A communication method and apparatus

Abstract

The application relates to a communication method and device. A terminal device sends M compressed data packets, which are obtained by compressing M data packets based on a first buffer. The terminal device reestablishes a PDCP layer and does not reset the first buffer. The terminal device further sends N compressed data packets, which are part or all of the M compressed data packets. In the case that the terminal device reestablishes the PDCP layer and does not reset the first buffer, if the terminal device needs to retransmit data packets, the terminal device can retransmit the previously obtained compressed data packets, and does not need to compress the data packets again, thereby reducing the compression times of the data packets, reducing the processing time of the terminal device, improving the processing efficiency, and reducing the power consumption of the terminal device due to the reduced workload of the terminal device.

Description

[0001] Cross-references to related applications

[0002] This application claims priority to Chinese Patent Application No. 202110086421.0, filed on January 22, 2021, entitled "A Data Transmission Method, Terminal and Network Device", the entire contents of which are incorporated herein by reference. Technical Field

[0003] This application relates to the field of communication technology, and in particular to a communication method and apparatus. Background Technology

[0004] In the acknowledged mode (AM) transmission of the Long Term Evolution (LTE) system, uplink data compression (UDC) technology is introduced and implemented at the packet data convergence protocol (PDCP) layer. UDC technology primarily targets data packets with a large amount of repetitive content, such as the Session Initiation Protocol (SIP) packets transmitted in Voice over Long Term Evolution (VoLTE) services. It reduces the amount of data transmitted by transmitting the differences between data packets.

[0005] When a terminal device undergoes cell handover, it rebuilds the PDCP layer, and the buffer corresponding to the UDC technology is reset. This buffer is used to compress data packets. Before the handover, the base station may not have correctly received data packets from the terminal device. For example, the terminal device might have sent multiple data packets, some of which the base station might not have received, requiring retransmission. Because the buffer used for data packet compression has been reset, the terminal device needs to recompress the data packets based on the reset buffer when retransmitting them. In other words, the terminal device may need to compress the same data packet twice, which undoubtedly increases the processing time and reduces processing efficiency. Summary of the Invention

[0006] This application provides a communication method and apparatus for reducing the number of compression operations on a terminal device, thereby improving the processing efficiency of the terminal device.

[0007] Firstly, a first communication method is provided, which can be executed by a terminal device or by a chip system or other functional module capable of implementing the functions of the terminal device. The method includes: sending M compressed data packets, wherein the M compressed data packets are obtained by compressing M data packets based on a first buffer, where M is a positive integer; reconstructing the PDCP layer without resetting the first buffer; and sending N compressed data packets, wherein 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.

[0008] In this embodiment, when the terminal device rebuilds the PDCP layer, it does not reset the first buffer. Therefore, if the terminal device needs to retransmit data packets, it can simply retransmit the previously obtained compressed data packets without compressing them again. This reduces the number of data packet compressions, decreases the processing time of the terminal device, and improves processing efficiency. Furthermore, by reducing the workload of the terminal device, its power consumption is also reduced.

[0009] In conjunction with the first aspect, in a first optional implementation of the first aspect, the method further includes: receiving a status report, the status report indicating the compressed data packets received by the network device (first network device or second network device). For example, the status report indicates K compressed data packets, and after receiving the status report, the terminal device can know that the network device has received K compressed data packets. For example, the status report can be implemented using a bitmap, which includes M bits, with each of the M bits corresponding to one of the M compressed data packets. If the network device receives a compressed data packet, the corresponding bit is set to "1"; if the network device does not receive a compressed data packet, the corresponding bit is set to "0", thus allowing the terminal device to quickly determine which compressed data packets the network device has received. Alternatively, the status report may include the sequence numbers of the compressed data packets received by the network device, and / or, the sequence numbers of the compressed data packets not received by the network device, thus enabling the terminal device to determine which compressed data packets the network device has received.

[0010] In conjunction with the first optional implementation of the first aspect, in the second optional implementation of the first aspect, the N compressed data packets do not include compressed data packets already received by the network device (first network device or second network device). If the network device sends a status report to the terminal device indicating the compressed data packets already received by the network device, then the terminal device does not need to retransmit the compressed data packets already received by the network device, but only needs to transmit the compressed data packets not received by the network device. This reduces the amount of data retransmitted by the terminal device and saves transmission overhead.

[0011] In conjunction with the first aspect, or the first optional implementation of the first aspect, or the second optional implementation of the first aspect, in the third optional implementation of the first aspect, the data packet with the smallest sequence number among the N compressed data packets is the data packet with the smallest sequence number among the data packets that the network device failed to receive. After the terminal device completes cell handover or after the terminal device completes PDCP layer reconstruction, it can retransmit N compressed data packets to the network device (first network device or second network device). The terminal device can send N compressed data packets in ascending order of their sequence numbers, starting from the first compressed data packet that the network device failed to receive. 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) can be the first compressed data packet that the first network device failed to receive (or the compressed data packet with the smallest sequence number among the data packets that the first network device failed to receive), which can reduce the probability of packet loss by the first network device.

[0012] In a fourth optional embodiment of the first aspect, in conjunction with any of the first to third optional embodiments of the first aspect, the method further includes: sending capability information, the capability information indicating support for continued use of the first cache. The network device (first network device or second network device) can determine whether the terminal device supports continued use of the first cache based on the capability information. If the terminal device supports continued use of the first cache, the network device can instruct the terminal device to continue using the first cache; if the terminal device does not support continued use of the first cache, the network device may not instruct the terminal device to continue using the first cache or may instruct the terminal device to reset the first cache. Alternatively, the terminal device may not send capability information, and the network device may determine whether to instruct the terminal device to continue using the first cache based on other factors, or whether the terminal device continues to use the first cache may be specified by a protocol, etc.

[0013] In a fifth optional embodiment of the first aspect, in conjunction with any of the first to fourth optional embodiments of the first aspect, the method further includes: receiving a handover command, the handover command being used to instruct cell handover or reconstruction of the PDCP layer, and also to instruct continued use of the first cache. For example, the handover command includes first indication information, which may instruct reconstruction of the PDCP layer or instruct cell handover. Optionally, the handover command may further include second indication information, which may instruct continued use of the first cache, or the second indication information may instruct not to reset the first cache during PDCP reconstruction. 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 through other messages. Or, for example, if the protocol specifies continued use of the first cache, or if the protocol specifies not to reset the first cache during PDCP reconstruction, the first network device may not send the second indication information.

[0014] In conjunction with any of the first to fifth optional embodiments of the first aspect, in the sixth optional embodiment of the first aspect, the first cache corresponds to a first radio bearer, and the first radio bearer includes part or all of the radio bearers of the terminal device. For example, if the terminal device is configured to use a radio bearer employing the compression technology provided in the embodiments of this application, one radio bearer may correspond to one cache, with a one-to-one correspondence between the radio bearer and the cache; or, multiple radio bearers may correspond to one cache, for example, space may be allocated separately for different radio bearers in the cache, thus saving the number of caches.

[0015] In conjunction with any of the first optional embodiments of the first aspect or the sixth optional embodiments of the first aspect, in the seventh optional embodiment of the first aspect, sending M compressed data packets includes: sending the M compressed data packets to a first network device; sending N compressed data packets includes: sending the N compressed data packets to the first network device. If the cell handover process of the terminal device is a co-site handover process, that is, the terminal device accesses the first network device before the cell handover and also accesses the first network device after the cell handover, then whether the terminal device sends M compressed data packets or N compressed data packets, it is sending them to the first network device.

[0016] In conjunction with any of the first to sixth optional embodiments of the first aspect, in the eighth optional embodiment of the first aspect, sending M compressed data packets includes: sending the M compressed data packets to a first network device, wherein the first network device is the network device accessed by the terminal device before cell handover; sending N compressed data packets includes: sending the N compressed data packets to a second network device, wherein the first network device is the network device accessed by the terminal device after cell handover. If the cell handover process of the terminal device is an inter-site handover process, that is, the terminal device accesses the first network device before cell handover and the second network device after cell handover, and the terminal device may send M compressed data packets before cell handover and send N compressed data packets after cell handover, therefore 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.

[0017] Secondly, a second communication method is provided, which can be executed by a first network device or by a chip system or other functional module capable of implementing 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: receiving K compressed data packets from a terminal device, wherein the K compressed data packets are obtained by compressing K data packets based on a first buffer, where K is a positive integer; reconstructing the PDCP layer without resetting the second buffer, the second buffer being used by the first network device to decompress the data packets compressed based on the first buffer.

[0018] When the terminal device rebuilds the PDCP layer, it does not reset the first buffer. Therefore, the corresponding first network device also does not reset the second buffer. If the terminal device needs to retransmit data packets, it can retransmit the previously obtained compressed data packets without recompressing them. This reduces the number of data packet compressions, decreases the terminal device's processing time, and improves processing efficiency. Furthermore, reducing the workload of the terminal device also reduces its power consumption. Since the first network device does not reset the second buffer, the states of the first and second buffers remain consistent. Therefore, the first network device can decompress compressed data packets from the terminal device, reducing its packet loss rate.

[0019] In conjunction with the second aspect, in the first optional implementation of the second aspect, the sequence numbers of the K data packets are not consecutive with the sequence numbers of the data packets already decompressed by the first network device. For example, if the sequence numbers of the K compressed data packets are not consecutive with the sequence numbers of the last data packet that the first network device has successfully decompressed and delivered to the upper layer, it indicates that the first network device has unreceived compressed data packets, and these unreceived compressed data packets will affect the first network device's decompression of the K compressed data packets.

[0020] In conjunction with the second aspect or the first optional implementation of the second aspect, in the second optional implementation of the second aspect, the method further includes: sending the K compressed data packets to a second network device, wherein the second network device is the network device accessed by the terminal device after cell handover, and the first network device is the network device accessed by the terminal device before cell handover. For example, the cell handover process of the terminal device is an inter-site handover process, that is, the terminal device accesses the first network device before cell handover, and accesses the second network device after cell handover. Therefore, since the terminal device has performed cell handover, the first network device does not need to decompress the K compressed data packets, but can forward or send the K compressed data packets to the second network device through a network device interface (such as port Xn), whereby the second network device processes the K compressed data packets.

[0021] In conjunction with the second aspect, or the first optional implementation of the second aspect, or the second optional implementation of the second aspect, in the third optional implementation of the second aspect, the method further includes: sending indication information to a second network device, the indication information being used to indicate the content of the second cache, the content of the second cache being used to update a third cache, the third cache being used by the second network device to decompress data packets compressed based on the first cache, wherein the second network device is the network device accessed by the terminal device after cell handover, and the first network device is the network device accessed by the terminal device before cell handover. For example, the cell handover process of the terminal device is an inter-site handover process, that is, the terminal device accessed the first network device before cell handover, and accessed the second network device after cell handover. Then the first network device can indicate the content of the second cache to the second network device, and the second network device can update the third cache maintained by the second network device according to the content of the second cache, so that the state of the third cache is consistent with that of the first cache, thereby enabling the second network device to correctly decompress the compressed data packets from the terminal device.

[0022] In a fourth optional embodiment of the second aspect, in conjunction with any of the first to third optional embodiments of the second aspect, the method further includes: sending a first message to the second network device, the first message being used to inquire whether the terminal device is supported to continue using the first cache, wherein the second network device is the network device accessed by the terminal device after cell handover, and the first network device is the network device accessed by the terminal device before cell handover; the first network device receiving a second message from the second network device, the second message being used to indicate support for the terminal device to continue using the first cache. For example, if the cell handover process of the terminal device is an inter-site handover process, that is, the terminal device accessed the first network device before cell handover and accessed the second network device after cell handover, then the first network device can inquire with the second network device whether the terminal device is supported to continue using the first cache. For example, if the second network device does not support the terminal device to continue using the first cache, then the first network device can configure the terminal device to reset the first cache so that the behavior of the terminal device is consistent with the behavior supported by the second network device.

[0023] In conjunction with the second aspect or the first optional implementation of the second aspect, in the fifth optional implementation of the second aspect, the method further includes: sending a status report to the terminal device, the status report indicating that the first network device has received the K compressed data packets.

[0024] In conjunction with the fifth optional implementation of the second aspect, in the sixth optional implementation of the second aspect, the method further includes: 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, 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.

[0025] In conjunction with the sixth optional implementation of the second aspect, in the seventh optional implementation of the second aspect, the N compressed data packets do not include the K compressed data packets.

[0026] In conjunction with the fifth, sixth, or seventh optional implementation of the second aspect, in the eighth optional implementation of the second aspect, the data packet with the smallest sequence number among the N compressed data packets is the data packet with the smallest sequence number among the data packets that the first network device failed to receive.

[0027] In conjunction with any of the optional embodiments of the second aspect or the first to eighth optional embodiments of the second aspect, in the ninth optional embodiment of the second aspect, the method further includes: receiving capability information from the terminal device, the capability information being used to indicate that the terminal device supports continued use of the first cache.

[0028] In conjunction with any of the optional embodiments of the second aspect or the first to the ninth optional embodiments of the second aspect, in the tenth optional embodiment of the second aspect, the method further includes: sending a handover command to the terminal device, the handover command being used to instruct cell handover or rebuild the PDCP layer, and also to instruct continued use of the first cache.

[0029] In conjunction with any of the first to tenth optional embodiments of the second aspect, in the eleventh optional embodiment of the second aspect, the first buffer corresponds to a first radio bearer, the first radio bearer including part or all of the radio bearer of the terminal device.

[0030] For information on the technical effects of the second aspect or some of the optional implementation methods, please refer to the description of the technical effects of the first aspect or corresponding implementation methods.

[0031] Thirdly, a third communication method is provided, which can be executed by a second network device or by a chip system or other functional module capable of implementing 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 K compressed data packets from a first network device, the K compressed data packets being obtained by compressing K data packets based on a first buffer; the second network device being the network device accessed by the terminal device after cell handover, and the first network device being the network device accessed by the terminal device before cell handover; receiving indication information from the first network device, the indication information indicating the content of a second buffer, the second buffer being used by the first network device to decompress data packets compressed based on the first buffer; and updating a third buffer according to the content of the second buffer, the third buffer being used by the second network device to decompress data packets compressed based on the first buffer.

[0032] In conjunction with the third aspect, in the first optional implementation of the third aspect, the sequence numbers of the K data packets are not consecutive with the sequence numbers of the data packets already received by the second network device.

[0033] In conjunction with the third aspect or the first optional implementation of the third aspect, in the second optional implementation of the third aspect, the method further includes: 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, 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.

[0034] In conjunction with the third aspect, or the first optional implementation of the third aspect, or the second optional implementation of the third aspect, in the third optional implementation of the third aspect, the method further includes: 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 cache; and sending a second message to the first network device, the second message being used to indicate that the terminal device is supported to continue using the first cache.

[0035] In conjunction with any of the optional embodiments of the third aspect or the first to the third optional embodiments of the third aspect, in the fourth optional embodiment of the third aspect, the method further includes: sending a status report to the terminal device, the status report indicating that the second network device has received the K compressed data packets.

[0036] In conjunction with the fourth optional implementation of the third aspect, in the fifth optional implementation of the third aspect, the N compressed data packets do not include the K compressed data packets.

[0037] In conjunction with any of the optional embodiments of the third aspect or the first to fifth optional embodiments of the third aspect, in the sixth optional embodiment of the third aspect, the data packet with the smallest sequence number among the N compressed data packets is the data packet with the smallest sequence number among the data packets that the second network device failed to receive.

[0038] In conjunction with any of the optional embodiments of the third aspect or the first to sixth optional embodiments of the third aspect, in the seventh optional embodiment of the third aspect, the first buffer corresponds to the first radio bearer, the first radio bearer including part or all of the radio bearer of the terminal device.

[0039] Regarding the technical effects of the third aspect or various alternative implementations, 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.

