Communication method and apparatus

Abstract

The present application relates to the field of communication technology and discloses a communication method and apparatus. The method includes: after determining that a first cell is a serving cell of a terminal device, an access network device can send N sets of data transmission mode information to the terminal device in the first cell, where N is a positive integer. The N sets of data transmission mode information include first data transmission mode information corresponding to a handover of the terminal device from a second cell to the first cell, and / or second data transmission mode information corresponding to a handover of the terminal device from the second cell to a third cell, where the first cell, the second cell, and the third cell are cells managed by the access network device. According to the method, the access network device can send data transmission mode information corresponding to a handover of the terminal device between multiple cells to the terminal device in the first cell, so that the terminal device can directly use the corresponding data transmission mode information to effectively save transmission resources when the terminal device is subsequently handed over between multiple cells.

Description

[Technical Field]

[0001] The present application relates to the field of communication technologies, and more particularly to communication methods and devices. [Background technology]

[0002] In a wireless communication system, when a terminal device moves, the terminal device may move from the coverage of one cell to the coverage of another cell. In order to ensure service continuity and communication quality of the terminal device, the terminal device needs to be handed over between different cells. The cell serving the terminal device before the terminal device is handed over may be referred to as a source serving cell or a source cell, and the cell serving the terminal device after the terminal device is handed over may be referred to as a target serving cell or a target cell.

[0003] However, to implement the handover of a terminal device between multiple cells, information needs to be exchanged between the access network device and the terminal device, which results in high transmission resource consumption. Therefore, how to reduce the transmission resource consumption for the handover of a terminal device between multiple cells still needs to be further studied. Summary of the Invention [Problem to be solved by the invention]

[0004] The present application provides a communication method and apparatus for reducing transmission resource consumption caused by handover of a terminal device between multiple cells.

[0005] According to a first aspect, an embodiment of the present application provides a communication method. The method may be applied to an access network device or a module within the access network device. In an example where the method is applied to the access network device, cells managed by the access network device include a first cell, a second cell, and a third cell. In the method, the access network device determines that the first cell is a serving cell of a terminal device and transmits N sets of data transmission mode information for the terminal device in the first cell to the terminal device, where N is a positive integer. The N sets of data transmission mode information include first data transmission mode information corresponding to performing a handover of the terminal device from the second cell to the first cell via a first type of cell handover and / or second data transmission mode information corresponding to performing a handover of the terminal device from the second cell to the third cell via the first type of cell handover.

[0006] According to the aforementioned method, the access network device can send, to the terminal device in the first cell, data transmission mode information corresponding to handover of the terminal device between the multiple cells, so that the terminal device can directly use the corresponding data transmission mode information when the terminal device is subsequently handed over between the multiple cells, effectively reducing the transmission resource consumption caused by the handover of the terminal device between the multiple cells, in other words, saving transmission resources.

[0007] In a possible design, after the terminal device is handed over from the first cell to the second cell via the first type of cell handover, the method further includes a step of sending first instruction information to the terminal device in the second cell, where the first instruction information instructs the terminal device to perform data transmission with the access network device based on the first data transmission mode information in the N sets of data transmission mode information after the terminal device is handed over from the second cell to the first cell via the first type of cell handover, or a step of sending second instruction information to the terminal device in the second cell, where the second instruction information instructs the terminal device to perform data transmission with the access network device based on the second data transmission mode information in the N sets of data transmission mode information after the terminal device is handed over from the second cell to the third cell via the first type of cell handover.

[0008] In a possible design, the method further includes receiving third and fourth indication information from the terminal device in the first cell, where the third indication information indicates that the terminal device has been handed over from the second cell to the first cell via a first type of cell handover, and the fourth indication information instructs the access network device to perform data transmission with the terminal device based on the first data transmission mode information in the N sets of data transmission mode information; or receiving fifth and sixth indication information from the terminal device in the third cell, where the fifth indication information indicates that the terminal device has been handed over from the second cell to the third cell via the first type of cell handover, and the sixth indication information instructs the access network device to perform data transmission with the terminal device based on the second data transmission mode information in the N sets of data transmission mode information.

[0009] In a possible design, the method further includes a step of determining that at least one of the following conditions is met: the terminal device needs to enter an idle mode or an inactive mode; the terminal device needs to be handed over to a fourth cell via a second type cell handover; and the N sets of data transmission mode information needs to be changed; and a step of releasing the N sets of data transmission mode information and / or sending seventh instruction information to the terminal device, wherein the seventh instruction information instructs the terminal device to release the N sets of data transmission mode information.

[0010] In a possible design, determining that the first cell is a serving cell of the terminal device includes determining that the first cell is a serving cell of the terminal device when the terminal device accesses the first cell in an idle mode or an inactive mode, or determining that the first cell is a serving cell of the terminal device when the terminal device is handed over to the first cell via a second type of cell handover.

[0011] In a possible design, the second type of cell handover is a cell level measurement based cell handover.

[0012] In a possible design, the first data transmission mode information or the second data transmission mode information includes at least one of first information, where the first information indicates whether to perform Packet Data Convergence Protocol (PDCP) reestablishment, second information, where the second information indicates whether to perform PDCP data recovery, or third information, where the third information indicates whether to send a random access preamble to the target cell to obtain uplink synchronization information for the target cell.

[0013] In a possible design, the first type of cell handover is a cell handover based on beam level measurements.

[0014] According to a second aspect, an embodiment of the present application provides a communication method. The method may be applied to a terminal device or a module within the terminal device. An example in which the method is applied to the terminal device is used. In the method, the terminal device determines that a first cell is a serving cell of the terminal device and receives N sets of data transmission mode information from an access network device in the first cell, where N is a positive integer. The N sets of data transmission mode information include first data transmission mode information corresponding to performing a handover of the terminal device from a second cell to the first cell via a first type of cell handover and / or second data transmission mode information corresponding to performing a handover of the terminal device from the second cell to a third cell via the first type of cell handover, where the first cell, the second cell, and the third cell are cells managed by the access network device (in other words, the first cell, the second cell, and the third cell belong to the access network device).

[0015] In a possible design, after the terminal device is handed over from the first cell to the second cell via the first type of cell handover, the method further includes a step of receiving first instruction information from the access network device in the second cell, the first instruction information instructing the terminal device to perform data transmission with the access network device based on first data transmission mode information in the N sets of data transmission mode information after the terminal device is handed over from the second cell to the first cell via the first type of cell handover, or a step of receiving second instruction information from the access network device in the second cell, the second instruction information instructing the terminal device to perform data transmission with the access network device based on second data transmission mode information in the N sets of data transmission mode information after the terminal device is handed over from the second cell to the third cell via the first type of cell handover.

[0016] In a possible design, the method further includes: after the terminal device is handed over from the second cell to the first cell, sending third indication information and fourth indication information to the access network device in the first cell, where the third indication information indicates that the terminal device has been handed over from the second cell to the first cell via a first type of cell handover, and the fourth indication information instructs the access network device to perform data transmission with the terminal device based on the first data transmission mode information in the N sets of data transmission mode information; or after the terminal device is handed over from the second cell to the third cell, sending fifth indication information and sixth indication information to the access network device in the third cell, where the fifth indication information indicates that the terminal device has been handed over from the second cell to the third cell via the first type of cell handover, and the sixth indication information instructs the access network device to perform data transmission with the terminal device based on the second data transmission mode information in the N sets of data transmission mode information.

[0017] In a possible design, the method further includes a step of receiving seventh instruction information from the access network device, the seventh instruction information instructing the terminal device to release N sets of data transmission mode information.

[0018] In a possible design, determining that the first cell is a serving cell of the terminal device includes determining that the first cell is a serving cell of the terminal device when the terminal device accesses the first cell in an idle mode or an inactive mode, or determining that the first cell is a serving cell of the terminal device when the terminal device is handed over to the first cell via a second type of cell handover.

[0019] In a possible design, the second type of cell handover is a cell level measurement based cell handover.

[0020] In a possible design, the first data transmission mode information or the second data transmission mode information includes at least one of first information, where the first information indicates whether to perform PDCP re-establishment, second information, where the second information indicates whether to perform PDCP data recovery, or third information, where the third information indicates whether to send a random access preamble to the target cell to obtain uplink synchronization information for the target cell.

[0021] In a possible design, the first type of cell handover is a cell handover based on beam level measurements.

[0022] According to a third aspect, an embodiment of the present application provides a communication method. The method may be applied to an access network device or a module in the access network device. An example in which the method is applied to the access network device is used. In the method, the access network device determines that a first cell among W cells is a serving cell of a terminal device, and the W cells further include a second cell. The access network device transmits, to a terminal device in a first cell, N sets of data transmission mode information for the terminal device, wherein the N sets of data transmission mode information include Q1 sets of data transmission mode information respectively corresponding to performing a handover of the terminal device from a cell in Q1 cell groups to the first cell via a first type of cell handover, and / or Q2 sets of data transmission mode information respectively corresponding to performing a handover of the terminal device from a cell in Q2 cell groups to a second cell via the first type of cell handover, wherein cells other than the first cell in W cells belong to the Q1 cell groups, and cells other than the second cell in W cells belong to the Q2 cell groups, and W, N, Q1, and Q2 are positive integers.

[0023] In a possible design, the first cell belongs to a first cell group among the Q2 cell groups, and the data transmission mode information corresponding to performing a handover of a terminal device from a cell in the first cell group to a second cell via a first type cell handover is third data transmission mode information.

[0024] In a possible design, after the terminal device is handed over from the first cell to the second cell via the first type of cell handover, the method further includes a step of sending eighth instruction information to the terminal device in the second cell, wherein the eighth instruction information instructs the terminal device to perform data transmission with the access network device based on third data transmission mode information in the N sets of data transmission mode information.

[0025] In a possible design, the method further includes receiving ninth indication information and tenth indication information from the terminal device in the second cell, where the ninth indication information indicates that the terminal device has been handed over from the first cell to the second cell via a first type cell handover, and the tenth indication information instructs the access network device to perform data transmission with the terminal device based on third data transmission mode information in the N sets of data transmission mode information.

[0026] According to a fourth aspect, an embodiment of the present application provides a communication method. The method may be applied to a terminal device or a module in the terminal device. An example in which the method is applied to the terminal device is used. In the method, the terminal device determines that a first cell among W cells is a serving cell of the terminal device, and the W cells further include a second cell. The terminal device receives N sets of data transmission mode information from the access network device in the first cell, the N sets of data transmission mode information including Q1 sets of data transmission mode information each corresponding to performing a handover of the terminal device from a cell in the Q1 cell group to the first cell via a first type of cell handover, and / or Q2 sets of data transmission mode information each corresponding to performing a handover of the terminal device from a cell in the Q2 cell group to a second cell via the first type of cell handover, wherein cells other than the first cell in the W cells belong to the Q1 cell group, and cells other than the second cell in the W cells belong to the Q2 cell groups, and W, N, Q1, and Q2 are positive integers.

[0027] In a possible design, the first cell belongs to a first cell group among the Q2 cell groups, and the data transmission mode information corresponding to performing a handover of a terminal device from a cell in the first cell group to a second cell via a first type cell handover is third data transmission mode information.

[0028] In a possible design, after the terminal device is handed over from the first cell to the second cell via the first type of cell handover, the method further includes a step of receiving eighth instruction information from the access network device in the second cell, wherein the eighth instruction information instructs the terminal device to perform data transmission with the access network device based on third data transmission mode information in the N sets of data transmission mode information.

[0029] In a possible design, the method further includes sending ninth instruction information and tenth instruction information to an access network device in the second cell, where the ninth instruction information indicates that the terminal device has been handed over from the first cell to the second cell via a first type of cell handover, and the tenth instruction information instructs the access network device to perform data transmission with the terminal device based on third data transmission mode information in the N sets of data transmission mode information.

[0030] According to a fifth aspect, an embodiment of the present application provides a communication method. The method may be applied to an access network device or a module within the access network device. An example in which the method is applied to the access network device is used. In the method, the access network device determines that a first cell among W cells is a serving cell for a terminal device, and transmits K sets of data transmission mode information for the terminal device to the terminal device in the first cell, where K is a positive integer. The K sets of data transmission mode information respectively correspond to K handover scenarios in which the terminal device is handed over between the W cells, and the K handover scenarios are determined according to whether the W cells belong to the same CU and / or the same DU.

[0031] In a possible design, the handover of the terminal device among the W cells is a first type of cell handover.

[0032] In a possible design, the W cells further include a second cell, and a handover scenario in which the terminal device is handed over from the first cell to the second cell via a first type cell handover is a first handover scenario, and the first handover scenario corresponds to third data transmission mode information in the K sets of data transmission mode information.

[0033] In a possible design, after the terminal device is handed over from the first cell to the second cell via the first type of cell handover, the method further includes a step of sending eighth instruction information to the terminal device in the second cell, wherein the eighth instruction information instructs the terminal device to perform data transmission with the access network device based on third data transmission mode information in the K sets of data transmission mode information.

[0034] In a possible design, the method further includes receiving ninth indication information and tenth indication information from the terminal device in the second cell, where the ninth indication information indicates that the terminal device has been handed over from the first cell to the second cell via a first type cell handover, and the tenth indication information instructs the access network device to perform data transmission with the terminal device based on third data transmission mode information in the K sets of data transmission mode information.

[0035] According to a sixth aspect, an embodiment of the present application provides a communication method. The method may be applied to a terminal device or a module within the terminal device. An example in which the method is applied to a terminal device is used. In the method, the terminal device determines that a first cell among W cells is a serving cell of the terminal device, and receives K sets of data transmission mode information from an access network device in the first cell, where K is a positive integer. The K sets of data transmission mode information respectively correspond to K handover scenarios in which the terminal device is handed over between the W cells, and the K handover scenarios are determined according to whether the W cells belong to the same CU and / or the same DU.

[0036] In a possible design, the handover of the terminal device among the W cells is a first type of cell handover.

[0037] In a possible design, the W cells further include a second cell, and a handover scenario in which the terminal device is handed over from the first cell to the second cell via a first type cell handover is a first handover scenario, and the first handover scenario corresponds to third data transmission mode information in the K sets of data transmission mode information.

[0038] In a possible design, after the terminal device is handed over from the first cell to the second cell via the first type of cell handover, the method further includes a step of receiving eighth instruction information from the access network device in the second cell, wherein the eighth instruction information instructs the terminal device to perform data transmission with the access network device based on third data transmission mode information in the N sets of data transmission mode information.

[0039] In a possible design, the method further includes sending ninth instruction information and tenth instruction information to an access network device in the second cell, where the ninth instruction information indicates that the terminal device has been handed over from the first cell to the second cell via a first type of cell handover, and the tenth instruction information instructs the access network device to perform data transmission with the terminal device based on third data transmission mode information in the N sets of data transmission mode information.

[0040] According to a seventh aspect, One embodiment of the present application provides a communication method.The method may be applied to an access network device or a module within the access network device. An example in which the method is applied to an access network device is used. In the method, the access network device determines that a first cell is a serving cell of a terminal device, and transmits cell group information of W cells to the terminal device in the first cell, where the W cells include the first cell. The cell group information is for determining a data transmission mode corresponding to performing a handover of the terminal device from one cell among the W cells to another cell among the W cells via a first type of cell handover, where W is an integer greater than 1.

[0041] According to the aforementioned method, the access network device can send cell group information of the W cells to the terminal device in the first cell, so that when the terminal device is subsequently handed over between the W cells, the terminal device can use a corresponding data transmission mode based on the cell group to which the cell in which the terminal device is located before the handover belongs and the cell group to which the cell in which the terminal device is located after the handover belongs, thereby effectively reducing the transmission resource consumption caused by the handover of the terminal device between the W cells, in other words, saving transmission resources.

[0042] In a possible design, the cell group information includes PDCP layer group information, the PDCP layer group information indicating at least one PDCP group, each of the at least one PDCP group including at least one of the W cells. When the one cell and another cell are not in the same PDCP group, the data transmission mode includes performing PDCP data recovery, or when the one cell and another cell are in the same PDCP group, the data transmission mode includes skipping performing PDCP data recovery.

[0043] In a possible design, the cell group information includes RLC layer group information, the RLC layer group information indicating at least one RLC group, each of the at least one RLC group including at least one of the W cells, and the data transmission mode includes performing RLC re-establishment when the one cell and another cell are not in the same RLC group, or skipping performing RLC re-establishment when the one cell and another cell are in the same RLC group.

[0044] In a possible design, the cell group information includes first MAC layer group information, the first MAC layer group information indicating at least one first MAC group, each of the at least one first MAC group including at least one of the W cells. When the one cell and the other cell are not in the same first MAC group, the data transmission mode includes performing random access, or when the one cell and the other cell are in the same first MAC group, the data transmission mode includes skipping performing random access.

[0045] In a possible design, the cell group information includes second MAC layer group information, the second MAC layer group information indicating at least one second MAC group, each of the at least one second MAC group including at least one of the W cells. When the one cell and the other cell are not in the same second MAC group, the data transmission mode includes performing a MAC reset, or when the one cell and the other cell are in the same second MAC group, the data transmission mode includes skipping performing a MAC reset.

[0046] In a possible design, the method further includes determining that at least one of the following conditions is met: the terminal device needs to enter an idle mode or an inactive mode; the terminal device needs to be handed over to a cell other than the W cells through a second type of cell handover; or the cell group information needs to be changed; and releasing the cell group information and / or instructing the terminal device to release the cell group information.

[0047] In a possible design, determining that the first cell is a serving cell of the terminal device includes determining that the first cell is a serving cell of the terminal device when the terminal device accesses the first cell in an idle mode or an inactive mode, or determining that the first cell is a serving cell of the terminal device when the terminal device is handed over to the first cell via a second type of cell handover.

[0048] According to an eighth aspect, an embodiment of the present application provides a communication method. The method may be applied to a terminal device or a module within the terminal device. An example in which the method is applied to a terminal device is used. In the method, the terminal device receives cell group information of W cells from an access network device in a first cell, where the W cells include the first cell. The terminal device determines, based on the cell group information, a data transmission mode corresponding to performing a handover of the terminal device from one cell among the W cells to another cell among the W cells via a first type of cell handover, where W is an integer greater than 1.

[0049] In a possible design, the cell group information includes PDCP layer group information, the PDCP layer group information indicating at least one PDCP group, each of the at least one PDCP group including at least one of the W cells. When the one cell and another cell are not in the same PDCP group, the data transmission mode includes performing PDCP data recovery, or when the one cell and another cell are in the same PDCP group, the data transmission mode includes skipping performing PDCP data recovery.

[0050] In a possible design, the cell group information includes RLC layer group information, the RLC layer group information indicating at least one RLC group, each of the at least one RLC group including at least one of the W cells, and the data transmission mode includes performing RLC re-establishment when the one cell and another cell are not in the same RLC group, or skipping performing RLC re-establishment when the one cell and another cell are in the same RLC group.

[0051] In a possible design, the cell group information includes MAC layer group information, where the MAC layer group information indicates at least one MAC group, each of the at least one MAC group including at least one of the W cells. When the one cell and the other cell are not in the same MAC group, the data transmission mode includes performing random access, or when the one cell and the other cell are in the same MAC group, the data transmission mode includes skipping performing random access.

[0052] In a possible design, the cell group information includes MAC layer group information, where the MAC layer group information indicates at least one MAC group, each of the at least one MAC group including at least one of the W cells. When the one cell and another cell are not in the same MAC group, the data transmission mode includes performing a MAC reset, or when the one cell and another cell are in the same MAC group, the data transmission mode includes skipping performing a MAC reset.

