Communication method and apparatus

Abstract

The present application relates to a communication method and an apparatus. A terminal device transmits M compressed data packets. The M compressed data packets are obtained by compressing the M data packets based on a first buffer. The terminal device re-establishes a PDCP layer without resetting the first buffer. Then, the terminal device transmits N compressed data packets. The N compressed data packets are a part or all of the M compressed data packets. When re-establishing the PDCP layer, the terminal device does not reset the first buffer. In this case, when the terminal device needs to re-transmit a data packet, the terminal device may re-transmit a compressed data packet obtained previously, and does not need to compress the data packet again. This reduces the amount of compression times of the data packet, reduces the processing time of the terminal device, and improves the processing efficiency. In addition, the workload of the terminal device is reduced, so that the power consumption of the terminal device is reduced.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to Chinese Patent Application No. 202110086421.0, entitled "DATA TRANSMISSION METHOD, TERMINAL, AND NETWORK DEVICE," filed with the State Intellectual Property Office of China on January 22, 2021, which is incorporated herein by reference in its entirety. This application claims priority to Chinese Patent Application No. 202110230452.9, entitled "COMMUNICATION METHOD AND APPARATUS," filed with the State Intellectual Property Office of China on March 2, 2021, which is incorporated herein by reference in its entirety.

[0002] The present application relates to the field of communication technologies, and in particular to communication methods and devices. [Background technology]

[0003] In acknowledged mode (AM) transmission in long term evolution (LTE) systems, uplink data compression (UDC) technology is introduced and implemented in the packet data convergence protocol (PDCP) layer. For some data packets with large amounts of repeated content, such as data packets for transmitting session initiation protocol (SIP) in voice over long term evolution (VoLTE) network services, UDC technology is used to transmit different parts between data packets to reduce the amount of data being transmitted.

[0004] When a terminal device undergoes cell handover, the terminal device re-establishes the PDCP layer, and a buffer corresponding to the UDC technology is also reset. The buffer is used to compress data packets. However, before the cell handover, the base station may not correctly receive data packets from the terminal device. For example, the terminal device may transmit multiple data packets, and some of the data packets may not be received by the base station. Therefore, the terminal device needs to retransmit the data packets. Because the buffer used to compress the data packets is reset, when retransmitting the data packets, the terminal device needs to recompress the data packets based on the reset buffer. That is, the terminal device may need to compress the same data packet twice. This will undoubtedly increase the processing time of the terminal device and reduce processing efficiency. Summary of the Invention [Means for solving the problem]

[0005] SUMMARY OF THE INVENTION Embodiments of the present application provide communication methods and apparatuses to reduce the amount of compression performed by a terminal device, and correspondingly improve the processing efficiency of the terminal device.

[0006] According to a first aspect, a first communication method is provided. The method may be executed by a terminal device, or may be executed by a chip system or another functional module. The chip system or functional module may implement the functions of the terminal device. The method includes: transmitting M compressed data packets, where the M compressed data packets are obtained by compressing the M data packets based on a first buffer, where M is a positive integer; re-establishing a PDCP layer without resetting the first buffer; and transmitting N compressed data packets, where the N compressed data packets are some or all of the M compressed data packets, where N is a positive integer less than or equal to M.

[0007] In this embodiment of the present application, when the PDCP layer is re-established, the terminal device does not reset the first buffer. In this case, when the terminal device needs to retransmit a data packet, the terminal device may retransmit the previously obtained compressed data packet, and there is no need to re-compress the data packet. This reduces the number of times the data packet is compressed, reduces the processing time of the terminal device, and improves processing efficiency. Furthermore, the workload of the terminal device is reduced, and therefore the power consumption of the terminal device is reduced.

[0008] In relation to the first aspect, in a first optional implementation of the first aspect, the method further includes a step of receiving a status report, where the status report indicates compressed data packets received by the network device (the first network device or the second network device). For example, the status report indicates K compressed data packets. After receiving the status report, the terminal device may know that the network device will receive K compressed data packets. For example, the status report may be implemented by using a bitmap. The amount of bits included in the bitmap may be M, and the M bits correspond one-to-one to the M compressed data packets. If the network device receives a compressed data packet, the bit corresponding to the compressed data packet is set to "1". If the network device does not receive a compressed data packet, the bit corresponding to the compressed data packet is set to "0". In this way, the terminal device can quickly determine which compressed data packets are received by the network device. As another example, the status report may include sequence numbers of compressed data packets received by the network device and / or may include sequence numbers of compressed data packets not received by the network device. In this way, the terminal device can determine which compressed data packets are received by the network device.

[0009] In relation to the first optional implementation of the first aspect, in a second optional implementation of the first aspect, the N compressed data packets do not include compressed data packets received by a network device (first network device or second network device). When the network device sends a status report to the terminal device and the status report indicates compressed data packets received by the network device, the terminal device no longer needs to send compressed data packets received by the network device, and only needs to send compressed data packets that were not received by the network device. In this way, the amount of data retransmitted by the terminal device can be reduced, and transmission overhead can be reduced.

[0010] In relation to the first aspect, the first optional implementation of the first aspect, or the second optional implementation of the first aspect, in a third optional implementation of the first aspect, the data packet having the lowest sequence number among the N compressed data packets is the data packet having the lowest sequence number among the data packets not successfully received by the network device. After completing cell handover or re-establishing the PDCP layer, the terminal device may retransmit the N compressed data packets to the network device (the first network device or the second network device). The terminal device may transmit the N compressed data packets in ascending order of the sequence numbers of the compressed data packets, starting from the first compressed data packet that is not determined to be successfully received by the network device. For example, the first compressed data packet among the N compressed data packets (or the compressed data packet having the lowest sequence number among the N compressed data packets) may be the first compressed data packet not successfully received by the first network device (or the compressed data packet having the lowest sequence number among the data packets not successfully received by the first network device). In this way, the packet loss rate of the first network device may be reduced.

[0011] In relation to the first aspect or any one of the first optional implementation of the first aspect to the third optional implementation of the first aspect, in a fourth optional implementation of the first aspect, the method further includes a step of transmitting capability information, where the capability information indicates that continuing to use the first buffer is supported. The network device (the first network device or the second network device) can determine whether the terminal device supports continuing to use the first buffer based on the capability information. If the terminal device supports continuing to use the first buffer, the network device may indicate to the terminal device to continue using the first buffer. If the terminal device does not support continuing to use the first buffer, the network device may not indicate to the terminal device to continue using the first buffer or may indicate to the terminal device to reset the first buffer. Alternatively, the terminal device may not transmit the capability information. There may be cases where the network device determines whether to indicate to the terminal device to continue using the first buffer based on another factor, or where whether the terminal device continues to use the first buffer is specified by a protocol, etc.

[0012] In relation to the first aspect or any one of the first optional implementation of the first aspect to the fourth optional implementation of the first aspect, in a fifth optional implementation of the first aspect, the method further includes receiving a handover command, where the handover command instructs the mobile station to perform a cell handover or re-establish a PDCP layer, and further instructs the mobile station to continue using the first buffer. For example, the handover command includes first indication information, and the first indication information may indicate re-establishing the PDCP layer or indicating performing a cell handover. Optionally, the handover command may further include second indication information. The second indication information may indicate continuing to use the first buffer, or the second indication information may indicate not resetting the first buffer when the PDCP layer is re-established. Alternatively, the second indication information may not be included in the handover command, and the first network device may send the second indication information to the terminal device by using another message. Alternatively, for example, if the protocol specifies that the first buffer continues to be used or that the first buffer is not reset when the PDCP layer is re-established, the first network device may not need to send the second indication information.

[0013] In relation to the first aspect or any one of the first optional implementation to the fifth optional implementation of the first aspect, in a sixth optional implementation of the first aspect, the first buffer corresponds to a first radio bearer, and the first radio bearer includes some or all of the radio bearers of the terminal device. For example, for radio bearers for which the terminal device is configured to use the compression technology provided in this embodiment of the present application, one radio bearer may correspond to one buffer, and there is a one-to-one correspondence between the radio bearer and the buffer. Alternatively, multiple radio bearers may correspond to one buffer. For example, space may be allocated separately to different radio bearers in the buffer so that the amount of the buffer can be reduced.

[0014] In relation to the first aspect or any one of the first optional implementation of the first aspect to the sixth optional implementation of the first aspect, in a seventh optional implementation of the first aspect, the step of transmitting M compressed data packets includes transmitting M compressed data packets to the first network device, and the step of transmitting N compressed data packets includes transmitting N compressed data packets to the first network device. If the cell handover process of the terminal device is a co-site handover process, specifically, if the terminal device accesses the first network device before performing the cell handover and continues to access the first network device after performing the cell handover, the terminal device transmits M compressed data packets or N compressed data packets to the first network device.

[0015] In relation to the first aspect or any one of the first optional implementation of the first aspect to the sixth optional implementation of the first aspect, in an eighth optional implementation of the first aspect, the step of transmitting M compressed data packets includes transmitting M compressed data packets to a first network device, where the first network device is a network device accessed by the terminal device before the terminal device performs a cell handover, and the step of transmitting N compressed data packets includes transmitting N compressed data packets to a second network device, where the first network device is a network device accessed by the terminal device after the terminal device performs a cell handover. If the cell handover process of the terminal device is an inter-site handover process, specifically, if the terminal device accesses a first network device before performing the cell handover and accesses a second network device after performing the cell handover, and the terminal device may send M compressed data packets before the cell handover and may send N compressed data packets after the cell handover, the terminal device may send M compressed data packets to the first network device and send N compressed data packets to the second network device.

[0016] According to a second aspect, a second communication method is provided. The method may be performed by a first network device, or may be performed by a chip system or another functional module. The chip system or functional module may implement the functions of the first network device. For example, the first network device may be an access network device, such as a base station. The method includes: receiving K compressed data packets from a terminal device, where the K compressed data packets are obtained by compressing the K data packets based on a first buffer, where K is a positive integer; and re-establishing a PDCP layer without resetting a second buffer, where the second buffer is used by the first network device to decompress the data packets compressed based on the first buffer.

[0017] If the terminal device does not reset the first buffer when re-establishing the PDCP layer, the first network device correspondingly does not reset the second buffer corresponding to the first buffer. When the terminal device needs to retransmit a data packet, the terminal device may retransmit the previously obtained compressed data packet, and the data packet does not need to be compressed again. This reduces the number of times the data packet is compressed, reduces the processing time of the terminal device, and improves processing efficiency. Furthermore, the workload of the terminal device is reduced, thereby reducing the power consumption of the terminal device. If the first network device does not reset the second buffer, the status of the first buffer and the status of the second buffer may be consistent. Therefore, the first network device can decompress the compressed data packet from the terminal device, and thus the packet loss rate of the first network device is reduced.

[0018] In relation to the second aspect, in a first optional implementation of the second aspect, the sequence numbers of the K data packets and the sequence numbers of the data packets decompressed by the first network device are discontinuous. For example, the sequence numbers of the K compressed data packets and the sequence number of the last data packet successfully decompressed by the first network device and delivered to an upper layer are discontinuous, indicating that the first network device has unreceived compressed data packets, and the unreceived compressed data packets affect the decompression of the K compressed data packets by the first network device.

[0019] In relation to the implementation of the second aspect or the first optional aspect of the second aspect, in a second optional implementation of the second aspect, the method further includes a step of transmitting K compressed data packets to a second network device, where the second network device is a network device accessed by the terminal device after the terminal device performs a cell handover, and the first network device is a network device accessed by the terminal device before the terminal device performs the cell handover. For example, the cell handover process of the terminal device is an inter-site handover process. Specifically, the terminal device accesses the first network device before performing the cell handover and accesses the second network device after performing the cell handover. In this case, since the terminal device performs the cell handover, the first network device does not need to decompress the K compressed data packets, but may forward or transmit the K compressed data packets to the second network device via an interface between the network devices (e.g., an Xn interface) so that the second network device processes the K compressed data packets.

[0020] In relation to the second aspect, the first optional implementation of the second aspect, or the second optional implementation of the second aspect, in a third optional implementation of the second aspect, the method further includes the step of sending indication information to a second network device, where the indication information indicates the content of a second buffer, the content of the second buffer is used to update a third buffer, and the third buffer is used by the second network device to decompress the compressed data packet based on the first buffer, the second network device is a network device accessed by the terminal device after the terminal device performs a cell handover, and the first network device is a network device accessed by the terminal device before the terminal device performs the cell handover. For example, the cell handover process of the terminal device is an inter-site handover process. Specifically, the terminal device accesses the first network device before performing the cell handover, and accesses the second network device after performing the cell handover. In this case, the first network device may indicate the contents of the second buffer to the second network device, and the second network device may update a third buffer maintained by the second network device based on the contents of the second buffer, so that the status of the third buffer is consistent with the status of the first buffer, and the second network device can correctly decompress compressed data packets from the terminal device.

[0021] In relation to the second aspect or any one of the first optional implementation of the second aspect to the third optional implementation of the second aspect, in a fourth optional implementation of the second aspect, the method further includes: a step of sending a first message to a second network device, the first message being used to inquire whether the terminal device is supported to continue using the first buffer, the second network device being a network device accessed by the terminal device after the terminal device performs a cell handover, and the first network device being a network device accessed by the terminal device before the terminal device performs the cell handover; and a step of receiving a second message from the second network device by the first network device, the second message indicating that the terminal device is supported to continue using the first buffer. For example, the cell handover process of the terminal device is an inter-site handover process. Specifically, the terminal device accesses the first network device before performing the cell handover, and accesses the second network device after performing the cell handover. In this case, the first network device may inquire whether the second network device supports the terminal device continuing to use the first buffer. For example, if the second network device does not support the terminal device continuing to use the first buffer, the first network device may configure the terminal device to reset the first buffer so that the behavior of the terminal device matches the behavior supported by the second network device.

[0022] In relation to the implementation of the second aspect or the first optional aspect of the second aspect, in a fifth optional implementation of the second aspect, the method further includes a step of sending a status report to the terminal device, the status report indicating that the first network device has received K compressed data packets.

[0023] In relation to the fifth optional implementation of the second aspect, in a sixth optional implementation of the second aspect, the method further includes a step of receiving N compressed data packets from a terminal device, where the N compressed data packets are some or all of the M compressed data packets, the K compressed data packets are some or all of the M compressed data packets, the sequence numbers of the M data packets are consecutive, the M compressed data packets are obtained by compressing the M data packets based on the first buffer, M is a positive integer, N is a positive integer less than or equal to M, and K is a positive integer less than or equal to M.

[0024] In relation to the sixth optional implementation of the second aspect, in a seventh optional implementation of the second aspect, the N compressed data packets do not include K compressed data packets.

[0025] In relation to the fifth optional implementation of the second aspect, the sixth optional implementation of the second aspect, or the seventh optional implementation of the second aspect, in an eighth optional implementation of the second aspect, the data packet having the smallest sequence number among the N compressed data packets is the data packet having the smallest sequence number among the data packets that are not successfully received by the first network device.

[0026] In relation to the second aspect or any one of the first optional implementation of the second aspect to the eighth optional implementation of the second aspect, in a ninth optional implementation of the second aspect, the method further includes a step of receiving capability information from the terminal device, wherein the capability information indicates that the terminal device supports continuing to use the first buffer.

[0027] In relation to the second aspect or any one of the first optional implementation of the second aspect to the ninth optional implementation of the second aspect, in a tenth optional implementation of the second aspect, the method further includes a step of sending a handover command to the terminal device, the handover command instructing the terminal device to perform a cell handover or re-establish a PDCP layer, and further instructing the terminal device to continue using the first buffer.

[0028] In relation to the second aspect or any one of the first optional implementation of the second aspect to the tenth optional implementation of the second aspect, in an eleventh optional implementation of the second aspect, the first buffer corresponds to a first radio bearer, and the first radio bearer includes some or all of the radio bearers of the terminal device.

[0029] For the technical effects brought about by the second aspect or some optional implementations, please refer to the description of the technical effects of the first aspect or the corresponding implementations.

[0030] According to a third aspect, a third communication method is provided. The method may be performed by a second network device, or may be performed by a chip system or another functional module. The chip system or functional module may implement the functions of the second network device. For example, the second network device is an access network device, such as a base station. The method includes the steps of receiving K compressed data packets from a first network device, where the K compressed data packets are obtained by compressing the K data packets based on a first buffer, where the second network device is a network device accessed by the terminal device after the terminal device performs a cell handover, and where the first network device is a network device accessed by the terminal device before the terminal device performs a cell handover; receiving indication information from the first network device, where the indication information indicates the contents of a second buffer, where the second buffer is used by the first network device to decompress the data packets compressed based on the first buffer; and updating a third buffer based on the contents of the second buffer, where the third buffer is used by the second network device to decompress the data packets compressed based on the first buffer.

[0031] In relation to the third aspect, in a first optional implementation of the third aspect, the sequence numbers of the K data packets and the sequence numbers of the data packets received by the second network device are discontinuous.

[0032] In relation to the third aspect or the first optional implementation of the third aspect, in a second optional implementation of the third aspect, the method further includes a step of receiving N compressed data packets from a terminal device, wherein the N compressed data packets are some or all of the M compressed data packets, the K compressed data packets are some or all of the M compressed data packets, the sequence numbers of the M data packets are consecutive, and the M compressed data packets are obtained by compressing the M data packets based on the first buffer, where M is a positive integer, N is a positive integer less than or equal to M, and K is a positive integer less than or equal to M.

[0033] In relation to the third aspect, the first optional implementation of the third aspect, or the second optional implementation of the third aspect, in a third optional implementation of the third aspect, the method further includes the steps of receiving a first message from a first network device, where the first message is used to inquire whether the terminal device is supported to continue using the first buffer, and sending a second message to the first network device, where the second message indicates that the terminal device is supported to continue using the first buffer.