[0040] The method described in any one or more of the first, second, or third aspects involves an uplink compression process.

[0041] Fourthly, a fourth communication method is provided, which can be executed by a first network device or by a chip system or other functional module capable of implementing 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 M compressed data packets to a terminal device, wherein the M compressed data packets are obtained by compressing M data packets based on a first buffer, where M is a positive integer; reconstructing the PDCP layer without resetting the first buffer.

[0042] In this embodiment, when the first network device rebuilds the PDCP layer, it does not reset the first buffer. Therefore, if the first network device needs to retransmit data packets, it can simply retransmit the previously obtained compressed data packets without compressing them again. This reduces the number of data packet compressions, decreases the processing time of the first network device, and improves processing efficiency. Moreover, by reducing the workload of the first network device, its power consumption is also reduced.

[0043] In conjunction with the fourth aspect, in a first optional implementation of the fourth aspect, the method further includes: sending indication information to a second network device, the indication information being used to indicate the content of the first cache, the content of the first cache being used to update the second cache, the second cache being used by the second network device to compress data packets, the first network device being a network device accessed by the terminal device before cell handover, and the second network device being a network device accessed by the terminal device after cell handover.

[0044] In conjunction with the fourth aspect or the first optional implementation of the fourth aspect, in the second optional implementation of the fourth aspect, the method further includes: 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 third cache, the first network device being a network device accessed by the terminal device before cell handover, and the second network device being a network device accessed by the terminal device after cell handover; and receiving a second message from the second network device, the second message being used to indicate support for the terminal device to continue using the third cache.

[0045] In conjunction with the fourth aspect, in a third optional implementation of the fourth aspect, the method further includes: receiving a status report from the terminal device, the status report indicating compressed data packets that the terminal device has received.

[0046] In conjunction with the third optional implementation of the fourth aspect, in the fourth optional implementation of the fourth aspect, the method further includes: sending N compressed data packets to the terminal device, wherein the N compressed data packets are part or all of the M compressed data packets, and N is a positive integer less than or equal to M.

[0047] In conjunction with the fourth optional implementation of the fourth aspect, in the fifth optional implementation of the fourth aspect, the N compressed data packets do not include the compressed data packets already received by the terminal device.

[0048] In conjunction with the third optional implementation of the fourth aspect, or the fourth optional implementation of the fourth aspect, or the fifth optional implementation of the fourth aspect, in the sixth optional implementation of the fourth aspect, the data packet with the smallest sequence number among the N compressed data packets is the data packet with the smallest sequence number among the data packets that the terminal device failed to receive.

[0049] In a seventh optional embodiment of the fourth aspect, in conjunction with any of the first to sixth optional embodiments of the fourth aspect, the method further includes: receiving capability information from the terminal device, the capability information being used to indicate that the terminal device supports continued use of a third cache, the third cache being used by the terminal device to decompress data packets compressed based on the first cache or the second cache, the second cache being used by a second network device to compress data packets, the second network device being a network device accessed by the terminal device after cell handover.

[0050] In conjunction with any of the optional embodiments of the fourth aspect or the first to seventh optional embodiments of the fourth aspect, in the eighth optional embodiment of the fourth aspect, the method further includes: sending a handover command to the terminal device, the handover command being used to instruct cell handover or rebuild the PDCP layer, and also being used to instruct the terminal device 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, the second buffer being used by a second network device to compress data packets, the second network device being the network device accessed by the terminal device after cell handover.

[0051] Regarding the technical effects of the fourth aspect or various optional embodiments, reference can be made to the description of the technical effects of the first aspect or corresponding embodiments, and / or, to the description of the technical effects of the second aspect or corresponding embodiments, and / or, to the description of the technical effects of the third aspect or corresponding embodiments.

[0052] Fifthly, a fifth communication method is provided, which can be executed by a second network device or by a chip system or other functional module capable of implementing 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 content of a first cache, the first cache 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 cell handover, and the first network device being a network device accessed by the terminal device before cell handover; updating a second cache according to the content of the first cache, the second cache being used by the second network device to compress data packets.

[0053] In conjunction with the fifth aspect, in a first optional implementation of the fifth aspect, the method further includes: receiving a first message from a first network device, the first message being used to inquire whether the terminal device is supported to continue using the third cache; and sending a second message to the first network device, the second message being used to indicate support for the terminal device to continue using the third cache.

[0054] In conjunction with the fifth aspect or the first optional implementation of the fifth aspect, in the second optional implementation of the fifth aspect, the method further includes: receiving a status report from the terminal device, the status report indicating compressed data packets that the terminal device has received.

[0055] In conjunction with the second optional implementation of the fifth aspect, in the third optional implementation of the fifth aspect, the method further includes: compressing the data packets according to the updated second cache to obtain N compressed data packets; and sending the N compressed data packets to the terminal device.

[0056] In conjunction with the third optional implementation of the fifth aspect, in the fourth optional implementation of the fifth aspect, the N compressed data packets do not include the compressed data packets already received by the terminal device.

[0057] In conjunction with the third optional implementation of the fifth aspect or the fourth optional implementation of the fifth aspect, in the fifth optional implementation of the fifth aspect, the data packet with the smallest sequence number among the N compressed data packets is the data packet with the smallest sequence number among the data packets that the terminal device failed to receive.

[0058] Regarding the technical effects of the fifth aspect or various alternative embodiments, reference can be made to the description of the technical effects of the first aspect or corresponding embodiments, and / or, to the description of the technical effects of the second aspect or corresponding embodiments, and / or, to the description of the technical effects of the third aspect or corresponding embodiments.

[0059] Sixthly, a sixth communication method is provided, which can be executed by a terminal device or by a chip system or other functional module capable of implementing the functions of the terminal device. The method includes: receiving K compressed data packets, the K compressed data packets being obtained by compressing K data packets based on a first buffer; reconstructing the PDCP layer without resetting the third buffer; receiving N compressed data packets, the N compressed data packets being obtained by compressing N data packets based on a second buffer, where K and N are both positive integers; 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.

[0060] In conjunction with the sixth aspect, in a first optional implementation of the sixth aspect, receiving K compressed data packets includes: receiving the K compressed data packets from a first network device; receiving N compressed data packets includes: receiving the N compressed data packets from the first network device.

[0061] In conjunction with the first optional implementation of the sixth aspect, in the second optional implementation of the sixth aspect, the first cache and the second cache are the same cache, and the first cache is maintained by the first network device.

[0062] In conjunction with the sixth aspect, in a third optional implementation of the sixth aspect, receiving K compressed data packets includes: receiving the K compressed data packets from a first network device; receiving N compressed data packets includes: receiving the N compressed data packets from a second network device, wherein the second network device is a network device accessed by the terminal device after cell handover, and the first network device is a network device accessed by the terminal device before cell handover.

[0063] In conjunction with the third optional implementation of the sixth aspect, in the fourth optional implementation of the sixth aspect, the first cache is maintained by the first network device, and the second cache is maintained by the second network device.

[0064] In conjunction with the sixth aspect or the first to fourth optional embodiments of the sixth aspect, in the fifth optional embodiment of the sixth aspect, the sequence numbers of the K data packets are not consecutive with the sequence numbers of the data packets that have been decompressed by the terminal device.

[0065] In conjunction with the sixth aspect or the first to fifth optional embodiments of the sixth aspect, in the sixth optional embodiment of the sixth aspect, the data packet with the smallest sequence number among the N compressed data packets is the data packet with the smallest sequence number among the data packets that the terminal device failed to receive.

[0066] In conjunction with the sixth aspect or the first to sixth optional embodiments of the sixth aspect, in the seventh optional embodiment of the sixth aspect, the method further includes: sending a status report, the status report indicating that the terminal device has received the K compressed data packets.

[0067] In conjunction with the seventh optional implementation of the sixth aspect, in the eighth optional implementation of the sixth aspect, the N compressed data packets do not include the K compressed data packets.

[0068] In conjunction with the sixth aspect or the first to eighth optional embodiments of the sixth aspect, in the ninth optional embodiment of the sixth aspect, the method further includes: receiving a handover command, the handover command being used to instruct cell handover or rebuild the PDCP layer, and also being used to instruct the terminal device to continue using the third cache.

[0069] In conjunction with the sixth aspect or the first to ninth optional embodiments of the sixth aspect, in the tenth optional embodiment of the sixth aspect, the method further includes: sending capability information, the capability information being used to indicate that the terminal device supports continued use of the third cache.

[0070] Regarding the technical effects of the sixth aspect or various alternative embodiments, reference can be made to the description of the technical effects of the first aspect or corresponding embodiments, and / or, to the description of the technical effects of the second aspect or corresponding embodiments, and / or, to the description of the technical effects of the third aspect or corresponding embodiments.

[0071] The method described in any one or more of the fourth, fifth, or sixth aspects involves a downlink compression process.

[0072] A seventh aspect provides a seventh communication method, which can be executed by a terminal device or by a chip system or other functional module capable of implementing 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 the reconstruction of the PDCP layer or cell handover, and the second indication information indicating that the terminal device continues to use a first buffer, the first buffer being used by the terminal device to compress data packets; reconstructing the PDCP layer without resetting the first buffer.

[0073] In conjunction with the seventh aspect, in a first optional implementation of the seventh aspect, the method further includes: receiving a status report, the status report indicating compressed data packets that the network device has received.

[0074] In conjunction with the first optional implementation of the seventh aspect, in the second optional implementation of the seventh aspect, the method further includes: starting from the first compressed data packet that was not confirmed to have been successfully received, sending N compressed data packets in ascending order of their sequence numbers, where N is a positive integer.

[0075] In conjunction with the second optional implementation of the seventh aspect, in the third optional implementation of the seventh aspect, starting from the first compressed data packet that was not confirmed to have been successfully received, N compressed data packets are sent in ascending order of their sequence numbers, including: performing integrity protection and encryption processing on the N compressed data packets; and sending the processed N compressed data packets.

[0076] In a fourth optional embodiment of the seventh aspect, in conjunction with any of the first to third optional embodiments of the seventh aspect, the method further includes: sending capability information to indicate support for continued use of the first cache.

[0077] In conjunction with any of the optional embodiments of the seventh aspect or the first to fourth optional embodiments of the seventh aspect, in the fifth optional embodiment of the seventh aspect, the first buffer corresponds to a first radio bearer, the first radio bearer including part or all of the radio bearer of the terminal device.

[0078] Regarding the technical effects of the seventh aspect or various alternative embodiments, reference can be made to the description of the technical effects of the first aspect or corresponding embodiments, and / or, to the description of the technical effects of the second aspect or corresponding embodiments, and / or, to the description of the technical effects of the third aspect or corresponding embodiments.

[0079] Eighthly, an eighth communication method is provided, which can be executed by a first network device or by a chip system or other functional module capable of implementing the functions of the first network device. Exemplarily, 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 the reconstruction of the PDCP layer or cell handover, and the second indication information indicating continued use of a first buffer, the first buffer being used by the terminal device to compress data packets; reconstructing the 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.

[0080] In conjunction with the eighth aspect, in a first optional implementation of the eighth aspect, the method further includes: sending K compressed data packets to a second network device, the K compressed data packets originating from the terminal device, the second network device being a network device accessed by the terminal device after cell handover, and the first network device being a network device accessed by the terminal device before cell handover.

[0081] In conjunction with the eighth aspect or the first optional implementation of the eighth aspect, in the second optional implementation of the eighth aspect, the method further includes: sending indication information to a second network device, the indication information being used to indicate the content of the second cache, the content of the second cache being used to update a third cache, the third cache being used by the second network device to decompress data packets compressed based on the first cache, the second network device being a network device accessed by the terminal device after cell handover, and the first network device being a network device accessed by the terminal device before cell handover.

[0082] In conjunction with the eighth aspect, or the first optional implementation of the eighth aspect, or the second optional implementation of the eighth aspect, in the third optional implementation of the eighth aspect, the method further includes: sending a first message to the second network device, the first message being used to inquire whether the terminal device is supported to continue using the first cache, the second network device being a network device accessed by the terminal device after cell handover, and the first network device being a network device accessed by the terminal device before cell handover; the first network device receiving a second message from the second network device, the second message being used to indicate support for the terminal device to continue using the first cache.

[0083] In conjunction with the eighth aspect, in a fourth optional implementation of the eighth aspect, the method further includes: sending a status report to the terminal device, the status report indicating the compressed data packets that the first network device has received.

[0084] In conjunction with the fourth optional implementation of the eighth aspect, in the fifth optional implementation of the eighth aspect, the method further includes: receiving N compressed data packets from the terminal device, wherein the data packet with the smallest sequence number among the N compressed data packets is the data packet with the smallest sequence number among the data packets that the first network device failed to receive.

[0085] In conjunction with the fifth optional implementation of the eighth aspect, in the sixth optional implementation of the eighth aspect, the N compressed data packets do not include the compressed data packets already received by the first network device.

[0086] In conjunction with the eighth aspect, or the first optional implementation of the eighth aspect, or the sixth optional implementation of the eighth aspect, in the seventh optional implementation of the eighth aspect, the method further includes: receiving capability information from the terminal device, the capability information being used to indicate that the terminal device supports continued use of the first cache.

[0087] In conjunction with the eighth aspect or the first optional implementation of the eighth aspect or the sixth optional implementation of the seventh aspect, in the eighth optional implementation of the eighth aspect, the first buffer corresponds to the first radio bearer, the first radio bearer including part or all of the radio bearer of the terminal device.

[0088] Regarding the technical effects of the eighth aspect or various alternative embodiments, reference can be made to the description of the technical effects of the first aspect or corresponding embodiments, and / or, to the description of the technical effects of the second aspect or corresponding embodiments, and / or, to the description of the technical effects of the third aspect or corresponding embodiments.

[0089] The methods described in the seventh and / or eighth aspects involve an uplink compression process.

[0090] A ninth aspect provides a ninth communication method, which can be executed by a first network device or by a chip system or other functional module capable of implementing the functions of the first network device. Exemplarily, 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 the reconstruction of the PDCP layer or cell handover, and the second indication information indicating continued use of 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; reconstructing the PDCP layer without resetting the first buffer, the first buffer being used by the first network device to compress data packets.

[0091] In conjunction with the ninth aspect, in a first optional embodiment of the ninth aspect, the method further includes: sending indication information to a second network device, the indication information being used to indicate the content of the first cache, the content of the first cache being used to update a second cache, the second cache being used by the second network device to compress data packets, the first network device being a network device accessed by the terminal device before cell handover, and the second network device being a network device accessed by the terminal device after cell handover.

[0092] In conjunction with the ninth aspect or the first optional implementation of the ninth aspect, in the second optional implementation of the ninth aspect, the method further includes: 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 third cache, the first network device being a network device accessed by the terminal device before cell handover, and the second network device being a network device accessed by the terminal device after cell handover; and receiving a second message from the second network device, the second message being used to indicate support for the terminal device to continue using the third cache.

[0093] In conjunction with the ninth aspect, in a third optional embodiment of the ninth aspect, the method further includes: receiving a status report from the terminal device, the status report indicating compressed data packets that the terminal device has received.

[0094] In conjunction with the third optional implementation of the ninth aspect, in the fourth optional implementation of the ninth aspect, the method further includes: starting from the first compressed data packet that was not confirmed to have been successfully received, sending N compressed data packets to the terminal device in ascending order of the sequence number of the compressed data packets, where N is a positive integer.

[0095] In conjunction with the fourth optional implementation of the ninth aspect, in the fifth optional implementation of the ninth aspect, starting from the first compressed data packet that was not successfully received, N compressed data packets are sent to the terminal device in ascending order of their sequence numbers, including: performing integrity protection and encryption on the N compressed data packets; and sending the processed N compressed data packets to the terminal device.