[0053] In a possible design, the method further includes determining that at least one of the following conditions is met: the terminal device needs to enter an idle mode or an inactive mode; the terminal device needs to be handed over to a cell other than the W cells through a second type of cell handover; or the cell group information needs to be changed; and releasing the cell group information and / or instructing the terminal device to release the cell group information.

[0054] In a possible design, determining that the first cell is a serving cell of the terminal device includes determining that the first cell is a serving cell of the terminal device when the terminal device accesses the first cell in an idle mode or an inactive mode, or determining that the first cell is a serving cell of the terminal device when the terminal device is handed over to the first cell via a second type of cell handover.

[0055] According to a ninth aspect, the present application provides a communication device. The communication device has functionality for implementing the first, third, fifth, or seventh aspects. For example, the communication device includes corresponding modules, units, or means for performing the operations of the first, third, fifth, or seventh aspects. The modules, units, or means may be implemented by software, hardware, or hardware executing corresponding software.

[0056] In a possible design, the communication device includes a processing unit and a communication unit. The communication unit may be configured to transmit and receive signals to implement communication between the communication device and another device. The processing unit may be configured to perform some internal operations of the communication device. Functions performed by the processing unit and the communication unit may correspond to operations in the first, third, fifth, or seventh aspects.

[0057] In a possible design, the communication device may include a processor coupled to a memory. The memory may store computer programs or instructions necessary to implement the functionality of the first, third, fifth, or seventh aspect. The processor may execute the computer programs or instructions stored in the memory. When the computer programs or instructions are executed, the communication device is enabled to implement the method of any one of the possible designs or implementations of the first, third, fifth, or seventh aspect.

[0058] In a possible design, a communication device includes a processor and a memory. The memory can store computer programs or instructions necessary to implement the functionality of the first, third, fifth, or seventh aspect. The processor can execute the computer programs or instructions stored in the memory. When the computer programs or instructions are executed, the communication device is enabled to implement the method of any one of the possible designs or implementations of the first, third, fifth, or seventh aspect.

[0059] In a possible design, a communications device includes a processor and an interface circuit, the processor configured to communicate with another device by using the interface circuit and to perform a method in any one of the possible designs or implementations of the first, third, fifth, or seventh aspect.

[0060] According to a tenth aspect, the present application provides a communication device. The communication device has a function implementing the second, fourth, sixth, or eighth aspect. For example, the communication device includes a corresponding module, unit, or means for performing the operations in the second, fourth, sixth, or eighth aspect. The function, unit, or means may be implemented by software, hardware, or hardware executing corresponding software.

[0061] In a possible design, the communication device includes a processing unit and a communication unit. The communication unit may be configured to transmit and receive signals to implement communication between the communication device and another device. For example, the communication unit may be configured to transmit system information to a terminal device. The processing unit may be configured to perform some internal operations of the communication device. Functions performed by the processing unit and the communication unit may correspond to operations in the second, fourth, sixth, or eighth aspects.

[0062] In a possible design, the communication device may include a processor, the processor coupled to a memory. The memory may store computer programs or instructions necessary to implement the functionality of the second, fourth, sixth, or eighth aspects. The processor may execute the computer programs or instructions stored in the memory. When the computer programs or instructions are executed, the communication device is enabled to implement the method of any one of the possible designs or implementations of the second, fourth, sixth, or eighth aspects.

[0063] In a possible design, the communication device includes a processor and a memory. The memory can store computer programs or instructions necessary to implement the functionality of the second, fourth, sixth, or eighth aspects. The processor can execute the computer programs or instructions stored in the memory. When the computer programs or instructions are executed, the communication device is enabled to implement the method of any one of the possible designs or implementations of the second, fourth, sixth, or eighth aspects.

[0064] In a possible design, the communication device includes a processor and an interface circuit, the processor configured to communicate with another device by using the interface circuit and to perform the method of any one of the possible designs or implementations of the second, fourth, sixth, or eighth aspects.

[0065] In the ninth and tenth aspects, it can be understood that the processor may be implemented by hardware or software. When the processor is implemented by hardware, the processor may be a logic circuit, an integrated circuit, etc. When the processor is implemented by software, the processor may be a general-purpose processor and is implemented by reading software code stored in a memory. In addition, there may be one or more processors and one or more memories. The memory may be integrated with the processor, or the memory and the processor may be located separately. In a specific implementation process, the memory and the processor may be integrated into one chip or located separately on different chips. The type of memory and the manner in which the memory and the processor are located are not limited in the embodiments of the present application.

[0066] According to an eleventh aspect, the present application provides a communication system. The communication system may include the communication device provided in the seventh aspect and the communication device provided in the eighth aspect.

[0067] According to a twelfth aspect, the present application provides a computer-readable storage medium, the computer storage medium storing computer-readable instructions, which, when read and executed by a computer, enable the computer to perform a method in any possible design of the first to eighth aspects.

[0068] According to a thirteenth aspect, the present application provides a computer program product, which, when read and executed by a computer, enables the computer to perform the method of any possible design of the first to eighth aspects.

[0069] According to a fourteenth aspect, the present application provides a chip, the chip including a processor, coupled to a memory, configured to read and execute a software program stored in the memory to implement a method in any possible design of the first to eighth aspects.

[0070] These and other aspects of the present application will become clearer and more easily understood in the description of the embodiments that follow. [Brief explanation of the drawings]

[0071] [Figure 1] 1 is a diagram of a communication system to which an embodiment of the present invention is applied; [Figure 2A] FIG. 1 is a diagram of a CU-DU split architecture according to an embodiment of the present application. [Figure 2B] FIG. 10 is a diagram of another CU-DU split architecture according to an embodiment of the present application. [Figure 3] 1 is a schematic flowchart corresponding to a communication method according to an embodiment of the present application; [Figure 4] FIG. 1 is a diagram of a continuous handover according to an embodiment of the present application. [Figure 5] 1 is a schematic flowchart corresponding to a communication method according to an embodiment of the present application; [Figure 6] 2 is a schematic flowchart corresponding to a communication method according to an embodiment of the present invention; [Figure 7] 1 is a schematic flowchart corresponding to a communication method according to an embodiment of the present application; [Figure 8] 1 is a schematic flowchart corresponding to a communication method according to an embodiment of the present application; [Figure 9] 1 is a possible exemplary block diagram of an apparatus according to an embodiment of the present application; [Figure 10] FIG. 2 is a diagram of the structure of an access network device according to one embodiment of the present technology. [Figure 11] FIG. 2 is a diagram of the structure of a terminal device according to an embodiment of the present application; DETAILED DESCRIPTION OF THE INVENTION

[0072] The following describes the technical solutions in the embodiments of the present application with reference to the accompanying drawings in the embodiments of the present application.

[0073] 1 is a diagram of a communication system to which an embodiment of the present invention can be applied. As shown in FIG. 1, the communication system 10 includes one or more access network devices 20 and one or more terminal devices 30. An interface between the access network devices and the terminal devices may be a Uu interface (also referred to as an air interface), and data transmission may be performed between the access network devices 20 and the terminal devices 30 via air interface resources. For example, the terminal device may be located within the communication coverage of one or more cells of the access network devices, and there may be one or more cells serving the terminal device. When there are multiple cells serving the terminal device, the terminal device may operate by using one or more transmission technologies such as carrier aggregation (CA), dual connectivity (DC), coordinated multipoint (CoMP) transmission, and multiple transmission and reception point (mTRP).

[0074] (1) Terminal Device A terminal device, also referred to as user equipment (UE), mobile station (MS), mobile terminal (MT), etc., is a device that provides a user with voice and / or data connectivity, such as a handheld device or an in-vehicle device with wireless connectivity. Currently, some examples of terminals include mobile phones, tablet computers, notebook computers, palmtops, 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, wireless terminals in smart homes, etc.

[0075] (2) Access Network Devices An access network device is a radio access network (RAN) node (or device) that connects terminals to a wireless network, and may also be referred to as a base station. Currently, some examples of RAN nodes are a NodeB (NodeB, NB), next-generation NodeB (gNB), transmission reception point (TRP), evolved NodeB (eNB), radio network controller (RNC), base station controller (BSC), base transceiver station (BTS), home base station (e.g., home evolved NodeB or home NodeB, HNB), baseband unit (BBU), wireless fidelity (Wifi) access point (AP), etc.

[0076] (3) Communication between terminal devices and access network devices Communication between a terminal device and an access network device follows a specific protocol layer structure. For example, the control plane protocol layer structure may include a radio resource control (RRC) layer, a packet data convergence protocol (PDCP) layer, a radio link control (RLC) layer, a media access control (MAC) layer, and a physical layer (PHY), while the user plane protocol layer structure may include a PDCP layer, an RLC layer, a MAC layer, and a physical layer. In a possible implementation, a service data adaptation protocol (SDAP) layer may be further included above the PDCP layer. The SDAP layer, the PDCP layer, the RLC layer, the MAC layer, and the physical layer may be collectively referred to as an access layer. For a specific description of the aforementioned protocol layers, please refer to the relevant technical specifications of the 3rd generation partnership project (3GPP).

[0077] Taking downlink data transmission as an example, downlink data may be correspondingly encapsulated at each layer of an access network device. Data received by a specific layer from its upper layer is regarded as the layer's service data unit (SDU), and becomes a protocol data unit (PDU) through layer encapsulation and is transmitted to the next layer. For example, data received from the SDAP layer by a PDCP layer entity may be referred to as a PDCP SDU. After encapsulating the PDCP SDU, the PDCP layer entity obtains a PDCP PDU and sends the PDCP PDU to the RLC layer. The PDCP PDU received by the RLC layer entity from the PDCP layer may be referred to as an RLC SDU. After encapsulating the RLC SDU, the RLC layer entity obtains an RLC PDU and sends the RLC PDU to the MAC layer.

[0078] From the perspective of the terminal device, after the physical layer of the terminal device receives the transport block from the access network device, the transport block may be sequentially submitted from the physical layer to higher layers and correspondingly decapsulated at each layer. In other words, the processing performed at each layer of the terminal device may be the reverse process of the processing performed at each layer of the access network device.

[0079] (4) CU-DU split architecture For example, in some possible network structures, an access network device may include one or more centralized units (CUs) and one or more distributed units (DUs). Multiple DUs may be centrally controlled by one CU. This architecture may be referred to as a CU-DU split architecture. For example, the interface between the CU and the DU may be referred to as an F1 interface. The control plane (CP) interface may be an F1-C interface, and the user plane (UP) interface may be an F1-U interface.

[0080] The processing functions of the CU and DU may be divided based on the protocol layers of the wireless network. For example, as shown in FIG. 2A , the functions of the PDCP layer and protocol layers above the PDCP layer are configured on the CU, and the functions of the protocol layers below the PDCP layer (e.g., the RLC layer and the MAC layer) are configured on the DU. It can be understood that the division of the processing functions of the CU and DU based on the protocol layer is merely an example, and the processing functions may alternatively be divided in another manner. For example, the functions of the protocol layers above the RLC layer are configured on the CU, and the functions of the RLC layer and protocol layers below the RLC layer are configured on the DU. In another example, the CU or DU may be divided into functions of more protocol layers. In another example, the CU or DU may be divided into partial processing functions of protocol layers. This is not limited to the embodiments of the present application.

[0081] Furthermore, the functions of the CU may be implemented by one entity or by different entities. For example, the functions of the CU may be further divided, specifically, the control plane and the user plane are divided and implemented by different entities, namely, a control plane CU entity (i.e., a CU-CP entity) and a user plane CU entity (i.e., a CU-UP entity), respectively. The CU-CP entity and the CU-UP entity may be coupled to a DU to jointly complete the functions of a RAN device. The interface between the CU-CP entity and the CU-UP entity may be an E1 interface, the interface between the CU-CP entity and the DU may be an F1-C interface, and the interface between the CU-UP entity and the DU may be an F1-U interface. One DU and one CU-UP may be connected to one CU-CP. Under the control of the same CU-CP, one DU may be connected to multiple CU-UPs, and one CU-UP may be connected to multiple DUs. Under the coordination of multiple CU-CPs, one CU-UP may alternatively be connected to multiple cooperating CU-CPs to improve the flexibility of the CU-CP. 2B is a diagram of the distribution of the air interface protocol stack. As shown in FIG. 2B, for both the user plane and the control plane, the air interface protocol stack may be that the RLC layer, the MAC layer, and the PHY layer are on the DU, and the PDCP layer and the protocol layer above the PDCP layer are on the CU.

[0082] 2A and 2B, it should be noted that signaling generated by the CU may be transmitted to the terminal device via the DU, or signaling generated by the terminal device may be transmitted to the CU via the DU. The DU may transparently transmit signaling to the terminal device or the CU by directly encapsulating the signaling in a protocol layer without parsing the signaling. In the following embodiments, when transmission of such signaling between the DU and the terminal device is involved, transmission or reception of signaling by the DU includes this scenario. For example, signaling in the RRC layer or the PDCP layer is finally processed into data in the physical layer and transmitted to the terminal device, or converted from received data in the physical layer. In this architecture, signaling in the RRC layer or the PDCP layer may be considered to be transmitted by the DU, or by the DU and the radio frequency device.

[0083] It can be understood that the number of access network devices and the number of terminal devices included in the communication system are not limited in the embodiments of this application. In addition, the communication system may further include other devices or network elements, such as core network devices or relay devices, in addition to the access network devices and the terminal devices. This is not limited in the embodiments of this application.

[0084] The communication system shown in FIG. 1 can support various radio access technologies (RATs). For example, the communication system shown in FIG. 1 may be a fourth-generation (4G) communication system (which may also be referred to as a long-term evolution (LTE) communication system), a fifth-generation (5G) communication system (which may also be referred to as a new radio (NR) communication system), a wireless fidelity (Wi-Fi) system, or a future-oriented evolved system. The communication systems and service scenarios described in the embodiments of the present application are intended to more clearly explain the technical solutions in the embodiments of the present application and do not constitute limitations on the technical solutions provided in the embodiments of the present application. Those skilled in the art can know that with the evolution of communication systems and the emergence of new service scenarios, the technical solutions provided in the embodiments of the present application can also be applied to similar technical problems.

[0085] In the following, relevant technical features in the embodiments of the present application will be described first, and it should be noted that these descriptions are intended to facilitate understanding of the embodiments of the present application, and should not be considered as limiting the scope of protection claimed in the present application.

[0086] 1. Cell Handover Types The cell handover may include a first type of cell handover and a second type of cell handover. The first type of cell handover is a cell handover implemented through layer 1 / layer 2 (abbreviated as layer 1 / layer 2 handover), i.e., a cell handover based on beam-level measurements. The second type of cell handover is a cell handover implemented through layer 3 (abbreviated as layer 3 handover), i.e., a cell handover based on cell-level measurements. Layer 1 may be the physical layer, layer 2 may be any one or more of the MAC layer, RLC layer, PDCP layer, or SDAP layer, and layer 3 may be the RRC layer. Note that layer 1 / layer 2 handover may also be understood as layer 1 handover and / or layer 2 handover. When layer 1 handover and layer 2 handover are in an AND relationship, operations related to the handover process are mainly performed by both layer 1 and layer 2. When Layer 1 handover and Layer 2 handover are ORed, the operations related to the handover process are mainly performed by Layer 1 or Layer 2. Because Layer 1 and Layer 2 are lower than the RRC layer (Layer 3) in the protocol stack, Layer 1 / Layer 2 handover is sometimes referred to as lower layer handover, lowest layer handover, or lower layer handover. The names of specific handover techniques are not limited in this application.

[0087] Furthermore, the layer 1 / layer 2 handover may include: (1) a cell handover triggered by an access network device based on beam level measurement results, e.g., the access network device makes a handover decision based on beam level measurement results reported by the terminal device and sends a layer 1 / layer 2 handover command to the terminal device to instruct the terminal device to perform the cell handover; and (2) a cell handover triggered by a terminal device based on beam level measurement results, also referred to as a layer 1 / layer 2 conditional handover (CHO), e.g., the terminal device makes a handover decision based on beam level measurement results and autonomously performs the cell handover when handover criteria are met, without the access network device needing to deliver a handover command. The handover criteria may be preconfigured by the access network device for the terminal device.

[0088] Similarly, Layer 3 handover may include (1) a cell handover triggered by an access network device based on cell-level measurements, and (2) a cell handover triggered by a terminal device based on cell-level measurements, also referred to as Layer 3 CHO.

[0089] Below, we briefly explain the cell level measurement results and the beam level measurement results.

[0090] The process by which a terminal device obtains beam-level measurement results may be as follows: The access network device transmits a reference signal in the direction of each beam of the cell. The reference signal may be a synchronization signal / physical broadcast channel block (SSB), a channel state information reference signal (CSI-RS), a sounding reference signal (SRS), or another possible reference signal. This is not specifically limited. The terminal device performs measurements based on the reference signal on a time-frequency resource indicated by the access network device. For example, the terminal device may obtain, through sampling, multiple temporary signal strengths in a certain period of time, which belong to the beam corresponding to the reference signal, and may weight the multiple obtained signal strengths to obtain measurement results for the corresponding beam. The cell-level measurement results may be obtained by performing filtering and weighting on the beam-level measurement results of the cell.

[0091] 2. Cell Handover Scenario As described above, an access network device may include one or more CUs and one or more DUs. For example, an access network device may include one CU and multiple DUs, and the multiple DUs may be centrally controlled by the CU, and each of the multiple DUs may include one or more cells. It may be understood that "a DU includes one or more cells" may also be expressed as "a DU manages or controls one or more cells," "one or more cells of a DU," or "one or more cells belong to a DU."

[0092] When a terminal device is handed over between different cells, there may be several specific handover scenarios. For example, the handover scenario may be obtained through classification based on the location relationship between the source cell and the target cell. The location relationship between the source cell and the target cell may be whether the source cell and the target cell belong to the same CU and / or the same DU. Three possible handover scenarios, namely, Scenario 1 to Scenario 3, are described herein.

[0093] Scenario 1: A terminal device is handed over from a cell of a DU to another cell of a DU. In other words, the source cell and target cell of the terminal device belong to the same DU.

[0094] Scenario 2: A terminal device is handed over from a cell of DU1 controlled by a CU to a cell of DU2 controlled by a CU. In this case, DU1 may be referred to as a source DU, and DU2 may be referred to as a target DU. In other words, the source cell and the target cell of the terminal device belong to different DUs controlled by the same CU.

[0095] Scenario 3: A terminal device is handed over from a cell of DU1 controlled by CU1 to a cell of DU3 controlled by CU2. In this case, CU1 may be referred to as a source CU, and CU2 may be referred to as a target CU. In other words, the source cell and the target cell of the terminal device belong to different DUs controlled by different CUs.

[0096] 3. PDCP Data Recovery When a terminal device needs to be handed over between DUs due to movement, for example, when it needs to be handed over from a source DU to a target DU, with respect to uplink data, if the uplink data sent by the terminal device to the source DU is not successfully transmitted, the PDCP layer entity of the terminal device needs to trigger retransmission. Specifically, the uplink data is retransmitted via the RLC layer entity corresponding to the target DU. As a result, after the target DU successfully receives the uplink data, the target DU can submit the data to the PDCP layer entity of the CU to ensure lossless transmission of the uplink data. Similarly, with respect to downlink data, if the downlink data sent by the CU to the terminal device via the source DU is not successfully transmitted, the downlink data can be retransmitted via the target DU to ensure lossless transmission of the downlink data.