[0034] In relation to the third aspect or any one of the first optional implementation of the third aspect to the third optional implementation of the third aspect, in a fourth optional implementation of the third aspect, the method further includes a step of sending a status report to the terminal device, the status report indicating that the second network device has received K compressed data packets.

[0035] In relation to the fourth optional implementation of the third aspect, in a fifth optional implementation of the third aspect, the N compressed data packets do not include K compressed data packets.

[0036] In relation to the third aspect or any one of the first optional implementation of the third aspect to the fifth optional implementation of the third aspect, in a sixth optional implementation of the third aspect, the data packet having the smallest sequence number among the N compressed data packets is the data packet having the smallest sequence number among the data packets that are not successfully received by the second network device.

[0037] In relation to the third aspect or any one of the first optional implementation of the third aspect to the sixth optional implementation of the third aspect, in a seventh optional implementation of the third aspect, the first buffer corresponds to a first radio bearer, and the first radio bearer includes some or all of the radio bearers of the terminal device.

[0038] For technical effects provided by the third aspect or optional implementations, please refer to the description of the technical effects of the first aspect or corresponding implementations and / or refer to the description of the technical effects of the second aspect or corresponding implementations.

[0039] A method according to one or more of the first, second, or third aspects relates to an uplink compression process.

[0040] According to a fourth aspect, a fourth communication method is provided. The method may be performed by a first network device, or may be performed by a chip system or another functional module. The chip system or functional module may implement the functions of the first network device. For example, the first network device is an access network device, such as a base station. The method includes: transmitting M compressed data packets to a terminal device, where the M compressed data packets are obtained by compressing the M data packets based on a first buffer, where M is a positive integer; and re-establishing a PDCP layer without resetting the first buffer.

[0041] In this embodiment of the present application, when re-establishing the PDCP layer, the first network device does not reset the first buffer. In this case, when the first network device needs to retransmit a data packet, the first network device may retransmit the previously obtained compressed data packet, and does not need to compress the data packet again. This reduces the number of times the data packet is compressed, reduces the processing time of the first network device, and improves processing efficiency. Furthermore, since the workload of the first network device is reduced, the power consumption of the first network device is reduced.

[0042] In relation to the fourth aspect, in a first optional implementation of the fourth aspect, the method further includes a step of transmitting indication information to a second network device, wherein the indication information indicates the contents of a first buffer, the contents of the first buffer are used to update a second buffer, and the second buffer is used by the second network device to compress data packets, and the first network device is a network device accessed by the terminal device before the terminal device performs a cell handover, and the second network device is a network device accessed by the terminal device after the terminal device performs a cell handover.

[0043] In relation to the implementation of the fourth aspect or the first optional aspect of the fourth aspect, in a second optional implementation of the fourth aspect, the method further includes the steps of: sending a first message to a second network device, wherein the first message is used to inquire whether the terminal device is supported to continue using the third buffer, the first network device being a network device accessed by the terminal device before the terminal device performs a cell handover, and the second network device being a network device accessed by the terminal device after the terminal device performs a cell handover; and receiving a second message from the second network device, wherein the second message indicates that the terminal device is supported to continue using the third buffer.

[0044] In relation to the fourth aspect, in a third optional implementation of the fourth aspect, the method further includes a step of receiving a status report from the terminal device, the status report indicating compressed data packets received by the terminal device.

[0045] In relation to the third optional implementation of the fourth aspect, in a fourth optional implementation of the fourth aspect, the method further includes a step of transmitting N compressed data packets to a terminal device, where the N compressed data packets are some or all of the M compressed data packets, and N is a positive integer less than or equal to M.

[0046] In relation to the fourth optional implementation of the fourth aspect, in a fifth optional implementation of the fourth aspect, the N compressed data packets do not include compressed data packets received by the terminal device.

[0047] In relation to the third optional implementation of the fourth aspect, the fourth optional implementation of the fourth aspect, or the fifth optional implementation of the fourth aspect, in a sixth optional implementation of the fourth aspect, the data packet having the smallest sequence number among the N compressed data packets is the data packet having the smallest sequence number among the data packets that are not successfully received by the terminal device.

[0048] In relation to the fourth aspect or any one of the first optional implementation of the fourth aspect to the sixth optional implementation of the fourth aspect, in a seventh optional implementation of the fourth aspect, the method further includes a step of receiving capability information from a terminal device, where the capability information indicates that the terminal device supports continuing to use a third buffer, the third buffer being used by the terminal device to decompress data packets compressed based on the first buffer or the second buffer, and the second buffer being used by a second network device to compress data packets, where the second network device is a network device accessed by the terminal device after the terminal device performs a cell handover.

[0049] In relation to the fourth aspect or any one of the first optional implementation of the fourth aspect to the seventh optional implementation of the fourth aspect, in an eighth optional implementation of the fourth aspect, the method further includes a step of sending a handover command to the terminal device, wherein the handover command instructs the terminal device to perform a cell handover or re-establish a PDCP layer, and further instructs the terminal device to continue using the third buffer, wherein the third buffer is used by the terminal device to decompress data packets compressed based on the first buffer or the second buffer, and the second buffer is used by the second network device to compress the data packets, and the second network device is a network device accessed by the terminal device after the terminal device performs the cell handover.

[0050] For technical effects provided by the fourth aspect or optional implementations, please refer to the description of the technical effects of the first aspect or corresponding implementation, and / or refer to the description of the technical effects of the second aspect or corresponding implementation, and / or refer to the description of the technical effects of the third aspect or corresponding implementation.

[0051] According to a fifth aspect, a fifth communication method is provided. The method may be performed by a second network device, or may be performed by a chip system or another functional module. The chip system or functional module may implement the functions of the second network device. For example, the second network device is an access network device, such as a base station. The method includes receiving indication information from a first network device, the indication information indicating the contents of a first buffer, the first buffer being used by the first network device to compress data packets, the second network device being a network device accessed by the terminal device after the terminal device performs cell handover, and the first network device being a network device accessed by the terminal device before the terminal device performs cell handover; and updating a second buffer based on the contents of the first buffer, the second buffer being used by the second network device to compress data packets.

[0052] In relation to the fifth aspect, in a first optional implementation of the fifth aspect, the method further includes the steps of receiving a first message from a first network device, where the first message is used to inquire whether the terminal device is supported to continue using the third buffer, and sending a second message to the first network device, where the second message indicates that the terminal device is supported to continue using the third buffer.

[0053] In relation to the fifth aspect or the first optional implementation of the fifth aspect, in a second optional implementation of the fifth aspect, the method further includes a step of receiving a status report from the terminal device, the status report indicating compressed data packets received by the terminal device.

[0054] In relation to the second optional implementation of the fifth aspect, in a third optional implementation of the fifth aspect, the method further includes a step of compressing data packets based on the updated second buffer to obtain N compressed data packets, and a step of transmitting the N compressed data packets to the terminal device.

[0055] In relation to the third optional implementation of the fifth aspect, in a fourth optional implementation of the fifth aspect, the N compressed data packets do not include compressed data packets received by the terminal device.

[0056] In relation to the third optional implementation of the fifth aspect or the fourth optional implementation of the fifth aspect, in a fifth optional implementation of the fifth aspect, the data packet having the smallest sequence number among the N compressed data packets is the data packet having the smallest sequence number among the data packets that are not successfully received by the terminal device.

[0057] For technical effects provided by the fifth aspect or optional implementations, please refer to the description of the technical effects of the first aspect or corresponding implementations, and / or refer to the description of the technical effects of the second aspect or corresponding implementations, and / or refer to the description of the technical effects of the third aspect or corresponding implementations.

[0058] According to a sixth aspect, a sixth communication method is provided. The method may be executed by a terminal device, or may be executed by a chip system or another functional module. The chip system or functional module can implement the functions of the terminal device. The method includes: receiving K compressed data packets, where the K compressed data packets are obtained by compressing the K data packets based on a first buffer; re-establishing a PDCP layer without resetting a third buffer; receiving N compressed data packets, where the N compressed data packets are obtained by compressing N data packets based on a second buffer, where both K and N are positive integers; and decompressing the K compressed data packets and the N compressed data packets based on the third buffer, or decompressing the N compressed data packets based on the third buffer.

[0059] In relation to the sixth aspect, in a first optional implementation of the sixth aspect, the step of receiving K compressed data packets includes receiving K compressed data packets from the first network device, and the step of receiving N compressed data packets includes receiving N compressed data packets from the first network device.

[0060] In relation to the first optional implementation of the sixth aspect, in a second optional implementation of the sixth aspect, the first buffer and the second buffer are the same buffer, and the first buffer is maintained by the first network device.

[0061] In relation to the sixth aspect, in a third optional implementation of the sixth aspect, the step of receiving K compressed data packets includes receiving K compressed data packets from a first network device, the step of receiving N compressed data packets includes receiving N compressed data packets from a second network device, the second network device being a network device accessed by the terminal device after the terminal device performs a cell handover, and the first network device being a network device accessed by the terminal device before the terminal device performs a cell handover.

[0062] In relation to the implementation of the third option of the sixth aspect, in the implementation of the fourth option of the sixth aspect, the first buffer is maintained by the first network device and the second buffer is maintained by the second network device.

[0063] In relation to the sixth aspect or the first optional implementation of the sixth aspect to the fourth optional implementation of the sixth aspect, in a fifth optional implementation of the sixth aspect, the sequence numbers of the K data packets and the sequence numbers of the data packets decompressed by the terminal device are discontinuous.

[0064] In relation to the sixth aspect or the first optional implementation of the sixth aspect to the fifth optional implementation of the sixth aspect, in the sixth optional implementation of the sixth aspect, the data packet having the smallest sequence number among the N compressed data packets is the data packet having the smallest sequence number among the data packets that are not successfully received by the terminal device.

[0065] In relation to the sixth aspect or the first optional implementation of the sixth aspect to the sixth optional implementation of the sixth aspect, in a seventh optional implementation of the sixth aspect, the method further includes a step of transmitting a status report, wherein the status report indicates that the terminal device has received K compressed data packets.

[0066] In relation to the seventh optional implementation of the sixth aspect, in an eighth optional implementation of the sixth aspect, the N compressed data packets do not include K compressed data packets.

[0067] In relation to the sixth aspect, or the first optional implementation of the sixth aspect to the eighth optional implementation of the sixth aspect, in a ninth optional implementation of the sixth aspect, the method further includes a step of receiving a handover command, the handover command instructing the terminal device to perform a cell handover or re-establish a PDCP layer, and further instructing the terminal device to continue using the third buffer.

[0068] In relation to the sixth aspect, or the first optional implementation of the sixth aspect to the ninth optional implementation of the sixth aspect, in a tenth optional implementation of the sixth aspect, the method further includes a step of transmitting capability information, wherein the capability information indicates that the terminal device supports continuing to use the third buffer.

[0069] For technical effects provided by the sixth aspect or optional implementations, please refer to the description of the technical effects of the first aspect or corresponding implementations, and / or refer to the description of the technical effects of the second aspect or corresponding implementations, and / or refer to the description of the technical effects of the third aspect or corresponding implementations.

[0070] A method according to any one or more of the fourth, fifth or sixth aspects relates to a downlink compression process.

[0071] According to a seventh aspect, a seventh communication method is provided. The method may be executed by a terminal device, or may be executed by a chip system or another functional module. The chip system or functional module may implement the functions of the terminal device. The method includes: receiving a handover command, the handover command including first indication information and second indication information, the first indication information indicating to re-establish a PDCP layer or perform a cell handover, and the second indication information indicating to the terminal device to continue using a first buffer, the first buffer being used by the terminal device to compress data packets; and re-establishing the PDCP layer without resetting the first buffer.

[0072] In relation to the seventh aspect, in a first optional implementation of the seventh aspect, the method further includes a step of receiving a status report, the status report indicating compressed data packets received by the network device.

[0073] In relation to the first optional implementation of the seventh aspect, in a second optional implementation of the seventh aspect, the method further includes a step of transmitting N compressed data packets in ascending order of sequence numbers of the compressed data packets, starting from a first compressed data packet that is not determined to be received successfully, where N is a positive integer.

[0074] In relation to the second optional implementation of the seventh aspect, in a third optional implementation of the seventh aspect, the step of transmitting N compressed data packets in ascending order of sequence numbers of the compressed data packets, starting from a first compressed data packet that is not determined to be received successfully, includes performing integrity protection and encryption processing on the N compressed data packets, and transmitting the processed N compressed data packets.

[0075] In relation to the seventh aspect or any one of the first optional implementation of the seventh aspect to the third optional implementation of the seventh aspect, in a fourth optional implementation of the seventh aspect, the method further includes a step of sending capability information, wherein the capability information indicates that continuing to use the first buffer is supported.

[0076] In relation to the seventh aspect or any one of the first optional implementation of the seventh aspect to the fourth optional implementation of the seventh aspect, in a fifth optional implementation of the seventh aspect, the first buffer corresponds to a first radio bearer, and the first radio bearer includes some or all of the radio bearers of the terminal device.

[0077] For technical effects provided by the seventh aspect or optional implementations, please refer to the description of the technical effects of the first aspect or corresponding implementations, and / or refer to the description of the technical effects of the second aspect or corresponding implementations, and / or refer to the description of the technical effects of the third aspect or corresponding implementations.

[0078] According to an eighth aspect, an eighth communication method is provided. The method may be executed by a first network device, or may be executed by a chip system or another functional module. The chip system or functional module may implement the functions of the first network device. For example, the first network device is an access network device, such as a base station. The method includes: sending a handover command to a terminal device, the handover command including first indication information and second indication information, the first indication information indicating to reestablish a PDCP layer or perform a cell handover, the second indication information indicating to continue using a first buffer, and the first buffer being used by the terminal device to compress data packets; and reestablishing the PDCP layer without resetting the second buffer, the second buffer being used by the first network device to decompress data packets compressed based on the first buffer.

[0079] In relation to the eighth aspect, in a first optional implementation of the eighth aspect, the method further includes a step of transmitting K compressed data packets to a second network device, where the K compressed data packets are from a terminal device, the second network device is a network device accessed by the terminal device after the terminal device performs a cell handover, and the first network device is a network device accessed by the terminal device before the terminal device performs a cell handover.

[0080] In relation to the eighth aspect or the first optional implementation of the eighth aspect, in a second optional implementation of the eighth aspect, the method further includes a step of sending indication information to a second network device, wherein the indication information indicates the contents of a second buffer, the contents of the second buffer are used to update a third buffer, and the third buffer is used by the second network device to decompress data packets compressed based on the first buffer, the second network device being a network device accessed by the terminal device after the terminal device performs a cell handover, and the first network device being a network device accessed by the terminal device before the terminal device performs a cell handover.

[0081] In relation to the eighth aspect, the first optional implementation of the eighth aspect, or the second optional implementation of the eighth aspect, in a third optional implementation of the eighth aspect, the method further includes a step of sending a first message to a second network device, where the first message is used to inquire whether the terminal device is supported to continue using the first buffer, the second network device being a network device accessed by the terminal device after the terminal device performs a cell handover, and the first network device being a network device accessed by the terminal device before the terminal device performs the cell handover; and a step of receiving a second message from the second network device by the first network device, where the second message indicates that the terminal device is supported to continue using the first buffer.

[0082] In relation to the eighth aspect, in a fourth optional implementation of the eighth aspect, the method further includes a step of sending a status report to the terminal device, wherein the status report indicates the compressed data packets received by the first network device.

[0083] In relation to the fourth optional implementation of the eighth aspect, in a fifth optional implementation of the eighth aspect, the method further includes a step of receiving N compressed data packets from a terminal device, wherein the data packet having the smallest sequence number among the N compressed data packets is the data packet having the smallest sequence number among the data packets not successfully received by the first network device.

[0084] In relation to the implementation of the fifth option of the eighth aspect, in the implementation of the sixth option of the eighth aspect, the N compressed data packets do not include a compressed data packet received by the first network device.

[0085] In relation to the eighth aspect, the first optional implementation of the eighth aspect, or the sixth optional implementation of the eighth aspect, in a seventh optional implementation of the eighth aspect, the method further includes a step of receiving capability information from the terminal device, wherein the capability information indicates that the terminal device supports continuing to use the first buffer.

[0086] In relation to the eighth aspect, the first optional implementation of the eighth aspect, or the sixth optional implementation of the seventh aspect, in an eighth optional implementation of the eighth aspect, the first buffer corresponds to a first radio bearer, and the first radio bearer includes some or all of the radio bearers of the terminal device.

[0087] For technical effects provided by the eighth aspect or optional implementations, please refer to the description of the technical effects of the first aspect or corresponding implementations, and / or refer to the description of the technical effects of the second aspect or corresponding implementations, and / or refer to the description of the technical effects of the third aspect or corresponding implementations.

[0088] The method according to the seventh and / or eighth aspects relates to an uplink compression process.

[0089] According to a ninth aspect, a ninth communication method is provided. The method may be performed by a first network device, or may be performed by a chip system or another functional module. The chip system or functional module may implement functions of the first network device. For example, the first network device is an access network device, such as a base station. The method includes: sending a handover command to a terminal device, the handover command including first indication information and second indication information, the first indication information indicating to reestablish a PDCP layer or perform a cell handover, the second indication information indicating to continue using a third buffer, and the third buffer being used by the terminal device to decompress data packets compressed based on the first buffer or the second buffer; and reestablishing the PDCP layer without resetting the first buffer, the first buffer being used by the first network device to decompress the data packets.

[0090] In relation to the ninth aspect, in a first optional implementation of the ninth aspect, the method further includes a step of transmitting indication information to a second network device, wherein the indication information indicates the contents of a first buffer, the contents of the first buffer are used to update a second buffer, and the second buffer is used by the second network device to compress data packets, and the first network device is a network device accessed by the terminal device before the terminal device performs a cell handover, and the second network device is a network device accessed by the terminal device after the terminal device performs a cell handover.

