Communication methods, access network devices, terminal devices, and core network devices

Abstract

The present application provides a communication method, an access network device, a terminal device, and a core network device. During a process in which a terminal device is handed over from a first access network device to a second access network device, the second access network device can learn a first service progress of the first access network device based on a first sequence number of a data packet forwarded by the first access network device without introducing additional progress exchange information between the two access network devices. The method includes: receiving, by the first access network device, a first data packet and first indication information from a core network device, where the first indication information indicates 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 the terminal device.

Description

Technical Field

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

[0002] This application relates to the field of communications, and more specifically, to communication methods, access network devices, terminal devices, and core network devices.

Background Art

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

[0004] When MBMS services are moved from a source access network device to a target access network device, the terminal device must continue to receive the MBMS services it initially received from the source access network device after being handed over to the target access network device in order to continue receiving MBMS services. However, the progress of MBMS services sent by the two access network devices may not be consistent, and because the source access network device and the target access network device are independent of each other when determining the sequence number of the MBMS service data packets, the source access network device and the target access network device may have inconsistent understanding of the sequence number of the MBMS service data packets during the terminal device handover process. As a result, when a handover occurs, the terminal device may either interrupt its reception of MBMS services or receive redundant data packets. Therefore, the continuity of MBMS services cannot be guaranteed. [Overview of the project] [Means for solving the problem]

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

[0006] According to the first embodiment, a communication method is provided. This method is applied to a first access network device, The process includes: receiving a first data packet and first instruction information from a core network device, wherein the first instruction information indicates a sequence of the first data packet in at least one data packet; determining a first sequence number of the first protocol layer of the first data packet based on the first instruction information; and transmitting the first data packet to a terminal device.

[0007] Therefore, in the process of handing over a terminal device 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 packets transferred by the first access network device, without introducing additional progress exchange information between the two access network devices.

[0008] Referring to the first embodiment, in some implementations of the first embodiment, the first instruction information includes at least one of the following information: a general-purpose packet radio service tunneling protocol user plane GTP-U sequence number and a first service sequence number, the first service sequence number being set by a core network device or data server, the first data packet being a data packet of the first service, and at least one data packet being a data packet of the first service.

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

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

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

[0012] Referring to the first embodiment, in some implementations of the first embodiment, the method further includes the step of transmitting second instruction information to a terminal device, the second instruction information indicating the sequence number of the first data packet which is of the first service and is transmitted to the terminal device by a first access network device after the first protocol entity has been established, after the first protocol entity has been re-established, or after the first protocol entity has been recovered.

[0013] Therefore, the terminal device can determine the start sequence number of the first protocol layer of the first received data packet based on the second instruction 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 embodiment, in some implementations of the first embodiment, the method further includes the steps of: 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; and stopping forwarding data packets to the second access network device based on the third instruction information.

[0015] Therefore, during the handover process of the first terminal device, the second access network device determines whether data transfer of the first access network device may be stopped, and sends data transfer stop instruction information to the first access network device. As a result, the continuity of multicast service reception for the terminal device during the handover process is guaranteed, and packet loss or redundant transmission is avoided.

[0016] Referring to the first embodiment, in some implementations of the first embodiment, the method further includes the steps of: receiving fourth instruction information transmitted by a second access network device, wherein the fourth instruction information indicates the sequence number of the 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 instruction information indicates the sequence number of the first protocol layer of the initial data packet not yet received by the first terminal device, i.e., the initiating data packet in the data transfer 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, 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.

[0018] Referring to the first embodiment, in some implementations of the first embodiment, the method further includes the step of receiving fifth instruction information transmitted by a second access network device, the fifth instruction information comprising a second sequence number N, the second sequence number indicating the sequence number of the first data packet which is of the first service and is transmitted to the terminal device by the second access network device after the handover of the terminal device is complete. If the sequence number which is of the protocol layer and corresponds to a data packet successfully transmitted to the terminal device by the first access network device is N-1, the first access network device stops transmitting data packets to the terminal device.

[0019] Therefore, in the handover process, the first access network device determines when to terminate its connection to the terminal device based on the SN indicated by the second access network device, thereby ensuring the continuity of multicast service reception for the terminal device during the handover process and avoiding packet loss or redundant transmission.

[0020] Referring to the first embodiment, in some implementations of the first embodiment, the first access network device sends stop instruction information to the second access network device instructing the first access network device to disconnect from the first terminal device.

[0021] Referring to the first embodiment, in some implementations of the first embodiment, the second access network device transmits a fifth instruction to the first access network device, the fifth instruction includes a second sequence number N-1, the second sequence number instructing the first access network device to stop transmitting data packets to the terminal device if the first protocol layer sequence number of a data packet successfully transmitted to the terminal device by the first access network 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 a data packet with a first sequence number of N-1 has been sent.

[0023] A second aspect provides a communication method, which is applied to a terminal device and includes the steps of receiving second instruction information from a first access network device, the second instruction information indicating the sequence number of the first data packet which is a first service and is sent to the terminal device by the first access network device after the first protocol entity is established, after the first protocol entity is re-established, or after the first protocol entity is recovered.

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

[0025] Referring to the second aspect, in some implementations of the second aspect, the method further includes the step of transmitting data packet status report information to a second access network device, the data packet status report information indicating to the second access network device which data packets were successfully received by the terminal device and which data packets 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.

[0026] A third aspect provides a communication method, which is applied to a second access network device and includes the steps of: receiving a first data packet and first instruction information from a core network device, wherein the first instruction information indicates a sequence of the first data packets in at least one data packet; determining a second sequence number of the first protocol layer of the first data packet based on the first instruction 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 instruction information includes at least one of the following information, that is, the General Packet Radio Service Tunneling Protocol user plane GTP-U sequence number and the 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 at least one data packet is a data packet of the first service.

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

[0029] Referring to the third aspect, in some implementation forms of the third aspect, the method further includes the step of setting the start sequence number of the first protocol layer of the first data packet based on the first instruction information 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.

[0030] Referring to the third aspect, in some implementation forms of the third aspect, the method further includes the step of transmitting second instruction information to the terminal device. The second instruction information indicates the sequence number of the first data packet of the first service that is transmitted to the terminal device by the first access network 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 a third aspect, in some implementations 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 a second access network device, both the first and second terminal devices perform a first service, and the data packet transmitted by the first access network device is a data packet of the first service; and, if the second sequence number of the 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, transmitting a 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.

[0032] Referring to the third aspect, in some implementations of the third aspect, the method further includes: receiving data packet status report information from a second terminal device, wherein the data packet status report information indicates to the second access network device which data packets were successfully received by the terminal device and which were not successfully received by the terminal device; and transmitting a fourth instruction information to a first access network device based on the status report information, wherein the fourth instruction information indicates the sequence number of the first data packet transferred by the first access network device to the second access network device.

[0033] Referring to the third aspect, in some implementations of the third aspect, the method further includes the step of transmitting fifth instruction information to a first access network device, the fifth instruction information comprising a second sequence number N, the second sequence number indicating the sequence number of the first data packet which is of the first service and is transmitted to the second terminal device by the second access network device after the handover of the second terminal device is complete.

[0034] A fourth aspect provides a communication method, which is applied to a core network device and includes the steps of: receiving a first data packet transmitted by a data server; transmitting a second data packet and first instruction information to a first access network device, wherein the first instruction information indicates a sequence of the second data packets in at least one data packet transmitted by the core network device; and transmitting a third data packet and second instruction information to a second access network device, wherein the second instruction information indicates a sequence of the third data packets in at least one data packet of 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.

[0035] Referring to the fourth aspect, in some implementations of the fourth aspect, the first instruction information includes at least one of the following information: a general-purpose packet radio service tunneling protocol user plane GTP-U sequence number and a first service sequence number, the first service sequence number being set by a core network device or data server, the first data packet being a data packet of the first service, and at least one data packet being a data packet of the first service.