[0097] In some handover scenarios, PDCP data recovery may include RLC re-establishment, in other words, performing PDCP data recovery may be understood to mean also performing RLC re-establishment. For example, RLC re-establishment may be discarding RLC SDUs, segments of SDUs, RLC PDUs, etc., as well as stopping and resetting all timers in the RLC layer. RLC maintenance may mean that RLC functions continue to run.

[0098] In some embodiments, "PDCP data recovery" may be replaced with another possible description, for example, "RLC re-establishment" or "PDCP data retransmission."

[0099] 4. PDCP re-establishment When a terminal device needs to be handed over between CUs due to movement, for example, when handed over from a source CU to a target CU, the anchor position of the PDCP layer changes, so PDCP key update needs to be performed. Regarding uplink data, if the uplink data transmitted by the terminal device to the source CU is not transmitted successfully, the PDCP layer of the terminal device triggers re-establishment. Specifically, after the uplink data is processed by using the key of the target CU, the uplink data is retransmitted via the RLC layer entity corresponding to the target DU associated with the target CU. As a result, after the target DU successfully receives the uplink data, the target DU can submit the data to the PDCP layer entity of the target CU to ensure lossless transmission of the uplink data. Similarly, regarding downlink data, if the downlink data transmitted by the source CU to the terminal device is not transmitted successfully, after the downlink data is processed by the target CU by using the PDCP layer key of the target CU, the downlink data can be retransmitted via the target DU associated with the target CU to ensure lossless transmission of the data.

[0100] It may be understood that "PDCP re-establishment" may be replaced with another possible description, for example, "PDCP key update." For example, PDCP re-establishment may be re-establishing a PDCP layer entity by using a new configuration, including discarding stored PDCP PDUs, stored PDCP SDUs, etc., by using an indicated key and encryption algorithm. PDCP discarding may be discarding stored PDCP PDUs, stored PDCP SDUs, etc. PDCP maintenance may mean that PDCP functions continue to run.

[0101] 5.Uplink synchronization information The uplink synchronization information may include an uplink timing advance (TA). In an orthogonal multiple access system, to ensure orthogonality of uplink transmissions and avoid intra-cell interference, the access network device requires that signals from different terminal devices originating from the same subframe but on different frequency domain resources arrive at the access network device at essentially aligned times. To ensure time synchronization at the receiving side (i.e., the access network device side), an uplink TA mechanism may be used, so that the access network device can control the times at which uplink signals from different terminal devices arrive at the access network device by controlling the uplink TA of each terminal device. From the terminal device side's perspective, the uplink TA is essentially a negative offset between the start time at which a downlink subframe is received and the time at which an uplink subframe is transmitted. Due to large transmission delays, terminal devices far away from the access network device need to transmit uplink data earlier than terminal devices close to the access network device.

[0102] For cell handover, in a possible implementation, the terminal device may transmit a random access preamble or an uplink reference signal (e.g., a sounding reference signal (SRS)) to acquire uplink synchronization information (e.g., an uplink TA) for the target cell.

[0103] For example, when or after a terminal device is handed over to a target cell, the terminal device can send a random access preamble or an uplink reference signal to an access network device in the target cell, so that the access network device can obtain an uplink TA through measurements based on the random access preamble or the uplink reference signal, and send a timing advance command to the terminal device by using a random access response message. Correspondingly, the terminal device may obtain an uplink TA based on the timing advance command.

[0104] In another example, before performing a cell handover, a terminal device may transmit a random access preamble or an uplink reference signal to an access network device in one or more candidate cells to acquire and store an uplink TA for the one or more candidate cells. For example, the one or more candidate cells may include cell 1, and the terminal device may transmit an access network preamble or an uplink reference signal to a random access device in cell 1 based on a specified periodicity to acquire and store an uplink TA for cell 1. The uplink TA for cell 1 stored by the terminal device may be the latest uplink TA for cell 1. Furthermore, when or after the terminal device is handed over to cell 1 (in this case, cell 1 is the target cell), the terminal device can use the stored uplink TA for cell 1 and does not need to transmit a random access preamble or an uplink reference signal to an access network device to acquire an uplink TA for cell 1.

[0105] In another possible implementation, the terminal device may alternatively not transmit a random access preamble or an uplink reference signal to acquire uplink synchronization information for the target cell. For example, in Scheme 1, the terminal device may use the uplink synchronization information for the source cell as the uplink synchronization information for the target cell. In Scheme 2, the terminal device receives a downlink reference signal of the target cell and estimates the difference between the uplink TA for the target cell and the uplink TA for the source cell based on the strength difference between the downlink reference signal received by the terminal device from the source cell and the downlink reference signal received by the terminal device from the target cell, or the time difference between the downlink reference signal received by the terminal device from the source cell and the downlink reference signal received by the terminal device from the target cell. Thus, the terminal device can derive the uplink TA for the target cell from the uplink TA for the source cell. It may be understood that in some possible solutions, time synchronization is required between the source cell and the target cell in Scheme 2, and specifically, the source cell and the target cell transmit downlink reference signals at the same time.

[0106] It can be understood that random access primarily involves the MAC layer. From the MAC layer perspective, MAC layer behavior can include reset (in other words, re-establishment), partial reset, and maintenance. For example, a MAC reset can be stopping all timers, initializing MAC layer state variables, or clearing the HARQ cache. MAC maintenance (no reset) can mean that MAC functions continue to run. A MAC partial reset may be continuing some of the timers to run and / or reserving some of the MAC state variables.

[0107] In one example, there is an association relationship between random access and MAC reset. Specifically, when a MAC reset is performed, the terminal device needs to acquire uplink synchronization information for the target cell through a random access process. When MAC maintenance is performed, the terminal device does not need to acquire uplink synchronization information for the target cell through a random access process. For example, the terminal device maintains the uplink synchronization information acquired in the source cell. When a MAC partial reset is performed, if the content related to the uplink synchronization information of the target cell is reset, the terminal device needs to acquire the uplink synchronization information of the target cell through a random access process, or if the content related to the uplink synchronization information of the target cell is not reset, the terminal device does not need to acquire the uplink synchronization information of the target cell through a random access process. In this case, the aforementioned "transmitting a random access preamble to acquire uplink synchronization information for the target cell" may be replaced with "MAC reset." The "uplink synchronization information for the target cell" may be replaced with another possible description, for example, "uplink TA for the target cell."

[0108] In another example, there is no association between random access and MAC reset (in other words, random access and MAC reset are decoupled). In this case, when a MAC reset is performed, random access may or may not be performed. Similarly, when MAC maintenance is performed, random access may or may not be performed. Similarly, when a MAC partial reset is performed, random access may or may not be performed.

[0109] 6.Data transmission mode information The data transmission mode information indicates a data transmission mode between the terminal device and the target cell that is applied after the terminal device is handed over to the target cell. The "data" in the "data transmission mode" may refer to data in a broad sense, for example, including service data, and may further include other possible information. There may be multiple data transmission modes. The data transmission modes are described below with reference to Example 1 and Example 2.

[0110] (1) Example 1 In Example 1, the data transmission mode may include at least one of: whether to perform PDCP re-establishment, whether to perform PDCP data recovery, or whether to transmit a random access preamble or an uplink reference signal to acquire uplink synchronization information of the target cell. Six possible data transmission modes are described herein.

[0111] Data transmission mode 1 includes skipping performing PDCP re-establishment, skipping performing PDCP data recovery, and skipping sending a random access preamble or an uplink reference signal to obtain uplink synchronization information for the target cell.

[0112] Data transmission mode 2 includes skipping performing PDCP re-establishment, skipping performing PDCP data recovery, and sending a random access preamble or an uplink reference signal to obtain uplink synchronization information for the target cell.

[0113] Data transmission mode 3 includes performing PDCP data recovery and transmitting a random access preamble or an uplink reference signal to obtain uplink synchronization information of the target cell.

[0114] Data transmission mode 4 includes performing PDCP re-establishment and sending a random access preamble or an uplink reference signal to acquire uplink synchronization information of the target cell.

[0115] Data transmission mode 5 includes performing PDCP data recovery and skipping sending a random access preamble or an uplink reference signal to acquire uplink synchronization information of the target cell.

[0116] Data transmission mode 6 includes performing PDCP re-establishment and skipping sending a random access preamble or an uplink reference signal to acquire uplink synchronization information of the target cell.

[0117] It can be understood that the same data transmission mode can include one of "performing PDCP re-establishment" and "performing PDCP data recovery." In other words, at most one of "PDCP re-establishment" and "PDCP data recovery" is performed simultaneously. When a specific data transmission mode includes "performing PDCP re-establishment," it means "skipping performing PDCP data recovery." When a specific data transmission mode includes "performing PDCP data recovery," it means "skipping performing PDCP re-establishment." When a specific data transmission mode includes "skipping performing PDCP data recovery" and "skipping performing PDCP re-establishment," the data transmission mode can be understood as performing "PDCP maintenance." An implementation form of "including skipping performing PDCP data recovery" is that the data transmission mode information does not include an indication of PDCP data recovery. An implementation form of "including skipping performing PDCP re-establishment" is that the data transmission mode information does not include an indication of PDCP re-establishment. For a description of the behavior of other protocol layers below, please refer to the aforementioned implementation forms. In other words, an implementation form of skipping performing the X behavior is that the data transmission mode information does not include an instruction to perform the X behavior, or the data transmission mode information does not instruct to perform the X behavior. The "transmitting a random access preamble or an uplink reference signal to obtain uplink synchronization information for the target cell" included in the above data transmission mode may mean that when the terminal device is handed over to the target cell, the terminal device transmits a random access preamble or an uplink reference signal to the access network device to obtain uplink synchronization information for the target cell. Alternatively, before the terminal device is handed over to the target cell, the terminal device transmits a random access preamble or an uplink reference signal to the access network device to obtain uplink synchronization information for the target cell. For details, please refer to the above description.The phrase "skipping transmitting a random access preamble or an uplink reference signal to obtain uplink synchronization information for the target cell" included in the aforementioned data transmission mode may be replaced with "using uplink synchronization information for the source cell as uplink synchronization information for the target cell," "using uplink synchronization information for the target cell calculated by the terminal device," or "random access free handover."

[0118] In addition, there may be multiple implementation forms in which the data transmission mode information indicates a data transmission mode. For example, the data transmission mode information may include at least one of first information, second information, or third information. The first information indicates whether to perform PDCP reestablishment, the second information indicates whether to perform PDCP data recovery, and the third information indicates whether to transmit a random access preamble or an uplink reference signal to acquire uplink synchronization information for the target cell. For example, the data transmission mode information may alternatively not include the third information. In this case, if the configuration information for the target cell transmitted by the access network device to the terminal device includes configuration information for random access resources or uplink reference signals, the terminal device is implicitly instructed to transmit a random access preamble or an uplink reference signal to acquire uplink synchronization information for the target cell. Alternatively, if the configuration information for the target cell transmitted by the access network device to the terminal device does not include configuration information for random access resources or uplink reference signals, the terminal device is implicitly instructed not to transmit a random access preamble or an uplink reference signal to acquire uplink synchronization information for the target cell.

[0119] (2) Example 2 In Example 2, the data transmission mode may include at least one of PDCP layer behavior, RLC layer behavior, or MAC layer behavior. Specifically, different data transmission modes can be designed based on the behavior of different protocol layers. (1) PDCP layer behavior for a data radio bearer (DRB) includes re-establishment, data recovery, and maintenance. PDCP layer behavior for a signaling radio bearer (SRB) includes re-establishment, maintenance, and teardown. (2) RLC layer behavior includes re-establishment and maintenance (without re-establishment). (3) MAC layer behavior includes reset, partial reset, and maintenance (without reset). In a possible implementation, the PDCP layer behavior, RLC layer behavior, and MAC layer behavior can be combined to obtain multiple data transmission modes. For example, the data transmission mode obtained through the combination can include data transmission mode A, data transmission mode B, etc., and examples are not listed herein.

[0120] Data transmission mode A: PDCP re-establishment, RLC re-establishment, and MAC reset (corresponding to data transmission mode 4 above).

[0121] Data transmission mode B: PDCP data recovery, RLC re-establishment, and MAC reset (corresponding to data transmission mode 3 above).

[0122] It should be understood that in the description of the data transmission mode, the description of MAC layer behavior and the description of the behavior of whether to perform a random access process may be replaced with each other. For example, "MAC reset" may be replaced with "performing random access," and "MAC maintenance" may be replaced with "skip performing random access." Alternatively, the description of MAC layer behavior and the description of the behavior of whether to perform a random access process may coexist. For example, if both descriptions are present, "MAC reset" in the data transmission mode may be replaced with "MAC reset must be performed and random access must be initiated."

[0123] 7. Relationship between handover scenarios and data transmission modes For example, there may be a correspondence between handover scenarios and data transmission modes.

[0124] For example, scenario 1 may correspond to data transmission mode 1. In other words, when the source cell and target cell of a terminal device belong to the same DU, after the terminal device is handed over to the target cell, PDCP re-establishment may not be performed, PDCP data recovery may not be performed, and a random access preamble or an uplink reference signal may not be transmitted to obtain uplink synchronization information for the target cell. The reason is as follows: Because the source cell and target cell belong to the same DU, for a service used by the terminal device, the PDCP layer entity and RLC layer entity corresponding to the service do not need to be re-established. After the terminal device is handed over to the target cell, the terminal device may continue to transmit data of the service via the previous PDCP layer entity and RLC layer entity. In addition, because the source cell and target cell belong to the same DU, specifically, because the source cell and target cell are located at the same physical location, the uplink synchronization information for the source cell is the same as the uplink synchronization information for the target cell. Therefore, the terminal device may use the uplink synchronization information for the source cell as the uplink synchronization information for the target cell.

[0125] As another example, scenario 2 may correspond to data transmission mode 3. In other words, when the source cell and target cell of a terminal device belong to different DUs controlled by the same CU, after the terminal device is handed over to the target cell, PDCP data recovery may be performed, and a random access preamble or an uplink reference signal may be transmitted to acquire uplink synchronization information for the target cell. The reason is as follows: Because the source cell and the target cell belong to different DUs controlled by the same CU, for a service used by the terminal device, the PDCP layer entity corresponding to the service does not need to be re-established, but the RLC layer entity corresponding to the service needs to be re-established. After the terminal device is handed over to the target cell, the terminal device can transmit data for the service via the previous PDCP layer entity and the re-established RLC layer entity. In addition, because the source cell and the target cell belong to different DUs and may be deployed in different physical locations, the uplink synchronization information for the source cell may differ from the uplink synchronization information for the target cell. Therefore, the terminal device needs to transmit a random access preamble or an uplink reference signal to acquire uplink synchronization information for the target cell.

[0126] As another example, scenario 3 may correspond to data transmission mode 4. That is, when the source cell and target cell of a terminal device belong to different DUs controlled by different CUs, PDCP re-establishment is performed after the terminal device is handed over to the target cell, and a random access preamble or an uplink reference signal is transmitted to acquire uplink synchronization information for the target cell. The reason is as follows: Because the source cell and the target cell belong to different DUs controlled by different CUs, for the service used by the terminal device, a PDCP layer entity corresponding to the service needs to be re-established. After the terminal device is handed over to the target cell, the terminal device may transmit data for the service through the re-established PDCP layer entity. In addition, because the source cell and the target cell belong to different DUs and may be located in different physical locations, the terminal device needs to transmit a random access preamble or an uplink reference signal to acquire uplink synchronization information for the target cell.

[0127] It can be understood that the above-mentioned correspondence between handover scenarios and data transmission modes is a possible example. In the embodiment of the present application, the following example is used for explanation, but other possible correspondences are not excluded. For example, scenario 1 may correspond to data transmission mode 2, or scenario 2 may correspond to data transmission mode 1.

[0128] Based on the foregoing description of the relevant technical features, handover of a terminal device between different cells is considered in the embodiments of the present application.

[0129] Referring to FIG. 3, the following uses Layer 1 / Layer 2 handover as an example to describe the communication method provided in the embodiments of the present application.

[0130] 3 is a schematic flowchart corresponding to a communication method according to an embodiment of the present application. As shown in FIG. 3, the method includes the following steps:

[0131] S301: An access network device to which a source cell belongs obtains M sets of data transmission mode information for a terminal device, the M sets of data transmission mode information including data transmission mode information respectively corresponding to handovers of the terminal device from the source cell to M candidate cells, where M is a positive integer.

[0132] For example, an access network device to which a source cell belongs can obtain configuration information of M candidate cells for a terminal device. Using one of the candidate cells as an example, the configuration information for the candidate cell includes data transmission mode information corresponding to handover of the terminal device from the source cell to the candidate cell. Optionally, the configuration information for the candidate cell may further include related information of the candidate cell and configuration information for the terminal device in the candidate cell.

[0133] The related information of the candidate cell may include at least one of the following: reference signal configuration information of the candidate cell (e.g., SSB configuration information, CSI-RS configuration information, or SRS configuration information), beam measurement configuration information of the candidate cell, e.g., transmission configuration indicator (TCI) state configuration information, or physical cell identity (PCI) of the candidate cell.

[0134] The configuration information for the terminal device in the candidate cell may include at least one of physical layer channel configuration information for the terminal device in the candidate cell or a cell-radio network temporary identifier (C-RNTI) allocated to the terminal device by the candidate cell. The physical layer channel includes, for example, a physical downlink control channel (PDCCH), a physical downlink shared channel (PDSCH), a physical uplink control channel (PUCCH), or a physical uplink shared channel (PUSCH).

[0135] The data transmission mode information corresponding to the handover of the terminal device from the source cell to the candidate cell may be determined based on a handover scenario in which the terminal device is handed over from the source cell to the candidate cell. For example, if the handover scenario in which the terminal device is handed over from the source cell to the candidate cell is the above-mentioned scenario 1, the data transmission mode information corresponding to the handover of the terminal device from the source cell to the candidate cell may indicate data transmission mode 1. In another example, if the handover scenario in which the terminal device is handed over from the source cell to the candidate cell is the above-mentioned scenario 2, the data transmission mode information corresponding to the handover of the terminal device from the source cell to the candidate cell may indicate data transmission mode 3.

[0136] It may be understood that the source cell and the candidate cell may belong to the same access network device or to different access network devices. When the source cell and the candidate cell belong to different access network devices, the access network device to which the source cell belongs may obtain configuration information for the candidate cell from the access network device to which the candidate cell belongs via an Xn interface.

[0137] S302: The access network device to which the source cell belongs sends M sets of data transmission mode information to the terminal device, and the terminal device correspondingly receives the M sets of data transmission mode information.

[0138] For example, the access network device to which the source cell belongs may send an RRC message to the terminal device, where the RRC message includes configuration information for M candidate cells, and the configuration information for the M candidate cells includes M sets of data transmission mode information.

[0139] In some cases, the method may further include S303-a to S307-a (ie, handover mode 1), or may include S303-b to S306-b (ie, handover mode 2).

[0140] S303-a: The terminal device performs beam level measurement on the source cell and the candidate cell to obtain beam level measurement results, and reports the beam level measurement results to the access network device to which the source cell belongs.

[0141] S304-a: The access network device to which the source cell belongs sends a layer 1 / layer 2 handover command to the terminal device based on the beam level measurement result, and the handover command instructs the terminal device to be handed over from the source cell to the target cell. In response, the terminal device receives the handover command and is handed over from the source cell to the target cell based on the handover command.

[0142] Herein, the target cell may be selected from the M candidate cells based on beam level measurements by the access network device to which the source cell belongs. The Layer 1 handover command may be downlink control information (DCI) carried on the PDCCH, and the Layer 2 handover command may be a MAC control element (CE).