[0091] In relation to the implementation of the ninth aspect or the first optional implementation of the ninth aspect, in a second optional implementation of the ninth aspect, the method further includes the steps of: sending a first message to a second network device, wherein the first message is used to inquire whether the terminal device is supported to continue using the third buffer, the first network device being a network device accessed by the terminal device before the terminal device performs a cell handover, and the second network device being a network device accessed by the terminal device after the terminal device performs a cell handover; and receiving a second message from the second network device, wherein the second message indicates that the terminal device is supported to continue using the third buffer.

[0092] In relation to the ninth aspect, in a third optional implementation of the ninth aspect, the method further includes a step of receiving a status report from the terminal device, the status report indicating compressed data packets received by the terminal device.

[0093] In relation to the third optional implementation of the ninth aspect, in a fourth optional implementation of the ninth aspect, the method further includes a step of transmitting N compressed data packets to the terminal device in ascending order of sequence numbers of the compressed data packets, starting from a first compressed data packet that is not determined to be received successfully, where N is a positive integer.

[0094] In relation to the implementation of the fourth option of the ninth aspect, in the implementation of the fifth option of the ninth aspect, the step of transmitting N compressed data packets to the terminal device in ascending order of sequence numbers of the compressed data packets, starting from the first compressed data packet that is not determined to be received successfully, includes performing integrity protection and encryption processing on the N compressed data packets, and transmitting the processed N compressed data packets to the terminal device.

[0095] In relation to the fourth optional implementation of the ninth aspect or the fifth optional implementation of the ninth aspect, in a sixth optional implementation of the ninth aspect, the data packet having the smallest sequence number among the N compressed data packets is the data packet having the smallest sequence number among the data packets that are not successfully received by the terminal device.

[0096] In relation to the fourth optional implementation of the ninth aspect, the fifth optional implementation of the ninth aspect, or the sixth optional implementation of the ninth aspect, in a seventh optional implementation of the ninth aspect, the N compressed data packets do not include compressed data packets received by the terminal device.

[0097] In relation to the ninth aspect or any one of the first optional implementation of the ninth aspect to the seventh optional implementation of the ninth aspect, in an eighth optional implementation of the ninth aspect, the method further includes a step of receiving capability information from the terminal device, wherein the capability information indicates that the terminal device supports continuing to use the third buffer.

[0098] For technical effects provided by the ninth aspect or optional implementations, please refer to the description of the technical effects of the first aspect or corresponding implementations, and / or refer to the description of the technical effects of the second aspect or corresponding implementations, and / or refer to the description of the technical effects of the third aspect or corresponding implementations.

[0099] A method according to a ninth aspect relates to a downlink compression process.

[0100] According to a tenth aspect, there is provided a communication device. The communication device may be a terminal device according to any one of the first to ninth aspects. The communication device has the functionality of a terminal device. The terminal device is, for example, a base station or a baseband device in a base station. In an optional implementation, the communication device includes a baseband device and a radio frequency device. In another optional implementation, the communication device includes a processing unit (which may also be referred to as a processing module) and a transceiver unit (which may also be referred to as a transceiver module). The transceiver unit can implement a transmitting function and a receiving function. When the transceiver unit implements the transmitting function, the transceiver unit may be referred to as a transmitting unit (which may also be referred to as a transmitting module), and when the transceiver unit implements the receiving function, the transceiver unit may be referred to as a receiving unit (which may also be referred to as a receiving module). The transmitting unit and the receiving unit may be the same functional module. The functional module is referred to as a transceiver unit. The functional module can implement the transmitting function and the receiving function. Alternatively, the transmitting unit and the receiving unit may be different functional modules, and the transceiver unit is a collective term for these functional modules.

[0101] The transceiver unit (or the transmitting unit) is configured to transmit M compressed data packets, where the M compressed data packets are obtained by compressing the M data packets based on the first buffer, and M is a positive integer.

[0102] The processing unit is configured to re-establish the PDCP layer without resetting the first buffer.

[0103] The transceiver unit (or transmitting unit) is further configured to transmit N compressed data packets, where the N compressed data packets are some or all of the M compressed data packets, and N is a positive integer less than or equal to M.

[0104] Alternatively, The transceiver unit (or the receiving unit) is configured to receive K compressed data packets, where the K compressed data packets are obtained by compressing the K data packets based on the first buffer.

[0105] The processing unit is configured to re-establish the PDCP layer without resetting the third buffer.

[0106] The transceiver unit (or the receiving unit) is further configured to receive N compressed data packets, where the N compressed data packets are obtained by compressing the N data packets based on the second buffer, and both K and N are positive integers.

[0107] The processing unit is further configured to decompress the K compressed data packets and the N compressed data packets based on the third buffer, or decompress the N compressed data packets based on the third buffer.

[0108] Alternatively, The transceiver unit (or the receiving unit) is configured to receive a handover command, the handover command including first indication information and second indication information, the first indication information indicating to re-establish a PDCP layer or perform a cell handover, the second indication information indicating to the terminal device to continue using the first buffer, the first buffer being used by the terminal device to compress data packets.

[0109] The processing unit is configured to re-establish the PDCP layer without resetting the first buffer.

[0110] In an optional implementation, the communication device further includes a storage unit, and the processing unit is configured to couple to the storage unit and execute programs or instructions in the storage unit to enable the communication device to perform functions of a terminal device according to any one of the first to ninth aspects.

[0111] According to an eleventh aspect, there is provided a communication device. The communication device may be the first network device according to any one of the first to ninth aspects. The communication device has the functionality of the first network device. The first network device is, for example, a base station or a baseband device in a base station. In an optional implementation, the communication device includes a baseband device and a radio frequency device. In another optional implementation, the communication device includes a processing unit (which may also be referred to as a processing module) and a transceiver unit (which may also be referred to as a transceiver module). For implementation of the transceiver unit, please refer to the description of the fourth aspect.

[0112] The transceiver unit (or receiving unit) is configured to receive K compressed data packets from the terminal device, where the K compressed data packets are obtained by compressing the K data packets based on the first buffer, and K is a positive integer.

[0113] The processing unit is configured to re-establish the PDCP layer without resetting the second buffer, the second buffer being used by the first network device to decompress data packets compressed based on the first buffer.

[0114] Alternatively, The transceiver unit (or receiving unit) is configured to receive K compressed data packets from a first network device, where the K compressed data packets are obtained by compressing the K data packets based on the first buffer, the second network device is a network device accessed by the terminal device after the terminal device performs a cell handover, and the first network device is a network device accessed by the terminal device before the terminal device performs a cell handover.

[0115] The transceiver unit (or receiving unit) is configured to receive indication information from the first network device, the indication information indicating the contents of the second buffer, and the second buffer is used by the first network device to decompress the compressed data packet based on the first buffer.

[0116] The processing unit is configured to update a third buffer based on the contents of the second buffer, and the third buffer is used by the second network device to decompress data packets compressed based on the first buffer.

[0117] Alternatively, The transceiver unit (or the transmitting unit) is configured to transmit M compressed data packets to the terminal device, where the M compressed data packets are obtained by compressing the M data packets based on the first buffer, and M is a positive integer.

[0118] The processing unit is configured to re-establish the PDCP layer without resetting the first buffer.

[0119] Alternatively, The transceiver unit (or receiving unit) is configured to receive indication information from a first network device, the indication information indicating the contents of a first buffer, the first buffer being used by the first network device to compress data packets, the second network device being a network device accessed by the terminal device after the terminal device performs a cell handover, and the first network device being a network device accessed by the terminal device before the terminal device performs a cell handover.

[0120] The processing unit is configured to update a second buffer based on the contents of the first buffer, the second buffer being used by a second network device to compress data packets.

[0121] Alternatively, The transceiver unit (or the transmitting unit) is configured to send a handover command to the terminal device, the handover command including first indication information and second indication information, the first indication information indicating to re-establish a PDCP layer or perform a cell handover, and the second indication information indicating to continue using a first buffer, the first buffer being used by the terminal device to compress data packets.

[0122] The processing unit is configured to re-establish the PDCP layer without resetting the second buffer, the second buffer being used by the first network device to decompress data packets compressed based on the first buffer.

[0123] Alternatively, The transceiver unit (or the transmitting unit) is configured to send a handover command to the terminal device, the handover command including first indication information and second indication information, the first indication information indicating to re-establish a PDCP layer or perform a cell handover, and the second indication information indicating to continue using a third buffer, the third buffer being used by the terminal device to decompress data packets compressed based on the first buffer or the second buffer.

[0124] The processing unit is configured to re-establish the PDCP layer without resetting the first buffer, the first buffer being used by the first network device to compress the data packets.

[0125] In an optional implementation, the communication device further includes a storage unit, and the processing unit is configured to couple to the storage unit and execute programs or instructions in the storage unit to enable the communication device to perform the functions of the first network device or the second network device according to any one of the first to ninth aspects.

[0126] According to a twelfth aspect, there is provided a computer-readable storage medium configured to store computer programs or instructions, which, when executed, perform the method performed by the terminal device, the first network device, or the second network device of the above-mentioned aspect.

[0127] According to a thirteenth aspect, there is provided a computer program product comprising instructions, which when run on a computer, perform the method of the above aspect. [Brief explanation of the drawings]

[0128] [Figure 1]1 is a schematic diagram of a data packet compression and decompression process in an LTE system; [Figure 2] 1 is a schematic diagram of a data packet transmission process between a terminal device and a base station when a cell handover occurs on the terminal device in an LTE system; [Figure 3] 1 is a schematic diagram of an application scenario according to an embodiment of the present application; [Figure 4] 1 is a schematic diagram of an application scenario according to an embodiment of the present application; [Figure 5] 1 is a schematic diagram of UDC technology according to an embodiment of the present application; [Figure 6] FIG. 10 is a schematic diagram of the composition of a count value of a data packet. [Figure 7] 1 is a flow chart of a first communication method according to an embodiment of the present application. [Figure 8] FIG. 2 is a schematic diagram of retransmitting some compressed data packets by a terminal device according to an embodiment of the present application; [Figure 9] FIG. 2 is a schematic diagram of compressing data packets by a terminal device according to an embodiment of the present application; [Figure 10] 4 is a flow chart of a second communication method according to an embodiment of the present application. [Figure 11] 10 is a flow chart of a third communication method according to an embodiment of the present application. [Figure 12] 10 is a flow chart of a fourth communication method according to an embodiment of the present application. [Figure 13] 1 is a schematic block diagram of a communication device according to an embodiment of the present application; [Figure 14] FIG. 1 is a schematic block diagram of a terminal device according to an embodiment of the present application; [Figure 15] 1 is a schematic block diagram of a network device according to an embodiment of the present application; DETAILED DESCRIPTION OF THE INVENTION

[0129] In order to make the objectives, technical solutions and advantages of the embodiments of the present application clearer, the following further describes the embodiments of the present application in detail with reference to the accompanying drawings.

[0130] In an embodiment of the present application, the terminal device is a device having wireless transceiver functionality, and may be a fixed device, a mobile device, a handheld device (e.g., a mobile phone), a wearable device, an in-vehicle device, or a wireless device (e.g., a communication module, a modem, or a circuit system) built into the above-mentioned devices. Terminal devices are configured to connect people, things, machines, etc., and may be widely used in various scenarios, including but not limited to, the following scenarios: cellular communication, device-to-device (D2D) communication, vehicle-to-everything (V2X), machine-to-machine / machine-type communications (M2M / MTC), internet of things (IoT), virtual reality (VR), augmented reality (AR), industrial control, self driving, remote medical, smart grid, smart furniture, smart office, smart wearable, smart transportation, smart city, unmanned aerial vehicle, and robots. Terminal devices may also be referred to as user equipment (UE), terminal, access station, UE station, remote station, wireless communication device, user equipment, etc.

[0131] The network device in the embodiments of the present application includes, for example, an access network device and / or a core network device. The access network device is a device having wireless transceiver functionality and configured to communicate with terminal devices. The access network device includes, but is not limited to, a base transceiver station (BTS), a NodeB, an evolved NodeB (eNodeB / eNB or gNodeB / gNB), a transmission reception point (TRP) of the above-mentioned communication systems, a base station evolved later from the 3rd generation partnership project (3GPP), an access node, a wireless relay node, a wireless backhaul node, etc. of a wireless fidelity (Wi-Fi) system. The base station may be a macro base station, a micro base station, a picocell base station, a small cell, a relay station, etc. Multiple base stations may support the above-mentioned network using the same access technology or may support the above-mentioned network using different access technologies. The base station may include one or more co-site or non-co-site transmission / reception points. The network device may alternatively be a radio controller, a centralized unit (CU), and / or a distributed unit (DU) in a cloud radio access network (CRAN) scenario. The network device may alternatively be a server, a wearable device, an in-vehicle device, etc. For example, the network device may be a road side unit (RSU) in vehicle-to-everything (V2X) technology. In the following, an explanation is given by using an example in which the access network device is a base station.Multiple network devices in a communication system may be base stations of the same type or different types. A base station may communicate with a terminal device, or may communicate with the terminal device via a relay station. A terminal device may communicate with multiple base stations of different access technologies. A core network device is configured to implement functions such as mobility management, data processing, session management, and policy and charging. The names of devices implementing core network functions in systems of different access technologies may be different. This is not limited in the embodiments of the present application. A 5G system is used as an example. The core network device includes an access and mobility management function (AMF), a session management function (SMF), a user plane function (UPF), etc.

[0132] In the embodiments of the present application, the communication device configured to implement the network device function may be a network device, or may be an apparatus, such as a circuit system, that can support the network device to implement the function. The apparatus may be installed in the network device. In the technical solutions provided in the embodiments of the present application, the technical solutions provided in the embodiments of the present application will be described by using an example in which the apparatus configured to implement the network device function is a network device.

[0133] In the embodiments of the present application, unless otherwise specified, the quantity of nouns refers to "singular or plural nouns," i.e., "one or more." "At least one" means one or more, and "multiple" means two or more. "And / or" describes an association relationship between related objects and indicates that three relationships may exist. For example, A and / or B may represent the following cases: when only A is present, when both A and B are present, and when only B is present, and A and B may be singular or plural. The character " / " generally indicates an "or" relationship between related objects. For example, A / B refers to A or B. At least one of the following items (pieces) or similar expressions refers to any combination of these items, including any combination of singular items (pieces) or multiple items (pieces). For example, at least one of a, b, or c may refer to a, b, c, a and b, a and c, b and c, or a, b, and c, where a, b, and c may be singular or plural.

[0134] In the embodiments of the present application, ordinals such as "first" and "second" are used to distinguish between multiple objects and are not used to limit the size, content, order, time sequence, application scenario, priority, or importance of the multiple objects. For example, the first buffer and the second buffer may be the same buffer or different buffers. Furthermore, such names do not indicate that the content, priority, application scenario, or importance of the two buffers are different.

[0135] Figure 1 shows the data packet compression and decompression process in an LTE system. The top two lines of Figure 1 represent the PDCP and RLC layers on the transmitting side. For example, the buffer size is two data packets. Each dashed box represents the contents of the buffer. Furthermore, dashed boxes containing a " / " represent pre-configured information contained in the buffer. Each data packet is compressed based on the current contents of the buffer. The bottom two lines of Figure 1 represent the PDCP and RLC layers on the receiving side. In AM mode, the RLC layer supports a data retransmission mechanism. Therefore, the transmitting side transmits compressed data packets in order, but the receiving side may receive them out of order. In an LTE system, the receiving side's RLC layer sorts the received compressed data packets and then passes the sorted compressed data packets to the PDCP layer. For example, in FIG. 1, the RLC layer on the receiving side receives compressed data packet 1, compressed data packet 2, compressed data packet 3, and compressed data packet 4 in the following order: compressed data packet 3, compressed data packet 4, compressed data packet 2, and compressed data packet 1. After receiving compressed data packet 1, the RLC layer sorts the four compressed data packets and then passes the four compressed data packets to the PDCP layer in the normal order. After receiving the four compressed data packets, the PDCP layer sequentially decompresses the four compressed data packets by using the UDC protocol stack. Next, the receiving side receives compressed data packet 5, and the RLC layer on the receiving side passes compressed data packet 5 to the PDCP layer, which decompresses compressed data packet 5. Next, the receiving side receives compressed data packet 6, compressed data packet 7, and compressed data packet 8, and the receiving side receives the three compressed data packets in the order of compressed data packet 8, compressed data packet 7, and compressed data packet 6.In this case, after receiving compressed data packet 6, the RLC layer on the receiving side sorts the three compressed data packets and then hands them over to the PDCP layer. After receiving the three compressed data packets, the PDCP layer sequentially decompresses the three compressed data packets by using the UDC protocol stack. For example, the PDCP layer decompresses compressed data packet 1 based on preset information contained in the compression buffer, the PDCP layer decompresses compressed data packet 2 based on preset information contained in the compression buffer and information obtained after compressed data packet 1 is decompressed, the PDCP layer decompresses compressed data packet 3 based on information obtained after compressed data packet 1 is decompressed and information obtained after compressed data packet 2 is decompressed (since the buffer can hold the contents of two data packets, the preset information is considered to be locked out of the buffer), and so on. The sequence number of the data packet (or the sequence number of the compressed data packet) in FIG. 1 is the sequence number (SN) of the PDCP layer, or the sequence number may alternatively be understood as the count value of the PDCP layer of the data packet.

[0136] Generally, the receiver's PDCP layer receives compressed data packets in order to ensure that the receiver's buffer is aligned with the sender's buffer, thereby performing sequential decompression.