[0036] According to a fifth aspect, an access network device is provided. The access network device may be a first access network device, a chip or module within the first access network device, or a chip or system-on-a-chip. The access network device includes a transceiver unit configured to receive a first data packet and first instruction information from a core network device, wherein the first instruction information indicates 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 the first protocol layer of the first data packet based on the first instruction 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 implementations of the fifth aspect, the first instruction information includes at least one of the following information: a general-purpose packet radio service tunneling protocol user plane GTP-U sequence number and a first service sequence number, the first service sequence number being set by a core network device or data server, the first data packet being a data packet of a first service, and at least one data packet being a data packet of a first service.

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

[0039] Referring to the fifth aspect, in some implementations of the fifth aspect, the processing unit is further configured to determine the start sequence number of the first protocol layer of the first data packet based on the first instruction information when any one of the following occurs: establishment of the first protocol entity, re-establishment of the first protocol entity, and recovery of the first protocol entity.

[0040] Referring to the fifth aspect, in some implementations of the fifth aspect, the transceiver unit is further configured to transmit second instruction information to a terminal device, the second instruction information indicating the sequence number of the first data packet that is of the first service and is transmitted to the terminal device by the first access network device after the first protocol entity has been established, after the first protocol entity has been re-established, or after the first protocol entity has been recovered.

[0041] Referring to the fifth aspect, in some implementations of the fifth aspect, the transceiver unit is further configured to receive 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, 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 implementations of the fifth aspect, the transceiver unit is further configured to receive fourth instruction information transmitted by the second access network device, the fourth instruction information indicating the sequence number of the 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 implementations of the fifth aspect, the transceiver unit is further configured to receive fifth instruction information transmitted by a second access network device, the fifth instruction information includes a second sequence number N, where the second sequence number indicates the sequence number of the first data packet which is a first service and is sent to the terminal device by the second access network device after the handover of the terminal device is complete, and the processing unit is configured to decide to stop sending data packets to the terminal device if the sequence number which is a protocol layer and corresponds to the data packet successfully sent to the terminal device by the first access network device is N-1.

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

[0046] Referring to the sixth aspect, in some implementations of the sixth aspect, the transceiver unit is further configured to transmit data packet status report information to a second access network device, the data packet status report information indicating to the second access network device which data packets were successfully received by the terminal device and which 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.

[0047] According to a seventh aspect, an access network device is provided. The access network device may be a second access network device, a chip or module within the second access network device, or a chip or system-on-a-chip. The access network device includes a transceiver unit configured to receive a first data packet and first instruction information from a core network device, wherein the first instruction information indicates 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 the first protocol layer of the first data packet based on the first instruction information, wherein the transceiver unit is configured to transmit the first data packet to a first terminal device.

[0048] Referring to the seventh aspect, in some implementations of the seventh aspect, the first instruction information includes at least one of the following information: a general-purpose packet radio service tunneling protocol user plane GTP-U sequence number and a first service sequence number, the first service sequence number being set by a core network device or data server, the first data packet being a data packet of a first service, and at least one data packet being a data packet of a first service.

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

[0050] Referring to the seventh aspect, in some implementations of the seventh aspect, the processing unit is further configured to set the start sequence number of the first protocol layer of the first data packet based on the first instruction information when any one of the following occurs: establishment of the first protocol entity, re-establishment of the first protocol entity, and recovery of the first protocol entity.

[0051] Referring to the seventh aspect, in some implementations of the seventh aspect, the transceiver unit is further configured to transmit second instruction information to a terminal device, the second instruction information indicating the sequence number of the first data packet that is of the first service and is transmitted to the terminal device by the first access network device after the first protocol entity has been established, after the first protocol entity has been re-established, or after the first protocol entity has been recovered.

[0052] Referring to the seventh aspect, in some implementations of the seventh aspect, the transceiver unit is configured to receive a data packet transmitted by a first access network device, and if 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 and second terminal devices are performing a first service, and the data packet transmitted by the first access network device is a data packet of the first service, and the second sequence number of the 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 transmitted by the first access network device, then transmit a 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.

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

[0054] Referring to the seventh aspect, in some implementations of the seventh aspect, the transceiver unit is further configured to transmit fifth instruction information to a first access network device, the fifth instruction information comprising a second sequence number N, the second sequence number indicating the sequence number of the first data packet which is of the first service and is transmitted to the second terminal device by the second access network device after the handover of the second terminal device is complete.

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

[0056] Referring to the eighth aspect, in some implementations of the eighth aspect, the first instruction information includes at least one of the following information: a general-purpose packet radio service tunneling protocol user plane GTP-U sequence number and a first service sequence number, the first service sequence number being set by a core network device or data server, the first data packet being a data packet of the first service, and at least one data packet being a data packet of the first service.

[0057] According to the ninth aspect, a communication device is provided, the device including a processor. The processor is connected to memory. The memory is configured to store computer programs. The processor is configured to execute the computer programs stored in memory so that the device can perform a method according to any one of the first aspect or a possible implementation of the first aspect, a method according to any one of the second aspect or a possible implementation of the second aspect, a method according to any one of the third aspect or a possible implementation of the third aspect, or a method according to any one of the fourth aspect or a possible implementation of the fourth aspect.

[0058] According to the tenth aspect, a computer-readable storage medium is provided. The computer-readable storage medium stores a computer program. When the computer program is executed, a method according to the first aspect or any possible implementation of the first aspect, a method according to the second aspect or any possible implementation of the second aspect, a method according to the third aspect or any possible implementation of the third aspect, or a method according to the fourth aspect or any possible implementation of the fourth aspect is performed.

[0059] According to the eleventh aspect, a chip is provided, which includes a processor and an interface. The processor is configured to read instructions and execute a method according to any one of the first aspect or a possible implementation of the first aspect, a method according to any one of the second aspect or a possible implementation of the second aspect, a method according to any one of the third aspect or a possible implementation of the third aspect, or a method according to any one of the fourth aspect or a possible implementation of the fourth aspect.

[0060] Optionally, the chip may include additional memory. Memory stores instructions. The processor is configured to execute instructions stored in memory or other instructions.

[0061] According to the twelfth aspect, a communication system is provided. The system includes an apparatus having the function of implementing the method and possible design of the first aspect, an apparatus having the function of implementing the method and possible design of the second aspect, an apparatus having the function of implementing the method and possible design of the third aspect, and an apparatus having the function of implementing the method and possible design of the fourth aspect. [Brief explanation of the drawing]

[0062] [Figure 1] This is a schematic diagram of an application scenario according to one embodiment of this application. [Figure 2] This is a schematic flowchart of a communication method according to one embodiment of this application. [Figure 3] This is a schematic flowchart illustrating a method for handing over terminal devices between access network devices using conventional technology. [Figure 4] This is a schematic diagram illustrating an application scenario for a multicast service according to one embodiment of this application. [Figure 5] This is a schematic flowchart of a communication method according to one embodiment of this application. [Figure 6] This is a schematic flowchart of data transfer in a communication method according to one embodiment of this application. [Figure 7]This is a schematic flowchart of a communication method according to one embodiment of this application. [Figure 8] This is a schematic block diagram of a communication device according to one embodiment of the present application. [Figure 9] This is a schematic diagram of the structure of the terminal device according to this application. [Figure 10] This is a schematic diagram of the structure of the access network device according to this application. [Modes for carrying out the invention]

[0063] The technical solutions in this application will be described below with reference to the attached drawings.

[0064] To better understand this application, we will first explain the terms that may appear in the embodiments of this application.

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

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

[0067] A terminal device may be a wireless or wired terminal. A wireless terminal may refer to a device that provides connectivity for voice and / or other service data to a user, a handheld device with wireless connectivity, or other 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, and may be, for example, 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).Wireless terminals are also sometimes called systems, subscriber units, subscriber stations, mobile stations, mobile devices, remote stations, remote terminals, access terminals, user terminals, user agents, user devices or user equipment, mobile internet devices (MIDs), wearable devices, virtual reality (VR) devices, augmented reality (AR) devices, wireless terminals in industrial control, wireless terminals in self-driving, wireless terminals in remote medical surgery, wireless terminals in smart grids, wireless terminals in transportation safety, wireless terminals in smart cities, and wireless terminals in smart homes. They are also referred to as in-vehicle devices, wearable devices, terminal devices for 5G networks, and future advanced public land mobile networks (PLA). Examples include terminal devices of a network (PLMN), etc. This is not limited to the embodiments of this application.