[0143] The handover command may include identification information of the target cell and target beam information to be used by the terminal device in the target cell. The identification information of the target cell may be, for example, the PCI of the target cell. The target beam information may include, for example, identification information of the TCI state, in other words, the target beam may be indicated by the TCI state.

[0144] S305-a: The terminal device sends uplink information (or an acknowledgment command for the handover command) to the access network device to which the target cell belongs, and the uplink information notifies the access network device that the terminal device has been handed over from the source cell to the target cell.

[0145] In this specification, the uplink information may be a Layer 1 / Layer 2 acknowledgement (ACK), or may be uplink data or signaling, such as a scheduling request (SR), transmitted by the terminal device to the target cell.

[0146] For example, in a possible manner, the uplink information may include the identity of the source cell, e.g., the PCI of the source cell. Optionally, the uplink information may further include the identity of the terminal device, e.g., the C-RNTI. The C-RNTI may be configured by the target cell for the terminal device. In this way, after receiving the uplink information, the access network device to which the target cell belongs may identify the terminal device based on the identity of the terminal device and may identify the source cell of the terminal device based on the PCI of the source cell. This explicitly indicates the terminal device and the source cell. In another possible manner, after selecting the target cell based on the beam level measurement result, the access network device to which the source cell belongs may communicate with the access network device to which the target cell belongs, for example, may confirm with the access network device to which the target cell belongs whether the terminal device is allowed to be handed over to the target cell. Correspondingly, if the terminal device is allowed to be handed over to the target cell, the access network device to which the target cell belongs may allocate a first physical resource to the terminal device and notify the terminal device of the first physical resource via the source cell. Furthermore, the terminal device can transmit uplink information to the access network device to which the target cell belongs on the first physical resource. In this way, after receiving the uplink information on the first physical resource, the access network device to which the target cell belongs can identify the terminal device and the source cell of the terminal device based on the first physical resource. In this way, the terminal device and the source cell are implicitly indicated.

[0147] For example, after the terminal device is handed over from the source cell to the target cell, the terminal device may release M sets of data transmission mode information. Optionally, the terminal device may further release other information, for example, configuration information for the terminal device in the M candidate cells.

[0148] In a possible implementation, the terminal device may further send an acknowledgement command for the handover command to the access network device to which the source cell belongs to indicate that the handover command has been successfully received.

[0149] S306-a: The access network device to which the terminal device and the target cell belong performs data transmission based on data transmission mode information corresponding to handover of the terminal device from the source cell to the target cell.

[0150] S307-a: The access network device to which the target cell belongs sends a notification message to the access network device to which the source cell belongs, where the notification message notifies the access network device to which the source cell belongs to release M sets of data transmission mode information for the terminal device. Correspondingly, the access network device to which the source cell belongs can release the M sets of data transmission mode information for the terminal device based on the notification message. In this specification, if the access network device to which the target cell belongs and the access network device to which the source cell belongs are the same access network device, the notification message does not need to be transmitted.

[0151] Optionally, the access network device to which the source cell belongs may further release other related information for the terminal device, for example, configuration information for the terminal device in the M candidate cells.

[0152] In this embodiment of the present application, the terminal device or access network device to which the source cell belongs "releasing M sets of data transmission mode information for the terminal device" can be understood as the terminal device or access network device to which the source cell belongs "deleting M stored sets of data transmission mode information for the terminal device."

[0153] S303-b: The terminal device performs beam level measurement on the source cell and the candidate cell to obtain beam level measurement results, and determines to be handed over from the source cell to the target cell based on the beam level measurement results.

[0154] In this specification, the terminal device may trigger a cell handover, i.e., a layer 1 / layer 2 CHO, based on the beam level measurement result. In this case, in S302, the access network device may further send a handover criterion for the layer 1 / layer 2 CHO to the terminal device, so that the terminal device may trigger a cell handover based on the beam level measurement result and the handover criterion. For example, the handover criterion for the layer 1 / layer 2 CHO may be that a handover to the candidate cell may be performed when the channel quality of the candidate cell is better than the channel quality of the source cell.

[0155] S304-b: The terminal device sends handover completion information to the access network device to which the target cell belongs, where the handover completion information notifies the access network device that the terminal device has been handed over from the source cell to the target cell.

[0156] In a possible implementation, the handover completion information may be a random access preamble or an uplink reference signal transmitted by the terminal device to the target cell, in which case the access network device to which the target cell belongs can know the identifier of the source cell of the terminal device by using message 3 in the random access process or another possible message.

[0157] In another possible implementation, the handover completion information may alternatively be a Layer 1 / Layer 2 command. In this case, the handover completion information may include the identifier of the source cell. Alternatively, the access network device to which the target cell belongs may know the identifier of the source cell of the terminal device by using Message 3 in the random access process or another possible message.

[0158] For example, after the terminal device is handed over from the source cell to the target cell, the terminal device may release M sets of data transmission mode information.

[0159] S305-b: The access network device to which the terminal device and the target cell belong performs data transmission based on data transmission mode information corresponding to handover of the terminal device from the source cell to the target cell.

[0160] S306-b: The access network device to which the target cell belongs sends a notification message to the access network device to which the source cell belongs, where the notification message notifies the access network device to which the source cell belongs to release M sets of data transmission mode information for the terminal device. Correspondingly, the access network device to which the source cell belongs can release the M sets of data transmission mode information for the terminal device based on the notification message.

[0161] It can be understood that S303-a to S307-a are cell handovers triggered by an access network device based on beam level measurement results, and S303-b to S306-b are cell handovers triggered by a terminal device based on beam level measurement results. Similar steps in S303-a to S307-a and S303-b to S306-b can be referenced to each other.

[0162] According to the method shown in FIG. 3, the access network device to which the source cell belongs can send M sets of data transmission mode information to the terminal device, respectively corresponding to handover of the terminal device from the source cell to the M candidate cells, so that after the terminal device is handed over to the target cell (i.e., a specific candidate cell), the access network device to which the terminal device and the target cell belong can perform data transmission based on the data transmission mode information corresponding to handover of the terminal device from the source cell to the target cell.

[0163] However, considering that a terminal device may successively perform multiple layer 1 / layer 2 handovers between multiple cells, as shown in Figure 4, after the terminal device is handed over from a first cell to a second cell, the terminal device may be handed over from the second cell to a third cell. In this case, according to the method shown in Figure 3, during each handover of the terminal device, the access network device to which the source cell belongs needs to send, to the terminal device, data transmission mode information corresponding to the handover of the terminal device from the source cell to the candidate cell (for example, when the terminal device is handed over from the first cell to the second cell, the first cell is used as the source cell, and the access network device to which the first cell belongs needs to send, to the terminal device, data transmission mode information corresponding to the handover from the first cell to the candidate cell; when the terminal device is handed over from the second cell to the third cell, the second cell is used as the source cell, and the access network device to which the second cell belongs needs to send, to the terminal device, data transmission mode information corresponding to the handover from the second cell to the candidate cell). This results in high transmission resource overhead.

[0164] An embodiment of the present application provides another communication method. The communication method may include: after determining that a first cell is a serving cell of a terminal device, an access network device may send N sets of data transmission mode information to the terminal device in the first cell, where N is a positive integer; the N sets of data transmission mode information include first data transmission mode information corresponding to a handover of the terminal device from the second cell to the first cell and / or second data transmission mode information corresponding to a handover of the terminal device from the second cell to a third cell. In other words, the access network device can send multiple data transmission mode information sets corresponding to handover of the terminal device between different cells to the terminal device in the source cell (this is different from Figure 3 in which the access network device sends data transmission mode information corresponding to handover from the current source cell to the candidate cell, i.e., data transmission mode information corresponding to handover of the terminal device from the first cell to the second cell or the third cell to the terminal device in the source cell), so that the terminal device can directly use the corresponding data transmission mode information when performing successive handovers between different cells to effectively save transmission resources.

[0165] The method will be described in detail below with reference to Embodiments 1 to 3. The data transmission mode in Embodiments 1 to 3 may be the data transmission mode described in Example 1 above.

[0166] Embodiment 1 5 is a schematic flowchart corresponding to the communication method according to Embodiment 1 of the present invention. As shown in FIG. 5, the method includes the following steps:

[0167] S501: An access network device determines that a first cell is a serving cell of a terminal device.

[0168] In this specification, there may be multiple cases in which an access network device determines a first cell as a serving cell of a terminal device. For example, in case 1, when a terminal device accesses the first cell in an idle mode or an inactive mode, the access network device may determine that the first cell is a serving cell of the terminal device. In another example, in case 2, when a terminal device is handed over to the first cell from another cell through a layer 3 handover, the access network device may determine that the first cell is a serving cell of the terminal device.

[0169] It can be understood that S501 is described from the perspective of an access network device. From the perspective of a terminal device, in the above case 1 or case 2, the terminal device may also determine that the first cell is the serving cell of the terminal device.

[0170] For example, an access network device may include one CU and one or more DUs, e.g., DU1 and DU2.

[0171] S502: The access network device sends N sets of data transmission mode information to a terminal device in a first cell. In response, the terminal device can receive the N sets of data transmission mode information. Furthermore, the access network device and the terminal device can store the N sets of data transmission mode information.

[0172] For example, before S502, the access network device may determine W cells for the terminal device, and then determine N sets of data transmission mode information based on the W cells. The W cells include a current source cell (i.e., a first cell) and one or more candidate cells for the terminal device. The terminal device may perform a layer 1 / layer 2 handover among the W cells. That is, the W cells include cells for the terminal device to perform a layer 1 / layer 2 handover. For example, all W cells may be cells managed by the access network device, in other words, the W cells belong to the access network device. For example, the W cells may belong to one or more DUs of the access network device. W is an integer greater than 1, and the specific number of W cells is not limited in the embodiments of the present application.

[0173] The access network device can determine W cells in multiple implementations. In a possible implementation, the access network device can configure neighbor cell measurement information for a terminal device in a first cell. The neighbor cell measurement information may include a measurement configuration and a reporting configuration for at least one neighbor cell of the first cell. In this manner, the terminal device may measure neighbor cells of the first cell based on the neighbor cell measurement information and report measurement results (e.g., cell-level measurement results or beam-level measurement results). Correspondingly, the access network device can determine W cells based on the measurement results reported by the terminal device. For example, if the measurement results are cell-level measurement results, the W cells may include the first cell and one or more neighbor cells whose cell-level measurement results are equal to or greater than a first threshold. In another example, if the measurement results are beam-level measurement results, the W cells may include the first cell and one or more neighbor cells, and any one of the one or more neighbor cells includes a beam whose measurement results are equal to or greater than a second threshold. The first threshold or the second threshold may be set based on actual requirements. This is not specifically limited. In another possible implementation, the access network device may determine the W cells based on a radio resource management algorithm. For example, the access network device may obtain historical movement trajectory information of the terminal device, determine a list of cells to which the terminal device is frequently handed over based on the historical movement trajectory information, and determine the W cells based on the list of cells to which the terminal device is frequently handed over.

[0174] With reference to implementation form 1 and implementation form 2, the following describes a specific implementation form in which the access network device sends N sets of data transmission mode information to the terminal device using an example in which the W cells include a first cell, a second cell, and a third cell (the first cell and the second cell belong to DU1 controlled by the CU, and the third cell belongs to DU2 controlled by the CU).

[0175] (1) Implementation form 1 The N sets of data transmission mode information for the terminal device include W-1 sets of data transmission mode information, each corresponding to performing a handover of the terminal device from W-1 cells other than the i-th cell among the W cells to the i-th cell through a layer 1 / layer 2 handover, where the i-th cell may be any one of the W cells.

[0176] For example, the W cells include a first cell, a second cell, and a third cell, where the first cell and the second cell belong to DU1 controlled by the CU, and the third cell belongs to DU2 controlled by the CU. In this case, the N sets of data transmission mode information for the terminal device may include at least one of the following (1), (2), and (3):

[0177] (1) P1 sets of data transmission mode information, each corresponding to a handover of a terminal device from P1 cells (i.e., the second cell and the third cell) other than the first cell among the W cells to the first cell by layer 1 / layer 2 handover. For example, the P1 sets of data transmission mode information include data transmission mode information a1 corresponding to a handover of a terminal device from the second cell to the first cell by layer 1 / layer 2 handover (i.e., scenario 1), and data transmission mode information a2 corresponding to a handover of a terminal device from the third cell to the first cell by layer 1 / layer 2 handover (i.e., scenario 2). The data transmission mode information a1 may indicate data transmission mode 1 corresponding to scenario 1, and the data transmission mode information a2 may indicate data transmission mode 3 corresponding to scenario 2.

[0178] (2) P2 sets of data transmission mode information, each corresponding to performing a handover of a terminal device by layer 1 / layer 2 handover from P2 cells (i.e., the first cell and the third cell) other than the second cell among the W cells to the second cell. For example, the P2 sets of data transmission mode information include data transmission mode information a3 corresponding to performing a handover of a terminal device by layer 1 / layer 2 handover from the first cell to the second cell (i.e., scenario 1), and data transmission mode information a4 corresponding to performing a handover of a terminal device by layer 1 / layer 2 handover from the third cell to the second cell (i.e., scenario 2). The data transmission mode information a3 may indicate data transmission mode 1 corresponding to scenario 1, and the data transmission mode information a4 may indicate data transmission mode 3 corresponding to scenario 2.

[0179] (3) P3 sets of data transmission mode information, each corresponding to performing a handover of a terminal device from P3 cells (i.e., the first cell and the second cell) other than the third cell among the W cells to the third cell through layer 1 / layer 2 handover. For example, the P3 sets of data transmission mode information include data transmission mode information a5 corresponding to performing a handover of a terminal device from the first cell to the third cell through layer 1 / layer 2 handover (i.e., scenario 2) and data transmission mode information a6 corresponding to performing a handover of a terminal device from the second cell to the third cell through layer 1 / layer 2 handover (i.e., scenario 2). The data transmission mode information a5 may indicate data transmission mode 3 corresponding to scenario 2, and the data transmission mode information a6 may indicate data transmission mode 3 corresponding to scenario 2.

[0180] P1, P2, and P3 are positive integers. When W=3, P1=P2=P3=2.

[0181] For implementation 1, at S502, the access network device may send an RRC message to a terminal device in a first cell, where the RRC message includes configuration information for W cells, and the configuration information for the W cells includes N sets of data transmission mode information. For example, the configuration information for the first cell may include associated information of the first cell, configuration information for terminal devices in the first cell, and P1 sets of data transmission mode information. The configuration information for the second cell includes associated information of the second cell, configuration information for terminal devices in the second cell, and P2 sets of data transmission mode information. The configuration information for the third cell includes associated information of the third cell, configuration information for terminal devices in the third cell, and P3 sets of data transmission mode information. In a CU-DU split network architecture, a possible manner of generating configuration information for the first cell is as follows: DU1 generates configuration information for the first cell (excluding the P1 sets of data transmission mode information) and sends the configuration information to the CU. The CU generates P1 sets of data transmission mode information, combines it with the configuration information for the first cell received from DU1 (excluding the P1 sets of data transmission mode information) to generate complete configuration information for the first cell, and sends the complete configuration information to the terminal device. For the manner of generating the configuration information of the second cell and the third cell, please refer to the manner of generating the configuration information of the first cell. Details will not be described in this specification.

[0182] In another possible implementation, each set of data transmission mode information may be divided into two parts, denoted as a first part and a second part. The access network device notifies the terminal device of the first part through step S502 and the second part through step S504-a. Using the configuration information for the first cell as an example, the data transmission mode of the handover from the second cell to the first cell is data transmission mode 1, which specifically skips performing PDCP re-establishment, skips performing PDCP data recovery, and skips transmitting a random access preamble or an uplink reference signal to acquire uplink synchronization information for the target cell. Data transmission mode 1 is divided into a first part and a second part. The first part includes "skipping performing PDCP re-establishment and skipping performing PDCP data recovery," and the second part includes "skipping transmitting a random access preamble or an uplink reference signal to acquire uplink synchronization information for the target cell." In the CU-DU split network architecture, the first part of the information is notified to the terminal device by the CU using an RRC message, and the second part of the information is notified to the terminal device by the DU using a Layer 1 / Layer 2 handover command. In this way, the DU to which the source cell belongs needs to sense the second part of the information; in other words, the CU needs to notify the DU of the second part of the information, or the DU autonomously determines the second part of the information based on the status of the UE (e.g., the DU may determine that the TAs for the source cell and the target cell are similar and may not send a random access preamble to reacquire uplink synchronization information for the target cell, but may still use the TA for the source cell in the target cell).The advantage of dividing into two parts is that relatively static behavior, for example, information about whether PDCP re-establishment needs to be performed, can be pre-configured for the terminal device through S502, and relatively dynamic behavior, for example, whether the terminal device needs to initiate an access network process during handover (or whether the terminal device should transmit a random access preamble or an uplink reference signal to acquire uplink synchronization information for the target cell), which the random access device cannot determine in advance, can be determined before the access network device executes S504-a, so that an appropriate data transmission mode for the terminal can be more accurately selected and the reliability of handover can be improved.

[0183] In addition, in this embodiment, using the first cell as an example, P1 sets of configuration information and data transmission mode information for the terminal device in the first cell may be collectively referred to as context information for the terminal device in the first cell.

[0184] (2) Implementation form 2 The N sets of data transmission mode information for the terminal device include j sets of data transmission mode information, each corresponding to performing a handover of the terminal device from a cell in the j cell group to the i-th cell via Layer 1 / Layer 2 handover, where the i-th cell may be any cell in the W cells, and cells other than the i-th cell in the W cells belong to the j cell group, and j is a positive integer.

[0185] For example, the W cells include a first cell, a second cell, and a third cell, and the N sets of data transmission mode information for the terminal device may include at least one of the following (1), (2), and (3):

[0186] (1) Q1 sets of data transmission mode information, each corresponding to performing a handover of a terminal device from a cell in Q1 cell groups to a first cell through Layer 1 / Layer 2 handover, where cells other than the first cell in W cells belong to Q1 cell groups, where Q1 is a positive integer.

[0187] For example, the Q1 cell groups may be obtained by dividing the W cells according to whether the cells other than the first cell and the first cell belong to the same DU and / or the same CU. For example, if the second cell and the first cell belong to different DUs controlled by the same CU, and the third cell and the first cell belong to different DUs controlled by the same CU, the second cell and the third cell belong to the same cell group. In another example, if the second cell and the first cell belong to the same DU, and the third cell and the first cell belong to different DUs, the second cell and the third cell belong to different cell groups. Alternatively, if the handover scenario in which the terminal device is handed over from the second cell to the first cell is the same as the handover scenario in which the terminal device is handed over from the third cell to the first cell, the second cell and the third cell belong to the same cell group; or, if the handover scenario in which the terminal device is handed over from the second cell to the first cell is different from the handover scenario in which the terminal device is handed over from the third cell to the first cell, the second cell and the third cell belong to different cell groups. In this case, the Q1 cell groups can correspond to the Q1 handover scenarios. For the handover scenarios, please refer to the above description.

[0188] When the first cell and the second cell belong to DU1 and the third cell belongs to DU2, the cells other than the first cell in the W cells (i.e., the second cell and the third cell) belong to two cell groups (in this case, Q1=2), which are cell group 1 and cell group 2, respectively. The Q1 sets of data transmission mode information may include data transmission mode information b1 corresponding to handover of a terminal device from a cell in cell group 1 (i.e., the second cell) to the first cell, and data transmission mode information b2 corresponding to handover of a terminal device from a cell in cell group 2 (i.e., the third cell) to the first cell.