[0137] In an LTE system, when a cell handover occurs in a terminal device, the radio link control (RLC) layer of the base station is re-established. If out-of-order compressed data packets or no data packets are received at the RLC layer, the RLC layer no longer waits to receive the unreceived compressed data packets and delivers the received compressed data packets to the PDCP layer. For example, see FIG. 2. When the RLC layer of the base station (receiving side) is re-established, compressed data packets 3, 4, 5, and 7 have been received, but compressed data packets 1, 2, and 6 have not. In this case, the RLC layer delivers compressed data packets 3, 4, 5, and 7 to the PDCP layer. Compressed data packet 0 is received by the RLC and successfully decompressed, and data packet 0 obtained by decompressing compressed data packet 1 is delivered to the PDCP layer. After receiving compressed data packets 3, 4, 5, and 7, the PDCP layer decompresses these compressed data packets. When decompressing compressed data packet 3, the PDCP layer needs to update the buffer based on the decompression result of compressed data packet 2 so that compressed data packet 3 can be successfully decompressed. However, because the PDCP layer does not receive compressed data packet 2, it fails to decompress compressed data packet 3. Similarly, the PDCP layer also fails to decompress compressed data packets 4, 5, and 7. In this case, the PDCP layer discards compressed data packets 3, 4, 5, and 7. Furthermore, after receiving the compressed data packets, the RLC layer of the base station sends hybrid automatic repeat request (HARQ)-acknowledgement (ACK) information to the terminal device. For the received compressed data packets, the RLC layer of the base station sends an acknowledgment (ACK) to the terminal device.For example, if the RLC layer has not received compressed data packet 1 when re-established, the RLC layer will not send an ACK for compressed data packet 1 to the terminal device.

[0138] After completing the cell handover, the terminal device (transmitter) may retransmit the compressed data packets to the base station. For example, the terminal device sequentially retransmits the compressed data packets starting from the first compressed data packet for which no ACK is received. For example, if the terminal device receives ACKs for compressed data packets 3, 4, 5, and 7 but not for compressed data packets 1, 2, and 6, the terminal device retransmits compressed data packets 1 through 7. In the cell handover process, the terminal device reestablishes the PDCP layer and resets buffers corresponding to the UDCs of the terminal device, the UDC protocol stack, and the like. In this case, the terminal device recompresses the data packets based on the reset buffers. Compressed data packets 1 through 7, which were previously transmitted by the terminal device to the base station, are obtained by compressing the corresponding data packets based on the buffers before resetting. The terminal device then recompresses these data packets based on the reset buffers to obtain compressed data packets 1 through 7. Then, the terminal device transmits the compressed data packets to the base station. It can be seen that the terminal device needs to perform compression twice on the same data packet, but the multiple compression processes will significantly increase the processing time of the terminal device, and the processing efficiency of the terminal device will be significantly reduced, especially when there are a large number of data packets.

[0139] Currently, UDC technology exists only in LTE systems and has not been introduced in new radio (NR) systems. It is not currently determined whether UDC technology can be used in NR systems.

[0140] An embodiment of the present application provides a communication method. According to the method provided in this embodiment of the present application, a buffer-based data compression technology (e.g., UDC technology) can be applied to an NR system. In addition, in this embodiment of the present application, when re-establishing the PDCP layer, the terminal device does not reset the first buffer. In this case, when the terminal device needs to retransmit a data packet, the terminal device may retransmit the previously obtained compressed data packet, and there is no need to re-compress the data packet. This reduces the number of times the data packet is compressed, reduces the processing time of the terminal device, and improves processing efficiency. Furthermore, since the workload of the terminal device is reduced, the power consumption of the terminal device is reduced. When the terminal device acts as a data receiver, the terminal device may process data normally without resetting the buffer. This reduces the workload of the terminal device and reduces the power consumption of the terminal device.

[0141] The technical solutions provided in this embodiment of the present application may be applied to an LTE system, for example, a normal LTE system, or an internet of vehicles such as vehicle to everything (V2X) or LTE-V, or may be applied to an NR system, for example, a normal NR system, or an internet of vehicles such as V2X or NR-V, or another similar communication system or next-generation communication system.

[0142] 3 illustrates an application scenario according to an embodiment of the present application. FIG. 3 includes one network device and one terminal device. For example, the network device operates in an evolved Universal Mobile Telecommunications System terrestrial radio access (E-UTRA) system or an NR system. For example, the terminal device accesses the network device before and after performing cell handover.

[0143] 4 illustrates another application scenario according to an embodiment of the present application. Figure 4 includes two network devices and one terminal device. For example, network device 1 is a network device accessed by the terminal device before the terminal device performs cell handover, and network device 2 is a network device accessed by the terminal device after the terminal device performs cell handover. For example, network device 1 or network device 2 works in an evolved Universal Mobile Telecommunications System (UMTS) terrestrial radio access (E-UTRA) system or an NR system, and the systems in which network device 1 and network device 2 work may be the same or different.

[0144] The network device in FIG. 3 or FIG. 4 is, for example, a base station. The network device corresponds to different devices in different systems. For example, the network device may correspond to an eNB in ​​a 4G system and a 5G network device such as a gNB in ​​a 5G system. In a 5G system, the network device may be a device on a hybrid network composed of an LTE network device and an NR network device, and the network device and the terminal device form mixed radio-dual connectivity (MR-DC). Indeed, the technical solutions provided in this embodiment of the present application may also be applied to future mobile communication systems. Therefore, the network device in FIG. 3 or FIG. 4 may correspond to a network device of a future mobile communication system. FIGS. 3 and 4 show an example in which the network device is a base station. In fact, referring to the above description, the network device may alternatively be a device such as an RSU.

[0145] A practical application scenario of this embodiment of the present application will be considered. When a user holds a terminal device and needs to perform an operation such as a VoLTE / voice over new radio (VoNR) call or data Internet access (e.g., start a live broadcast, play a game, or surf the Internet), the user needs to access a network. At the initial stage of accessing a network, the terminal device usually needs to report to a base station whether the terminal device has the ability to support data compression. When determining that the terminal device has the ability to support data compression, the base station can determine whether to configure data compression-related parameters for the terminal device (e.g., configure a UDC function and a corresponding bearer to support an active state) based on the service initiated by the user. When the base station configures that the terminal device can perform data compression, for example, can perform UDC, the terminal device may use the UDC method in uplink transmission, for example, in the process of starting a VoLTE / VoNR call, starting a live broadcast, or playing a real-time game. In this case, the terminal device may perform UDC by using the method provided in this embodiment of the present application. This can reduce or even avoid packet loss caused by compressing uplink data, and can reduce power consumption caused by repeated compression. Similarly, the method provided in this embodiment of the present application may also be used to compress downlink data, to reduce or even avoid packet loss caused by compressing downlink data.

[0146] Furthermore, this embodiment of the present application is not limited to communication between a network device and a terminal device, but may include communication between network devices or communication between terminal devices.

[0147] The technical solutions provided in this embodiment of the present application are described in detail below with reference to the accompanying drawings. Please note that in the accompanying drawings corresponding to the embodiments of the present application, all steps represented by dashed lines are optional steps. Furthermore, in the embodiments of the present application, an NR system is used as an example.

[0148] Before the embodiments of the present application are described, the UDC technology in the embodiments of the present application will be described first.

[0149] In UDC, a terminal device functions as a sender that compresses data packets, and a network device functions as a receiver that decompresses the data packets. Both compression and decompression are performed based on the same buffer status maintained by the sender and receiver. The buffer status may refer to the contents (or information) contained in the buffer. When compressing a data packet, the sender compresses the data packet based on the current status of the buffer. After successful compression, the sender updates the buffer by inserting the original information of the current compressed data packet before compression from the end of the buffer. When the first data packet is compressed, the buffer may not contain information about the previous data packet. In this case, the sender may perform compression based on preset information, such as a predefined dictionary. For example, as shown in FIG. 5, the buffer contains "abc," and "abc" is, for example, a predefined dictionary. When the sender needs to compress the data packet "def", it may perform compression based on "abc" to obtain compressed data packet 1 after compressing the data packet "def", and the sender may put "def" into the buffer from the end of the buffer. Next, when the sender needs to compress the data packet "ghijkl", it may perform compression based on "abcdef" in buffer. In other words, compression is performed based on all the contents in the buffer each time. After compressing the data packet "ghijkl" and obtaining compressed data packet 2, the sender may put the data packet "ghijkl" into the buffer from the end of the buffer. Because the storage space of the buffer is limited, "abcd" is locked out of the buffer according to the first in first out (FIFO) principle. In this case, when the sender needs to compress another data packet, compression is performed based on "efghijkl" contained in the buffer.After receiving compressed data packet 1, the receiver may decompress compressed data packet 1 based on the predefined dictionary "abc" in the buffer to obtain data packet "def" and put the data packet "def" into the buffer from the end of the buffer. After receiving compressed data packet 2, the receiver may decompress compressed data packet 2 based on the information "abcdef" in the buffer to obtain data packet "ghijkl" and put the data packet "ghijkl" into the buffer from the end of the buffer. In this case, "abcd" is locked out of the buffer. It can be seen that the buffer status of the receiver continues to match the buffer status of the sender, which can ensure that the receiver can perform decompression correctly.

[0150] In an embodiment of the present application, a data packet before compression (hereinafter also referred to as a data packet) and a corresponding compressed data packet may have the same sequence number. For example, a first compressed data packet may be obtained by compressing a first data packet, and the sequence number of the first compressed data packet is the same as the sequence number of the first data packet. A second compressed data packet may be obtained by compressing a second data packet, and the sequence number of the second compressed data packet is the same as the sequence number of the second data packet. Furthermore, the technical solutions provided in the embodiments of the present application may be applied to the transmission of a data radio bearer (DRB) in UM / AM, may be applied to the transmission of a signaling radio bearer (SRB), or may be applied to the transmission of a quality of service flow (QoS flow) on a DRB.

[0151] In transmission over the air interface, each data packet has a number corresponding to the PDCP layer. The data packet number in the PDCP layer may include two parts: a sequence number (SN) and a hyperframe number (HFN). The combination of the two parts forms the data packet number, in other words, the data packet count value. Figure 6 is a schematic diagram of the components of the data packet count value. The data packet sequence number in this embodiment of the present application may be the data packet sequence number or the data packet count value.

[0152] An embodiment of the present application provides a first communication method. Figure 7 is a flowchart of the method. In the process of the following description, an example is used in which the method is applied to the network architecture shown in Figure 3. The terminal device described below is, for example, the terminal device in the network architecture shown in Figure 3, and the first network device described below is, for example, the network device in the network architecture shown in Figure 3.

[0153] S701: A terminal device sends capability information to a first network device, and in response, the first network device receives capability information from the terminal device.

[0154] For example, the terminal device may transmit capability information to the first network device in a random access process, or the terminal device may transmit the capability information to the first network device after successful random access. The capability information may indicate the capability of the terminal device. For example, the capability information indicates that the terminal device may support UDC. As another example, the capability information may indicate that continuing to use the first buffer is supported, which indicates that the terminal device supports a function of continuing to use the first buffer (the function may also be referred to as buffer continue), or the capability information may indicate that continuing to use the first buffer is not supported. Buffer continue may be understood as not resetting a buffer corresponding to a data compression / decompression function when a PDCP layer is re-established. Thus, the capability information may indicate that not resetting the first buffer when a PDCP layer is re-established is supported, or may indicate that not resetting the first buffer when a PDCP layer is re-established is not supported. Optionally, further, the capability information may further indicate the capability of the terminal device in another aspect, for example, may indicate the number of antennas supported by the terminal device. This is not limited to the first buffer, which is maintained by the terminal device and used to compress the data packet. In other words, the terminal device may compress the data packet based on the first buffer.

[0155] The first network device may determine, based on the capability information, whether the terminal device supports continuing to use the first buffer. If the terminal device supports continuing to use the first buffer, the first network device may indicate to the terminal device to continue to use the first buffer. If the terminal device does not support continuing to use the first buffer, the first network device may not indicate to the terminal device to continue to use the first buffer, or may indicate to the terminal device to reset the first buffer. Alternatively, the terminal device may not send the capability information. The first network device may determine, based on another factor, whether to indicate to the terminal device to continue to use the first buffer, or whether the terminal device continues to use the first buffer may be specified in a protocol. Therefore, S701 is an optional step.

[0156] S702: A terminal device transmits M compressed data packets to a first network device, and in response, the first network device receives K compressed data packets from the terminal device, where M is a positive integer and K is a positive integer less than or equal to M. The K compressed data packets may be some or all of the M compressed data packets, or the K compressed data packets are a subset of the M compressed data packets.

[0157] The reason why the first network device receives K compressed data packets instead of M compressed data packets is because packet loss is taken into consideration. For example, M K compressed data packets may be lost in the transmission process and not be correctly received by the first network device. The sequence numbers of the K compressed data packets may be consecutive or discontinuous. Optionally, the sequence numbers of the K compressed data packets and the sequence numbers of the data packets successfully decompressed by the first network device are discontinuous. For example, the M compressed data packets are compressed data packet 1 to compressed data packet 7, and the K compressed data packets are compressed data packets 3, 4, 5, and 7. In this case, the sequence numbers of the K compressed data packets are discontinuous. Furthermore, the compressed data packet with the highest sequence number successfully decompressed by the first network device is compressed data packet 0. In this case, the sequence numbers of the K compressed data packets and the sequence number of the last data packet successfully decompressed by the first network device and handed over to an upper layer are both discontinuous. As another example, the M compressed data packets are compressed data packet 1 to compressed data packet 7, and the K compressed data packets are compressed data packets 3, 4, 5, and 6. In this case, the sequence numbers of the K compressed data packets are consecutive. Furthermore, the compressed data packet with the largest sequence number successfully decompressed by the first network device is compressed data packet 0. In this case, the sequence numbers of the K compressed data packets and the sequence number of the data packet successfully decompressed by the first network device are discontinuous.

[0158] The M compressed data packets are obtained by the terminal device by compressing the M data packets based on the first buffer, where there is a one-to-one correspondence between the compressed data packets and the data packets. The first buffer is a buffer used by the terminal device to compress the data packets. For example, the terminal device may compress the data packets based on the first buffer by using UDC technology. For example, the first buffer corresponds to a first radio bearer. The first radio bearer may include all or a part of a radio bearer of the terminal device. The radio bearer is, for example, a DRB or an SRB. Alternatively, for example, the first buffer corresponds to one or more QoS flows within the DRB.

[0159] For example, before transmitting M compressed data packets, the terminal device did not transmit any compressed data packets to the first network device. In this case, before the terminal device compresses the M compressed data packets, the first buffer includes, for example, a predefined dictionary, i.e., the first buffer is filled with the predefined dictionary. The terminal device compresses data packet 1 among the M data packets based on the predefined dictionary to obtain compressed data packet 1. Then, the terminal device updates the first buffer based on the contents of data packet 1, and compresses data packet 2 among the M data packets based on the updated first buffer to obtain compressed data packet 2, and so on until M compressed data packets are obtained. See FIG. 5 for an example of this process.

[0160] The first network device may send feedback information about the K compressed data packets to the terminal device to indicate that the first network device has received the K compressed data packets. For example, each time the RLC layer of the first network device receives one compressed data packet, the first network device may send an ACK for the compressed data packet to the terminal device. In this case, the first network device may send a total of K ACKs to the terminal device, where the K ACKs correspond to the K compressed data packets. After receiving the K ACKs, the terminal device may know that the first network device will receive K compressed data packets.

[0161] Optionally, the PDCP layer of the first network device may further send a status report to the terminal device. The status report may indicate compressed data packets received by the first network device. For this embodiment of the present application, the status report may indicate K compressed data packets. After receiving the status report, the terminal device may know that the first network device will receive K compressed data packets. For example, the status report may be implemented by using a bitmap. The amount of bits included in the bitmap may be M, and the M bits correspond one-to-one to the M compressed data packets. If the first network device receives a compressed data packet, the bit corresponding to the compressed data packet is set to "1." If the first network device does not receive a compressed data packet, the bit corresponding to the compressed data packet is set to "0." In this way, the terminal device can quickly determine which compressed data packets are received by the first network device. As another example, the status report may include sequence numbers of compressed data packets received by the first network device and / or sequence numbers of compressed data packets not received by the first network device. In this way, the terminal device can determine which compressed data packets are received by the first network device.

[0162] It should be noted that the terminal device may perform corresponding processing on the compressed data packet before transmitting the compressed data packet. For example, the terminal device performs integrity protection and encryption processing on the compressed data packet (e.g., performs corresponding processing in the PDCP layer) and delivers the processed compressed data packet to the lowest layer of the terminal device (e.g., the RLC layer, the media access control (MAC) layer, or the physical layer). Then, the lowest layer of the terminal device transmits the processed compressed data packet. The terminal device may transmit M compressed data packets in a similar manner, and the terminal device may transmit N compressed data packets described below in a similar manner. The details will not be described again.

[0163] S703: The first network device sends a handover command to the terminal device, and in response, the terminal device receives a handover command from the first network device.

[0164] For example, the handover command may include first indication information, which may indicate reestablishing a PDCP layer or performing a cell handover. Optionally, the handover command may further include second indication information. The second indication information may indicate continuing to use the first buffer, or may indicate not resetting the first buffer when the PDCP layer is reestablished. In this case, if the handover command includes the second indication information, the terminal device may continue to use the first buffer when reestablishing the PDCP layer, or if the handover command does not include the second indication information, the terminal device does not continue to use the first buffer when reestablishing the PDCP layer. For example, when reestablishing the PDCP layer, the terminal device resets the first buffer. Alternatively, in this case, the second indication information indicates whether to reset the first buffer when the PDCP layer is reestablished. Alternatively, in this case, the value of the second indication information indicates whether the first buffer should be reset when the PDCP layer is re-established.