[0068] For illustrative purposes only, and not as an limitation, in the embodiments of this application, wearable devices may also be called wearable intelligent devices, and are a general term for wearable devices such as glasses, gloves, watches, clothing, and shoes, which are developed based on intelligent designs to be worn daily by utilizing wearable technology. Wearable devices are portable devices that are worn directly or incorporated into the user's clothing or accessories. Wearable devices are not only hardware devices but also implement more powerful functionality through software support, data exchange, and cloud interaction. Typical wearable intelligent devices include full-featured, large devices that can implement full or partial functionality without relying on a smartphone, such as smartwatches or smart glasses, and devices that focus on only one type of application functionality and need to work in conjunction with other devices such as smartphones, such as various smart bands for monitoring bodily signs, or smart jewelry.

[0069] In addition, in the embodiments of this 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 the use of communication technology to connect things to a network in order to implement an intelligent network for interconnection between people and machines and between things.

[0070] When the various terminal devices described above are located inside a vehicle (for example, placed inside or mounted inside the vehicle), all of these terminal devices can be considered in-vehicle terminal devices. For example, in-vehicle terminal devices are also called on-board units (OBUs).

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

[0072] In embodiments of this application, the access network device may be a device configured to communicate with terminal devices, a base station, an access point, or a network device, or it may refer to a device that communicates with wireless terminals via an air interface in the access network using one or more sectors. The network device may be configured to convert received radio communication frames to and from IP packets and to act as a router between wireless terminals and the rest of the access network, the rest of the access network 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 of Mobile Communication (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, access point, in-vehicle device, wearable device, access device for a 5G network, or network device for a future evolved PLMN network, or a WLAN access point (AP), or a gNB in ​​a new radio (NR) system. This is not limited to the embodiments of this 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 this application may be used for each TRP and each terminal. In another scenario, the network device may be further divided into Control Units (CUs) and Data Units (DUs). One CU may correspond to multiple DUs. The measurement reporting method in the embodiments of this 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] In addition, in the embodiments of this application, the access network device is a device within an access network (radio access network, RAN), in other words, a RAN node that connects terminal devices to the radio network. For example, but not limited to, 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 node B or home node B, HNB), a base band unit (BBU), or a wireless fidelity (Wi-Fi) access point (access point, AP).

[0074] Access network devices provide services to cells. Terminal devices communicate with access network devices by using the transmission resources (e.g., frequency domain resources or spectral resources) available to the cell. A cell may be a cell corresponding to an access network device (e.g., a base station). A cell may belong to a macro base station or to 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 low coverage and low transmission power, making them suitable for providing high-speed data transmission services.

[0075] Unicast: A point-to-point communication technique, specifically single-point communication between a network device and a terminal device. The network device can transmit data separately to each terminal device. Unicast is sometimes also called unicast transmission mode or unicast transmission technique.

[0076] A transmission performed in unicast mode means that when a transport block (TB) corresponding to a protocol data unit (PDU) is transmitted, the transmitting device uses a cell network temporary identifier (C-RNTI) to scramble the PDU or the corresponding downlink control information (DCI), 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 over a radio bearer established for unicast transmission, or over a channel specifically designed for unicast.

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

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

[0079] Transmission performed in multicast transmission mode means that when a transport block (TB) corresponding to a protocol data unit (PDU) is transmitted, the transmitting device uses a group radio network temporary identifier (G-RNTI) to scramble the PDU or the downlink control information (DCI) corresponding to the PDU, 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-permanently notified of the location of the same PDU, and that multiple receiving devices can receive the PDU simultaneously. Alternatively, transmitting a PDU in multicast mode may mean that the PDU is transmitted over a radio bearer established for multicast transmission, or over a channel specifically designed for multicast.

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

[0081] Broadcast: A point-to-multipoint communication technology. Unlike multicast, the technology associated with broadcast involves the transmitting device sending TBs corresponding to PDUs on the broadcast channel, and all receiving devices being able to receive the PDUs on the broadcast channel. Unlike multicast technology, the scrambling method described above using G-RNTI is not used on broadcast channels in conventional broadcast transmission.

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

[0083] Protocol Stack: Network devices and terminal devices have a specific protocol layer structure used for mutual communication. For example, a 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. A 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 lowest layer (Layer 1), the MAC layer, RLC layer, and PDCP layer belong to the second layer (Layer 2), and the RRC layer belongs to the third layer (Layer 3). In one implementation, a service data adaptation protocol (SDAP) layer may be further included above the PDCP layer. In addition, above the SDAP layer, there may be a transport layer, such as a Transmission Control Protocol / Internet Protocol (TCP / IP) layer, and an application layer.

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

[0085] It should be understood that partitioning based on the protocol layer is just one example, and alternatively, partitioning may be performed based on a different protocol layer. For example, partitioning can be performed based on the RLC layer. Functions of the RLC layer and layers above the RLC layer are set to CU, and functions of protocol layers below the RLC layer are set to DU. Alternatively, partitioning can be performed at the protocol layer. For example, some functions of the RLC layer and functions of protocol layers above the RLC layer are set to CU, and the remaining functions of the RLC layer and functions of protocol layers below the RLC layer are set to DU. In addition, partitioning may be performed alternatively in other ways. For example, partitioning can be performed based on latency. Functions whose processing time must meet latency requirements are set to DU, and functions whose processing time does not need to meet latency requirements are set to 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 an 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 includes the configuration of the protocol layer. Protocol layer entities of network devices and terminal devices transmit, receive, or process data packets or signaling over the radio bearer based on the configuration. Technically, a radio bearer can be understood as a transmission channel. Each radio bearer, whether on the terminal device side or the network device side, includes one PDCP entity and at least one RLC entity for processing data packets transmitted over the radio bearer. In addition to establishing radio bearers, network devices may further add, modify, or remove (release) radio bearers using RRC signaling.

[0087] Multimedia broadcast multicast services are used for point-to-multipoint unidirectional multimedia services. For example, a multimedia broadcast service is transmitted to users in a cell on a common channel via an air interface, or a multicast service subscribed to by a user in a cell is transmitted to the user in multicast mode, resulting in reduced air interface resources.

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

[0089] The access network device in Figure 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 to a 5G access network device in a 5G system, such as a gNB. The technical solutions provided in the embodiments of this application may, alternatively, be applied to future mobile communication systems. Therefore, the access network device in Figure 1 may, alternatively, correspond to access network devices in future mobile communication systems. In Figure 1, an example is used where the access network device is a base station. For actual access network devices, please refer to the above description.

[0090] It should be understood that the communication system shown in Figure 1 may further include more network nodes, such as other terminal devices or access network devices. The access network devices or terminal devices included in the communication system shown in Figure 1 may be various forms of the aforementioned access network devices or terminal devices. These are not shown one by one in the drawings in the embodiments of this application.

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

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

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

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

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

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

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

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

[0099] S202: The core network device receives at least one data packet that is a first service, sent by the data server.

[0100] Specifically, upon receiving at least one data packet that is part of the first service and has been sent by the data server, the core network device determines which access network devices need to receive the first service and thereby sends at least one data packet separately to different access network devices.

[0101] S203: The core network device transmits a first data packet and first instruction information to a first access network device, the first instruction information indicating a sequence of the first data packets in at least one data packet transmitted by the core network device.

[0102] In this embodiment, it should be noted that S201 and S202 are merely optional steps, and S203 unnecessarily depends on S201 and S202. Specifically, data packets 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 instead receive progress information from another location and determine the location of the data packets based on the progress information. In addition, the method by which the core network device transmits data packets to different access network devices is not limited.

