apparatus 700 performs steps performed by a terminal device in the aforementioned methods.

[0185] In some possible designs, processing unit 710 is configured to execute instructions stored in storage unit 720 such that apparatus 700 performs the steps performed by the access network device in the aforementioned methods. Alternatively, processing unit 710 may be configured to access data in storage unit 720 such that apparatus 700 performs the steps performed by the access network device in the aforementioned methods.

[0186] For example, the processing unit 710, the storage unit 720, and the transceiver unit 730 may communicate with each other and transfer control and / or data signals using an internal connection path. For example, the storage unit 720 may be configured to store a computer program, and the processing unit 710 may be configured to call the computer program from the storage unit 720 and execute the computer program, control the transceiver unit 730 to receive and / or send signals, and complete the steps of the terminal device or the access network device in the aforementioned methods. The storage unit 720 may be integrated into the processing unit 710 or provided separately from the processing unit 710.

[0187] Optionally, when the apparatus 700 is a communication device (e.g., a terminal device or an access network device), the transceiver unit 730 includes a receiver and a transmitter. The receiver and the transmitter may be the same physical entity or different physical entities. When the receiver and the transmitter are the same physical entity, the receiver and the transmitter may be collectively referred to as a transceiver.

[0188] If the device 700 is a terminal device or an access network device or a core network device, the transceiver unit 730 may be a transmitting unit or transmitter when transmitting information, and may be a receiving unit or receiver when receiving information. The transceiver unit may be a transceiver. The transceiver, transmitter, or receiver may be a radio frequency circuit. If the device includes a memory unit, the memory unit is configured to store computer instructions. The processor is communicatively connected to the memory. The processor executes the computer instructions stored in the memory, thereby enabling the device to perform method 200, method 500, or method 600. The processor may be a general-purpose central processing unit (CPU), a microprocessor, or an application-specific integrated circuit (ASIC).

[0189] Optionally, if the apparatus 700 is a chip or a circuit, the transceiver unit 730 includes an input interface and an output interface.

[0190] If the apparatus 700 is a chip, the transceiver unit 730 may be an input and / or output interface, pins, circuitry, etc. The processing unit 710 may execute computer-executable instructions stored in a memory unit such that the apparatus can perform method 200, method 500, or method 600. Optionally, the memory unit is a memory unit within the chip, such as a register or buffer, or the memory unit may be a memory unit within the terminal but outside the chip, such as a read-only memory (ROM), another type of static storage device capable of storing static information and instructions, or a random access memory (RAM).

[0191] In one implementation, the functionality of the transceiver unit 730 may be considered to be implemented using transceiver circuitry or a dedicated transceiver chip. The processing unit 710 may be considered to be implemented using a dedicated processing chip, processing circuitry, processing unit, or a general-purpose chip.

[0192] In another implementation form, the communication device (e.g., a terminal device or an access network device) provided in this embodiment of the present application may be considered to be implemented using a general-purpose computer, i.e., the storage unit 720 stores program code for implementing the functions of the processing unit 710 and the transceiver unit 730, and the general-purpose processing unit executes the code in the storage unit 720 to implement the functions of the processing unit 710 and the transceiver unit 730.

[0193] In some embodiments, the apparatus 700 may be an access network device, the access network device may be a first access network device, or may be a chip or circuit disposed in the first access network device. When the apparatus 700 is the first access network device or a chip or circuit disposed in the first access network device, the transceiver unit 730 is configured to receive a first data packet and first indication information from a core network device, the first indication information indicating a sequence of the first data packet in the at least one data packet; the processing unit 710 is configured to determine a first sequence number of a first protocol layer of the first data packet based on the first indication information; and the transceiver unit 730 is configured to transmit the first data packet to the terminal device.

[0194] In one implementation, the first indication information includes at least one of the following information: a General Packet Radio Service Tunneling Protocol-User Plane GTP-U sequence number and a first service sequence number, where the first service sequence number is set by a core network device or a data server, the first data packet is a data packet of the first service, and at least one data packet is a data packet of the first service.

[0195] In one implementation, the first protocol layer includes at least one of a Service Data Adaptation Protocol (SDAP) layer, a Packet Data Convergence Protocol (PDCP) layer, and a Radio Link Control (RLC) layer.

[0196] In one implementation, the processing unit 710 is further configured to determine a starting sequence number of the first protocol layer of the first data packet based on the first indication information when any one of establishment of the first protocol entity, re-establishment of the first protocol entity, and recovery of the first protocol entity occurs.

[0197] In one implementation, the transceiver unit 730 is further configured to send second instruction information to the terminal device, where the second instruction information indicates a sequence number of a first data packet belonging to the first service to be sent by the first access network device to the terminal device after the first protocol entity is established, after the first protocol entity is re-established, or after the first protocol entity is recovered.

[0198] In one implementation, the transceiver unit 730 is further configured to receive third instruction information from the second access network device, the third instruction information instructing the first access network device to stop forwarding data packets to the second access network device. The processing unit 710 is configured to stop forwarding data packets to the second access network device based on the third instruction information.