[0165] Alternatively, the second indication information may not be included in the handover command, and the first network device may send the second indication information to the terminal device by using a separate message. In this case, the first network device may send the second indication information to the terminal device before S703, or may send the second indication information to the terminal device after S703, or the first network device may send the handover command and the second indication information to the terminal device simultaneously. In this case, if the terminal device receives the second indication information, the terminal device may continue to use the first buffer when re-establishing the PDCP layer, or if the terminal device does not receive the second indication information, the terminal device does not continue to use the first buffer when re-establishing the PDCP layer. For example, the terminal device may reset the first buffer when re-establishing the PDCP layer.

[0166] If the first network device transmits the second indication information, the first network device supports continuing to use the second buffer. The second buffer corresponds to the first buffer and is maintained by the first network device. For example, the first network device may decompress the compressed data packet obtained based on the first buffer (or the data packet compressed based on the first buffer) based on the second buffer. If the first network device does not transmit the second indication information, the first network device may support continuing to use the second buffer or may not support continuing to use the second buffer. Regardless of whether the first network device supports continuing to use the second buffer, since the first network device does not transmit the second indication information, the first network device does not continue to use the second buffer and resets the second buffer when re-establishing the PDCP layer to remain consistent with the behavior of the terminal device.

[0167] Alternatively, for example, if the protocol specifies that the first buffer continues to be used or that the first buffer is not reset when the PDCP layer is re-established, the first network device may not need to send the second indication information. In this case, the network device may determine, in accordance with the protocol, to continue to use the second buffer when re-establishing the PDCP layer, and the terminal device may determine, in accordance with the protocol, to continue to use the first buffer when re-establishing the PDCP layer.

[0168] Except when a cell handover is performed, the terminal device may re-establish the PDCP layer in other cases. Therefore, S703 is an optional step.

[0169] S704: The terminal device re-establishes the PDCP layer without resetting the first buffer.

[0170] When performing a cell handover, the terminal device may re-establish the PDCP layer. Alternatively, the terminal device may re-establish the PDCP layer when triggered by another event other than a cell handover. Therefore, S703 is an optional step.

[0171] If the terminal device receives the second indication or if the protocol specifies that the first buffer continues to be used, the terminal device may not reset the first buffer when re-establishing the PDCP layer. However, if the terminal device does not receive the second indication or if the protocol does not specify that the first buffer continues to be used, the terminal device may reset the first buffer when re-establishing the PDCP layer. Resetting the first buffer by the terminal device may include, for example, clearing the contents of the first buffer and adding a predefined dictionary to the cleared first buffer. In an embodiment of the present application, the contents of the predefined dictionary are associated with, for example, a service. When the services performed by the device are different, the predefined dictionary may be the same or different. Alternatively, the contents of the predefined dictionary may be associated with another factor. This is not particularly limited, and details will not be described again below. In this embodiment of the present application, an example is used in which the terminal device does not reset the first buffer when re-establishing the PDCP layer.

[0172] S705: The first network device re-establishes the PDCP layer without resetting the second buffer.

[0173] When the terminal device performs a cell handover, the first network device also re-establishes the PDCP layer. In this embodiment of the present application, the terminal device accesses the first network device before and after performing the cell handover. For example, the terminal device is handed over from a first cell provided by the first network device to a second cell provided by the first network device. If the first network device determines to continue using the second buffer, the first network device does not reset the second buffer when re-establishing the PDCP layer. However, if the first network device determines not to continue using the second buffer, the first network device may reset the second buffer when re-establishing the PDCP layer. Resetting the second buffer by the first network device may include, for example, clearing the contents of the second buffer and adding a predefined dictionary to the cleared second buffer. For the first network device and the terminal device, the buffer status needs to remain consistent, so the predefined dictionary used to reset the first buffer and the predefined dictionary used to reset the second buffer may be the same. In this embodiment of the present application, an example is used in which the first network device does not reset the second buffer when re-establishing the PDCP layer.

[0174] S704 may be performed before S705, after S705, or simultaneously with S705.

[0175] S706: The terminal device transmits N compressed data packets to the first network device, and in response, the first network device receives N compressed data packets from the terminal device. The N compressed data packets are part or all of the M compressed data packets. For example, N is an integer equal to or less than M.

[0176] After completing the cell handover or re-establishing the PDCP layer, if the terminal device is not handed over between network devices, the terminal device may retransmit N compressed data packets to the first network device. The terminal device transmits N compressed data packets in ascending order of compressed data packet sequence numbers, starting from the first compressed data packet determined not to be successfully received by the first network device. For example, the first compressed data packet among the N compressed data packets (or the compressed data packet with the smallest sequence number among the N compressed data packets) may be the first compressed data packet not successfully received by the first network device (or the compressed data packet with the smallest sequence number among the data packets not successfully received by the first network device). For example, the M compressed data packets are compressed data packet 1 to compressed data packet 7, the K compressed data packets are compressed data packets 3, 4, 5, and 7, and the N compressed data packets are compressed data packet 1 to compressed data packet 7. In this case, the first compressed data packet among the N compressed data packets is compressed data packet 1. Compressed data packet 1 is the first compressed data packet that is not successfully received by the first network device.

[0177] In the above example, N=M, which is equivalent to the terminal device retransmitting M compressed data packets. In this way, the success rate of the first network device acquiring the compressed data packets can be improved. Optionally, when the first network device sends a status report to the terminal device and the status report indicates the compressed data packets received by the first network device, the terminal device no longer needs to transmit the compressed data packets received by the first network device and only needs to transmit the compressed data packets not received by the first network device. In this case, the N compressed data packets may not include the compressed data packets received by the first network device. For example, the M compressed data packets are compressed data packet 1 to compressed data packet 7, and the K compressed data packets are compressed data packets 3, 4, 5, and 7, and the status report sent by the first network device to the terminal device indicates the K compressed data packets. In this case, the N compressed data packets transmitted by the terminal device are, for example, compressed data packets 1, 2, and 6, and the terminal device no longer needs to transmit compressed data packets 3, 4, 5, and 7. In this way, the amount of data retransmitted by the terminal device can be reduced, and the transmission overhead can be reduced.

[0178] See Figure 8. The M compressed data packets transmitted by the PDCP layer of the terminal device are, for example, compressed data packet 1 to compressed data packet 7. The PDCP layer of the first network device receives compressed data packets 3, 4, 5, and 7, but does not receive compressed data packets 1, 2, and 6. In addition, the PDCP layer of the terminal device further transmits compressed data packet 0 to the first network device before transmitting the M compressed data packets. The PDCP layer of the first network device receives compressed data packet 0 and successfully decompresses it to obtain data packet 0. In this case, the PDCP layer of the first network device passes data packet 0 to an upper layer above the PDCP layer, for example, a service data adaptation protocol (SDAP) layer. The PDCP layer of the first network device transmits a status report to the PDCP layer of the terminal device. The status report indicates that the first network device has received compressed data packets 3, 4, 5, and 7. For example, the status report is implemented by using a bitmap. The bitmap may include 7 bits. For example, the bitmap may be 1011100, which corresponds to compressed data packet 1 to compressed data packet 7, from least significant bit to most significant bit. The first network device receives compressed data packets 3, 4, 5, and 7. In this case, the bit values ​​corresponding to these compressed data packets are "1." The first network device does not receive compressed data packets 1, 2, and 6. In this case, the bit values ​​corresponding to these compressed data packets are "0." After the terminal device receives the status report, the PDCP layer of the terminal device retransmits compressed data packets 1, 2, and 6 to the first network device, and does not need to retransmit compressed data packets 3, 4, 5, and 7, in order to save uplink transmission resources.

[0179] FIG. 9 illustrates a process in which a terminal device compresses data packets 1 to 7. Numbers 1 to 7 in the first row of FIG. 9 represent seven PDCP service data units (SDUs), i.e., seven data packets. In other words, numbers 1 to 7 in the first row represent seven data packets to be compressed. The second row illustrates compressed data packets 1 to 7 obtained after the terminal device compresses data packets 1 to 7 based on a first buffer. The third row illustrates encrypted data packets 1 to 7 obtained after compressed data packets 1 to 7 in the second row are encrypted with a first encryption method. The terminal device may transmit the seven encrypted data packets to a first network device. This process may be considered as the terminal device transmitting M compressed data packets to the first network device. For example, M=7, and seven encrypted data packets are obtained by encrypting M compressed data packets with a first encryption method, where the first encryption method corresponds to the first cell accessed by the terminal device before the terminal device performs cell handover. The fourth row shows encrypted data packets 1 to 7 obtained after compressed data packets 1 to 7 in the second row are encrypted with a second encryption method. The terminal device may transmit the seven encrypted data packets to the first network device. This process may be considered as the terminal device transmitting N compressed data packets to the first network device. For example, N=7, and seven encrypted data packets are obtained by encrypting N compressed data packets with a second encryption method, where the second encryption method corresponds to the second cell accessed by the terminal device after the terminal device performs cell handover. It can be seen from FIG. 9 that the terminal device performs the compression process for these data packets only once.If the compressed data packet needs to be retransmitted, the obtained compressed data packet only needs to be encrypted based on the corresponding encryption method after the cell handover, and the data packet does not need to be compressed again, which reduces the compression process of the terminal device and correspondingly improves the processing efficiency of the terminal device.

[0180] With respect to the first network device, if the first network device does not send a status report to the terminal device after receiving the K compressed data packets, the first network device may decompress the K compressed data packets. Because the sequence numbers of the K compressed data packets and the sequence numbers of the data packets successfully decompressed by the first network device are discontinuous, the first network device may fail to decompress the K compressed data packets, and the first network device may discard the K compressed data packets that fail to be decompressed. The terminal device further transmits N compressed data packets to the first network device. Because the terminal device does not receive the status report, the compressed data packet with the smallest sequence number among the N compressed data packets is the compressed data packet with the smallest sequence number among the compressed data packets not successfully received by the first network device, and the sequence numbers of the N data packets are consecutive. For example, the M compressed data packets are compressed data packet 1 to compressed data packet 7, the K compressed data packets are compressed data packets 3, 4, 5, and 7, and the N compressed data packets are compressed data packet 1 to compressed data packet 7. In this way, even if the first network device discards the K compressed data packets, the first network device can still obtain the K compressed data packets because the terminal device retransmits the N compressed data packets and the N compressed data packets include the K compressed data packets. The above example continues to be used. The first network device obtains compressed data packets 1 to 7, and because the first network device previously performed correct decompression on compressed data packet 0, the status of the second buffer is determined based on data packet 0.In this case, the first network device can correctly decompress compressed data packet 1 through compressed data packet 7 based on the second buffer not being reset.

[0181] Alternatively, if the first network device does not send a status report to the terminal device after receiving the K compressed data packets, the first network device may not decompress the K compressed data packets and wait for the N compressed data packets from the terminal device. The PDCP layer may have a deduplication function. For example, if the first network device receives compressed data packet 3 and does not discard compressed data packet 3, and the N compressed data packets include compressed data packet 3, after receiving compressed data packet 3 among the N compressed data packets, the first network device discards compressed data packet 3 and continues to store the previously received compressed data packet 3. For example, the M compressed data packets are compressed data packet 1 to compressed data packet 7, the K compressed data packets are compressed data packets 3, 4, 5, and 7, and the N compressed data packets are compressed data packet 1 to compressed data packet 7. In this case, the first network device discards compressed data packets 3, 4, 5, and 7 among the N received compressed data packets. However, because the second buffer is not reset, compressed data packets 3, 4, 5, and 7 stored in the first network device are the same as compressed data packets 3, 4, 5, and 7 discarded by the first network device. Therefore, the first network device can still correctly decompress the K compressed data packets 3, 4, 5, and 7 and compressed data packets 1, 2, and 6 among the N compressed data packets based on the second buffer that is not reset. In this way, the packet loss rate of the first network device can be reduced.

[0182] When the first network device sends a status report to the terminal device after receiving K compressed data packets, the N compressed data packets sent by the terminal device may no longer include K compressed data packets. If the first network device compresses K compressed data packets, and the K compressed data packets are discarded due to decompression failure, and the terminal device no longer sends the K compressed data packets, the first network device may not be able to obtain the K compressed data packets, and the decompression of other compressed data packets performed by the first network device may be affected. Therefore, when the first network device sends a status report to the terminal device after receiving K compressed data packets, the first network device may not decompress the K compressed data packets and wait for N compressed data packets from the terminal device. In addition, because the terminal device does not repeatedly send data packets with the same sequence number, the first network device does not need to use a deduplication function. For example, the M compressed data packets are compressed data packet 1 to compressed data packet 7, the K compressed data packets are compressed data packets 3, 4, 5, and 7, and the N compressed data packets are compressed data packets 1, 2, and 6. The first network device can correctly decompress the K compressed data packets 3, 4, 5, and 7 and the N compressed data packets 1, 2, and 6 based on the second buffer that is not reset.

[0183] S707: The first network device decompresses the N compressed data packets based on the second buffer, or the first network device decompresses the N compressed data packets and the K compressed data packets based on the second buffer.

[0184] For example, it will be understood that if the N compressed data packets include K compressed data packets, the first network device decompresses the N compressed data packets based on the second buffer. For example, the M compressed data packets are compressed data packet 1 to compressed data packet 7, the K compressed data packets are compressed data packets 3, 4, 5, and 7, and the N compressed data packets are compressed data packet 1 to compressed data packet 7. In this case, the first network device decompresses compressed data packet 1 to compressed data packet 7 based on the second buffer.

[0185] As another example, if the N compressed data packets include K compressed data packets, it will be understood that the first network device decompresses the N compressed data packets and the K compressed data packets based on the second buffer. For example, the M compressed data packets are compressed data packet 1 to compressed data packet 7, the K compressed data packets are compressed data packets 3, 4, 5, and 7, and the N compressed data packets are compressed data packets 1, 2, and 6. In this case, the first network device decompresses compressed data packet 1 to compressed data packet 7 based on the second buffer, and compressed data packet 1 to compressed data packet 7 is the union of the K compressed data packets and the N compressed data packets.

[0186] According to the technical solution provided in this embodiment of the present application, the number of compressions performed by the terminal device can be reduced, and the processing efficiency of the terminal device can be improved. When the first network device sends a status report to the terminal device, the amount of data sent by the terminal device can be reduced, and the transmission overhead can be reduced. Furthermore, since neither the first buffer of the terminal device nor the second buffer of the first network device is reset, when the first network device does not send a status report to the terminal device, the first network device can obtain M compressed data packets regardless of whether the first network device decompresses the K compressed data packets after receiving the K compressed data packets. This reduces the amount of packet loss.

[0187] The above describes a case where the terminal device and the first network device do not reset the buffers. If the second indication information received by the terminal device indicates that the first buffer will not continue to be used, or if the protocol specifies that the first buffer will not continue to be used, the terminal device may reset the first buffer when re-establishing the PDCP layer, and the first network device also resets the second buffer. The following briefly describes how the terminal device and the first network device process this case.

[0188] For example, continue to refer to Figure 2. When the PDCP layer of the first network device is re-established, compressed data packets 3, 4, 5, and 7 have been received, but compressed data packets 1, 2, and 6 have not. Compressed data packet 0 is a successfully decompressed compressed data packet received by the PDCP layer, and the PDCP layer decompresses compressed data packet 0 to obtain data packet 0. After the PDCP layer receives compressed data packets 3, 4, 5, and 7, a PDCP re-establishment indication may trigger the decompression of these compressed data packets, and the PDCP layer fails to decompress compressed data packets 3, 4, 5, and 7. In this case, the PDCP layer may discard compressed data packets 3, 4, 5, and 7, or the PDCP re-establishment indication may trigger the PDCP layer to discard out-of-order compressed data packets (there is a special case in which packets from the sender are uncompressed data packets and do not need to be discarded even if they are out-of-order). That is, the PDCP layer does not decompress compressed data packets 3, 4, 5, and 7, and immediately discards them. The solution of immediately discarding out-of-order compressed data packets can reduce the number of decompression operations at the receiving side, improve processing efficiency, save energy consumption, and avoid wasting resources for ineffective decompression processing. Furthermore, after receiving the compressed data packets, the RLC layer of the first network device sends ACK information to the terminal device. For example, for the received compressed data packets, the RLC layer of the first network device sends an ACK to the terminal device. Thereafter, when the first network device sends a PDCP layer feedback report to the terminal device, the feedback report may indicate a data packet that is not received by the first network device or may indicate a data packet that is not successfully decompressed by the first network device.

[0189] After completing the cell handover or re-establishment of the PDCP layer, the terminal device may retransmit the compressed data packets to the first network device. For example, the terminal device sequentially retransmits the compressed data packets starting from the first compressed data packet for which no ACK is received. For example, if the terminal device receives ACKs for compressed data packets 0, 3, 4, 5, and 7 but not for compressed data packets 1, 2, and 6, the terminal device retransmits compressed data packets 1 to 7. During the cell handover process, the terminal device re-establishes the PDCP layer and resets the first buffer. In this case, the terminal device recompresses the data packets based on the reset first buffer. Compressed data packets 1 to 7 previously transmitted by the terminal device to the first network device are obtained by compressing data packets 1 to 7 based on the first buffer before resetting, and the terminal device recompresses data packets 1 to 7 based on the reset first buffer to obtain compressed data packets 1 to 7. The terminal device then transmits the compressed data packet to the first network device, and if the first buffer is not used, it is found that the terminal device needs to perform compression twice on the same data packet.