[0103] S204: The core network device transmits a second data packet and second instruction information to the second access network device, the second instruction information indicating the sequence order of the second data packet in at least one data packet transmitted 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, but is not limited to this. 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 instruction information is the same as the second instruction information.

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

[0105] Specifically, when a core network device transmits at least one data packet of a first service to an access network device, at least one data packet may carry first instruction information, thereby allowing the access network device to know the transmission progress of the first service. The first instruction information may be implemented by setting a core network sequence number for 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 instruction information, which identifies the sequence of data packets in at least one transmitted data packet.

[0106] Optionally, the first instruction information includes at least one of the following: the General-Purpose Packet Radio Service Tunneling Protocol User Plane Sequence Number (GPRS Tunneling Protocol-U Sequence Number, GTP-U SN) and information on the first service sequence number. The first service sequence number is set by a core network device or 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.

[0107] The first service sequence number is briefly described below 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, it may set different GTP-U SNs when sending the same data packet to different access network devices. However, in this application, the core network device sets the same GTP-U SN for data packets when sending the same data packet, received by the core network device from a data server or generated by the core network device, to different access network devices. In possible implementations, the GTP-U SN is set for each data packet based on the 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 the progress of service transmission based on the GTP-U SN.

[0108] Optionally, when a data server transmits at least one data packet of a first service to a core network device, if at least one data packet carries at least one first service sequence number corresponding to each of the data packets, the core network device may transmit first instruction information to an access network device based on the first service sequence number. The first instruction information may be the first service sequence number carried in at least one data packet. When a data server transmits at least one data packet of a first service to a core network device, if at least one data packet does not carry the first service sequence number, the core network device resets the first service sequence number of at least one data packet based on the sequence in which it receives the data packet. For example, if a core network device receives data packet 1, data packet 2, and data packet 3 from a data server, the core network device may set data packet 1 to the first service sequence number 1, data packet 2 to the first service sequence number 2, and data packet 3 to the first service sequence number 3.

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

[0110] It should be noted that, given that the first data packet and the first instruction information are received from the core network device, the specific implementations in which S205 depends on the aforementioned steps are not limited to those in this embodiment.

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

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

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

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

[0115] Optionally, when a 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 the starting sequence number of the first data packet based on first instruction information. For example, a PDCP entity is used. After the PDCP entity for multicast transmission is re-established, the access network device receives the first instruction information for the first data packet. For example, if the first instruction 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, which is the starting point for PDCP sequence numbers in conventional technologies. Even if the first protocol layer entity is re-established or recovered, it can be ensured that the information corresponding to the data packet is current actual service progress information.

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

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

[0118] In steps S206 and S208, after receiving the data packets and core network sequence numbers transmitted by the core network device, the first and second access network devices need to determine the sequence number of the received data packets. To understand the steps more clearly, the steps are briefly described below with reference to Figure 6. The first access network device receives a first data packet whose core network sequence number GTP-U SN is 8, and based on the GTP-U SN of the first data packet, the first access network device determines that the PDCP SN of the first data packet is 8. 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 the 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 instruction information in data packets having the same content. As a result, the first and second access network devices can determine the same first protocol layer sequence number for data packets having the same content based on the same first instruction information. That is, the sequence number, which is of the first protocol layer and is determined by different access network devices, is the same for data packets having the same data. Therefore, in the process of handing over a terminal device from the first access network device to the second access network device, the second access network device can know the progress of the first service 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 protocol layer sequence numbers for data servers, core network devices, access network devices, and terminal devices may be set for the protocol layer. For example, a core network sequence number is a sequence number set by the core network device for data packets, and a PDCP sequence number is a sequence number set by the PDCP layer of an access network device or terminal device for data packets. 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. Also, "sequence number" is a general term for all sequence numbers and is not limited to a specific sequence number. A specific sequence number needs to be determined specifically based on the scenario. For example, the sequence number for 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 (for example, a header is added to the data packet). This processing is necessary for transmission. After processing, the size or form of the data packet may change. However, as long as the content of the data packet's payload does not change, the data packet may be called the same data packet, e.g., the first data packet.

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

[0124] Optionally, the first access network device may transmit second instruction information to the first terminal device. The second instruction information indicates the sequence number of the first data packet of the first service transmitted 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 possible implementations, once the first protocol entity is established before the first terminal device begins receiving the first service, the first terminal device first obtains configuration information from the first access network device for receiving the first protocol entity. The first access network device includes second instruction information in the configuration information, which indicates the sequence number (e.g., PDCP SN) of the first data packet that is of the first service and is 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 or 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 instruction information to the first terminal device, which indicates the sequence number (e.g., PDCP SN) of the first data packet that is of the first service and is 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: The second access network device sends the second data packet to the second terminal device.

[0128] Optionally, the second access network device may transmit second instruction information to the second terminal device. For a detailed explanation, please refer to the relevant explanation in S209. Details will not be repeated here.

[0129] According to the communication method 200 provided in this application, in the process of handing over a terminal device 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 situations where redundant data packets are received by the terminal or service data is interrupted due to inconsistent multicast service progress between different access network devices.

[0130] To better understand the beneficial effects of the method provided in this application, the procedure for handing over terminal devices between access network devices (e.g., base stations) in the prior art is briefly described below. The procedure for handing over between base stations (gNBs) is shown in Figure 3. Figure 3 is a schematic flowchart of Method 300 for handing over terminal devices between access network devices in the prior art. The handover is initiated by the source gNB. The source gNB (SgNB) decides to hand over the UE based on a measurement report reported by the UE and initiates a handover request to the target gNB (TgNB). After the SgNB receives a positive handover acknowledgment 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 a handover command is sent to the UE, the SgNB stops performing uplink or downlink data transmission with the UE and sends the data stored in the SgNB to the TgNB. After successfully accessing the TgNB, the UE starts uplink or downlink data transmission with the TgNB. Method 300, shown in Figure 3, may include S301 to S308. The steps of Method 300 will be briefly described below with reference to Figure 3.

[0131] S301: During the handover preparation phase, the UE in 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 the UE's target gNB 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 the handover request.

[0133] S303: The target gNB prepares for the UE to be handed over to the target gNB, assigns the cell identification information parameter C-RNTI and another parameter to the UE, and returns C-RNTI and the other parameter to the source gNB via a handover request acknowledgment message. After receiving the handover request acknowledgment message, the source gNB prepares to transfer the packet data to the target gNB.

[0134] S304: The SgNB sends a “Handover Command” to the UE (the Handover Command includes the following information: the new C-RNTI, the SIB of the target gNB, and the UE's configuration information such as the MAC, RLC, and PDCP layer configurations). 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 sent by the UE and the buffered downlink data sent by the UPF to the target gNB.

[0136] S305: The source gNB transmits SN status information and transfers data (dashed line 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 a random access process to obtain uplink timing and uplink resource allocation. The target gNB sends a tracking area TA to the UE, indicating 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 that the handover is complete.

[0138] S307:UE sends "Handover Acknowledgment" information to the target gNB to indicate that the handover is complete.

[0139] S308: The target gNB indicates to the source gNB that the handover is complete, and as a result, the source gNB releases the UE context information.

[0140] Furthermore, the target gNB notifies the core network nodes to update information about the target gNB to which the data is being transferred, so that the core network can send the UE's data to the target gNB.

[0141] In conventional technologies, in some multicast application scenarios, the UE needs to perform a handover procedure in which it receives multicast (groupcast) service from a base station, instantly moves, and hands over to another base station to receive the multicast service. If the multicast service progress 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. Figure 4 is a schematic diagram of multicast service handover scenario 400. Figure 4 includes a core network device 410, an access network device 420, an access network device 430, a terminal device 440, and a terminal device 450. Access network devices 420 and 430 receive multicast service data sent by the core network device 410 and transmit the multicast service data to terminal devices within the coverage of access network devices 420 and 430. Terminal device 450 is handed over from access network device 420 to access network device 430. The multicast service progress of access network devices 420 and 430 does not match. Existing handover procedures may cause terminal device 450 to receive redundant data packets or may cause data interruption on terminal device 450.