[0096] In conjunction with the fourth optional implementation of the ninth aspect or the fifth optional implementation of the ninth aspect, in the sixth optional implementation of the ninth aspect, the data packet with the smallest sequence number among the N compressed data packets is the data packet with the smallest sequence number among the data packets that the terminal device failed to receive.

[0097] In conjunction with the fourth, fifth, or sixth optional implementation of the ninth aspect, in the seventh optional implementation of the ninth aspect, the N compressed data packets do not include the compressed data packets already received by the terminal device.

[0098] In an eighth optional embodiment of the ninth aspect, in conjunction with any of the first to seventh optional embodiments of the ninth aspect, the method further includes: receiving capability information from the terminal device, the capability information being used to indicate that the terminal device supports continued use of the third cache.

[0099] Regarding the technical effects of the ninth aspect or various alternative embodiments, reference can be made to the description of the technical effects of the first aspect or corresponding embodiments, and / or, to the description of the technical effects of the second aspect or corresponding embodiments, and / or, to the description of the technical effects of the third aspect or corresponding embodiments.

[0100] The method described in the ninth aspect involves a downlink compression process.

[0101] A tenth aspect provides a communication device. The communication device may be a terminal device as described in any one of the first to ninth aspects above. The communication device possesses the functions of the aforementioned terminal device. The terminal device is, for example, a base station, or a baseband device within a base station. In one 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 (sometimes also called a processing module) and a transceiver unit (sometimes also called a transceiver module). The transceiver unit is capable of performing both transmitting and receiving functions. When the transceiver unit performs the transmitting function, it may be called a transmitting unit (sometimes also called a transmitting module), and when the transceiver unit performs the receiving function, it may be called a receiving unit (sometimes also called a receiving module). The transmitting unit and the receiving unit may be the same functional module, which is called the transceiver unit and can perform both transmitting and receiving functions; or, the transmitting unit and the receiving unit may be different functional modules, with the transceiver unit being a collective term for these functional modules.

[0102] The transceiver unit (or the sending unit) is used to send M compressed data packets, wherein the M compressed data packets are obtained by compressing M data packets based on the first buffer, and M is a positive integer;

[0103] The processing unit is used to rebuild the PDCP layer without resetting the first cache;

[0104] The transceiver unit (or the sending unit) is further configured to send N compressed data packets, wherein the N compressed data packets are part or all of the M compressed data packets, and N is a positive integer less than or equal to M.

[0105] or,

[0106] The transceiver unit (or the receiving unit) is configured to receive K compressed data packets, wherein the K compressed data packets are obtained by compressing the K data packets based on the first buffer;

[0107] The processing unit is used to rebuild the PDCP layer without resetting the third cache;

[0108] The transceiver unit (or the receiving unit) is further configured to receive N compressed data packets, wherein the N compressed data packets are compressed based on the second buffer, and K and N are both positive integers;

[0109] The processing unit is further configured to decompress the K compressed data packets and the N compressed data packets based on the third cache, or to decompress the N compressed data packets based on the third cache.

[0110] or,

[0111] 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 being configured to indicate the reconstruction of the PDCP layer or cell handover, and the second indication information being configured to indicate the terminal device to continue using the first buffer, the first buffer being used by the terminal device to compress data packets;

[0112] The processing unit is used to rebuild the PDCP layer without resetting the first cache.

[0113] In one alternative implementation, the communication device further includes a storage unit, and the processing unit is configured to couple with the storage unit and execute programs or instructions in the storage unit to enable the communication device to perform the functions of the terminal device described in any one of the first to ninth aspects above.

[0114] Eleventhly, a communication device is provided. The communication device may be a first network device as described in any of the first to ninth aspects above. The communication device possesses the functions of the first network device. The first network device is, for example, a base station, or a baseband device within a base station. In one 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 (sometimes also called a processing module) and a transceiver unit (sometimes also called a transceiver module). The implementation of the transceiver unit can be referred to the description in the fourth aspect.

[0115] The transceiver unit (or the receiving unit) is configured to receive K compressed data packets from the terminal device, wherein the K compressed data packets are obtained by compressing the K data packets based on the first buffer, and K is a positive integer;

[0116] The processing unit is used to rebuild the PDCP layer without resetting the second cache, which is used by the first network device to decompress data packets compressed based on the first cache.

[0117] or,

[0118] The transceiver unit (or the receiving unit) is configured to receive K compressed data packets from the first network device. The K compressed data packets are obtained by compressing the K data packets based on the first buffer. The second network device is the network device that the terminal device accesses after cell handover, and the first network device is the network device that the terminal device accesses before cell handover.

[0119] The transceiver unit (or the receiving unit) is further configured to receive indication information from the first network device, the indication information being used to indicate the contents of the second cache, the second cache being used by the first network device to decompress data packets compressed based on the first cache;

[0120] The processing unit is configured to update the third cache according to the content of the second cache, the third cache being used by the second network device to decompress data packets compressed based on the first cache.

[0121] or,

[0122] The transceiver unit (or the sending unit) is used to send M compressed data packets to the terminal device. The M compressed data packets are obtained by compressing M data packets based on the first buffer, where M is a positive integer.

[0123] The processing unit is used to rebuild the PDCP layer without resetting the first cache.

[0124] or,

[0125] The transceiver unit (or the receiving unit) is configured to receive indication information from the first network device. The indication information is used to indicate the contents of the first buffer. The first buffer is used by the first network device to compress data packets. The second network device is the network device that the terminal device accesses after cell handover, and the first network device is the network device that the terminal device accesses before cell handover.

[0126] The processing unit is used to update the second cache according to the content of the first cache, and the second cache is used by the second network device to compress data packets.

[0127] or,

[0128] The transceiver unit (or the sending unit) is used to send a handover command to the terminal device. The handover command includes first indication information and second indication information. The first indication information is used to indicate the reconstruction of the PDCP layer or cell handover. The second indication information is used to indicate the continued use of the first buffer. The first buffer is used by the terminal device to compress data packets.

[0129] The processing unit is used to rebuild the PDCP layer without resetting the second cache, which is used by the first network device to decompress data packets compressed based on the first cache.

[0130] or,

[0131] The transceiver unit (or the sending unit) is used to send a handover command to the terminal device. The handover command includes first indication information and second indication information. The first indication information is used to indicate the reconstruction of the PDCP layer or cell handover. The second indication information is used to indicate the continued use of the third buffer. The third buffer is used by the terminal device to decompress data packets compressed based on the first buffer or the second buffer.

[0132] The processing unit is used to rebuild the PDCP layer without resetting the first cache, which is used by the first network device to compress data packets.

[0133] In one alternative implementation, the communication device further includes a storage unit, and the processing unit is configured to couple with 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 described in any one of the first to ninth aspects above.

[0134] In a twelfth aspect, a computer-readable storage medium is provided for storing a computer program or instructions that, when executed, cause the methods performed by the terminal device, the first network device, or the second network device in the foregoing aspects to be implemented.

[0135] In a thirteenth aspect, a computer program product containing instructions is provided that, when run on a computer, enables the methods described in the above aspects to be implemented. Attached Figure Description

[0136] Figure 1 This is a schematic diagram illustrating the compression and decompression process of data packets in an LTE system.

[0137] Figure 2 This is a schematic diagram illustrating the data packet transmission process between a terminal device and a base station during cell handover in an LTE system.

[0138] Figure 3 and Figure 4 These are schematic diagrams illustrating two application scenarios of embodiments of this application;

[0139] Figure 5 This is a schematic diagram of the UDC technology involved in the embodiments of this application;

[0140] Figure 6 This is a schematic diagram illustrating the composition of the data packet count value;

[0141] Figure 7 A flowchart illustrating the first communication method provided in this application embodiment;

[0142] Figure 8 This is a schematic diagram of the terminal device retransmitting a portion of the compressed data packets in an embodiment of this application;

[0143] Figure 9 This is a schematic diagram illustrating the compression of data packets by the terminal device in an embodiment of this application;

[0144] Figure 10 A flowchart illustrating the second communication method provided in this application embodiment;

[0145] Figure 11 A flowchart illustrating the third communication method provided in the embodiments of this application;

[0146] Figure 12 A flowchart illustrating the fourth communication method provided in this application embodiment;

[0147] Figure 13 A schematic block diagram of a communication device provided in an embodiment of this application;

[0148] Figure 14 A schematic block diagram of a terminal device provided in an embodiment of this application;

[0149] Figure 15 This is a schematic block diagram of a network device provided in an embodiment of this application. Detailed Implementation

[0150] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the embodiments of this application will be further described in detail below with reference to the accompanying drawings.

[0151] In this embodiment, the terminal device is a device with wireless transceiver capabilities, which can 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, etc.) built into the aforementioned devices. The terminal device is used to connect people, objects, machines, etc., and can be widely used in various scenarios, including but not limited to the following: cellular communication, device-to-device (D2D) communication, vehicle-to-everything (V2X) communication, machine-to-machine / machine-type communications (M2M / MTC) communication, Internet of Things (IoT), virtual reality (VR), augmented reality (AR), industrial control, self-driving, remote medical care, smart grid, smart furniture, smart office, smart wearables, smart transportation, smart city, drones, robots, and other scenarios. The terminal equipment may sometimes be referred to as user equipment (UE), terminal, access station, UE station, remote station, wireless communication equipment, or user device, etc.

[0152] The network devices in this application embodiment include, for example, access network devices and / or core network devices. The access network devices are devices with wireless transceiver capabilities, used for communication with the terminal devices. The access network devices include, but are not limited to, base transceiver stations (BTS), Node Bs, evolved Node Bs (eNodeB / eNB, or gNodeB / gNB), transmission reception points (TRPs), base stations evolved from the 3rd Generation Partnership Project (3GPP), access nodes in Wireless Fidelity (WiFi) systems, wireless relay nodes, and wireless backhaul nodes. The base stations can be macro base stations, micro base stations, pico base stations, small cells, relay stations, etc. Multiple base stations can support networks using the same access technology mentioned above, or they can support networks using different access technologies mentioned above. A base station can contain one or more co-located or non-co-located transmission and reception points. Network devices can also be radio controllers, centralized units (CUs), and / or distributed units (DUs) in cloud radio access network (CRAN) scenarios. Network devices can also be servers, wearable devices, or vehicle-mounted devices. For example, network devices in vehicle-to-everything (V2X) technology can be roadside units (RSUs). The following description of access network devices uses base stations as an example. Multiple network devices in the communication system can be base stations of the same type or different types. Base stations can communicate with terminal devices or through relay stations. Terminal devices can communicate with multiple base stations in different access technologies. The core network devices are used to implement functions such as mobility management, data processing, session management, policy and billing. The names of devices implementing core network functions can differ in systems using different access technologies; this application does not limit this. Taking a 5G system as an example, the core network equipment includes: access and mobility management function (AMF), session management function (SMF), or user plane function (UPF), etc.

[0153] In this application embodiment, the communication device used to implement the network device function can be a network device or a device capable of supporting the network device to implement the function, such as a circuit system. This device can be installed within the network device. In the technical solutions provided in this application embodiment, the example of a network device being used to implement the network device function is used to describe the technical solutions provided in this application embodiment.

[0154] In this application embodiment, the number of nouns, unless otherwise specified, refers to "singular nouns or plural nouns," that is, "one or more." "At least one" means one or more, and "more than one" means two or more. "And / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can mean: A exists alone, A and B exist simultaneously, or B exists alone, where A and B can be singular or plural. The character " / " generally indicates that the related objects before and after are in an "or" relationship. For example, A / B means: A or B. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, at least one of a, b, or c means: a, b, c, a and b, a and c, b and c, or a and b and c, where a, b, and c can be single or multiple.

[0155] In this application's embodiments, ordinal numbers such as "first" and "second" are used to distinguish multiple objects, and are not used to limit the size, content, order, timing, application scenario, priority, or importance of the multiple objects. For example, the first cache and the second cache can be the same cache or different caches, and such names do not indicate differences in the content, priority, application scenario, or importance of the two caches.

[0156] Please refer to Figure 1 This refers to the process of data packet compression and decompression in LTE systems. Figure 1 In the diagram, PDCP and RLC in the top two lines refer to the PDCP and RLC layers at the sending end. Taking a buffer size of two data packets as an example, each dashed box represents the content included in the buffer. Additionally, boxes marked with a " / " within the dashed boxes indicate pre-defined information included in the buffer. Each data packet is compressed based on the content currently included in the buffer. Figure 1 The PDCP and RLC in the bottom two lines refer to the PDCP layer and RLC layer at the receiving end. In AM mode, because the RLC layer supports data retransmission, although the sender transmits compressed data packets in order, the compressed data packets received by the receiver may be out of order. In the LTE system, the receiver's RLC layer sorts the received compressed data packets and then delivers the sorted compressed data packets to the PDCP layer. For example... Figure 1 In the protocol stack, the receiving end's RLC layer receives compressed data packets 1, 2, 3, and 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 these four compressed data packets and then delivers them to the PDCP layer in the normal order. The PDCP layer receives these four compressed data packets and decompresses them sequentially through the UDC protocol stack. Afterward, the receiving end receives compressed data packet 5, and the receiving end's RLC layer delivers compressed data packet 5 to the PDCP layer, which then decompresses it. Subsequently, the receiving end receives compressed data packets 6, 7, and 8. However, the receiving end receives these three compressed data packets in the order of 8, 7, and 6. After receiving compressed data packet 6, the receiving end's RLC layer sorts these three compressed data packets and then delivers the sorted three compressed data packets to the PDCP layer. The PDCP layer receives these three compressed data packets and decompresses them sequentially through the UDC protocol stack. For example, the PDCP layer decompresses compressed data packet 1 based on preset information included in the compression buffer; it decompresses compressed data packet 2 based on the preset information included in the compression buffer and the information obtained after decompressing compressed data packet 1; it decompresses compressed data packet 3 based on the information obtained after decompressing compressed data packet 1 and the information obtained after decompressing compressed data packet 2 (because the buffer can hold the contents of two data packets, it is assumed that the preset information has been evicted from the buffer), and so on. Figure 1 The sequence number of the data packets appearing in the data (or the sequence number of the compressed data packets) is the sequence number (SN) of the PDCP layer, or the sequence number can also be understood as the count value of the PDCP layer of the data packet.

[0157] Normally, the PDCP layer at the receiving end will receive compressed data packets in sequence, ensuring that the buffer at the receiving end and the buffer at the sending end are aligned, thus achieving sequential decompression.

[0158] In LTE systems, when a terminal device undergoes cell handover, the radio link control (RLC) layer of the base station is rebuilt. If the RLC layer already has out-of-order compressed data packets, or if there are still data packets that have not yet been received, the RLC layer will no longer wait to receive the unreceived compressed data packets, but will instead deliver the already received compressed data packets to the PDCP layer. (See reference...) Figure 2When the base station (receiving end) RLC layer undergoes reconstruction, it has already received compressed data packets 3, 4, 5, and 7, but has not yet received compressed data packets 1, 2, and 6. Therefore, the RLC layer will deliver compressed data packets 3, 4, 5, and 7 to the PDCP layer. Compressed data packet 0 has already been received and successfully decompressed by the RLC, and data packet 0 obtained from decompressing compressed data packet 1 has been delivered to the PDCP layer. After receiving compressed data packets 3, 4, 5, and 7, the PDCP layer will decompress them. When decompressing compressed data packet 3, the PDCP layer needs to update its buffer based on the decompression result of compressed data packet 2 to ensure successful decompression of compressed data packet 3. However, since the PDCP layer has not received compressed data packet 2, it will fail to decompress compressed data packet 3. Similarly, it will also fail to decompress compressed data packets 4, 5, and 7, and will discard them. In addition, after receiving compressed data packets, the base station's RLC layer sends a hybrid automatic repeat request (HARQ) acknowledgment (ACK) message to the terminal device. For compressed data packets that have been received, the base station's RLC layer sends an affirmative acknowledgment (ACK) to the terminal device. For example, if the RLC layer has not yet received compressed data packet 1 when reconstruction occurs, then the RLC layer will not send an ACK for compressed data packet 1 to the terminal device.