[0190] In this embodiment of the present application, the first network device may indicate whether to continue using the first buffer, and correspondingly, the first network device may indicate whether to continue using the first buffer based on a specific situation. For example, for a terminal device with low capabilities, the first network device may not indicate to continue using the first buffer or may indicate not to continue using the first buffer to meet the capabilities requirements of the terminal device. As another example, in a scenario with high latency requirements, the first network device may indicate to continue using the first buffer, and the terminal device needs to perform compression only once. This reduces the processing time of the terminal device, thereby reducing the transmission delay of data packets. It can be seen that the solution of this embodiment of the present application is flexible.

[0191] The scenario to which the embodiment shown in FIG. 7 is applied is a same-site scenario, i.e., the terminal device accesses the same network device before and after handover. A second communication method according to an embodiment of the present application is described below. The method may be applied to the network architecture shown in FIG. 4. FIG. 10 is a flowchart of the method. In the method, the terminal device accesses a first network device before performing a cell handover and accesses a second network device after performing the cell handover. It will be understood that the terminal device hands over from a first cell provided by the first network device to a second cell provided by the second network device, and the first network device and the second network device are different network devices. The terminal device described below is, for example, a terminal device in the network architecture shown in FIG. 4, the first network device described below is, for example, network device 1 in the network architecture shown in FIG. 4, and the second network device described below is, for example, network device 2 in the network architecture shown in FIG. 4.

[0192] S1001: A terminal device transmits capability information to a first network device, and in response, the first network device receives capability information from the terminal device.

[0193] For further details of S1001, please refer to S701 in the embodiment shown in FIG.

[0194] S1002: The terminal device transmits M compressed data packets to the first network device, and in response, the first network device receives K compressed data packets from the terminal device, where M is a positive integer and K is a positive integer less than or equal to M.

[0195] In this embodiment of the present application, after receiving the K compressed data packets, the first network device may send feedback information about the K compressed data packets to the terminal device. For example, the RLC layer of the first network device may send K ACKs to the terminal device. Optionally, the first network device may further send a status report of the K compressed data packets to the terminal device. The status report indicates the compressed data packets received by the first network device, for example, indicates the K compressed data packets. For details, see S702 of the embodiment shown in FIG. 7. Alternatively, the first network device may not send a status report of the K compressed data packets to the terminal device.

[0196] For further details of S1002, please refer to S702 in the embodiment shown in FIG.

[0197] S1003: The first network device sends a first message to the second network device, and in response, the second network device receives a first message from the first network device. The first message may be used to inquire whether the terminal device is supported to continue using the first buffer after handover, or the first message may be used to inquire whether the terminal device is supported to not reset the first buffer when re-establishing the PDCP layer. The first buffer is a buffer maintained by the terminal device and used to compress data packets. When the first buffer is reset, the contents of a third buffer maintained by the second network device and used to decompress data packets also need to be reset. For example, a predefined dictionary is placed in the third buffer. The third buffer is maintained by the second network device, and the second network device may decompress the data packet compressed based on the first buffer based on the third buffer.

[0198] The first buffer, the second buffer, and the third buffer are all corresponding to each other. The first buffer is maintained by the terminal device, and the terminal device compresses data packets based on the first buffer. The second buffer is maintained by the first network device. The terminal device accesses the first network device before performing a cell handover. The first network device may decompress compressed data packets from the terminal device (data packets compressed based on the first buffer) based on the second buffer. The third buffer is maintained by the second network device. The terminal device accesses the second network device after performing a cell handover. The second network device may decompress compressed data packets from the terminal device (data packets compressed based on the first buffer) based on the third buffer.

[0199] For example, the first message may be a handover request message. It will be understood that the handover request message may include inquiry information, and the inquiry information may be used to inquire whether the second network device supports the terminal device continuing to use the first buffer. Alternatively, the first message may be a separate message.

[0200] S1004: The second network device sends a second message to the first network device, and in response, the first network device receives a second message from the second network device. The second message may indicate that the terminal device is supported to continue using the first buffer, or that the terminal device is not supported to continue using the first buffer. Alternatively, the second message may indicate that the terminal device is supported to not reset the first buffer when re-establishing the PDCP layer, or that the terminal device is not supported to not reset the first buffer when re-establishing the PDCP layer. For example, the second message is a handover request acknowledge message. It will be understood that the handover request acknowledge message includes third indication information, and the third indication information may indicate that the terminal device is supported to continue using the first buffer, or that the terminal device is not supported to continue using the first buffer. Alternatively, the third indication information may indicate that the terminal device is supported to not reset the first buffer when re-establishing the PDCP layer, or may indicate that the terminal device is not supported to not reset the first buffer when re-establishing the PDCP layer. Alternatively, the second message may be a separate message.

[0201] Alternatively, the first network device may not need to know whether the second network device supports the terminal device to continue using the first buffer, or the first network device may know in another way whether the second network device supports the terminal device to continue using the first buffer. Therefore, S1003 and S1004 are optional steps.

[0202] S1005: The first network device sends a handover command to the terminal device, and in response, the terminal device receives a handover command from the first network device. The handover command may instruct the terminal device to perform cell handover or instruct PDCP to perform re-establishment. Optionally, the handover command may further include information indicating to the terminal device to continue using the first buffer or not to continue using the first buffer.

[0203] For further details of S1005, please refer to S703 in the embodiment shown in FIG.

[0204] S1006: The terminal device re-establishes the PDCP layer without resetting the first buffer.

[0205] For further details of S1006, please refer to S704 in the embodiment shown in FIG.

[0206] S1007: The first network device re-establishes the PDCP layer without resetting the second buffer.

[0207] For further details of S1007, please refer to S705 in the embodiment shown in FIG.

[0208] S1008: The first network device transmits the contents of the second buffer to the second network device, and in response, the second network device receives the contents of the second buffer from the first network device. For example, the first network device may transmit indication information to the second network device. To distinguish it from the above-mentioned indication information, the indication information may also be referred to as fourth indication information, and the fourth indication information may indicate the contents of the second buffer. For example, the fourth indication information may include the contents of the second buffer (e.g., depending on the size of the second buffer, the typical configuration of the size of the second buffer is 2 kbytes, 4 kbytes, or 8 kbytes), or the fourth indication information may not include the contents of the second buffer, but the second network device may determine the contents of the second buffer based on the fourth indication information.

[0209] If the second network device supports the terminal device continuing to use the first buffer, the first network device may send the fourth indication information to the second network device, or if the second network device does not support the terminal device continuing to use the first buffer, the first network device may not need to send the fourth indication information to the second network device.

[0210] Alternatively, the same message may be used in S1008 and S1003. The first network device may send the contents of the second buffer to the second network device and implicitly or explicitly inquire whether the second network device supports the terminal device continuing to use the first buffer.

[0211] S1009: The second network device updates the third buffer based on the contents of the second buffer.

[0212] The second network device may put the contents of the second buffer into the third buffer or replace the original contents of the third buffer with the contents of the second buffer so that the status of the third buffer matches the status of the second buffer, which is equivalent to matching the status of the third buffer before the data packet is compressed with the status of the first buffer when the data packet is decompressed.

[0213] S1010: A first network device transmits K compressed data packets to a second network device, and in response, the second network device receives the K compressed data packets from the first network device.

[0214] In this embodiment of the present application, since the terminal device performs cell handover, the first network device does not need to decompress the K compressed data packets, but may forward or transmit the K compressed data packets to the second network device via an interface between the network devices (e.g., an Xn interface) so that the second network device processes the K compressed data packets. Alternatively, the first network device may not transmit the K compressed data packets to the second network device; that is, the first network device forwards only successfully decompressed data packets to the second network device. For example, it can be seen from the description of the embodiment shown in FIG. 7 that when the terminal device transmits N consecutive compressed data packets from the first compressed data packet for which no ACK is received, the N compressed data packets include K compressed data packets. In this case, even if the first network device does not transmit the K compressed data packets to the second network device, the second network device may receive the K compressed data packets from the terminal device. Therefore, S1110 is an optional step.

[0215] When a first network device transmits K compressed data packets to a second network device, optionally, after receiving the K compressed data packets, the second network device may transmit a status report of the K compressed data packets to the terminal device. The status report indicates the compressed data packets received by the second network device, for example, indicates the K compressed data packets. Alternatively, the second network device may not transmit a status report to the terminal device. In other words, in this embodiment of the present application, the first network device and / or the second network device may transmit a status report of the K compressed data packets to the terminal device. The terminal device may receive a status report of the K compressed data packets from the first network device, or may receive a status report of the K compressed data packets from the second network device, or may receive a status report of the K compressed data packets from both the first network device and the second network device. Alternatively, in this embodiment of the present application, neither the first network device nor the second network device may send a status report of the K compressed data packets to the terminal device, in which case the terminal device does not receive the status report of the K compressed data packets.

[0216] Furthermore, in addition to the K compressed data packets, the first network device may further receive other compressed data packets from the terminal device, and the first network device may have successfully decompressed these compressed data packets, and the first network device may transmit the successfully decompressed data packets to the second network device.

[0217] S1011: A terminal device transmits N compressed data packets to a second network device, and in response, the second network device receives N compressed data packets from the terminal device. The N compressed data packets are part or all of the M compressed data packets. For example, N is an integer equal to or less than M.

[0218] After successfully performing the cell handover, the terminal device may continue to transmit data packets to the second network device. Thus, the terminal device retransmits N compressed data packets to the second network device. For further details of S1011, please refer to S706 in the embodiment shown in FIG. 7.

[0219] The above describes a case where the terminal device and the first network device do not reset the buffers. If the second indication information received by the terminal device indicates that the first buffer will not continue to be used, or if the protocol specifies that the first buffer will not continue to be used, the terminal device may reset the first buffer when re-establishing the PDCP layer. The first network device also resets the second buffer when re-establishing the PDCP layer. The following describes how the terminal device and the first network device process this case.

[0220] For example, when the PDCP layer of the first network device is re-established, compressed data packets 3, 4, 5, and 7 have been received, but compressed data packets 1, 2, and 6 have not been received. After the PDCP layer receives compressed data packets 3, 4, 5, and 7, a PDCP re-establishment indication may trigger decompression of these compressed data packets, and the PDCP layer fails to decompress compressed data packets 3, 4, 5, and 7. In this case, the PDCP layer may discard compressed data packets 3, 4, 5, and 7, or the PDCP re-establishment indication may trigger the PDCP layer to discard out-of-order compressed data packets (there is a special case where packets from the sender are uncompressed data packets and do not need to be discarded even if these data packets are out-of-order). That is, compressed data packets 3, 4, 5, and 7 are not decompressed, and compressed data packets 3, 4, 5, and 7 are immediately discarded. The solution of immediately discarding out-of-order compressed data packets can reduce the number of decompression operations, improve processing efficiency, save energy consumption, and avoid wasting resources due to ineffective decompression processes. The first network device only needs to send successfully decompressed or out-of-order compressed data packets that are not discarded to the second network device, and does not need to send compressed data packets that fail to be decompressed or are not decompressed to the second network device. Furthermore, after receiving the compressed data packets, the RLC layer of the first network device sends ACK information to the terminal device. For example, for the received compressed data packets, the RLC layer of the first network device sends an ACK to the terminal device.

[0221] After completing the cell handover or re-establishing the PDCP layer, the terminal device may retransmit the compressed data packets to the second network device. For example, the terminal device sequentially retransmits the compressed data packets starting from the first compressed data packet for which no ACK is received. For example, if the terminal device receives ACKs for compressed data packets 0, 3, 4, 5, and 7 but not for compressed data packets 1, 2, and 6, the terminal device retransmits compressed data packets 1 to 7. During the cell handover process, the terminal device re-establishes the PDCP layer and resets the first buffer. In this case, the terminal device recompresses the data packets based on the reset first buffer. Compressed data packets 1 to 7 previously transmitted by the terminal device to the second network device are obtained by compressing data packets 1 to 7 based on the first buffer before resetting, and the terminal device recompresses data packets 1 to 7 based on the reset first buffer to obtain compressed data packets 1 to 7. The terminal device then transmits the compressed data packet to the second network device, and if the first buffer remains unused, it is found that the terminal device needs to perform compression twice on the same data packet.

[0222] S1012: The second network device decompresses the N compressed data packets based on the third buffer, or the second network device decompresses the N compressed data packets and the K compressed data packets based on the third buffer.

[0223] For example, if the N compressed data packets include K compressed data packets, and for example, the second network device does not receive the K compressed data packets from the first network device, or the second network device receives the K compressed data packets from the first network device but the N compressed data packets include K compressed data packets, it will be understood that the second network device decompresses the N compressed data packets based on the third buffer. For example, the M compressed data packets are compressed data packet 1 to compressed data packet 7, the K compressed data packets are compressed data packets 3, 4, 5, and 7, and the N compressed data packets are compressed data packet 1 to compressed data packet 7. In this case, the second network device decompresses compressed data packet 1 to compressed data packet 7 based on the third buffer.

[0224] As another example, when the N compressed data packets do not include K compressed data packets, for example, when the second network device receives K compressed data packets from the first network device and the N compressed data packets do not include K compressed data packets, it will be understood that the second network device decompresses the N compressed data packets and the K compressed data packets based on the third buffer. For example, the M compressed data packets are compressed data packet 1 to compressed data packet 7, the K compressed data packets are compressed data packets 3, 4, 5, and 7, and the N compressed data packets are compressed data packets 1, 2, and 6. In this case, the second network device decompresses compressed data packet 1 to compressed data packet 7 based on the third buffer, and compressed data packet 1 to compressed data packet 7 is the union of the K compressed data packets and the N compressed data packets.

[0225] According to the technical solution provided in this embodiment of the present application, the number of compressions performed by the terminal device can be reduced, and the processing efficiency of the terminal device can be improved. When the first network device and / or the second network device sends a status report to the terminal device, the amount of data sent by the terminal device can be reduced, and transmission overhead can be reduced. Furthermore, since neither the first buffer of the terminal device nor the second buffer of the first network device is reset, and the third buffer of the second network device can be set based on the second buffer, when neither the first network device nor the second network device sends a status report to the terminal device, the second network device can obtain M compressed data packets regardless of whether the second network device decompresses the K compressed data packets after receiving the K compressed data packets, or regardless of whether the second network device receives the K compressed data packets. This reduces the amount of packet loss.

[0226] Both the embodiment shown in Figure 7 and the embodiment shown in Figure 10 describe an uplink data packet compression process, for example, using UDC technology. The embodiment of the present application further provides a downlink data packet compression process, which will be described below.

[0227] An embodiment of the present application provides a third communication method. Figure 11 is a flow chart of the method. The method relates to a downlink data packet compression process. In the process described below, an example is used in which the method is applied to the network architecture shown in Figure 3. The terminal device described below is, for example, a terminal device in the network architecture shown in Figure 3, and the first network device described below is, for example, a network device in the network architecture shown in Figure 3.

[0228] S1101: A terminal device transmits capability information to a first network device, and in response, the first network device receives capability information from the terminal device. The capability information may indicate that a third buffer is supported to continue to be used when PDCP re-establishment occurs, or may indicate that a third buffer is not supported to continue to be used when PDCP re-establishment occurs, or may indicate that a third buffer is supported to not be reset when PDCP layer is re-established, or may indicate that a third buffer is not supported to not be reset when PDCP layer is re-established. The third buffer is maintained by the terminal device and configured to decompress data packets. In other words, the terminal device may decompress the data packets based on the third buffer. For example, the terminal device may decompress the received compressed data packets based on the third buffer by using downlink compression technology.

[0229] The first network device can determine whether the terminal device supports continuing to use the third buffer based on the capability information. If the terminal device supports continuing to use the third buffer, the first network device may select whether to indicate to the terminal device to continue to use the third buffer during handover. If the terminal device does not support continuing to use the third buffer, the first network device does not indicate to the terminal device to continue to use the third buffer. Alternatively, the terminal device may not transmit the capability information. The first network device may determine whether to indicate to the terminal device to continue to use the third buffer based on another factor, or whether the terminal device continues to use the third buffer may be specified in a protocol. Therefore, S1101 is an optional step.

[0230] For further details of S1101, please refer to S701 in the embodiment shown in FIG.

[0231] S1102: A first network device transmits M compressed data packets to a terminal device, and in response, the terminal device receives K compressed data packets from the first network device. M is a positive integer, and K is a positive integer less than or equal to M. The K compressed data packets may be a part or all of the M compressed data packets, or the K compressed data packets are a subset of the M compressed data packets. The M compressed data packets are obtained by the first network device by compressing the M data packets based on a first buffer (or the first buffer in this embodiment of the present application may also be referred to as a second buffer). The first buffer is maintained by the first network device and used by the first network device to compress the data packets. For example, the first network device may compress the data packets based on the first buffer by using a downlink compression technology.

[0232] It should be noted that the first network device may perform corresponding processing on the compressed data packet before transmitting the compressed data packet. For example, the first network device performs integrity protection and encryption processing on the compressed data packet (e.g., performs corresponding processing in the PDCP layer) and delivers the processed compressed data packet to the lowest layer of the first network device (e.g., the RLC layer, the MAC layer, or the physical layer). Then, the lowest layer of the first network device transmits the processed compressed data packet. The first network device may transmit M compressed data packets in a similar manner, and the first network device (or the second network device) may transmit N compressed data packets in a similar manner, as described below. Details will not be described again.

[0233] For further details of S1102, please refer to S701 in the embodiment shown in Figure 7. During the reference, the roles of "terminal device" and "first network device" in S701 may be exchanged.

[0234] S1103: The first network device sends a handover command to the terminal device, and in response, the terminal device receives a handover command from the first network device. The handover command may instruct the terminal device to perform cell handover or re-establishment of a PDCP layer. Optionally, the handover command may further instruct the terminal device to continue using the third buffer when re-establishing PDCP, or to not reset the third buffer when re-establishing PDCP.

[0235] For further details of S1103, please refer to S703 in the embodiment shown in Figure 7. During the reference, in S703, the "first buffer" maintained by the terminal device may be replaced with the "third buffer", and the "second buffer" maintained by the first network device may be replaced with the "first buffer".