[0189] (2) Q2 sets of data transmission mode information, respectively corresponding to performing a handover of a terminal device from a cell in the Q2 cell groups to a second cell through layer 1 / layer 2 handover, where the cells other than the second cell in the W cells belong to the Q2 cell groups, and Q2 is a positive integer.

[0190] When the first cell and the second cell belong to DU1 and the third cell belongs to DU2, the cells other than the second cell in the W cells (i.e., the first cell and the third cell) belong to two cell groups (in this case, Q2=2), which are cell group 3 and cell group 4, respectively. The Q2 sets of data transmission mode information may include data transmission mode information b3 corresponding to handover of the terminal device from a cell in cell group 3 (i.e., the first cell) to the second cell, and data transmission mode information b4 corresponding to handover of the terminal device from a cell in cell group 4 (i.e., the third cell) to the second cell.

[0191] (3) Q3 sets of data transmission mode information, respectively corresponding to performing a handover of a terminal device from a cell in the Q3 cell groups to a third cell through layer 1 / layer 2 handover, where the cells other than the third cell in the W cells belong to the Q3 cell groups, and Q3 is a positive integer.

[0192] When the first cell and the second cell belong to DU1 and the third cell belongs to DU2, the cells other than the third cell in the W cells (i.e., the first cell and the second cell) belong to one cell group (in this case, Q3=1), i.e., cell group 5. The Q3 sets of data transmission mode information may include data transmission mode information b5 corresponding to handover of a terminal device from a cell in cell group 5 (i.e., the first cell or the second cell) to the third cell.

[0193] For implementation 2, at S502, the access network device may send an RRC message to a terminal device in a first cell, where the RRC message includes configuration information for W cells, and the configuration information for the W cells includes N sets of data transmission mode information. For example, the configuration information for the first cell may include related information of the first cell, configuration information for terminal devices in the first cell, and Q1 sets of data transmission mode information. The configuration information for the second cell includes related information of the second cell, configuration information for terminal devices in the second cell, and Q2 sets of data transmission mode information. The configuration information for the third cell includes related information of the third cell, configuration information for terminal devices in the third cell, and Q3 sets of data transmission mode information. In a CU-DU split network architecture, a possible manner of generating configuration information for the first cell is as follows: DU1 generates configuration information for the first cell (excluding the Q1 sets of data transmission mode information) and sends the configuration information to the CU. The CU generates Q1 sets of data transmission mode information, combines it with the configuration information for the first cell received from DU1 (excluding the Q1 sets of data transmission mode information) to generate complete configuration information for the first cell, and sends the complete configuration information to the terminal device. For the manner of generating the configuration information for the second cell and the third cell, please refer to the manner of generating the configuration information for the first cell. Details will not be described in this specification.

[0194] In another possible implementation, each set of data transmission mode information may be divided into two parts, which are indicated as a first part and a second part. The access network device notifies the terminal device of the first part through step S502, and notifies the terminal device of the second part through step S504-a. For specific processes, please refer to Implementation 1. The details will not be described again in this specification.

[0195] Optionally, the aforementioned method may further include S503-a to S506-a (ie, handover mode 1) or S503-b to S505-b (ie, handover mode 2).

[0196] S503-a: The terminal device performs beam level measurement for the W cells to obtain beam level measurement results, and reports the beam level measurement results to the access network device.

[0197] S504-a: The access network device sends a layer 1 or layer 2 handover command to the terminal device based on the beam level measurement result, the handover command instructs the terminal device to be handed over from the first cell to the second cell. In response, the terminal device receives the handover command and is handed over from the first cell to the second cell.

[0198] S505-a: The terminal device sends uplink information to an access network device in a second cell, where the uplink information notifies the access network device that the terminal device has been handed over from the first cell to the second cell through Layer 1 / Layer 2 handover. Correspondingly, the access network device may receive the uplink information and determine, based on the uplink information, that the second cell is the serving cell of the terminal device.

[0199] For example, for the uplink information, see the description in S305-a. In addition, in embodiment 1, the uplink information may include or be the indication information 2 (for details, see the description in S506-a).

[0200] In a possible implementation, the terminal device may further send an acknowledgement command for the handover command to the access network device to which the first cell belongs to indicate that the handover command has been successfully received.

[0201] S506-a: The terminal device and the access network device perform data transmission in the second cell based on the third data transmission mode information.

[0202] In one possible implementation, the access network device may determine which set of data transmission mode information among the N sets of data transmission mode information for the terminal device to use after the terminal device is handed over to the second cell. For example, if the access network device determines to use the third data transmission mode information among the N sets of data transmission mode information (the third data transmission mode information may be data transmission mode information a3 or data transmission mode information b3), the access network device may send instruction information 1 to the terminal device in the first cell, instructing the terminal device to perform data transmission with the access network device in the second cell based on the third data transmission mode information among the N sets of data transmission mode information after the terminal device is handed over from the first cell to the second cell. Correspondingly, the terminal device receives the instruction information 1 and, based on the instruction information 1, can know which set of data transmission mode information among the N sets of data transmission mode information will be used in the second cell to perform data transmission with the access network device without having to determine it independently. This reduces the power consumption of the terminal device. For example, the indication information 1 (or the subsequent indication information 2 or indication information 3) may indicate the third transmission mode information in multiple ways. For example, the indication information 1 may include an index of the third data transmission mode information, the index of the third data transmission mode information may be included in the third data transmission mode information, or the index may be unrelated to the third data transmission mode information. This is not specifically limited. The handover command and the indication information 1 may be carried in the same message or in different messages.

[0203] In another possible implementation, the terminal device can determine which set of data transmission mode information among the N sets of data transmission mode information should be used after the terminal device is handed over to the second cell. For example, if the terminal device determines to use the third data transmission mode information among the N sets of data transmission mode information (the third data transmission mode information may be the terminal device data transmission mode information a3 or the data transmission mode information b3), the terminal device can send instruction information 2 to the access network device in the second cell, where the instruction information 2 instructs the access network device to perform data transmission with the terminal device in the second cell based on the third data transmission mode information among the N sets of data transmission mode information after the terminal device is handed over from the first cell to the second cell. Correspondingly, the access network device receives the instruction information 2 and determines which set of data transmission mode information among the N sets of data transmission mode information should be used. Terminal Device and which cell will be used in the second cell for performing data transmission can be known based on the indication information 2 without autonomously determining it, thereby reducing the power consumption of the access network device.

[0204] The terminal device can send the indication information 2 to the access network device in the second cell in multiple manners. For example, the terminal device sends a physical layer message (e.g., the physical layer message is carried on a PUCCH or a physical random access channel (PRACH)) to the access network device in the second cell, and the physical layer message includes the indication information 2. In another example, the terminal device sends a MAC CE or RRC message to the access network device in the second cell, and the MAC CE or RRC message includes the indication information 2.

[0205] For example, the uplink information and the indication information 2 may be different information. In this case, the uplink information and the indication information 2 may be carried in different messages or the same message. Alternatively, as described in S505-a, "the uplink information may include the indication information 2." Alternatively, as described in S505-a, "the uplink information is the indication information 2." Specifically, by using the indication information 2, the terminal device may notify the access network device that the terminal device has been handed over from the first cell to the second cell through a Layer 1 / Layer 2 handover (this may be understood as an implicit notification), and may notify the access network device of data transmission mode information to be used.

[0206] In yet another possible implementation, the access network device and the terminal device can separately determine which set of data transmission mode information among the N sets of data transmission mode information should be used after the terminal device is handed over to the second cell. In this case, to save transmission resources, the access network device does not need to send the indication information 1 to the terminal device, and the terminal device does not need to send the indication information 2 to the access network device.

[0207] S503-b: The terminal device performs measurements on W cells to obtain beam level measurement results, and determines to be handed over from the first cell to the second cell based on the beam level measurement results.

[0208] S504-b: The terminal device sends handover completion information to the access network device in the second cell, where the handover completion information notifies the access network device that the terminal device has been handed over from the first cell to the second cell.

[0209] S505-b: The access network device and the terminal device perform data transmission in the second cell based on the third data transmission mode information.

[0210] In a possible implementation, the terminal device can determine which set of data transmission mode information among the N sets of data transmission mode information should be used after the terminal device is handed over to the second cell. For example, if the terminal device determines to use the third data transmission mode information among the N sets of data transmission mode information (the third data transmission mode information may be data transmission mode information a3 or data transmission mode information b3), the terminal device can send instruction information 3 to the access network device in the second cell, where the instruction information 3 instructs the access network device to perform data transmission with the terminal device in the second cell based on the third data transmission mode information among the N sets of data transmission mode information after the terminal device is handed over from the first cell to the second cell. For a manner in which the terminal device sends the instruction information 3, refer to the aforementioned manner in which the terminal device sends the instruction information 2. For example, the handover completion information and the instruction information 3 may be different information, or the handover completion information may include the instruction information 3, or the handover completion information is the instruction information 3. For details, please refer to the description of uplink information and instruction information 2 in S506-a.

[0211] In another possible implementation, the access network device and the terminal device can separately determine which set of data transmission mode information among the N sets of data transmission mode information should be used after the terminal device is handed over to the second cell. For example, the access network device may know based on the uplink information that the terminal device will be handed over from the first cell to the second cell, and may further determine to use third data transmission mode information among the N sets of data transmission mode information (the third data transmission mode information may be data transmission mode information a3 or data transmission mode information b3).

[0212] It can be understood that the above describes two implementation forms in which a terminal device is handed over from a first cell to a second cell through Layer 1 / Layer 2 handover using S503-a to S506-a (i.e., cell handover triggered by the access network device based on beam level measurement results) and S503-b to S505-b (i.e., cell handover triggered by the terminal device based on beam level measurement results). After the access network device determines that the terminal device has been handed over from the first cell to the second cell, the access network device may stop transmitting downlink data to the terminal device, but the access network device and the terminal device do not release the N sets of data transmission mode information for the terminal device. In other words, after the cell handover of the terminal device, the access network device and the terminal device still store the N sets of data transmission mode information for the terminal device.

[0213] Further, in a possible implementation, after the terminal device is handed over to the second cell, the terminal device may be further handed over from the second cell to the first cell through a Layer 1 / Layer 2 handover. In this case, the access network device may send first instruction information to the terminal device in the second cell. The first instruction information instructs the terminal device to perform data transmission with the access network device based on the first data transmission mode information in the N sets of data transmission mode information after the terminal device is handed over from the second cell to the first cell through the first type of cell handover. For an implementation of the first instruction information, please refer to the above-mentioned Instruction Information 1. Alternatively, the terminal device may send third indication information and fourth indication information to the access network device in the first cell, where the third indication information indicates that the terminal device has been handed over from the second cell to the first cell through a first type of cell handover, and the fourth indication information instructs the access network device to perform data transmission with the terminal device based on the first data transmission mode information in the N sets of data transmission mode information. For an implementation form of the third indication information, refer to the above-mentioned uplink information, and for an implementation form of the fourth indication information, refer to the above-mentioned indication information 2. Alternatively, for an implementation form of the third indication information, refer to the above-mentioned handover completion information, and for an implementation form of the fourth indication information, refer to the above-mentioned indication information 3. In this way, the access network device and the terminal device may perform data transmission in the first cell based on the first data transmission mode information (e.g., data transmission mode information a1 or data transmission mode information b1).

[0214] In another possible implementation, after the terminal device is handed over to the second cell, the terminal device may be further handed over from the second cell to a third cell through a Layer 1 / Layer 2 handover. In this case, the access network device may send second instruction information to the terminal device in the second cell. The second instruction information instructs the terminal device to perform data transmission with the access network device based on the second data transmission mode information in the N sets of data transmission mode information after the terminal device is handed over from the second cell to the third cell through the first type of cell handover. For an implementation of the second instruction information, see the above-mentioned Instruction Information 1. Alternatively, the terminal device may send fifth indication information and sixth indication information to the access network device in the third cell, where the fifth indication information indicates that the terminal device has been handed over from the second cell to the third cell via a first type of cell handover, and the sixth indication information instructs the access network device to perform data transmission with the terminal device based on the second data transmission mode information in the N sets of data transmission mode information. For an implementation form of the fifth indication information, see the above-mentioned uplink information, and for an implementation form of the sixth indication information, see the above-mentioned indication information 2. Alternatively, for an implementation form of the fifth indication information, see the above-mentioned handover completion information, and for an implementation form of the sixth indication information, see the above-mentioned indication information 3. In this way, the access network device and the terminal device may perform data transmission in the third cell based on the second data transmission mode information (e.g., data transmission mode information a6 or data transmission mode information b5).

[0215] It can be understood that for a specific implementation form in which the terminal device is handed over from the second cell to the first cell or the third cell through Layer 1 / Layer 2 handover, please refer to the description of the handover of the terminal device from the first cell to the second cell. In other words, after the access network device sends N sets of data transmission mode information to the terminal device in the first cell, and multiple Layer 1 / Layer 2 handovers of the terminal device are successively performed between W cells, both the access network device and the terminal device can use the corresponding data transmission mode information, and the access network device does not need to send corresponding data transmission mode information to the terminal device, which effectively saves transmission resources.

[0216] In addition, after the access network device sends the N sets of data transmission mode information to the terminal device, if the access network device determines that a second condition is met, the access network device may release the N sets of data transmission mode information for the terminal device and / or may instruct the terminal device to release the N sets of data transmission mode information.

[0217] Article 2 The matter , may include at least one of the following: (1) the terminal device needs to be handed over to the fourth cell via Layer 3 handover, (2) the terminal device needs to enter idle mode or inactive mode, and (3) N sets of data transmission mode information for the terminal device needs to be changed.

[0218] Regarding (1), in addition to performing beam level measurements on the W cells in S503-a, the terminal device may further perform cell level measurements on multiple cells including the W cells to obtain cell level measurement results, and report the cell level measurement results to the access network device. Further, in S504-a, the access network device may trigger a layer 1 / layer 2 handover or a layer 3 handover based on the beam level measurement results and the cell level measurement results. The process shown in FIG. 5 is explained by using an example in which the access network device triggers a layer 1 / layer 2 handover. In another possible embodiment, if the access network device determines, based on the beam level measurement results reported by the terminal device, that none of the candidate cells corresponding to the layer 1 / layer 2 handover are suitable to serve as a target cell, the access network device may perform a layer 3 handover. By performing a Layer 3 handover, the terminal device may be handed over to a cell other than the W cells, for example, a fourth cell (in other words, the fourth cell is a cell other than the W cells), so the access network device may release N sets of data transmission mode information for the terminal device and / or instruct the terminal device to release N sets of data transmission mode information.

[0219] Similarly, in S503-b, in addition to performing beam level measurements for the W cells, the terminal device may further perform cell-level measurements for multiple cells including the W cells to obtain cell-level measurement results. Furthermore, the terminal device triggers a layer 1 / layer 2 CHO or a layer 3 CHO based on the beam level measurement results and the cell-level measurement results. The process shown in FIG. 5 is described by using an example in which an access network device triggers a layer 1 / layer 2 CHO. In another possible embodiment, if the terminal device determines that the handover criteria for the layer 1 / layer 2 CHO are not met but the handover criteria for the layer 3 CHO are met, the terminal device may trigger a layer 3 CHO. Because the terminal device may be handed over to a cell other than the W cells (e.g., a fourth cell) by performing a layer 3 handover, the access network device may release N sets of data transmission mode information for the terminal device and / or instruct the terminal device to release N sets of data transmission mode information.

[0220] Regarding (2), during successive cell handovers of the terminal device, the access network device always maintains the RRC connection to the terminal device. If the access network device determines that the RRC connection to the terminal device needs to be disconnected (e.g., the terminal device needs to enter idle mode), the access network device may release N sets of data transmission mode information for the terminal device and / or instruct the terminal device to release N sets of data transmission mode information.

[0221] Regarding (3), because the N sets of data transmission mode information are pre-configured by the access network device for the terminal device before successive cell handovers of the terminal device, the N sets of data transmission mode information may need to be changed subsequently for multiple reasons. Therefore, if the N sets of data transmission mode information need to be changed, the access network device may release the N sets of data transmission mode information and / or instruct the terminal device to release the N sets of data transmission mode information. Optionally, when determining that the configuration information for any one of the W cells needs to be changed, the access network device may release the N sets of data transmission mode information and / or instruct the terminal device to release the N sets of data transmission mode information. In this case, after the access network device and the terminal device release the N sets of data transmission mode information, subsequent procedures may be performed with reference to the scheme shown in FIG. 3 or the scheme shown in FIG. 5. For example, when a terminal device is handed over from another cell to a first cell through a layer 1 / layer 2 handover and the previously configured sets of data transmission mode information need to be changed, the access network device can execute S502. In other words, the access network device and the terminal device release all of the last configured sets of data transmission mode information, and then the access network device reconfigures the sets of data transmission mode information for the terminal device.

[0222] It can be understood that "when a terminal device is handed over from another cell to a first cell via a layer 1 / layer 2 handover and multiple sets of previously configured data transmission mode information need to be changed, the access network device can execute S502" may further include another possible case. For example, when a terminal device is handed over from another cell to a first cell via a layer 1 / layer 2 handover and multiple sets of previously configured data transmission mode information need to be changed, in S502, the access network device may send an RRC reconfiguration message to the terminal device, where the RRC reconfiguration message includes N sets of data transmission mode information and is for modifying the multiple sets of previously configured data transmission mode information. Correspondingly, after receiving the RRC reconfiguration message, the terminal device may modify the multiple sets of previously configured data transmission mode information based on the RRC reconfiguration message. In this case, the access network device and the terminal device change the multiple previously configured data transmission modes instead of releasing all of the multiple previously configured data transmission modes. For example, the multiple sets of previously configured data transmission modes include data transmission mode information d1 corresponding to handover of the terminal device from the second cell to the first cell and data transmission mode information a2 corresponding to handover of the terminal device from the third cell to the first cell, and the N sets of data transmission mode information include data transmission mode information a1 corresponding to handover of the terminal device from the second cell to the first cell. In this case, it indicates that the "data transmission mode information d1" is changed to "data transmission mode information a1", and the data transmission mode information a2 remains unchanged.

[0223] For example, in addition to releasing N sets of data transmission mode information, the access network device and the terminal device may further release configuration information for W cells and / or configuration information for terminal devices within the W cells.

[0224] The access network device can instruct the terminal device to release the N sets of data transmission mode information in multiple manners. In a possible implementation, the access network device can send instruction information 4 to the terminal device, where the instruction information 4 instructs the terminal device to release the N sets of data transmission mode information. For example, the instruction information 4 can be an information element carried in an RRC message such that the terminal device can release the N sets of data transmission mode information after receiving an RRC message (e.g., an RRC reconfiguration message).

[0225] According to the method in embodiment 1, an access network device may send configuration information for a plurality of cells to a terminal device in a first cell. The configuration information of each of the plurality of cells includes data transmission mode information corresponding to a handover of the terminal device from another cell to the cell. Therefore, when performing successive handovers between different cells, the terminal device can directly use the corresponding data transmission mode information to effectively save transmission resources.

[0226] Embodiment 2 6 is a schematic flowchart corresponding to a communication method according to Embodiment 2 of the present invention. As shown in FIG. 6, the method includes the following steps:

[0227] S601: An access network device determines that a first cell is a serving cell of a terminal device.

[0228] S602: The access network device sends K sets of data transmission mode information to a terminal device in a first cell, where the K sets of data transmission mode information indicate K data transmission modes.