[0159] After cell handover, the terminal device (sender) can retransmit compressed data packets to the base station. For example, the terminal device can retransmit sequentially starting from the first compressed data packet for which no ACK has been received. For instance, if the terminal device receives ACKs for compressed data packets 3, 4, 5, and 7, but not ACKs for compressed data packets 1, 2, and 6, it will retransmit compressed data packets 1 through 7. During cell handover, the terminal device rebuilds the PDCP layer and resets its corresponding UDC buffer and UDC protocol stack. The terminal device then recompresses the data packets based on the reset buffer. The compressed data packets 1 through 7 previously sent to the base station were obtained by compressing the corresponding data packets based on the buffer before the reset. Now, the terminal device recompresses these data packets again based on the reset buffer to obtain compressed data packets 1 through 7, and then sends these compressed data packets to the base station. It is evident that the terminal device needs to perform compression twice for the same data packet. Multiple compression processes obviously increase the processing time of the terminal device, especially when there are many data packets, which will significantly reduce the processing efficiency of the terminal device.

[0160] UDC technology currently only exists in LTE systems and has not yet been introduced into new radio (NR) systems. Whether UDC technology can be used in NR systems is still undecided.

[0161] This application provides a communication method that enables the application of buffer-based data compression technology (such as UDC technology) in NR systems. Furthermore, in this application embodiment, the terminal device does not reset the first buffer when rebuilding the PDCP layer. Therefore, if the terminal device needs to retransmit data packets, it can retransmit the previously obtained compressed data packets without recompressing them. This reduces the number of data packet compressions, decreases the processing time of the terminal device, and improves processing efficiency. Moreover, reducing the workload of the terminal device also reduces its power consumption. If the terminal device acts as a data receiver, it can also process data normally without resetting the buffer, further reducing its workload and power consumption.

[0162] The technical solutions provided in this application can be applied to LTE systems, such as ordinary LTE systems or vehicle-to-everything (V2X) systems, LTE-V systems, etc., or to NR systems, such as ordinary NR systems or vehicle-to-everything (V2X) systems, NR-V systems, etc., or to other similar communication systems or next-generation communication systems.

[0163] Please see Figure 3 This is one application scenario of an embodiment of this application. Figure 3 This includes a network device and a terminal device. The network device operates, for example, in an evolved UMTS terrestrial radio access (E-UTRA) system or in an NR system. For instance, the terminal device accesses this network device both before and after cell handover.

[0164] Please refer to Figure 4 This is another application scenario of the embodiments of this application. Figure 4 This includes two network devices and one terminal device. For example, network device 1 is the network device that the terminal device accesses before cell handover, and network device 2 is the network device that the terminal device accesses after cell handover. Network device 1 or network device 2 may operate in, for example, an evolved UMTS terrestrial radio access (E-UTRA) system or an NR system, and the systems in which network device 1 and network device 2 operate may be the same or different.

[0165] Figure 3or Figure 4 The network equipment in this context includes, for example, a base station. The network equipment corresponds to different devices in different systems; for instance, in a 4G system it might correspond to an eNB, while in a 5G system it might correspond to a 5G network device, such as a gNB. In a 5G system, the network equipment can also be a hybrid network of LTE and NR network equipment, forming a mixed radio-dual connectivity (MR-DC) with the terminal equipment. Of course, the technical solutions provided in this application can also be applied to future mobile communication systems. Figure 3 or Figure 4 The network equipment in this context can also correspond to the network equipment in future mobile communication systems. Figure 3 and Figure 4 Taking base stations as an example of network equipment, as mentioned above, network equipment can also include devices such as RSUs.

[0166] Consider a practical application scenario of an embodiment of this application. When a user holds a terminal device and wants to make a VoLTE / Voice over New Radio (VoNR) call or access the internet (such as starting a live stream or playing games online), they need to access the network. Upon initial network access, the terminal device typically needs to report to the base station whether it supports data compression. When it is determined that the terminal device supports data compression, the base station can decide whether to configure relevant data compression parameters for the terminal device (e.g., configure the corresponding bearer to support UDC function and its activation status) based on the user's initiated service. When the terminal device is configured by the base station to perform data compression, such as UDC, the terminal device can use UDC during uplink transmission, such as initiating a VoLTE / VoNR call, starting a live stream, or playing a real-time game. In this case, the terminal device can use the method provided in this embodiment to perform UDC, which can reduce or even avoid packet loss caused by uplink data compression and save power consumption from repeated compression. Similarly, if downlink data compression is performed, the method provided in this embodiment can also be used to reduce or even avoid packet loss caused by downlink data compression.

[0167] Furthermore, the embodiments of this application are not limited to communication between network devices and terminal devices; they can also be communication between network devices or between terminal devices, etc.

[0168] The technical solutions provided by the embodiments of this application are described below with reference to the accompanying drawings. It should be noted that in the accompanying drawings corresponding to the various embodiments of this application, all steps indicated by dashed lines are optional. Furthermore, all embodiments of this application use an NR system as an example.

[0169] Before introducing the embodiments provided in this application, the UDC technology involved in the various embodiments of this application will be introduced first.

[0170] UDC (User Data Compression) involves the terminal device (as the sender) compressing data packets, and the network device (as the receiver) decompressing them. Both compression and decompression rely on the sender and receiver maintaining the same buffer state. The buffer state refers to the content (or information) included in the buffer. When compressing data packets, the sender compresses them based on the current buffer state. After successful compression, the sender updates the buffer by adding the original information of the current compressed data packet from the backend. For the first data packet, the buffer may not contain information from previous packets. In this case, the sender can compress based on preset information, such as a pre-made dictionary. See [reference needed]. Figure 5 The buffer contains "abc", where "abc" is, for example, a pre-made dictionary. When the sender needs to compress the data packet "def", it can compress it based on "abc", resulting in compressed data packet 1. The sender can then add "def" from the back end of the buffer. Next, if the sender needs to compress the data packet "ghijkl", it can compress it based on "abcdef" in the buffer. In other words, compression is always based on the entire contents of the buffer. Compressing the data packet "ghijkl" results in compressed data packet 2, which the sender can then add from the back end of the buffer. Due to the limited storage space of the buffer, following the first-in-first-out (FIFO) principle, "abcd" will be evicted from the buffer. Therefore, if the sender needs to compress other data packets, it will compress them based on "efghijkl" included in the buffer. For the receiving end, after receiving compressed data packet 1, it can decompress compressed data packet 1 based on the pre-defined dictionary "abc" in the buffer, obtaining data packet "def", and then put data packet "def" into the buffer from the back end. After receiving compressed data packet 2, the receiving end can decompress compressed data packet 2 based on the information "abcdef" in the buffer, obtaining data packet "ghijkl", and then put data packet "ghijkl" into the buffer from the back end, thus evicting "abcd" from the buffer. It is evident that the buffer state of the receiving end and the buffer state of the sending end are always consistent, thus ensuring that the receiving end can correctly decompress the data.

[0171] In various embodiments of this application, the sequence number of the uncompressed data packet (hereinafter also referred to as a data packet) and the corresponding compressed data packet can be the same. For example, compressing the first data packet yields a first compressed data packet, and the sequence number of the first compressed data packet is the same as the sequence number of the first data packet; compressing the second data packet yields a second compressed 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 various embodiments of this application can be applied to the transmission of UM / AM data radio bearer (DRB), or to the transmission of signaling radio bearer (SRB), or to the transmission of a QoS flow within the DRB.

[0172] In air interface transmission, each data packet has a corresponding number at the PDCP layer. This PDCP layer number consists of two parts: the sequence number (SN) and the hyperframe number (HFN). These two parts together constitute the data packet's number, or its count value. (See reference...) Figure 6 This is a schematic diagram illustrating the composition of the data packet count. In the embodiments of this application, the data packet sequence number can refer to either the data packet's serial number or its count value.

[0173] This application provides a first communication method, please refer to [link to relevant documentation]. Figure 7 Here is a flowchart of the method. In the following description, this method will be applied to... Figure 3 The network architecture shown is an example. The terminal devices described below are, for example,... Figure 3 The terminal devices in the network architecture shown, the first network device described below, are, for example, Figure 3 Network devices in the network architecture shown.

[0174] S701, The terminal device sends capability information to the first network device, and the first network device receives the capability information from the terminal device accordingly.

[0175] For example, the terminal device may send this capability information to the first network device during random access, or it may send it after successful random access. This capability information may indicate the terminal device's capabilities, such as indicating that the terminal device supports UDC. Alternatively, it may indicate support for continuing to use the first buffer, meaning the terminal device supports the function of continuing to use the first buffer (also known as buffer continue), or it may indicate that it does not support continuing to use the first buffer. Buffer continue can be understood as not resetting the buffer corresponding to the data compression / decompression function when rebuilding the PDCP layer. Therefore, this capability information may also indicate support for not resetting the first buffer when rebuilding the PDCP layer, or it may indicate that not resetting the first buffer is not supported when rebuilding the PDCP layer. Optionally, in addition to this, the capability information may also indicate other capabilities of the terminal device, such as the number of antennas supported by the terminal device, without limitation. The first buffer is maintained by the terminal device and used to compress data packets; in other words, the terminal device can compress data packets based on the first buffer.

[0176] Based on this capability information, the first network device can determine whether the terminal device supports continuing to use the first cache. If the terminal device supports continuing to use the first cache, the first network device can instruct the terminal device to continue using the first cache. If the terminal device does not support continuing to use the first cache, the first network device may not instruct the terminal device to continue using the first cache or may instruct the terminal device to reset the first cache. Alternatively, the terminal device may not send capability information, and the first network device can determine whether to instruct the terminal device to continue using the first cache based on other factors, or whether the terminal device continues to use the first cache can be specified by the protocol. Therefore, S701 is an optional step.

[0177] S702. The terminal device sends M compressed data packets to the first network device, and correspondingly, the first network device receives K compressed data packets from the terminal device. M is a positive integer, and K is a positive integer less than or equal to M. The K compressed data packets can be some or all of the M compressed data packets, or in other words, the K compressed data packets are a subset of the M compressed data packets.

[0178] The reason the first network device receives K compressed data packets instead of M is to account for packet loss. For example, MK compressed data packets might be lost during transmission and not correctly received by the first network device. The sequence numbers of the K compressed data packets may be consecutive or non-consecutive. Optionally, the sequence numbers of the K compressed data packets may not be consecutive with the sequence numbers of the data packets successfully decompressed by the first network device. For example, if the M compressed data packets are compressed data packets 1 to 7, and the K compressed data packets are compressed data packets 3, 4, 5, and 7, then the sequence numbers of the K compressed data packets are not consecutive. Furthermore, if the compressed data packet with the largest sequence number successfully decompressed by the first network device is compressed data packet 0, then the sequence numbers of the K compressed data packets will also not be consecutive with the sequence numbers of the last data packet successfully decompressed and submitted to the upper layer by the first network device. For example, if M compressed data packets are compressed data packets 1 to 7, and K compressed data packets are compressed data packets 3, 4, 5, and 6, then the sequence numbers of the K compressed data packets are consecutive. The compressed data packet with the largest sequence number that the first network device has successfully decompressed is compressed data packet 0. Therefore, the sequence numbers of the K compressed data packets are not consecutive with the sequence numbers of the data packets that the first network device has successfully decompressed.

[0179] The M compressed data packets are obtained by the terminal device compressing M data packets based on a first buffer, and there is a one-to-one correspondence between the compressed data packets and the data packets. The first buffer is the buffer used by the terminal device to compress data packets. For example, the terminal device may use UDC technology to compress data packets based on the first buffer. The first buffer may correspond to a first radio bearer, which may include all or part of the radio bearer of the terminal device, such as a DRB or SRB. Alternatively, the first buffer may correspond to one or more QoS flows in a DRB.

[0180] For example, before sending M compressed data packets, the terminal device has not yet sent the compressed data packets to the first network device. Therefore, before compressing the M compressed data packets, the terminal device's first buffer may include a pre-made dictionary; that is, the first buffer is filled with a pre-made dictionary. The terminal device compresses data packet 1 from the M data packets based on this pre-made dictionary, obtaining compressed data packet 1. Next, the terminal device updates the first buffer based on the content of data packet 1, and then compresses data packet 2 from the M data packets based on the updated first buffer, obtaining compressed data packet 2, and so on, until M compressed data packets are obtained. An example of this process can also be found in [reference needed]. Figure 5 .

[0181] The first network device can send feedback information of K compressed data packets to the terminal device to indicate that the first network device has received K compressed data packets. For example, the first network device's RLC layer can send an ACK for each compressed data packet it receives to the terminal device. The first network device can send a total of K ACKs to the terminal device, with each K ACK corresponding to a compressed data packet. After receiving K ACKs, the terminal device can know that the first network device has received K compressed data packets.

[0182] Optionally, the PDCP layer of the first network device can also send a status report to the terminal device. This status report can indicate the compressed data packets received by the first network device. In this embodiment, the status report can indicate K compressed data packets. After receiving the status report, the terminal device can know that the first network device has received K compressed data packets. For example, the status report can be implemented using a bitmap, which includes M bits, with each of the M bits corresponding to one of the M compressed data packets. If the first network device receives a compressed data packet, the corresponding bit is set to "1"; if the first network device does not receive a compressed data packet, the corresponding bit is set to "0". This allows the terminal device to quickly determine which compressed data packets the first network device has received. Alternatively, the status report can include the sequence number of the compressed data packets received by the first network device, and / or the sequence number of the compressed data packets not received by the first network device. This also allows the terminal device to determine which compressed data packets the first network device has received.

[0183] It is important to note that terminal devices can process compressed data packets appropriately before sending them. For example, the terminal device can perform integrity protection and encryption on the compressed data packets (e.g., at the PDCP layer), and then deliver the processed compressed data packets to the lower layers of the terminal device (e.g., RLC layer, Media Access Control (MAC) layer, or physical layer), which will then send the processed compressed data packets. Whether the terminal device sends M compressed data packets, or, as discussed later, N compressed data packets, a similar approach can be used, which will not be elaborated further.

[0184] S703, the first network device sends a handover command to the terminal device, and the terminal device receives the handover command from the first network device accordingly.

[0185] For example, the handover command includes first indication information, which may indicate the reconstruction of the PDCP layer or the handover of the cell. Optionally, the handover command may also include second indication information, which may indicate continued use of the first cache, or may indicate that the first cache should not be reset during PDCP reconstruction. In this case, if the handover command includes the second indication information, the terminal device may continue to use the first cache during PDCP layer reconstruction; however, if the handover command does not include the second indication information, the terminal device will not continue to use the first cache during PDCP layer reconstruction, for example, the terminal device will reset the first cache during PDCP layer reconstruction. Alternatively, in this case, the second indication information indicates whether the first cache should be reset during PDCP reconstruction. Or, in this case, the value of the second indication information indicates whether the first cache should be reset during PDCP reconstruction.

[0186] Alternatively, the second indication information may not be included in the handover command. The first network device can send the second indication information to the terminal device through other messages. In this case, the first network device can send the second indication information to the terminal device before S703, or after S703, or the first network device can send both 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, it can continue to use the first buffer when rebuilding the PDCP layer. If the terminal device does not receive the second indication information, it will not continue to use the first buffer when rebuilding the PDCP layer; for example, the terminal device can reset the first buffer when rebuilding the PDCP layer.

[0187] When the first network device sends the second indication information, it also supports continuing to use the second cache. The second cache corresponds to the first cache and is maintained by the first network device. For example, the first network device can decompress compressed data packets (or data packets compressed based on the first cache) according to the second cache. When the first network device does not send the second indication information, it may or may not support continuing to use the second cache. Regardless of whether the first network device supports continuing to use the second cache, since it did not send the second indication information, it will not continue to use the second cache when rebuilding the PDCP layer; instead, it will reset the second cache to maintain consistency with the behavior of the terminal device.