[0236] S1104: The terminal device re-establishes the PDCP layer without resetting the third buffer.

[0237] For further details of S1104, please refer to S704 in the embodiment shown in Figure 7. During the reference, the "first buffer" maintained by the terminal device in S704 may be replaced with a "third buffer".

[0238] S1105: The first network device re-establishes the PDCP layer without resetting the first buffer.

[0239] For further details of S1105, please refer to S705 in the embodiment shown in Figure 7. During the reference, the "second buffer" maintained by the first network device in S705 may be replaced with the "first buffer."

[0240] S1106: The first network device transmits N compressed data packets to the terminal device, and in response, the terminal device receives the N compressed data packets from the first network device. The N compressed data packets are part or all of the M compressed data packets. For example, N is an integer equal to or less than M. The first network device may transmit the N compressed data packets in ascending order of sequence numbers of the compressed data packets, starting from the first compressed data packet that is not determined to be successfully received by the terminal device.

[0241] For further details of S1106, please refer to S706 in the embodiment shown in Figure 7. During the reference, the roles of the "terminal device" and the "first network device" in S706 may be exchanged, and the roles of the "first buffer" and the "third buffer" may be exchanged.

[0242] S1107: The terminal device decompresses the N compressed data packets based on the third buffer, or the terminal device decompresses the N compressed data packets and the K compressed data packets based on the third buffer.

[0243] For example, if the N compressed data packets include K compressed data packets, it will be understood that the terminal device decompresses the N compressed data packets based on the third buffer. For example, the M compressed data packets are compressed data packet 1 to compressed data packet 7, the K compressed data packets are compressed data packets 3, 4, 5, and 7, and the N compressed data packets are compressed data packet 1 to compressed data packet 7. In this case, the terminal device decompresses compressed data packet 1 to compressed data packet 7 based on the third buffer.

[0244] As another example, if the N compressed data packets include K compressed data packets, it will be understood that the terminal device decompresses the N compressed data packets and the K compressed data packets based on the third buffer. For example, the M compressed data packets are compressed data packet 1 to compressed data packet 7, the K compressed data packets are compressed data packets 3, 4, 5, and 7, and the N compressed data packets are compressed data packets 1, 2, and 6. In this case, the terminal device decompresses compressed data packet 1 to compressed data packet 7 based on the third buffer, and compressed data packet 1 to compressed data packet 7 is the union of the K compressed data packets and the N compressed data packets.

[0245] According to the technical solution provided in this embodiment of the present application, the number of compressions performed by the first network device can be reduced, and the processing efficiency of the first network device can be improved. When the terminal device sends a status report to the first network device, the amount of data transmitted by the first network device can be reduced, and transmission overhead can be reduced. Furthermore, since neither the third buffer of the terminal device nor the first buffer of the first network device is reset, when the terminal device does not transmit a status report to the first network device, the terminal device can obtain M compressed data packets regardless of whether the terminal device decompresses the K compressed data packets after receiving the K compressed data packets. This reduces the amount of packet loss.

[0246] If the second indication information received by the terminal device indicates that the third buffer is not to be continued to be used, or if the protocol specifies that the third buffer is not to be continued to be used, the terminal device may reset the third buffer. The first network device also resets the first buffer. In this case, for the processing methods of the terminal device and the first network device, please refer to the description of the embodiment shown in Figure 7. During the reference, the roles of the "terminal device" and the "first network device" in the embodiment shown in Figure 7 may be exchanged.

[0247] In this embodiment of the present application, the first network device may indicate whether to continue using the third buffer, and correspondingly, the first network device may indicate whether to continue using the third buffer based on a specific situation. For example, for a terminal device with low capabilities, the first network device may not indicate to continue using the third buffer or may indicate not to continue using the third buffer to meet the capabilities requirements of the terminal device. As another example, in a scenario with high latency requirements, the first network device may indicate to continue using the third buffer, and the first network device needs to perform compression only once. This reduces the processing time of the first network device, thereby reducing the transmission delay of data packets. It can be seen that the solution of this embodiment of the present application is flexible.

[0248] The scenario to which the embodiment shown in FIG. 11 is applied is a same-site scenario, i.e., the terminal device accesses the same network device before and after handover. A fourth communication method according to an embodiment of the present invention will be described below. The method may be applied to the network architecture shown in FIG. 4. FIG. 12 is a flowchart of the method. The method continues with a downlink compression process. In the method, the terminal device accesses a first network device before performing a cell handover and accesses a second network device after performing the cell handover, where the first network device and the second network device are different network devices. The terminal device described below is, for example, a terminal device in the network architecture shown in FIG. 4, the first network device described below is, for example, network device 1 in the network architecture shown in FIG. 4, and the second network device described below is, for example, network device 2 in the network architecture shown in FIG. 4.

[0249] S1201: A terminal device transmits capability information to a first network device, and in response, the first network device receives capability information from the terminal device.

[0250] For further details of S1201, please refer to S701 in the embodiment shown in FIG.

[0251] S1202: A first network device transmits M compressed data packets to a terminal device, and in response, the terminal device receives K compressed data packets from the first network device. M is a positive integer, and K is a positive integer less than or equal to M. The K compressed data packets may be a part or all of the M compressed data packets, or the K compressed data packets are a subset of the M compressed data packets. The M compressed data packets are obtained by the first network device by compressing the M data packets based on a first buffer. The first buffer is maintained by the first network device and used by the first network device to compress the data packets. For example, the first network device may compress the data packets based on the first buffer by using a downlink compression technology.

[0252] For further details of S1202, please refer to S701 in the embodiment shown in Figure 7. During the reference, the roles of "terminal device" and "first network device" in S701 may be exchanged.

[0253] S1203: The first network device sends a first message to the second network device, and in response, the second network device receives a first message from the first network device. The first message may be used to inquire whether the terminal device is supported to continue using the third buffer, or the first message may be used to inquire whether the terminal device is supported to not reset the third buffer when re-establishing the PDCP layer. The third buffer is a buffer maintained by the terminal device and used to decompress data packets. When the third buffer is reset, the contents of the third buffer maintained by the terminal device and used to decompress data packets are in a state that exists after the third buffer is reset. For example, the third buffer is filled with a predefined dictionary. Furthermore, the second network device maintains a second buffer. The second buffer is used by the second network device to compress data packets. For example, the second network device may compress data packets based on the second buffer.

[0254] The first buffer, the second buffer, and the third buffer are all corresponding to each other. The first buffer is maintained by the first network device. The terminal device accesses the first network device before performing a cell handover, and the first network device compresses the data packets based on the first buffer. The second buffer is maintained by the second network device. The terminal device accesses the second network device after performing a cell handover, and the second network device may compress the data packets based on the second buffer. The third buffer is maintained by the terminal device. The terminal device may decompress compressed data packets from the first network device and / or the second network device based on the third buffer. In other words, the terminal device may decompress data packets compressed based on the first buffer based on the third buffer and / or decompress data packets compressed based on the second buffer based on the third buffer.

[0255] For example, it will be understood that the first message is a handover request message, and the handover request message includes inquiry information. The inquiry information may be used to inquire whether the terminal device is supported to continue using the third buffer, or whether the terminal device is supported to not reset the third buffer when re-establishing the PDCP layer. Alternatively, the first message may be a separate message.

[0256] S1204: The second network device sends a second message to the first network device, and in response, the first network device receives a second message from the second network device. The second message may indicate that the terminal device is supported to continue using the third buffer, or may indicate that the terminal device is not supported to continue using the third buffer. For example, it will be understood that the second message is a handover request response message, and the handover request response message includes third indication information. The third indication information may indicate that the terminal device is supported to continue using the third buffer, or may indicate that the terminal device is not supported to continue using the third buffer. Alternatively, the second message may be another message.

[0257] Alternatively, the first network device may not need to know whether the second network device supports the terminal device to continue using the third buffer, or the first network device may know in another way whether the second network device supports the terminal device to continue using the third buffer. Therefore, S1203 and S1204 are optional steps.

[0258] S1205: The first network device sends a handover command to the terminal device, and in response, the terminal device receives a handover command from the first network device. The handover command may instruct the terminal device to perform a cell handover.

[0259] For further details of S1205, please refer to S703 in the embodiment shown in Figure 7. During the reference, in S703, the "first buffer" maintained by the terminal device may be replaced with the "third buffer", and the "second buffer" maintained by the first network device may be replaced with the "first buffer".

[0260] S1206: The terminal device re-establishes the PDCP layer without resetting the third buffer.

[0261] For further details of S1206, please refer to S704 in the embodiment shown in Figure 7. During the reference, the "first buffer" maintained by the terminal device in S704 may be replaced with a "third buffer".

[0262] S1207: The first network device re-establishes the PDCP layer without resetting the first buffer.

[0263] For further details of S1207, please refer to S705 in the embodiment shown in Figure 7. During the reference, the "second buffer" maintained by the first network device in S705 may be replaced with the "first buffer."

[0264] S1208: The first network device transmits the contents of the first buffer to the second network device, and in response, the second network device receives the contents of the first buffer from the first network device. For example, the first network device may transmit indication information to the second network device. To distinguish it from the above-mentioned indication information, the indication information may also be referred to as fourth indication information, and the fourth indication information may indicate the contents of the first buffer. For example, the fourth indication information may include the contents of the first buffer (e.g., depending on the size of the first buffer, the typical size of the contents of the first buffer is 2 kbytes, 4 kbytes, or 8 kbytes), or the fourth indication information may not include the contents of the first buffer, but the second network device may determine the contents of the first buffer based on the fourth indication information.

[0265] Alternatively, the same message is used in S1208 and S1203. The first network device may send the contents of the second buffer to the second network device and implicitly or explicitly inquire whether the second network device supports the terminal device continuing to use the third buffer.

[0266] If the second network device supports the terminal device to continue using the third buffer, the first network device may send the fourth indication information to the second network device, or if the second network device does not support the terminal device to continue using the third buffer, the first network device may not need to send the fourth indication information to the second network device. Therefore, S1208 is an optional step.

[0267] S1209: The second network device updates the second buffer based on the contents of the first buffer.

[0268] The second network device may replace the original contents of the second buffer with the contents of the first buffer such that the status of the second buffer matches the status of the first buffer, which is equivalent to matching the status of the second buffer before the data packet is compressed with the status of the third buffer when the data packet is decompressed.

[0269] S1210: A first network device forwards data packets from a core network device to a second network device, and in response, the second network device receives data packets from the first network device. For example, these data packets include data packets (SDUs) compressed by the first network device and / or include uncompressed data packets (SDUs).

[0270] Before the terminal device performs cell handover, the data packets received from the first network device are data packets from a core network device (e.g., a UPF user plane function). When the terminal device is handed over from the first network device to the second network device, the terminal device's subsequent data packets are transmitted from the core network device to the second network device. When the terminal device performs cell handover, for data packets transmitted by the first network device but not successfully received by the terminal device, the first network device forwards the data packets to the second network device starting from the data packet with the smallest sequence number for which no ACK is received from the terminal device. That is, the first network device forwards data packets for which no ACK is received from the terminal device to the second network device. Some of the data packets forwarded to the second network device may include data packets compressed by the first network device and / or data packets not compressed by the first network device.

[0271] If the first network device is from a core network and does not receive data packets that need to be sent to the terminal device, or if the first network device is from a core network device and has sent all data packets that need to be sent to the terminal device to the terminal device and received an ACK from the terminal device, S1210 does not need to be performed. Therefore, S1210 is an optional step.

[0272] S1211: A second network device transmits N compressed data packets to a terminal device, and in response, the terminal device receives N compressed data packets from the second network device. The N compressed data packets are part or all of the M compressed data packets. For example, N is an integer equal to or less than M. The second network device may transmit the N compressed data packets in ascending order of sequence numbers of the compressed data packets, starting from a first compressed data packet that is not determined to be successfully received by the terminal device.

[0273] After the terminal device successfully performs the cell handover, the second network device continues to send data packets to the terminal device. Because the terminal device has compressed data packets that were not successfully received before the cell handover, the second network device sends N compressed data packets to the terminal device. For example, after updating the second buffer, the second network device may compress the N data packets based on the updated second buffer to obtain N compressed data packets, and then send the N compressed data packets to the terminal device. Some or all of the N data packets may be sent by the first network device to the second network device, or the N data packets may be obtained by the second network device from the core network device. For further content of S1211, please refer to S1011 in the embodiment shown in FIG. 10. In the reference, the roles of "terminal device" and "second network device" may be interchanged. Furthermore, in the reference, if a status report is included, the status report in this embodiment of the present application may indicate K compressed data packets. The status report may be transmitted by the terminal device to the first network device. The first network device may transmit the status report to the second network device. Alternatively, the status report may be transmitted by the terminal device to the second network device.

[0274] S1212: The terminal device decompresses the N compressed data packets based on the third buffer, or the terminal device decompresses the N compressed data packets and the K compressed data packets based on the third buffer.

[0275] For further details of S1212, please refer to S1107 in the embodiment shown in FIG.

[0276] Up to this point, we have described a case where the terminal device and the first network device do not reset the buffer. If the second indication information received by the terminal device indicates that the terminal device does not continue to use the third buffer, or if the protocol specifies that the terminal device does not continue to use the third buffer, the terminal device may reset the third buffer, and the first network device also resets the first buffer. The following describes how the terminal device and the first network device process this case.

[0277] For example, when the PDCP layer of a terminal device is re-established, compressed data packets 3, 4, 5, and 7 have been received, but compressed data packets 1, 2, and 6 have not. After the PDCP layer receives compressed data packets 3, 4, 5, and 7, a PDCP re-establishment indication may trigger decompression of these compressed data packets, and the PDCP layer fails to decompress compressed data packets 3, 4, 5, and 7. In this case, the PDCP layer may discard compressed data packets 3, 4, 5, and 7, or the PDCP re-establishment indication may trigger the PDCP layer to discard out-of-order compressed data packets (there is a special case where packets from the sender are uncompressed data packets and do not need to be discarded even if these data packets are out-of-order). That is, compressed data packets 3, 4, 5, and 7 are not decompressed, and compressed data packets 3, 4, 5, and 7 are immediately discarded. The solution of immediately discarding out-of-order compressed data packets can reduce the number of decompression operations, improve processing efficiency, save energy consumption, and avoid wasting resources for ineffective decompression operations. Furthermore, after receiving the compressed data packets, the RLC layer of the terminal device sends ACK information to the first network device. For example, for the received compressed data packets, the RLC layer of the terminal device sends ACK to the first network device.

[0278] After the terminal device completes the cell handover or the re-establishment of the PDCP layer, the second network device may retransmit the compressed data packets to the terminal device. For example, the second network device sequentially retransmits the compressed data packets starting from the first compressed data packet for which no ACK is received. For example, if the second network device receives ACKs for compressed data packets 0, 3, 4, 5, and 7 but does not receive ACKs for compressed data packets 1, 2, and 6, the second network device retransmits compressed data packets 1 through 7. During the cell handover process, the second network device re-establishes the PDCP layer and resets the second buffer. In this case, the second network device compresses the data packets based on the reset second buffer. Compressed data packets 1 to 7 previously transmitted by the second network device to the terminal device are obtained by compressing data packets 1 to 7 based on the second buffer before resetting, and the second network device re-compresses data packets 1 to 7 based on the reset second buffer to obtain compressed data packets 1 to 7. Then, the second network device transmits the compressed data packets to the terminal device. If the third buffer is not continuously used, it is found that the first network device needs to perform compression and the second network device needs to perform compression again for the same data packets.

[0279] According to the technical solution provided in this embodiment of the present application, the amount of compression times by the network device can be reduced, and the processing efficiency of the network device can be improved. When the terminal device sends a status report to the network device, the amount of data sent by the network device can be reduced, and the transmission overhead can be reduced.

[0280] FIG. 13 is a schematic diagram of the structure of a communication device 1300 according to an embodiment of the present application. The communication device 1300 may be a terminal device in any one of the embodiments shown in FIG. 7, the embodiment shown in FIG. 10, the embodiment shown in FIG. 11, or the embodiment shown in FIG. 12, and is configured to implement a method executed by the terminal device in the above-mentioned method embodiments. Alternatively, the communication device 1300 may be a first network device in any one of the embodiments shown in FIG. 7, the embodiment shown in FIG. 10, the embodiment shown in FIG. 11, or the embodiment shown in FIG. 12, and is configured to implement a method corresponding to the first network device in the above-mentioned method embodiments. Alternatively, the communication device 1300 may be a second network device in any one of the embodiments shown in FIG. 7, the embodiment shown in FIG. 10, the embodiment shown in FIG. 11, or the embodiment shown in FIG. 12, and is configured to implement a method corresponding to the second network device in the above-mentioned method embodiments. For specific functions, please refer to the descriptions in the above-mentioned method embodiments.

[0281] The communications device 1300 includes one or more processors 1301. The processor 1301 may also be referred to as a processing unit and may implement specific control functions. The processor 1301 may be a general-purpose processor, a special-purpose processor, etc., and may include, for example, a baseband processor, a central processing unit, an application processor, a modem processor, a graphics processing unit, an image signal processor, a digital signal processor, a video codec processor, a controller, a memory, and / or a neural network processing unit. The baseband processor may be configured to process communications protocols and communication data. The central processing unit may be configured to control the communications device 1300, execute software programs, and / or process data. The different processors may be separate components or may be integrated into one or more processors, for example, integrated into one or more application-specific integrated circuits.

[0282] Optionally, the communication device 1300 includes one or more memories 1302 configured to store instructions 1304, which may be executed on a processor, causing the communication device 1300 to perform the methods described in the method embodiments above. Optionally, the memory 1302 may further store data. The processor and memory may be located separately or integrated together.