[0199] In one implementation, the transceiver unit 730 is further configured to receive fourth indication information sent by the second access network device, where the fourth indication information indicates a sequence number of a first data packet forwarded by the first access network device to the second access network device. The processing unit 710 is configured to forward the data packet to the second access network device based on the fourth indication information.

[0200] In one implementation, the transceiver unit 730 is further configured to receive fifth instruction information sent by the second access network device, where the fifth instruction information includes a first sequence number N and the fifth instruction information includes a second sequence number N, where the second sequence number indicates a sequence number of a first data packet belonging to the first service to be sent by the second access network device to the terminal device after handover of the terminal device is completed. The processing unit 710 is configured to determine to stop sending data packets to the terminal device when a sequence number belonging to a protocol layer corresponding to a data packet successfully sent by the first access network device to the terminal device is N-1.

[0201] If the apparatus 700 is configured in or is a first access network device, the modules or units in the apparatus 700 may be configured to perform the operations or processing steps performed by the first access network device in the above-described manner. To avoid repetition, detailed descriptions are omitted here.

[0202] In some embodiments, the apparatus 700 may be a terminal device, or a chip or circuit disposed in the terminal device. When the apparatus 700 is a terminal device, or a chip or circuit disposed in the terminal device, the transceiver unit 730 is configured to receive second indication information sent by the first access network device, where the second indication information indicates a sequence number of a first data packet belonging to the first service that is sent by the first access network device to the terminal device after the first protocol entity is established, after the first protocol entity is re-established, or after the first protocol entity is recovered.

[0203] In one implementation, the transceiver unit 730 is further configured to send request information to the first access network device when the first protocol entity is re-established or recovered, the request information requesting the first access network device to send a sequence number of a first data packet belonging to the first service to be sent by the first access network device to the terminal device after the first protocol entity is re-established or the first protocol entity is recovered.

[0204] In one implementation, the transceiver unit 730 is further configured to send status report information of the data packets to the second access network device, wherein the status report information of the data packets indicates to the second access network device the data packets that have been successfully received by the terminal device and the data packets that have not been successfully received by the terminal device, and the terminal device is handed over from the first access network device to the second access network device.

[0205] If the apparatus 700 is configured as or is a terminal device, the modules or units of the apparatus 700 may be configured to perform the operations or processing steps performed by the first terminal device in the above-described manner, and detailed descriptions thereof will be omitted here to avoid repetition.

[0206] In some embodiments, the apparatus 700 may be an access network device, the access network device may be a first access network device, or may be a chip or circuit disposed in the first access network device. When the apparatus 700 is the first access network device or a chip or circuit disposed in the first access network device, the transceiver unit 730 is configured to receive a first data packet and first indication information from a core network device, the first indication information indicating a sequence of the first data packet in the at least one data packet; the processing unit 710 is configured to determine a first sequence number of a first protocol layer of the first data packet based on the first indication information; and the transceiver unit 730 is configured to transmit the first data packet to the terminal device.

[0207] In one implementation, the first indication information includes at least one of the following information: a General Packet Radio Service Tunneling Protocol-User Plane GTP-U sequence number and a first service sequence number, where the first service sequence number is set by a core network device or a data server, the first data packet is a data packet of the first service, and at least one data packet is a data packet of the first service.

[0208] In one implementation, the first protocol layer includes at least one of a Service Data Adaptation Protocol (SDAP) layer, a Packet Data Convergence Protocol (PDCP) layer, and a Radio Link Control (RLC) layer.

[0209] In one implementation, the processing unit 710 is further configured to determine a starting sequence number of the first protocol layer of the first data packet based on the first indication information when any one of establishment of the first protocol entity, re-establishment of the first protocol entity, and recovery of the first protocol entity occurs.

[0210] In one implementation, the transceiver unit 730 is further configured to send second instruction information to the terminal device, where the second instruction information indicates a sequence number of a first data packet belonging to the first service to be sent by the first access network device to the terminal device after the first protocol entity is established, after the first protocol entity is re-established, or after the first protocol entity is recovered.

[0211] In one implementation, the transceiver unit 730 receives a data packet transmitted by a first access network device; When a second terminal device connected to the first access network device is handed over from the first access network device to the second access network device, and both the first terminal device and the second terminal device are running a first service, and a data packet sent by the first access network device is a data packet of the first service, and a second sequence number of the first protocol layer of the data packet being sent to the first terminal device is equal to or greater than a first sequence number of the first protocol layer of the data packet sent by the first access network device, sending third instruction information to the first access network device, wherein the third instruction information instructs the first access network device to stop forwarding the data packet to the second access network device; It is further configured as follows.

[0212] In one implementation, the transceiver unit 730 is further configured to receive status report information for a data packet transmitted by the second terminal device, the status report information for the data packet indicating to the second access network device a data packet that was successfully received by the terminal device and a data packet that was not successfully received by the terminal device; and send fourth indication information to the first access network device based on the status report information, the fourth indication information indicating a sequence number of a first data packet forwarded by the first access network device to the second access network device.