[0142] To solve the problem, this application provides a communication method 500. The communication method provided in this application will be described in detail below with reference to Figure 5. Figure 5 is a schematic flowchart of the communication method 500 according to one embodiment of this application. The method 500 may be applied to the scenario shown in Figure 1, and of course, to other communication scenarios. This is not limited to this embodiment of this 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 and second access network devices perform a first service.

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

[0144] In this embodiment of the present application, it should be further understood that the method is described using examples in which terminal devices and access network devices perform the method. The method may also be performed by, but not limitingly, chips, chip systems, processors, etc., used in terminal devices and access network devices.

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

[0146] S501: The first access network device forwards a data packet to the second access network device, and the data packet transmitted by the first access network device is a data packet for the first service.

[0147] S502: The second access network device receives data packets transmitted by the first access network device.

[0148] Specifically, in the handover process, the first access network device needs to forward data sent by the core network device but not successfully delivered to the first terminal device to the second access network device. This is the data forwarding process. The sequence numbers of the first protocol layer of both access network devices are determined based on the first instruction information sent by the core network device. Therefore, for data packets with the same content, the sequence numbers of the first protocol layer determined by the two access network devices are the same. Thus, 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 at the first access network device based on the sequence number of the data packets, and can use a 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, and the third instruction information instructs the first access network device to stop forwarding the data packet to the second access network device.

[0150] Optionally, if the second sequence number of the first protocol layer of a data packet 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 a data packet transmitted by the first access network device, the second access network device transmits a third instruction to the first access network device.

[0151] Optionally, if the second sequence number of the first protocol layer of a data packet transmitted by the second access network device to the first terminal device is N, and the first sequence number of the first protocol layer of a data packet transmitted by the first access network device is N-1, the second access network device transmits third instruction information to the first access network device.

[0152] Specifically, after a terminal device has been 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 any data packets of the first service that were not successfully received by the terminal from the first access network device to the second access network device. If the sequence number of the data packets received by the second access network device from the first access network device is greater than or equal to the sequence number of the data packets sent to the terminal device, the second access network device instructs to stop data transfer. The first service assumes that the transmission progress of the second access network device is fast. Figure 6 is a schematic flowchart of data transfer in the 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 instructional 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 sending data packets to the first and second access network devices by the user plane function is inconsistent. The maximum sequence number of data packets for the first service sent by the first access network device is SN=8, and the maximum sequence number of data packets for the first service sent 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, if 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 data packets forwarded by the first access network device catches up with the transmission progress of the second access network device, that is, when the sequence number of the data packets received by the second access network device from the first access network device is greater than or equal to the SN of the first data packet of the first service transmitted by the second access network device after the terminal device was successfully handed over to the second access network device, the second access network device sends a stop instruction to the first access network device to indicate that data forwarding has ended.

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

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

[0155] S505: Based on the instruction information of the third, the first access network device stops forwarding data packets to the second access network device.

[0156] Specifically, after receiving the instruction information, the first access network device stops data transfer. The first access network device continues data forwarding until it receives the stop instruction information from the target base station.

[0157] Therefore, during the handover process of the first terminal device, the second access network device determines whether data transfer of the first access network device may be stopped, and sends data transfer stop instruction information to the first access network device. As a result, the continuity of multicast service reception for the terminal device during the handover process is guaranteed, and packet loss or redundant transmission is avoided.

[0158] Optionally, before step S501, 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 which data packets of the first service were successfully received by the first terminal device and which data packets were not 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 status report information, the fourth instruction information indicating the sequence number of the first data packet forwarded by the first access network device to the second access network device, the first data packet being the data packet that the first access network device initiates forwarding to the second access network device, or the 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 instruction information transmitted by the second access network device.

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

[0163] Specifically, the first terminal device sends data packet status report information to the second access network device after handover. The status report information indicates to the second access network device which data packets were successfully received by the first terminal device and which were not successfully received by the first terminal device. After receiving the status report information, the second access network device sends a fourth instruction to the first access network device. The fourth instruction indicates the sequence number of the first protocol layer of the initial data packet not received by the first terminal device, i.e., the initiating data packet in the data transfer by the first access network device. In this way, it is possible to prevent the first terminal device from receiving redundant data packets. Specifically, the following case can be avoided: 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 sent by the second access network device to the first terminal device.

[0164] This application provides a communication method 600. The communication method provided in this application will be described in detail below with reference to Figure 7. Figure 7 is a schematic flowchart of the communication method 600 according to one embodiment of this application. The method 600 may be applied to the scenario shown in Figure 1, and of course, to other communication scenarios. This is not limited to this embodiment of the application. In the method 600, during the process of a first terminal device connected to a first access network device being handed over from the first access network device to a second access network device, the terminal device remains connected to both the first and second access network devices. In this way, the first and second access network devices can simultaneously transmit the 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 can 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 is consecutive to the sequence number of a data packet received from the second access network device (for example, if a data packet with the largest SN9 is received from the first access network device and a data packet with the smallest SN10 is received from the second access network device), the first access network device may stop transmitting data packets to the terminal device or disconnect from the terminal device.

[0165] In this embodiment of the present application, it should be further understood that the method is described using examples in which terminal devices and access network devices perform the method. The method may also be performed by, but not limitingly, chips, chip systems, processors, etc., used in terminal devices and access network devices.

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

[0167] S601: The second access network device transmits fifth instruction information to the first access network device, the fifth instruction information including a first sequence number N, the first sequence number indicating the sequence number of the first data packet of the first service that is transmitted to the first terminal device by the second access network device after the first terminal device has been successfully handed over from the first access network device to the second access network device.

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

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

[0170] Therefore, in the handover process, the first access network device determines when to terminate its connection to the terminal device based on the SN indicated by the second access network device, thereby ensuring the continuity of multicast service reception for the terminal device during the handover process and avoiding packet loss or redundant transmission.

[0171] Specifically, during the handover process, the first terminal device receives data packets of the first service from both the first and second access network devices. The first access network device does not need to forward the data packets of the first service to the second access network device; in other words, a data forwarding process is unnecessary. For example, in Figure 5, no data forwarding is performed for data packets with SNs 9 and 10, and the data packets are sent directly to the first terminal device by the first access network device. After the first terminal device has been 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 that is of the first service and is to be sent to the terminal device to the first access network device. Based on the SN of the first data packet, the first access network device decides when to stop sending data to the first terminal device. If the sequence number of the first protocol layer of a data packet successfully transmitted to the terminal device by the first access network device is N-1, the first access network device stops transmitting data packets to the first terminal device. For example, in Figure 5, after transmitting data packet number 11-1=10, the first access network device disconnects from the first terminal device.

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

[0173] Optionally, if a terminal device is successfully handed over to a second access network device, the second access network device may send information to the first access network device indicating that the first terminal device has been successfully handed over. 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 the first sequence number of the first protocol layer newly transmitted to the first terminal device, and the second access network device determines, based on the first sequence number of the first protocol layer and the second sequence number of the first protocol layer, whether the first access network device will stop transmitting data packets of the first service to the first terminal device, the second sequence number of the first protocol layer being the first protocol layer sequence number of the first data packet received by the first terminal device from the second access network device after the first terminal device was 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 it to disconnect from the first terminal device.

[0174] Optionally, the second access network device transmits a fifth instruction to the first access network device. The fifth instruction includes a first sequence number N-1, which instructs the first access network device to stop transmitting data packets to the terminal device if the first protocol layer sequence number of a data packet successfully transmitted to the terminal device by the first access network 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 a data packet with a first sequence number of N-1 has been sent.

[0176] The method for measuring the communication parameters of a multi-SIM terminal device according to the embodiment of this application has been described in detail above with reference to Figures 1 to 7. The communication device in the embodiment of this application will now be described in detail with reference to Figures 8 to 10.