[0283] Optionally, the communication device 1300 may include instructions 1303 (which may also be referred to as code or program), which may be executed on the processor, causing the communication device 1300 to perform the methods described in the above embodiments. The processor 1301 may store data.

[0284] Optionally, the communications device 1300 may further include a transceiver 1305 and an antenna 1306. The transceiver 1305, which may also be referred to as a transceiver unit, transceiver machine, transceiver circuit, transceiver, input / output interface, etc., is configured to perform transceiver functions of the communications device 1300 through the antenna 1306.

[0285] Optionally, communication device 1300 may further include one or more of the following components: a wireless communication module, an audio module, an external memory interface, an internal memory, a universal serial bus (USB) interface, a power management module, an antenna, a speaker, a microphone, an input / output module, a sensor module, a motor, a camera, a display, etc. It will be understood that in some embodiments, communication device 1300 may include more or fewer components, or some components may be integrated, or some components may be separated. These components may be hardware, software, or a combination of software and hardware.

[0286] The processor 1301 and the transceiver 1305 described in this embodiment of the present application may be implemented in an integrated circuit (IC), an analog IC, a radio frequency identification (RFID) integrated circuit, a hybrid signal IC, an application-specific integrated circuit (ASIC), a printed circuit board (PCB), an electronic device, etc. The communication apparatus described herein may be implemented as an independent device (e.g., an independent integrated circuit and a mobile phone), or may be part of a larger device (e.g., a module that can be incorporated into another device). For details, please refer to the above description of the terminal device and the network device. The details will not be described again herein.

[0287] An embodiment of the present application provides a terminal device. The terminal device (referred to as UE for ease of explanation) may be used in the above-described embodiments. The terminal device includes corresponding means, units, and / or circuits used to implement the functions of the terminal device in the embodiments shown in any one or more of Figures 7, 10, 11, or 12. For example, the terminal device includes a transceiver module configured to support the terminal device to perform transceiver functions and a processing module configured to support the terminal device to process signals.

[0288] FIG. 14 is a schematic diagram of the structure of a terminal device according to an embodiment of the present application.

[0289] The terminal device 1400 is applicable to the architecture shown in FIG. 3 or FIG. 4. For ease of explanation, FIG. 14 shows only the main components of the terminal device 1400. As shown in FIG. 14, the terminal device 1400 includes a processor, a memory, a control circuit, an antenna, and an input / output device. The processor is mainly configured to process communication protocols and communication data, control the entire terminal device 1400, execute software programs, and process data of the software programs. The memory is mainly configured to store software programs and data. The control circuit is mainly configured to convert baseband signals and radio frequency signals and process radio frequency signals. The antenna is mainly configured to receive and transmit radio frequency signals in the form of electromagnetic waves. The input / output device, such as a touch screen, a display, a microphone, or a keyboard, is mainly configured to receive data input by a user and output data to the user.

[0290] It is assumed that the terminal device 1400 is a mobile phone as an example. After the terminal device 1400 is powered on, the processor may read a software program in a storage unit, interpret and execute instructions of the software program, and process data of the software program. When data needs to be transmitted wirelessly, the processor performs baseband processing on the data to be transmitted and then outputs a baseband signal to a control circuit. After performing radio frequency processing on the baseband signal, the control circuit transmits the radio frequency signal in the form of electromagnetic waves through an antenna. When data is transmitted to the terminal device 1400, the control circuit receives the radio frequency signal through the antenna, converts the radio frequency signal into a baseband signal, and outputs the baseband signal to the processor. The processor converts the baseband signal into data and processes the data.

[0291] Those skilled in the art will understand that for simplicity of explanation, FIG. 14 shows only one memory and only one processor. In some embodiments, the terminal device 1400 may include multiple processors and memories. A memory may also be referred to as a storage medium, a storage device, etc. This is not limited to this embodiment of the present invention.

[0292] In an optional implementation, the processor may include a baseband processor and a central processing unit. The baseband processor is primarily configured to process communication protocols and communication data. The central processing unit is primarily configured to control the entire terminal device 1400, execute software programs, and process data of the software programs. The processor in FIG. 14 integrates the functions of the baseband processor and the central processing unit. Those skilled in the art will understand that the baseband processor and the central processing unit may alternatively be separate processors and connected to each other using technology such as a bus. The terminal device 1400 may include multiple baseband processors to accommodate different network standards, and the terminal device 1400 may include multiple central processing units to increase the processing power of the terminal device 1400. The components of the terminal device 1400 may be connected using various buses. The baseband processor may also be referred to as a baseband processing circuit or a baseband processing chip. The central processing unit may alternatively be referred to as a central processing circuit or a central processing chip. The functions for processing communication protocols and communication data may be incorporated into the processor or may be stored in the storage unit in the form of a software program, which the processor executes to perform the baseband processing functions.

[0293] In an example, an antenna and control circuitry having transceiver functionality may be considered a transceiver unit 1410 of the terminal device 1400, and a processor having processing functionality may be considered a processing unit 1420 of the terminal device 1400. As shown in FIG. 14, the terminal device 1400 includes a transceiver unit 1410 and a processing unit 1420. The transceiver unit may also be referred to as a transceiver, a transceiver machine, a transceiver apparatus, etc. Optionally, a component within the transceiver unit 1410 that is configured to perform a receiving function may be considered a receiving unit, and a component within the transceiver unit 1410 that is configured to perform a transmitting function may be considered a transmitting unit. That is, the transceiver unit 1410 includes a receiving unit and a transmitting unit. For example, the receiving unit may also be referred to as a receiver, a receiving machine, or a receiving circuit, and the transmitting unit may also be referred to as a transmitter, a transmitting machine, or a transmitting circuit.

[0294] An embodiment of the present application further provides a network device. The network device may be used in the above-described embodiments. The network device includes means, units, and / or circuits for implementing, for example, the functionality of a first network device in the embodiments shown in any one or more of Figures 7, 10, 11, or 12. Alternatively, the network device includes means, units, and / or circuits for implementing, for example, the functionality of a second network device in the embodiments shown in any one or more of Figures 7, 10, 11, or 12. For example, the network device includes a transceiver module configured to support the network device performing transceiver functions and a processing module configured to support the network device processing signals.

[0295] Figure 15 is a schematic diagram of the structure of a network device according to an embodiment of the present application. As shown in Figure 15, the network device is applicable to the architecture shown in Figure 3 or Figure 4. The network device includes a baseband device 1501, a radio frequency device 1502, and an antenna 1503. In the uplink direction, the radio frequency device 1502 receives information transmitted by a terminal device through the antenna 1503 and transmits the information transmitted by the terminal device to the baseband device 1501 for processing. In the downlink direction, the baseband device 1501 processes the information of the terminal device and transmits the information to the radio frequency device 1502. The radio frequency device 1502 processes the information of the terminal device and then transmits the processed information to the terminal device through the antenna 1503.

[0296] The baseband device 1501 includes one or more processing units 15011, a storage unit 15012, and an interface 15013. The processing unit 15011 is configured to support the network device in performing the functions of the network device in the above-described method embodiments. The storage unit 15012 is configured to store software programs and / or data. The interface 15013 is configured to exchange information with the radio frequency device 1502. The interface includes an interface circuit configured to input and output information. In an implementation, the processing unit is an integrated circuit, such as one or more ASICs, one or more DSPs, one or more FPGAs, or a combination of these types of integrated circuits. These integrated circuits may be integrated together to form a chip. The storage unit 15012 and the processing unit 15011 may be located on the same chip, i.e., on-chip storage elements. Alternatively, the storage unit 15012 and the processing unit 15011 may be located on different chips, i.e., off-chip storage elements. The storage unit 15012 may be a single memory, or may be a collective term for multiple memory or storage elements.

[0297] The network device may perform some or all of the steps in the above-described method embodiments by scheduling a program with one or more processing units, such as the corresponding functions of the first network device and / or the second network device in the embodiments shown in any one or more of Figures 7, 10, 11, or 12. The one or more processing units may support radio access technologies of the same standard or may support radio access technologies of different standards.

[0298] Those skilled in the art will know that, in combination with the examples described in the embodiments disclosed herein, the units and methods may be implemented by electronic hardware or a combination of computer software and electronic hardware. Whether a function is performed by hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art may use different methods to implement the described functions for each specific application, but the implementation should not be considered to deviate from the scope of this application.

[0299] It should be understood that the disclosed systems, devices, and methods in some embodiments provided in this application may be implemented differently. For example, the described device embodiments are merely examples. For example, the division of units is merely a division of logical functions, and units described as separate parts may or may not be physically separated, and parts shown as units may or may not be physical units, may be located in one place, or may be distributed across multiple network units. Some or all of the units may be selected based on actual requirements to achieve the objectives of the solutions of the embodiments.

[0300] When a function is implemented in the form of a software functional unit and sold or used as an independent product, the function may be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present application may be basically implemented in the form of a software product, or a part contributing to a common technology or a part of the technical solution may be implemented in the form of a software product. A computer software product is stored in a storage medium and includes some instructions for instructing a computer device (which may be a personal computer, a server, or a network device) to perform all or part of the steps of the method described in the embodiments of the present application. The computer-readable storage medium may be any available medium that can be accessed by a computer. This is used as an example but not a limitation. The computer-readable medium may include random access memory (RAM), read-only memory (ROM), programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), compact disc read-only memory (CD-ROM), universal serial bus flash disk, removable hard disk, other optical disk storage, magnetic disk storage medium, other magnetic storage device, or any other medium that can be configured to carry or store expected program code in the form of instructions or data structures and that can be accessed by a computer.Furthermore, based on the description used by way of example and not limitation, many forms of RAM may be used, such as static random access memory (static RAM, SRAM), dynamic random access memory (dynamic RAM, DRAM), synchronous dynamic random access memory (synchronous DRAM, SDRAM), double data rate synchronous dynamic random access memory (double data rate SDRAM, DDR SDRAM), enhanced synchronous dynamic random access memory (enhanced SDRAM, ESDRAM), synchronous link dynamic random access memory (synchlink DRAM, SLDRAM), or Direct Rambus random access memory (direct rambus RAM, DR RAM).

[0301] The above description is merely a specific implementation of the present application and is not intended to limit the scope of protection of the embodiments of the present application. Any modifications or replacements that can be easily thought of by those skilled in the art within the technical scope disclosed in the embodiments of the present application shall fall within the scope of protection of the embodiments of the present application. Therefore, the scope of protection of the embodiments of the present application shall be subject to the scope of protection of the claims. [Explanation of symbols]

[0302] 1300 Communication Equipment 1301 processor 1302 memory 1303 Command 1304 Instructions 1305 Transceiver 1306 Antenna 1400 Terminal Devices 1410 Transceiver Unit 1420 Processing Unit 1501 Baseband Equipment 15011 Processing Unit 15012 Storage Unit 15013 Interface 1502 Radio Frequency Devices 1503 Antenna

Claims

1. A communication method applied to a terminal device, comprising: transmitting M compressed data packets, wherein the M compressed data packets are obtained by compressing M data packets based on the first buffer, where M is a positive integer; re-establishing a PDCP layer without resetting the first buffer; transmitting N compressed data packets, the N compressed data packets being some or all of the M compressed data packets, where N is a positive integer less than or equal to M; transmitting capability information, the capability information indicating that continuing to use the first buffer is supported; A communication method, including:

2. compressing the M data packets based on the first buffer; 2. The method of claim 1, comprising: compressing each data packet of the M data packets sequentially based on the first buffer, wherein each time a data packet is compressed, the first buffer is updated, and a next data packet is compressed by using the updated first buffer.

3. 3. The method according to claim 1, wherein the data packet having the smallest sequence number among the N compressed data packets is the data packet having the smallest sequence number among the data packets not successfully received by the network device.

4. 4. The method according to claim 1, further comprising the step of receiving a handover command, the handover command instructing to perform a cell handover or to re-establish the PDCP layer, and further instructing to continue using the first buffer.

5. wherein the step of transmitting the M compressed data packets includes transmitting the M compressed data packets to a first network device; 5. The method of claim 1, wherein the step of transmitting N compressed data packets comprises transmitting the N compressed data packets to the first network device.

6. the step of transmitting the M compressed data packets includes transmitting the M compressed data packets to a first network device, the first network device being a network device accessed by the terminal device before the terminal device performs a cell handover; 5. The method according to claim 1, wherein the step of transmitting the N compressed data packets comprises transmitting the N compressed data packets to a second network device, the second network device being a network device accessed by the terminal device after the terminal device performs the cell handover.

7. applied to a first network device, receiving K compressed data packets from a terminal device, wherein the K compressed data packets are obtained by compressing the K data packets based on a first buffer, where K is a positive integer; re-establishing a PDCP layer without resetting a second buffer, the second buffer being used by the first network device to decompress data packets compressed based on the first buffer; receiving capability information from the terminal device, the capability information indicating that the terminal device supports continuing to use the first buffer; A communication method including:

8. 8. The method of claim 7, further comprising the step of transmitting the K compressed data packets to a second network device, wherein the second network device is a network device accessed by the terminal device after the terminal device performs a cell handover, and the first network device is a network device accessed by the terminal device before the terminal device performs the cell handover.

9. 9. The method of claim 7 or 8, further comprising the step of: sending indication information to a second network device, wherein the indication information indicates the contents of the second buffer, the contents of the second buffer are used to update a third buffer, and the third buffer is used by the second network device to decompress the data packet compressed based on the first buffer, the second network device being the network device accessed by the terminal device after the terminal device performs a cell handover, and the first network device being the network device accessed by the terminal device before the terminal device performs the cell handover.

10. sending a first message to a second network device, the first message being used to inquire whether the terminal device is supported to continue using the first buffer, the second network device being the network device accessed by the terminal device after the terminal device performs a cell handover, and the first network device being the network device accessed by the terminal device before the terminal device performs the cell handover; 10. The method of claim 7, further comprising: receiving, by the first network device, a second message from the second network device, the second message indicating that the terminal device is supported to continue using the first buffer.

11. 8. The method of claim 7, further comprising the step of transmitting a status report to the terminal device, the status report indicating that the first network device has received the K compressed data packets.

12. 12. The method of claim 11, further comprising the step of receiving N compressed data packets from the terminal device, wherein the N compressed data packets are part or all of M compressed data packets, the K compressed data packets are part or all of the M compressed data packets, sequence numbers of the M compressed data packets are consecutive, the M compressed data packets are obtained by compressing M data packets based on the first buffer, M is a positive integer, N is a positive integer less than or equal to M, and K is a positive integer less than or equal to M.

13. 13. The method of claim 12, wherein the data packet having the lowest sequence number among the N compressed data packets is the data packet having the lowest sequence number among the data packets not successfully received by the first network device.

14. 14. The method according to claim 7, further comprising the step of sending a handover command to the terminal device, the handover command instructing the terminal device to perform a cell handover or re-establish a PDCP layer, and further instructing the terminal device to continue using the first buffer.

15. applied to a second network device, receiving the K compressed data packets from a first network device to which the method according to any one of claims 7 to 14 is applied, the K compressed data packets being obtained by compressing the K data packets based on the first buffer, the second network device being a network device accessed by the terminal device after the terminal device performs a cell handover, and the first network device being a network device accessed by the terminal device before the terminal device performs the cell handover; receiving an indication from the first network device, the indication indicating the contents of the second buffer, the second buffer being used by the first network device to decompress compressed data packets based on the first buffer; updating a third buffer based on the contents of the second buffer, the third buffer being used by the second network device to decompress the data packets compressed based on the first buffer; receiving a first message from the first network device, the first message being used to inquire whether the terminal device is supported to continue using the first buffer; sending a second message to the first network device, the second message indicating that the terminal device is supported to continue using the first buffer; A communication method including:

16. 16. The method of claim 15, further comprising the step of sending a status report to the terminal device, the status report indicating that the second network device has received the K compressed data packets.

17. 17. The method according to claim 15 or 16, wherein the data packet having the smallest sequence number among the K compressed data packets is the data packet having the smallest sequence number among the data packets not successfully received by the second network device.

18. 18. The method of claim 15, wherein the first buffer corresponds to a first radio bearer, the first radio bearer including some or all of the radio bearers of the terminal device.

19. A terminal device, one or more processors; one or more memories; and one or more computer programs, the one or more computer programs being stored in the one or more memories, the one or more computer programs comprising instructions that, when executed by the one or more processors of the terminal device, enable the terminal device to perform the method of any one of claims 1 to 6.

20. 1. A network device, comprising: one or more processors; one or more memories; and one or more computer programs, the one or more computer programs stored in the one or more memories, the one or more computer programs comprising instructions that, when executed by the one or more processors of the network device, enable the network device to perform the method of any one of claims 7 to 14.

21. 1. A network device, comprising: one or more processors; one or more memories; and one or more computer programs, the one or more computer programs stored in the one or more memories, the one or more computer programs comprising instructions that, when executed by the one or more processors of the network device, enable the network device to perform the method of any one of claims 15 to 18.

22. A computer-readable storage medium configured to store a computer program, the computer program being enabled, when executed on a computer, to perform the method of any one of claims 1 to 6.

23. A computer-readable storage medium configured to store a computer program, the computer program being enabled, when executed on a computer, to perform the method of any one of claims 7 to 14.

24. 19. A computer-readable storage medium configured to store a computer program, the computer program being enabled, when run on a computer, to perform the method of any one of claims 15 to 18.

25. A chip comprising one or more processors and a communication interface, the one or more processors configured to read instructions and to perform the method of any one of claims 1 to 6.

26. A chip comprising one or more processors and a communication interface, the one or more processors configured to read instructions and to perform the method of any one of claims 7 to 14.

27. 19. A chip comprising one or more processors and a communication interface, the one or more processors configured to read instructions and to perform the method of any one of claims 15 to 18.

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