[0213] In one implementation, the transceiver unit 730 is further configured to send fifth instruction information to the first access network device, where the fifth instruction information includes a second sequence number N, and the second sequence number indicates a sequence number of a first data packet belonging to the first service to be sent by the second access network device to the second terminal device after handover of the second terminal device is completed.

[0214] If the apparatus 700 is configured in or is a second access network device, the modules or units in the apparatus 700 may be configured to perform the operations or processing steps performed by the second access network device in the manner described above. To avoid repetition, detailed descriptions are omitted here.

[0215] In some embodiments, the apparatus 700 may be a core network device or a chip or circuit disposed in a core network device. When the apparatus 700 is a core network device or a chip or circuit disposed in a core network device, the transceiver unit 730 is configured to receive a first packet transmitted by the data server, the transceiver unit 730 is configured to transmit a second data packet and first indication information to the first access network device, the first indication information indicating a sequence of the second data packets in the at least one data packet transmitted by the core network device, and the transceiver unit 730 is configured to transmit a third data packet and the second indication information to the second access network device, the second indication information indicating a sequence of the third data packets in the at least one data packet transmitted by the core network device, and the data in the second data packet and the data in the third data packet are the same as the data in the first data packet.

[0216] In one implementation, the first indication information includes at least one of the following information: a General Packet Radio Service Tunneling Protocol-User Plane GTP-U sequence number and a first service sequence number, where the first service sequence number is set by a core network device or a data server, the first data packet is a data packet of the first service, and at least one data packet is a data packet of the first service.

[0217] If the apparatus 700 is configured in or is a core network device, the modules or units in the apparatus 700 may be configured to perform the operations or processing steps performed by the core network device in the manner described above. To avoid repetition, detailed descriptions are omitted here.

[0218] For the concept, description, detailed explanation and other steps of the device 700 related to the technical solutions provided in the embodiments of the present application, please refer to the description of the content of the aforementioned methods or other embodiments, and the details will not be repeated here.

[0219] 9 is a schematic diagram of the structure of a terminal device 800 according to the present application. The terminal device 800 may perform the operations performed by the terminal device in the above-described method embodiments.

[0220] For ease of explanation, Fig. 9 shows only the main components of the terminal device. As shown in Fig. 9, the terminal device 800 includes a processor, a memory, a control circuit, an antenna, and an input / output device.

[0221] The processor is primarily configured to process communication protocols and communication data, control the entire terminal device, execute software programs, and process data from the software programs, for example, to support the terminal device in performing the operations described in the above-described embodiments of the transmission precoding matrix instruction method. The memory is primarily configured to store software programs and data, for example, to store the codebook described in the above-described embodiments. The control circuit is primarily configured to convert baseband signals and radio frequency signals and process radio frequency signals. The combination of the control circuit and the antenna may also be referred to as a transceiver, which is primarily configured to transmit and receive radio frequency signals in the form of electromagnetic waves. The input / output device, for example, a touch screen, a display, or a keyboard, is primarily configured to receive data input by a user and output data to the user.

[0222] After the terminal device is powered on, the processor can read the software program in the storage unit, interpret and execute the instructions of the software program, and process the data of the software program. When data needs to be transmitted wirelessly, the processor performs baseband processing on the data to be transmitted and then outputs a baseband signal to the radio frequency circuit. The radio frequency circuit performs radio frequency processing on the baseband signal and then transmits the radio frequency signal in the form of an electromagnetic wave via the antenna. When data is to be transmitted to the terminal device, the radio frequency circuit receives the radio frequency signal via the antenna, converts the radio frequency signal into a baseband signal, and outputs the baseband signal to the processor. The processor converts the baseband signal into data and processes the data.

[0223] Those skilled in the art will understand that for ease of explanation, Figure 9 shows only one memory and one processor. In an actual terminal device, there may be multiple processors and memories. The memory may also be referred to as a storage medium, a storage device, or the like. This is not limited to the embodiments of the present application.

[0224] For example, the processor may include a baseband processor and a central processing unit. The baseband processor is primarily configured to process communication protocols and communication data. The central processing unit is primarily configured to control the entire terminal device, execute software programs, and process data from the software programs. The functions of the baseband processor and the central processing unit are integrated into the processor in FIG. 9. Those skilled in the art will understand that the baseband processor and the central processing unit may each be independent processors and interconnected using technology such as a bus. Those skilled in the art will understand that a terminal device may include multiple baseband processors to accommodate different network standards, multiple central processing units to improve the processing capabilities of the terminal device, and the components of the terminal device may be connected using various buses. Alternatively, the baseband processor may be expressed as a baseband processing circuit or a baseband processing chip. Alternatively, the central processing unit may be expressed as a central processing circuit or a central processing chip. The function of processing communication protocols and communication data may be incorporated into the processor or stored in a storage unit in the form of a software program. The processor executes the software program to perform the baseband processing function.