[0229] For example, the access network device may determine K handover scenarios in which a terminal device is handed over between W cells to obtain K data transmission modes corresponding to the K handover scenarios. For example, if the W cells belong to the same DU, the handover scenario in which a terminal device is handed over between W cells is scenario 1. In this case, K=1, and the data transmission mode may be data transmission mode 1. In another example, if the W cells belong to different DUs controlled by the same CU and include two or more cells of the same DU (e.g., the first cell and the second cell belong to DU1, and the third cell belongs to DU2), the handover scenario in which a terminal device is handed over between W cells includes scenario 1 and scenario 2. In this case, K=2, and the K data transmission modes may include data transmission mode 1 and data transmission mode 3.

[0230] In addition, the access network device can further send configuration information for the W cells to the terminal device in the first cell. Using the first cell as an example, the configuration information for the first cell can include related information of the first cell and configuration information for the terminal device in the first cell. The difference from the configuration information for the first cell in embodiment 1 is that the configuration information for the first cell in embodiment 2 may not include data transmission mode information.

[0231] Optionally, the method may further include the following steps:

[0232] S603: The terminal device performs beam level measurement for the W cells to obtain beam level measurement results, and reports the beam level measurement results to the access network device.

[0233] S604: The access network device sends a layer 1 or layer 2 handover command to the terminal device based on the beam level measurement result, the handover command instructs the terminal device to be handed over from the first cell to the second cell. In response, the terminal device receives the handover command and is handed over from the first cell to the second cell.

[0234] S605: The terminal device sends uplink information to an access network device in the second cell, where the uplink information notifies the access network device that the terminal device has been handed over from the first cell to the second cell through Layer 1 / Layer 2 handover. Correspondingly, the access network device may determine, based on the uplink information, that the second cell is a serving cell of the terminal device.

[0235] For example, see the description in S305-a for uplink information.

[0236] S606: The terminal device and the access network device perform data transmission based on the third data transmission mode information.

[0237] In a possible embodiment, the access network device may determine which set of data transmission mode information among the K sets of data transmission mode information should be used after the terminal device is handed over to the second cell. For example, if the access network device determines to use the third data transmission mode information among the K sets of data transmission mode information, the access network device may send instruction information 1 to the terminal device in the first cell, where the instruction information 1 instructs the terminal device to perform data transmission with the access network device in the second cell based on the third data transmission mode information among the K sets of data transmission mode information after the terminal device is handed over from the first cell to the second cell. Correspondingly, the terminal device receives the instruction information 1 and, based on the instruction information 1, can know which data transmission mode information set among the K sets of data transmission mode information will be used to perform data transmission with the access network device in the second cell without having to determine it independently. This reduces the power consumption of the terminal device.

[0238] In another possible implementation, the terminal device can determine which set of data transmission mode information among the K sets of data transmission mode information should be used after the terminal device is handed over to the second cell. For a specific process, please refer to S506-a. The details will not be described again in this specification. In another possible implementation, the access network device and the terminal device can separately determine which set of data transmission mode information among the K sets of data transmission mode information should be used after the terminal device is handed over to the second cell. For a specific process, please refer to S506-a. The details will not be described again in this specification.

[0239] According to the method in embodiment 2, the access network device may determine K data transmission modes corresponding to K handover scenarios in which the terminal device is handed over between W cells, and may send K sets of data transmission mode information to the terminal device in the first cell. In this way, during successive handovers of the terminal device between different cells, the access network device can indicate to the terminal device the data transmission mode information to be used, so as to effectively save transmission resources.

[0240] In embodiment 1 and embodiment 2, the implementation process of the embodiment of the present application is described from the perspective of communication between an access network device and a terminal device. The access network device may include a CU and one or more DUs. Therefore, with reference to embodiment 3, the implementation process of the embodiment of the present application will be described below from the perspective of communication between a CU, a DU, and a terminal device.

[0241] Embodiment 3 In embodiment 3, the interaction process between the CU, the DU, and the terminal device is described based on embodiment 1 (the interaction process between the CU, the DU, and the terminal device in embodiment 2 can be implemented by reference).

[0242] 7 is a schematic flowchart corresponding to a communication method according to Embodiment 3 of the present invention. As shown in FIG. 7, the method includes the following steps:

[0243] S701: The CU determines that the first cell of the DU1 is the serving cell of the terminal device.

[0244] S702: The CU determines W cells for the terminal device and configuration information for the W cells, where the configuration information for the W cells includes N sets of data transmission mode information.

[0245] In this specification, an example is used in which the W cells include a first cell, a second cell, and a third cell. The access network device includes a CU, a DU1, and a DU2, and the first cell and the second cell belong to the DU1, and the third cell belongs to the DU2. For specific content included in the configuration information for the W cells, please refer to embodiment 1.

[0246] For example, the CU may determine W cells based on measurement results of the terminal device (e.g., cell-level measurement results of the terminal device), and may further determine N sets of data transmission mode information for the terminal device by referring to the positional relationships between the W cells (e.g., whether the W cells belong to the same CU and / or the same DU).

[0247] S703: The CU sends configuration information for the W cells to the terminal device via DU1. Correspondingly, the terminal device can receive the configuration information for the W cells.

[0248] In a possible implementation, the CU can send an RRC message to the terminal device via DU1, in which case the configuration information for W cells can be placed in a container and transparently transmitted to the terminal device via DU1.

[0249] In another possible implementation, the CU can send configuration information for W cells to the DU1 by using an F1 interface message, and then the DU1 sends the configuration information for the W cells to the terminal device.

[0250] S704: The CU sends configuration information about W1 cells to the DU1, where W1 is less than or equal to W.

[0251] For example, W1 cells belong to W cells and may include cells of DU1 (e.g., the first cell and the second cell). Optionally, W1 cells further include a candidate cell of the terminal device (e.g., a third cell; specifically, the terminal device may be handed over to the third cell from the first cell or the second cell) that exists when the serving cell of the terminal device is the cell of DU1. Considering that the W cells may further include another cell, but that the cell is neither the cell of DU1 nor a candidate cell, the CU does not need to send configuration information for the cell to DU1 to save transmission resources.

[0252] It can be understood that the configuration information for a candidate cell (e.g., a third cell) among the W1 cells may include the complete configuration information described above, for example, the related information of the third cell, the configuration information for the terminal device in the third cell, and the corresponding data transmission mode information, or may include only the configuration information related to the handover from DU1, for example, the PCI of the third cell, so that DU1 knows that the terminal device can be handed over between the W1 cells. In other words, the configuration information about the candidate cell transmitted by the CU to DU1 is about the cell and may not need to include the complete configuration information that needs to be detected by the terminal device.

[0253] For example, the CU may send configuration information about the W cells to the DU1 by using an F1 interface message, which may be, for example, a DL RRC message transfer or a UE context modification request.

[0254] For S703 and S704, in a possible manner, the CU can transmit the configuration information for the W cells and the configuration information for the W1 cells to the DU1 by using the same F1 interface message. Alternatively, the CU transmits the configuration information for the W cells to the DU1 by using the F1 interface message, so that the DU1 can obtain the configuration information for the W1 cells based on the configuration information for the W cells, store the configuration information for the W1 cells, and transmit the configuration information for the W cells to the terminal device. In this case, the CU does not need to transmit the configuration information for the W1 cells to the DU1.

[0255] S705: The CU sends configuration information about W2 cells to the DU2, where W2 is less than or equal to W.

[0256] For example, the W2 cells may belong to the W cells and include a cell of DU2 (e.g., a third cell). Optionally, the W2 cells further include candidate cells of the terminal device (e.g., a first cell and a second cell, specifically, the terminal device may be handed over from the third cell to the first cell or the second cell) that exist when the serving cell of the terminal device is the cell of DU2. For another implementation, see the description of S704.

[0257] It can be understood that the above provides an explanation by using an example in which a CU determines W cells and configuration information for the W cells. In another possible embodiment, a DU can determine W cells based on measurement results of a terminal device (e.g., beam level measurement results of a terminal device) and report the W cells to the CU. For example, DU1 determines a first cell and a second cell and reports the first cell and the second cell to the CU, and DU2 determines a third cell and reports the third cell to the CU. In this way, the CU can determine configuration information for the W cells based on the positional relationships among the W cells.

[0258] Alternatively, the DU may determine W cells based on measurement results of the terminal device (e.g., beam level measurement results of the terminal device) and report the W cells to the CU. As a result, the CU determines a positional relationship between the W cells and notifies DU1 and DU2 of the positional relationship. DU1 and DU2 may determine configuration information for the W cells based on the positional relationship between the W cells. Furthermore, the CU may obtain configuration information for the W cells (e.g., N sets of data transmission mode information) from DU1 and DU2. There may be multiple implementations in which the CU obtains the N sets of data transmission mode information from DU1 and DU2. For example, the CU may send a request message 1 to DU1 to which the first cell and the second cell belong, where the request message 1 requests data transmission mode information. In this way, DU1 may transmit P1 sets of transmission mode information and P2 sets of data transmission mode information to the CU (see Implementation 1 of Embodiment 1). Alternatively, DU1 may send Q1 sets of transmission mode information and Q2 sets of data transmission mode information to the CU (see Implementation 2 of Embodiment 1). In addition, the CU may send a request message 2 to DU2 to which the third cell belongs, where the request message 2 requests data transmission mode information, so that DU2 may send P3 sets of transmission mode information to the CU (see Implementation 1 of Embodiment 1), or DU2 may send Q3 sets of transmission mode information to the CU (see Implementation 2 of Embodiment 1). In this case, in S704, the CU may send the configuration information of the third cell to DU1 without sending the configuration information of the first cell and the second cell to DU1. In S705, the CU may send the configuration information of the first cell and the second cell to DU2 without sending the configuration information of the third cell to DU2. Alternatively, the CU may not need to perform S704 and S705; in other words, the CU does not need to send the configuration information of the corresponding cell to DU1 or DU2.

[0259] Optionally, the method may further include S403-a to S406-a, or may include S403-b to S405-b.

[0260] S706-a: The terminal device performs beam level measurement for W cells to obtain beam level measurement results, and reports the beam level measurement results to DU1.

[0261] S707-a: DU1 sends a layer 1 or layer 2 handover command to the terminal device based on the beam level measurement result, the handover command instructs the terminal device to be handed over from the first cell to the second cell. In response, the terminal device receives the handover command and is handed over from the first cell to the second cell.

[0262] S708-a: The terminal device transmits uplink information to DU1 in the second cell, where the uplink information notifies DU1 that the terminal device has been handed over from the first cell to the second cell through Layer 1 / Layer 2 handover. Correspondingly, DU1 may stop transmitting downlink data to the terminal device in the first cell after receiving the uplink information and determining that the second cell is the serving cell of the terminal device.

[0263] For a specific implementation of the uplink information, please refer to embodiment 1.

[0264] S709-a: The terminal device and DU1 perform data transmission in the second cell based on the third data transmission mode information.

[0265] For specific implementation forms in this specification, please refer to embodiment 1.

[0266] S706-b: The terminal device performs measurements on W cells to obtain beam level measurement results, and determines to be handed over from the first cell to the second cell based on the beam level measurement results.

[0267] S707-b: The terminal device sends handover completion information to the DU1 in the second cell, where the handover completion information notifies the DU1 that the terminal device has been handed over from the first cell to the second cell.

[0268] S708-b: DU1 and the terminal device perform data transmission in the second cell based on the third data transmission mode information.

[0269] For related implementations of this specification, please refer to embodiment 1.

[0270] In addition, after determining that the second condition is met, the CU may instruct the DUs (e.g., DU1 and DU2) to which the W cells belong to release N sets of data transmission mode information for the terminal device, and / or instruct the terminal device to release N sets of data transmission mode information.

[0271] There may be multiple ways for the CU to instruct the DU to release N sets of data transmission mode information for the terminal device. For example, the CU sends a UE context release command (UE context change request) to the DU, where the UE context release command includes an identifier of the terminal device, and the DU releases the N sets of data transmission mode information for the terminal device based on the UE context release command.

[0272] For an implementation form in which the CU instructs the terminal device to release N sets of data transmission mode information, please refer to the implementation form in which the access network device instructs the terminal device to release N sets of data transmission mode information in embodiment 1.

[0273] In embodiment 3, an intra-DU cell handover process, i.e., handover of DU1 from a first cell to a second cell, is described. In this scenario, the CU sends N sets of data transmission mode information to the terminal device via DU1. Therefore, when the terminal device needs to be handed over from the first cell to the second cell, DU1 can determine the data transmission mode information to be used and send an index of the data transmission mode information to be used to the terminal device. Alternatively, the terminal device can determine the data transmission mode information to be used and send an index of the data transmission mode information to be used to DU1. Alternatively, the terminal device and DU1 separately determine the data transmission mode information to be used. It should be understood that in an inter-DU cell handover process, the CU sends N sets of data transmission mode information to the terminal device via DU1. When a terminal device needs to be handed over (for example, when a terminal device needs to be handed over from a second cell of DU1 to a third cell of DU2), DU1 may determine data transmission mode information that needs to be used and may send an index of the data transmission mode information that needs to be used to the terminal device. When the terminal device is handed over to the third cell in a designated data transmission mode, the terminal device may notify DU2 of the index of the data transmission mode information, or DU2 autonomously determines the data transmission mode information that needs to be used.

[0274] In another possible embodiment, the CU may not send N sets of data transmission mode information to the terminal device. In this case, when the terminal device needs to be handed over, the source DU can determine the data transmission mode information to be used and send the data transmission mode information to be used to the terminal device. For example, the data transmission mode information to be used is sent to the terminal device in a handover command (this is different from embodiment 3 in which an index of the data transmission mode information is sent to the terminal device).

[0275] An embodiment of the present application provides another communication method. The communication method may include: after determining that a first cell is a serving cell of a terminal device, an access network device may send cell group information of W cells to the terminal device in the first cell, where the W cells include the first cell, and the cell group information is for determining a data transmission mode corresponding to performing a handover of the terminal device from one cell among the W cells to another cell among the W cells via a first type of cell handover. In other words, the access network device may send the cell group information to the terminal device in the first cell, so that when the terminal device is handed over between different cells continuously, the terminal device can determine a data transmission mode to be used based on the groups to which the source cell and target cell to which the terminal device is handed over belong, thereby effectively saving transmission resources.

[0276] The method will be described in detail below with reference to embodiment 4. The data transmission mode in embodiment 4 may be the data transmission mode described in example 2 above.

[0277] Embodiment 4 8 is a schematic flowchart corresponding to a communication method according to Embodiment 4 of the present invention. As shown in FIG. 8, the method includes the following steps:

[0278] S801: An access network device determines that a first cell is a serving cell of a terminal device.

[0279] S802: The access network device sends cell group information to a terminal device in a first cell. In response, the terminal device may receive the cell group information. In addition, the access network device and the terminal device may store the cell group information.

[0280] For example, before S802, the access network device may determine W cells for the terminal device and then determine cell group information based on the W cells. The terminal device can perform successive handovers among the W cells. The cell group information is for determining a data transmission mode corresponding to handover of the terminal device from one cell of the W cells to another cell of the W cells (e.g., a data transmission mode corresponding to performing handover of the terminal device from one cell of the W cells to another cell of the W cells via layer 1 / layer 2 handover). The data transmission mode is, for example, the above-mentioned data transmission mode A or data transmission mode B.

[0281] For example, the cell group information may include at least one of PDCP layer group information, RLC layer group information, or MAC layer group information. In the following, the cell group information is described by using an example in which W cells include cell1, cell2, cell3, and cell4, and cell1 is the first cell.

[0282] (1) PDCP Layer Group Information For example, the access network device may determine the PDCP layer group information based on the PDCP layer behavior corresponding to a handover of the terminal device between the W cells.

[0283] In a possible implementation, PDCP re-establishment does not need to be performed when a terminal device is handed over between W cells. For example, the W cells are served by the same CU, that is, the W cells belong to a DU controlled by the same CU. Specifically, PDCP layer behavior corresponding to a handover of a terminal device between W cells includes PDCP data restoration or maintenance for data radio bearers and PDCP teardown or maintenance for signaling radio bearers. In this case, using data radio bearers as an example, the access network device can divide the W cells into two PDCP groups. For example, PDCP group 1 includes {cell1, cell2}, and PDCP group 2 includes {cell3, cell4}. When the source cell and target cell to which the terminal device is handed over are in the same PDCP group, PDCP maintenance is performed (in other words, PDCP data restoration is not performed). When the source cell and target cell to which the terminal device is handed over are not in the same PDCP group, PDCP data restoration may be performed.

[0284] It should be understood that for some types of data radio bearers, e.g., unacknowledged mode (UM) data radio bearers, the PDCP layer behavior may not be constrained by the aforementioned group and PDCP maintenance is always performed, and for some other types of data radio bearers, e.g., acknowledged mode (AM) data radio bearers, the PDCP layer behavior should be constrained by the aforementioned group.

[0285] In addition, for the signaling radio bearer, the access network device may also group W cells. When possible, the grouping result for the signaling radio bearer is the same as the grouping result for the data radio bearer; in other words, the grouping result for the data radio bearer may be reused. When the source cell and the target cell to which the terminal device is handed over are in the same PDCP group, PDCP maintenance is performed. When the source cell and the target cell to which the terminal device is handed over are not in the same PDCP group, PDCP discard may be performed.

[0286] In another possible implementation, PDCP re-establishment may need to be performed when a terminal device is handed over between W cells. For example, the W cells are served by different CUs, that is, the W cells belong to DUs controlled by different CUs. Specifically, PDCP layer behaviors corresponding to a handover of a terminal device between W cells include PDCP re-establishment, PDCP data recovery, or PDCP maintenance. In this case, the access network device may perform a second-level grouping for the W cells. The first-level grouping indicates whether PDCP re-establishment should be performed. For example, PDCP group 1-1 {cell1, cell2, cell3} and PDCP group 1-2 {cell4} are obtained through the first-level grouping. When the source cell and target cell of the terminal device are in the same group of the first-level grouping, PDCP re-establishment does not need to be performed. When the source cell and target cell of the terminal device are not in the same group of the first-level grouping, PDCP re-establishment needs to be performed. Furthermore, when PDCP re-establishment does not need to be performed, a second-level grouping is performed. For example, PDCP group 2-1{cell1, cell2} and PDCP group 2-2{cell3} are obtained through the second-level grouping. When the source cell and target cell of the terminal device are in the same group of the second-level grouping, PDCP maintenance is performed. When the source cell and target cell of the terminal device are not in the same group of the second-level grouping, PDCP data recovery is performed.

[0287] The above process can be understood as a description of the PDCP layer behavior for data radio bearers. For the PDCP layer behavior of signaling radio bearers, please refer to the above description. The difference is that for signaling radio bearers, the grouping behavior includes "PDCP re-establishment, PDCP teardown, and PDCP maintenance." The details will not be described again here.

[0288] In addition, the PDCP layer group information may be for performing different cell groupings for each bearer, and the PDCP layer behavior corresponding to each bearer may be determined based on the cell group for the bearer, or the same group may be shared among multiple bearers, which is not limited in this application.

[0289] (2) RLC layer group information The RLC layer behavior corresponding to the handover of the terminal device between W cells includes RLC re-establishment or maintenance. The access network device may divide the W cells into two RLC groups. For example, RLC group 1 includes {cell1, cell2}, and RLC group 2 includes {cell3, cell4}. When the source cell and target cell of the terminal device are not in the same group, RLC re-establishment is performed. When the source cell and target cell of the terminal device are in the same group, RLC maintenance is performed.