[0177] Figure 8 is a schematic block diagram of a communication device 700 according to one embodiment of this application.

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

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

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

[0181] In possible ways, the device 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 called a decision 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. In possible ways, the storage unit 720 is configured to store instructions. In another implementation, the storage unit may be configured to store data or information. The storage unit 720 may be implemented using memory.

[0184] In some possible designs, the processing unit 710 is configured to execute instructions stored in the storage unit 720, so that the device 700 performs the steps performed by the terminal device in the manner described above. Alternatively, the processing unit 710 may be configured to retrieve data in the storage unit 720 so that the device 700 performs the steps performed by the terminal device in the manner described above.

[0185] In some possible designs, the processing unit 710 is configured to execute instructions stored in the storage unit 720, so that the device 700 performs the steps performed by the access network device in the manner described above. Alternatively, the processing unit 710 may be configured to retrieve data in the storage unit 720 so that the device 700 performs the steps performed by the access network device in the manner described above.

[0186] For example, the processing unit 710, the storage unit 720, and the transceiver unit 730 may communicate with each other using internal connection paths and transfer control signals and / or data signals. 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 transmit signals, and complete the steps of the terminal device or access network device in the method described above. The storage unit 720 may be integrated with the processing unit 710 or may be provided separately from the processing unit 710.

[0187] If, optionally, the device 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 transmitter may be the same physical entity or different physical entities. When the receiver and transmitter are the same physical entity, they may be collectively referred to as a transceiver.

[0188] If the device 700 is a terminal device, or if the device is an access network device or a core network device, the transceiver unit 730 may be a transmitting unit or transmitter when transmitting information, or 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, and as a result, the device can 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 device 700 is a chip or circuit, the transceiver unit 730 includes an input interface and an output interface.

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

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

[0192] In another implementation, the communication device provided in this embodiment of the present application (e.g., a terminal device or an access network device) may be considered to be implemented using a general-purpose computer. That is, 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 implements the functions of the processing unit 710 and the transceiver unit 730 by executing the code in the storage unit 720.

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

[0194] In one implementation, the first instruction information includes at least one of the following information: a general-purpose packet radio service tunneling protocol user plane GTP-U sequence number and a first service sequence number, the first service sequence number being set by a core network device or data server, the first data packet being a data packet of a first service, and at least one data packet being a data packet of a first service.

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

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

[0197] In one implementation, the transceiver unit 730 is further configured to transmit a second instruction information to a terminal device, the second instruction information indicating the sequence number of the first data packet that is of a first service and is transmitted to the terminal device by a first access network 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 a second access network device, which instructs 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 a fourth instruction information transmitted by a second access network device, the fourth instruction information indicating the sequence number of the 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 instruction information.

[0200] In one implementation, the transceiver unit 730 is further configured to receive a fifth instruction information transmitted by a second access network device, the fifth instruction information including a first sequence number N, the fifth instruction information including a second sequence number N, the second sequence number indicating the sequence number of the first data packet which is a first service and is sent to the terminal device by the second access network device after the handover of the terminal device is complete. The processing unit 710 is configured to decide to stop transmitting data packets to the terminal device if the sequence number which is a protocol layer and corresponds to a data packet successfully transmitted to the terminal device by the first access network device is N-1.

[0201] If the device 700 is configured within or is the first access network device, modules or units within the device 700 may be configured to perform operations or processing steps performed by the first access network device in the manner described above. For the sake of avoiding repetition, a detailed explanation is omitted here.

[0202] In some embodiments, the device 700 may be a terminal device, or a chip or circuit located on a terminal device. When the device 700 is a terminal device, or a chip or circuit located on a terminal device, the transceiver unit 730 is configured to receive second instruction information transmitted by a first access network device, the second instruction information indicating the sequence number of the first data packet that is a first service, transmitted 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, and the request information requests the first access network device to send the sequence number of the first data packet which is of the first service and is sent by the first access network device to the terminal device after the first protocol entity is re-established or recovered.

[0204] In one implementation, the transceiver unit 730 is further configured to transmit data packet status report information to a second access network device, which indicates to the second access network device which data packets were successfully received by the terminal device and which 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.

[0205] If the apparatus 700 consists of or is a terminal device, modules or units of the apparatus 700 may be configured to perform operations or processing steps performed by the first terminal device in the manner described above. For the sake of avoiding repetition, a detailed explanation is omitted here.

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

[0207] In one implementation, the first instruction information includes at least one of the following information: a general-purpose packet radio service tunneling protocol user plane GTP-U sequence number and a first service sequence number, the first service sequence number being set by a core network device or data server, the first data packet being a data packet of a first service, and at least one data packet being a data packet of a first service.

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

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

[0210] In one implementation, the transceiver unit 730 is further configured to transmit a second instruction information to a terminal device, the second instruction information indicating the sequence number of the first data packet that is of a first service and is transmitted to the terminal device by a first access network 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 configuration, the transceiver unit 730 receives data packets transmitted by the first access network device. If a second terminal device connected to a first access network device is handed over from the first access network device to the second access network device, and both the first and second terminal devices are performing the first service, and a data packet transmitted by the first access network device is a data packet for the first service, and the second sequence number of the 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, then a third instruction is sent to the first access network device, and the third instruction instructs the first access network device to stop forwarding the data packet to the second access network device. It is further configured in this way.

[0212] In one implementation configuration, the transceiver unit 730 receives status report information of a data packet transmitted by a second terminal device, the status report information of the data packet indicates to the second access network device which data packets were successfully received by the terminal device and which were not successfully received by the terminal device, and based on the status report information, transmits fourth instruction information to the first access network device, the fourth instruction information indicating the sequence number of the 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 transmit fifth instruction information to a first access network device, the fifth instruction information including a second sequence number N, the second sequence number indicating the sequence number of the first data packet that is of the first service and is transmitted to the second terminal device by the second access network device after the handover of the second terminal device is complete.

[0214] If the device 700 is configured within or is a second access network device, modules or units within the device 700 may be configured to perform operations or processing steps performed by the second access network device in the manner described above. For the sake of avoiding repetition, a detailed explanation is omitted here.

[0215] In some embodiments, the device 700 may be a core network device, or a chip or circuit located on a core network device. When the device 700 is a core network device, or a chip or circuit located on a core network device, the transceiver unit 730 is configured to receive a first packet transmitted by a data server, and to transmit a second data packet and first instruction information to a first access network device, wherein the first instruction information indicates a sequence of second data packets in 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 second instruction information to a second access network device, wherein the second instruction information indicates a sequence of third data packets in 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 instruction information includes at least one of the following information: a general-purpose packet radio service tunneling protocol user plane GTP-U sequence number and a first service sequence number, the first service sequence number being set by a core network device or data server, the first data packet being a data packet of a first service, and at least one data packet being a data packet of a first service.

[0217] If the device 700 is configured within or is a core network device, modules or units within the device 700 may be configured to perform operations or processing steps performed by the core network device in the manner described above. For the sake of avoiding repetition, a detailed explanation is omitted here.

[0218] For a concept, description, detailed description, and other steps of the apparatus 700 related to the technical solution provided in the embodiments of this application, please refer to the description of the method or other embodiments described above. Details will not be repeated here.

[0219] Figure 9 is a schematic diagram of the structure of the terminal device 800 according to this application. The terminal device 800 can perform the operations performed by the terminal device in the method embodiment described above.

[0220] For the sake of clarity, Figure 9 shows only the main components of the terminal device. As shown in Figure 9, the terminal device 800 includes a processor, memory, control circuits, an antenna, and input / output devices.

[0221] The processor is primarily configured to process communication protocols and communication data, control the entire terminal device, execute software programs, process data for software programs, and, for example, support the terminal device when performing the operations described in the aforementioned embodiment of the transmission precoding matrix instruction method. The memory is primarily configured to store software programs and data, for example, the codebook described in the aforementioned embodiment. 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 antenna may also be called a transceiver, primarily configured to transmit and receive radio frequency signals in electromagnetic wave form. Input / output devices, such as touchscreens, displays, or keyboards, are primarily configured to receive data entered by the user and output data to the user.