[0188] Alternatively, if the protocol specifies that the first buffer should continue to be used, or if the protocol specifies that the first buffer should not be reset when rebuilding the PDCP layer, then the first network device may not send the second indication information. In this case, the network device can determine, according to the protocol, to continue using the second buffer when rebuilding the PDCP layer, and the terminal device can also determine, according to the protocol, to continue using the first buffer when rebuilding the PDCP layer.

[0189] In addition to cell handover, terminal equipment may rebuild the PDCP layer in other situations, so S703 is an optional step.

[0190] S704: The terminal device rebuilds the PDCP layer without resetting the first cache.

[0191] The terminal device can rebuild the PDCP layer during cell handover. Alternatively, the terminal device can also rebuild the PDCP layer when triggered by events other than cell handover, so S703 is an optional step.

[0192] If the terminal device receives the second instruction information, or if the protocol stipulates continued use of the first cache, the terminal device may not reset the first cache when rebuilding the PDCP layer. However, if the terminal device does not receive the second instruction information, and the protocol does not stipulate continued use of the first cache, the terminal device may reset the first cache when rebuilding the PDCP layer. Resetting the first cache may include, for example, clearing the contents of the first cache and adding a pre-made dictionary to the cleared first cache. In various embodiments of this application, the contents of the pre-made dictionary may be related to services, and the pre-made dictionary may be the same or different depending on the services performed by the device. Alternatively, the contents of the pre-made dictionary may also be related to other factors; specific details are not limited and will not be elaborated further below. This application embodiment takes the example of the terminal device not resetting the first cache when rebuilding the PDCP layer.

[0193] S705, the first network device rebuilds the PDCP layer without resetting the second cache.

[0194] If the terminal device performs a cell handover, the first network device will also rebuild the PDCP layer. In this embodiment, the terminal device accesses the first network device both before and after the cell handover; for example, the terminal device switches 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 cache, it will not reset the second cache when rebuilding the PDCP layer. However, if the first network device determines not to continue using the second cache, it can reset the second cache when rebuilding the PDCP layer. Resetting the second cache includes, for example, clearing the contents of the second cache and adding a pre-made dictionary to the cleared second cache. For both the first network device and the terminal device, since it is necessary to maintain a consistent cache state, the pre-made dictionary used to reset the first cache and the pre-made dictionary used to reset the second cache can be the same. This embodiment takes the example of the first network device not resetting the second cache when rebuilding the PDCP layer.

[0195] S704 may occur before S705, or after S705, or simultaneously with S705.

[0196] S706. The terminal device sends N compressed data packets to the first network device, and correspondingly, 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 less than or equal to M.

[0197] After a terminal device completes cell handover or PDCP layer reconstruction but has not switched network devices, it can retransmit N compressed data packets to the first network device. The terminal device sends N compressed data packets in ascending order of their sequence numbers, starting from the first compressed data packet that was not 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) could be the first compressed data packet that was not successfully received by the first network device (or the compressed data packet with the smallest sequence number among the data packets that were not successfully received by the first network device). For example, if M compressed data packets are compressed data packets 1 to 7, K compressed data packets are compressed data packets 3, 4, 5, and 7, and N compressed data packets are compressed data packets 1 to 7, then the first compressed data packet among the N compressed data packets is compressed data packet 1, which is the first compressed data packet that was not successfully received by the first network device.

[0198] In the example above, N = M, meaning the terminal device effectively retransmits M compressed data packets, which increases the success rate of the first network device receiving the compressed data packets. Optionally, if the first network device sends a status report to the terminal device indicating the compressed data packets it has received, the terminal device doesn't need to retransmit those packets; it only needs to send the compressed data packets the first network device hasn't received. In this case, the N compressed data packets don't necessarily include those already received. For example, if the M compressed data packets are compressed data packets 1 through 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 indicates K compressed data packets, then the terminal device sends N compressed data packets, such as compressed data packets 1, 2, and 6. For compressed data packets 3, 4, 5, and 7, the terminal device doesn't need to retransmit them, reducing the amount of data retransmitted and saving transmission overhead.

[0199] For reference Figure 8 The terminal device's PDCP layer sends M compressed data packets, for example, compressed data packets 1 to 7. The first network device's PDCP layer receives compressed data packets 3, 4, 5, and 7, but not compressed data packets 1, 2, and 6. Before sending the M compressed data packets, the terminal device's PDCP layer also sends compressed data packet 0 to the first network device. The first network device's PDCP layer receives compressed data packet 0 and successfully decompresses it, obtaining data packet 0. The first network device's PDCP layer then delivers data packet 0 to its upper layer, such as the Service Data Adaptation Protocol (SDAP) layer. The first network device's PDCP layer sends a status report to the terminal device's PDCP layer, indicating that the first network device has received compressed data packets 3, 4, 5, and 7. For example, this status report is implemented using a bitmap, which may include 7 bits, such as 1011100. The bits, from least significant to most significant, correspond to compressed data packets 1 through 7. If the first network device receives compressed data packets 3, 4, 5, and 7, the corresponding bits for these compressed data packets are set to "1". If the first network device does not receive compressed data packets 1, 2, and 6, the corresponding bits for these compressed data packets are set to "0". After receiving this status report, the terminal device's PDCP layer retransmits compressed data packets 1, 2, and 6 to the first network device, instead of retransmitting compressed data packets 3, 4, 5, and 7, thus saving uplink transmission resources.

[0200] Can be referenced again Figure 9 This refers to the process by which the terminal device compresses data packets 1 through 7. Figure 9The first row, from 1 to 7, represents 7 PDCP service data units (SDUs), which are 7 data packets. In other words, 1 to 7 in the first row represent 7 data packets to be compressed. The second row represents the compressed data packets 1 to 7 obtained by the terminal device compressing data packets 1 to 7 based on the first buffer. The third row represents the encrypted data packets 1 to 7 obtained by encrypting the compressed data packets 1 to 7 in the second row according to the first encryption method. The terminal device can send these 7 encrypted data packets to the first network device. This process can be regarded as the terminal device sending M compressed data packets to the first network device, for example, M=7. These 7 encrypted data packets are obtained by encrypting the M compressed data packets according to the first encryption method. The first encryption method is the encryption method corresponding to the first cell that the terminal device accesses before cell handover. The fourth line represents the encrypted data packets 1 through 7 obtained by encrypting the compressed data packets 1 through 7 in the second line using the second encryption method. The terminal device can send these 7 encrypted data packets to the first network device. This process can be regarded as the terminal device sending N compressed data packets to the first network device, for example, N=7. These 7 encrypted data packets are obtained by encrypting the N compressed data packets using the second encryption method. The second encryption method is the encryption method corresponding to the second cell that the terminal device accesses after cell handover. Figure 9 As can be seen, the terminal device only performs the compression process for these data packets once. If it is necessary to retransmit these compressed data packets, it is only necessary to encrypt the already obtained compressed data packets according to the encryption method corresponding to the cell handover. There is no need to re-compress the data packets, which reduces the compression process of the terminal device and improves the processing efficiency of the terminal device accordingly.

[0201] For the first network device, after receiving K compressed data packets, if it does not send a status report to the terminal device, it can decompress the K compressed data packets. Since the sequence numbers of the K compressed data packets are not consecutive with the sequence numbers of the data packets successfully decompressed by the first network device, the first network device may fail to decompress the K compressed data packets. Therefore, the first network device can discard the K undecompressed compressed data packets. The terminal device will then send N compressed data packets to the first network device. Since the terminal device did not receive a 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 that the first network device failed to receive. Furthermore, the sequence numbers of the N data packets are consecutive; for example, the M compressed data packets are compressed data packets 1 to 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 to 7. Thus, even if the first network device discards the K compressed data packets, since the terminal device will send N compressed data packets again, and these N compressed data packets will include the K compressed data packets, the first network device can still obtain the K compressed data packets. Continuing the example above, since the first network device has obtained compressed data packets 1 to 7, and the first network device has already correctly decompressed compressed data packet 0, the state of the second buffer is determined based on data packet 0. Therefore, the first network device can correctly decompress compressed data packets 1 to 7 based on the unreset second buffer.

[0202] Alternatively, after receiving K compressed data packets, the first network device may not decompress them if it does not send a status report to the terminal device, but instead waits for N compressed data packets from the terminal device. The PDCP layer may have deduplication functionality. For example, if the first network device has already received compressed data packet 3 and has not discarded it, then if compressed data packet 3 is included in the N compressed data packets, the first network device will discard compressed data packet 3 after receiving it from the N compressed data packets, and continue storing the previously received compressed data packet 3. For example, if M compressed data packets are compressed data packets 1 to 7, K compressed data packets are compressed data packets 3, 4, 5, and 7, and N compressed data packets are compressed data packets 1 to 7, then the first network device will discard compressed data packets 3, 4, 5, and 7 from the N received compressed data packets. However, since the second buffer was not reset, the compressed data packets 3, 4, 5, and 7 stored by the first network device are the same as the compressed data packets 3, 4, 5, and 7 discarded by the first network device. Therefore, based on the unreset second buffer, the first network device can still correctly decompress the K compressed data packets 3, 4, 5, and 7, as well as the compressed data packets 1, 2, and 6 out of the N compressed data packets. In this way, the packet loss rate of the first network device can be reduced.

[0203] If 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 the K compressed data packets. If the first network device attempts to decompress the K compressed data packets but fails and discards them, and the terminal device stops sending the K compressed data packets, the first network device will not receive the K compressed data packets and may also affect its ability to decompress other compressed data packets. Therefore, if the first network device sends a status report to the terminal device after receiving K compressed data packets, it can choose not to decompress the K compressed data packets but instead wait for the N compressed data packets from the terminal device. Since the terminal device will not send data packets with the same sequence number repeatedly, the first network device does not need to use deduplication. For example, M compressed data packets are compressed data packets 1 to 7, K compressed data packets are compressed data packets 3, 4, 5, and 7, and N compressed data packets are compressed data packets 1, 2, and 6. The first network device, based on the unreset second buffer, is able to correctly decompress the K compressed data packets 3, 4, 5, and 7, as well as the N compressed data packets 1, 2, and 6.

[0204] S707, The first network device decompresses N compressed data packets based on the second buffer, or the first network device decompresses N compressed data packets and K compressed data packets based on the second buffer.

[0205] For example, if N compressed data packets include K compressed data packets, then it can be understood that the first network device decompresses the N compressed data packets based on the second buffer. For example, if M compressed data packets are compressed data packets 1 to 7, K compressed data packets are compressed data packets 3, 4, 5, and 7, and N compressed data packets are compressed data packets 1 to 7, then the first network device decompresses compressed data packets 1 to 7 based on the second buffer.

[0206] For example, if N compressed data packets include K compressed data packets, then it can 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 instance, if M compressed data packets are compressed data packets 1 to 7, K compressed data packets are compressed data packets 3, 4, 5, and 7, and N compressed data packets are compressed data packets 1, 2, and 6, then the first network device decompresses compressed data packets 1 to 7 based on the second buffer, and compressed data packets 1 to 7 are the union of the K compressed data packets and the N compressed data packets.

[0207] The technical solution provided in this application can reduce the number of compression operations performed by the terminal device, thereby improving its processing efficiency. If the first network device sends a status report to the terminal device, the amount of data sent by the terminal device can also be reduced, saving transmission overhead. Furthermore, since neither the first buffer of the terminal device nor the second buffer of the first network device is reset, even if the first network device does not send a status report to the terminal device, it can still obtain M compressed data packets regardless of whether it decompresses the K compressed data packets after receiving them, thus reducing packet loss.

[0208] The preceding sections described the scenario where neither the terminal device nor the first network device resets the cache. However, if the terminal device receives a second indication message instructing it not to continue using the first cache, or if the protocol specifies that the first cache should not be used, the terminal device can reset the first cache when rebuilding the PDCP layer. The first network device will also reset the second cache in this case. The following is a brief description of how the terminal device and the first network device handle this situation.

[0209] For example, continue to refer to Figure 2 When the PDCP layer of the first network device undergoes reconstruction, it has already received compressed data packets 3, 4, 5, and 7, but has not yet received compressed data packets 1, 2, and 6. Compressed data packet 0 is a compressed data packet that the PDCP layer has already received and successfully decompressed; the PDCP layer decompressed compressed data packet 0 to obtain data packet 0. After receiving compressed data packets 3, 4, 5, and 7, the PDCP reconstruction indication can trigger the decompression of these compressed data packets. If the PDCP layer fails to decompress compressed data packets 3, 4, 5, and 7, it will discard them. Alternatively, the PDCP reconstruction indication can trigger the PDCP layer to discard out-of-order compressed data packets (in a special case, if the data packets from the sender are uncompressed, these data packets 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, but directly discards them. The scheme of directly discarding out-of-order compressed data packets can reduce the number of decompression operations at the receiving end, improve processing efficiency, save energy, and avoid wasting resources on invalid decompression processing. Furthermore, after receiving compressed data packets, the RLC layer of the first network device sends ACK information to the terminal device. For already received compressed data packets, the RLC layer of the first network device sends an ACK to the terminal device. Subsequently, if the first network device sends a feedback report from the PDCP layer to the terminal device, the feedback report can indicate both data packets that the first network device has not received and data packets that the first network device has not successfully decompressed.

[0210] After a cell handover or PDCP layer reconstruction is complete, the terminal device can retransmit compressed data packets to the first network device. For example, the terminal device can retransmit sequentially starting from the first compressed data packet for which no ACK has been received. For instance, if the terminal device receives ACKs for compressed data packets 0, 3, 4, 5, and 7, but not ACKs for compressed data packets 1, 2, and 6, it will retransmit compressed data packets 1 through 7. During cell handover, the terminal device reconstructs the PDCP layer and resets the first buffer. The terminal device then recompresses the data packets based on the reset first buffer. Previously, compressed data packets 1 through 7 sent to the first network device were compressed using the first buffer before the reset. Now, the terminal device recompresses these data packets again using the reset first buffer to obtain compressed data packets 1 through 7, and then sends these compressed data packets to the first network device. Therefore, if the first buffer is not reused, the terminal device needs to perform compression twice for the same data packet.

[0211] In this embodiment, the first network device can instruct whether to continue using the first cache. The first network device can then instruct whether to continue using the first cache according to specific circumstances. For example, for terminal devices with lower capabilities, the first network device may not instruct to continue using the first cache, or may instruct not to continue using the first cache, to meet the capability requirements of the terminal device. Alternatively, for scenarios with high latency requirements, the first network device can instruct to continue using the first cache, requiring the terminal device to compress data only once, saving processing time and reducing data packet transmission latency. Therefore, the solution in this embodiment is quite flexible.

[0212] Figure 7 The illustrated embodiment applies to a co-location scenario, meaning that the terminal device accesses the same network device both before and after the handover. Next, we will introduce a second communication method provided in this application embodiment, which can be applied to... Figure 4 For the network architecture shown, please refer to [link / reference]. Figure 10 The flowchart below illustrates this method. In this method, the terminal device accesses a first network device before cell handover and a second network device after cell handover. This can be understood as the terminal device switching from a first cell provided by the first network device to a second cell provided by the second network device. The first and second network devices are different network devices. The terminal device described below is, for example, a... Figure 4 The terminal devices in the network architecture shown, the first network device described below, are, for example, Figure 4 Network device 1 in the network architecture shown, and the second network device described below, for example, are Figure 4 Network device 2 in the network architecture shown.

[0213] S1001, The terminal device sends capability information to the first network device, and the first network device receives the capability information from the terminal device accordingly.

[0214] For more information about S1001, please refer to [link / reference]. Figure 7 S701 in the illustrated embodiment.

[0215] S1002. The terminal device sends M compressed data packets to the first network device, and correspondingly, the first network device receives K compressed data packets from the terminal device. M is a positive integer, and K is a positive integer less than or equal to M.