[0290] For example, when the PDCP layer behavior corresponding to a handover of a terminal device between W cells includes PDCP data restoration or maintenance, the RLC layer group information and the PDCP layer group information may be bound together. For example, when PDCP maintenance is performed, RLC maintenance is also performed. When PDCP data restoration is performed, RLC re-establishment needs to be performed. In this case, only the PDCP layer group information or only the RLC layer group information may be configured to implicitly indicate the PDCP layer behavior or the RLC layer behavior.

[0291] (3) MAC Layer Group Information As mentioned above, if there is no association relationship between random access and MAC reset, the following three possible implementations may be included:

[0292] In a first possible implementation, the MAC layer behavior corresponding to the handover of the terminal device between W cells includes MAC reset or MAC maintenance, and the access network device may obtain the MAC group through division based on the MAC layer behavior. For example, the access network device can divide the W cells into two MAC groups. For example, MAC group 1 includes {cell1, cell2}, and MAC group 2 includes {cell3, cell4}. When the source cell and the target cell to which the terminal device is handed over are in the same MAC group, MAC maintenance is performed. When the source cell and the target cell to which the terminal device is handed over are not in the same MAC group, MAC reset may be performed.

[0293] In a second possible implementation, the MAC layer behavior corresponding to the handover of the terminal device between W cells includes MAC reset, MAC partial reset, or MAC maintenance. In this case, the access network device can perform second-level grouping for the W cells. The first-level grouping indicates whether a MAC reset should be performed. For example, MAC group 1-1 {cell1, cell2, cell3} and MAC group 1-2 {cell4} are obtained through the first-level grouping. When the source cell and target cell of the terminal device are in the same group of the first-level grouping, a MAC reset does not need to be performed. When the source cell and target cell of the terminal device are not in the same group of the first-level grouping, a MAC reset needs to be performed. Furthermore, when a MAC reset does not need to be performed, the second-level grouping is performed. For example, MAC group 2-1 {cell1, cell2} and MAC group 2-2 {cell3} are obtained through the second-level grouping. When the source cell and target cell of the terminal device are in the same group of the second-level grouping, MAC maintenance is performed. When the source cell and the target cell of the terminal device are not in the same group of the second level grouping, a MAC partial reset is performed.

[0294] In a third possible implementation, whether to perform random access in the handover process needs to be indicated to the terminal device by the access network device. Therefore, in this embodiment of the present application, the access network device may alternatively obtain the MAC group through division depending on whether to perform random access in the handover process (or whether the terminal device needs to send an uplink message in the handover process to obtain uplink synchronization information for the target cell). For example, the access network device may divide W cells into two MAC groups. For example, MAC group 1 includes {cell1, cell2, cell3}, and MAC group 2 includes {cell4}. If the source cell and target cell of the terminal device do not belong to the same group, the terminal device performs random access. If the source cell and target cell of the terminal device belong to the same group, the terminal device does not perform random access. When the terminal device performs random access, the access network device may cooperate to complete the random access process based on a received uplink message (e.g., a random access preamble). If the terminal device does not perform random access, the access network device may actively schedule the terminal device through the target cell, or may pre-configure uplink grant resources or PUCCH resources for the terminal device.

[0295] The first possible implementation form and the third possible implementation form may coexist. In this case, the terminal device may determine whether a MAC reset or maintenance should be performed in the first possible implementation form, and may determine whether to perform random access in the third possible implementation form. The second possible implementation form and the third possible implementation form may coexist. In this case, the terminal device may determine whether a MAC reset, a partial reset, or maintenance should be performed in the second possible implementation form, and may determine whether to perform random access in the third possible implementation form.

[0296] When there is an association relationship between random access and MAC reset, the access network device may obtain the MAC group through division based on MAC layer behavior or depending on whether to perform random access. For example, the MAC layer behavior corresponding to the handover of a terminal device between W cells includes MAC reset or MAC maintenance, and the MAC group obtained by the access network device through division based on the MAC layer behavior may include MAC group 1 {cell1, cell2} and MAC group 2 {cell3, cell4}. If the source cell from which the terminal device is handed over and the target cell to which the terminal device is handed over are in the same MAC group, MAC maintenance is performed, which implicitly indicates skipping the execution of random access. If the source cell from which the terminal device is handed over and the target cell to which the terminal device is handed over are not in the same MAC group, MAC reset may be performed, which implicitly indicates performing random access. In the following description of this embodiment of the present application, the case where there is an association relationship between random access and MAC reset is used as an example for explanation.

[0297] For example, in S802, the access network device can send an RRC message to a terminal device in a first cell, where the RRC message includes cell group information and optionally further includes configuration information for W cells. Using a first cell in the W cells as an example, the configuration information for the first cell may include related information of the first cell and configuration information for the terminal device in the first cell. For the related information of the first cell and the configuration information for the terminal device in the first cell, please refer to the above description. The details will not be described again in this specification.

[0298] Optionally, the aforementioned method may further include S803-a to S806-a (ie, handover mode 1) or S803-b to S805-b (ie, handover mode 2).

[0299] S803-a: The terminal device performs beam level measurement for W cells to obtain beam level measurement results, and reports the beam level measurement results to the access network device.

[0300] S804-a: The access network device sends a layer 1 or layer 2 handover command to the terminal device based on the beam level measurement result, where the handover command instructs the terminal device to be handed over from the first cell to the second cell. In response, the terminal device receives the handover command and is handed over from the first cell to the second cell.

[0301] For example, the second cell may be any one of cell2, cell3, or cell4.

[0302] S805-a: The terminal device sends uplink information to an access network device in a second cell, where the uplink information notifies the access network device that the terminal device has been handed over from the first cell to the second cell through Layer 1 / Layer 2 handover. Correspondingly, the access network device may receive the uplink information and determine, based on the uplink information, that the second cell is the serving cell of the terminal device.

[0303] S806-a: The terminal device and the access network device perform data transmission in the second cell in a corresponding data transmission mode.

[0304] In a possible implementation, after the terminal device is handed over to the second cell, the terminal device can determine the group to which the first cell and the second cell belong based on the cell group information to determine the data transmission mode to be used. In addition, after the terminal device is handed over to the second cell, the access network device can determine the group to which the first cell and the second cell belong based on the cell group information to determine the data transmission mode to be used. In other words, the access network device and the terminal device can separately determine the data transmission mode to be used after the terminal device is handed over to the second cell, and the data transmission mode determined by the access network device and the terminal device is the same. For a specific process, see S506-a.

[0305] The following uses an example to explain how a terminal device determines a data transmission mode to be used when performing cell handover among W cells. For example, cell group information configured by an access network device for a terminal device includes PDCP group 1 {cell1, cell2} and PDCP group 2 {cell3, cell4}, RLC group 1 {cell1, cell2} and RLC group 2 {cell3, cell4}, and MAC group 1 {cell1, cell2, cell3} and MAC group 2 {cell4}. The current serving cell (source cell) of the terminal device is cell1. When the terminal device receives a handover command indicating handover to cell2, because both cell1 and cell2 belong to PDCP group1, RLC group1, and MAC group1, the terminal device may perform PDCP maintenance and RLC maintenance and does not perform random access. Correspondingly, the access network device also performs corresponding behavior. After the terminal device is handed over to cell2, the serving cell of the terminal is cell2. When the terminal device receives the handover command again, indicating a handover to cell 4, the terminal device may perform PDCP data recovery, RLC re-establishment, and random access because cell 2 and cell 4 belong to different PDCP groups, different RLC groups, and different MAC groups. Correspondingly, the access network device also performs corresponding behaviors.

[0306] The following uses another example to describe how a terminal device determines a data transmission mode that needs to be used when performing cell handover between W cells. For example, the cell group information indicates at least one group, and each of the at least one group includes at least one of the W cells. For example, the groups indicated by the cell group information configured by the access network device for the terminal device include group 1 {cell1, cell2} and group 2 {cell3, cell4}.

[0307] The current serving cell (source cell) of the terminal device is cell 1. When the terminal device receives a handover command indicating a handover to cell 2, the terminal device can perform behavior 1 because both cell 1 and cell 2 belong to the same group. When the terminal device receives a handover command to be handed over from cell 2 to cell 3, the terminal device can perform behavior 2 because cell 2 and cell 3 do not belong to the same group.

[0308] Behavior 1 and / or Behavior 2 may be agreed upon in the protocol. For example, Behavior 1 includes at least one of PDCP maintenance, RLC maintenance, or MAC partial reset, and Behavior 2 includes at least one of PDCP data recovery, RLC re-establishment, or MAC reset. The specific contents of Behavior 1 and Behavior 2 are not limited and may include at least one possible behavior of the PDCP layer, the RLC layer, or the MAC layer. For specific behaviors, see the description of "Data Transmission Mode."

[0309] It can be understood that when multiple cells included in the same group belong to the same DU, this means that the PDCP and RLC layer configurations applied by the terminal device in the multiple cells may be maintained, and the MAC layer configurations applied by the terminal device in the multiple cells may be partially maintained. Therefore, when the source cell and the target cell belong to the same group, behavior 1 may include PDCP maintenance, RLC maintenance, and MAC partial reset. When multiple cells in different groups belong to different DUs (e.g., cell1 and cell3 belong to different DUs), this means that the PDCP, RLC, and MAC layer configurations applied by the terminal device in the multiple cells may need to be updated. Therefore, when the source cell and the target cell belong to different groups, behavior 2 may include PDCP data recovery, RLC re-establishment, and MAC reset.

[0310] Behavior 1 and / or Behavior 2 may alternatively be configured by an access network device. For example, at least one of (1) a PDCP layer behavior to be performed when the source cell and the target cell belong to the same group, (2) a PDCP layer behavior to be performed when the source cell and the target cell do not belong to the same group, (3) an RLC layer behavior to be performed when the source cell and the target cell belong to the same group, (4) an RLC layer behavior to be performed when the source cell and the target cell do not belong to the same group, (5) a MAC layer behavior to be performed when the source cell and the target cell belong to the same group, or (6) a MAC layer behavior to be performed when the source cell and the target cell do not belong to the same group is configured using an RRC message.

[0311] It should be understood that in this embodiment of the present application, there are multiple ways of expressing a group. For example, one group may be a list, and the list includes identifiers of multiple cells in the group. Optionally, the list further includes an identifier of the group. In another example, one group identifier may be configured for each cell, and cells with the same group identifier belong to the same group. For example, a group identifier is configured for cell1, and the same group identifier is configured for cell2. This way indicates that cell1 and cell2 belong to the same group.

[0312] In addition, in a CU-DU split scenario, for example, an access network device includes a CU and one or more DUs, and the CU may send cell group information to a terminal device and may further send the cell group information to each DU controlled by the CU. When the PDCP layer is located on the CU and the RLC layer and MAC layer are located on the DU, the PDCP layer behavior included in the data transmission mode may be determined by the CU, and the RLC layer behavior and MAC layer behavior included in the data transmission mode may be determined by the DU.

[0313] For example, with respect to PDCP layer behavior, in a possible implementation, after completing transmission of the handover command, the DU that sent the handover command notifies the CU of the identification information of the target cell. The CU also maintains cell group information, so that the CU can determine the PDCP layer behavior based on the groups to which the source cell and the target cell belong. In another possible implementation, after the terminal device accesses the target cell (e.g., after the terminal device successfully transmits an uplink message to the target cell), the DU to which the target cell belongs notifies the CU of the identification information of the target cell, so that the CU can determine the PDCP layer behavior based on the groups to which the source cell and the target cell belong. This implementation is also applicable to determining CU-side behavior in embodiments 1 to 3.

[0314] Regarding the RLC layer behavior and the MAC layer behavior, since the DU to which the target cell belongs also maintains the above-mentioned cell group information, the DU to which the target cell belongs can determine the RLC layer behavior and the MAC layer behavior based on the group to which the source cell and the target cell belong. This implementation form is also applicable to the determination of the DU side behavior in Embodiments 1 to 3.

[0315] In another possible embodiment, it may be understood that there may be a correspondence between cell group information and handover scenarios. For example, in scenario 1, two cells (i.e., a source cell and a target cell) may be managed by the same DU and may be in the same RLC group and the same MAC group. In scenario 2, the two cells may be managed by different DUs and may be in different RLC groups and different MAC groups. When there is a correspondence between cell group information and handover scenarios, the CU may not need to send cell group information to the DU, and the DU to which the target cell belongs may determine the RLC layer behavior and the MAC layer behavior based on the handover scenario. Specifically, the DU to which the target cell belongs may make a decision depending on whether the terminal device is handed over from a cell managed by the DU. For example, when a terminal device is handed over from cell 1 to cell 2, the DU to which cell 2 belongs may know that the source cell of the terminal device is also managed by the DU. Therefore, RLC maintenance and MAC maintenance may be performed. For example, when a terminal device is handed over from cell 1 to cell 3, the DU to which cell 3 belongs knows that the source cell of the terminal device is not managed by the DU, and therefore RLC re-establishment and MAC reset can be performed.

[0316] S803-b: The terminal device performs measurements on W cells to obtain beam level measurement results, and determines to be handed over from the first cell to the second cell based on the beam level measurement results.

[0317] S804-b: The terminal device sends handover completion information to an access network device in the second cell, where the handover completion information notifies the access network device that the terminal device has been handed over from the first cell to the second cell.

[0318] S805-b: The access network device and the terminal device perform data transmission in the second cell in a corresponding data transmission mode.

[0319] In addition, after the access network device sends the cell group information to the terminal device, if the access network device determines that at least one of the following conditions is met: the terminal device needs to enter an idle mode or an inactive mode, the terminal device needs to be handed over to a cell other than the W cells through Layer 3 handover, or the cell group information needs to be changed, the access network device may release the cell group information and / or instruct the terminal device to release the cell group information. For details, please refer to the description of embodiment 1.

[0320] According to the method in embodiment 4, cells are grouped, so that the configuration content can be effectively reduced, thereby effectively saving transmission resources. In addition, cells can be grouped separately based on the behavior of different protocol layers, so that the configuration is more flexible.

[0321] In embodiment 1, for each target cell, a data transmission mode for handover from a different cell to the target cell is configured. When there are a large number of cells for continuous handover, the configuration content in embodiment 1 is large. According to embodiment 4, the configuration content can be effectively simplified. In embodiment 2, each handover scenario corresponds to one data transmission mode. However, in some possible cases, different data transmission modes may exist in the same handover scenario (e.g., intra-DU cell handover). For example, cell A, cell B, and cell C are cells managed by the same DU, and random access does not need to be performed for handover from cell A to cell B to obtain uplink synchronization information for cell B, but needs to be performed for handover from cell A to cell C to obtain uplink synchronization information for cell C. According to embodiment 4, the data transmission mode may be separated from the handover scenario to improve configuration flexibility.

[0322] In embodiment 4, in a CU-DU separation scenario, the CU may transmit cell group information to the terminal device via the DU. In this way, after the terminal device is handed over, the terminal device and the target DU can separately determine the data transmission mode to be used based on the cell group information. In another possible embodiment, the CU may not transmit cell group information to the terminal device. In this case, after the terminal device is handed over, the source DU may determine the data transmission mode to be used based on the cell group information and transmit the data transmission mode information to the terminal device. In the above-mentioned scheme, in an intra-DU handover scenario, both the source DU (i.e., the target DU) and the terminal device know the data transmission mode to be used. In an inter-DU handover scenario, the target DU may autonomously determine the data transmission mode, or the terminal device may inform the target DU of the data transmission mode in the target cell.

[0323] Regarding the first to fourth embodiments, the following can be understood.

[0324] (1) Embodiments 1 to 4 are described using an example in which the serving cell of a terminal device is one cell. In another possible case, for example, when a terminal device operates in a dual connectivity mode, the solutions in embodiments 1 to 4 may be applied to a handover of a master node in dual connectivity, or to an addition or change of a secondary node (SN) / secondary cell group (SCG). In addition, when the above-mentioned CHO is applicable to an addition or change of a secondary node / secondary cell group, the CHO may also be referred to as a conditional primary SCG cell addition (CPA) or a conditional primary SCG cell change (CPC). A primary secondary cell group cell (PSCell) is a primary cell of a secondary node / secondary cell group.

[0325] (2) The step numbers in the flowcharts described in the first to fourth embodiments are examples of execution procedures and do not constitute limitations on the order in which the steps are executed. In the embodiments of the present application, there is no strict order of execution between steps that do not have a chronological dependency on each other. Not all steps shown in the flowcharts are necessarily required. Some steps may be deleted from the flowcharts based on actual requirements, or other possible steps may be added to the flowcharts based on actual requirements.

[0326] (3) The above focuses on the differences between different embodiments in Embodiments 1 to 4, and contents other than the differences may be mutually referenced in Embodiments 1 to 4. In addition, different implementation forms or different examples may be mutually referenced in the same embodiment.

[0327] The above mainly describes the solutions provided in the embodiments of the present application from the perspective of interactions between communication devices. It can be understood that, to implement the aforementioned functions, the access network device and the terminal device may include corresponding hardware structures and / or software modules for implementing the functions. Those skilled in the art will easily recognize that the embodiments of the present application can be implemented by hardware or a combination of hardware and computer software with reference to the units and algorithm steps in the examples described in the embodiments disclosed herein. Whether the functions are performed by hardware or by hardware driven by computer software depends on the specific application and design constraints of the technical solution. Those skilled in the art may use different methods to implement the described functions for each specific application, but such implementation should not be considered to exceed the scope of the present application.

[0328] In the embodiments of the present application, the access network device and the terminal device may be divided into functional units according to the above-mentioned method examples. For example, each functional unit may be obtained by dividing it according to its corresponding function, or two or more functions may be integrated into one unit. The integrated unit may be implemented in the form of hardware or in the form of a software functional unit.

[0329] When an integrated unit is used, FIG. 9 is a possible exemplary block diagram of an apparatus according to an embodiment of the present application. As shown in FIG. 9, the apparatus 900 may include a processing unit 902 and a communication unit 903. The processing unit 902 is configured to control and manage operation of the apparatus 900. The communication unit 903 is configured to support communication between the apparatus 900 and another device. Optionally, the communication unit 903, also referred to as a transceiver unit, may include a receiving unit and / or a transmitting unit configured to perform receiving and transmitting operations, respectively. The apparatus 900 may further include a storage unit 901 configured to store program codes and / or data of the apparatus 900.

[0330] The apparatus 900 may be the access network device in the aforementioned embodiment. The processing unit 902 may support the apparatus 900 in performing the operations of the access network device in the aforementioned method examples. Alternatively, the processing unit 902 may mainly perform internal actions of the access network device in the method examples, and the communication unit 903 may support communication between the apparatus 900 and another device.

[0331] For example, in one embodiment, the processing unit 902 is configured to determine that the first cell is a serving cell of the terminal device. The communication unit 903 is configured to send N sets of data transmission mode information for the terminal device to the terminal device in the first cell, where N is a positive integer. The N sets of data transmission mode information include first data transmission mode information corresponding to performing a handover of the terminal device from the second cell to the first cell via a first type of cell handover and / or second data transmission mode information corresponding to performing a handover of the terminal device from the second cell to a third cell via the first type of cell handover.

[0332] The apparatus 900 may be the terminal device in the aforementioned embodiment. The processing unit 902 may support the apparatus 900 in performing the operations of the terminal device in the aforementioned method examples. Alternatively, the processing unit 902 may mainly perform internal actions of the terminal device in the method examples, and the communication unit 903 may support communication between the apparatus 900 and another device.