[0222] After the terminal device is powered on, the processor may read the software program in the memory unit, interpret and execute the software program's instructions, and process the software program's data. If the 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 electromagnetic wave form via the antenna. When data is transmitted to the terminal device, the radio frequency circuit receives the radio frequency signal via the antenna, converts the radio frequency signal back into a baseband signal, and outputs the baseband signal to the processor. The processor converts the baseband signal back into data and processes the data.

[0223] Those skilled in the art will understand that, for the sake of clarity, Figure 9 shows only one memory and only one processor. Actual terminal devices may have multiple processors and memories. Memory is sometimes also called a storage medium or storage device. This is not limited to the embodiments of this application.

[0224] For example, a 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 those software programs. The functions of the baseband processor and the central processing unit are integrated into the processor shown in Figure 9. Those skilled in the art will understand that the baseband processor and the central processing unit may be independent processors and interconnected using technologies such as buses. Those skilled in the art will understand that a terminal device may include multiple baseband processors to adapt to different network standards, a terminal device may include 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 represented as a baseband processing circuit or baseband processing chip. Alternatively, the central processing unit may be represented as a central processing circuit or central processing chip. The functions for processing communication protocols and communication data may be incorporated into the processor or stored in a memory unit in the form of software programs. The processor executes software programs to perform the baseband processing functions.

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

[0226] Figure 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 the access devices (e.g., a first access network device, a second access network device, or a third access network device) in the methods described above. The access network device 900 includes one or more radio frequency units, e.g., a remote radio unit (RRU) 910, and one or more (sometimes called a digital unit, DU) baseband units (BBU) 920. The RRU 910 may also be called 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 to perform conversion between radio frequency signals and baseband signals, for example, to transmit signaling messages to terminal devices in the embodiments described above. The BBU 920 is mainly configured to perform baseband processing, control base stations, etc. The RRU910 and BBU920 may be physically located together, or they may be physically separated, i.e., located in distributed base stations.

[0227] The BBU 920 is the base station's control center, sometimes referred to as the processing unit, and is primarily configured to perform baseband processing functions such as channel coding, multiplexing, modulation, or spreading. For example, the BBU (processing unit) 920 may be configured to control the base station 40 to perform the operational procedures related to the network device in the method embodiment described above.

[0228] In one example, the BBU920 may include one or more boards, and the multiple boards may together support a radio access network of a single access standard (e.g., an LTE system or a 5G system), or they may separately support radio access networks of different access standards. The BBU920 further includes memory 921 and a processor 922. Memory 921 is configured to store necessary instructions and data. For example, memory 921 stores the codebook in the above embodiment. The processor 922 is configured to control a base station to perform necessary operations, for example, to control a base station to perform operating procedures relating to a network device in the above method embodiment. Memory 921 and processor 922 may serve one or more boards. In other words, the memory and processor may be located separately on each board. Alternatively, multiple boards may share the same memory and the same processor. In addition, necessary circuitry may be further located on each board.

[0229] In possible implementations, with the advancement of system-on-chip (SoC) technology, all or some 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 these programs to realize the base station-related functions. Optionally, the base station function chip may also read from the chip's external memory to perform base station-related functions.

[0230] It should be understood that the structure of the access network device shown in Figure 10 is merely a possible form and should not constitute any limitation to the embodiments of this application. This application does not rule out the possibility of other forms of base station structures emerging in the future.

[0231] It should be understood that the processor in the embodiments of this application may be a central processing unit (CPU). Alternatively, the processor may be another general-purpose processor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), another 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.

[0232] It should be further understood that the memory in the embodiments of this application may be volatile memory or non-volatile memory, and may include both 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. Rather than providing a limited explanation, 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 (synchronous DRAM, SDRAM), double data rate synchronous dynamic random access memory (DDR SDRAM), enhanced synchronous dynamic random access memory (enhanced SDRAM, ESDRAM), synchlink dynamic random access memory (synchlink DRAM, SLDRAM), and direct rambus random access memory (DR RAM).

[0233] All or part of the embodiments described above may be implemented using software, hardware, firmware, or any combination thereof. Where software is used to implement the embodiments, the embodiments described above may be implemented in whole or in part in the form of a computer program product. A 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, all or part of the procedures or functions according to the embodiments of this application are generated. The computer may be a general-purpose computer, a dedicated computer, a computer network, or other programmable device. Computer instructions may be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another. For example, computer instructions may be transmitted from one website, computer, server, or data center to another by a wired (e.g., infrared, wireless, 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 usable media may be magnetic media (e.g., floppy disks, hard disks, or magnetic tapes), optical media (e.g., DVDs), or semiconductor media. Semiconductor media may be solid-state drives.

[0234] One embodiment of this application further provides a computer-readable medium. The computer-readable medium stores a computer program. When the computer program is executed by a computer, steps are performed by a terminal device, a first access network device, a second access network device, or any one of the core network devices of the above embodiments.

[0235] One embodiment of this application further provides a computer program product. When the computer program product is executed by a computer, steps performed by a terminal device, steps performed by a first access network device, steps performed by a second access network device, or steps performed by any one of the core network devices of the above embodiments are carried out.

[0236] One embodiment of the present application further provides a system-on-a-chip. The system-on-a-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, pins, a circuit, etc. The processing unit can execute computer instructions so that a chip in a communication device performs steps performed by a terminal device, steps performed by a first access network device, steps performed by a second access network device, and steps performed by a core network device, as provided in the aforementioned embodiments of the present application.

[0237] Optionally, computer instructions are stored in memory units.

[0238] According to the method provided in the embodiments of this application, one embodiment of this application further provides a communication system including the aforementioned first access network device, the aforementioned second access network device, the aforementioned core network device, and the aforementioned terminal device.

[0239] The embodiments of this application may be used independently or in combination; this is not limited herein.

[0240] In addition, aspects or features of this application may be implemented as methods, apparatus, or products using standard programming and / or engineering techniques. As used in this application, the term “product” encompasses computer programs that can be accessed 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 discs (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). In addition, the 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 media” may include, but is not limited to, wireless channels and various other media that can store, contain, and / or carry instructions and / or data.

[0241] The term "and / or" describes the relationship between the related objects and indicates that there may be three possible relationships. For example, A and / or B could represent three cases: A only exists, both A and B exist, and B only exists. The symbol " / " generally indicates an "or" relationship between the related objects. "At least one" means one or more. Similar to "A and / or B," "at least one of A and B" describes the relationship between the related objects and indicates that there may be three possible relationships. For example, at least one of A and B could represent three cases: A only exists, both A and B exist, and B only exists.

[0242] Those skilled in the art will recognize, in combination with the examples described in the embodiments disclosed herein, that units and algorithmic 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 functions described for each specific application, but such implementations should not be considered to exceed the scope of this application.

[0243] For the sake of simplicity, it will be readily apparent to those skilled in the art that the detailed operating processes of the aforementioned systems, apparatus, and units are described by referring to the corresponding processes in the method embodiments described above. Details will not be repeated here.

[0244] It should be understood that in some embodiments provided in this application, the disclosed systems, apparatus, and methods may be implemented in other ways. For example, the embodiments of the apparatus described above are merely examples. For example, the division into units is merely a logical functional division and may be other divisions 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 performed. In addition, the interconnections, direct connections, or communication connections shown or described may be implemented by using some interfaces. Indirect coupling or communication connections between apparatus or units may be implemented electrical, mechanical, or in other forms.

[0245] Units described as separate parts may or may not be physically separated, and parts shown as units may or may not be physical units, that is, they may be located in one place or distributed across multiple network units. Some or all of the units may be selected on a practical basis to achieve the objectives of the solution of the embodiment.

[0246] In addition, the functional units in the embodiments of this application may be integrated into a single processing unit, or each unit may exist physically independently, or two or more units may be integrated into a single unit.