[0225] For example, in this embodiment of the present application, an antenna and a control circuit having receiving and transmitting functions may be considered as a transceiver unit 810 of the terminal device 800, and a processor having processing functions may be considered as a processing unit 820 of the terminal device 800. As shown in FIG. 9 , the terminal device 800 includes a transceiver unit 810 and a processing unit 820. The transceiver unit may also be referred to as a transceiver, a transceiver, a transceiver device, etc. Optionally, a component within the transceiver unit 810 configured to implement the receiving function may be considered as a receiving unit, and a component within the transceiver unit 810 configured to implement the transmitting function may be considered as a transmitting unit. That is, the transceiver unit includes a receiving unit and a transmitting unit. For example, the receiving unit may also be referred to as a receiver, a receiver, or a receiving circuit, and the transmitting unit may also be referred to as a transmitter, a transmitter, or a transmitting circuit.

[0226] 10 is a schematic diagram of the structure of an access network device 900 according to one embodiment of the present application. The access network device 900 may be configured to perform the functions of an access device (e.g., a first access network device, a second access network device, or a third access network device) in the aforementioned method. The access network device 900 includes one or more radio frequency units, such as a remote radio unit (RRU) 910, and one or more baseband units (BBUs) 920 (which may also be referred to as digital units (DUs)). The RRU 910 may also be referred to as a transceiver unit, transceiver, transceiver circuit, transceiver, etc., and may include at least one antenna 911 and a radio frequency unit 912. The RRU 910 is mainly configured to transmit and receive radio frequency signals and perform conversion between radio frequency signals and baseband signals, for example, to transmit signaling messages in the aforementioned embodiments to terminal devices. The BBU 920 is mainly configured to perform baseband processing, control the base station, etc. The RRU 910 and the BBU 920 may be physically co-located or physically separated, i.e., located in distributed base stations.

[0227] The BBU 920 is a control center of the base station, and may also be called a processing unit, and is mainly configured to perform baseband processing functions such as channel coding, multiplexing, modulation, or spreading, etc. For example, the BBU (processing unit) 920 may be configured to control the base station 40 to perform operation procedures related to the network devices of the above-mentioned method embodiments.

[0228] In one example, the BBU 920 may include one or more boards, and the multiple boards may jointly support a radio access network of a single access standard (e.g., an LTE system or a 5G system) or separately support radio access networks of different access standards. The BBU 920 further includes a memory 921 and a processor 922. The memory 921 is configured to store necessary instructions and data. For example, the memory 921 stores a codebook in the aforementioned embodiments. The processor 922 is configured to control the base station to perform necessary operations, for example, to control the base station to perform operation procedures related to the network device in the aforementioned method embodiments. The memory 921 and the processor 922 may provide services to one or more boards. In other words, the memory and the processor may be separately located on each board. Alternatively, the multiple boards may share the same memory and the same processor. In addition, necessary circuits may be further located on each board.

[0229] In a possible implementation, with the development of system-on-chip (SoC) technology, all or part of the functions of components 920 and 910 may be implemented using SoC technology, for example, using a single base station function chip. The base station function chip integrates components such as a processor, memory, and antenna ports. The memory stores programs for base station-related functions, and the processor executes the programs to realize the base station-related functions. Optionally, the base station function chip can also read its external memory to perform the base station-related functions.

[0230] It should be understood that the structure of the access network device shown in Figure 10 is only a possible form and should not constitute any limitation on the embodiments of the present application. The present application does not exclude the possibility that other forms of base station structures may appear in the future.

[0231] It should be understood that the processor in the embodiments of the present application may be a central processing unit (CPU). The processor may alternatively be another general-purpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device, a discrete gate or transistor logic device, or a discrete hardware component. The general-purpose processor may be a microprocessor, or the processor may be any conventional processor, or the like.

[0232] It should be further understood that the memory of the embodiments of the present application may be volatile or non-volatile memory, or may include volatile and non-volatile memory. Non-volatile memory may be read-only memory (ROM), programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), or flash memory. Volatile memory may be random access memory (RAM) used as an external cache. By way of example and not limitation, many forms of random access memory (RAM) may be used, such as static random access memory (SRAM), dynamic random access memory (DRAM), synchronous dynamic random access memory (SDRAM), double data rate synchronous dynamic random access memory (DDR SDRAM), enhanced synchronous dynamic random access memory (ESDRAM), synchlink dynamic random access memory (SLDRAM), and direct rambus random access memory (DR RAM).

[0233] All or part of the above embodiments may be implemented using software, hardware, firmware, or any combination thereof. When software is used to implement the embodiments, the aforementioned embodiments may be implemented, entirely or partially, in the form of a computer program product. The computer program product includes one or more computer instructions or computer programs. When the computer instructions or computer programs are loaded into a computer and executed, the procedures or functions according to the embodiments of the present application are generated, entirely or partially. 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 on a computer-readable storage medium or transmitted from a computer-readable storage medium to another computer-readable storage medium. For example, the computer instructions may be transmitted from a website, computer, server, or data center to another website, computer, server, or data center via a wired (e.g., infrared, radio, or microwave) method. The computer-readable storage medium may be any available medium accessible by a computer, or a data storage device, such as a server or data center, that integrates one or more available media. The available media may be magnetic media (e.g., floppy disks, hard disks, or magnetic tapes), optical media (e.g., DVDs), or semiconductor media, which may be solid-state drives.