[0333] For example, in one embodiment, the processing unit 902 is configured to determine that the first cell is a serving cell of the terminal device. The communication unit 903 is configured to receive N sets of data transmission mode information from an access network device in the first cell, where N is a positive integer. The N sets of data transmission mode information include first data transmission mode information corresponding to performing a handover of the terminal device from the second cell to the first cell via a first type of cell handover and / or second data transmission mode information corresponding to performing a handover of the terminal device from the second cell to a third cell via the first type of cell handover.

[0334] It should be understood that the division of the device into units described above is merely a logical division of function. During actual implementation, all or some of the units may be integrated into one physical entity or physically separated. In addition, all units in the device may be implemented in the form of software called by a processing element, or in the form of hardware, or some units may be implemented in the form of software called by a processing element and the remaining units in the form of hardware. For example, each unit may be a separately located processing element, or may be integrated into a chip of the device for implementation. In addition, each unit may alternatively be stored in memory in the form of a program called by a processing element of the device to perform the function of the unit. In addition, all or some of the units may be integrated or implemented independently. The processing element in this specification may also be referred to as a processor and may be an integrated circuit having signal processing capabilities. In an implementation process, the operations in the above-described methods or units may be implemented by using a hardware integrated logic circuit in the processor element, or may be implemented in the form of software called by the processing element.

[0335] In one example, the units in any one of the aforementioned devices may be one or more integrated circuits configured to implement the aforementioned methods, such as one or more application specific integrated circuits (ASICs), one or more digital signal processors (DSPs), one or more field programmable gate arrays (FPGAs), or a combination of at least two of these forms of integrated circuits. In another example, when a unit in an apparatus may be implemented in a form in which the processing element schedules a program, the processing element may be a processor, such as a general-purpose central processing unit (CPU) or another processor that can invoke a program. In yet another example, the units may be integrated and implemented in a form of a system-on-a-chip (SoC).

[0336] The unit configured to receive is an interface circuit of the device and is configured to receive a signal from another device. For example, when the device is implemented in the form of a chip, the receiving unit is an interface circuit of the chip and configured to receive a signal from another chip or device. The unit configured to transmit is an interface circuit of the device and is configured to transmit a signal to another device. For example, when the device is implemented in the form of a chip, the transmitting unit is an interface circuit of the chip and configured to transmit a signal to another chip or device.

[0337] FIG. 10 is a diagram illustrating the structure of an access network device according to one embodiment of the present technology. The access network device (or base station) may be used in the communication system illustrated in FIG. 1 to perform the functions of the access network device in the aforementioned method embodiment. As illustrated in FIG. 10, the access network device 100 may include one or more DUs 1001 and one or more CUs 1002. The DU 1001 may include at least one antenna 10011, at least one radio frequency unit 10012, at least one processor 10013, and at least one memory 10014. The DU 1001 is mainly configured to receive and transmit radio frequency signals, perform conversion between radio frequency signals and baseband signals, and perform part of baseband processing. The CU 1002 may include at least one processor 10022 and at least one memory 10021.

[0338] The CU 1002 is mainly configured to perform baseband processing and control the access network device. The DU 1001 and the CU 1002 can be physically located together, or in other words, can be physically located separately in a distributed base station. The CU 1002 is the control center of the access network device, and may also be referred to as a processing unit, and is mainly configured to complete baseband processing functions. For example, the CU 1002 can be configured to control the access network device to perform operation procedures related to the access network device in the above-mentioned method embodiments.

[0339] Also, as needed, the access network device 100 may include one or more radio frequency units, one or more DUs, and one or more CUs. The DU may include at least one processor 10013 and at least one memory 10014, the radio frequency unit may include at least one antenna 10011 and at least one radio frequency unit 10012, and the CU may include at least one processor 10022 and at least one memory 10021.

[0340] In one example, the CU 1002 may include one or more boards. The multiple boards may jointly support a radio access network of a single access standard (e.g., a 5G network) or may each support a radio access network of a different access standard (e.g., an LTE network, a 5G network, or another network). The memory 10021 and the processor 10022 may serve one or more boards. In other words, the memory and the processor may be located on each board. Alternatively, the multiple boards may share the same memory and the same processor. Further, necessary circuitry may be located on each board. The DU 1001 may include one or more boards. The multiple boards may jointly support a radio access network of a single access standard (e.g., a 5G network) or may each support a radio access network of a different access standard (e.g., an LTE network, a 5G network, or another network). The memory 10014 and the processor 10013 may serve one or more boards. In other words, the memory and processor can be located on each board, or alternatively, multiple boards can share the same memory and processor, and each board can further include any necessary circuitry.

[0341] The access network device shown in Figure 10 can implement each process related to the access network device in the above-mentioned method embodiment. The operations and / or functions of the modules in the access network device shown in Figure 10 are for implementing the corresponding procedures in the above-mentioned method embodiment. For details, please refer to the descriptions in the above-mentioned method embodiment. To avoid repetition, detailed descriptions will be omitted here as appropriate.

[0342] 11 is a diagram of the structure of a terminal device according to an embodiment of the present application. The terminal device may be used in the communication system shown in FIG. 1 and is configured to implement the operation of the terminal device in the above-described embodiment. As shown in FIG. 11, the terminal device includes an antenna 1110, a radio frequency unit 1120, and a signal processing unit 1130. The antenna 1110 is connected to the radio frequency unit 1120. In the downlink direction, the radio frequency unit 1120 receives information transmitted by a network device by using the antenna 1110 and transmits the information transmitted by the network device to the signal processing unit 1130 for processing. In the uplink direction, the signal processing unit 1130 processes the information of the terminal device and transmits the information to the radio frequency unit 1120. After processing the information of the terminal device, the radio frequency unit 1120 transmits the information to the network device by using the antenna 1110.

[0343] The signal processing unit 1130 may include a modem subsystem configured to process each communication protocol layer of data, and may further include a central processing subsystem configured to process the operating system and application layer of the terminal device, and may further include other subsystems such as a multimedia subsystem and a peripheral subsystem, where the multimedia subsystem is configured to control the camera, screen display, etc. of the terminal device, and the peripheral subsystem is configured to implement connection to other devices. The modem subsystem may be a separately disposed chip.

[0344] The modem subsystem may include one or more processing elements 1131, such as a main control CPU and another integrated circuit. In addition, the modem subsystem may further include a storage element 1132 and an interface circuit 1133. The storage element 1132 is configured to store data and programs. However, the programs for implementing the methods performed by the terminal device in the above-described methods need not be stored in the storage element 1132, but may be stored in a memory external to the modem subsystem and loaded by the modem subsystem for use. The interface circuit 1133 is configured to communicate with other subsystems.

[0345] The modem subsystem may be implemented by a chip. The chip includes at least one processing element and an interface circuit. The processing element is configured to execute steps of any method implemented by the terminal device. The interface circuit is configured to communicate with other devices. In one implementation, the units of the terminal device that implement the steps of the aforementioned method may be implemented by a program scheduled by the processing element. For example, an apparatus used in the terminal device includes a processing element and a storage element. The processing element invokes a program stored in the storage element to implement the method implemented by the terminal device in the aforementioned method embodiment. The storage element may be located on the same chip as the processing element, i.e., an on-chip storage element.

[0346] In another implementation, the program for performing the method performed by the terminal device in the aforementioned method may be in a storage element located on a different chip than the processing element, i.e., an off-chip storage element, in which case the processing element calls or loads the program from the off-chip storage element to the on-chip storage element to call and perform the method performed by the terminal device in the aforementioned method embodiment.

[0347] In yet another implementation, the unit of the terminal device that implements the steps of the aforementioned method may be configured as one or more processing elements. The processing elements are located in a modem subsystem. A processing element herein may be an integrated circuit, such as one or more ASICs, one or more DSPs, one or more FPGAs, or a combination of integrated circuit types. These integrated circuits may be integrated together to form a chip.

[0348] The units of a terminal device that implement the steps of the aforementioned method may be integrated together and implemented in the form of an SoC. An SoC chip is configured to implement the aforementioned method. At least one processing element and a storage element may be integrated into the chip, and the processing element calls a program stored in the storage element to implement the aforementioned method performed by the terminal device. Alternatively, at least one integrated circuit may be integrated into the chip to implement the aforementioned method performed by the terminal device. Alternatively, with reference to the aforementioned implementation forms, the functions of some units may be implemented by a program called by the processing element, and the functions of some units may be implemented by the integrated circuit.

[0349] It can be seen that the aforementioned apparatus used in the terminal device may include at least one processing element and an interface circuit. The at least one processing element is configured to perform any one of the methods performed by the terminal device provided in the aforementioned method embodiments. The processing element may perform some or all of the steps performed by the terminal device in a first manner, specifically by calling a program stored in a storage element, or may perform some or all of the steps performed by the terminal device in a second manner, specifically by using a hardware integrated logic circuit in the processor element in combination with an instruction, or may reliably perform some or all of the steps performed by the terminal device by combining the first and second manners.

[0350] The processing element in this specification may be similar to that described above and may be implemented by a processor. The function of the processing element may be the same as the function of the processing unit described in FIG. 9. For example, the processing element may be a general-purpose processor, such as a central processing unit, or may be one or more integrated circuits configured to implement the above-described method, such as one or more ASICs, one or more digital signal processors (DSPs), or one or more FPGAs, or a combination of at least two of the integrated circuit forms. The storage element may be implemented by a memory. The function of the storage element may be similar to the function of the storage unit described in FIG. 9. The storage element may be a memory or may be a collective term for multiple memories.

[0351] The terminal device shown in Fig. 11 may implement each process related to the terminal device in the above-mentioned method embodiments. The operations and / or functions of the modules in the terminal device shown in Fig. 11 are for implementing the corresponding procedures in the above-mentioned method embodiments. For details, please refer to the descriptions in the above-mentioned method embodiments. To avoid repetition, detailed descriptions will be omitted here as appropriate.

[0352] The terms "system" and "network" may be used interchangeably in the embodiments of this application. The term "at least one" means one or more, and "multiple" means two or more. The term "and / or" describes an association relationship between related objects and indicates that three relationships may exist. For example, A and / or B may indicate the following three cases: when only A is present, when both A and B are present, and when only B is present, where A and B may be singular or plural. The character " / " generally indicates an "or" relationship between related objects. "At least one item (moiety)" of the following or similar expressions refers to any combination of these items, including any combination of singular items (moieties) or multiple items (moieties). For example, "at least one of A, B, and C" includes A, B, C, AB, AC, BC, or ABC. Additionally, unless otherwise specified, ordinal numbers such as "first" and "second" in the embodiments of this application are used to distinguish between multiple objects and are not used to limit the order, chronological order, priority, or importance of the multiple objects.

[0353] Those skilled in the art should understand that the embodiments of the present application may be provided as a method, a system, or a computer program product. Therefore, the present application may use the form of a hardware-only embodiment, a software-only embodiment, or an embodiment having a combination of software and hardware. In addition, the present application may use the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk memory, CD-ROM, optical memory, etc.) containing computer-usable program code.

[0354] The present application is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to the present application. It should be understood that computer program instructions can be used to implement each process and / or each block in the flowcharts and / or block diagrams, and combinations of processes and / or blocks in the flowcharts and / or block diagrams. These computer program instructions may be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or another programmable data processing device to create a machine, such that the instructions executed by the processor of the computer or another programmable data processing device create an apparatus for implementing the specific functions in one or more processes in the flowcharts and / or one or more blocks in the block diagrams.

[0355] These computer program instructions may be stored in a computer-readable memory that can instruct a computer or another programmable data processing device to operate in a specific manner, such that the instructions stored in the computer-readable memory generate an artifact that includes an instruction apparatus that implements a specific function in one or more processes in the flowcharts and / or one or more blocks in the block diagrams.

[0356] The computer program instructions may alternatively be loaded onto a computer or other programmable data processing device such that a sequence of operations and steps are executed on the computer or other programmable device to produce a computer-implemented process. Thus, the instructions executed on the computer or other programmable device provide steps for implementing a specific function in one or more procedures in the flowcharts and / or one or more blocks in the block diagrams.

[0357] Those skilled in the art will appreciate that ExampleIt is apparent that various modifications and variations can be made to the present application without departing from the scope thereof, and the present application is intended to cover these modifications and variations of the present application, provided that they fall within the scope of the appended claims and their equivalents. [Explanation of symbols]

[0358] 10. Communication Systems 20 Access Network Devices 30 Terminal Devices 900 equipment 901 Storage Unit 902 Processing Unit 903 Communication Unit 100 Access Network Devices 1001 Distributed Unit (DU) 1002 Central Unit (CU) 10011 Antenna 10012 Radio Frequency Unit 10013 processor 10014 memory 10021 memory 10022 processor 1110 Antenna 1120 Radio Frequency Unit 1130 Signal Processing Unit 1131 Processing Elements 1132 Memory Elements 1133 Interface Circuit

Claims

1. 1. A communication method, the method being applied to an access network device or a module within the access network device, determining that the first cell is a serving cell of the terminal device; transmitting cell group information of W cells to the terminal device in the first cell, the W cells including the first cell; Including, The cell group information is for determining a data transmission mode corresponding to performing a handover of the terminal device from one cell among the W cells to another cell among the W cells via a first type cell handover, where W is an integer greater than 1; method.

2. the cell group information includes PDCP layer group information, the PDCP layer group information indicating at least one PDCP group, each of the at least one PDCP group including at least one of the W cells; When the one cell and the other cell are not in the same PDCP group, the data transmission mode includes performing PDCP data recovery; or When the one cell and the other cell are in the same PDCP group, the data transmission mode includes skipping performing PDCP data recovery. The method of claim 1.

3. The cell group information includes RLC layer group information, the RLC layer group information indicating at least one RLC group, each of the at least one RLC group including at least one of the W cells; When the one cell and the other cell are not in the same RLC group, the data transmission mode includes performing an RLC re-establishment; or When the one cell and the other cell are in the same RLC group, the data transmission mode includes skipping performing RLC re-establishment. The method of claim 1.

4. The cell group information indicates at least one group, each of which includes at least one of the W cells; When the one cell and the other cell are not in the same group, the data transmission mode includes performing PDCP data recovery and RLC re-establishment; or When the one cell and the other cell are in the same group, the data transmission mode includes performing PDCP maintenance and RLC maintenance. The method of claim 1.

5. The cell group information indicates at least one group, each of which includes at least one of the W cells; When the one cell and the other cell are not in the same group, the data transmission mode includes performing at least one of PDCP data recovery, RLC re-establishment, or MAC reset; or When the one cell and the other cell are in the same group, the data transmission mode includes performing at least one of PDCP maintenance, RLC maintenance, or MAC partial reset. The method of claim 1.

6. The method described in claim 1, wherein the first type of cell handover is a layer 1 / layer 2 handover.

7. The method of claim 1, wherein one group identifier is configured for each cell in the W cells, and cells having the same group identifier belong to the same group.

8. The method of claim 7, wherein the cell group information includes PDCP layer group information, the PDCP layer group information indicates at least one PDCP group, each of the at least one PDCP group including at least one of the W cells; When the one cell and the other cell are not in the same PDCP group, the data transmission mode includes performing PDCP re-establishment; or When the one cell and the other cell are in the same PDCP group, the data transmission mode includes skipping performing PDCP re-establishment. The method of claim 1.

9. The cell group information further includes RLC layer group information, wherein the RLC layer group information indicates at least one RLC group, each of the at least one RLC group including at least one of the W cells; When the one cell and the other cell are in the same PDCP group but not in the same RLC group, the data transmission mode further includes performing RLC re-establishment; or When the one cell and the other cell are in the same PDCP group and also in the same RLC group, the data transmission mode further includes skipping performing RLC re-establishment. The method of claim 8.

10. The method comprising: determining that the terminal device needs to enter an idle mode or an inactive mode; Releasing the cell group information; The method of claim 1 further comprising:

11. 1. A communication method, the method being applied to a terminal device or a module within the terminal device, receiving cell group information of W cells from an access network device in a first cell, the W cells including the first cell; determining a data transmission mode corresponding to performing a handover of the terminal device from one cell among the W cells to another cell among the W cells via a first type of cell handover based on the cell group information, where W is an integer greater than 1; A method comprising:

12. the cell group information includes PDCP layer group information, the PDCP layer group information indicating at least one PDCP group, each of the at least one PDCP group including at least one of the W cells; When the one cell and the other cell are not in the same PDCP group, the data transmission mode includes performing PDCP data recovery; or When the one cell and the other cell are in the same PDCP group, the data transmission mode includes skipping performing PDCP data recovery. The method of claim 11.

13. The cell group information includes RLC layer group information, the RLC layer group information indicating at least one RLC group, each of the at least one RLC group including at least one of the W cells; When the one cell and the other cell are not in the same RLC group, the data transmission mode includes performing an RLC re-establishment; or When the one cell and the other cell are in the same RLC group, the data transmission mode includes skipping performing RLC re-establishment. The method of claim 11.

14. The cell group information indicates at least one group, each of which includes at least one of the W cells; When the one cell and the other cell are not in the same group, the data transmission mode includes performing PDCP data recovery and RLC re-establishment; or When the one cell and the other cell are in the same group, the data transmission mode includes performing PDCP maintenance and RLC maintenance. The method of claim 11.

15. The cell group information indicates at least one group, each of which includes at least one of the W cells; When the one cell and the other cell are not in the same group, the data transmission mode includes performing at least one of PDCP data recovery, RLC re-establishment, or MAC reset; or When the one cell and the other cell are in the same group, the data transmission mode includes performing at least one of PDCP maintenance, RLC maintenance, or MAC partial reset. The method of claim 11.

16. The method of claim 11 , wherein the first type of cell handover is a Layer 1 / Layer 2 handover.

17. The method of claim 11, wherein one group identifier is configured for each cell in the W cells, and cells having the same group identifier belong to the same group.

18. The cell group information includes PDCP layer group information, the PDCP layer group information indicating at least one PDCP group, each of the at least one PDCP group including at least one of the W cells; When the one cell and the other cell are not in the same PDCP group, the data transmission mode includes performing PDCP re-establishment; or When the one cell and the other cell are in the same PDCP group, the data transmission mode includes skipping performing PDCP re-establishment. The method of claim 11.

19. The cell group information further includes RLC layer group information, the RLC layer group information indicating at least one RLC group, each of the at least one RLC group including at least one of the W cells; When the one cell and the other cell are in the same PDCP group but not in the same RLC group, the data transmission mode further includes performing RLC re-establishment; or When the one cell and the other cell are in the same PDCP group and also in the same RLC group, the data transmission mode further includes skipping performing RLC re-establishment.

19. The method of claim 18.

20. The method comprising: determining that the terminal device needs to enter an idle mode or an inactive mode; Releasing the cell group information; The method of claim 11 further comprising:

21. A communication device comprising a module configured to implement the method according to any one of claims 1 to 10.

22. A communications device comprising a module configured to implement a method according to any one of claims 11 to 20.

23. 11. A communications device comprising a processor, the processor coupled to a memory, the memory storing a computer program, the processor configured to invoke the computer program in the memory to enable the communications device to perform a method according to any one of claims 1 to 10.

24. 21. A communications device comprising a processor, the processor coupled to a memory, the memory storing a computer program, the processor configured to invoke the computer program in the memory to enable the communications device to perform a method according to any one of claims 11 to 20.

25. 11. A computer-readable storage medium storing a computer program or instructions that, when executed by a computer, performs the method of any one of claims 1 to 10.

26. 21. A computer-readable storage medium storing a computer program or instructions which, when executed by a computer, perform the method of any one of claims 11 to 20.

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