[0247] When a function is implemented in the form of a software function unit and sold or used as an independent product, the function may be stored on a computer-readable storage medium. Based on this understanding, the technical solution of this application, in its essence, or in part, contributes to the prior art, or a part of the technical solution may be implemented in the form of a software product. The computer software product is stored on a storage medium and includes several 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 embodiment of this application. The aforementioned storage medium includes any medium capable of storing program code, such as a USB flash drive, a removable hard disk, read-only memory (ROM), random access memory (RAM), a magnetic disk, or an optical disk.

[0248] The foregoing description represents only a specific implementation of this application, and the scope of protection of this application is not limited thereto. Any modifications or substitutions readily conceivable by a person skilled in the art within the scope of the technical scope disclosed herein shall also fall within the scope of protection of this application. Accordingly, the scope of protection of this application shall be subject to the scope of protection 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 memory units 730 Transceiver Unit 800 terminal devices 810 Transceiver Unit 820 processing units 900 Access Network Devices 910 Remote Wireless Unit (RRU) 911 Antenna 912 Radio frequency unit 920 Baseband Unit (BBU) 921 memory 922 Processors

Claims

1. A communication method performed by a first access network device, A step of receiving a first data packet and a first core network sequence number from a core network device, wherein the first core network sequence number indicates the sequence of the first data packet in at least one data packet, the first core network sequence number is set by the core network device, the at least one data packet belongs to a first service, and the first service is a multicast service; A step of determining the first sequence number of the first protocol layer of the first data packet based on the first core network sequence number, wherein the value of the first sequence number of the first protocol layer of the first data packet is equal to the value of the first core network sequence number. The steps include sending the first data packet to a terminal device, A step of sending a handover command to the terminal device, wherein the handover command instructs the terminal device to hand over from the first access network device to a second access network device, and the sequence number of the first protocol layer of the data packet of the second access network device is set to be equal to the value of the core network sequence number for the data packet. The steps include: transmitting the status information of the sequence number to the second access network device outside of the data packet; Methods that include...

2. The method according to claim 1, wherein the first sequence number of the first protocol layer is used by the first protocol layer to process sorting or duplicate detection for the first data packets.

3. The method according to claim 1 or 2, wherein the first protocol layer is a packet data convergence protocol (PDCP) layer.

4. The method according to any one of claims 1 to 3, wherein the sequence number indicates progress information of the first service on the first access network device.

5. The method according to any one of claims 1 to 4, wherein the second core network sequence number corresponding to the second data packet is the same as the first core network sequence number, the second data packet is from the core network device to the second access network device, and the data of the first data packet is the same as the data of the second data packet.

6. Steps to set the first sequence number of the first protocol layer of the first data packet to the first core network sequence number when any one of the following occurs: establishment of a first protocol entity, re-establishment of the first protocol entity, or recovery of the first protocol entity: The method according to any one of claims 1 to 5, further comprising:

7. A step of transmitting instruction information to the terminal device, wherein the instruction information indicates the sequence number of the first data packet of the first service transmitted to the terminal device by the first access network device after the first protocol entity is established, after the first protocol entity is re-established, or after the first protocol entity is recovered. The method according to any one of claims 1 to 6, further comprising:

8. The steps include receiving third instruction information from the second access network device, wherein the third instruction information instructs the first access network device to stop forwarding data packets to the second access network device, The steps include stopping the transfer of the data packets to the second access network device based on the third instruction information, and The method according to any one of claims 1 to 7, further comprising:

9. The steps include receiving a fourth instruction information transmitted by the second access network device, wherein the fourth instruction information indicates the sequence number of the first data packet transferred by the first access network device to the second access network device, The steps include: forwarding a data packet to the second access network device based on the fourth instruction information; The method according to claim 8, further comprising:

10. A step of receiving a fifth instruction information transmitted by the second access network device, wherein the fifth instruction information includes a second sequence number N, the second sequence number indicating the sequence number of the first data packet of the first service transmitted to the terminal device by the second access network device after the handover of the terminal device is completed. If the sequence number of the data packet successfully transmitted to the terminal device by the first access network device is N-1, the first access network device stops transmitting the data packet to the terminal device. The method according to any one of claims 1 to 9, further comprising:

11. A communication device, A transceiver unit configured to receive a first data packet and a first core network sequence number from a core network device, wherein the first core network sequence number indicates the sequence of the first data packet in at least one data packet, the first core network sequence number is set by the core network device, the at least one data packet belongs to a first service, and the first service is a multicast service, A processing unit configured to determine the first sequence number of the first protocol layer of the first data packet based on the first core network sequence number, wherein the value of the first sequence number of the first protocol layer of the first data packet is equal to the value of the first core network sequence number. Equipped with, The transceiver unit is further configured to transmit the first data packet to a terminal device and to transmit a handover command to the terminal device, the handover command instructing the terminal device to hand over from the communication device to a second access network device, the sequence number of the first protocol layer of the data packet of the second access network device is set to be equal to the value of the core network sequence number for the data packet. The transceiver unit is further configured to transmit the status information of the sequence number to the second access network device outside of the data packet, as a communication device.

12. The communication device according to claim 11, wherein the first protocol layer is a packet data convergence protocol (PDCP) layer.

13. The communication device according to claim 11 or 12, wherein the first sequence number of the first protocol layer is used by the first protocol layer to process sorting or duplicate detection for the first data packets.

14. The communication device according to any one of claims 11 to 13, wherein the sequence number indicates the progress information of the first service in the communication device.

15. The communication device according to any one of claims 11 to 14, wherein the second core network sequence number corresponding to the second data packet is the same as the first core network sequence number, the second data packet is from the core network device to the second access network device, and the data of the first data packet is the same as the data of the second data packet.

16. The aforementioned processing unit When any one of the following occurs: establishment of a first protocol entity, re-establishment of the first protocol entity, or recovery of the first protocol entity, the first sequence number of the first protocol layer of the first data packet is set to the first core network sequence number. A communication device according to any one of claims 11 to 15, further configured as follows.

17. The aforementioned transceiver unit, Instructional information is transmitted to the terminal device, the instructional information indicating the sequence number of the first data packet of the first service that is transmitted to the terminal device by the communication device after the first protocol entity is established, after the first protocol entity is re-established, or after the first protocol entity is recovered. A communication device according to any one of claims 11 to 16, further configured as follows.

18. The aforementioned transceiver unit, The second access network device receives a third instruction information, and the third instruction information instructs the communication device to stop forwarding data packets to the second access network device. It is further configured in this way, The aforementioned processing unit Based on the third instruction information, the forwarding of the data packets to the second access network device is stopped. A communication device according to any one of claims 11 to 17, further configured as follows.

19. The aforementioned transceiver unit, The communication device receives a fourth instruction information transmitted by the second access network device, the fourth instruction information indicating the sequence number of the first data packet transferred to the second access network device by the communication device. It is further configured in this way, The aforementioned processing unit Based on the fourth instruction information, the data packet is forwarded to the second access network device. The communication device according to claim 18, further configured as follows.

20. The aforementioned transceiver unit, The terminal device receives a fifth instruction information transmitted by a second access network device, the fifth instruction information including a second sequence number N, the second sequence number indicating the sequence number of the first data packet of the first service transmitted to the terminal device by the second access network device after the handover of the terminal device is completed. It is further configured in this way, The aforementioned processing unit If the protocol layer sequence number of a data packet successfully transmitted to the terminal device by the communication device is N-1, it is decided to stop transmitting the data packet to the terminal device. A communication device according to any one of claims 11 to 17, further configured as follows.

21. A communication device comprising a processor, wherein the processor is connected to a memory, the memory is configured to store a computer program, and the processor is configured to execute the computer program stored in the memory so that the communication device can perform the method according to any one of claims 1 to 10.

22. A computer-readable storage medium, wherein the computer-readable storage medium stores a computer program, and when the computer program is executed, the method according to any one of claims 1 to 10 is performed.

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