[0234] An embodiment of the present application further provides a computer-readable medium, which stores a computer program, which, when executed by a computer, performs steps performed by a terminal device, a first access network device, a second access network device, or a core network device according to any one of the preceding embodiments.

[0235] An embodiment of the present application further provides a computer program product, which, when run by a computer, performs steps performed by a terminal device, a first access network device, a second access network device, or a core network device according to any one of the preceding embodiments.

[0236] An embodiment of the present application further provides a system-on-chip. The system-on-chip includes a communication unit and a processing unit. The processing unit may be, for example, a processor. The communication unit may be, for example, a communication interface, an input / output interface, a pin, a circuit, etc. The processing unit may execute computer instructions such that the chip in the communication device performs the steps performed by the terminal device, the steps performed by the first access network device, the steps performed by the second access network device, and the steps performed by the core network device provided in the foregoing embodiments of the present application.

[0237] Optionally, the computer instructions are stored in a storage unit.

[0238] According to the method provided in the embodiment of the present application, an embodiment of the present application further provides a communication system including the above-mentioned first access network device, the above-mentioned second access network device, the above-mentioned core network device, and the above-mentioned terminal device.

[0239] The embodiments of the present application may be used independently or together, which is not limited herein.

[0240] Additionally, aspects or features of the present application may be implemented as a method, apparatus, or article of manufacture using standard programming and / or engineering techniques. The term "article of manufacture" as used herein encompasses a computer program accessible from any computer-readable component, carrier, or medium. For example, computer-readable media may include, but are not limited to, magnetic storage components (e.g., hard disks, floppy disks, or magnetic tapes), optical disks (e.g., compact discs (CDs) and digital versatile discs (DVDs)), smart cards, and flash memory components (e.g., erasable programmable read-only memory (EPROM), cards, sticks, or key drives). Additionally, various storage media described herein may refer to one or more devices and / or other machine-readable media configured to store information. The term "machine-readable medium" may include, but is not limited to, wireless channels and various other media capable of storing, containing, and / or conveying instructions and / or data.

[0241] It should be understood that the term "and / or" describes an association relationship between associated objects and indicates that three relationships may exist. For example, A and / or B may represent three cases: when only A is present, when both A and B are present, and when only B is present. The symbol " / " generally indicates an "or" relationship between associated objects. "At least one" means one or more. "At least one of A and B," similar to "A and / or B," describes an association relationship between associated objects and indicates that three relationships may exist. For example, "at least one of A and B" may represent three cases: when only A is present, when both A and B are present, and when only B is present.

[0242] Those skilled in the art may recognize that, in combination with the examples described in the embodiments disclosed herein, the units and algorithm steps may be implemented by electronic hardware or a combination of computer software and electronic hardware. Whether a function is performed by hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art may use different methods to implement the described functions for each specific application, but the implementation form should not be considered to exceed the scope of this application.

[0243] For ease of explanation, those skilled in the art will clearly understand that the detailed operation processes of the above-mentioned systems, devices and units may refer to the corresponding processes in the above-mentioned method embodiments, and the details will not be repeated here.

[0244] In some embodiments provided in the present application, it should be understood that the disclosed system, device, and method may be implemented in other ways. For example, the device embodiments described above are merely examples. For example, the division into units is merely a logical division of function, and other divisions may be used in actual implementation. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not implemented. In addition, the shown or described interconnections, direct connections, or communication connections may be implemented by using some interfaces. Indirect couplings or communication connections between devices or units may be implemented in electrical, mechanical, or other forms.

[0245] The units described as separate parts may or may not be physically separated, and the parts shown as units may or may not be physical units, i.e., they may be located in one place or distributed across multiple network units. Some or all of the units may be selected based on actual requirements to achieve the objectives of the solutions of the embodiments.

[0246] In addition, the functional units in the embodiments of the present application may be integrated into one processing unit, or each of the units may exist physically alone, or two or more units may be integrated into one unit.

[0247] When a function is implemented in the form of a software functional unit and sold or used as an independent product, the function may be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present application, or a portion of the technical solution, may be essentially implemented in the form of a software product, or a portion of the technical solution. A computer software product is stored in a storage medium and includes instructions for instructing a computer device (which may be a personal computer, a server, or a network device) to perform all or part of the steps of the method of the embodiments of the present application. The aforementioned storage medium includes any medium capable of storing program code, such as a USB flash drive, a removable hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk, or an optical disk.