[0216] In this embodiment, after receiving K compressed data packets, the first network device can send feedback information of K compressed data packets to the terminal device. For example, the RLC layer of the first network device can send K ACKs to the terminal device. Optionally, the first network device can also send a status report of K compressed data packets to the terminal device, which indicates the number of compressed data packets received by the first network device, such as indicating K compressed data packets. For more information, please refer to... Figure 7 S702 in the illustrated embodiment. Alternatively, the first network device may not send a status report of K compressed data packets to the terminal device.

[0217] For more information about S1002, please refer to [link / reference]. Figure 7 S702 in the illustrated embodiment.

[0218] S1003, the first network device sends a first message to the second network device, and correspondingly, the second network device receives the first message from the first network device. The first message can be used to inquire whether the terminal device should continue using the first buffer after handover, or it can be used to inquire whether the terminal device should not reset the first buffer when rebuilding the PDCP layer. The first buffer is a buffer maintained by the terminal device for compressing data packets. If the first buffer is reset, the content of the third buffer maintained by the second network device for decompression also needs to be in the reset state, for example, by filling the third buffer with a pre-made dictionary. The third buffer is maintained by the second network device, and the second network device can decompress data packets compressed based on the first buffer according to the third buffer.

[0219] The first, second, and third caches are all corresponding. The first cache is maintained by the terminal device, which compresses data packets based on the first cache. The second cache is maintained by the first network device. Before cell handover, the terminal device accesses the first network device, which can decompress compressed data packets (data packets compressed based on the first cache) from the terminal device based on the second cache. The third cache is maintained by the second network device. After cell handover, the terminal device accesses the second network device, which can decompress compressed data packets (data packets compressed based on the first cache) from the terminal device based on the third cache.

[0220] For example, if the first message is a handover request message, it can be understood as including query information, which can be used to inquire whether the second network device supports the terminal device continuing to use the first cache. Alternatively, the first message could be any other message.

[0221] S1004. The second network device sends a second message to the first network device, and correspondingly, the first network device receives the second message from the second network device. The second message may indicate that the supporting terminal device should continue to use the first cache, or indicate that the supporting terminal device should not continue to use the first cache. Alternatively, the second message may indicate that the supporting terminal device should not reset the first cache when rebuilding the PDCP layer, or indicate that the supporting terminal device should not reset the first cache when rebuilding the PDCP layer. For example, if the second message is a handover request acknowledge message, it can be understood that the handover request acknowledge message includes third indication information, which may indicate that the supporting terminal device should continue to use the first cache, or indicate that the supporting terminal device should not continue to use the first cache; or, the third indication information may indicate that the supporting terminal device should not reset the first cache when rebuilding the PDCP layer, or indicate that the supporting terminal device should not reset the first cache when rebuilding the PDCP layer. Alternatively, the second message may be other messages.

[0222] Alternatively, the first network device may not need to know whether the second network device supports the terminal device to continue using the first cache, or the first network device may also know whether the second network device supports the terminal device to continue using the first cache through other means. Therefore, S1003 and S1004 are optional steps.

[0223] S1005, the first network device sends a handover command to the terminal device, and correspondingly, the terminal device receives the handover command from the first network device. The handover command may instruct the terminal device to perform a cell handover or instruct the PDCP to be rebuilt. Optionally, the handover command may also include information instructing the terminal device to continue using the first buffer or not to continue using the first buffer.

[0224] For more information about S1005, please refer to [link / reference]. Figure 7 S703 in the illustrated embodiment.

[0225] S1006. The terminal device rebuilds the PDCP layer without resetting the first cache.

[0226] For more information about S1006, please refer to [link / reference]. Figure 7 S704 in the illustrated embodiment.

[0227] S1007. The first network device rebuilds the PDCP layer without resetting the second cache.

[0228] For more information about S1007, please refer to [link / reference]. Figure 7 S705 in the illustrated embodiment.

[0229] S1008. The first network device sends the contents of the second cache to the second network device, and correspondingly, the second network device receives the contents of the second cache from the first network device. For example, the first network device may send indication information to the second network device. To distinguish it from the aforementioned indication information, this indication information may also be called fourth indication information. The fourth indication information may indicate the contents of the second cache. For example, the fourth indication information may include the contents of the second cache (e.g., depending on the size of the second cache, common configurations for the size of the second cache are 2k, 4k, or 8k bytes), or the fourth indication information may not include the contents of the second cache, but the second network device can determine the contents of the second cache based on the fourth indication information.

[0230] If the second network device supports the terminal device continuing to use the first cache, the first network device may send a fourth indication message to the second network device; if the second network device does not support the terminal device continuing to use the first cache, the first network device may not need to send a fourth indication message to the second network device.

[0231] Alternatively, S1008 and S1003 can be the same message, in which the first network device sends the contents of the second cache to the second network device, implicitly or explicitly asking the second network device whether the terminal device supports the continued use of the first cache.

[0232] S1009. The second network device updates the third cache based on the contents of the second cache.

[0233] The second network device can put the contents of the second cache into the third cache, or replace the original contents of the third cache with the contents of the second cache, so that the state of the third cache is consistent with the state of the second cache. This is also equivalent to making the state of the third cache before compressing a certain data packet consistent with the state of the first cache when decompressing the data packet.

[0234] S1010, the first network device sends K compressed data packets to the second network device, and correspondingly, the second network device receives K compressed data packets from the first network device.

[0235] In this embodiment, since the terminal device has performed a cell handover, the first network device does not need to decompress the K compressed data packets. Instead, it can forward or send the K compressed data packets to the second network device through an inter-network device interface (such as port Xn), where the second network device processes the K compressed data packets. Alternatively, the first network device may not send the K compressed data packets to the second network device; that is, the first network device only forwards the successfully decompressed data packets to the second network device, for example, according to... Figure 7 As can be seen from the illustrated embodiment, if the terminal device sends N consecutive compressed data packets starting from the first compressed data packet for which no ACK has been received, then the N compressed data packets will include K compressed data packets. In this case, even if the first network device does not send the K compressed data packets to the second network device, the second network device can still receive the K compressed data packets from the terminal device. Therefore, S1110 is an optional step.

[0236] If the first network device sends K compressed data packets to the second network device, then optionally, after receiving the K compressed data packets, the second network device can send a status report of K compressed data packets to the terminal device. This status report indicates the number of compressed data packets received by the second network device, for example, indicating K compressed data packets. Alternatively, the second network device may not send this status report to the terminal device. That is, in this embodiment, the first network device and / or the second network device can send a status report of K compressed data packets to the terminal device. For the terminal device, it may receive a status report of K compressed data packets from the first network device, or it may receive a status report of K compressed data packets from the second network device, or it may receive a status report of K compressed data packets from both the first and second network devices. Alternatively, in this embodiment, the first and second network devices may not send a status report of K compressed data packets to the terminal device, in which case the terminal device will not receive a status report of K compressed data packets.

[0237] In addition to the K compressed data packets, the first network device may have received other compressed data packets from the terminal device. If the first network device has successfully decompressed these compressed data packets, it can also send the successfully decompressed data packets to the second network device.

[0238] S1011, The terminal device sends N compressed data packets to the second network device, and correspondingly, 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 less than or equal to M.

[0239] After a successful cell handover, the terminal device can continue sending data packets to the second network device. Therefore, for each retransmission of N compressed data packets, the terminal device will retransmit them to the second network device. For more information on S1011, please refer to [link to relevant documentation]. Figure 7 S706 in the illustrated embodiment.

[0240] The preceding text described the scenario where the terminal device and the first network device do not reset the cache. However, if the terminal device receives a second indication message indicating that the first cache should no longer be used, or if the protocol stipulates that the first cache should no longer be used, the terminal device can reset the first cache upon rebuilding the PDCP layer. The first network device will also reset the second cache upon rebuilding the PDCP layer. The handling methods for this scenario by the terminal device and the first network device are described below.

[0241] For example, when the PDCP layer of the first network device undergoes reconstruction, it has already received compressed data packets 3, 4, 5, and 7, but has not yet received compressed data packets 1, 2, and 6. After the PDCP layer receives compressed data packets 3, 4, 5, and 7, the PDCP reconstruction instruction can trigger the decompression of these compressed data packets. If the PDCP layer fails to decompress compressed data packets 3, 4, 5, and 7, it will discard them. Alternatively, the PDCP reconstruction instruction can trigger the PDCP layer to discard out-of-order compressed data packets (in a special case, if the data packets from the sender are uncompressed, these data packets do not need to be discarded even if they are out of order). That is, compressed data packets 3, 4, 5, and 7 are not decompressed, but directly discarded. The scheme of directly discarding out-of-order compressed data packets can reduce the number of decompression operations, improve processing efficiency, save energy, and avoid wasting resources on ineffective decompression processing. The first network device only needs to send the correctly decompressed data packets or the out-of-order compressed data packets that have not been dropped to the second network device; it does not need to send decompressed or undecompressed compressed data packets to the second network device. Furthermore, after receiving the compressed data packets, the RLC layer of the first network device will send an ACK message to the terminal device. For received compressed data packets, for example, the RLC layer of the first network device will send an ACK message to the terminal device.

[0242] After a cell handover or PDCP layer reconstruction is complete, the terminal device can retransmit compressed data packets to the second network device. For example, the terminal device can retransmit sequentially starting from the first compressed data packet for which no ACK has been received. For instance, if the terminal device receives ACKs for compressed data packets 0, 3, 4, 5, and 7, but not ACKs for compressed data packets 1, 2, and 6, it will retransmit compressed data packets 1 through 7. During cell handover, the terminal device reconstructs the PDCP layer and resets the first buffer. The terminal device then recompresses the data packets based on the reset first buffer. Previously, compressed data packets 1 through 7 sent to the second network device were compressed using the first buffer before the reset. Now, the terminal device recompresses these data packets again using the reset first buffer to obtain compressed data packets 1 through 7, and then sends these compressed data packets to the second network device. Therefore, if the first buffer is not reused, the terminal device needs to perform compression twice for the same data packet.

[0243] S1012, The second network device decompresses N compressed data packets based on the third cache, or the second network device decompresses N compressed data packets and K compressed data packets based on the third cache.

[0244] For example, if N compressed data packets include K compressed data packets, or if the second network device did not receive K compressed data packets from the first network device, or if the second network device received K compressed data packets from the first network device but the N compressed data packets include K compressed data packets, then it can be understood that the second network device decompresses the N compressed data packets based on the third buffer. For example, if M compressed data packets are compressed data packets 1 to 7, K compressed data packets are compressed data packets 3, 4, 5, and 7, and N compressed data packets are compressed data packets 1 to 7, then the second network device decompresses compressed data packets 1 to 7 based on the third buffer.

[0245] For example, if N compressed data packets do not include K compressed data packets, such as when a second network device receives K compressed data packets from a first network device, and the N compressed data packets do not include K compressed data packets, then it can be understood that the second network device decompresses the N compressed data packets and the K compressed data packets based on a third buffer. For example, if M compressed data packets are compressed data packets 1 to 7, K compressed data packets are compressed data packets 3, 4, 5, and 7, and N compressed data packets are compressed data packets 1, 2, and 6, then the second network device decompresses compressed data packets 1 to 7 based on the third buffer, and compressed data packets 1 to 7 are the union of the K compressed data packets and the N compressed data packets.

[0246] The technical solution provided by the embodiments of this application can reduce the number of compression operations of the terminal device and improve the processing efficiency of the terminal device. If the first network device and / or the second network device send a status report to the terminal device, the amount of data sent by the terminal device can also be reduced, saving transmission overhead. Moreover, since neither the first buffer of the terminal device nor the second buffer of the first network device is reset, the third buffer of the second network device can also be set according to the second buffer. Therefore, even if neither the first network device nor the second network device sends a status report to the terminal device, the second network device can still obtain M compressed data packets regardless of whether it decompresses the K compressed data packets after receiving them, or regardless of whether it receives the K compressed data packets. This reduces packet loss.

[0247] Figure 7 The illustrated embodiments and Figure 10 The embodiments shown all describe the compression process of uplink data packets, using, for example, UDC technology. However, this application also provides a compression process for downlink data packets, which will be described below.

[0248] This application provides a third communication method; please refer to [link / reference]. Figure 11 The flowchart below shows the method, which involves the compression process of downlink data packets. In the following description, this method will be applied to... Figure 3 The network architecture shown is an example. The terminal devices described below are, for example,... Figure 3 The terminal devices in the network architecture shown, the first network device described below, are, for example, Figure 3 Network devices in the network architecture shown.

[0249] S1101, the terminal device sends capability information to the first network device, and correspondingly, the first network device receives capability information from the terminal device. This capability information may indicate support for continuing to use the third buffer during PDCP reconstruction, or indicate that continued use of the third buffer is not supported during PDCP reconstruction; alternatively, this capability information may indicate support for not resetting the third buffer during PDCP layer reconstruction, or indicate that not resetting the third buffer during PDCP layer reconstruction is not supported. The third buffer is maintained by the terminal device and is used for decompressing data packets. In other words, the terminal device can decompress data packets based on the third buffer; for example, the terminal device can use downlink compression technology to decompress received compressed data packets based on the third buffer.

[0250] Based on this capability information, the first network device can determine whether the terminal device supports continuing to use the third cache. If the terminal device supports continuing to use the third cache, the first network device can choose whether to instruct the terminal device to continue using the third cache during a handover. If the terminal device does not support continuing to use the third cache, the first network device will not instruct the terminal device to continue using the third cache. Alternatively, the terminal device may not send capability information, and the first network device can determine whether to instruct the terminal device to continue using the third cache based on other factors. Furthermore, whether the terminal device continues to use the third cache can be specified through a protocol; therefore, step S1101 is optional.

[0251] For more information about S1101, please refer to [link / reference]. Figure 7 S701 in the illustrated embodiment.

[0252] S1102. The first network device sends M compressed data packets to the terminal device, and correspondingly, 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 can be some or all of the M compressed data packets, or in other words, 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 compressing the M data packets based on a first buffer (or, in this embodiment, the first buffer can also be called a second buffer). The first buffer is maintained by the first network device and is used by the first network device to compress data packets. For example, the first network device can use downlink compression technology to compress data packets based on the first buffer.

[0253] It is important to note that the first network device can process the compressed data packets appropriately before sending them. For example, the first network device can perform integrity protection and encryption processing on the compressed data packets (e.g., processing at the PDCP layer), and then deliver the processed compressed data packets to the lower layer of the first network device (e.g., RLC layer, MAC layer, or physical layer), which will then send the processed compressed data packets. If the first network device sends M compressed data packets, and the first network device (or, the second network device) mentioned later sends N compressed data packets, a similar approach can be used, which will not be elaborated further.

[0254] For more information about S1102, please refer to [link / reference]. Figure 7 In the illustrated embodiment, the roles of "terminal device" and "first network device" in S701 can be interchanged when referenced.

[0255] S1103. The first network device sends a handover command to the terminal device, and correspondingly, the terminal device receives the handover command from the first network device. This handover command may instruct the terminal device to perform cell handover or PDCP layer reconstruction. Optionally, the handover command may also instruct the terminal device to continue using the third buffer when reconstructing PDCP, or instruct the terminal device not to reset the third buffer when reconstructing PDCP.

[0256] For more information about S1103, please refer to [link / reference]. Figure 7 In the embodiment shown, S703 can be referenced by replacing the "first cache" maintained by the terminal device with the "third cache" and replacing the "second cache" maintained by the first network device with the "first cache".

[0257] S1104. The terminal device rebuilds the PDCP layer without resetting the third cache.

[0258] For more information about S1104, please refer to [link / reference]. Figure 7 In the illustrated embodiment, S704 can be referenced by replacing the "first cache" maintained by the terminal device in S704 with the "third cache".