[0248] The above description is merely a specific implementation form of the present application, and the protection scope of the present application is not limited thereto. Any modifications or replacements that can be easily conceived by those skilled in the art within the technical scope disclosed in the present application shall fall within the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims. [Explanation of symbols]

[0249] 100 Application Scenarios 110 Access Network Devices 120,130,140,150,160,170 terminal devices 400 Multicast Service Handover Scenarios 410 Core Network Devices 420,430 Access Network Devices 440,450,460 terminal devices 700 Communication Equipment 710 Processing Unit 720 Storage Unit 730 Transceiver Unit 800 Terminal Devices 810 Transceiver Unit 820 Processing Unit 900 Access Network Devices 910 Remote Radio Unit (RRU) 911 antenna 912 Radio Frequency Unit 920 Baseband Unit (BBU) 921 memory 922 processor

Claims

1. A communication method applied to a first access network device, comprising: receiving a first data packet and first indication information from a core network device, the first indication information indicating a sequence of the first data packet in at least one data packet; determining a first sequence number of a first protocol layer of the first data packet based on the first indication; transmitting the first data packet to a terminal device; A method comprising:

2. The first indication information is the following information: General Packet Radio Service Tunneling Protocol-User Plane (GTP-U) sequence number and first service sequence number and The method of claim 1 , wherein the first service sequence number is set by the core network device or a data server, and the at least one data packet is a data packet of a first service.

3. the first protocol layer Service Data Adaptation Protocol (SDAP) layer, Packet Data Convergence Protocol (PDCP) layer, and Radio Link Control (RLC) layer 3. The method of claim 1 or 2, comprising at least one of:

4. setting a starting sequence number of the first protocol layer of the first data packet based on the first indication information when any one of establishment of a first protocol entity, re-establishment of the first protocol entity, and recovery of the first protocol entity occurs.

4. The method of claim 1, further comprising:

5. sending second indication information to the terminal device, the second indication information indicating a sequence number of a first data packet belonging to a first service to be sent by the first access network device to the terminal device after a first protocol entity is established, after the first protocol entity is re-established, or after the first protocol entity is recovered; 5. The method of claim 1, further comprising:

6. receiving third instruction information from a second access network device, the third instruction information instructing the first access network device to stop forwarding data packets to the second access network device; stopping forwarding of the data packet to the second access network device based on the third instruction information; 6. The method of claim 1, further comprising:

7. receiving fourth indication information sent by the second access network device, the fourth indication information indicating a sequence number of a first data packet forwarded by the first access network device to the second access network device; forwarding the data packet to the second access network device based on the fourth indication information; 7. The method of claim 6, further comprising:

8. receiving fifth indication information sent by a second access network device, the fifth indication information including a second sequence number N, the second sequence number indicating a sequence number of a first data packet of a first service sent by the second access network device to the terminal device after handover of the terminal device is completed; If the sequence number of the data packet successfully transmitted by the first access network device to the terminal device is N-1, stopping the first access network device from transmitting data packets to the terminal device; 6. The method of claim 1, further comprising:

9. A communication method applied to a terminal device, comprising: receiving second indication information sent by a first access network device, the second indication information indicating a sequence number of a first data packet belonging to a first service to be sent by the first access network device to the terminal device after a first protocol entity is established, after the first protocol entity is re-established, or after the first protocol entity is restored; A method comprising:

10. sending request information to the first access network device when the first protocol entity is re-established or restored, the request information requesting the first access network device to transmit the sequence number of the first data packet of the first service to be transmitted by the first access network device to the terminal device after the first protocol entity is re-established or restored; 10. The method of claim 9, further comprising:

11. sending status report information of data packets to a second access network device, wherein the status report information of the data packets indicates to the second access network device data packets that were successfully received by the terminal device and data packets that were not successfully received by the terminal device, and the terminal device is handed over from the first access network device to the second access network device; 11. The method of claim 9 or 10, further comprising:

12. A communication method applied to a second access network device, comprising: receiving a first data packet and first indication information from a core network device, the first indication information indicating a sequence of the first data packet in at least one data packet; determining a second sequence number of a first protocol layer of the first data packet based on the first indication; transmitting the first data packet to a first terminal device; A method comprising:

13. The first indication information is the following information: General Packet Radio Service Tunneling Protocol-User Plane (GTP-U) sequence number and first service sequence number and 13. The method of claim 12, wherein the first service sequence number is set by the core network device or a data server, the first data packet is a data packet of a first service, and the at least one data packet is a data packet of the first service.

14. the first protocol layer Service Data Adaptation Protocol (SDAP) layer, Packet Data Convergence Protocol (PDCP) layer, and Radio Link Control (RLC) layer 14. The method of claim 12 or 13, comprising at least one of:

15. determining a starting sequence number of the first protocol layer of the first data packet based on the first indication information when any one of establishment of a first protocol entity, re-establishment of the first protocol entity, and recovery of the first protocol entity occurs; 15. The method of any one of claims 12 to 14, further comprising:

16. sending second indication information to the terminal device, the second indication information indicating a sequence number of a first data packet belonging to a first service to be sent by a first access network device to the terminal device after a first protocol entity is established, after the first protocol entity is re-established, or after the first protocol entity is recovered; 16. The method of any one of claims 12 to 15, further comprising:

17. receiving a data packet from a first access network device, wherein a second terminal device connected to the first access network device is handed over from the first access network device to the second access network device, both the first terminal device and the second terminal device are running a first service, and the data packet sent by the first access network device is a data packet of the first service; sending third instruction information to the first access network device if a second sequence number of a first protocol layer of the data packet being sent to the first terminal device is greater than or equal to a first sequence number of a first protocol layer of the data packet sent by the first access network device, the third instruction information instructing the first access network device to stop forwarding data packets to the second access network device; 16. The method of any one of claims 12 to 15, further comprising:

18. receiving status report information of data packets transmitted by the second terminal device, the status report information of the data packets indicating to the second access network device data packets that were successfully received by the terminal device and data packets that were not successfully received by the terminal device; sending fourth indication information to the first access network device based on the status report information, the fourth indication information indicating a sequence number of a first data packet forwarded by the first access network device to the second access network device; 18. The method of claim 17, further comprising:

19. sending fifth indication information to the first access network device, the fifth indication information including a second sequence number N, the second sequence number indicating a sequence number of a first data packet belonging to a first service to be sent by the second access network device to the second terminal device after handover of the second terminal device is completed; 16. The method of any one of claims 12 to 15, further comprising:

20. A communication method applied to a core network device, comprising: receiving a first data packet from a data server; sending a second data packet and first indication information to a first access network device, the first indication information indicating a sequence of the second data packet in at least one data packet transmitted by the core network device; sending a third data packet and second indication information to a second access network device, the second indication information indicating a sequence of the third data packet in the at least one data packet transmitted by the core network device, and data in the second data packet and data in the third data packet being the same as data in the first data packet; A method comprising:

21. The first indication information is the following information: General Packet Radio Service Tunneling Protocol-User Plane (GTP-U) sequence number and first service sequence number and 21. The method of claim 20, wherein the first service sequence number is set by the core network device or the data server, the first data packet is a data packet of a first service, and the at least one data packet is a data packet of the first service.

22. an access network device, the access network device being a first access network device; a transceiver unit configured to receive a first data packet and first indication information from a core network device, the first indication information indicating a sequence of the first data packet in at least one data packet; a processing unit configured to determine a first sequence number of a first protocol layer of the first data packet based on the first indication; Equipped with The access network device, wherein the transceiver unit is further configured to transmit the first data packet to a terminal device.

23. The first indication information is the following information: General Packet Radio Service Tunneling Protocol-User Plane (GTP-U) sequence number and first service sequence number and 23. The access network device of claim 22, wherein the first service sequence number is set by the core network device or a data server, the first data packet is a data packet of a first service, and the at least one data packet is a data packet of the first service.

24. the first protocol layer Service Data Adaptation Protocol (SDAP) layer, Packet Data Convergence Protocol (PDCP) layer, and Radio Link Control (RLC) layer 24. The access network device of claim 22 or 23, comprising at least one of:

25. The processing unit determining a starting sequence number of the first protocol layer of the first data packet based on the first indication information when any one of establishment of a first protocol entity, re-establishment of the first protocol entity, and recovery of the first protocol entity occurs; 25. The access network device of claim 22, further configured to:

26. the transceiver unit: sending second indication information to the terminal device, the second indication information indicating a sequence number of a first data packet belonging to a first service to be sent by the first access network device to the terminal device after a first protocol entity is established, after the first protocol entity is re-established, or after the first protocol entity is recovered; 26. The access network device of claim 22, further configured to:

27. the transceiver unit: receiving third instruction information from a second access network device, the third instruction information instructing the first access network device to stop forwarding data packets to the second access network device; further configured as follows: The processing unit Stopping forwarding of the data packet to the second access network device based on the third instruction information.

27. The access network device of claim 22, further configured to:

28. the transceiver unit: receiving fourth indication information sent by the second access network device, the fourth indication information indicating a sequence number of a first data packet forwarded by the first access network device to the second access network device; further configured as follows: The processing unit forwarding the data packet to the second access network device based on the fourth indication information; 28. The access network device of claim 27, further configured to:

29. the transceiver unit: receiving fifth indication information sent by a second access network device, the fifth indication information including a second sequence number N, the second sequence number indicating a sequence number of a first data packet of a first service sent by the second access network device to the terminal device after handover of the terminal device is completed; further configured as follows: The processing unit determining to stop sending data packets to the terminal device if the protocol layer sequence number of the data packet successfully sent by the first access network device to the terminal device is N-1; 27. The access network device of claim 22, further configured to:

30. A terminal device, a transceiver unit configured to receive second indication information transmitted by a first access network device, the second indication information indicating a sequence number of a first data packet of a first service to be transmitted by the first access network device to the terminal device after a first protocol entity is established, after the first protocol entity is re-established, or after the first protocol entity is restored; A terminal device comprising:

31. the transceiver unit: sending request information to the first access network device when the first protocol entity is re-established or restored, the request information requesting the first access network device to transmit the sequence number of the first data packet belonging to the first service to be transmitted by the first access network device to the terminal device after the first protocol entity is re-established or restored; 31. The terminal device of claim 30, further configured to:

32. the transceiver unit: sending status report information of the data packets to a second access network device, the status report information of the data packets indicating to the second access network device the data packets that were successfully received by the terminal device and the data packets that were not successfully received by the terminal device, and the terminal device is handed over from the first access network device to the second access network device; 32. The terminal device of claim 30 or 31, further configured to:

33. an access network device, the access network device being a second access network device; a transceiver unit configured to receive a first data packet and first indication information from a core network device, the first indication information indicating a sequence of the first data packet in at least one data packet; a processing unit configured to determine a second sequence number of a first protocol layer of the first data packet based on the first indication; Equipped with The access network device, wherein the transceiver unit is further configured to transmit the first data packet to a first terminal device.