[0259] S1105, The first network device rebuilds the PDCP layer without resetting the first cache.

[0260] For more information about S1105, please refer to [link / reference]. Figure 7 In the illustrated embodiment, S705 can be referenced by replacing "second cache" maintained by the first network device with "first cache".

[0261] S1106. The first network device sends N compressed data packets to the terminal device, and correspondingly, the terminal device receives 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 less than or equal to M. The first network device may send the N compressed data packets in ascending order of their sequence numbers, starting from the first compressed data packet that the terminal device has not yet confirmed as successfully received.

[0262] For more information about S1106, please refer to [link / reference]. Figure 7 In the illustrated embodiment, when referenced, the roles of "terminal device" and "first network device" in S706 can be interchanged, as can the roles of "first cache" and "third cache".

[0263] S1107. The terminal device decompresses N compressed data packets based on the third cache, or the terminal device decompresses N compressed data packets and K compressed data packets based on the third cache.

[0264] For example, if N compressed data packets include K compressed data packets, then it can be understood that the terminal device decompresses the N compressed data packets based on the third buffer. For example, if M compressed data packets are compressed data packets 1 to 7, K compressed data packets are compressed data packets 3, 4, 5, and 7, and N compressed data packets are compressed data packets 1 to 7, then the terminal device decompresses compressed data packets 1 to 7 based on the third buffer.

[0265] For example, if N compressed data packets include K compressed data packets, then it can be understood that the terminal device decompresses the N compressed data packets and the K compressed data packets based on the third buffer. For instance, if M compressed data packets are compressed data packets 1 to 7, K compressed data packets are compressed data packets 3, 4, 5, and 7, and N compressed data packets are compressed data packets 1, 2, and 6, then the terminal device decompresses compressed data packets 1 to 7 based on the third buffer, and compressed data packets 1 to 7 are the union of the K compressed data packets and the N compressed data packets.

[0266] The technical solution provided in this application can reduce the number of compression operations performed by the first network device, thereby improving its processing efficiency. If the terminal device sends a status report to the first network device, the amount of data sent by the first network device can also be reduced, saving transmission overhead. Furthermore, since neither the third buffer of the terminal device nor the first buffer of the first network device is reset, even if the terminal device does not send a status report to the first network device, it can still obtain M compressed data packets regardless of whether it decompresses the K compressed data packets after receiving them, thus reducing packet loss.

[0267] If the terminal device receives a second indication message indicating that the third cache should not be used further, or if the protocol stipulates that the third cache should not be used further, the terminal device can reset the third cache. The first network device will also reset its first cache. In this case, the processing methods for the terminal device and the first network device can be referenced as follows. Figure 7 The embodiments shown are described in the description and can be used as a reference. Figure 7 In the illustrated embodiment, the roles of "terminal device" and "first network device" are interchanged.

[0268] In this embodiment, the first network device can instruct whether to continue using the third cache. The first network device can then instruct accordingly based on specific circumstances. For example, for terminal devices with lower capabilities, the first network device may not instruct continued use of the third cache, or may instruct against continued use, to meet the capability requirements of the terminal device. Alternatively, for scenarios with high latency requirements, the first network device can instruct continued use of the third cache, requiring only one compression operation, saving processing time and reducing data packet transmission latency. Therefore, the solution in this embodiment is quite flexible.

[0269] Figure 11 The illustrated embodiment applies to a co-location scenario, meaning that the terminal device accesses the same network device both before and after the handover. Next, we will introduce the fourth communication method provided in this application embodiment, which can be applied to... Figure 4 For the network architecture shown, please refer to [link / reference]. Figure 12 The flowchart below illustrates this method, which still involves downlink compression. In this method, the terminal device connects to a first network device before cell handover and to a second network device after cell handover. The first and second network devices are different network devices. The terminal device described below is, for example, a... Figure 4 The terminal devices in the network architecture shown, the first network device described below, are, for example, Figure 4 Network device 1 in the network architecture shown, and the second network device described below, for example, are Figure 4 Network device 2 in the network architecture shown.

[0270] S1201, The terminal device sends capability information to the first network device, and the first network device receives the capability information from the terminal device accordingly.

[0271] For more information about S1201, please refer to [link / reference]. Figure 7 S701 in the illustrated embodiment.

[0272] S1202. The first network device sends M compressed data packets to the terminal device, and correspondingly, 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 can be some or all of the M compressed data packets, or in other words, 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 compressing the M data packets based on a first buffer. The first buffer is maintained by the first network device and is used by the first network device to compress data packets. For example, the first network device can use downlink compression technology to compress data packets based on the first buffer.

[0273] For more information about S1202, please refer to [link / reference]. Figure 7 In the illustrated embodiment, the roles of "terminal device" and "first network device" in S701 can be interchanged when referenced.

[0274] S1203, the first network device sends a first message to the second network device, and correspondingly, the second network device receives the first message from the first network device. The first message can be used to inquire whether the terminal device supports continuing to use the third buffer, or whether the terminal device supports not resetting the third buffer when rebuilding the PDCP layer. The third buffer is a buffer maintained by the terminal device for decompressing data packets. If the third buffer is reset, the content of the third buffer maintained by the terminal device for decompression will be the state after the reset; for example, the third buffer will be filled with a pre-made dictionary. Additionally, the second network device maintains a second buffer, which is used by the second network device to compress data packets; for example, the second network device can compress data packets based on the second buffer.

[0275] The first, second, and third caches are all corresponding. The first cache is maintained by the first network device. Before cell handover, the terminal device accesses the first network device, and the first network device compresses data packets based on the first cache. The second cache is maintained by the second network device. After cell handover, the terminal device accesses the second network device, and the second network device can compress data packets based on the second cache. The third cache is maintained by the terminal device. The terminal device can decompress compressed data packets from the first and / or second network devices based on the third cache. In other words, the terminal device can decompress data packets compressed based on the first cache according to the third cache, and / or decompress data packets compressed based on the second cache according to the third cache.

[0276] For example, if the first message is a handover request message, it can be understood as including query information. This query information can be used to inquire whether the terminal device is supported to continue using the third cache, or whether the terminal device is supported to not reset the third cache when rebuilding the PDCP layer. Alternatively, the first message could be any other message.

[0277] S1204. The second network device sends a second message to the first network device, and correspondingly, the first network device receives the second message from the second network device. The second message may indicate that the terminal device is supported in continuing to use the third cache, or indicate that the terminal device is not supported in continuing to use the third cache. For example, if the second message is a handover request response message, it can be understood that the handover request response message includes third indication information, which may indicate that the continued use of the third cache is supported, or indicate that the continued use of the third cache is not supported. Alternatively, the second message may be other messages.

[0278] Alternatively, the first network device may not need to know whether the second network device supports the terminal device to continue using the third cache, or the first network device may also know whether the second network device supports the terminal device to continue using the third cache through other means. Therefore, S1203 and S1204 are optional steps.

[0279] S1205. The first network device sends a handover command to the terminal device, and the terminal device receives the handover command from the first network device. This handover command instructs the terminal device to perform cell handover.

[0280] For more information about S1205, please refer to [link / reference]. Figure 7 In the embodiment shown, S703 can be referenced by replacing the "first cache" maintained by the terminal device with the "third cache" and replacing the "second cache" maintained by the first network device with the "first cache".

[0281] S1206. The terminal device rebuilds the PDCP layer without resetting the third cache.

[0282] For more information about S1206, please refer to [link / reference]. Figure 7 In the illustrated embodiment, S704 can be referenced by replacing the "first cache" maintained by the terminal device in S704 with the "third cache".

[0283] S1207. The first network device rebuilds the PDCP layer without resetting the first cache.

[0284] For more information about S1207, please refer to [link / reference]. Figure 7 In the illustrated embodiment, S705 can be referenced by replacing "second cache" maintained by the first network device with "first cache".

[0285] S1208. The first network device sends the contents of the first cache to the second network device, and correspondingly, the second network device receives the contents of the first cache from the first network device. For example, the first network device may send indication information to the second network device. To distinguish it from the aforementioned indication information, this indication information may also be called fourth indication information. The fourth indication information may indicate the contents of the first cache. For example, the fourth indication information may include the contents of the first cache (e.g., depending on the size of the first cache, the common configuration for the size of the contents of the first cache is 2k, 4k, or 8k bytes), or the fourth indication information may not include the contents of the first cache, but the second network device can determine the contents of the first cache based on the fourth indication information.

[0286] Alternatively, S1208 and S1203 may be the same message, in which the first network device sends the contents of the second cache to the second network device, and may implicitly or explicitly ask the second network device whether it supports the terminal device to continue using the third cache.

[0287] If the second network device supports the terminal device continuing to use the third cache, the first network device may send a fourth indication message to the second network device. However, if the second network device does not support the terminal device continuing to use the third cache, the first network device does not need to send a fourth indication message to the second network device. Therefore, S1208 is an optional step.

[0288] S1209. The second network device updates the second cache according to the contents of the first cache.

[0289] The second network device can replace the original content in the second cache with the content in the first cache, so that the state of the second cache is consistent with the state of the first cache. This is also equivalent to making the state of the second cache before compressing a certain data packet consistent with the state of the third cache when decompressing the data packet.

[0290] S1210, the first network device forwards data packets from the core network device to the second network device, and correspondingly, the second network device receives data packets from the first network device. For example, these data packets include compressed data packets (SDUs) by the first network device, and / or include uncompressed data packets (SDUs).

[0291] Before a cell handover occurs, the data packets received by the terminal device from the first network device originate from the core network device (e.g., the UPF user plane function). When the terminal device hands over from the first network device to the second network device, subsequent data packets from the terminal device will be transmitted from the core network device to the second network device. However, during the cell handover, for data packets sent by the first network device but not successfully received by the terminal device, the first network device will forward the packets to the second network device, starting with the packet with the smallest sequence number that did not receive an ACK from the terminal device. That is, the first network device forwards packets that did not receive an ACK from the terminal device to the second network device. These forwarded data packets may include compressed data packets from the first network device, and / or uncompressed data packets from the first network device.

[0292] If the first network device does not receive any data packets from the core network that need to be sent to the terminal device, or if the first network device has already sent all the data packets from the core network device that need to be sent to the terminal device to the terminal device, and has also received ACKs from the terminal device, then S1210 does not need to be executed. Therefore, S1210 is an optional step.

[0293] S1211, The second network device sends N compressed data packets to the terminal device, and correspondingly, 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 less than or equal to M. The second network device may send the N compressed data packets in ascending order of their sequence numbers, starting from the first unreceived compressed data packet received by the terminal device.

[0294] After a successful cell handover, the second network device continues to send data packets to the terminal device. Since the terminal device had unreceived compressed data packets before the handover, the second network device sends N compressed data packets to the terminal device. For example, after updating its second buffer, the second network device can compress the N data packets to obtain N compressed data packets, which are then sent to the terminal device. Some or all of the N data packets may have been sent from the first network device to the second network device, or the N data packets may have been obtained by the second network device from the core network equipment. For more information on S1211, please refer to [link to relevant documentation]. Figure 10 In the embodiment shown, S1011 can be referenced, and the roles of "terminal device" and "second network device" can be interchanged. In addition, when referring to the embodiment, if a status report is involved, the status report in this application embodiment can indicate K compressed data packets. The status report can be sent by the terminal device to the first network device, and the first network device can send the status report to the second network device. Alternatively, the status report can also be sent by the terminal device to the second network device.

[0295] S1212, The terminal device decompresses N compressed data packets based on the third cache, or the terminal device decompresses N compressed data packets and K compressed data packets based on the third cache.

[0296] For more information about S1212, please refer to [link / reference]. Figure 11 S1107 in the illustrated embodiment.

[0297] The preceding text described the scenario where the terminal device and the first network device do not reset the cache. However, if the second instruction received by the terminal device instructs it not to continue using the third cache, or if the protocol stipulates that the terminal device should not continue using the third cache, then the terminal device can reset the third cache, and the first network device will also reset the first cache. In this case, the handling methods of the terminal device and the first network device are described below.

[0298] For example, when the PDCP layer of the terminal device is rebuilt, it has already received compressed data packets 3, 4, 5, and 7, but has not yet received compressed data packets 1, 2, and 6. After the PDCP layer receives compressed data packets 3, 4, 5, and 7, the PDCP rebuild instruction can trigger the decompression of these compressed data packets. If the PDCP layer fails to decompress compressed data packets 3, 4, 5, and 7, it will discard them. Alternatively, the PDCP rebuild instruction can trigger the PDCP layer to discard out-of-order compressed data packets (in a special case, if the data packets from the sender are uncompressed, these data packets do not need to be discarded even if they are out of order). That is, instead of decompressing compressed data packets 3, 4, 5, and 7, the PDCP layer directly discards them. The scheme of directly discarding out-of-order compressed data packets can reduce the number of decompression operations, improve processing efficiency, save energy, and avoid wasting resources on ineffective decompression processing. In addition, after receiving the compressed data packet, the RLC layer of the terminal device will send ACK information to the first network device. For the received compressed data packet, the RLC layer of the terminal device will send ACK to the first network device.

[0299] After the terminal device completes cell handover or PDCP layer reconstruction, the second network device can retransmit compressed data packets to the terminal device. For example, the second network device can retransmit sequentially starting from the first compressed data packet for which no ACK has been received. For instance, if the second network device receives ACKs for compressed data packets 0, 3, 4, 5, and 7, but not ACKs for compressed data packets 1, 2, and 6, it will retransmit compressed data packets 1 through 7. During cell handover, the second network device reconstructs the PDCP layer and resets the second buffer. The second network device then compresses the data packets according to the reset second buffer. Previously, compressed data packets 1 through 7 sent to the terminal device by the second network device were compressed using the second buffer before the reset. Now, the second network device recompresses data packets 1 through 7 again using the reset second buffer to obtain compressed data packets 1 through 7, and then sends these compressed data packets to the terminal device. Therefore, if the third buffer is not used, for the same data packet, the first network device needs to compress it, and the second network device needs to compress it again.

[0300] The technical solutions provided in this application can reduce the number of compression operations performed by network devices, thereby improving their processing efficiency. Furthermore, if the terminal device sends a status report to the network device, the amount of data sent by the network device can be reduced, saving transmission overhead.

[0301] Figure 13A schematic diagram of a communication device 1300 according to an embodiment of this application is provided. The communication device 1300 may be... Figure 7 The illustrated embodiments Figure 10 The illustrated embodiments Figure 11 The illustrated embodiments, or Figure 12 The terminal device described in any of the illustrated embodiments is used to implement the method executed by the terminal device in the above method embodiments. Alternatively, the communication device 1300 may also be... Figure 7 The illustrated embodiments Figure 10 The illustrated embodiments Figure 11 The illustrated embodiments, or Figure 12 The first network device described in any of the illustrated embodiments is used to implement the method corresponding to the first network device in the above method embodiments. Alternatively, the communication device 1300 may also be... Figure 7 The illustrated embodiments Figure 10 The illustrated embodiments Figure 11 The illustrated embodiments, or Figure 12 The second network device described in any of the embodiments shown is used to implement the method corresponding to the second network device in the above method embodiments. For specific functions, please refer to the descriptions in the above method embodiments.

[0302] The communication device 1300 includes one or more processors 1301. The processor 1301, also referred to as a processing unit, can implement certain control functions. The processor 1301 can be a general-purpose processor or a dedicated processor, etc. For example, it may include: a baseband processor, a central processing unit (CPU), an application processor, a modem processor, a graphics processor, an image signal processor, a digital signal processor, a video codec processor, a controller, a memory, and / or a neural network processor, etc. The baseband processor can be used to process communication protocols and communication data. The CPU can be used to control the communication device 1300, execute software programs, and / or process data. Different processors can be independent devices or integrated into one or more processors, for example, integrated on one or more application-specific integrated circuits (ASICs).