34. The first indication information is the following information: General Packet Radio Service Tunneling Protocol-User Plane (GTP-U) sequence number and first service sequence number and 34. The access network device of claim 33, wherein the first service sequence number is set by the core network device or a data server, the first data packet is a data packet of a first service, and the at least one data packet is a data packet of the first service.

35. the first protocol layer Service Data Adaptation Protocol (SDAP) layer, Packet Data Convergence Protocol (PDCP) layer, and Radio Link Control (RLC) layer 35. The access network device of claim 33 or 34, comprising at least one of:

36. The processing unit determining a starting sequence number of the first protocol layer of the first data packet based on the first indication information when any one of establishment of a first protocol entity, re-establishment of the first protocol entity, and recovery of the first protocol entity occurs; 36. The access network device of any one of claims 33 to 35, further configured to:

37. the transceiver unit: sending second indication information to the terminal device, the second indication information indicating a sequence number of a first data packet belonging to the first service to be sent by the first access network device to the terminal device after a first protocol entity is established, after the first protocol entity is re-established, or after the first protocol entity is recovered; 37. The access network device of any one of claims 33 to 36, further configured to:

38. the transceiver unit: receiving a data packet transmitted by a first access network device, a second terminal device connected to the first access network device being handed over from the first access network device to the second access network device, both the first terminal device and the second terminal device running a first service, and the data packet transmitted by the first access network device being a data packet of the first service; If a second sequence number of a first protocol layer of the data packet being transmitted to the first terminal device is greater than or equal to a first sequence number of the first protocol layer of the data packet transmitted by the first access network device, sending third instruction information to the first access network device, the third instruction information instructing the first access network device to stop forwarding the data packet to the second access network device; 38. The access network device of any one of claims 33 to 37, further configured to:

39. the transceiver unit: receiving status report information for data packets transmitted by the second terminal device, the status report information for the data packets indicating to the second access network device data packets successfully received by the terminal device and data packets not successfully received by the terminal device; sending fourth indication information to the first access network device based on the status report information, the fourth indication information indicating a sequence number of a first data packet forwarded by the first access network device to the second access network device; 40. The access network device of claim 38, further configured to:

40. the transceiver unit: sending fifth instruction information to the first access network device, the fifth instruction information including a second sequence number N, the second sequence number indicating a sequence number of a first data packet belonging to the first service to be sent by the second access network device to the second terminal device after handover of the second terminal device is completed; 37. The access network device of any one of claims 33 to 36, further configured to:

41. A core network device, comprising: a transceiver unit configured to receive a first data packet transmitted by a data server; Equipped with the transceiver unit is further configured to transmit a second data packet and first indication information to a first access network device, the first indication information indicating a sequence of the second data packet in at least one data packet transmitted by the core network device; The core network device is further configured such that the transceiver unit transmits a third data packet and second instruction information to a second access network device, the second instruction information indicating the sequence of the third data packet in the at least one data packet transmitted by the core network device, and the data in the second data packet and the data in the third data packet are the same as the data in the first data packet.

42. The first indication information is the following information: General Packet Radio Service Tunneling Protocol-User Plane (GTP-U) sequence number and first service sequence number and 42. The core network device of claim 41, wherein the first service sequence number is set by the core network device or the data server, the first data packet is a data packet of a first service, and the at least one data packet is a data packet of the first service.

43. 20. A communications device comprising a processor, the processor connected to a memory, the memory configured to store a computer program, the processor configured to execute the computer program stored in the memory to enable the communications device to perform the method of any one of claims 1 to 8, the method of any one of claims 9 to 11, the method of any one of claims 12 to 19, or the method of claim 20 or 21.

44. 13. A computer-readable storage medium having stored thereon a computer program that, when executed, performs the method of any one of claims 1 to 8, the method of any one of claims 9 to 11, the method of any one of claims 12 to 19, or the method of claim 20 or 21.

45. A chip including a processor and an interface, the processor being configured to read instructions and to perform the data transmission method of any one of claims 1 to 8, the method of any one of claims 9 to 11, the method of any one of claims 12 to 19, or the method of claim 20 or 21.

46. A communication device according to any one of claims 22 to 29; A communication device according to any one of claims 30 to 32; A communication device according to any one of claims 33 to 40; A communication device according to claim 40 or 41. A communication system comprising:

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