[0303] Optionally, the communication device 1300 includes one or more memories 1302 for storing instructions 1304, which can be executed on the processor to cause the communication device 1300 to perform the methods described in the above method embodiments. Optionally, the memories 1302 may also store data. The processor and memories can be provided separately or integrated together.

[0304] Optionally, the communication device 1300 may include instructions 1303 (sometimes referred to as code or program), which can be executed on the processor to cause the communication device 1300 to perform the methods described in the above embodiments. Data may be stored in the processor 1301.

[0305] Optionally, the communication device 1300 may also include a transceiver 1305 and an antenna 1306. The transceiver 1305 may be referred to as a transceiver unit, transceiver, transceiver circuit, transceiver, input / output interface, etc., and is used to realize the transmission and reception functions of the communication device 1300 through the antenna 1306.

[0306] Optionally, the communication device 1300 may further include one or more of the following components: a wireless communication module, an audio module, an external memory interface, 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, or a display screen, etc. It is understood that in some embodiments, the 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 implemented in hardware, software, or a combination of software and hardware.

[0307] The processor 1301 and transceiver 1305 described in this application embodiment can be implemented on integrated circuits (ICs), analog ICs, radio frequency identification (RFID) integrated circuits, mixed-signal ICs, application-specific integrated circuits (ASICs), printed circuit boards (PCBs), or electronic devices. The communication device described herein can be a standalone device (e.g., a standalone integrated circuit, a mobile phone, etc.) or a part of a larger device (e.g., a module embedded in other devices). For details, please refer to the foregoing descriptions of terminal devices and network devices; further details will not be repeated here.

[0308] This application provides a terminal device (referred to as UE for convenience) that can be used in the foregoing embodiments. The terminal device includes components for implementing... Figure 7 , Figure 10 , Figure 11 or Figure 12The corresponding means, units, and / or circuits of the terminal device functions described in any one or more of the accompanying drawings. For example, the terminal device includes a transceiver module for supporting the terminal device in implementing transceiver functions, and a processing module for supporting the terminal device in processing signals.

[0309] Figure 14 A schematic diagram of the structure of a terminal device provided in an embodiment of this application is given.

[0310] The terminal device 1400 is applicable to Figure 3 or Figure 4 In the architecture shown. For ease of explanation, Figure 14 Only the main components of the terminal device 1400 are shown. (For example...) Figure 14 As shown, the terminal device 1400 includes a processor, memory, control circuitry, antenna, and input / output devices. The processor is primarily used to process communication protocols and data, control the entire terminal device 1400, execute software programs, and process the data from those programs. The memory is mainly used to store software programs and data. The control circuitry is primarily used for converting baseband signals to radio frequency signals and processing radio frequency signals. The antenna is primarily used for transmitting and receiving radio frequency signals in the form of electromagnetic waves. Input / output devices, such as a touchscreen, display screen, microphone, and keyboard, are primarily used to receive user input data and output data to the user.

[0311] Taking a mobile phone as an example, when the terminal device 1400 is powered on, the processor can read the software program in the storage unit, interpret and execute the instructions of the software program, and process the data of the software program. When data needs to be transmitted wirelessly, the processor performs baseband processing on the data to be transmitted and outputs the baseband signal to the control circuit. The control circuit performs radio frequency processing on the baseband signal and transmits the radio frequency signal outward in the form of electromagnetic waves through the antenna. When data is sent 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.

[0312] Those skilled in the art will understand that, for ease of explanation, Figure 14 Only one memory and processor are shown. In some embodiments, the terminal device 1400 may include multiple processors and memories. Memory may also be referred to as storage medium or storage device, etc., and this embodiment of the invention does not limit this.

[0313] As an optional implementation, the processor may include a baseband processor and a central processing unit. The baseband processor is mainly used to process communication protocols and communication data, while the central processing unit is mainly used to control the entire terminal device 1400, execute software programs, and process the data of the software programs. Figure 14 The processor in the terminal device 1400 integrates the functions of a baseband processor and a central processing unit (CPU). Those skilled in the art will understand that the baseband processor and CPU can also be independent processors interconnected via technologies such as buses. The terminal device 1400 may include multiple baseband processors to adapt to different network standards, and multiple CPUs to enhance its processing capabilities. The various components of the terminal device 1400 can be connected via various buses. The baseband processor can also be described as a baseband processing circuit or a baseband processing chip. The CPU can also be described as a central processing circuit or a central processing chip. The function of processing communication protocols and communication data can be built into the processor or stored in the storage unit as a software program, with the processor executing the software program to implement the baseband processing function.

[0314] In one example, the antenna and control circuitry with transceiver functions can be considered as the transceiver unit 1410 of the terminal device 1400, and the processor with processing functions can be considered as the processing unit 1420 of the terminal device 1400. For example... Figure 14 As shown, the terminal device 1400 includes a transceiver unit 1410 and a processing unit 1420. The transceiver unit can also be referred to as a transceiver, transceiver device, or transceiver apparatus. Optionally, the device in the transceiver unit 1410 used to implement the receiving function can be considered as a receiving unit, and the device in the transceiver unit 1410 used to implement the transmitting function can be considered as a transmitting unit; that is, the transceiver unit 1410 includes a receiving unit and a transmitting unit. For example, the receiving unit can also be referred to as a receiver, receiver circuit, or receiving device, and the transmitting unit can be referred to as a transmitter, transmitter, or transmitting circuit.

[0315] This application also provides a network device that can be used in the foregoing embodiments. The network device includes components for implementing... Figure 7 , Figure 10 , Figure 11 or Figure 12 The means, units, and / or circuits of the embodiment shown in any one or more of the accompanying drawings, for example, the functions of a first network device. Alternatively, the network device includes components for implementing... Figure 7 , Figure 10 , Figure 11 or Figure 12The means, units, and / or circuits of, for example, the functions of a second network device as described in any one or more of the accompanying drawings. For example, the network device includes a transceiver module to support the network device in implementing transceiver functions, and a processing module to support the network device in processing signals.

[0316] Figure 15 A schematic diagram of the structure of a network device provided in an embodiment of this application is given. Figure 15 As shown, the network device can be used with 3 or Figure 4 In the illustrated architecture, the network device includes a baseband device 1501, a radio frequency (RF) device 1502, and an antenna 1503. In the uplink direction, the RF device 1502 receives information transmitted by the terminal device via the antenna 1503 and transmits the information to the baseband device 1501 for processing. In the downlink direction, the baseband device 1501 processes the information from the terminal device and transmits it to the RF device 1502. The RF device 1502 processes the information from the terminal device and then transmits it to the terminal device via the antenna 1503.

[0317] The baseband device 1501 includes one or more processing units 15011, a storage unit 15012, and an interface 15013. The processing unit 15011 supports the network device in performing the functions of the network device in the above method embodiments. The storage unit 15012 stores software programs and / or data. The interface 15013 interacts with the radio frequency device 1502, and includes interface circuitry for information input and output. In one implementation, the processing unit is an integrated circuit, such as one or more ASICs, or one or more DSPs, or one or more FPGAs, or a combination of these integrated circuit types. These integrated circuits can be integrated together to form a chip. The storage unit 15012 and the processing unit 15011 can reside on the same chip, i.e., an on-chip storage element. Alternatively, the storage unit 15012 can reside on a different chip than the processing unit 15011, i.e., an off-chip storage element. The storage unit 15012 can be a single memory or a collective term for multiple memories or storage elements.

[0318] Network devices can implement some or all of the steps in the above method embodiments through one or more processing unit schedulers. For example, implementing... Figure 7 , Figure 10 , Figure 11 or Figure 12 The embodiments shown in any one or more of the accompanying drawings illustrate the corresponding functions of the first network device and / or the second network device. The one or more processing units may support the same type of wireless access technology or different types of wireless access technologies.

[0319] Those skilled in the art will recognize that the units and steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0320] In the several embodiments provided in this application, it should be understood that the disclosed systems, apparatuses, and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of units is only a logical functional division. Units described as separate components may or may not be physically separated, and components shown as units may or may not be physical units, i.e., they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0321] If the aforementioned functions are implemented as software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, or a portion of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this application. The aforementioned computer-readable storage medium can be any available medium that a computer can access. For example, but not limited to: computer-readable media 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, portable hard disk, or other optical disc storage, magnetic disk storage media, or other magnetic storage devices, or any other medium capable of carrying or storing desired program code having the form of instructions or data structures and accessible by a computer. Additionally, by way of example but not limitation, many forms of RAM are available, such as static random access memory (SRAM), dynamic random access memory (DRAM), synchronous dynamic random access memory (SDRAM), double data rate synchronous dynamic random access memory (DDRSDRAM), enhanced synchronous dynamic random access memory (ESDRAM), synchronous link dynamic random access memory (SLDRAM), or direct rambus RAM (DR RAM).

[0322] The above description is merely a specific embodiment of this application, but the protection scope of the embodiments of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the embodiments of this application should be included within the protection scope of the embodiments of this application. Therefore, the protection scope of the embodiments of this application should be determined by the protection scope of the claims.

Claims

1. A communication method applied to a terminal device, characterized in that, Send M compressed data packets, wherein the M compressed data packets are obtained by compressing the M data packets based on the first buffer, and M is a positive integer; Rebuild the PDCP layer without resetting the first cache; Send N compressed data packets, where the N compressed data packets are part or all of the M compressed data packets, and N is a positive integer less than or equal to M.

2. The method according to claim 1, characterized in that, The data packet with the smallest sequence number among the N compressed data packets is the data packet with the smallest sequence number among the data packets that the network device failed to receive.

3. The method according to claim 1 or 2, characterized in that, The method further includes: Send capability information, which indicates support for continuing to use the first cache.

4. The method according to claim 1 or 2, characterized in that, Prior to reconstructing the PDCP layer, the method further includes: Receive a first indication message and a second indication message, wherein the first indication message is used to indicate the reconstruction of the PDCP layer, and the second indication message is used to indicate the continued use of the first cache.

5. The method according to claim 4, characterized in that, The first indication information and the second indication information are included in the switching command.

6. The method according to any one of claims 1, 2, and 5, characterized in that, Sending M compressed data packets includes: The M compressed data packets are protected for integrity and encrypted using the PDCP layer of the terminal device. The processed M compressed data packets are delivered to the underlying layer of the terminal device through the PDCP layer, wherein the underlying layer is the RLC layer, MAC layer or physical layer; The M compressed data packets are sent through the underlying layer.

7. The method according to claim 6, characterized in that, The process of performing integrity protection and encryption on the M compressed data packets through the PDCP layer of the terminal device includes: The M compressed data packets are associated with a first encryption method, and the N compressed data packets are associated with a second encryption method. The first encryption method is the encryption method corresponding to the first cell accessed by the terminal device before cell handover, and the second encryption method is the encryption method corresponding to the second cell accessed by the terminal device after cell handover.

8. The method according to claim 1 or 2, characterized in that, Sending M compressed data packets includes: sending the M compressed data packets to a first network device; Sending N compressed data packets includes sending the N compressed data packets to the first network device.

9. The method according to claim 1 or 2, characterized in that, Sending M compressed data packets includes: sending the M compressed data packets to a first network device, wherein the first network device is the network device that the terminal device accesses before cell handover; Sending N compressed data packets includes sending the N compressed data packets to a second network device, wherein the first network device is the network device that the terminal device accesses after cell handover.

10. The method according to claim 1 or 2, characterized in that, The M compressed data packets are obtained by compressing M data packets based on the first buffer, including: Each of the M data packets is compressed sequentially according to the first cache, wherein after each data packet is compressed, the first cache is updated, and the updated first cache is used to compress the next data packet.

11. A communication method applied to a first network device, characterized in that, include: K compressed data packets are received from the terminal device. The K compressed data packets are obtained by compressing the K data packets based on the first buffer, where K is a positive integer. The PDCP layer is rebuilt without resetting the second cache, which is used by the first network device to decompress data packets compressed based on the first cache.

12. The method according to claim 11, characterized in that, The method further includes: The K compressed data packets are sent to a second network device, which is the network device that the terminal device accesses after cell handover, and the first network device is the network device that the terminal device accesses before cell handover.

13. The method according to claim 11 or 12, characterized in that, The method further includes: The system sends an instruction to the second network device, the instruction being used to indicate the content of the second cache, the content of the second cache being used to update the third cache, the third cache being used by the second network device to decompress data packets compressed based on the first cache, the second network device being the network device accessed by the terminal device after cell handover, and the first network device being the network device accessed by the terminal device before cell handover.

14. The method according to claim 11 or 12, characterized in that, The method further includes: Send a first message to the second network device. The first message is used to inquire whether the terminal device is supported to continue using the first cache. The second network device is the network device that the terminal device accesses after cell handover, and the first network device is the network device that the terminal device accesses before cell handover. The first network device receives a second message from the second network device, the second message being used to indicate support for the terminal device to continue using the first cache.

15. The method according to claim 11, characterized in that, The method further includes: A status report is sent to the terminal device, the status report indicating that the first network device has received the K compressed data packets.

16. The method according to claim 15, characterized in that, The method further includes: The terminal device receives N compressed data packets, which are part or all of M compressed data packets, and K compressed data packets are part or all of the M compressed data packets. The M data packets have consecutive sequence numbers and 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.

17. The method according to claim 16, characterized in that, The data packet with the smallest sequence number among the N compressed data packets is the data packet with the smallest sequence number among the data packets that the first network device failed to receive.

18. The method according to any one of claims 11, 12, 15-17, characterized in that, The method further includes: The terminal device receives capability information, which is used to instruct the terminal device to support continued use of the first cache.

19. The method according to any one of claims 11, 12, 15-17, characterized in that, The method further includes: Send a first instruction message and a second instruction message to the terminal device. The first instruction message is used to instruct the reconstruction of the PDCP layer, and the second instruction message is used to instruct the continued use of the first cache.

20. The method according to claim 19, characterized in that, The first indication information and the second indication information are included in the switching command.

21. The method according to claim 16 or 17, characterized in that, The M compressed data packets are associated with a first encryption method, and the N compressed data packets are associated with a second encryption method. The first encryption method is the encryption method corresponding to the first cell accessed by the terminal device before cell handover, and the second encryption method is the encryption method corresponding to the second cell accessed by the terminal device after cell handover.

22. The method according to any one of claims 11, 12, 15-17, characterized in that, The K compressed data packets are obtained by compressing K data packets based on the first buffer, including: Each of the K data packets is compressed sequentially according to the first cache, wherein after each data packet is compressed, the first cache is updated, and the updated first cache is used to compress the next data packet.

23. A terminal device, characterized in that, include: One or more processors; One or more memory units; And one or more computer programs, wherein the one or more computer programs are stored in the one or more memories, the one or more computer programs including instructions that, when executed by one or more processors of the terminal device, cause the terminal device to perform the method as described in any one of claims 1 to 10.

24. A network device, characterized in that, include: One or more processors; One or more memory units; And one or more computer programs, wherein the one or more computer programs are stored in the one or more memories, the one or more computer programs including instructions that, when executed by one or more processors of the network device, cause the network device to perform the method as described in any one of claims 11 to 22.

25. A computer-readable storage medium, characterized in that, The computer-readable storage medium is used to store a computer program that, when run on a computer, causes the computer to perform the method as described in any one of claims 1 to 10, or causes the computer to perform the method as described in any one of claims 11 to 22.

26. A chip, characterized in that, It includes one or more processors and a communication interface, wherein the one or more processors are configured to read instructions to perform the method of any one of claims 1 to 10, or to perform the method of any one of claims 11 to 22.

27. A communication device, characterized in that, It includes at least one module for performing the method of any one of claims 1-10 or for performing the method of any one of claims 11-22.

28. A computer program product, characterized in that, The computer program product includes a computer program that, when run on a computer, causes the computer to perform the method as described in any one of claims 1 to 10, or causes the computer to perform the method as described in any one of claims 11 to 22.

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